How should we pasteurize donor breast milk?

Posted on 23 April 2024 by Keith Barrington

The standard method of pasteurization of donor breast milk, and I believe the only method approved by HMBANA (the human milk banking association of north america), is similar to what Louis Pasteur himself came up with a couple of centuries ago (in about 1865). I’m not sure why its called Holder pasteurization, it may be because the temperature is “held” at 62.5 degrees for 30 minutes, or maybe it’s named after someone. In any case, it is effective in killing most bacteria, not including spore-bearing forms (like Bacillus cereus), but, unfortunately, inactivates white cells, kills probiotic organisms and denatures many large molecules, especially proteins.

Some of the advantages of human milk are therefore impacted by Holder pasteurization (HP), and there are a few review articles available (including this one from the European MBA) which discuss the available pasteurization methods. Other means of pasteurization that have been evaluated, include ultraviolet treatment, high hydrostatic pressure, and most particularly High Temperature Short Time (HTST) which uses temperatures of about 72 degrees for 15 seconds. All the alternative methods seem to be equally good at inactivating bacteria, and many viruses, but the alternatives have much less negative impact on the other beneficial components of milk (Oligosaccharides are relatively unaffected by HP). The major current problem with changing over to alternatives are the new equipment that will be required, and the lack of good evidence that it actually makes a clinical difference.

A recent RCT from 2 NICUs in Madrid compared supplementing mothers milk with pasteurized donor milk that used one of 2 different pasteurization methods, HP and HTST. They enrolled 213 and analyzed results from 160 ELBW infants, with the primary outcome being the occurrence of CLABSI, or a positive blood culture in an infant who had a central line in place for more than 48 hours, and in whom the culture was drawn during catheter use or within 48 hours after.

The most striking result is the enormously high frequency of CLABSI in those units, in both groups, 42% with the HTST and 46% in the HP group. There was no statistical difference between groups, but the study was designed to have 150 babies per group, and powered for a 33% reduction in the outcome. They stopped adding patients after 160 were actually enrolled, which is never really explained, the confidence intervals for the relative risk of catheter related sepsis were 0.68-1.26 with HTST compared to HP, so a large potential benefit is consistent with this null result.

The definition of late-onset sepsis is quite rigorous, and required a positive blood culture, after 72 hours of life, with a central catheter in place (or removed <48 h) and at least 2 of a sequence of clinical signs, or in the case of CoNS also other lab results (CBC results or CrP raised). When expressed per 1000 catheter days, the incidence in the two groups was about 18/1000 catheter days.

As a comparison, among babies <1kg birth weight in the CNN, all LOS combined (which is any positive blood culture, not requiring any other criteria, either with or without a central catheter in place) was 28%. In a publication from the German Neonatal Network, they showed “only 45% of primary BSI were CVC related in the <1000 g birthweight group” in other words, only about half of LOS was catheter related. That percentage is going to vary a great deal, depending on how central catheters are used, and the GNN also showed also a large variation in use. Nevertheless, the infections reported by this new Spanish study are only a subgroup of all the LOS in their infants; again in comparison with the Canadian Network, among infants <33 weeks the incidence of CLABSI was about 7.5/1000 catheter days.

As far as I can tell, the Spanish study did not enrol particularly high-risk babies, some were eliminated because of a “risk of early death”, they seem to be a group with relatively standard risk profile.

I think that different ways to try and preserve the advantages of human milk, by using different pasteurization methods is really important. However, by themselves, such improvements will not be likely to have a huge impact on LOS rates, especially when only a small proportion of the milk received is the donor milk. Enteral colonization with pathogenic, mostly Gram negative, organisms is a known common occurrence prior to blood stream infection. This recent publication for example, Schwartz DJ, et al. Gut pathogen colonization precedes bloodstream infection in the neonatal intensive care unit. Sci Transl Med. 2023;15(694):eadg5562, showed that GI colonization with the same organisms was very common, and that the pathogens were more abundant, in babies who later developed LOS. The anti-infective properties of milk will have an impact on gut colonization, and it is likely that different pasteurization methods will have an impact on those benefits.

There are many other things we do that can affect the incidence of LOS, I note that in the Spanish trial the use of “anti-acid” medications was very common at 20 to 30%, there are no details, and they may have been given after the episodes of sepsis, but I think there is very little indication for the use of such medications, which clearly can increase gut colonization by reducing one of the important barriers.

I just hope this new study doesn’t discourage the on-going development of better ways to pasteurize donor human milk which preserve more of the advantages. I think we need more, adequately powered studies to, firstly, show impacts on the intestinal microbiome of different pasteurization methods, and, if possible, following that, the clinical benefits. But we must take into account the large number of other risk factors for LOS, and reinforce quality control. Stringent quality improvement methods can reduce LOS in the very preterm, and have to be a priority wherever ELBW infants are cared for.

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22 to 23 weeks gestation, what is so special?

Posted on 27 March 2024 by Keith Barrington

I was confused by this new article published in the Journal of Pediatrics. I really don’t understand what the point of it is, except to try and discourage intensive care for one particular group of high risk babies (Guillen U, et al. Community considerations for aggressive intensive care therapy for infants <24+0 weeks of gestation. J Pediatr. 2024:113948).

The article title immediately alerts to the slant of the argument, apparently active intensive care for the most immature infants is “aggressive”, the authors justify this word by noting that Helen Harrison used it. Speaking as someone who was publicly attacked by Helen Harrison after a presentation I gave, in which I had noted that the long term outcomes of preterm infants were largely positive, I don’t find that justification adequate!

The authors of the article make a number of points that it is difficult to argue with: that outcomes are variable and uncertain; that decisions should be individualized and parents should always be involved; and that we should advocate for long term support for survivors and their families.

My question is: what is so different about this subgroup of babies? Surely the same things can be said about high-risk diaphragmatic hernias, or babies with severe variants of hypoplastic left heart syndrome, or babies born at 28 weeks after rupture of membranes at 20 weeks and persistent anhydramnios. Indeed, for each of those 3 examples, survival may be lower, and long term complications just as uncertain, as the baby born at 22 weeks gestation.

Surely all high risk infants, whatever their gestational age, have outcomes that are uncertain and variable, require individualized decision-making with parental involvement, and deserve long term support as much as they deserve active intensive care.

There are some other concerns about this paper, it is stated, for example, “As the rates of BPD were high, and BPD correlates with NDI, the loss to follow up may under-estimate rates of NDI” I don’t understand the logic of that sentence, unless there is some unstated evidence that infants with BPD have lower follow up rates. In fact the reference just given in the article, which was written by the first author of this new opinion piece, shows the opposite; higher follow up rates are associated with lower rates of “NDI”.

In that systematic review, it was shown that loss to follow up, on average, over-estimates rates of NDI. Which I presume is because infants who are doing well are, in general, less likely to be brought back by their parents for neuro-developmental assessment.

The authors also talk about the high rate of acute morbidity among the most immature infants, and it is true that a very high proportion have acute morbidity, including extremely high rates of BPD. But, still needing oxygen at 36 weeks is a consequence of exposing fragile and extremely under-developed lungs to oxygen and positive pressure, and doesn’t necessarily have huge impacts on the baby’s future quality of life. 2 of the other 3 examples I gave of high risk babies also have a very high incidence of chronic respiratory problems, and extremely high proportions have acute morbidity.

I think it would have been much more useful to point out that survival and other outcomes among these babies are extremely variable, but that with a consistent approach, co-ordinated with our obstetric teams, good survival is possible, and we should all be striving to institute best practice. They could also have indicated where to find the best information about how to improve survival and outcomes of these babies.

The Tiny Baby Collaborative has been developed in an attempt to improve the outcomes of such infants, their website gives you access to several recent Webinars. One interesting aspect of which is that the approach to such infants differs in many important details from one successful centre to another, in terms of fluid management, ventilatory approach, etc. What is universal in such centres is a collaboration with obstetrics, consistent, protocol-driven, approaches, and a commitment to and belief that these babies are worth the effort. I don’t find it useful to define one category of babies that are not worth as much as others; it is not many years since people were saying exactly the same things about babies born at 24 weeks. With “aggressive” quality improvement initiatives, survival is now over 70% across Canada, it has become infrequent to not start intensive care for such infants, and huge numbers of families, including my own, have benefited from a refusal to suppose that we have arrived at a limit of viability, but rather to push the barriers and progressively improve our care processes.

Posted in Neonatal Research | 6 Comments

Oxygen is toxic in older kids too!

Posted on 22 February 2024 by Keith Barrington

A new large RCT from PICUs in the UK randomly compared 2 saturation target ranges, 88-92 and >94%. (Peters MJ, et al. Conservative versus liberal oxygenation targets in critically ill children (Oxy-PICU): a UK multicentre, open, parallel-group, randomised clinical trial. Lancet. 2024;403(10424):355-64). Children <16 years of age being ventilated with supplemental oxygen were randomized within 6 hours of admission. The intervention stopped when the child was extubated. Primary outcome was “the duration of organ support” up to 30 days after admission. This was “a rank-based endpoint with death either on or before day 30 as the worst outcome (a score equating to 31 days of organ support), with survivors assigned a score between 1 and 30 depending on the number of calendar days of organ support received. Organ support … included respiratory support… cardiovascular support… and renal support. Other components of organ support included analgesia or sedation, exchange transfusion, neurological support, and metabolic support”.

2040 patients were randomized and data included for 1872 of them (more about that in a moment), half of the children were <1 year of age.

Differences in outcomes were small, but there was a reduction in the adverse primary outcome,

The size of the effect is expressed in a way which I find difficult to understand, it is “a probabilistic index of 0·53 (95% CI 0·50–0·55; p=0·04 Wilcoxon rank-sum test) indicating a higher probability for a better outcome in the conservative oxygenation group”.

I found this graph made the results a little easier to comprehend, the cumulative proportion of infants in each group who required organ support in the first 30 days of hospitalisation, with the children who died scoring 31.

This relatively small advantage of lower SpO2 targets was achieved despite many infants being above the target range for significant periods of time. As in the preterm O2 studies, much of this is because they were in 21% oxygen, but some was due to periods of time in supplemental O2 with SpO2 above target.

These 3 panels, using the same colours as the figure above, show the proportions of time by SpO2 in the top panel, the proportions of time with each SpO2 reading while receiving more than 21% oxygen in the middle panel, and the proportion of ventilated time with each FiO2 in the bottom panel. This is the version from the supplemental materials, which includes data up to day 30, data from the first 7 days are in the main article and look very similar. It looks like the lower SpO2 target group were extubated about 3 hours earlier on average, and may have had a shorter duration of cardiovascular support.

Previous studies in newborn infants of differing saturation targets include the early life trials which were meta-analysed in the NeoProm collaboration, and led to an increase in saturation targets, as mortality was higher with SpO2 targets in the high 80’s compared to the low 90’s.

Studies in older preterm newborn infants include STOP-ROP, and the first BOOST trial. STOP-ROP was a large RCT, published in 2000, among about 600 preterm infants who had developed pre-threshold retinopathy, as then defined, and who had a median SpO2 of <94% in room air. Pre-threshold was any zone 1 RoP of stage 1 or 2 without plus, or zone 2 RoP of stage 2 with a limited region of plus disease, or stage 3 without plus. The infants were randomized to target SpO2 in the low 90’s or the high 90’s (89-94 vs 96-99%), the idea being that some animal models showed decreased progression of retinopathy, after it had first appeared, when saturations were maintained in a higher range. It was thought that maintaining retinal ateriolar vasoconstriction with mild hyperoxia could prevent neovascularization. There was no overall difference in ophthalmic outcomes between groups, on subgroup analysis there might have been an advantage of the high oxygen group in the eyes that did not have plus disease, but the most severely affected infants, with plus disease, had no difference between groups. The intervention continued for at least 2 weeks, and until the baby’s eyes had either reached “threshold” (and treatment indications) or had shown regression on 2 subsequent eye exams. Almost all the babies were out of the study before discharge, as they had satisfied eye end points. Babies were usually randomized at about 35 weeks PMA, and therefore most had a BPD diagnosis. All the pulmonary outcomes were worse in the group with higher SpO2 goals. There were more babies still hospitalised at 3 months corrected age, more babies on oxygen at 3 months, were more episodes of pneumonia and episodes of BPD exacerbations in the supplemental oxygen group. In contrast to the expectations of the investigators, babies with higher oxygen saturations did not grow any better, with identical weight gain between groups.

BOOST was a trial from Australia of supplemental oxygen among 360 preterm infants <30 weeks GA who had reached 32 weeks and still required oxygen. They were randomized to target SpO2 of 91-94% or 95-98% (using masked oximeters) and remained in their group until oxygen was stopped (including when at home). The hypothesis behind this trial was also that higher saturations would lead to better growth and development, which was a reasonable supposition, based on observational data that babies who had been maintained with higher saturations had better outcomes in those domains. The RCT, in contrast to the observational data, showed no advantage in growth or development. In order to maintain the higher saturation, the high SpO2 group stayed in oxygen much longer, and were more likely to go home in oxygen. They also had more respiratory related deaths (1 vs 6, p=NS), more treatment with steroids and/or with diuretics, and had more re-hospitalisations.

Which suggests that even small increments of inhaled oxygen concentrations can have pulmonary toxicity, and that the balance between ensuring adequate oxygen delivery while limiting oxygen-induced lung injury is a very narrow one. Maintaining tight oxygen saturation limits, and avoiding even mild hyperoxia seems to be important for ensuring the best clinical outcomes, in older children, as well as in newborn infants.

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Donor human milk, not toxic after all!

Posted on 31 January 2024 by Keith Barrington

It was fairly recently that I deconstructed a truly terrible database analysis which claimed that neonatal mortality was dramatically increased among very preterm infants who received mother’s own milk (MoM) and donor human milk (DHM), without any formula or fortifier, compared to a group which only received MoM and artificial formula. Almost certainly, this was because many of the deaths in the MoM+DHM group occurred before the babies had survived long enough to receive fortification. A baby who survived for a few weeks and then received some fortification or formula being deleted from the group, even if the change of diet occurred after the primary outcome (surgical NEC) had been determined! The study also claimed that MoM+DHM was associated with more surgical NEC (3.5%) than MoM+formula (1.7%), but with a difference much smaller than the enormous difference in mortality. This could well be another example of confounding by indication, and again, much of the feeding data were derived from medical record abstraction which included many days, or weeks, after the occurrence of the NEC, up to and including the day of discharge.

My letter to the editor about this has now been published. One thing I mentioned in my discussions of the data about DHM was the MILK trial, for which I included data from Clinicaltrials.org, and which has now been published. (Colaizy TT, et al. Neurodevelopmental Outcomes of Extremely Preterm Infants Fed Donor Milk or Preterm Infant Formula. JAMA. 2024).

The details of the protocol are now available, with the full publication. Eligibility included a GA <29 weeks or birth weight <1000g, 483 babies were randomized. If the mother never initiated breast milk expression, or stopped before 21 days of age, or produced “minimal” amounts of MoM, then the infant could be included, and randomized, which could therefore occur any time between birth and 21 days of age. The median age of randomization was 16 days, and the median age of starting oral feeds was 4 days. Which makes me wonder why, on average, these babies were not fed for 4 days? I think most babies, of any gestational age, can be fed on day 1. Our protocol is to only withhold feeds for babies in shock and/or on inotrope/vasopressors, which is a small minority, most extremely preterm babies receiving either MoM, or if not yet available, DHM, within 24 hours.

The eligibility up to 21 days dilutes the potential differences between groups, I suggest, as many babies will have had some MoM, or DHM, or formula, before they were enrolled. Even after being enrolled, many babies in both groups received some maternal milk, which is reported as the number of weeks of any MoM, and averaged about 1.7 weeks.

I’m not sure how many babies were in those 3 slightly different subgroups (no MoM, mother stopped expressing before 21 days, and mother not able to produce enough milk), but some analyses were done for the subgroup who had zero MoM. In the supplemental materials, it looks like there were 369 babies in total that completed follow up, 79 of whom had zero MoM; in other words it is a minority of mothers who never expressed at all.

The primary outcome variable was the Cognitive Score on the Bayley version 3, performed at 2 years corrected age. Another thing which I find a bit weird, is that the babies who died were assigned a cognitive score of 54 (the minimum possible); it is one way of integrating the competing outcome of mortality with developmental outcomes, but, depending on the risk of death, it could well dilute any difference in cognitive outcomes, especially if there were an imbalance in mortality. It also makes the scores look a lot lower than they really were, mean scores being about 5 points higher when the non-survivors assigned scores were removed. Scores on the language composite (44) and motor composite (49) were also assigned for babies who did not survive.

In any case, all of the developmental and neurological outcomes were very similar between groups. In the supplemental material the analysis restricted to the survivors is given, which shows that all of the mean and median scores are slightly better in the DHM group, but none of the differences are large enough to really have any clinical significance (and none are “statistically significant”). Interestingly, the differences are all greater in the “sole diet” subgroup, the median scores on each subscale being 5 to 6 points higher with DHM than formula, but the numbers are, of course, much smaller, and remain within 95% CIs.

Assigning the lowest possible score to the non-survivors leads to some slightly strange findings, for example, the Bayley motor composite scores among survivors were slightly higher in the DHM group, but identical when the non-survivors are added as scoring 49; and there was actually more cerebral palsy (all grades) in the formula group, 20% vs 15%.

For the short term outcomes, the most striking difference is in NEC, which was twice as frequent, 9%, in the formula group than in the DHM group, 4.2%. You may want to argue that NEC is a somewhat subjective diagnosis, but, as I haven’t yet mentioned, this was a masked trial. The study group went to some lengths to maintain masking, with feeds prepared daily by study staff in amber tinted syringes, which were continued for 120 days maximum, or until 1 week before anticipated discharge.

Another interesting outcome is that length and head circumference increased very similarly in the 2 groups, but the weight gain was a little greater in the formula fed babies. Both groups “lost” percentiles of length, and gained a little in head circumference, being born with weight and length z-scores of about -1, and head circumference z-scores of -1.4. At discharge the DHM group weighed about 140 g less. The Fenton standards were used to create the z-scores.

The study confirms the safety of donor human milk, and the reduction in NEC compared to artificial formula. This is despite the limitations in the study design, which made the study feasible (only enrolling babies whose mothers decided to not provide breast milk would have enormously prolonged the trial), but potentially diminished any difference between groups.

A recent editorial in Pediatric Research raised some reasonable concerns about the commercialisation of human milk for preterm infants, but suggested, with no real evidence, that there are also concerns about harm from DHM. It misquotes O’Connor’s previous RCT of MoM-receiving babies who either received supplemental feeds with DHM or artificial formula, and which also showed only tiny differences in mean cognitive scores, of 92.9 with DHM vs 94.5 with formula. The spread of scores was wider in the DHM group, so a somewhat larger proportion had scores between 70 and 85 in the DHM group, but this was a post hoc secondary analysis. The editorial also suggests that the mortality morbidity index was worse in the DHM group, in fact the tiny difference 43% vs 40% in this composite outcome was far from being significant, the only clinical outcome that was different in that trial was a much higher rate of NEC (stage 2 or 3, 6.6% vs 1.7%) with formula than DHM.

The MILK trial therefore confirms the benefits of DHM as a replacement for inadequate or absent MoM, compared to formula. It shows that NEC is lower, and there are no adverse effects. With reasonable standardized nutritional practices weight gain may be slightly less with fortified DHM than with formula, but length gain and head growth are very similar. Developmental outcomes are also unaffected, or are perhaps a little better with DHM, and maybe with less CP.

Although many of us are uncomfortable with the commercial side of human milk trafficking, most human milk banks are non-profit, and/or government supported, and most donors are altruistic women who wish to help others, and are fortunate enough to have a surplus of this precious resource. Our own local bank, like many others, does not accept donations from mothers who are within the first month of breast feeding their own baby, in order to not impact adversely on breast feeding their own infant. There are many challenges to ensuring adequate DHM supply, standardizing and optimizing nutritional intakes, adjusting fortification to alter nutrient supply by when growth is suboptimal. The MILK trial results confirm that responding to those challenges is worth the effort.

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Is there any indication to close the PDA?

Posted on 26 January 2024 by Keith Barrington

Yet another trial of PDA treatment and attempted closure with a null result.

Baby-OSCAR was a UK multi-center masked RCT of ibuprofen treatment of 23 to <29 week infants who were screened with echocardiogram within the first 72 hours of life, and randomized if the PDA diameter was >1.5 mm (Gupta S, et al. Trial of Selective Early Treatment of Patent Ductus Arteriosus with Ibuprofen. N Engl J Med. 2024;390(4):314-25). The echo criteria included the need for pulsatile left-to right shunting and no evidence of pulmonary hypertension.

There were few other eligibility restrictions. 3861 babies had echocardiograms for determining eligibility and 1271 had large enough PDA to be eligible, most of the failure to enrol was parental refusal, and the groups were well balanced, with a final sample size of 653.

The primary outcome was the dreaded “death or BPD”, meaning an oxygen requirement at 36 weeks or death before 36 weeks, babies who did not require oxygen after an O2 reduction test were considered “mild BPD” and not considered an adverse outcome. Babies on high-flow cannulae with 21% O2, however, were all considered to have severe BPD and did not have an O2 reduction test.

The primary outcome was not different between groups; the major outcomes are shown below:

As you can see there were more adverse outcomes in the ibuprofen group for just about every outcome.

I don’t understand, yet again, why mortality is only reported up to 36 weeks. There are no data I can find anywhere in the publication or supplemental materials about overall mortality. The results presented don’t, as a result, answer the most important question of all, “does early ibuprofen treatment of a large PDA have an effect on survival?”

You can’t even back-calculate survival to discharge from the home oxygen numbers, as 130 ibuprofen babies went home in oxygen, which is reported as being 41.3%, but that can’t be quite right; 130 is 41.3% of 315, which is less than the number randomized in that group (324), but is greater than the number of 36 week survivors (280). Perhaps 35 babies were resurrected after 36 weeks, and went home without oxygen? Similarly 123 control babies went home on oxygen, which is reported as being 39.2%, giving a total number of babies discharged of 314, but only 289 survived to 36 weeks.

All we know about mortality, therefore, are the numbers who survived to 36 weeks, and we have to hope that there wasn’t an imbalance of deaths between 36 weeks and discharge. According to the supplemental data, two secondary outcomes were determined at discharge, NEC and home oxygen, so the denominator, alive at discharge, should surely have been reported.

By the protocol of the Baby-OSCAR trial, open label treatment with ibuprofen could be given if the following were present:

  1. Inability to wean on ventilator (ventilated for at least 7 days continuously) and any of: inability to wean oxygen; persistent hypotension; pulmonary haemorrhage; signs of cardiac failure
    AND
  2. Echocardiographic findings of a large PDA (PDA ≥ 2.0 mm with pulsatile flow) AND
  3. Echocardiographic findings of hyperdynamic circulation or ductal steal (refer to Baby-OSCAR ECHO workbook).

I’m not sure what “signs of cardiac failure” means, I haven’t seen a definition in the protocol. There were 15 ibuprofen and 33 controls who received open label treatment without satisfying these criteria. In total 14% of the ibuprofen-treated and 30% of the controls received open-label treatment including both the by protocol and outside of protocol open-label use, the timing of which is shown in this survival graph

Despite the limitations of the design and the study report, there is no evidence of any benefit of early ibuprofen treatment of PDA of over 1.5 mm diameter, compared to selective later treatment. Subgroup analysis of the larger ducts, the babies receiving assisted ventilation, and by gestational age show no group with a benefit in either BPD or death. The most immature babies almost all have BPD, and there is therefore no difference in their primary outcome.

Much like the Beneductus trial there was actually more BPD in the treated group, a relatively minor difference in this trial, and a larger difference in that other trial, which otherwise has a number of similarities to Baby-OSCAR. Both required a PDA >1.5 mm diameter within 72 hours of birth, without signs of pulmonary hypertension. The average GA in each study was 26.1 weeks (even though Baby-OSCAR included 28 week babies, and Beneductus was <28 weeks, probably because there were more 23 week GA babies in Baby-OSCAR). One big difference with Beneductus, is that only one control infant had open-label PDA treatment in that trial, and with less cross over they showed a greater difference in BPD. Need for home oxygen is a much more clinically important outcome, and it seems to me to be very high among the babies in this trial, at about 40%, but was almost identical between groups.

The editorial accompanying the trial publication notes that there is very little evidence of any situation in which medical or surgical PDA closure improves clinical outcomes. However, it also includes the following “With more than half of the enrolled patients born at less than 26 weeks’ gestation and an absence of notable serious adverse events, early parenteral administration of the drug appears safe in this high-risk population and may ultimately reduce the need for surgical or transcatheter closure”. Which I think is a bizarre statement. Surely, if there is no apparent benefit, the fact that it is “safe” is irrelevant, even if it were true. And, even though I am very critical of the use of BPD as a measure of lung injury, the results from these 2 recent trials show an increase in BPD. The two previous trials of ibuprofen in the Cochrane review of early PDA treatment, in the subgroup of “very early treatment” (<72 hours of age), only included a total of 128 babies, one of which was a trial in China of oral ibuprofen, the other being Afif El-Khuffash’s pilot trial with 60 babies. Those two studies showed a possible decrease in “Chronic Lung Disease”, but are overwhelmed by the results from these 2 latest trials, which suggest that early ibuprofen treatment is not safe.

The editorial also begs the question of what is a “need” for surgical or transcatheter closure. Across Canada in the last 10 years, the percentage of babies <33 weeks who have had a surgical PDA closure has fallen from 3% to 1%, and among those who have a recorded diagnosis of a PDA has fallen from 10% to 4%. The best way to avoid surgical PDA closure may well be to just avoid surgical PDA closures.

One potential benefit of early PDA closure from previous studies was an apparent impact on pulmonary haemorrhage. Martin Kluckow’s trial of early indomethacin treatment showed a reduction in this serious phenomenon. The results of this new trial show no benefit for this outcome, the haemorrhages just look like they tend to occur later. The first column below is the ibuprofen group, the 2nd column are the controls, there were a few more pulmonary haemorrages in the ibuprofen group (blood in the endotracheal tube with a respiratory deterioration), and they occurred later.

You could also ask if having the pulmonary haemorrhage later might be a benefit, as the serious intracranial haemorrhages, which often occur at the same time, might be less frequent if the pulmonary haemorrhage occurs after day 3 to 6, but as the main table of the results above shows, there were actually a few more serious intracranial haemorrhages with ibuprofen than with control.

As far as I can tell then, trying to integrate these new data into the large literature that already exists, there is no clinical situation in which using medication to close a patent ductus arterious has been shown to improve clinically important outcomes.

The most evidence-based approach to the PDA therefore, appears to be to just to leave it alone.

It is possible that there exist clinical situations in which closure of the PDA is justified, but I think it is incumbent on anyone who thinks that is true to perform studies to prove that you improve clinically relevant outcomes with treatment in those situations. It may be, for example, that babies with a large duct with a large difference between left and right ventricular outputs and diastolic steal in the abdominal aorta would benefit from ductal constriction with early ibuprofen treatment, even though it is not very effective in closing the PDA.

But there are currently no subgroups in whom treatment has been shown to have more benefit than harm. Perhaps this lack of benefit is because ibuprofen is not very effective, but the only other options would be to either return to indomethacin, which is not much different in efficacy, or to routinely close by catheterisation or surgery. Those options are not realistic for the large majority of sick tiny preterm infants.

There are already centres who have decided to rarely, if ever, treat the PDA. In Montreal, for example, we have a difference in treatment approaches between our hospital (Centre Hospitalier Universitaire Sainte Justine, CHUSJ) and McGill, where they have decided to be extremely conservative, and have progressively reduced their rate of PDA treatment to close to zero. The two groups have just published some long term follow up results of babies <29 weeks, (Cervera SB, et al. Evaluation of the association between patent ductus arteriosus approach and neurodevelopment in extremely preterm infants. J Perinatol. 2024) over the period of the study, 2014 to 2017, the rate of PDA treatment fell from 33% to 0% at McGill, and remained much higher at CHUSJ. The new publication reports the neurological and developmental outcomes, which are close to identical between the 2 centres. Among the large number of comparisons the only one which is a bit different is the mean motor composite score, but the proportion with scores below various thresholds were identical, and all the cognitive, visual and other outcomes are very similar. The shorter term results show there is somewhat more BPD (using the usual diagnostic criteria) at CHUSJ, despite a much higher rate of PDA treatment, which was almost all with ibuprofen; over the years of that study we also had a 6% rate of PDA ligation, which has since fallen to about 0.

As mentioned above, there appears to be no longer any evidence-based indication for ibuprofen use to treat the PDA. Despite large numbers of trials, and multiple different attempts to determine whether we can improve outcomes with ibuprofen, or with acetaminophen/paracetamol, I am left wondering in what circumstances treatment is justifiable.

There will probably be other trials, and I would guess they will have to include older infants with persistent very large shunts, and will examine effective ways of closing the PDA, such as by catheterization. For now early treatment with ibuprofen appears to be relatively ineffective in closing the PDA, ineffective in improving any clinically important outcomes, and appears to lead to worse pulmonary outcomes. It will be essential to find out what the impact on mortality was in the Baby-OSCAR trial, and more clinically important respiratory outcomes.

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Time to open the DOOR

Posted on 17 January 2024 by Keith Barrington

I have written many times about the problems with classical composite outcomes in neonatal research. “Death or BPD”, “death or NDI”, or sometimes “death or NEC or Sepsis or BPD or severe IVH” have been used as a way of combining adverse outcomes that we want to avoid, and accounting for the fact that death is a competing outcome for many negative outcomes. The enormous problems with such composites is that they give equal weight, when evaluating an intervention, to the components of the composite. A baby who survives to 36 weeks but needs oxygen is considered equivalent, in terms of the analysis of the results, to a baby who dies.

This has led to a number of serious problems in interpretation of results, to the extent that interventions may, for example, decrease mortality, but if they have no impact on BPD the results may be considered null and “not statistically significant”. Composite outcomes have sometimes been used as a way of increasing power, but in reality they do not necessarily increase power. Especially if the components change in different directions, or if the most important outcome is less frequent than the less important components; in such instances power may actually be decreased.

I have suggested, in the past the Win Ratio approach, one way of planning and analyzing trials, in which outcomes are evaluated in a prioritised fashion, and death is considered the worst outcome, followed by survival with very severe BPD, followed by survival with less severe BPD… etc. Subjects can be compared in pairs to see which has the better outcome, this Win Ratio approach has been used in some trials, especially in adult cardiology studies. It is an approach which is most easily used if subjects are randomized in pairs. In more standard large RCTs, each subject in group 1 has to be compared to every subject in group 2, and the maths and the statistical analysis becomes more complex.

An alternative which has been used mostly, I think, in infectious disease research, is called the Desirability Of Outcomes Ranking. This article, for example, discusses how to design and analyze a trial using this approach (Ong SWX, et al. Unlocking the DOOR-how to design, apply, analyse, and interpret desirability of outcome ranking endpoints in infectious diseases clinical trials. Clin Microbiol Infect. 2023;29(8):1024-30). It was designed as a way of analyzing trials where there are a few deaths, some patients survive with complications, and others survive without serious complications. Ranking these outcomes according to their desirability. Exactly how to rank the outcomes, which also include, for example, treatment failure where the antibiotics don’t eliminate the infection, is an ongoing question, but should include important input from patients, or in our case, parents.

As usual, Anup Katheria is ahead of the game, and he has just published a reanalysis of the MINVI trial. This was a cluster randomized trial of cord-milking in term and near-term babies who were non-vigorous at 15 seconds of life. A cartoon of the protocol, from the original publication (Katheria AC, et al. Umbilical cord milking in non-vigorous infants: A cluster-randomized crossover trial. Am J Obstet Gynecol. 2022) is reproduced below.

The primary outcome of the MINVI trial was NICU admission for any of the following reasons “respiratory distress (tachypnea, grunting, or retractions), bradycardia or tachycardia, hypotonia, lethargy or difficulty arousing, hypertonia or irritability, poor feeding or emesis, hypoglycemia, oxygen desaturations or cyanosis, need for oxygen, apnea, seizures or seizure-like activity, hyperbilirubinemia, and/or temperature instability”. Although there were some apparent benefits of cord milking in the results, the primary outcome was 23% (cord milking) vs 28% (early cord clamping) and considered not ‘statistically significant’. Many of the individual reasons for NICU admission were slightly lower in the cord milking group.

This reanalysis (Katheria AC, et al. Application of desirability of outcome ranking to the milking in non-vigorous infants trial. Early Hum Dev. 2024;189:105928) used a DOOR approach. Which depends on a list of ranked outcomes which are shown below in the first column of the table; the table also shows the numbers and proportion of babies in each of the two groups, Umbilical Cord Milking (UCM) and Early Cord Clamping (ECC) who have that outcome as their worst outcome.

The DOOR analysis entails a calculation of how likely it is that a member of the UCM group will have a better outcome than a member of the ECC group. If the interventions are equivalent, then the possibility will be 50%, 95% confidence intervals can be calculated, and if they do not include 50%, then you can conclude, with 95% confidence, that the results are different. You can see in the figure below that the overall DOOR ranking was more likely to favour ECM, with the percentage of the comparisons between UCM and ECC babies favouring UCM being 56%, with 95% CI of 53 to 59%, and each component of the score favouring UCM, except for mild HIE being equivalent.

The last author of this new paper with Anup Katheria has been heavily involved in developing this approach in infections disease research, and they have an extra twist in those studies, that, if there is a tie in outcomes, you can take into account the duration of antibiotic use. Getting an equally good clinical outcome with a shorter course of antibiotics is considered an advantage. I think they mostly invented this wrinkle for the cute acronym RADAR (Response Adjusted for the Duration of Antibiotic Risk) Evans SR, et al. Desirability of Outcome Ranking (DOOR) and Response Adjusted for Duration of Antibiotic Risk (RADAR). Clin Infect Dis. 2015;61(5):800-6. I’m not sure how this could be adapted to our population, but I like the idea that if you get equally good outcomes with less intervention, that is a good thing.

I know there are other groups that are already considering this approach, which I think could be easily adapted to be a much better primary outcome variable for clinical trials in neonatology. It clarifies the difference in outcomes between groups, giving greater weight to worse outcomes. How to develop the prioritised list of outcomes, and what order to place them in, should definitely be done in collaboration with parents.

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To bolus or not to bolus? Not really a question…

Posted on 19 December 2023 by Keith Barrington

Many preterm babies receive boluses of normal saline, often during the first 24 hours when their blood pressure is lower than desired. I have 3 serious questions about this.

  1. Are they indicated?
  2. Do they work?
  3. Are there adverse effects?
  1. Do hypotensive newborn infants have low blood volume?

The rationale for giving a fluid bolus is that the infant may be hypovolaemic, if they are, then you really don’t want to start other therapies if you could simply correct the hypovolaemia. I have some sympathy with this idea, I certainly wouldn’t want to start an epinephrine infusion if all the baby needed was to have 10 mL/kg of saline. But what is the likelihood that a hypotensive very preterm baby may have a low blood volume? There are a couple of studies that have attempted to measure circulating blood volumes in preterm babies, neither show any correlation between volume and BP, or volume and the occurrence of hypotension. Both studies were performed before widespread use of delayed cord clamping, which is very likely to make the association even rarer.

Generally then, no; preterm babies with hypotension are unlikely to be hypovolaemic, and after DCC extremely unlikely to be hypovolaemic. Unless the baby had a cord prolapse, vasa praevia, or was unable to have DCC for some reason, I don’t think we should even consider hypovolaemia. It is a rare reason for babies to be hypotensive after birth.

What about sepsis?

This is a trickier issue, the haemodynamics of neonatal sepsis have not been studied in as much detail as I would like, there are a few studies, which have studied mostly infants with Gran-negative sepsis, who may develop shock from the haemodynamic responses to endotoxins, or as a result of systemic inflammation.

It has become a sort of gospel in treatment of sepsis in older patients that they need huge amounts of fluids, 60 ml/kg is often given before patients are considered fluid unresponsive, at which time inotropes may be added to their therapy (this is what the current CPS recommendations for sepsis treatment in children state). But more recent trials in adults with septic shock are casting doubt on this approach. Two new large RCTs (here and here) have shown no harm from a restrictive approach to fluid management compared to liberal fluids. Admittedly to be enrolled in those trial the adults had to have already received a litre of fluid, but that is an awful lot less than 60 mL/kg. An updated meta-analysis including those trials confirmed a lack of difference with liberal compared to restrictive fluid management. Indeed the only large RCT I am aware of in children with septic shock showed an increase in mortality with fluid boluses.

As there is no good data in babies with septic shock, I think that an initial bolus of 10 mL/kg is reasonable, but may not actually turn out to be a good idea, after that the approach should be based on improving overall perfusion if it is impaired, increasing BP, if it is low and associated with poor perfusion, and/or improving perfusion of vital regions. Overall haemodynamic evaluation with functional echo, and regional evaluation with NIRS might help, but that is about as evidence-based as one can get. I start steroids early in treatment of septic shock, although I don’t know for sure that is right, 2 to 6 hours after starting hydrocortisone at lowish dose (2-3 mg/kg/day) things are usually getting better.

2. Do fluid boluses increase BP?

To return to our hypotensive preterm without evidence of sepsis, there is very little evidence that boluses even increase blood pressure. With the knowledge that BP is likely to trend upward anyway, you can only really answer this question with an RCT, but to my knowledge there has never been an RCT of bolus vs no bolus in hypotensive preterms.

Years ago, I did a little before and after study where we gave 15 mL/kg of 5% albumin to hypotensive preterms, and showed that mean BP increased by a mean of 2 mmHg for about 20 minutes, before returning to baseline, echocardiography at the time showed an increase in left ventricular output, but not right ventricular output, which means, in preterm babies with an open PDA, that the only thing the boluses did was to increase ductal shunting without improving systemic flow.

There are a few other short term haemodynamic studies showing very similar findings, i.e. increase in ductal shunt, little or no effect on BP.

3. Are there adverse effects?

This new publication (Sehgal A, Gauli B. Changes in respiratory mechanics in response to crystalloid infusions in extremely premature infants. Am J Physiol Lung Cell Mol Physiol. 2023;325(6):L819-L25) is what triggered this blog post, Arvind Sehgal and Bishal Gauli from Monash in Melbourne, recorded dynamic pulmonary mechanics from the VN500 ventilator before, during and after administration of a crystalloid bolus that had been prescribed by the clinical team.

Ventilator setting remained the same in these babies <29 weeks who were on volume guarantee ventilation. So a change in dynamic lung compliance will lead to a change in peak inspiratory pressure if the baby’s efforts remain similar.

There was a trivial increase in BP with the boluses, 2 mmHg, which may well have been due to the variable nature of BP. As you can see, there was a worsening of dynamic compliance, leading to an increase in PIP, associated with an increase in FiO2.

The most likely explanation is an increase in pulmonary interstitial liquid, perhaps secondary to the increase in ductal shunting.

In view of the lack of evidence of hypovolaemia, the lack of response in BP, and the adverse effects, fluid boluses should generally be avoided in hypotensive preterm infants.

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Early routine surfactant, method and outcomes

Posted on 13 December 2023 by Keith Barrington

Two important new studies of the use of very early routine surfactant, compared to later selective surfactant if necessary. The first I will discuss is the one that didn’t seem to improve any important clinical outcomes (Murphy MC, et al. Prophylactic Oropharyngeal Surfactant for Preterm Newborns at Birth: A Randomized Clinical Trial. JAMA Pediatr. 2023 the POPART trial). 252 infants of less than 29 weeks (mean GA 26 weeks) were randomized prior to birth in 9 university hospitals in 6 European countries, co-ordinated by Colm O’Donnell in Dublin. The intervention was the instillation of 120 mg of Poractant into the pharynx for infants <26 weeks, and 240 mg for those 26-28, this was done without any suctioning, and prior to any positive pressure, ideally before clamping of the cord at 30 to 60 seconds after delivery. Only a small number of babies were protocol violations, being intubated outside of protocol defined indications. After the oro-pharyngeal surfactant, babies followed standard stabilisation, including intubation if required, and any baby thought to need surfactant was treated with the usual surfactant dose thereafter (either by intubation or LISA).

The primary outcome was intubation for respiratory failure in the 1st 120 hours of life, with fairly objective criteria, even though the intervention was, unsurprisingly, unmasked. As you can see here, there isn’t a hint of a difference between groups.

The only difference in secondary outcomes was an increase in pneumothoraces in the surfactant group, 17% vs 6%, not likely to be a random difference. Clinical BPD (70 vs 69%) and physiologic BPD were also just about identical, there was a minor difference in NEC, favouring the control group, and in home oxygen, favouring the surfactant group. Mortality was identical also, 18% in each group.

The rationale for the trial was based on previous pre-clinical data in rabbits showing that the administration method does lead to pulmonary surfactant deposition, and an old RCT in 328 babies of 25 to 29 weeks GA, with a dry powder surfactant which is no longer available, called ALEC (Artifical Lung Expanding Compound, which was developed by Colin Morley) in the Ten centre trial of artificial surfactant in very premature babies. (Ten Centre Study Group. Br Med J (Clin Res Ed). 1987;294(6578):991-6). In that study the prophylactic administration was performed in the delivery room, in a similar way to the POPART trial. In the Ten Centre trial, mortality was lower with surfactant. ALEC was a mixture of two phospholipids, DPPC and PG, and was eventually taken off the market as it was, overall, somewhat less effective than liquid surfactants containing protein.

Why ALEC would work, and lead to lower mortality, but poractant would not, and lead to increased pneumothorax, is not clear to me. Clearly, in the last 35 years many things have changed in neonatology, (I have witnessed all of them!) the Ten Centre group studied 328 babies of 25 to 29 weeks gestation, of whom 19% of the ALEC group and 30% of the controls died, with an overall mean GA of just under 28 weeks. Unfortunately there are some problems with the study design of that trial, it started as a much smaller pilot trial published in the widely circulated journal (!) known as “Colloids and Surfaces”, the results of which were published after about 35 babies of 25 to 29 weeks were reported, and there were 5 deaths in the control group, and 0 in the ALEC group. The later publication in the BMJ appears to have included and re-reported the outcomes of those pilot trial babies, as well as a much larger group added on after the initial benefit was shown. Routine early CPAP was not typically used in the Ten Centre study, perhaps that is why early prophylactic ALEC surfactant was effective, in comparison to standard care, which did not include routine early CPAP.

The mortality is overall about 50% higher in the old study, despite a substantially lower GA in the new trial, demonstrating some of the amazing improvements in survival over this time period. Overall respiratory and ICU management is so much better, that there are no apparent benefits from this intra-pharyngeal prophylactic approach. The controls in the older study did not receive routine CPAP, but in both control groups in the 2 new studies, controls routinely were supported with CPAP.

One thing which is not mentioned in the POPART manuscript, or in the protocol, is the use of caffeine, which although frequently given early, is not often given in very early life.

That is one of the 2 major differences between PROPART and CaLI, the routine administration of intravenous caffeine in the 1st 2 hours of life, the other difference being direct intra-tracheal surfactant administration by the LISA procedure, after the caffeine.

In the CaLI trial, which is unfortunately not open access (Katheria A, et al. Caffeine and Less Invasive Surfactant Administration for Respiratory Distress Syndrome of the Newborn. NEJM Evidence. 2023;2(12)), it was funded by Chiesi, I would have thought they could pay for open access as well! 180 babies between 24 and <29 weeks were randomized. The protocol was as briefly outlined above, Caffeine and CPAP versus Caffeine, LISA, and CPAP. To be enrolled, babies had to be breathing and stable at 5 to 60 minutes of age, if enrolled, babies were then weighed and had IV access inserted. LISA followed at least 5 minutes after the 20 mg/kg load of caffeine citrate. In the CPAP group, early postnatal caffeine was also given, which was intended to be before 2 hours of age in both groups.

Randomization was performed at an average of 7 minutes of age, the caffeine was given at a median of about 50 to 60 minutes, and the LISA performed in the LISA group at a median of 1.5 hours, IQR 0.9 to 2. The primary outcome of the trial was the diagnosis of respiratory failure in the first 72 hours of life, the criteria for which were an FiO2 of >40%, respiratory acidosis with a PCO2 >65 on 2 gases, or lots of apneas.

The primary outcome was dramatically reduced by Caffeine plus LISA, compared to Caffeine alone. 23% vs 53%, the benefit was very similar in the 2 GA strata, 44% vs 80% in the 24 to 26 wk group and 14% vs 51% in the 27 to 29 weeks group.

I am actually a bit confused about what exactly was the primary outcome. In the text of the document it is written, “The primary outcome of the trial was the frequency of neonates requiring endotracheal intubation or meeting respiratory failure criteria between the two groups (caffeine and LISA vs. caffeine and CPAP) within the first 72 HoL” but then the tables just mention intubation, and babies in the caffeine plus CPAP group could have had LISA without necessarily being intubated. In the table showing the primary outcome results,

the implication is that all the babies counted were actually intubated, even though LISA was permitted in the caffeine alone group. LISA is not much used in the USA currently, so perhaps all the “intubation or respiratory failure” babies were actually intubated. There were only 3 deaths, all in the CPAP without LISA group.

Among other outcomes, there was no sign of adverse effects, and the proportion of babies in oxygen at 36 weeks fell from 35 to 21% in the LISA group. I previously discussed the presentation of these results at the PAS earlier this year, and how Anup Katheria, the first author and PI, put the results together with the OPTIMIST trial. There aren’t yet any data on more clinically important long-term respiratory outcomes with the CaLI approach, but follow up is planned, and, if such outcomes are improved, we will have to figure out the best way to implement the approach. I’d love to figure out how to reduce the discomfort/pain of laryngoscopy, without any respiratory depression, and be more comfortable at performing LISA in the 50% of babies who would never have needed intubation.

CORRECTION: post changed 15 December 2023: The post initially read that the protocol violations in POPART were of babies “being intubated before the POPART intervention”. Colm O’Donnell has informed me that I misinterpreted the violations, the protocol violations were all babies who received the intervention, but were intubated outside of protocol indications, such as because they were “very small” or “needing a lot of oxygen”. As Colm also points out, if there was insufficient surfactant reaching the lungs to improve lung function, then how could the increase in pneumothoraces be blamed on the intervention? (I paraphrase), he is right of course, it doesn’t make much sense, so I guess the difference in pneumothorax rates may just be an accidental occurrence. As for caffeine timing, it isn’t known exactly when the babies in POPART received their caffeine, but they probably mostly received it quite early….

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Umbilical cord management at birth for preterm infants

Posted on 24 November 2023 by Keith Barrington

The Lancet just published back-to-back articles from the iCOMP collaborative reporting the results of the Individual Patient Data Meta-analysis of trials of differing cord management techniques in preterm infants. There were 48 trials with a total of 7000 patients in the IPD which made 3 comparisons Delayed compared to immediate clamping, and each approach compared to cord milking. Seidler AL, et al. Deferred cord clamping, cord milking, and immediate cord clamping at preterm birth: a systematic review and individual participant data meta-analysis. Lancet. 2023.

The data were analysed by subgroups above and below 32 weeks. Above 32 weeks there was very little evident impact on the outcomes that they analyzed, IVH, need for transfusion, NICU admission, and temperature on admission; which is what you would expect. The advantages in larger babies are probably more long term, with higher iron stores and less later anaemia.

Below 32 weeks the results can be seen below: clear advantages of DCC compared to ICC; no major advantages of cord milking compared to ICC; and the major difference between DCC and milking being more severe IVH with cord milking.

For the first comparison, 80% of the weight of the meta-analysis of mortality comes from 3 trials, APTS 58%, a trial from Egypt which is inaccessible, (not listed on Pubmed, or in Embase, and the journal does not appear to have a website, so I am unsure how iCOMP even found it!), weight 14%, and the UK CORD pilot trial (8% weight). The remaining are all small trials with between 4 and 50 per group. The CORD pilot trial was a trial of at least 2 minutes of DCC, with resuscitation, if needed, with the cord intact.

Other analyses performed included the impact of multiple delivery (only available for 4 trials, many trials have excluded multiples) and of gestational age. Neither of these factors appear to have an impact on the advantages of DCC.

The second paper tries to evaluate the data regarding how long to delay cord clamping (Seidler AL, et al. Short, medium, and long deferral of umbilical cord clamping compared with umbilical cord milking and immediate clamping at preterm birth: a systematic review and network meta-analysis with individual participant data. Lancet. 2023), dividing the studies up into 3 groups, 15 to 45 seconds, 45 seconds to less than 120 seconds, and 120 seconds or more. Almost all of the information for the longest delayed group comes from the same UK CORD pilot trial, the other trials with longer delays had more predominantly mature infants, and therefore few events. In particular there were very few severe IVH, so they don’t even report that, in the UK trial there were 6 and 7 severe IVH in the two groups, and the other trials had tiny numbers of babies at risk, or excluded the most immature, or had 0 events.

The analysis of the longest duration of delay therefore relies almost entirely on the results of the CORD pilot trial, which was a well-done trial, delaying cord clamping for at least 2 minutes, and even longer if the physicians felt comfortable waiting for longer, up until there was no evident pulsation. Babies needing resuscitation were treated next to the mother on a hard surface. Many babies in the DCC group actually had clamping earlier as can be seen here:

Many of the early clamped babies in the DCC group of the CORD pilot trial had good reason for early clamping, such as abruption, or the baby being born with the placenta, but many were because the “cord was too short” which, the authors note, became less frequent with time, or for “clinical decision”, which is not further explained.

I remain somewhat sceptical about Network Meta-Analyses, especially for indirect comparisons, where interventions that have not been directly compared are evaluated against each other as if they had been. The huge advantage of a true RCT, that all confounding variables tend to even out, those which you know about as well as those you don’t, is lost with an indirect comparison, such as in an NMA. No matter how much effort is put into correction for baseline imbalances, there always will remain the possibility of residual confounding.

The results of the NMA for these 3 outcomes (all are compared to ICC as the reference group) suggest that the longest delay gives the most mortality benefit. But I don’t think that this should lead to everyone aiming for 2 minutes in every baby. Only one tiny trial directly compared short duration DCC to longer duration. But the NMA, showing the biggest reduction in mortality with the longer delay, is mostly dependent on the trial of Duley, which, individually, showed a small reduction in mortality with longer delay in clamping, which may have been due to random variability. Although this trial had more deaths in the ICC group, the difference in deaths was almost entirely among larger babies of 26 to 32 weeks (8/108 deaths compared to 1/107) and may have been a random occurrence in a smallish trial.

The NMA gives sufficient evidence that further trials examining the relative impacts of 60 to >120 seconds of DCC are warranted. The ABC3 trial was presented recently at the JENS meeting in Rome, it was a trial in very preterm infants comparing an approach similar to what many are currently doing, that is, immediate clamping if the baby needs intervention and DCC of 30 to 60 seconds if the baby is doing well. This approach was compared to DCC and clamping being performed after the baby was stabilised, with a good heart rate and oxygenation, resuscitation if needed was performed with the cord intact, and clamping could be delayed up to 10 minutes. There were no differences in the outcomes reported at presentation of the results, mortality or IVH. I think we should therefore wait until this, and other ongoing trials are published, before longer delays in clamping, and resuscitation with an intact cord becomes the standard.

Take home messages: for mildly preterm infants at low risk of IVH, DCC is preferable to ICC, but milking may be a reasonable option if DCC is not feasible; for very preterm infants at risk of mortality or IVH, DCC is preferable to either ICC or milking. Longer durations of DCC, with resuscitation on an intact umbilical circulation, are not yet proven to further improve mortality or other clinically important outcomes.

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Which Probiotic is Preferable?

Posted on 21 November 2023 by Keith Barrington

The word “probiotic” is defined rather vaguely as a micro-organism which has beneficial health impacts. I think it is obvious that there is a huge difference between fungi that are found in the intestinal microbiome of adults, and the lactic acid bacteria which are major components in the young infant.

Even that term “lactic acid bacteria” includes organisms which are dramatically different. Lactobacilli, of the phylum Firmicutes (also called Bacillota), are gram positive rods which are facultative anaerobes, and have limited synthetic capacity, fermenting hexoses to produce lactic acid. Bifidobacteria are Bifid gram positive rods, hence the name, they are often portrayed as tiny little ‘Y’s, and are from a different phylum, the Actinobacteria (or Actinomycetota). They are obligate anaerobes, and have varying abilities to metabolise Hexoses, but remarkable abilities to metabolise oligosaccharides (Human Milk Oligosaccharides, HMOs) that are present in large quantities in breastmilk, but which humans lack the ability to digest.

The only reason these HMOs are present in breastmilk is to feed the Bifidobacteria, which, when they are established and reproduce, come to dominate the intestinal microbiome of the breastfed baby. In particular, a subspecies of B Longum, known as Bifidobacterium Longum ssp Infantis, is a micro-organism that seems to have co-evolved with humans, and is able to digest just about the entire range of HMOs, of which there may be over 200. (Underwood MA, et al. Bifidobacterium longum subspecies infantis: champion colonizer of the infant gut. Pediatr Res. 2015;77(1-2):229-35). HMO composition of human milk is variable, but B Infantis has 24 glycoside hydrolase genes and, alone among GI commensals, possesses sialidases and fucosidases allowing it to digest all types of HMOs.

I don’t for a minute think that breastmilk composition and B infantis evolved in this symbiotic manner in order to prevent NEC! But the GI tract of the full term newborn, who had a possibility of survival, is a haven for nasty pathogens, that can thrive if they have access to food, and which sometimes need access to iron. Hence the presence of Lactoferrin in substantial quantities in breastmilk, which binds iron to keep it out of the clutches of certain Gram negatives, and allows very high bioavailability of breastmilk iron, shuttling it into enterocytes, via specific human lactoferrin receptors, that strip off the iron and resecrete the lactoferrin. Hence the presence of those HMOs, which feed bifidobacteria but for which many pathogens, such as E Coli, Clostridia, Enterobacter and Staphylococci, completely lack the enzymes required to feed on them.

During the evolution of humanity it looks like the constant pressure to avoid GI and systemic infections, in order to survive to be able to pass on our genes, led to this symbiotic relationship between breastmilk and B Infantis. It led to the evolution of breastmilk that is packed with molecules that can only be utilised by Bifidobacteria, and specifically with a high degree of activity by B Infantis. B Infantis can inhibit the growth of other organisms, as well as starving them by eating up all the HMOs, and reduces inflammation by damping down the activity of the TLR4. TLR4 has an affinity for G negative LPS endotoxin, and seems (probably, I guess, by accident) to be overexpressed in the very immature bowel (Meng D, et al. Toll-like receptor-4 in human and mouse colonic epithelium is developmentally regulated: a possible role in necrotizing enterocolitis. Pediatr Res. 2015;77(3):416-24).

B Infantis also seems to decrease gut permeability and translocation of pathogens, at least in part by stabilising tight junction proteins. (Bergmann KR, et al. Bifidobacteria stabilize claudins at tight junctions and prevent intestinal barrier dysfunction in mouse necrotizing enterocolitis. Am J Pathol. 2013;182(5):1595-606.)

When there are a lot of B Infantis about, their metabolic activity leads to production of acids, lactate and acetate, and other short chain fatty acids. Which leads to a low stool pH. A fascinating study published 5 years ago (Henrick BM, et al. Elevated Fecal pH Indicates a Profound Change in the Breastfed Infant Gut Microbiome Due to Reduction of Bifidobacterium over the Past Century. mSphere. 2018;3(2):10.1128/msphere.00041-18) traced the changes in stool pH over the last century, as recorded in various publications, and showed that stool pH in breast fed babies used to be as low as 5, and has increased to as high as 6.5. There is a clear correlation between this increase and lower colonization by Bifidobacteria.

The intestinal protection afforded by this normal microbiome is the reason behind the use of probiotics, my micro-review suggests strongly that B Infantis is the most promising candidate of all the strains.

Sanjay Patole and others in Perth have performed a number of meta-analyses of the clinical trials of probiotics in the preterm, and the most recent focuses on the trials that have used B Infantis, as either the sole probiotic, or as a component of a mixed probiotic preparation. (Batta VK, et al. Bifidobacterium infantis as a probiotic in preterm infants: a systematic review and meta-analysis. Pediatr Res. 2023).

As you can see from this Forest plot, there are a large number of trials, including B Infantis or without, with a total of over 14,000 babies. The trials which included a B Infantis in the treatment group had a reduction in NEC with the RR of 0.38 (0.27, 0.55 95% CI) compared to those with other organisms which had an RR of 0.59 (0.50, 0.70). The statistical test for subgroup differences suggest that this differential impact is unlikely to be due to random effects.

That SR also includes similar plots for overall mortality, preparations with B Infantis RR=0.65 (0.48, 0.88) compared to placebo, preparations without B Infantis compared to placebo, RR= 0.78 (0.67, 0.91). For Late-Onset Sepsis, RR=0.8 (0.63, 1.01) with B Infantis, compared to 0.86 (0.77, 0.97) without B Infantis.

The minor problem with this SR is that, as mentioned B Infantis is a subspecies of B Longum, the other subspecies being B Longum ssp Longum. A few RCTs have stated that they used B Longum, without specifying the subspecies, at least one of them used a mixture “Restore” that they report as including B Longum, when I went on the website of the company that produces Restore, they state that it is a B Longum ssp Infantis. However, the study had so few cases of NEC, 2 vs 1, (and is so badly written that I cannot tell whether group A or group B received the probiotics!) that it would make no difference to the meta-analysis. Another small trial used a mixture containing B Longum, but neither the publication nor the website of the company states which subspecies is in the mixture “Darolac”.

Indeed, this is a major problem in many parts of the world, the quality control standards and certainty of the identification of the strains in the various available products are often very poor. Mixtures may contain no live organisms, different organisms to those claimed, and/or pathogens. It is essential to find a preparation with the production standards required to ensure that you are really giving the organisms you want, and not others.

If B infantis, or other “probiotic” organisms, are able to enter the blood stream, which usually occurs only when the intestinal barrier has been breached, they do not produce lipopolysaccharide endotoxins, as do most pathogenic Gram negatives, which are responsible for much of the inflammation. Nor do they produce any exotoxins, as does Group B streptococcus and some Gram negatives. Which is why most of the babies described in the literature have had minor illness when they have a bacteraemia with these organisms, they just are not very pathogenic. It really is essential to make sure that you are not giving any of the bad bugs when you try and supplement with the good guys.

The most likely candidate, as a single strain of organism that could vigorously colonise the preterm intestine, digest HMOs, decrease inflammation, decrease intestinal permeability, inhibit the growth of pathogens, and has been shown to be a preferentially effective probiotic against NEC in this species selective Systematic Review is B Infantis. The very organism that the FDA has just forced off the market.

UPDATE: of note, David Mills, a real expert in this subject, sent a comment (and a reference) pointing out that many commercial probiotic preparations, that are supposed to contain B Infantis often do not! There may be other Bifidobacteria, such as a B Infantis that turned out to be B lactis, and there is even variation from lot to lot. This casts a shadow over the meta-analysis above, as it is possible that some of the preparations in the B Infantis group may not actually have contained B Infantis, clearly, all future studies must reliably ascertain the strain used.

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