Will the edge of viability be redefined before long?

Will the edge of viability be redefined before long?

I couldn’t think of a better topic for World Prematurity Day 2021 than what constitutes the edge of viability. Thinking back over my career, when I was a resident and fellow infants born at 25 and 26 weeks were deemed about as low as “we should” go but we certainly resuscitated infants at 24 weeks but this was considered heroic. Jump ahead to the last decade and we began caring for infants at birth at 23 weeks so commonly that the thought of offering comfort care only to infants at 24 weeks became almost unthinkable for many health care providers. Before I get jumped on, let me say that I am not saying I agree or disagree with that sentiment but it is something that is felt by many.

The Shared Decision Model

In the last few years a rethink again has occurred whereby the concept of the treating team knowing best has been replaced by the “shared decision model”. In this line of thinking, it is not up to us as health care providers to “tell the parents” what to do but rather come to a shared decision based on an assessment of the wishes and values of the parents in conjunction with hearing about both short and long term problems their infants may face if resuscitated. This concept was central to the statement by the Canadian Pediatric Society that I am proud to have been part of with respect to its development. The statement for those that are interested is Counselling and management for anticipated extremely preterm birth

What’s next? Going below 22 weeks?

The challenge of the shared decision model is that there comes a point where the answer is simply “no”. If for example a family at 19 weeks gestation demanded an attempt at resuscitation I would have to inform them that survival is not possible (assuming ultrasound confirmed anthropometric measurements consistent with that age). The question though becomes a little more difficult to answer at 21 weeks and was the subject of a recent article in the New York Times about a survivor at 21 weeks gestation.

Even with the best gestational age dating the estimate can be off by up to 5 days so it’s possible that the infant in this story was closer to 22 weeks or even midpoint between 22 and 23 weeks in reality. Regardless it does raise the question about what to do at 21 weeks and I suspect we will begin to see more stories about this now that the glass ceiling of 22 weeks has been breached. What about below 21 weeks? Sounds impossible I know but with research that remains at the stage of animal studies this may become possible. Maybe not in the next 5-10 years but it could happen in my lifetime in this chosen field.

The Artificial Placenta

This made headlines a few years ago with the news that the Children’s Hospital of Philadelphia had successfully kept a lamb alive for a period of 4 weeks using an artificial placenta and amniotic fluid.

You might think that this was a one-off experiment that will never see the light of day but similar work is being done in Toronto, Canada where they have been able to do similar work with preterm piglets in their paper Achieving sustained extrauterine life: Challenges of an artificial placenta in fetal pigs as a model of the preterm human fetus. Incidentally as my colleague Dr. Ayman Sheta worked on this project while in Toronto I am particularly pleased to share this research. Similar to the experience in CHOP the team in Toronto has been able to keep piglets alive for progressively longer durations. My understanding is that despite the best efforts infectious complications over arise limiting how long one can sustain such animals.

This leads me to my final thoughts on where we might be able to go. I see a future where we apply such technology to humans but not in the way that people might have thought. Keeping a fetus after delivery at 21 or 20 weeks on an artificial placenta for many weeks is not likely a realistic goal. What if we could get 1 or 2 weeks though and allow the fetus to be oxygenated without using positive pressure on their developing lungs and transition them at 23 or 24 weeks gestation? We may in this way be able to allow for postnatal maturation in a artificial uterine environment and give babies a chance who would otherwise never had the opportunity for a shared decision with medical staff.

Sound like science fiction? Well the beauty of the internet as my friend told me today is that once it’s out there it out there for good. Let’s see how this post stands the test of time and to all the babies out there in NICUs and to their families I wish you all a good and uneventful World Prematurity Day wherever you may be!

What strength of chlorhexidine is best in NICU?

What strength of chlorhexidine is best in NICU?

In NICU we are always vigilant for infections. Bacterial sepsis is not uncommon and in fact in the latest 2020 Canadian Neonatal Network annual report, 9.4% of all babies across Canada born at < 33 weeks gestation experienced an infection after 3 days of age. Looking at the rate of infections in those with central lines (Central Line Bloodstream Infection or CLABSI the rate was 2.9/1000 line days. Infections in NICU are not surprising given that these infants often have need for vascular access and needle pokes breaking the skin and have a somewhat fragile immune system associated with premature birth. There are many strategies to reduce infection risk in the NICU but one in particular that has been around a long time is cleansing of the skin before any skin breaking procedures are performed such as for blood draws. Options exist for cleaning in terms of solution and whether it contains alcohol or not. A common skin antiseptic used is chlorhexidine which comes available as a 2% or 1% solution and with or without alcohol. The babies in particular who are our smallest may be sensitive to the alcohol and may be left with skin burns so for the smallest of infants we often clean without the alcohol containing solutions. What we are going to talk about today though is the use of 2% vs 1% and whether one is any different than the other in terms of effectiveness.

The Study

The study was done in India by Sharma A et al and entitled Aqueous chlorhexidine 1% versus 2% for neonatal skin antisepsis: a randomised non-inferiority trial. The authors set out to determine a number of things. The primary outcome was the percentage of negative skin swabs after application of both but they also looked for evidence of harm in terms of skin rashes and chlorhexidine blood levels. The strategy employed was for the investigator to identify a 4cm2 skin area to obtain the pre-antisepsis skin swab from one of the following sites: cubital fossa, dorsum hand or dorsum foot. Each patient could be enrolled again after a 96 hour period of time had elapsed. An alternate site was selected at the time of repeat enrolment. Each patient had a swab of this area done in a specific and repeated way in terms of strokes of the skin and then in a randomized fashion each patient received either the 1% or 2% solution on a swab. The solution was tested by a pharmacist throughout the study to validate the concentration of chlorhexidine (swab was dipped in the tested solution) and then applied in a consistent manner to the skin area. The area was left to dry for 60 seconds and then a second swab taken to determine whether the skin had been cleared of the bacteria that would have been picked up by the swab pre-chlorhexidine. The study set a target of a 5% non-inferiority limit comparing the two concentrations with an expected efficacy of about 90% for a 2% chlorhexidine solution to sterilize an area. This meant that if the efficacy of the 1% solution fell below a 5% difference it would be deemed to not be equivalent to the 2%.

What did they find?

First of all the groups were comparable in baseline characteristics. The babies enrolled in the study ranged from 26 0/7 to 42 6/7 weeks at delivery. As planned the groups; 341 to 1% and 344 to 2% were stratified for analysis into 26 0/7 to 27 6/7, 28 0/7 to 34 6/7 and 35 0/7 to 42 6/7 groups. The means GA and BW for each overall group however were 2018 vs 2029 and 34 vs 35 weeks for 1 and 2% groups.

The table above has all the relevant information from the outcomes of interest. The efficacy of the antiseptics was a bit better than anticipated at 93% for the 1% vs 95.6% for the 2% group. On the surface you might be tempted to jump up and say “ah ha! They are equal”. However when you look at the 95% CI around the estimates you get a risk difference of -2.7% but the lower CI limit is -6.2% so as the authors concluded they are in fact not equal. Looking at the subgroups the number show some differences but only the middle group reached a statistical difference.

Importantly contact dermatitis which was scored by nursing using a standardized approach showed no difference at any time points. As expected some absorption did occur from application of the swabs but there was no difference between the two concentrations of significance although interestingly the higher concentration solution trended lower.

The authors do point out in this study that they did not get the 355 patients they wanted in each group although I have to say it was so close that I don’t believe adding a small percentage more of patients to the study would have been likely to change the conclusions.

Lesson from this study?

I suppose the first thing I take is that I am relieved that since our unit uses the 2% solution I don’t see any need for change. The second thing is that the rate of dermatitis from either solution is limited to about 1/10 babies after application but by 6 hours it is gone. Both have very high rates of successful skin antisepsis but if there is really no contraindication in terms of either skin irritation or high levels of drug in the blood my bias would be to grab onto the extra few percent successes at clearing the skin of bacteria. Even if it only a 3% gain, if we can maximize the cleaning of the skin before we poke a needle through it I think that is the way to go. If there are centres out there using the 1% though and plan on sticking to it I would be curious as to why?