If you have had a baby born prematurely and are reading this blog post you may have been told that the medical team is looking for a PDA. The PDA stands for Patent Ductus Arteriosus and the last two words Ductus Arteriosus really helped your fetus as it was growing in the womb. In order to understand how it can cause a problem after birth it is first important to understand what it did and why it exists in the first place.
Act I – The Womb
When your baby was developing its lungs the tissue was busy branching into airways that ended in little air sacs called alveoli. Each of those alveoli was next to a capillary which is our smallest blood vessels in the body. One day these units (alveolus and capillary) will happily exchange oxygen that is breathed in for carbon dioxide that needs to be breathed out. In the womb though the lungs were filled with fluid and air was nowhere to be seen. As such, most of the blood (about 90%) that came back from all the veins in the body to the right side of the heart had no business going to the lung. There was just not really any point in sending blood to the lung when it couldn’t pick up any oxygen there. The fetus by having a ductus arteriosus had a “pop off valve”. Since the pressure in the lung was high instead of sending blood to the lung, the 90% went from the right ventricle in the lower part of the heart to the pulmonary artery and from there across the ductus arteriosus to the aorta. The blood following this path therefore basically bypassed the lung and went from the “right” side of the heart to the “left” side that normally sends blood with oxygen to the rest of the body. The oxygen in this case came from the placenta. This fetal ciruculation is shown in the figure below.
Act II – Life on the outside
After birth the lungs fill with air containing oxygen and the resistance to blood flowing into the lung decreases which is a good thing as it allows oxygen to move from the alveolus to the capillary and back to the left side of the heart. As oxygen in the blood stream rises this usually leads to closure of the ductus arteriosus. In preterm babies though the ductus may not shut and this is what we call a Patent Ductus Arteriosus or PDA. This becomes a problem when the blood pressure in the aorta is high and the pressure in the lungs falls with breathing of air. Eventually, instead of the right to left flow of blood that occurred before, you now get blood flowing from the aorta to the pulmonary artery going to the lung and as more and more blood flows to the lungs they start to look white on chest x-rays and it gets harder and harder for your baby to breathe. The mixing is shown below.
Act III -So what do we do about it?
If we suspect that there is a PDA your doctor will order a test called an echocardiogram. This is an ultrasound of the heart and may be done by a specialist in the heart called a Cardiologist or may be done by a Neonatologist trained in doing such tests. Either way if the doctors believe the PDA is causing problems they will suggest a treatment plan to deal with it. The problems that would tend to motivate us to treat would most commonly be that your baby is needed support to help their breathing although problems related to poor blood supply to the kidneys might also lead us to treat.
The mainstays of treatment are two very common drugs and one that you may not have heard of. Indomethacin is a drug that was first used to help close PDAs and is a non steroidal anti-inflammatory (NSAID) drug that is in the same class as ibuprofen (advil) which is another drug that is used. In some centres another very common drug acetaminophen (tylenol) is employed. Most centres at this point are using one of the first two. Regardless after the medicines are given the doctors will order another echocardiogram to see if the PDA has closed and if not may repeat a course of the same medicine or choose a different one.
Act IV – What do you do if it just won’t close?
The next steps depend on how your baby is tolerating the PDA. If your infant is breathing on their own and their kidney function is working well many doctors will just observe and not offer more treatment. Babies though who are on a ventilator or are having significant issues related to their kidneys may rarely need to have a surgeon put a clip on the PDA to close it. These days this is quite rare and there are some centres that choose to not treat the PDA with medicine or surgical closure at all and just wait it out until they are gone. Almost 90% of them will close on their own if you leave them alone but again it depends on how sick your infant is in order to determine if this is reasonable.
After several reports providing reassurance to breastfeeding mothers, two very recent reports are giving me reason to pause. The Canadian Pediatric Society has been recommending breastfeeding if a mother has COVID19 with precautions in place; Breastfeeding when mothers have suspected or proven COVID-19. It would be heresy to suggest that a mother not be permitted to breastfeed her infant but what follows are two reports that at the very least may need to enter the discussion when a COVID19 positive mother gives birth and is deciding about route of feeding.
Toronto Case Report
The first report was notable not so much for breastmilk but rather that a mother with a chronic immunodeficiency and pneumonia from COVID19 had placental surfaces that tested positive on PCR for COVID19. This was the main focus of the paper Probable congenital SARS-CoV-2 infection in a neonate born to a woman with active SARS-CoV-2 infection. In the same paper though, testing of breastmilk in this mother demonstrated a positive PCR with a semi-quantitative cycle time result (there are 40 cycles of amplification of RNA in PCR testing- the further away from 40 cycles the more likely it is a true positive).
The results above were positive at 2 days and negative at 7 days. One could possibly excuse this case as an anomaly since the mother in this case not only was sick but also has chronic neutropenia but then along comes another report.
Second Research Report
This week a second report emerged that adds to the uncertainty around breastmilk. Detection of SARS-CoV-2 in human breastmilk looks at two mothers one of whom was negative on testing of breastmilk but the other unfortunately tested positive. The authors included the following timeline which is very informative.
From the timeline above you will note that in the second case the mother becomes positive at 11 days of age and the infant tests positive around the same time the milk comes back positive. The infant in this case also develops RSV which likely explains the symptoms they developed later in the course. What is concerning to me though is that in this case while the mother was COVID19 positive, she was not acutely ill. When thinking of vertical transmission this has been something that has been postulated in suspecting that those with more severe illness have higher viral loads and therefore may be capable of vertical transmission. Not the case here if the results are to be believed. Adding to the strength of the result are Ct values for SARSCoV2 N peaked at 29∙8 and 30∙4 in whole milk and skimmed milk respectively so this seems real.
How does this differ than past testing?
What intrigues me about this study in particular is that past research on transmission into breastmilk has failed to detect the virus. It could be that previous testing close to delivery was negative and that with time might the virus enter breastmilk? At eleven days I think this may be the latest testing done. In virtually all cases reported about COVID19 positives in newborns the authors have always explained the painstaking steps they took to prevent postnatal infection. I do wonder now if some of these cases may be related to a small percentage of women carrying the virus in their breastmilk. This leaves us in a tough spot. What do we tell women who are thinking of breastfeeding and have COVID19? There will need to be discussion on this but one option is to proceed with feeding accepting there may be a small risk of transmission. A second option would be to test milk but if the transmission occurs late you may miss it in hospital on initial sampling Finally it may be worth pumping and discarding milk until mothers test negative and using donor breastmilk in the meantime (or formula for those who don’t have DBM).
Regardless I think this information coming out will need to be digested and centres think about how they will approach this issue. My guess is these will not be the last reports on this.
After developing a community of over 23000 people unfortunately I had to close my Facebook site due to concerns over a hack. Not to worry as I have created a new independent site to share information daily in Neonatology. I look forward to building an audience at this site and working to continue the dialogue I have come to enjoy with all the followers.
I doubt there is a unit in the world where at least once a day a discussion ensues about whether an infant is ready to wean or come off their CPAP. For many years we have made the decision based on a variety of markers. Some people would comment on the work of breathing, others on the FiO2 or what the oxygen saturations are at the moment as we round on the patient. Our unit has been pulling oxygen histograms off the patient monitor for years now to provide a more objective measurement to determine if an infant is ready or not. What is a histogram? It is a bar graph representation of the percentage of time in a 24 hour period that an infant has spent in several different oxygen saturation ranges.
They looked at 36 babies (24 control and 12 cases) in which controls were babies who successfully weaned off CPAP when on less than or equal to 30% oxygen in the first week of life and compared them to infants who failed and had to go back on. Success was defined as remaining off CPAP for 7 consecutive days while failure was having to go back on with in 7 days of discontinuation. All infants were <1250g at birth or less then or equal to 30 weeks gestational age at delivery. Infants were enrolled prospectively in an observational case-control study. During the study goal oxygen saturations were 90-95% and oxygen histograms were monitored q6h by respiratory therapists. Importantly, during the study there was no standard approach to weaning patients off of CPAP but as per many NICUs, discontinuation occurred when FiO2 was low and there were only 1-2 events per day requiring stimulation. The authors controlled for a number of potential factors which could influence success such as GA, BW, Sex, receipt of antenatal steroids, ventilation, caffeine dose, FiO2 prior to weaning and surfactant but found no differences between groups.
What did they find though?
As you might expect there was a difference found and it was in the histograms. The infants who ultimately succeeded in coming off CPAP were better oxygenated in the 24 hours prior to coming off CPAP. Of note, the cases had a median FiO2 of 22% and the controls 21% which was not statistically different.
Looking at the above figure you can see that there were statistically significant differences in the two groups with the babies who successfully weaned off CPAP having significantly higher levels of oxygen saturation in the 95% and above ranges. The authors concluded “The optimal value of oxygen saturation achievement >95% to predict CPAP-weaning success by Youden index was 31.6% with a sensitivity of 75% and specificity of 75%.”
In other words if you have about 30% of the time spent above 95% in the 24 hours prior to coming off CPAP you have a pretty good chance of success!
Applying the information
Who doesn’t like a study that validates your own practice?! The study is really a beginning though as the study tells us that for babies that are mildly ill (as evidenced by being on room air or 22%) that you can utilize the histogram data to make decisions about when it is best to stop CPAP. What this study though examined is a particular population of small infants who were all taken off CPAP in the first week of life. Would the same principals apply to an older infant or one who is larger at birth? I would like to think so but there are many infants who are on oxygen with BPD who are also weaning off CPAP after many weeks of age. We use histograms in this population as well to guide our weaning but an important measurement that must be taken into account is the FiO2. I can really manipulate a histogram to show anything I want for a baby on oxygen. If it is better from one day to the next is it because the lungs have improved or has the average FiO2 simply been higher in the preceding 24 hours? Conversely if it is worse does the infant have atelectasis or pneumonia or has nursing been more restrictive in FiO2?
Further studies in this area need to create an objective tool that takes into account level of support and mean FiO2 when interpreting the histogram. Failure to do so would lead at times to incorrect decisions if you solely look at a bar graph. As with everything in NICU, the devil is in the details!
Phenobarbital at least where I work has been first line treatment for seizure control for as long as I can recall. We dabbled with using phenytoin and fos-phenytoin in the past but the go to tried and true has been phenobarbital for some time. The use of this drug though has not been without trepidation. Animal studies have linked phenobarbital to increases rates of cerebral apoptosis. Additionally, in a retrospective comparison of outcomes between seizures controlled with phenobarbital vs Levetiracetam, the latter came out ahead in terms of better long term developmental outcomes. This study from 2013 was entitled Adverse neurodevelopmental outcomes after exposure to phenobarbital and levetiracetam for the treatment of neonatal seizures. Purists of course would argue the need for a prospective trial and that is what we have to chat about here.
Levetiracetam vs Phenobarbital
The study in question was a multicenter randomized phase IIb trial (searches for a dose that provides biological activity with the minimal side effect profile) that compared two doses 40 mg/kg and 60 mg/kg of Levetiracetam with standard doses of phenobarbital. The study was done by Sharpe C et al and called Levetiracetam Versus Phenobarbital for Neonatal Seizures: A Randomized Controlled Trial.
In this study patients were randomized to receive levetiracetam or control phenobarbital treatment group in a 60:40 allocation ratio by using a block randomization strategy and stratified by site. The trial design is shown in the diagram below.
The study was designed to not delay institution of the accepted treatement with phenobarbital as usual first line treatment of seizures by more than 1 hour. The strength of this study was that the authors used electrographic seizures confirmed by continuous EEG monitoring. The efficacy of medication effect was blindly interpretted by two independent electrophysiologists. in other words the authors went out of their way to ensure these were real seizures and moreover that any changes to medications were decided upon after interpretation of effect by people remote from the study. The primary outcome though in comparison to the aforementioned retrospective study was a short one. In this study the primary outcome was initialy absense of seizures for 48 hours but then was changed part way through the study to 24 hours. The change was a practical one since it was noted after data collection that in many cases EEG monitoring had been stopped prior to 48 hours.
Honestly it is the results that led me to want to talk about this study. They are the exact opposite of what i thought they would be. Based on my own experience with Levitiracetam seeming like a wonder drug when it comes to seizure control I expected the results to favour it. Not the case.
To say that phenobarbital crushed the competition is an udnerstatement. Having said that the incidence of side effects were higher with phenobarbital as well. Hypotension, respiratory suppression, sedation, and requirement for pressor support, were more common. Nonetheless, this study also included patients with HIE and found even in this subgroup phenobarbital was superior. This is important information as one could speculate that earlier seizure cessation in those with anoxic injury already could be especially beneficial.
What do we do with these results?
As the authors point out this is a study of short term outcomes. In the trial about long term outcome it was clear that treatment with phenobarbital leads to worse outcome than with levitiracetam. Having said that it was a retrospective study so the next step will be to conduct long term outcome studies to see effects. This presents the possibility of an interesting conundrum. What if the newer drug is inferior to tried and true phenobarbital at controlling seizures but leads to better long term outcome? Would you consider allowing seizures to persist longer than you might otherwise want to in the short term but then be able to reassure families that the long term outlook is bettter? The side effect profile of levitiracetam is such that I think neurologists want to use it but the other possibility is that there is another newer anticonvulsant that will need to be tested as wouldn’t it be great not to have to choose either poor acute seizure control but better long term outcome vs better seizure control with concerning long term outcome? As a parent I have no doubt watching a child eize would be terrifying and you would want it to end as soon as possible but the question with phenobarbital is at what cost?