Capnography or colorimetric detection of CO2 in the delivery suite.  What to choose?

Capnography or colorimetric detection of CO2 in the delivery suite. What to choose?

For almost a decade now confirmation of intubation is to be done using detection of exhaled CO2. The 7th Edition of NRP has the following to say about confirmation of ETT placement “The primary methods of confirming endotracheal tube placement within the trachea are detecting exhaled CO2 and a rapidly rising heart rate.” They further acknowledge that there are two options for determining the presence of CO2 “There are 2 types of CO2 detectors available. Colorimetric devices change color in the presence of CO2. These are the most commonly used devices in the delivery room. Capnographs are electronic monitors that display the CO2 concentration with each breath.” The NRP program stops short of recommending one versus the other. I don’t have access to the costs of the colorimetric detectors but I would imagine they are MUCH cheaper than the equipment and sensors required to perform capnography using the NM3 monitor as an example. The real question though is if capnography is truly better and might change practice and create a safer resuscitation, is it the way to go?

Fast but not fast enough?

So we have a direct comparison to look at. Hunt KA st al published Detection of exhaled carbon dioxide following intubation during resuscitation at delivery this month. They started from the standpoint of knowing from the manufacturer of the Pedicap that it takes a partial pressure of CO2 of 4 mm Hg to begin seeing a colour change from purple to yellow but only when the CO2 reaches 15 mm Hg do you see a consistent colour change with that device. The capnograph from the NM3 monitor on the other hand is quantitative so is able to accurately display when those two thresholds are reached. This allowed the group to compare how long it took to see the first colour change compared to any detection of CO2 and then at the 4 and 15 mm Hg levels to see which is the quicker method of detection. It is an interesting question as what would happen if you were in a resuscitation and the person intubates and swears that they are in but there is no colour change for 5, 10 or 15 seconds or longer? At what point do you pull the ETT? Compare that with a quantitative method in which there is CO2 present but it is lower than 4. Would you leave the tube in and use more pressure (either PIP/PEEP or both?)? Before looking at the results, it will not shock you that ANY CO2 should be detected faster than two thresholds but does it make a difference to your resuscitation?

The Head to Head Comparison

The study was done retrospectively for 64 infants with a confirmed intubation using the NM3 monitor and capnography.  Notably the centre did not use a colorimetric detector as a comparison group but rather relied on the manufacturers data indicating the 4 and 15 mm Hg thresholds for colour changes.  The mean age of patients intubated was 27 weeks with a range of 23 – 34 weeks.  The results I believe show something quite interesting and informative.

Median time secs (range)
Earliest CO2 detection 3.7 (0 – 44s)
4 mm Hg 5.3 (0 – 727)
15 mm Hg 8.1 (0 – 727)

I wouldn’t worry too much about a difference of 1.6 seconds to start getting a colour change but it is the range that has me a little worried.  The vast majority of the patients demonstrated a level of 4 or 15 mm Hg within 50 seconds although many were found to take 25-50 seconds.  When compared to a highest level of 44 seconds in the first detection of CO2 group it leads one to scratch their head.  How many times have you been in a resuscitation and with no CO2 change you keep the ETT in past 25 seconds?  Looking closer at the patients, there were 12 patients that took more than 30 seconds to reach a threshold of 4 mm Hg.  All but one of the patients had a heart rate in between 60-85.  Additionally there was an inverse relationship found between gestational age and time to detection.  In other words, the smallest of the babies in the study took the longest to establish the threshold of 4 and 15 mm Hg.

Putting it into context?

What this study tells me is that the most fragile of infants may take the longest time to register a colour change using the colorimetric devices.  It may well be that these infants take longer to open up their pulmonary vasculature and deliver CO2 to the alveoli.  As well these same infants may take longer to open the lung and exhale the CO2.  I suppose I worry that when a resuscitation is not going well and an infant at 25 weeks is bradycardic and being given PPV through an ETT without colour change, are they really not intubated?  In our own centre we use capnometry in these infants (looks for a wave form of CO2) which may be the best option if you are looking to avoid purchasing equipment for quantitative CO2 measurements.  I do worry though that in places where the colorimetric devices are used for all there will be patients who are extubated due to the thought that they in fact have an esophageal intubation when the truth is they just need time to get the CO2 high enough to register a change in colour.

Anyways, this is food for thought and a chance to look at your own practice and see if it is in need of a tweak…

Is skin to skin care truly good for the developing brain?

Is skin to skin care truly good for the developing brain?

Skin to skin care or kangaroo care is all the rage and I am the first one to offer my support for it.  Questions persist though as to whether from a physiological standpoint, babies are more stable in an isolette in a quiet environment or out in the open on their mother or father’s chests. Bornhorst et al expressed caution in their study Skin-to-skin (kangaroo) care, respiratory control, and thermoregulation.  In a surprising finding, babies with an average gestational age of 29 weeks were monitored for a number of physiological parameters and found to have more frequent apnea and higher heart rates than when in an isolette.  The study was small though and while there were statistical differences in these parameters they may not have had much clinical significance (1.5 to 2.8 per hour for apnea, bradycardia or desaturation events).  Furthermore, does an increase in such events translate into any changes in cerebral oxygenation that might in turn have implications for later development?  Tough to say based on a study of this magnitude but it certainly does raise some eyebrows.

What if we could look at cerebral oxygenation?

As you might have guessed, that is exactly what has been done by Lorenz L et al in their recent paper Cerebral oxygenation during skin-to-skin care in preterm infants not receiving respiratory support.The goal of this study was to look at 40 preterm infants without any respiratory distress and determine whether cerebral oxygenation (rStO2)was better in their isolette or in skin to skin care (SSC).  They allowed each infant to serve as their own control by have three 90 minute periods each including the first thirty minutes as a washout period.  Each infant started their monitoring in the isolette then went to SSC then back to the isolette.  The primary outcome the power calculation was based on was the difference in rStO2 between SSC and in the isolette.  Secondary measures looked at such outcomes as HR, O2 sat, active and quiet sleep percentages, bradycardic events as lastly periods of cerebral hypoxia or hyperoxia.  Normal cerebral oxygenation was defined as being between 55 to 85%.

Surprising results?

Perhaps its the start of a trend but again the results were a bit surprising showing a better rStO2 when in the isolette (−1.3 (−2.2 to −0.4)%, p<0.01).  Other results are summarized in the table below:

Mean difference in outcomes
Variable SSC Isolette Difference in mean p
rStO2 73.6 74.8 -1.3 <0.01
SpO2 (median) 97 97 -1.1 0.02
HR 161 156 5 <0.01
% time in quiet sleep 58.6 34.6 24 <0.01

No differences were seen in bradycardic events, apnea, cerebral hypoexmia or hyperoxemia.  The authors found that SSC periods in fact failed the “non-inferiority” testing indicating that from a rStO2 standpoint, babies were more stable when not doing SSC!  Taking a closer look though one could argue that even if this is true does it really matter?  What is the impact on a growing preterm infant if their cerebral oxygenation is 1.3 percentage points on average lower during SSC or if their HR is 5 beats per minute faster?  I can’t help but think that this is an example of statistical significance without clinical significance.  Nonetheless, if there isn’t a superiority of these parameters it does leave one asking “should we keep at it?”

Benefits of skin to skin care

Important outcomes such as reductions in mortality and improved breastfeeding rates cannot be ignored or the positive effects on family bonding that ensue. Some will argue though that the impacts on mortality certainly may be relevant in developing countries where resources are scarce but would we see the same benefits in developed nations.  The authors did find a difference though in this study that I think benefits developing preterm infants across the board no matter which country you are in.  That benefit is that of Quiet Sleep (QS).  As preterm infants develop they tend to spend more time in QS compared to active sleep  (AS).  From Doussard- Roossevelt J, “Quiet sleep consists of periods of quiescence with regular respiration and heart rate, and synchronous EEG patterns. Active sleep consists of periods of movement with irregular respiration and heart rate, and desynchronous EEG patterns.”  In the above table one sees that the percentage of time in QS was significantly increased compared to AS when in SSC.  This is important as neurodevelopment is thought to advance during periods of QS as preterm infants age.

There may be little difference favouring less oxygen extraction during isolette times but maybe that isn’t such a good thing?  Could it be that the small statistical difference in oxygen extraction is because the brain is more active in laying down tracks and making connections?  Totally speculative on my part but all that extra quiet sleep has got to be good for something.

To answer the question of this post in the title I think the answer is a resounding yes for the more stable infant.  What we don’t know at the moment except from anecdotal reports of babies doing better in SSC when really sick is whether on average critically ill babies will be better off in SSC.  I suspect the answer is that some will and some won’t.  While we like to keep things simple and have a one size fits all answer for most of our questions in the NICU, this one may not be so simple.  For now I think we keep promoting SSC for even our sick patients but need to be honest with ourselves and when a patient just isn’t ready for the handling admit it and try again when more stable.  For the more stable patient though I think giving more time for neurons to find other neurons and make new connections is a good thing to pursue!

Hydrocortisone after birth may benefit the smallest preemies the most!

Hydrocortisone after birth may benefit the smallest preemies the most!

This must be one of my favourite topics as I have been following the story of early hydrocortisone to reduce BPD for quite some time. It becomes even more enticing when I have met the authors of the studies previously  and can see how passionate they are about the possibilities. The PREMILOC study was covered on my site twice now, with the first post being A Shocking Change in Position. Postnatal steroids for ALL microprems? and the second reviewing the 22 month outcome afterwards /2017/05/07/early-hydrocortisone-short-term-gain-without-long-term-pain/.

The intervention here was that within 24 hours of birth babies born between 24-27 weeks gestational age were randomized to receive placebo or hydrocortisone 1 mg/kg/d divided q12h for one week followed by 0.5 mg/kg/d for three days. The primary outcome was rate of survival without BPD at 36 weeks PMA. The finding was a positive one with a 9% reduction in this outcome with the use of this strategy. Following these results were the two year follow-up which reported no evidence of harm but the planned analysis by gestational age groupings of 24-25 and 26-27 weeks was not reported at that time but it has just been released this month.

Is there a benefit?

Of the original cohort the authors are to be commended here as they were able to follow-up 93% of all infants studied at a mean age of 22 months. The methods of assessing their neurological status have been discussed previously but essentially comprised standardized questionnaires for parents, assessment tools and physical examinations.

Let’s start off with what they didn’t find. There was no difference between those who received placebo vs hydrocortisone in the 26-27 week group but where it perhaps matters most there was. The infants born at 24-25 weeks are certainly some of our highest risk infants in the NICU. It is in this group that the use of hydrocortisone translated into a statistically significant reduction in the rate of neurodevelopmental impairment. The Global Neurological Assessement scores demonstrated a significant improvement in the hydrocortisone group with a p value of 0.02. Specifically moderate to severe disability was noted in 18% compared to 2% in the group receiving hydrocortisone.They did not find a difference in the neurological exam but that may reflect the lack of physical abnormalities with cognitive deficit remaining.  It could also be explained perhaps by the physical examination not being sensitive enough to capture subtle differences.

 

Why might this be?

Adding an anti-inflammatory agent into the early phase of a preemies life might spare the brain from white matter damage. Inflammation is well known to inflict injury upon the developing brain and other organs (think BPD, ROP) so dampening these factors in the first ten days of life could bring about such results via a mechanism such as that. When you look at the original findings of the study though, a couple other factors also pop up that likely contribute to these findings as well. Infants in the hydrocortisone group had a statistical reduction in the rate of BPD and PDA ligations. Both of these outcomes have been independently linked to adverse neurodevelopmental outcome so it stands to reason that reducing each of these outcomes in the most vulnerable infants could have a benefit.

In fact when you add everything up, is there much reason not to try this approach? Ten days of hydrocortisone has now been shown to reduce BPD, decrease PDA ligations and importantly in the most vulnerable of our infants improve their developmental outcome. I think with this information at our fingertips it becomes increasingly difficult to ignore this approach. Do I think this will become adopted widely? I suspect there will be those who take the Cochrane approach to this and will ask for more well designed RCTs to be done in order to replicate these results or at least confirm a direction of effect which can then be studied as part of a systematic review. There will be those early adopters though who may well take this on. It will be interesting to see as these centres in turn report their before and after comparisons in the literature what the real world impact of this approach might be.

Stay tuned as I am sure this is not the last we will hear on this topic!

An Old Drug Finds A New  Home In The Treatment of BPD.

An Old Drug Finds A New Home In The Treatment of BPD.

What is old is new again as the saying goes.  I continue to hope that at some point in my lifetime a “cure” will be found for BPD and is likely to centre around preventing the disease from occurring.  Will it be the artificial placenta that will allow this feat to be accomplished or something else?  Until that day we unfortunately are stuck with having to treat the condition once it is developing and hope that we can minimize the damage.  When one thinks of treating BPD we typically think of postnatal steroids.  Although the risk of adverse neurodevelopmental outcome is reduced with more modern approaches to use, such as with the DART protocol,most practitioners would prefer to avoid using them at all if possible.  We know from previous research that a significant contributor to the development of BPD is inflammation.  As science advanced, the specific culprits for this inflammatory cascade were identified and leukotrienes in particular were identified in tracheal lavage fluid from infants with severe lung disease.  The question then arises as to whether or not one could ameliorate the risk of severe lung disease by halting at least a component of the inflammatory cascade leading to lung damage.

Leukotriene Antagonists

In our unit, we have tried using the drug monteleukast, an inhibitor of leukotrienes in several patients.  With a small sample it is difficult to determine exactly whether this has had the desired effect but in general has been utilized when “all hope is lost”.  The patient has severe disease already and is stuck on high frequency ventilation and may have already had a trial of postnatal steroids.  It really is surprising that with the identification of leukotriene involvement over twenty years ago it took a team in 2014 to publish the only clinical paper on this topic.  A German team published Leukotriene receptor blockade as a life-saving treatment in severe bronchopulmonary dysplasia.in 2014 and to date as far as I can see remains the only paper using this strategy. Given that we are all looking for ways to reduce BPD and this is the only such paper out there I thought you might want to see what they found.  Would this be worth trying in your own unit?  Well, read on and see what you think!

Who was included?

This study had an unusual design that will no doubt make statistical purists cringe but here is what they did.  The target population for the intervention were patients with “life threatening BPD”.  That is, in the opinion of the attending Neonatologist the patient had a greater than 50% likelihood of dying and also had to meet the following criteria; born at < 32 weeks GA, <1500g and had to be ventilated at 28 days.  The authors sought a blinded RCT design but the Research Ethics Board refused due to the risk of the drug being low and the patients having such a high likelihood of death.  The argument in essence was if the patients were likely to die and this drug might benefit them it was unethical to deny them the drug.  The authors attempted to enroll all eligible patients but wound up with 11 treated and 11 controls.  The controls were patients either with a contraindication to the drug or were parents who consented to be included in the study as controls but didn’t want the drug.  Therapy was started for all between 28 – 45 days of age and continued for a wide range of durations (111+/-53 days in the study group).  Lastly, the authors derived a score of illness severity that was used empirically:

PSC = FiO2 X support + medications

– support was equal to 2.5 for a ventilator. 1.5 for CPAP and 1 for nasal cannulae or an oxygen hood

– medications were equal to 0.2 for steroids, 0.1 for diruetics or inhaled steroids, 0.05 for methylxanthines or intermittent diruetics.

Did it make a difference?

The study was very small and each patient who received the medication was matched with one that did not receive treatment.  Matching was based on GA, BW and the PSC with matching done less than 48 hours after enrollment in an attempt to match the severity of illness most importantly.

First off survival in the groups were notably different.  A marked improvement in outcome was noted in the two groups.  Of the deaths in the control group, the causes were all pulmonary and cardiac failure, although three patients died with a diagnosis of systemic inflammatory response syndrome.  That is quite interesting given that monteleukast is an anti-inflammatory medication and none of the patients in the treatment arm experienced this diagnosis.

The second point of interest is the trend in the illness severity score over time.  The time points in the figure are time 1 (start of study), time 2 (4 weeks of treatment), time 3 (end of treatment).  These patients improved much more over time than the ones who did not receive treatment.

The Grain of Salt

As exciting as the results are, we need to acknowledge a couple things.  The study is small and with that the risk of the results appearing to be real but in actual fact there being no effect is not minimal.  As the authors knew who was receiving monteleukast it is possible that they treated the kids differently in the unit.  If you believed that the medication would work or moreover wanted it to work, did you pay more attention on rounds and during a 24 hour period to those infants?  Did the babies get more blood gases and tighter control of ventilation with less damage to the lungs over time?  There are many reasons why these patients could have been different including earlier attempts to extubate.  The fact is though the PSC scores do show that the babies indeed improved more over time so I wouldn’t write it off entirely that they did in fact benefit.  The diagnosis of SIRS is a tough one to make in a newborn and I worry a little that knowing the babies didn’t receive an anti-inflammatory drug they were “given” that diagnosis.

Would I use it in spite of these faults? Yes.  We have used it in such cases but I can’t say for sure that it has worked.  If it does, the effect is not immediate and we are left once we start it not knowing how long to treat.  As the authors here say though, the therapeutic risk is low with a possibly large benefit.  I doubt it is harmful so the question we are left asking is whether it is right for you to try in your unit?  As always perhaps a larger study will be done to look at this again with a blinded RCT structure as the believers won’t show up I suspect without one!

Maybe we shouldn’t be in such a rush to stop caffeine.

Maybe we shouldn’t be in such a rush to stop caffeine.

Given that many preterm infants as they near term equivalent age are ready to go home it is common practice to discontinue caffeine sometime between 33-34 weeks PMA.  We do this as we try to time the readiness for discharge in terms of feeding, to the desire to see how infants fare off caffeine.  In general, most units I believe try to send babies home without caffeine so we do our best to judge the right timing in stopping this medication.  After a period of 5-7 days we generally declare the infant safe to be off caffeine and then move on to other issues preventing them from going home to their families.  This strategy generally works well for those infants who are born at later gestations but as Rhein LM et al demonstrated in their paper Effects of caffeine on intermittent hypoxia in infants born prematurely: a randomized clinical trial., after caffeine is stopped, the number of intermittent hypoxic (IH) events are not trivial between 35-39 weeks.  Caffeine it would seem may still offer some benefit to those infants who seem otherwise ready to discontinue the medication.  What the authors noted in this randomized controlled trial was that the difference caffeine made when continued past 34 weeks was limited to reducing these IH events only from 35-36 weeks but the effect didn’t last past that.  Why might that have been?  Well it could be that the babies after 36 weeks don’t have enough events to really show a difference or it could be that the dose of caffeine isn’t enough by that point.  The latter may well be the case as the metabolism of caffeine ramps up during later gestations and changes from a half life greater than a day in the smallest infants to many hours closer to term.  Maybe the caffeine just clears faster?

Follow-up Study attempts to answer that very question.

Recognizing the possibility that levels of caffeine were falling too low after 36 weeks the authors of the previous study begun anew to ask the same question but this time looking at caffeine levels in saliva to ensure that sufficient levels were obtained to demonstrate a difference in the outcome of frequency of IH.  In this study, they compared the original cohort of patients who did not receive caffeine after planned discontinuation (N=53) to 27 infants who were randomized to one of two caffeine treatments once the decision to stop caffeine was made.  Until 36 weeks PMA each patient was given a standard 10 mg/kg of caffeine case and then randomized to two different strategies.  The two dosing strategies were 14 mg/kg of caffeine citrate (equals 7 mg/kg of caffeine base) vs 20 mg/kg (10 mg/kg caffeine base) which both started once the patient reached 36 weeks in anticipation of increased clearance.  Salivary caffeine levels were measured just prior to stopping the usual dose of caffeine and then one week after starting 10 mg/kg dosing and then at 37 and 38 weeks respectively on the higher dosing.  Adequate serum levels are understood to be > 20 mcg/ml and salivary and plasma concentrations have been shown to have a high level of agreement previously so salivary measurement seems like a good approach.  Given that it was a small study it is work noting that the average age of the group that did not receive caffeine was 29.1 weeks compared to the caffeine groups at 27.9 weeks.  This becomes important in the context of the results in that earlier gestational age patients would be expected to have more apnea which is not what was observed suggesting a beneficial effect of caffeine even at this later gestational age.  Each patient was to be monitored with an oximeter until 40 weeks as per unit guidelines.

So does caffeine make a difference once term gestation is reached?

A total of 32 infants were enrolled with 12 infants receiving the 14 mg/kg and 14 the 20 mg/kg dosing.  All infants irrespective of assigned group had caffeine concentrations above 20 mcg/mL ensuring that a therapeutic dose had been received.  The intent had been to look at babies out to 40 weeks with pulse oximetry even when discharged but owing to drop off in compliance with monitoring for a minimum of 10 hours per PMA week the analysis was restricted to infants at 37 and 38 weeks which still meant extension past 36 weeks as had been looked at already in the previous study.  The design of this study then compared infants receiving known therapeutic dosing at this GA range with a previous cohort from the last study that did not receive caffeine after clinicians had determined it was no longer needed.

The outcomes here were measured in seconds per 24 hours of intermittent hypoxia (An IH event was defined as a decrease in SaO2 by ⩾ 10% from baseline and lasting for ⩾5 s).  For graphical purposes the authors chose to display the number of seconds oxygen saturation fell below 90% per day and grouped the two caffeine patients together given that the salivary levels in both were therapeutic.  As shown a significant difference in events was seen at all gestational ages.

Putting it into context

The scale used I find interesting and I can’t help but wonder if it was done intentionally to provide impact.  The outcome here is measured in seconds and when you are speaking about a mean of 1200 vs 600 seconds it sounds very dramatic but changing that into minutes you are talking about 20 vs 10 minutes a day.  Even allowing for the interquartile ranges it really is not more than 50 minutes of saturation less than 90% at 36 weeks.  The difference of course as you increase in gestation becomes less as well.  When looking at the amount of time spent under 80% for the groups at the three different gestational ages there is still a difference but the amount of time at 36, 37 and 38 weeks was 229, 118 and 84 seconds respectively without caffeine (about 4, 2 and 1 minute per day respectively) vs 83, 41, and 22 seconds in the caffeine groups. I can’t help but think this is a case of statistical significance with questionable clinical significance.  The authors don’t indicate that any patients were readmitted with “blue spells” who were being monitored at home which then leaves the sole question in my mind being “Do these brief periods of hypoxemia matter?”  In the absence of a long-term follow-up study I would have to say I don’t know but while I have always been a fan of caffeine I am just not sure.

Should we be in a rush to stop caffeine?  Well, given that the long term results of the CAP study suggest the drug is safe in the preterm population I would suggest there is no reason to be concerned about continuing caffeine a little longer. If the goal is getting patients home and discharging on caffeine is something you are comfortable with then continuing past 35 weeks is something that may have clinical impact.  At the very least I remain comfortable in my own practice of not being in a rush to stop this medication and on occasion sending a patient home with it as well.