Continuous glucose monitoring in NICU may be around the corner

Continuous glucose monitoring in NICU may be around the corner

We sure do poke a lot of babies to test their blood glucose levels.  Some of these babies don’t have so much blood to spare either so checking sugars multiple times a day can drain the body of that precious blood they so need for other functions.  Taking too much can always be addressed with a blood transfusion but that as I see it may be avoidable so shouldn’t we do what we can to cut down on blood work? Those with diabetes will be familiar with a continuous glucose monitor (CGM) which is implanted in the skin and can stay in place up to 7 days.  The device does require calibration twice a day with a capillary sample to verify it is reading well but this saves a couple pokes a day for those who check four times a day.  Such a device could be useful in the NICU where those with hypoglycemia may be checked 6 or more times per day if they are either hypo or hyperglycemic.  Cutting this down to two a day would certainly we something worth striving for and if not for the reduction in blood loss then for the minimization of painful procedures.

Does it work in small babies?

A natural question for sure.Uettweller et al published Real-time continuous glucose monitoring reduces the duration of hypoglycemia episodes: a randomized trial in very low birth weight neonates. In babies with a BW < 1500g they were able to demonstrate in 43 babies (21 with traditional intermittent glucose checks vs 22 with CGM)  a  reduction in duration of hypoglycemia episodes per patient (CGM 44[10-140] min versus IGM 95[15-520] min, p<0.05). Moreover in this brief study of the first three days of life they also found a reduction in the total number of pokes per patient of 5 pokes (22 vs 16).  The numbers however are small and the duration short in only being three days so it did not provide a perfect answer as to whether this technology would work in babies from 500-750g reliably but certainly for older babies, continuous knowledge of the blood glucose in theory would allow for faster response to low sugars and as a result as evidenced by the results led to a decrease in time with a low blood glucose.

Improving on these results

Galderisi et al just published Continuous Glucose Monitoring in Very Preterm Infants: A Randomized Controlled Trial.  The study remains small at 50 and the target group ranging from 28-31 weeks (all < 1500g) but the study followed babies for a longer time frame of 7 days. This study employed an algorithm for adjustments in glucose infusion that required staff to first put data into an excel spreadsheet and then the predictive algorithm dictated whether to increase or decrease the rate of dextrose infusion.  In one arm, CGM results were unblinded and the practitioners relied on the rate of change to determine the predicted glucose 15 minutes into the future while in the blinded group the CGM was used but results were not available (retrospectively yes) so changes were made based on the usual practice of obtaining point of care results and modifying glucose infusion rates based on that result.  The primary outcome of interest here was percentage of time in the euglycemic range of 72 – 144 mg/dL (4-8 mmol/L).   Secondary outcomes were time spent hypo or hyperglycemic (mild hypoglycemia (M-HYPO) (47–71 mg/dL); severe hypoglycemia (S-HYPO) (<47 mg/dL); mild hyperglycemia (M-HYPER) (145–180 mg/dL); and severe hyperglycemia (S-HYPER) (>180 mg/dL)).  The study lasted a total of seven days allowing the use of one subcutaneous probe per patient as they can last one week after insertion.

How did the approaches compare?

As you might have expected, having a predictive model proved superior.  Overall after adjusting for sex, gestational age and weight mean time in target using the unblinded CGM was 83% [95% CI, 79%–87%] and of 71% [95% CI, 67%–76%] in B-CGM [P < .001]).

As for secondary outcomes one can see that the time spent in the hypo/hyper areas was much less as a percentage of time than using traditional methods of intermittent sampling.  One interesting outcome was that the total number of samples used over the study was an average of 2.4 tests per day in the unblinded group vs 2.59 per day in the intermittent sampling group which although statistically different does not seem to have much clinical impact.

A few questions remain

The idea of using an implanted CGM for infants in the NICU is one that excites me.  The lack of a reduction in pokes in a meaningful way is disappointing but I can’t help but wonder if the effect was different whether you were in the first or second half of the week.  What if glycemic control in these 29-31 week infants had stabilized by 2-3 days such that you only needed one or two glucose checks in the last half of the week per day?  The CGM requires calibration twice daily with POC samples so the lack of a difference my be due to those issues.  Future, calibration is rumoured to be possible with one sample so that may change.

There is no disputing though that the use of the predictive algorithm made a difference in terms of avoidance of hypo/hyperglycemic episodes.  A larger study would be needed to look at whether this impacts harm that may be associated with such variability such as IVH or ROP but it certainly is promising.  The biggest issue here is that I cannot see people manually inputting glucose readings on the CGM into an excel sheet in everyday practice.  For this to become widely adopted, a simplified approach to prediction would be required or even better a feedback loop whereby data from the CGM would relay to the infusion pump and rates adjusted automatically (with manual override available).

The use of CGM is coming though and I can’t help but think in the larger babies born to mothers with diabetes there would be a real heal sparing effect with these.  Might this be the next study?

 

 

A Cure For Neonatal Hypoglycemia

A Cure For Neonatal Hypoglycemia

I have probably received more requests for our glucose gel protocol than any other question since I started writing on this blog.  Dextrose gel has been used more and more often for treatment of hypoglycemia such that it is now a key strategy in the management of low blood sugar in ours and many other institutions.  If you are interested in the past analyses of the supporting trials they can be found in these posts; Glucose gel For Managing Hypoglycemia. Can We Afford Not To Use It? and Dextrose gel for hypoglycemia: Safe in the long run?  As you can tell from these posts I am a fan of dextrose gel and eagerly await our own analysis of the impact of using gel on NICU admission rates for one!

But What If You Could Prevent Hypoglycemia Rather Than Treating It?

This is the question that the same group who has conducted the other trials sought to answer in their dose finding study entitled Prophylactic Oral Dextrose Gel for Newborn Babies at Risk of Neonatal Hypoglycaemia: A Randomised Controlled Dose-Finding Trial (the Pre-hPOD Study).  I suppose it was only a matter of time that someone asked the question; “What if we prophylactically gave at risk babies dextrose gel?  Could we prevent them from becoming hypoglycemic and reduce admissions and improve breastfeeding rates as has been seen with treatment of established hypoglycemia?”  That is what they went out and did.  The group selected at risk patients such as those born to mothers with any type of diabetes, late preterm infants, SGA and others typically classified as being at risk but who did not require NICU admission at 1 hour of age when treatment was provided.  The primary outcome was hypoglcyemia (<2.6 mmol/L) in the first 48 hours.  Secondary outcomes included NICU admissions, breastfeeding rates in hospital and after discharge as well as formula intake at various time points.

The study sought really to serve as a pilot whose goal was to determine when compared to placebo whether several different regimens could prevent development of hypoglycemia.  The groups were (with the first dose in each case given at 1 hour of age):

  1. Single dose of 40% dextrose gel – 0.5 mL/kg
  2. Single dose of 40% dextrose gel – 1 ml/kg
  3. Four doses of 0.5 mL/kg given every three hours with breastfeeding
  4. A single dose of 1 mL/kg then 3 X 0.5 mL/kg given q3h before each breastfeed.

In total 412 patients were randomized into 8 different groups (4 treatment and 4 placebo).

As The Saying Goes, Less Is More

odds-of-hypoglycemia

The only dose of dextrose that reduced the risk of hypoglycemia in the first 48 hours was 0.5 mL/kg which provides 200 mg/kg of dextrose which is the same as a bolus of IV dextrose when giving 2 mL/kg of D10W.  Curiously using a higher dose or using multiple doses had no effect on reducing the risk.  Based on a difference of 14% between placebo and this group you would need to treat roughly 7 patients with dextrose gel once to prevent one episode of hypoglycemia.  Also worth noting is that admission to NICU was no different but if one restricted the reason for admission to hypoglycemia the difference was significant (13% vs 2% risk; p = 0.04).  What was not seen here was a difference in rates of breastfeeding and much effect on use of formula.

Why Might These Results Have Occurred?

Insulin levels were not measured in this study but I truly wonder if the reason for hypoglycemia in the other groups may have been transient hyperinsulinemia from essentially receiving either a very large load of glucose (1 mL/kg groups) or effectively 4 boluses of glucose in the first 12 hours of feeding.  Rebound hypoglycemia from IV boluses is a known phenomenon as insulin levels surge to deal with the large dextrose load and I can’t help but wonder if that is the reason that all but the single dose regimen had an effect.  It is also worth commenting that with so many secondary outcomes in this study the p values needed to reach significance are likely much smaller than 0.05 so I would take the reduction in NICU admissions for hypoglycemia with a grain of salt although at least the trend is encouraging.

I wouldn’t change my practice yet and the authors do acknowledge in the article that a much larger study is now being done using the single dose of 0.5 mL/kg to look at outcomes and until that is published I don’t think a practice change is in order.  What this study does reinforce though is that providing multiple doses of dextrose gel may yield diminishing returns.  While the goal here was prophylaxis, I can’t help but think about the patients who are symptomatic and receive two or three gels and still wind up with an IV.  Could it be the same rebound hypoglycemia at play?

We also have to acknowledge that even if this is an effective preventative strategy, is it in the best interests of the babies to all receive such treatment when at least in 6 babies they wouldn’t have needed any?  Could such treatment simply be reserved as has been done for those who develop hypoglycemia?  Those who question the safety of the ingredients such as dyes that are found in the product may want some long term safety data before this becomes routine in at risk babies but it won’t surprise me if such strategies become commonplace pending the results of the larger trial on the way.

Dextrose gel for hypoglycemia: Safe in the long run?

Dextrose gel for hypoglycemia: Safe in the long run?

The Sugar Babies trial was the subject of a post earlier this year as the largest trial to date examining the effects of using dextrose gel to treat hypoglycemia.  For an analysis of the use of gel in this situation please see the original post Glucose Gel For Neonatal Hypoglycemia: Can We Afford Not To Use It?

In summary though, the trial involved 118 infants who received 40% dextrose gel vs 119 who received a placebo gel. All of the infants in this study were selected based on risk factors for hypoglycemia (IDM, IUGR, LBW, LGA, near term) and were all 35 weeks or greater. Each infant had to be less than 48 hours of age when enrolled. Infants received 0.5 mL/kg 40% dextrose gel (200 mg/kg). This was designed to deliver the same amount of sugar as would be given with a D10W bolus of 2 mL/kg. In order to receive the treatment the blood glucose had to be < 2.6 mmol/L so equivalent to our own standards in Canada and the US. Treatment failure, which was the primary outcome was defined as a blood glucose < 2.6 mmol/L despite two treatments with gel.  The studies most important findings were a reduction in NICU admission and greater breastfeeding rates at 2 weeks of age (due to avoidance of formula feeding to keep the glucose stable).

But Is It Safe?

With any new strategy though, questions arise regarding safety of the product in the long term.  As one reader commented after the original post, could the red dye be harmful in some way or perhaps some other constituent of the gel?  The authors of the original study have now published the follow-up paper entitled Outcome at 2 Years after Dextrose Gel Treatment for Neonatal Hypoglycemia: Follow-Up of a Randomized Trial.  The findings were a little concerning to me in that there was a high rate of neurosensory impairment in both arms (sham and glucose gel) with the following findings.  None of the differences were significant however.

Workbook1 copy

Looking at these results you could be dismayed that the glucose gel did not show any benefit compared to standard therapies for hypoglycemia but if you look at the original study one could equally ask why would we have expected it to?

Should The Results Surprise Us?

All of the newborns in either arm had an episode of hypoglycemia recorded in order to qualify for entry into the study.  The glucose gel was effective compared to placebo in reducing admissions and increasing breastfeeding rates (which one might think would improve outcomes) but we don’t know what the drop off rate in breastfeeding was after 2 weeks. What I can say though is that if there were significant adverse side effects with the glucose gel I would have expected to see some differences in outcome favouring the placebo group which did not occur.

An additional issue is we know that the placebo group had more treatment failures meaning they would have had more newborns in the original study with a second low glucose.  Would this favour a worse outcome in the placebo group?  If so does the equivalence in groups suggest that the dextrose gel might worsen outcomes?

Unfortunately, what this study is really missing is some indication of how low and how long the blood sugars remained under 2.6 mmol/L in both arms of the study.  We know the mean low glucoses were similar but what about duration and range? While the rates of mild, moderate and severe impairment are the same we don’t know how severe the hypoglycemia was which if unbalanced between the groups could actually lead to very different conclusions here.  For example, let’s say the glucose gel group had an over representation of infants with 3 or more episodes of hypoglycemia compared to the placebo arm.  The fact that the outcomes are equivalent would suggest that the glucose gel is in fact protective.

What Can We Say?

I suspect that while glucose gel is effective, to truly assess harm across many different aspects of development we will need larger sample sizes.  We also have to take the results of this study with a grain of salt as so many that have come before it have seen outcomes at school age reveal different findings than when assessed at 2 years of age as in this study. From my standpoint though I will continue to advocate for the use of glucose gel as the reduction in NICU admissions and enhancement of breastfeeding rates especially if sustained are well worth the efforts to implement this strategy if you aren’t using it already.

 

Glucose gel For Managing Hypoglycemia.  Can We Afford Not To Use It?

Glucose gel For Managing Hypoglycemia. Can We Afford Not To Use It?

I was inspired to write this post after sharing a review of an article from 2013 on my Facebook page. The article pertained to the use of a 40% dextrose gel to treat neonatal hypoglycemia

We have been using this glucose gel in our population for nearly two years and have noted great success in avoiding admissions for hypoglycemia, however this remains unpublished. I was surprised to hear how many places have yet to adopt such treatment and based on the comments on the page it would appear that adoption of such gels are on their way in some locations. The popularity of this post though inspired me to write this piece, which summarizes the evidence for the use of gels in the neonate.

What is the Evidence For Using Glucose Gels

Surprisingly there is actually very little in the way of publications on the topic. In 1992, there was a small randomized trial which failed to show a benefit in terms of variability of one serum glucose to the next but it did not look at other functional outcomes such as impact on maternal infant separation or success in breast-feeding.

The next study is in fact the one mentioned in the article that was posted on Facebook called the Sugar Babies study. Dr. Harris in this case studied 118 infants who received 40% dextrose gel vs 119 who received a placebo gel. All of the infants in this study were selected based on risk factors for hypoglycemia (IDM, IUGR, LBW, LGA, near term) and were all 35 weeks or greater. Each infant had to be less than 48 hours of age when enrolled. Infants received 0.5 mL/kg 40% dextrose gel (200 mg/kg). This was designed to deliver the same amount of sugar as would be given with a D10W bolus of 2 mL/kg. In order to receive the treatment the blood glucose had to be < 2.6 mmol/L so equivalent to our own standards in Canada and the US. Treatment failure, which was the primary outcome was defined as a blood glucose < 2.6 mmol/L despite two treatments with gel. The significant findings were quite interesting and are shown in the table below.

Finding Dextrose Placebo
Treatment Failure 14% 24%
Admission to NICU 14% 25%
# formula feeds (median) 7 10
Formula fed at 2 weeks 4% 13%

What was not found to be significant and in and of itself is a very important finding is a higher incidence of rebound hypoglycemia in the dextrose gel group. This was a potential concern as provision of dextrose in theory could cause a spike in insulin secretion thereby dramatically lowering the blood glucose but thankfully this was not observed.

Dextrose Gel Improves Breastfeeding Rates

These results I believe speak for themselves but it is extremely important to highlight the benefit here. The use of the dextrose gel was also able to enhance success at breastfeeding rates. This was accomplished in all likelihood by a reduction in admission to NICU and less reliance on formula to achieve satisfactory blood glucose. As these infants were all less than 48 hours old it is safe to assume that in many cases the mother’s milk had not yet come in so if the glucose measured was low, health care providers were more likely to intervene with an offering of formula.  It is worth noting that while this is the only significant study in the field there is a letter to the editor in which another author describes the use of a sublingual sugar powder for treating the same, which was met with similar success. There is no actual peer-reviewed study to examine however so we will leave it as simply an interesting point.

New Study on The Way

If these results leave you still being skeptical you may be pleased to hear there is a very large study (2129 babies needed) beginning enrolment in New Zealand with the primary outcome of admission to the NICU.  This prospective RCT will hopefully put to rest any questions about this treatment that have delayed implementation in many units.

As a final thought regarding the Sugar Babies study, one of the differences that came close to reaching statistical significance was the rate of IV insertions for dextrose. In the dextrose gel group the rate was 7% vs 14% in the placebo. With a p value of 0.09 it suggests that with a larger study size a difference may have been reached. The idea that we have the option of using a therapy that can decrease formula use, improve breastfeeding rates including those found post discharge and lastly decrease the poking of infants for IV dextrose is a goal well worth pursuing. Is this enough evidence for you? I would encourage all who read this piece to ask their NICU the question of whether a trial of dextrose gel is worthwhile. It could make a big difference far beyond treating a number.