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If A Little Caffeine Is Good Is A Lot Better?

If A Little Caffeine Is Good Is A Lot Better?

Caffeine seems to be good for preterm infants.  We know that it reduces the frequency of apnea in the this population and moreover facilitates weaning off the ventilator in a shorter time frame than if one never received it at all.  The earlier you give it also seems to make a difference as shown in the Cochrane review on prophylactic caffeine. When given in such a fashion the chances of successful extubation increase. Less time on the ventilator not surprisingly leads to less chronic lung disease which is also a good thing.

I have written about caffeine more than once though so why is this post different?  The question now seems to be how much caffeine is enough to get the best outcomes for our infants.  Last month I wrote about the fact that as the half life of caffeine in the growing preterm infant shortens, our strategy in the NICU might be to change the dosing of caffeine as the patient ages.  Some time ago though I wrote about the use of higher doses of caffeine and in the study analyzed warned that there had been a finding of increased cerebellar hemorrhage in the group randomized to receive the higher dosing.  I don’t know about where you work but we are starting to see a trend towards using higher caffeine base dosing above 5 mg/kg/d.  Essentially, we are at times “titrating to effect” with dosing being as high as 8-10 mg/kg/d of caffeine base.

Does it work to improve meaningful outcomes?

This month Vliegenthart R et al published a systematic review of all RCTs that compared a high vs low dosing strategy for caffeine in infants under 32 weeks at birth; High versus standard dose caffeine for apnoea: a systematic review. All told there were 6 studies that met the criteria for inclusion.  Low dosing (all in caffeine base) was considered to be 5- 15 mg/kg with a maintenance dose of 2.5 mg/kg to 5 mg/kg.  High dosing was a load of 5 mg/kg to 40 mg/kg with a maintenance of 2.5 mg/kg to 15 mg/kg.  The variability in the dosing (some of which I would not consider high at all) makes the quality of the included studies questionable so a word of warning that the results may not truly be “high” vs “low” but rather “inconsistently high” vs. “inconsistently low”.

The results though may show some interesting findings that I think provide some reassurance that higher dosing can allow us to sleep at night. image.png.616fa09a93facce802265c01a9dd6bbb.png

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On the positive front, while there was no benefit to BPD and mortality at 36 weeks PMA they did find if they looked only at those babies who were treated with caffeine greater than 14 days there was a statistically significant difference in both reduction of BPD and decreased risk of BPD and mortality.  This makes quite a bit of sense if you think about it for a moment.  If we know that caffeine improves the chances of successful extubation and we also know it reduces apnea, then who might be on caffeine for less than 2 weeks?  The most stable of babies I would expect!  These babies were all < 32 weeks at birth.  What the review suggests is that those babies who needed caffeine for longer durations benefit the most from the higher dose.  I think I can buy that.

On the adverse event side, I suppose it shouldn’t surprise many that the risk of tachycardia was statistically increased with an RR of 3.4.  Anyone who has explored higher dosing would certainly buy that as a side effect that we probably didn’t need an RCT to prove to us.  Never mind that, have you ever taken your own pulse after a couple strong coffees in the morning?

What did it not show?

It’s what the study didn’t show that is almost equally interesting.  The cerebellar hemorrhages seen in the study I previously wrote about were not seen at all in the other studies.  There could be a lesson in there about taking too much stock in secondary outcomes in small studies…

Also of note, looking at longer term outcome measures there appears to be no evidence of harm when the patients are all pooled together.  The total number of patients in all of these studies was 620 which for a neonatal systematic review is not bad.  A larger RCT may be needed to conclusively tell us what to do with a high and low dosing strategy that we can all agree on.  What do we do though in the here and now?  More specifically, if you are on call tomorrow and a baby is on 5 mg/kg/d of caffeine already, will you intubate them if they are having copious apneic events or give them a higher dose of caffeine when CPAP or NIPPV that they are already on isn’t cutting it?  That is where the truth about how you feel about the evidence really comes out.  These decisions are never easy but unfortunately you sometimes have to make a decision and the perfect study hasn’t been done yet.  I am not sure where you sit on this but I think this study while certainly flawed gives me some comfort that nothing is truly standing out especially given the fact that some of the “high dose” studies were truly high.  Will see what happens with my next patient!

 

 

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