Fentalyl or Morphine during cooling procedure?

[Zuzana Tomaskova]

Dear All,

I would like to seek your help. I remember I read about differences between Fentanyl and Morphine action during cooling protocol in our NICU patients. Unfortunately, I cannot find the evidence now (may be I am looking wrong) whether Fentanyl or Morphine is better option. Both are metabolised slower during cooling and we have to be careful in administration. My knowledge is that Morphine was drug of choice due to better binding to pain receptors and a bit better action during cooling. I remember some article (from Pediatrics, Neoreview?) and there was mentioned even some protective effect of Morphine. Can you help me with sources or whether it is still true? I know that now Clonidine is being studied as possible neuroprotective drug too but nothing specific about mentioned  meds above.

Thank you very much

Zuzana

[Hamed]

Hi, concerning morphine and fentanyl during cooling, smaller doses as potentially toxic serum concentrations of morphine may occur with hypothermia with doses above 10 mcg/kg/h. Start 5 mcg/kg/h and not exceed 10 mcg/kg/h. Another option is  boluses 50 mcg/kg/4hrs. As for Fentanyl 0.5 mcg/kg/h max is 1 mcg/kg/h or boluses 0.5mcg/kg every 2 ~4 hs.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3552186/

I am not sure about the better action of morphine, but what I know that fentanyl shows a rebound increase in serum levels during rewarming. on the other hand, in cooling Morphine glucuronidation is inhibited in cooling and thus M3G (a product of morphine glucuronidation) is less produced which is a potent opiate receptor antagonist. http://neoreviews.aappublications.org/content/14/1/e22?sso=1&sso_redirect_count=1&nfstatus=401&nftoken=00000000-0000-0000-0000-000000000000&nfstatusdescription=ERROR%3a+No+local+token

Although, fentanyl is 80 times more potent to morphine, we usually use fentanyl in our unit with doses less than 1 mcg/kg/h.