March 3, 2007
NEW YORK (Reuters Health) Mar 15 – The combination of meperidine and skin surface warming additively reduces the shivering threshold when mild hypothermia is induced, a new study shows.
Therapeutic induction of mild hypothermia has been shown to improve outcome after cardiac arrest and may have benefits in the setting of ischemic stroke and myocardial ischemia, investigators note in the February 23rd online issue of Critical Care.
“However, in the awake patient even a small decrease of core temperature provokes vigorous autonomic reactions — vasoconstriction and shivering, which both inhibit efficient core cooling,” Dr. Oliver Kimberger from University of Bern, Switzerland, and colleagues point out.
The investigators tested the hypothesis that the combination of meperidine (target plasma level: 0.9 g/mL), which has anti-shivering action, together with skin surface warming decreases the shivering threshold below 34 C without causing significant sedation or respiratory toxicity.
Eight volunteers participated for 4 study days. The subjects were assigned to a control treatment; skin warming only (with forced air and warming mattress); meperidine only; or skin warming plus meperidine. Cooling was achieved with infusion of 4 C cold Ringer’s lactate and shivering threshold was identified by an increase in oxygen consumption of plus 20% of baseline. Sedation was determined using the Observer’s Assessment of Sedation/Alertness Scale.
The team found that the shivering threshold with control was 35.5 degrees C. Skin warming alone reduced the shivering threshold to 34.9 C and meperidine alone reduced it to 34.2 C.
However, “the synergistic interaction between medium-dose meperidine and skin surface warming enables core temperature cooling of volunteers to 33.8 +/- 0.2 C with only very little sedation” and no respiratory toxicity, Dr. Kimberger told Reuters Health.
“This combination is therefore recommendable for therapeutic hypothermia,” the study leader said.
Reuters Health Information 2007. © 2007 Reuters Ltd. – Critical Care 2007