Anesthesia and analgesia
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Anesthesia and analgesia · Aug 1988
Cardiovascular effects of fentanyl reversal by naloxone at varying arterial carbon dioxide tensions in dogs.
Clinical reports, as well as animal studies, have described cardiovascular and sympathetic stimulation after the administration of naloxone (NX) to reverse opioid-induced respiratory depression. This investigation examines the effect of PaCO2 on hemodynamic and adrenergic responses to NX, by means of 24 experiments carried out in six dogs. Each dog underwent NX reversal of fentanyl (FEN) at three different PaCO2 levels: 20, 35, and 60 mm Hg. ⋯ NE levels were greater in hypercapnic dogs at all time periods after NX. In blocked dogs, neither F nor NX had any effects on hemodynamic functions or plasma CA levels; the institution of hypercapnia caused significant decreases in HR, MAP, and systemic vascular resistance. This direct circulatory depressant action of an elevated PCO2 may have attenuated the indirectly mediated excitatory hemodynamic effects of NX in intact dogs, thus explaining the relatively greater effect of hypercapnia on adrenergic than on hemodynamic responses to reversal.(ABSTRACT TRUNCATED AT 250 WORDS)