Urine catecholamine excretion after large doses of fentanyl, fentanyl and diazepam and fentanyl, diazepam and pancuronium.

The effects of fentanyl (0.5 mg/kg iv), fentanyl with diazepam (1 mg/kg iv) and fentanyl, diazepam and pancuronium (0.1 mg/kg iv) on heart rate (HR), mean arterial blood pressure (BP), cardiac output (QT), urine flow rate and urine epinephrine and norepinephrine excretion were determined in nine dogs. Fentanyl did not significantly change QT or BP but did reduce HR and urine flow rate (P less than 0.05). Urine epinephrine and norepinephrine excretion rates were signicantly increased by fentanyl (P less than 0.05). Diazepam caused no significant further changes in QT, BP or HR 30 minutes after administration, but urine epinephrine and norepinephrine excretion rates were reduced to control (pre-fentanyl) levels. Addition of pancuronium after fentanyl and diazepam increased urine flow rate to pre-fentanyl levels and elevated QT, BP and HR above controls but produced no significant change in urine epinephrine or norepinephrine excretion. These data suggest that fentanyl increases catecholamine blood levels and imply that the latter may be one mechanism by which cardiovascular dynamics are maintained stable during fentanyl anaesthesia. Our findings also demonstrate that cardiovascular stimulation after pancuronium is not associated with increased urinary catecholamine excretion.