Nalbuphine's reversal of hypovolemic shock in the anesthetized rat.

Nalbuphine is an agonist-antagonist analgesic chemically related to the opiate agonist oxymorphone and to the opiate antagonist naloxone. Because naloxone has been shown to be beneficial in hemorrhagic shock, this study was undertaken to investigate the hemodynamic effects of nalbuphine in anesthetized rats. The animals were bled 1% of body weight, which caused a significant decrease in mean arterial pressure (MAP) and heart rate (HR). Results indicate an immediate increase in MAP and HR above posthemorrhage values in the rats treated with 1 and 5 mg/kg nalbuphine compared with no improvement for the rats in the saline-treated group. The increases in MAP were sustained for periods up to 120 min postadministration of nalbuphine. Measurements of cardiac output and regional distribution of blood flow indicate that nalbuphine caused an increase in cardiac output, heart rate, stroke volume, and dP/dt with no change in total peripheral resistance.