Effects of pentazocine on cardiovascular and plasma catecholamine responses in surgical patients

There are no reports in the literature regarding the effect of pentazocine (PENT) on autonomic responses to surgical stimulation. Therefore, we examined the effects of intravenously administered (iv) PENT, either before or after the skin incision, on the cardiovascular and plasma catecholamine responses, as characterized by plasma levels of epinephrine (Epi) and norepinephrine (Nor), to surgical noxious stimulation of patients. Hemodynamic and sympathoadrenergic reactions occurred after the skin incision had been made, and iv PENT (0.6 mg/kg) before the incision attenuated both cardiovascular and sympatho-adrenal responses to surgical stimulation compared with those after the skin incision under isoflurane-nitrous oxide anesthesia. The attenuation of these responses to surgical stimulation was greater at 0.6 mg/kg than at 1.2 mg/kg. Our present data suggest that it might be difficult for iv PENT to block the activated sympathetic outflows once the sympathetic nervous system has been activated by surgically noxious stimulation. According to our present results, iv PENT (0.6 mg/kg, but not 1.2 mg/kg) before a skin incision seems to be of clinical relevance for attenuation of the hemodynamic response to surgical stimulation although the effects of PENT on the autonomic nervous system appears to be complex and difficult to interpret.