The effects of morphine, morphine plus scopolamine, midazolam and promethazine on cerebrospinal fluid histamine concentration and postoperative analgesic consumption.

The effects of morphine (0.14 mg/kg), morphine (0.14 mg/kg plus scopolamine (0.042 mg/kg), midazolam (0.015 mg/kg) and promethazine (0.08 mg/kg) on cerebrospinal fluid histamine (CSF-HA) and CSF-methylhistamine were investigated in 44 healthy patients. CSF-HA was determined by HPLC. CSF-HA was found to be increased after all premedications with great individual variation (range 0.07-7.4 pmol/ml). The highest values were found in the promethazine group (1.83 +/- 2.2 (SD) pmol/ml and the lowest in the control group (0.63 +/- 0.42 pmol/ml). Measurable concentrations of CSF-methylhistamine were found in 13 patients without correlation with HA. Postoperative need for analgesics was reduced in all premedicated groups. A significant correlation existed between HA and need for postoperative analgesics in the morphine plus scopolamine group. It is concluded that the histamine system plays a role in central nociception.