The effects of oxytocin on intracranial pressure.

The commonly used vasodilators sodium nitroprusside and nitroglycerine increase the intracranial pressure (ICP). Oxytocin is also a vasodilator although its primary effect is contraction of uterine smooth muscle. We therefore studied the effect of oxytocin on the ICP of cats. Twelve cats were assigned to two equal groups. One group had normal ICP and in the other the ICP was artificially increased by inflating a balloon placed in the extradural space. All of the cats initially received an oxytocin infusion for 15 min. After a period of stabilization, an additional dose of oxytocin was injected as a bolus. Oxytocin administered as an infusion did not change the ICP significantly in any of the cats. Oxytocin administered as a bolus increased the ICP from 27 +/- 4 to 31 +/- 2 mm Hg in the cats with artificially increased ICP. There were no significant changes in the mean blood pressure or heart rate in either group.