The hemodynamic effects of intrathecal oxytocin in normal dogs

To evaluate the hemodynamic effects produced by intrathecal administration of oxytocin in healthy isoflurane-anesthetized dogs.

Prospective single-dose trial.

Six healthy purpose-bred adult dogs weighing between 7.3 and 14.5 kg.

Dogs were anesthetized with isoflurane and instrumented. Oxytocin at a dosage of 1.6 microg/kg was administered intrathecally at the cisternal space at time 0. Hemodynamic data were recorded immediately before and at 1, 5, 15, 30, and 60 minutes after oxytocin administration. Statistical analysis included an analysis of variance (ANOVA) for repeated measures over time. A P < .05 was considered significant.

Baseline values +/- standard error of the mean for heart rate, mean arterial pressure, central venous pressure, cardiac output, systemic vascular resistance, mean pulmonary arterial pressure, pulmonary arterial occlusion pressure, and pulmonary vascular resistance were 101 +/- 11 beats/minute, 76 +/- 7 mm Hg, 4 +/- 4 mm Hg, 1.9 +/- 0.7 L/min, 3834 +/- 2556 dynes x sec/cm5, 14 +/- 3 mm Hg, 4 +/- 2 mm Hg, and 430 +/- 201 dynes x sec/cm5, respectively. Variations from the baseline values were seen in all parameters after intrathecal oxytocin administration, but no statistically significant differences were found.

The intrathecal injection of 1.6 microg/kg of oxytocin is associated with minimal hemodynamic effects during isoflurane anesthesia.

This study revealed no clinically significant deleterious effects from the intrathecal administration of oxytocin, and investigations into its use as a perioperative analgesic are therefore warranted.