Influence of Ketamine on Non-Pregnant Uterus in Vivo

This investigation was performed to evaluate the effect of ketamine anesthesia on non-pregnant uterine activity. Seven healthy non-pregnant women took part in the study. Anesthesia was induced with an i.v. bolus injection of ketamine 2 mg/kg and maintained with a continuous i.v. ketamine infusion, mean dosage 39 μg/kg/min. Before induction of anesthesia, each patient was placed in the lithotomy position, and a catheter fitted with two microtransducers for monitoring of intra-uterine pressures was fed through the cervix into the uterine cavity. For determination of plasma concentrations of ketamine and norketamine, venous blood samples were collected. The assay was based on a gas-liquid chromatographic technique. It was found that ketamine induced an increased uterine activity, both in basal tone and intensity of contractions. Only minor effects on the frequency were observed. This stimulatory effect was simultaneous with a hemodynamic stimulation with increases in heart rate and arterial blood pressure, and with the peak plasma concentration of ketamine.