Effects of ketamine on the pregnant uterus.

Intra-uterine pressure was recorded by placing a Foley catheter in the extra-amniotic space before the termination of pregnancy in 25 patients, and Caesarean section in 12 patients. The effects of administration of i.v. ketamine 2 mg/kg body weight, sodium thiopentone 4 mg/kg body weight and ergometrine 0.5 mg, and intra-cervical 0.5% lignocaine 20 ml were measured in the first trimester of pregnancy, and i.v. ketamine and sodium thiopentone in late pregnancy. Ketamine was found to cause uterine contraction (mean increase 16.1 mm Hg) equal to ergometrine (mean increase 14.8 mm Hg) in early pregnancy, but exert no effect (mean decrease -- 1.33 mm Hg) in late pregnancy. Lignocaine in early pregnancy given as a paracervical block had no significant effect on intrauterine pressure (mean increase 0.33 mm Hg). Sodium thiopentone (mean decrease -- 4.28 mm Hg first trimester and -- 2.22 mm Hg at term) in late pregnancy had no significant effect on intra-uterine pressure.