Spread of subarachnoid hyperbaric amethocaine in pregnant women.

In order to examine how the gestational period influences the spread of spinal anaesthesia, we have measured the extent of spinal block produced by hyperbaric amethocaine 8 mg in 90 women. The patients were allocated to one of five groups according to the gestational period: non-pregnant group (n = 17), first trimester group (6-12 weeks, n = 14), second trimester group (13-24 weeks, n = 26), third trimester group (25-36 weeks, n = 15) and term group (37-41 weeks, n = 18). Maximum cephalad spread of analgesia was significantly higher in the second trimester (median T3 (range T9-C6)), third trimester (T3 (T4-C7)) and term groups (T2.5 (T4-C8)) than in the nonpregnant (T4 (T8-T2)) and first trimester groups (T4 (T11-C7)). We found that not only term pregnancy but also second and third trimester pregnancies enhanced the spread of spinal anaesthesia, and that first trimester pregnancy did not affect the spread of spinal anaesthesia.