A 29-year-old primigravida entered the obstetrical suite with a history of 12 hours of active labor and 36 hours of ruptured membranes. She had not had prenatal care. Results of physical examination were unremarkable. The cervix was fully dilated and the caput was showing. Fetal weight was estimated at 4,000 gm (9 lb). No fetal heart sounds were audible, and the hematocrit value was 32%; the results of urinalysis were normal except for 1+ acetonuria.
A continuous intravenous infusion of 5% dextrose in water was instituted, and the patient placed on the delivery table. After pudendal block had been administered, the fetal head was delivered spontaneously. However, there was shoulder dystocia, and general anesthesia was desired to provide relaxation of the lower uterine segment.
The patient denied having had food or drink for the past ten hours. Induction of anesthesia was started using a combination of nitrous oxide, oxygen, and