Obesity, gravity, and spread of epidural anesthesia.

Epidural anesthesia was administered for cesarean section in 250 patients using 20 ml of 0.75% bupivacaine administered at L3-4 with the patient in a sitting position for 5 minutes. Comparing the results with those obtained in a previous study in which parturients were kept horizontal at all times, it was found that the sitting position limited cephalad spread of anesthesia only in obese patients and that the decrease in spread was in proportion to the degree of obesity. The previous findings that cephalad spread is positively correlated to body mass index BMI (weight in kilograms divided by height in meters squared) and with body weight were confirmed.