Spinal anesthesia for cesarean section is regaining popularity. The effects of patient variables on the spread of sensory blockade have been reported to vary widely. We evaluated the effects of abdominal circumference, fundus height and cerebrospinal fluid pressure on the spread of sensory blockade following subarachnoid hyperbaric bupivacaine with fentanyl in term parturients. We also evaluated the effects of age, height, weight, body mass index on the spread of sensory blockade.

Sixty healthy term parturients scheduled for elective cesarean section, were measured for, abdominal circumference, fundus height, cerebrospinal fluid pressure, and received 8 mg of 0.5% hyperbaric bupivacaine with fentanyl 20microgram intrathecally. Maximal sensory block height and blood pressure were assessed. Intraoperative visceral pain was checked as discribed using four grades.

Age, weight, abdominal circumference, fundus height and cerebrospinal fluid pressure were not found to be correlated with the spread of sensory blockade. However, height and body mass index correlated with the spread of sensory blockade (P<0.05).

It is necessary to vary the dose of injected hyperbaric bupivacaine according to changes in height and body mass index.