Patient Variables and the Subarachnoid Spread of Hyperbaric Bupivacaine in the Term Patient

Abstract

Among the variables suggested as influencing the spread of sensory blockade following subarachnoid injection of local anesthetics have been age, height, weight, and body mass index; with height the most commonly considered. To reevaluate this issue, the author studied 52 parturients scheduled for cesarean section under spinal anesthesia, elective and urgentin labor. Following standardized preparation, including prehydration with 2 1 balanced salt solution, all patients were placed in the right lateral decubitus position. After the distance from the sacral hiatus to the C7 prominence was measured, all patients received a subarachnoid injection of 2 ml 0.75% bupivacaine (15 mg) in 8.25% dextrose plus 0.3 ml of 0.05% morphine (0.15 mg) through a 25-gauge needle placed at L3–4 or L2–3. Patients were turned supine immediately and provided with left uterine displacement, but no other movement was performed. An investigator blinded to the distance measured determined bilateral levels of analgesia (pin prick) and anesthesia (light touch). Linear regression analysis was employed to correlate spread of sensory blockade to any of the measured variables.