Effect of Body Mass Index on Anesthesia Characteristics and Vasopressor Requirements during Spinal Anesthesia for Elective Cesarean Section

Abstract

Background: There is a debate about the dose of hyperbaric bupivacine for spinal anesthesia for cesarean delivery in obese parturients. While it is concessive that the dose of spinal bupivacine is reduced in pregnant compared with non-pregnant parturient due to many factors. But it is still controversial whether local anesthetic should further reduce in obese patients or not. In this perspective, observation study, we tested the influence of BMI on vasopressor requirements and block height. Methods: Three groups of 40 parturients, group A (Body mass index (BMI) < 30 kg/m2), group B (BMI 30 - 45 Kg/m2) and group C (BMI > 45 kg/m2) requiring elective cesarean section were recruited all patients received 12.5 mg subarachnoid hyperbaric bupivacine combined with 20 ug fentanyl. Dermatomal levels were assessed after subarachnoid injection using touch sensation at 2 minutes interval for first 10 minutes then every 5 minutes. Vasopressor requirements in the first 45 minutes after subarachnoid injection, and maximum block heights using touch sensation were assessed as primary outcomes. Secondary outcomes were extent of motor block (peak flow rate), technique difficulty (number of attempts), maternal side effects and neonatal outcomes. Results: There was no significant difference in mean blood pressure (MBP) between group A and B but the difference was significant in group C in relation to other two groups, mean number of hypotensive episodes was significantly higher in group C than group A, B with no significant difference in incidence between group A and B (P < 0.001) (3.28 vs 3.98 vs 5.98). Total dose of vasoprenor and total volume of fluid infused were higher in group C than group A, B. In group A the maximum block level extended above T3 in 5 patients (12.5%), with predominance of T5 (35%), in group B the maximum level extended above T3 in 10 patients (25%) with predominance of T4 (45%) and in group C the maximum block level extended above T3 in 21 patients (52.5%) with predominance of T3 (32.5%). Significant decrease in the mean of peak expiratory flow