Abstract
Background: There is 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 reduced in obese patients or not. In this prospective, observation study, we tested the influence of BMI on vasopressor requirements and block height.
Methods: Three groups of 40 parturients, group A (Bodymass 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 12.5mg 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 height 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 were 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 rate (PEFR) in group C than group A, B, 30 minutes after subarachnoid injection of bupivacine (P = 0.004) (343.75 35.06 vs 335.36 32.96 vs 320.38 24.0 ml). No cases required analgesic supplementation.
Conclusion: Sensory testing using touch modality to detect extent of anesthesia, showed at 25 minutes after spinal anesthesia induction, significant higher level in group C than the other two groups. Vasopressor requirements during the first 45 minutes of spinal anesthesia were not different between group A, B but significantly higher in group C. Time for regression of anesthesia was longer in group C, which may be helpful regarding longer surgical time. Single shots spinal anesthesia of 12.5 mg hyperbaric bupivacine produce clinically equivalent effect in parturients with BMI < 45 Kg/m2 with no need for dose reduction but caution and dose adjustment recommended in parturients with BMI > 45 Kg/m2.
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