Pencil-point needle bevel direction influences ED50 of isobaric ropivacaine with fentanyl in spinal anesthesia for cesarean delivery: A prospective, double-blind sequential allocation study

Abstract

Background: There is little evidence on the influence of bevel direction of a pencil-point needle on the median effective dose (ED50) of isobaric ropivacaine and fentanyl in spinal anesthesia for cesarean delivery. Methods: In this prospective, double-blind, sequential allocation study, 82 parturients scheduled for elective cesarean delivery under combined spinal-epidural anesthesia were included. We sought to determine the median effective dose of intrathecal 0.75% isobaric ropivacaine plus fentanyl 15 lg with two different bevel directions of a 26-gauge Whitacre needle using up-down sequential allocation. Parturients were randomly allocated to either Group Ce (needle aperture oriented in a cephalad direction) or Group Ca (aperture directed caudally). The initial dose was 0.75% ropivacaine 11.25 mg plus fentanyl 15 lg in both groups. Each dose was classified as effective if, after 15 min and during the next 60 min, there was inability to appreciate pin-prick as sharp at T4, a visual analogue pain score <2 and no requirement for an epidural rescue bolus. Results: Eighty patients were included in the analysis. The ED50 in group Ca was significantly higher (13.09 mg, 95% CI 12.19-14.00) than in group Ce (10.10 mg, 95% CI 9.54-10.65, P <0.001). Conclusion: The orientation of the distal aperture of a 26-gauge Whitacre needle during induction of spinal anesthesia for cesarean delivery influences the ED50 of 0.75% ropivacaine. Copyright © 2015 Elsevier Ltd. All rights reserved