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.
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 15μg 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 11.25mg plus fentanyl 15μg in both groups. Each dose was classified as effective if, after 15min and during the next 60min, 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 (13.09mg, 95% CI 12.19-14.00) than in group Ce (10.10mg, 95% CI 9.54-10.65, P <0.001).


CONCLUSIONS
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.
Anesthesiology Department, "Alexandra" General Hospital of Athens, Greece. Electronic address: arkaskostas@yahoo.gr.
K
K
Stroumpoulis
Anesthesiology Department, "Alexandra" General Hospital of Athens, Greece.
E
E
Stamatakis
1st Departement of Obstetrics & Gynecology, University of Athens Medical School, "Alexandra" General Hospital of Athens, Greece.
P
P
Koutroumanis
Anesthesiology Department, "Alexandra" General Hospital of Athens, Greece.
A
A
Loukeri
Anesthesiology Department, "Alexandra" General Hospital of Athens, Greece.
D
D
Valsamidis
D000328:Adult; D000577:Amides / Q000008:administration & dosage*; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000773:Anesthesia, Obstetrical; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002585:Cesarean Section; D004311:Double-Blind Method; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage*; D006801:Humans; D011247:Pregnancy; D011446:Prospective Studies; D000077212:Ropivacaine
D000577:Amides; D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D000077212:Ropivacaine; D005283:Fentanyl
Bevel direction; Cesarean delivery; ED50; Pencil-point; Ropivacaine; Spinal anesthesia