Evidence that intravenous vasopressors can affect rostral spread of spinal anesthesia in pregnancy.
BACKGROUND
The authors have previously observed an apparent association between rostral spread of spinal anesthesia and choice of intravenous vasopressor given to maintain maternal systolic arterial pressure during cesarean delivery. This study tested the hypothesis that an intravenous infusion of phenylephrine can reduce rostral spread of spinal anesthesia in pregnancy, compared with ephedrine.


METHODS
The study was randomized and double blind. It compared phenylephrine 100 microg/ml (phenylephrine group, n = 30), and ephedrine 3 mg/ml (ephedrine group, n = 30), given by infusion, to prevent maternal hypotension during combined spinal-epidural anesthesia for cesarean delivery. Two ml intrathecal plain levobupivacaine, 0.5%, combined with 0.4 ml intrathecal fentanyl, 50 microg/ml, and 10 ml epidural saline was given with the patient in the sitting position. The upper level of neural blockade to cold and light touch sensation was recorded at 10 and 20 min postspinal. Epidural space pressure was recorded at 5, 10, 15, and 20 min.


RESULTS
At 20 min, the upper dermatome blocked to cold sensation was median T3 (interquartile range, T2-T4) for the phenylephrine group, compared with T1 (T1-T2) for the ephedrine group (P = 0.001). At 20 min, the upper dermatome blocked to light touch sensation was median T5 (T4-T8) for the phenylephrine group, compared with T3 (T2-T6) for the ephedrine group (P = 0.009). The mean epidural space pressure in the phenylephrine group was 16 (13-19) mmHg, compared with 16 (13-18) mmHg in the ephedrine group (P = 0.63).


CONCLUSIONS
This study provides evidence that intravenous phenylephrine can decrease rostral spread of spinal anesthesia in pregnancy, compared with intravenous ephedrine. Further work is required to investigate possible mechanisms and to assess its clinical significance.
Cooper
David W
DW
Department of Anaesthesia, James Cook University Hospital, Middlesbrough, Cleveland, United Kingdom. david.cooper@stees.nhs.uk
Jeyaraj
Leo
L
Hynd
Ryan
R
Thompson
Rebekah
R
Meek
Tim
T
Ryall
David M
DM
Kokri
Manmohan S
MS
D000328:Adult; D000773:Anesthesia, Obstetrical; D000775:Anesthesia, Spinal; D018686:Anesthetics, Intravenous; D000779:Anesthetics, Local; D001794:Blood Pressure / Q000187:drug effects; D002045:Bupivacaine; D002585:Cesarean Section; D004311:Double-Blind Method; D004809:Ephedrine / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D005283:Fentanyl; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007231:Infant, Newborn; D007275:Injections, Intravenous; D007278:Injections, Spinal; D010147:Pain Measurement / Q000187:drug effects; D010656:Phenylephrine / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*
D018686:Anesthetics, Intravenous; D000779:Anesthetics, Local; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D004809:Ephedrine; D005283:Fentanyl; D002045:Bupivacaine