Minimum effective bolus dose of oxytocin during elective Caesarean delivery.
BACKGROUND
The aim of this study was to determine the lowest effective bolus dose of oxytocin to produce adequate uterine tone (UT) during elective Caesarean delivery (CD).


METHODS
Seventy-five pregnant patients undergoing elective CD under spinal anaesthesia were randomized to receive oxytocin (0.5, 1, 3, 5 units) or placebo. UT was assessed by a blinded obstetrician as either adequate or inadequate, and using a verbal numerical scale score (0-10; 0, no UT; 10, optimal UT) at 2, 3, 6, and 9 min after oxytocin administration. Minimum effective doses of oxytocin were analysed (ED(50) and ED(95)) using logistic regression. Oxytocin-related side-effects (including hypotension) were recorded.


RESULTS
There were no significant differences in the prevalence of adequate UT among the study groups at 2 min (73%, 100%, 93%, 100%, and 93% for 0, 0.5, 1, 3, and 5 units oxytocin, respectively). The high prevalence of adequate UT after placebo and low-dose oxytocin precluded determination of the ED(50) and ED(95). UT scores were significantly lower in patients receiving 0 unit oxytocin at 2 and 3 min compared with 3 and 5 units oxytocin (P<0.05, respectively). The prevalence of hypotension was significantly higher after 5 units oxytocin vs 0 unit at 1 min (47% vs 7%; P=0.04).


CONCLUSIONS
The routine use of 5 units oxytocin during elective CD can no longer be recommended, as adequate UT can occur with lower doses of oxytocin (0.5-3 units).
Department of Anaesthesia, Stanford University School of Medicine, Stanford, CA 94305-5640, USA. ajbut@stanford.edu
A J
AJ
Butwick
L
L
Coleman
S E
SE
Cohen
E T
ET
Riley
B
B
Carvalho
D000328:Adult; D000465:Algorithms; D000773:Anesthesia, Obstetrical / Q000379:methods; D000775:Anesthesia, Spinal / Q000379:methods; D002585:Cesarean Section / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007022:Hypotension / Q000139:chemically induced; D007262:Infusions, Intravenous; D010120:Oxytocics / Q000008:administration & dosage* / Q000009:adverse effects; D010121:Oxytocin / Q000008:administration & dosage* / Q000009:adverse effects; D011247:Pregnancy
D010120:Oxytocics; D010121:Oxytocin