• Geoff Frawley and Md Hamidul Huque.
• Department of Paediatric Anaesthesia and Pain Management, Royal Childrens Hospital, Melbourne, VIC, Australia.
• Paediatr Anaesth. 2017 Oct 1; 27 (10): 1037-1042.

BackgroundGender differences in absorption, distribution, and metabolism of a number of anesthetic agents have been identified in adults. Clinically, adult studies suggest women demonstrate slower onset of opioid analgesic effects, lower spinal and epidural dose requirements, and greater sensitivity to neuromuscular blocking agents. Sex-related differences in the pharmacokinetics and pharmacodynamics of local anesthetics in neonates and infants, however, have not been well documented. As a result, it is not known whether modification of the dose of local anesthetic for awake spinal anesthesia in infants is required.AimsOur aim was to determine whether the ED50 and ED95 of local anesthetics used for infant spinal anesthesia are different between sexes.MethodsThis was a retrospective analysis of data previously collected during dose-response studies of levobupivacaine and ropivacaine spinal anesthetics. The doses were reanalyzed using generalized linear regression analysis to determine whether there is a discernible difference in dose requirements between male and female infants.ResultsOne hundred and twenty infant spinal anesthetics were reviewed. For levobupivacaine, the ED50 (95% CI) was 0.69 (0.49-0.88) mg vs 0.49 (0.33-0.65), whereas the ED95(95% CI) was 1.07 (0.73-1.41) vs 0.93 (0.64-1.22) for girls and boys, respectively. For ropivacaine spinal anesthesia, the ED50 (95% CI) was 0.64 (0.35-0.92) mg vs 0.30 (-0.32-0.92), whereas the ED95 (95% CI) was 1.30 (0.73-1.87) vs 1.66 (0.55-2.76) for girls and boys, respectively.ConclusionThere is no evidence that sex differences occur at the ED50 dose range or at the clinically relevant ED95 dose. Modification of spinal anesthetic dose is not required for infant girls.© 2017 John Wiley & Sons Ltd.

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