Predictors of topical anesthetic effectiveness in children.

UNLABELLED: Some children report significant pain with peripheral intravenous catheter (IV) insertion, despite the appropriate use of topical lidocaine anesthetics. This analysis of data from an existing study identified factors related to variation in topical anesthetic effectiveness used for IV insertion. The children (n = 218) in this investigation were 4 to 10 years old and undergoing a scheduled IV insertion. Inclusion criteria were (1) topical anesthetic was used according to manufacturer's recommendations, (2) DNA material was available, and (3) child completed a self-report measure of pain intensity (Oucher scale). Low pain phenotype was defined as a pain intensity score of 0 to 3, and high pain phenotype was an intensity score of 4 to 10. Potential predictor variables included child age, gender, number of previous painful procedures, state and trait anxiety, temperament characteristics, and alleles in 3 candidate genes in a pain pathway influenced by topical anesthetics (endothelin-1 [EDN1], endothelin receptor A [EDNRA], endothelin receptor B [EDNRB]). All subjects were genotyped for a single-nucleotide polymorphism in each gene. Children in the high pain group (n = 89) were significantly younger (P < .0001), more active (P = .0029), scored higher for trait (P = .0009) and state anxiety (P = .0312), and had the EDNRA TT genotype (high pain group, TT 67.35%; low pain group, TT 39.47%; P = .026). PERSPECTIVE: The identification of factors that influence peripheral pain sensation aids in selecting the most appropriate pharmacologic and nonpharmacologic interventions. Until genotyping is available at a clinically prescriptive level, other predictors (eg, age and activity level) can be used to tailor pain-relieving strategies for children undergoing needle sticks.