Intraoperative awareness risk, anesthetic sensitivity, and anesthetic management for patients with natural red hair: a matched cohort study.

PURPOSE: The red-hair phenotype, which is often produced by mutations in the melanocortin-1 receptor gene, has been associated with an increase in sedative, anesthetic, and analgesic requirements in both animal and human studies. Nevertheless, the clinical implications of this phenomenon in red-haired patients undergoing surgery are currently unknown. METHODS: In a secondary analysis of a prospective trial of intraoperative awareness, red-haired patients were identified and matched with five control patients, and the relative risk for intraoperative awareness was determined. Overall anesthetic management between groups was compared using Hotelling's T(2) statistic. Inhaled anesthetic requirements were compared between cohorts by evaluating the relationship between end-tidal anesthetic concentration and the bispectral index with a linear mixed-effects model. Time to recovery was compared using Kaplan-Meier analysis, and differences in postoperative pain and nausea/vomiting were evaluated with Chi square tests. RESULTS: A cohort of 319 red-haired patients was matched with 1,595 control patients for a sample size of 1,914. There were no significant differences in the relative risk of intraoperative awareness (relative risk = 1.67; 95% confidence interval 0.34 to 8.22), anesthetic management, recovery times, or postoperative pain between red-haired patients and control patients. The relationship between pharmacokinetically stable volatile anesthetic concentrations and bispectral index values differed significantly between red-haired patients and controls (P < 0.001), but without clinical implications. CONCLUSION: There were no demonstrable differences between red-haired patients and controls in response to anesthetic and analgesic agents or in recovery parameters. These findings suggest that perioperative anesthetic and analgesic management should not be altered based on self-reported red-hair phenotype.