Evaluation of the influence of the codon 16 polymorphism of the Beta-2 adrenergic receptor gene on the incidence of arterial hypotension and ephedrine use in pregnant patients submitted to subarachnoid anesthesia.

BACKGROUND AND OBJECTIVES The beta-2 adrenergic receptor gene has several polymorphisms. Recent studies have demonstrated the clinical importance of the latter. The objective of the present study was to evaluate the influence of the Arg16Gli polymorphism on the incidence of arterial hypotension and ephedrine use in pregnant patients submitted to subarachnoid block for Cesarean section. METHOD Healthy parturients (ASA I and II) were submitted to subarachnoid anesthesia for elective Cesarean section (n = 50). Ephedrine was administered in cases of arterial hypotension. The incidence of arterial hypotension and the required dose of ephedrine to correct the arterial pressure were compared between the different genotypes identified. RESULTS The most prevalent genotype was Arg16Gli (60%, n = 30) followed by Gli16Gli (26%, n = 13) and Arg16Arg (14%, n = 7). No differences were observed regarding the basic characteristics of the genotypes. In comparison to the Arg16Arg genotype, the Gli16Gli presented a 3.95-fold increase in the hazard ratio of arterial hypotension (95%CI 0.86-18.11; p = 0.076), whereas the Arg16Gli presented a 4.83-fold increase (95%CI 1.13-20.50; p = 0.033). The parturients with the Arg16Arg needed, on average, 6.4 +/- 8.5 mg of ephedrine to correct the arterial hypotension, whereas those with the Arg16Gli needed 19.5 +/- 15.9 mg (p = 0.0445; 95%CI 0.3325-25.78) and the ones with the Gli16Gli genotype, 19.2 +/- 14.3 (p = 0.0445, 95%CI 0.3476-25.26). CONCLUSIONS The results show that the genetic variant Arg16Arg presents a lower incidence of arterial hypertension and that lower doses of ephedrine were necessary to reestablish normal arterial pressure in the patients with this genetic profile. We conclude that the Arg16Arg genotype confers better pressure stability to the parturients submitted to subarachnoid anesthesia for Cesarean section.