Ephedrine requirements during spinal anesthesia for cesarean delivery in Jordanian parturients: association with β2-adrenoceptor gene variants

BACKGROUND: Maternal hypotension after spinal anesthesia for cesarean delivery is common. Many studies performed on the β2-adrenoceptor (β2AR) gene variants and their association with vasopressor requirements during and after neuroaxial block have contradictory conclusions. OBJECTIVES: The aim of the study was to evaluate the influence of the β2AR in codons 16 and 27 on the incidence of maternal hypotension and ephedrine consumption after spinal anesthesia for cesarean delivery in an Arab ethnic group. DESIGN: A prospective gene association study. SETTING: Jordan University Hospital from 1 July 2013 to 31 January 2014. PATIENTS AND METHODS: We enrolled parturients who underwent cesarean delivery under spinal anesthesia. Spinal anesthesia was performed with 10 mg plain bupivacaine along with 25 μg fentanyl. Hypotension was treated with ephedrine and the amount consumed in the first 30 minutes after spinal anesthesia was calculated. The β2AR genotype at codons 16 and 27 was determined. We studied the correlation between the β2AR genotype and the amount of ephedrine consumption after spinal anesthesia. MAIN OUTCOME MEASURES: Amount of ephederine used. RESULTS: Of 250 patients enrolled in the study, genotype and clinical data were available for 234 cases. Ephedrine was used in 94% of patients. There was a significant effect of β2AR genotype on ephedrine dose in the first 30 minutes after spinal anesthesia in codon 16 and 27. Arg16 homozygotes received less ephedrine (14.0 [11.2] mg) than Gly16 homozygotes (38.6 [25.7] mg) and Arg16Gly heterozygotes (33.42 [22.70] mg) (P<.0001). Gln27 homozygotes received less ephedrine (18.2 [12.8] mg) than Glu 27 homozygotes (47.5 [27.0] mg) and Gln27Glu heterozygotes (48.2 [23.7] mg). (P<.0001). CONCLUSION: In an Arab ethnic group, the β2AR gene has a role in maternal hypotension after spinal anesthesia. The Gly16 and Glu27 alleles have a higher incidence of arterial hypotension and required a greater amount of vasopressor to treat hypotension compared with homozygous Arg16 and Gln27 carriers. LIMITATIONS: Fasting time and hydration protocol, the use of a fixed dose of ephedrine, and relatively small sample size.