Characteristics and methodological quality of included studies.

BMI: body mass index ASA: American Society of Anesthesiologists RCT: randomized controlled trial RA: regional anesthesia EA: epidural anesthesia ND: not demonstrated GA: general anesthesia CSEA: combined spinal epidural anesthesia SA: spinal anesthesia CS: cohort study* Originally twenty patients included in the RA group, but one patient converted to GA.**Totally 69 patients were included in the GA group, the authors [16] might report a wrong number here.Characteristics and methodological quality of included studies.