INS and clubfoot: The following variables were used to construct the fully adjusted model: (1) continuous variables: Age, BMI, Hb, LOS, duration of surgery; (2) categorical variables: Sex, ethnicity, American Society of Anesthesiologists (ASA) status, smoking, obstructive sleep apnea (OSA), diabetes mellitus (DM), ischemic heart disease (IHD), congestive cardiac failure (CCF), cerebrovascular accident (CVA), creatinine > 2 mg/dl, DM on insulin, day of week of operation.