“…Of the 55 studies, three were randomized controlled trials, 37 , 80 , 93 and 52 were observational cohort studies. The studies included various surgical specialties or aggregates thereof, including 8 or more specialties, 81 , 91 breast surgery, 59 , 73 , 74 , 101 cardiac surgery, 44 , 45 , 52 , 53 , 56 , 65–67 , 70 , 89 , 90 , 99 , 100 colorectal surgery, 34 , 61 , 68 , 71 , 78 , 85 , 92 , 103 , 104 ENT surgery, 75 gastrointestinal surgery, 34 , 83 general surgery, 34 , 37 , 57 , 77 , 79 , 82 , 86 , 93 , 95 , 96 , 102 obstetrics, 80 ophthalmology, 97 orthopedic surgery, 55 , 76 , 84 , 102 rectal surgery, 72 , 98 spinal surgery, 58 trauma surgery, 87 and urology. 62–64 , 69 , 88 , 94 , 102 38 studies were conducted in the USA, 10 in the UK, two in Austria and Sweden, one each in Canada, France, and Germany.…”