“…Seventeen trials [ 28 , 29 , 31 – 33 , 35 , 36 , 39 , 41 , 43 , 45 – 51 ] included patients who were less than 65 years old, and 14 trials [ 3 , 9 , 24 – 27 , 30 , 34 , 37 , 38 , 40 , 42 , 44 , 52 ] included patients who were more than 65 years old. As for the type of alpha-1 adrenergic agonists used in studies, 17 studies [ 3 , 25 , 27 – 30 , 34 – 38 , 40 , 44 , 45 , 49 – 52 ] selected norepinephrine, 11 studies [ 24 , 26 , 31 – 33 , 39 , 41 , 42 , 50 , 52 ] considered phenylephrine, 2 studies [ 43 , 46 ] used norepinephrine and phenylephrine, and 1 study [ 9 ] used metaraminol. Additionally, 18 trials [ 3 , 27 – 29 , 31 , 32 , 35 , 37 , 38 , 40 – 45 , 47 , 48 , 52 ] involved abdominal surgery.…”