Supplementary Table S1: Opioid equianalgesic conversion chart
Opioid Administration
route Dose equivalent to 1 mg of parenteral morphine (mg)
Morphine Oral 3
Fentanyl Intravenous 0.01
Alfentanil Intravenous 0.087
Remifentanil Intravenous 0.01
Tramadol Intravenous 7.5
Tramadol Oral 15
Meperidine Intravenous 7.5
Supplementary Table S2: Subgroup analyses of current versus never smokers for postoperative pain outcomes
Never smoker Current smoker Unstandardized beta
(95% CI) p
Postoperative opioid consumption, MME†
Age ≥ 65 years 25.0 (15.2, 43.7) 39.9 (16.2, 49.0) 0.117 (-0.504, 0.739) 0.710 Age < 65 years 43.2 (25.0, 71.1) 52.1 (30.3, 78.5) 0.343 (0.100, 0.587) 0.006
Male 37.5 (23.4, 84.6) 49.5 (30.5, 79.8) 0.290 (-0.061, 0.641) 0.105
Female 39.6 (22.0, 66.0) 48.0 (29.0, 69.2) 0.415 (0.108, 0.723) 0.008
Body mass index ≥ 30 kg·m-2 42.4 (25.2, 78.3) 50.0 (30.3, 67.0) 0.262 (-0.251, 0.775) 0.315 Body mass index < 30 kg·m-2 38.1 (21.0, 66.0) 48.5 (30.0, 77.5) 0.331 (0.078, 0.584) 0.011 Current sedative-hypnotic use 36.0 (20.6, 66.0) 55.0 (30.0, 94.1) 0.163 (-0.294, 0.619) 0.483 No current sedative-hypnotic use 40.5 (22.4, 68.0) 48.8 (30.0, 70.1) 0.351 (0.090, 0.613) 0.009 General anesthesia 33.8 (19.0, 60.0) 51.8 (31.0, 78.1) 0.374 (0.131, 0.617) 0.003 Neuraxial anesthesia 48.4 (28.1, 78.3) 30.0 (17.0, 49.0) -0.401 (-1.176, 0.374) 0.309 Mean daily maximum NRS pain score‡
Age ≥ 65 years 3.0 (2.4, 3.5) 2.9 (2.5, 3.4) 0.061 (-0.138, 0.261) 0.545
Age < 65 years 2.9 (2.4, 3.4) 3.2 (2.5, 3.8) 0.085 (-0.005, 0.174) 0.063
Male 3.0 (2.4, 3.8) 3.3 (2.6, 3.8) 0.128 (0.010, 0.246) 0.034
Female 2.9 (2.4, 3.4) 3.0 (2.4, 3.8) 0.058 (-0.059, 0.176) 0.330
Body mass index ≥ 30 kg·m-2 2.8 (2.3, 3.3) 3.2 (2.5, 3.7) 0.090 (-0.097, 0.277) 0.344 Body mass index < 30 kg·m-2 3.0 (2.4, 3.5) 3.1 (2.5, 3.8) 0.088 (0.001, 0.176) 0.048 Current sedative-hypnotic use 3.1 (2.5, 3.6) 3.4 (2.8, 3.9) 0.187 (0.042, 0.332) 0.012 No current sedative-hypnotic use 2.9 (2.4, 3.4) 3.0 (2.5, 3.6) 0.052 (-0.043, 0.146) 0.284 General anesthesia 3.0 (2.5, 3.5) 3.3 (2.6, 3.8) 0.111 (0.026, 0.196) 0.011 Neuraxial anesthesia 2.8 (2.3, 3.3) 2.4 (2.1, 2.7) -0.186 (-0.461, 0.088) 0.183 Numbers of IV-PCA infusion requests§
Age ≥ 65 years 28 (13, 59) 49 (21, 74) 0.314 (-0.101, 0.729) 0.138
Age < 65 years 40 (20, 83) 54 (27, 99) 0.188 (0.014, 0.361) 0.034
Male 48 (18, 92) 49 (25, 88) 0.155 (-0.079, 0.389) 0.193
Female 37 (17, 76) 56 (28, 99) 0.304 (0.088, 0.519) 0.006
Body mass index ≥ 30 kg·m-2 41 (22, 83) 48 (22, 64) 0.036 (-0.339, 0.411) 0.850 Body mass index < 30 kg·m-2 37 (17, 76) 55 (28, 99) 0.231 (0.055, 0.406) 0.010 Current sedative-hypnotic use 37 (17, 75) 51 (27, 111) 0.174 (-0.127, 0.476) 0.256 No current sedative-hypnotic use 38 (18, 77) 55 (24, 84) 0.194 (0.004, 0.384) 0.046
General anesthesia 34 (15, 70) 55 (27, 100) 0.276 (0.102, 0.450) 0.002
Neuraxial anesthesia 46 (25, 88) 43 (18, 55) 0.103 (-0.438, 0.645) 0.708
Values are median (interquartile range). CI = confidence interval; IV-PCA = intravenous patient-controlled analgesia; MME = morphine milligram equivalent; NRS = numeric rating scale. † Adjusted for age, sex, current sedative-hypnotic use, surgical sites, laparoscopic or robotic surgery, type of anesthesia, and anesthesia duration. ‡ Adjusted for body mass index, current sedative-hypnotic use, surgical sites, and anesthesia duration. § Adjusted for age, sex, hemoglobin level, surgical sites, and laparoscopic or robotic surgery.