Table 1.
Patients demographics and surgery–related characteristics
| All patients (N = 2.034) |
Closed abdominal surgery (N = 906) |
Open abdominal surgery (N = 1.128) |
P–value | Absolute Difference | |
|---|---|---|---|---|---|
| Age, years | 54 [40 to 67] | 49 [36 to 64] | 58 [45 to 69] | < 0.001 | 9 [6 to 21] |
| Gender, male (%) | 42% (846/2034) | 34% (306/906) | 48% (540/1128) | < 0.001 | 14% [9 to 18%] |
| Ethnicity, % (n/N) | 0.194 | ||||
| Caucasian | 88% (1787/2.030) | 87% (786/902) | 89% (1001/1.128) | ||
| Black | 1% (20/2.030) | 1% (6/902) | 1% (14/1.128) | ||
| Asian | 3% (58/2.030) | 4% (33/902) | 2% (25/1.128) | ||
| Other | 8% (165/2.030) | 8% (77/902) | 8% (88/1.128) | ||
| BMI (Kg∙m−2) | 26.2 [23.3 to 30.0] | 26.7 [23.6 to 31.3] | 25.8 [22.9 to 29.3] | < 0.001 | 0.8 [0.04 to 1.6] |
| Weight (kg) | 75.0 [65.0 to 87.0] | 77.0 [68.0 to 93.0] | 74.0 [64.0 to 85.0] | 0.001 | 3 [8 to 13] |
| PBW (kg) | 60.6 [55.1 to 69.0] | 59.7 [54.2 to 67.8] | 61.5 [56.0 to 69.7] | < 0.001 | 1.82 [1.8 to 2] |
| ASA class, % (n/N) | < 0.001 | ||||
| 1 | 24% (495/2.028) | 31% (276/904) | 20% (219/1.124) | ||
| 2 | 49% (989/2.028) | 53% (477/904) | 46% (512/1.124) | ||
| 3 | 24% (488/2.028) | 16% (146/904) | 30% (342/1.124) | ||
| 4 | 3% (53/2.028) | 1% (5/904) | 4% (48/1.124) | ||
| 5 | 0% (3/2.028) | 0% (0/904) | 0% (3/1.124) | ||
| ARISCAT score | 26 [18 to 38] | 18 [15 to 31] | 34 [18 to 41] | < 0.001 | 16 [16 to 16] |
| ARISCAT class, % (n/N) | < 0.001 | ||||
| < 26 | 51% (985/1.945) | 68% (607/888) | 36% (378/1.057) | ||
| 26–44 | 38% (741/1.945) | 26% (231/888) | 48% (510/1.057) | ||
| > 44 | 11% (219/1.945) | 6% (50/888) | 16% (169/1.057) | ||
| Preop. SpO2,% | 98 [96 to 99] | 98 [96 to 99] | 97 [96 to 99] | 0.004 | 0 [0 to 3] |
| Current smoker, % | 20% (413/2.034) | 21% (79/906) | 20% (222/1.128) | 0.468 | 2% [3 to 7%] |
| Chronic comorbidity, % (n/N) | |||||
| Metastatic cancer | 7% (138/2.034) | 2% (22/906) | 10% (116/1.128) | < 0.001 | 8% [5 to 9%] |
| Chronic kidney failure | 4% (81/2.034) | 1% (13/906) | 6% (68/1.128) | < 0.001 | 5% [2 to 6%] |
| COPD | 7% (138/2.034) | 7.% (83/906) | 6% (55/1.128) | 0.290 | 1% [1 to 3%] |
| Heart failure | 7% (143/2.034) | 6% (53/906) | 8% (90/1.128) | 0.075 | 2% [1 to 4%] |
| OSAS | 2% (42/2.034) | 3% (27/906) | 1% (15/1.128) | 0.015 | 2% [1 to 3%] |
| Neuromuscular diseasea | 1% (17/2.034) | 1% (6/906) | 1% (11/1.128) | 0.599 | 0.3% [0.3 to 1%] |
| Liver dysfunction | 1% (29/2.034) | 1% (5/906) | 2% (24/1.128) | 0.210 | 1% [1 to 2%] |
| Functional Status, % (n/N) | < 0.001 | ||||
| Independent | 92% (1872/2.034) | 96% (867/906) | 89% (1005/1.128) | ||
| Partially dependent | 7% (135/2.034) | 4% (32/906) | 9% (103/1.128) | ||
| Totally dependent | 1% (27/2.034) | 1% (7/906) | 2% (20/1.128) | ||
| Preop. resp. infection,% (n/N) | 5% (95/2.034) | 4% (35/906) | 5% (60/1.128) | 0.150 | 2% [0.5 to 3%] |
| Preop. Hb (g∙dl−1), % (n/N) | 13.4 [12.2 to 14.0] | 13.5 12.6 to 14.5] | 13.3 [11.9 to 14.5] | < 0.001 | 0.2 [0.3 to 1] |
| Preop. anemia (Hb ≤ 10 g dl−1) | 9% (1738/1.846) | 3% (21/798) | 8% (87/1.048) | < 0.001 | 5% [3 to 7%] |
| Preop. creatinine (g∙dl− 1) | 0.8 [0.7 to 1.0] | 0.8 [0.7 to 1.0] | 0.9 [0.7 to 1.1] | < 0.001 | 0.04 [0.01 to 0.1] |
| Preop transfusion, % (n/N) | 1% (23/2.034) | 0% (3/906) | 2% (20/1.128) | 0.004 | 1% [0.5 to 1%] |
| Surgical procedureb, % (n/N) | |||||
| Lower GI | 26% (286/1.098) | 14% (124/906) | 31% (346/1.128) | < 0.001 | 17% [13 to 20%] |
| Upper GI, HBP | 28% (303/1.098) | 47% (429/906) | 20% (222/1.128) | < 0.001 | 27% [23 to 31%] |
| Vascular surgery | 2% (25/1.098) | 0% (0/906) | 3% (30/1.128) | < 0.001 | 2% [1 to 3%] |
| Aortic surgery | 2% (19/1.098) | 0% (0/906) | 2% (20/1.128) | < 0.001 | 1% [1 to 2%] |
| Urological | 19% (204/1.098) | 9% (81/906) | 14% (162/1.128) | < 0.001 | 5% [2 to 8%] |
| Gynaecological | 18% (195/1.098) | 26% (233/906) | 17% (188/1.128) | < 0.001 | 9% [6 to 12%] |
| Endocrine surgery | 1% (9/1.098) | 1% (5/906) | 1% (10/1.128) | 0.443 | 0.3% [0.5 to 1%] |
| Transplant | 2% (18/1.098) | 0% (0/906) | 2% (20/1.128) | < 0.001 | 2% [1 to 3%] |
| Neurosurgery | 5% (52/1.098) | 0% (1/906) | 10% (109/1.128) | < 0.001 | 9% [8 to 11%] |
| Other procedure | 3% (30/1.098) | 5% (43/906) | 19% (214/1.128) | < 0.001 | 14% [11 to 17%] |
| Urgency of Surgeryc, % (n/N) | < 0.001 | ||||
| Elective | 84% (1705/2.034) | 87% (792/906) | 81% (913/1.128) | ||
| Urgent | 12% (235/2.034) | 9% (85/906) | 13% (150/1.128) | ||
| Emergency | 4% (94/2.034) | 4% (29/906) | 6% (65/1.128) | ||
| Duration of surgeryd, min | 86 [55 to 149] | 70 [50 to 110] | 105 [65 to 172] | < 0.001 | 35 [21 to 43] |
| Duration of anaesthesiae, min | 115 [80 to 190] | 100 [71 to 147] | 140 [91 to 205] | < 0.001 | 40 [20 to 60] |
| Time of surgery, % (n/N) | < 0.843 | 0.2 [0.2 to 1] | |||
| Daytimef | 95% (1925/2034) | 95% (859/906) | 95%(1066/1128) | ||
| Night–time | 5% (109/2034) | 5% (47/906) | 5% (962/1128) | ||
| Antibiotic prophylaxis, % (n/N) | 80% (1.628/2.034) | 73% (662/906) | 84% (956/1.127) | 0.005 | 11% [8 to 15%] |
| Mean arterial pressure, mmHg | 82 [74 to 92] | 84 [76 to 94] | 80 [72 to 90] | < 0.001 | 4 [4 to 7] |
| Heart rate, beats∙min | 72 [63 to 82] | 73 [64 to 82] | 72 [62 to 83] | 0.276 | 1 [3 to 11] |
| Intraop. procedures, % (n/N) | |||||
| Epidural anesthesia | 12% (237/2.034) | 3% (25/906) | 19% (212/1128) | < 0.001 | 16% [13 to 18%] |
| Opioid | < 0.001 | ||||
| Short–acting | 18% (367/2.015) | 22% (193/900) | 16% (174/1.115) | ||
| Long–acting | 70% (1410/2.015) | 62% (561/900) | 76% (849/1.115) | ||
| Both | 12% (238/2.015) | 16% (146/900) | 8% (92/1.115) | ||
| Neuromuscular Blockade | 97% (1965/2.028) | 97% (876/903) | 97% (1089/1.125) | 0.887 | 0.2% [0.1 to 1%] |
| Neuromuscular Monitoring | 23% (474/2.032) | 25% (230/906) | 22% (244/1.126) | 0.055 | 3% [0 to 7%] |
| Neuromuscular Reversal | 41% (827/2.024) | 49% (437/901) | 35% (390/1.123) | < 0.001 | 14% [9 to 18%] |
| TIVA | 10% (211/2.027) | 11% (102/902) | 10% (109/1.125) | 0.266 | 1% [1 to 4%] |
| Transfusion | 6% (113/2.034) | 1% (13/906) | 9% (100/1.128) | < 0.001 | 7% [6 to 9%] |
| Total Fluids (mL∙ kg−1) | 18 [12 to 30] | 15 [13 to 30] | 23 [14 to 26] | < 0.001 | 8 [6 to 10] |
| Crystalloids (mL∙ kg−1) | 17 [12 to 26] | 14 [11 to 21] | 20 [13 to 31] | < 0.001 | 5 [4 to 7] |
| Colloids (mL∙ kg−1) | 7 [3 to 9] | 4 [0 to 7] | 7 [6 to 12] | < 0.001 | 3 [2 to 6] |
Data are presented as median [25th–75th percentile] or % (n/N). For binary and continuous variables risk difference and median difference with 95% confidence intervals in square brackets are reported respectively
Abbreviations: BMI Body mass index, ASA American Society of Anaesthesiologists, ARISCAT Assess Respiratory Risk in Surgical Patients in Catalonia risk index,14,15 Hb Haemoglobin, GI Gastrointestinal, HBP Hepatobiliopancreatic, SpO2 Peripheral oxygen saturation, CI Confidence interval, COPD Chronic Obstructive Pulmonary Disease, OSAS Obstructive sleep apnea sydnrome, TIVA Total Intravenous Anaesthesia
aNeuromuscular disease affecting the respiratory system
bThe same patient may have more than one surgical indication
cUrgency of surgery is defined as elective: surgery that is scheduled in advance because it does not involve a medical emergency, urgent: surgery required within < 48 h, emergent: surgery performed when the patients’ life or well being are threatened
dDuration of surgery is the time between skin incision and closure of the incision
eDuration of anaesthesia is the time between start of induction and tracheal extubation or discharge from operation room if the mechanical ventilation is continued
fDaytime surgery is defined as anaesthesia induction between 8:00 a.m. and 19:59 p.m.