Table 1. Baseline Features from Patient Cohorts With and Without Inpatient SSI.
| Without SSI (N=684; 80.4%) | With SSI (N=167; 19.6%) | p Value | |
|---|---|---|---|
| Demographics | |||
| Age, y, mean, (95% CI) | 56.2 (55.1-57.3) | 57.5 (55.5-59.5) | 0.29 |
| Male sex | 0.81 | ||
| n (%) | 247 (36.1) | 62 (37.1) | |
| 95% CI | 0.33-0.40 | 0.30-0.45 | |
| Pre-operative labs | |||
| Hemoglobin, g/dL, mean, (95% CI) | 12.7 (12.6-12.9) | 12.1 (11.6-12.6) | <0.001 |
| Total protein, g/dL, mean, (95% CI) | 6.8 (6.7-6.9) | 6.7 (6.4-7.0) | 0.82 |
| Albumin, g/dL, mean, (95% CI) | 4.1 (4.0-4.2) | 3.8 (3.6-4.0) | 0.002 |
| Blood urea nitrogen, mg/dL, mean, (95% CI) | 12.4 (11.4-13.3) | 11.2 (8.9-13.4) | 0.29 |
| Creatinine, mg/dL, mean, (95% CI) | 3.3 (2.9-3.6) | 2.2 (1.7-2.8) | 0.006 |
| C-reactive protein, mg/L, mean, (95% CI) | 2.7 (2.0-3.4) | 5.5 (3.4-7.6) | 0.002 |
| Platelet count, 103/uL, mean, (95% CI) | 236 (226-246) | 257 (230-283) | 0.097 |
| WBC count, 103/uL, mean, (95% CI) | 8.2 (7.8-8.6) | 8.9 (8.0-9.8) | 0.15 |
| PT, seconds, mean, (95% CI) | 14.3 (13.5-15.1) | 15.7 (13.4-18) | 0.15 |
| aPTT, seconds, mean, (95% CI) | 34.5 (33.3-35.6) | 37.7 (34.0-41.4) | 0.036 |
| Procedure-related | |||
| Duration of surgery, minutes, mean, (95% CI) | 253 (244-262) | 312 (289-335) | <0.001 |
| Wound class, n (%) | <0.001 | ||
| Clean | 135 (19.7) | 12 (7.2) | |
| Clean-contaminated | 497 (72.7) | 131 (78.4) | |
| Contaminated | 21 (3.1) | 7 (4.2) | |
| Dirty | 31 (4.5) | 17 (10.2) | |
| Type of operation, n (%) | <0.001 | ||
| Abdominal wall | 44 (6.4) | 3 (1.8) | |
| Gastroduodenum | 27 (3.9) | 4 (2.4) | |
| Gall bladder/bile duct | 31 (4.5) | 4 (2.4) | |
| Liver | 101 (14.8) | 19 (11.4) | |
| Spleen/adrenal gland & other | 29 (4.2) | 4 (2.4) | |
| Small bowel | 35 (5.1) | 18 (10.8) | |
| Kidney | 179 (26.2) | 23 (13.8) | |
| Vascular | 50 (7.3) | 6 (3.6) | |
| Esophagus | 75 (11.0) | 25 (15.0) | |
| Large bowel | 69 (10.1) | 35 (21.0) | |
| Pancreas | 44 (6.4) | 26 (15.6) | |
| Emergency surgery | 0.45 | ||
| n (%) | 149 (21.8) | 41 (24.6) | |
| 95% CI | 0.19-0.25 | 0.18-0.32 | |
| Kidney or liver transplantation | 0.003 | ||
| n (%) | 187 (29.2) | 29 (17.8) | |
| 95% CI | 0.26-0.33 | 0.12-0.25 | |
| Ostomy created | 0.023 | ||
| n (%) | 40 (5.8) | 18 (10.8) | |
| 95% CI | 0.04-0.08 | 0.07-0.16 | |
| Blood transfusion peri-op | 0.017 | ||
| n (%) | 146 (21.4) | 50 (30.1) | |
| 95% CI | 0.18-0.25 | 0.23-0.38 | |
| Risk factors | |||
| Smoking | 0.12 | ||
| n (%) | 287 (42.0) | 59 (35.3) | |
| 95% CI | 0.38-0.46 | 0.28-0.43 | |
| Diabetes mellitus type I or II | 0.88 | ||
| n (%) | 83 (12.2) | 21 (12.6) | |
| 95% CI | 0.10-0.15 | 0.08-0.19 | |
| Chronic lung disease | 0.063 | ||
| n (%) | 58 (8.5) | 22 (13.2) | |
| 95% CI | 0.07-0.11 | 0.08-0.19 | |
| Systemic corticosteroid use | 0.23 | ||
| n (%) | 79 (11.6) | 25 (15.0) | |
| 95% CI | 0.09-0.14 | 0.10-0.21 | |
| Chemotherapy in 3 months pre-op | 0.83 | ||
| n (%) | 46 (6.7) | 12 (7.2) | |
| 95% CI | 0.05-0.09 | 0.04-0.12 | |
| Radiotherapy in 3 months pre-op | 0.97 | ||
| n (%) | 12 (1.8) | 3 (1.8) | |
| 95% CI | 0.01-0.03 | 0.00-0.05 | |
| Ascites present | 0.014 | ||
| n (%) | 16 (2.3) | 10 (6.0) | |
| 95% CI | 0.01-0.04 | 0.03-0.11 | |
| Infection (non-SSI) at intake | 0.33 | ||
| n (%) | 75 (11.0) | 14 (8.4) | |
| 95% CI | 0.09-0.14 | 0.05-0.14 | |
| Alcohol use | 0.71 | ||
| n (%) | 311 (47.1) | 70 (45.5) | |
| 95% CI | 0.43-0.51 | 0.37-0.54 | |
| Alcohol quantity, units per week, mean, (95% CI) | 4.5 (3.8-5.1) | 5.2 (3.5-6.9) | 0.34 |
| ASA score, n (%) | 0.29 | ||
| ASA 1 | 76 (11.1) | 15 (9.0) | |
| ASA 2 | 309 (45.2) | 80 (47.9) | |
| ASA 3 | 280 (40.9) | 67 (40.1) | |
| ASA 4 | 19 (2.8) | 4 (2.4) | |
| ASA 5 | 0 (0.0) | 1 (0.6) | |
| BMI, n (%) | 0.65 | ||
| Underweight | 19 (2.8) | 6 (3.6) | |
| Normal | 317 (46.3) | 67 (40.1) | |
| Overweight | 220 (32.2) | 59 (35.3) | |
| Class 1 obesity | 80 (11.7) | 20 (12.0) | |
| Class 2 obesity | 20 (2.9) | 8 (4.8) | |
| Class 3 obesity | 8 (1.2) | 2 (1.2) | |
| Outcomes | |||
| Length of stay, d, mean, (95% CI) | 15.0 (13.8-16.2) | 24.9 (22.0-27.8) | <0.001 |
| 30 day mortality | 0.036 | ||
| n (%) | 16 (2.3) | 9 (5.4) | |
| 95% CI | 0.01-0.04 | 0.02-0.10 | |
| In-hospital mortality | 0.004 | ||
| n (%) | 25 (3.7) | 15 (9.0) | |
| 95% CI | 0.02-0.05 | 0.05-0.14 |
aPTT, activated partial thromboplastin time; ASA, American Society of Anesthesiologists; PT, prothrombin time; WBC, white blood cell