Characteristics of full study cohort and complication positive patients
| Full cohort (n=12 898) | NSQIP+ (n=2885) | PSI+ (n=2415) | Standardised difference* | |
| Age (mean, SD) | 59.8 (16.9) | 64.2 (16.2) | 65.9 (16.0) | 0.11 |
| Female (%) | 55.7 | 54.8 | 51.4 | 0.07 |
| Elective admission (%) | 69.2 | 57 | 56 | 0.02 |
| Length of stay in days (mean, SD) | 7.3 (12.8) | 16.0 (20.3) | 18.7 (21.5) | 0.13 |
| Comorbidities | ||||
| Diabetes (%) | 15.1 | 19.9 | 19.7 | 0.01 |
| Smoker (%) | 19.5 | 22.1 | 21.7 | 0.01 |
| Dyspnoea (%) | 7.7 | 12.2 | 12.5 | 0.01 |
| Functionally dependant (%) | 4.6 | 9.7 | 10 | 0.01 |
| SIRS <48 hours of surgery (%) | 3.2 | 5.3 | 4.5 | 0.04 |
| Sepsis <48 hours of surgery (%) | 1.9 | 4.4 | 4.6 | 0.01 |
| Septic shock <48 hours of surgery (%) | 0.6 | 2 | 2.1 | 0.01 |
| Ventilator dependent (%) | 0.6 | 2 | 2 | 0.00 |
| COPD (%) | 5.7 | 9.6 | 10.9 | 0.04 |
| Ascites (%) | 0.9 | 2.3 | 2.3 | 0.00 |
| Congestive heart failure (%) | 0.8 | 2.4 | 2.7 | 0.02 |
| Hypertension (%) | 41.7 | 52.5 | 53.7 | 0.02 |
| Acute renal failure <24 hours (%) | 0.3 | 1.1 | 1.1 | 0.00 |
| Dialysis (%) | 1.3 | 2.8 | 2.4 | 0.03 |
| Disseminated cancer (%) | 5.6 | 9.5 | 8.7 | 0.03 |
| >10% wt loss (%) | 2.1 | 2.1 | 4.7 | 0.14 |
| Immunosuppressed (%) | 3.6 | 6.7 | 5.7 | 0.04 |
| Bleeding disorder (%) | 3.8 | 7.1 | 7.1 | 0.00 |
| Preoperative transfusions (%) | 1.5 | 4.8 | 4.8 | 0.00 |
| Elixhauser score (mean, SD) | 2.5 (4.9) | 4.3 (6.0) | 4.5 (5.9) | 0.03 |
| ASA score <2 (%) | 32 | 15 | 12.8 | 0.06 |
| Surgical specialty | ||||
| General surgery (%) | 27.3 | 34.4 | 40 | 0.12 |
| Gynaecology (%) | 11.2 | 8.9 | 5.5 | 0.13 |
| Neurosurgery (%) | 9 | 8.6 | 7.3 | 0.05 |
| Orthopaedics (%) | 26.7 | 22.7 | 20.6 | 0.05 |
| Otolaryngology (%) | 6.4 | 3.8 | 4.3 | 0.03 |
| Plastics (%) | 1.8 | 2.2 | 1.7 | 0.04 |
| Thoracic (%) | 3.5 | 2.7 | 4.2 | 0.08 |
| Urology (%) | 6.4 | 5.1 | 4 | 0.05 |
| Vascular (%) | 7.8 | 11.6 | 12.4 | 0.02 |
*Standardised differences of 0.1 or less represent non-substantial differences.
ASA, American Society of Anesthesiology; COPD, chronic obstructive pulmonary disease; NSQIP, National Surgical Quality Improvement Programme; PSI, patient safety indicator; SIRS, systemic inflammatory response syndrome.