Table 2.
Associations between intraoperative supraphysiological oxygen administration and patient outcomes
| Analysis | Acute kidney injury | Estimate (95% CI) | P value | Myocardial injury | Estimate (95% CI) | P value | Lung injury | Estimate (95% CI) | P value |
|---|---|---|---|---|---|---|---|---|---|
| Primary analysis | 19 207/297 554 (6.5) | 1.26 (1.22 to 1.30) | <0.001 | 8972/320 527 (2.8) | 1.12 (1.07 to 1.17) | <0.001 | 13 789/312 161 (4.4) | 1.14 (1.12 to 1.16) | <0.001 |
| Sensitivity analyses—redefined exposure | |||||||||
| Excluding minutes when SpO2<96% | 19 207/297 554(6.5) | 1.21 (1.18 to 1.25) | <0.001 | 8.972/320 527 (2.8) | 1.09 (1.04 to 1.13) | <0.001 | 13 789/312 161 (4.4) | 1.11 (1.09 to 1.13) | <0.001 |
| Excluding minutes when SpO2<90% | 19 207/297 554 (6.5) | 1.26 (1.22 to 1.30) | <0.001 | 8972/320 527 (2.8) | 1.12 (1.07 to 1.17) | <0.001 | 13 789/312 161 (4.4) | 1.14 (1.12 to 1.16) | <0.001 |
| Redefining excess FIO2 as AUC>0.4 | 19 207/297 554 (6.5) | 1.13 (1.10 to 1.17) | <0.001 | 8972/320 527 (2.8) | 1.08 (1.04 to 1.13) | <0.001 | 13 789/312 161 (4.4) | 1.12 (1.11 to 1.14) | <0.001 |
| Sensitivity analyses—cohort restriction | |||||||||
| Excluding patients with any SpO2<96% | 11 535/197 213 (5.8) | 1.24 (1.19 to 1.30) | <0.001 | 5612/214 642 (2.6) | 1.15 (1.09 to 1.21) | <0.001 | 7274/204 626 (3.6) | 1.10 (1.08 to 1.13) | <0.001 |
| Excluding patients with early mortality | 19 207/297 046 (6.5) | 1.26 (1.22 to 1.30) | <0.001 | 8972/320 266 (2.8) | 1.12 (1.08 to 1.17) | <0.001 | 13 789/307 540 (4.5) | 1.14 (1.12 to 1.16) | <0.001 |
| Excluding patients with missing outcome data | 19 207/186 178 (10.3) | 1.21 (1.17 to 1.25) | <0.001 | 8972/28 987 (31.0) | 1.05 (1.00 to 1.11) | <0.001 | 13 789/312 161 (4.4) | 1.14 (1.12 to 1.16) | <0.001 |
| Excluding patients undergoing cardiac surgery | 18 173/289 398 (6.3) | 1.25 (1.21 to 1.30) | <0.001 | 8972/320 527 (2.8) | 1.12 (1.07 to 1.17) | <0.001 | 12 423/302 347 (4.1) | 1.14 (1.12 to 1.16) | <0.001 |
| Sensitivity analysis—instrumental variable | 19 207/297 554 (6.5) | 1.08 (1.01 to 1.15) | <0.001 | 8972/320 527 (2.8) | 1.29 (1.19 to 1.39) | <0.001 | 13 789/312 161 (4.4) | 0.93 (0.88 to 0.98) | 0.004 |
| Sensitivity analysis—adjusted for surgery duration | 19 207/297 531 (6.5) | 1.14 (1.10 to 1.18) | <0.001 | 8972/320 501 (2.8) | 1.17 (1.11 to 1.22) | <0.001 | 13 785/312.138 (4.4) | 1.14 (1.11 to 1.17) | <0.001 |
| Sensitivity analysis—no intraoperative covariates | 19 207/297 554 (6.5) | 1.39 (1.35 to 1.43) | <0.001 | 8972/320 527 (2.8) | 1.08 (1.04 to 1.13) | <0.001 | 13 789/312 161 (4.4) | 1.20 (1.18 to 1.22) | <0.001 |
| Sensitivity analysis—sIPTW | 19 207/297 554 (6.5) | 1.42 (1.38 to 1.46) | <0.001 | 8972/320 527 (2.8) | 1.19 (1.15 to 1.24) | <0.001 | 13 789/312 161 (4.4) | 1.20 (1.18 to 1.21) | <0.001 |
Estimates (95% confidence intervals) represent odds of acute kidney injury, myocardial injury, and lung injury between 75th and 25th centiles of intraoperative AUCFIO2, and P values represent statistical significance across entire range of AUCFIO2. All analyses were adjusted for age, sex, race, body mass index, ASA status, AHRQ Elixhauser comorbidity index, chronic pulmonary disease, emergency surgery, preoperative serum creatinine, hemoglobin, troponin and lactate concentrations, nitrous oxide exposure, median tidal volume, median intraoperative positive end expiratory pressure, volumes of intraoperative intravenous crystalloid and packed red blood cells administrations, and intraoperative hypotension.
Stabilized weights in sIPTW analysis ranged from 0 to 6.5, with median 1.0 (interquartile range 0.87-1.14).
AHRQ=Agency for Healthcare Research and Quality; ASA=American Society of Anesthesiologists; AUC=area under curve; AUCFIO2=area under the curve of FIO2 above 21% during minutes when corresponding oxygen saturation was >92%; FIO2=fraction of inspired oxygen; sIPTW=stabilized inverse probability treatment weighting; SpO2=arterial hemoglobin oxygen saturation.