Table 3 –
Summary of exposure-mediator, mediator-outcome, and exposure-outcome relationships estimated from univariable and multivariable regression*
| Mediator | Exposure | |||||
|---|---|---|---|---|---|---|
| Intraoperative RBCs | Preoperative anemia | Preoperative hemoglobin | ||||
| Estimate (95% CI) | p-value | Estimate (95% CI) | p-value | Estimate (95% CI) | p-value | |
| Univariable analyses | ||||||
| -Mediator | ||||||
| Intraoperative RBCs | NA | - | 3.45 (3.21, 3.70) | <.001 | 1.61 (1.58, 1.65) | <.001 |
| -Outcome | ||||||
| AKI | 1.14 (1.07, 1.21) | <.001 | 2.64 (2.16, 3.22) | <.001 | 1.26 (1.17, 1.35) | <.001 |
| Hospital length of stay | 1.06 (1.05, 1.06) | <.001 | 1.13 (1.11, 1.16) | <.001 | 1.05 (1.05, 1.06) | <.001 |
| Reoperation | 1.12 (1.06, 1.18) | <.001 | 1.30 (1.09, 1.54) | 0.004 | 1.10 (1.04, 1.18) | 0.002 |
| Vascular complications | 1.06 (0.96, 1.17) | 0.222 | 1.62 (1.18, 2.22) | 0.003 | 1.14 (1.02, 1.28) | 0.025 |
| Multivariable analysis | ||||||
| -Mediator | ||||||
| Intraoperative RBCs | NA | - | 3.11 (2.88, 3.35) | <.001 | 1.57 (1.53, 1.60) | <.001 |
| -Outcome | ||||||
| AKI | 1.04 (0.97, 1.12) | 0.229 | 1.99 (1.58, 2.50) | <.001 | 1.24 (1.14, 1.34) | <.001 |
| Hospital length of stay | 1.03 (1.02, 1.04) | <.001 | 1.07 (1.05, 1.10) | <.001 | 1.03 (1.02, 1.04) | <.001 |
| Reoperation | 1.06 (1.00, 1.13) | 0.044 | 1.14 (0.94, 1.38) | 0.183 | 1.05 (0.98, 1.13) | 0.172 |
| Vascular complications | 0.99 (0.88, 1.12) | 0.886 | 1.24 (0.87, 1.77) | 0.232 | 1.07 (0.94, 1.22) | 0.314 |
Results are from univariable and multivariable models assessing the association between the given mediator/exposures (columns) and the given mediator/outcomes (rows). Intraoperative RBCs was modelled with Poisson regression and estimates are rate ratios associated with preoperative anemia (<12 g/dL in women; <13 g/dL in men) or 1 g/dL decrease in pre-operative hemoglobin below 14 g/dL. AKI, reoperation, and vascular complications were modelled with logistic regression and estimates are odds ratios. Hospital length of stay was modelled with linear regression on the log scale and estimates are for the ratio of geometric means. All multivariable models are adjusted for age, sex, BMI, smoking status, preoperative creatinine, preoperative platelet count, Charlson comorbidity index, kidney disease, diabetes with complications, hypertension, surgery type (i.e. CABG vs. valve), and total cardiopulmonary bypass time as a marker for surgical complexity. Multivariable models in the mediator column include adjustment for preoperative anemia. Models in the exposure columns do not include the mediator variable (i.e. intraoperative RBCs).