Table 3.
Associations of intraoperative BP variability parameters with postoperative AKI in the SPARK-discovery cohort
| Subgroup, Outcome, and Exposure | Univariable Model | Multivariable Model 1a | Multivariable Model 2b | |||
|---|---|---|---|---|---|---|
| sOR (95% CI) | P Value | Adjusted sOR (95% CI) | P Value | Adjusted sOR (95% CI) | P Value | |
| All SPARK-discovery patientsc | ||||||
| Postoperative AKI | ||||||
| SD | 1.2 (1.16 to 1.25) | <0.001 | 1.11 (1.05 to 1.17) | <0.001 | 1.12 (1.06 to 1.19) | <0.001 |
| Coefficient of variation | 1.39 (1.33 to 1.44) | <0.001 | 1.14 (1.08 to 1.2) | <0.001 | 1.15 (1.08 to 1.22) | <0.001 |
| Average real variability | 1.2 (1.15 to 1.25) | <0.001 | 1.13 (1.08 to 1.18) | <0.001 | 1.13 (1.07 to 1.19) | <0.001 |
| Variation independent of mean | 1.36 (1.3 to 1.41) | <0.001 | 1.13 (1.07 to 1.2) | <0.001 | 1.15 (1.08 to 1.22) | <0.001 |
| Critical AKI | ||||||
| SD | 1.29 (1.19 to 1.41) | <0.001 | 1.14 (1.02 to 1.27) | 0.02 | 1.18 (1.04 to 1.32) | 0.01 |
| Coefficient of variation | 1.59 (1.46 to 1.72) | <0.001 | 1.2 (1.07 to 1.34) | <0.001 | 1.23 (1.09 to 1.39) | <0.001 |
| Average real variability | 1.24 (1.14 to 1.35) | <0.001 | 1.13 (1.03 to 1.25) | 0.01 | 1.13 (1.02 to 1.26) | 0.02 |
| Variation independent of mean | 1.54 (1.42 to 1.67) | <0.001 | 1.19 (1.06 to 1.33) | <0.001 | 1.22 (1.08 to 1.38) | <0.001 |
| In patients with hypotensiond | ||||||
| Postoperative AKI | ||||||
| SD | 1.17 (1.12 to 1.22) | <0.001 | 1.16 (1.09 to 1.23) | <0.001 | 1.17 (1.09 to 1.24) | <0.001 |
| Coefficient of variation | 1.35 (1.29 to 1.42) | <0.001 | 1.2 (1.12 to 1.27) | <0.001 | 1.20 (1.12 to 1.29) | <0.001 |
| Average real variability | 1.19 (1.14 to 1.25) | <0.001 | 1.19 (1.13 to 1.25) | <0.001 | 1.18 (1.11 to 1.25) | <0.001 |
| Variation independent of mean | 1.32 (1.26 to 1.38) | <0.001 | 1.19 (1.12 to 1.27) | <0.001 | 1.20 (1.12 to 1.28) | <0.001 |
| Critical AKI | ||||||
| SD | 1.28 (1.16 to 1.4) | <0.001 | 1.22 (1.08 to 1.36) | <0.001 | 1.24 (1.09 to 1.4) | <0.001 |
| Coefficient of variation | 1.56 (1.42 to 1.71) | <0.001 | 1.27 (1.13 to 1.44) | <0.001 | 1.29 (1.13 to 1.47) | <0.001 |
| Average real variability | 1.23 (1.13 to 1.34) | <0.001 | 1.19 (1.07 to 1.31) | <0.001 | 1.17 (1.04 to 1.31) | 0.01 |
| Variation independent of mean | 1.51 (1.38 to 1.65) | <0.001 | 1.26 (1.12 to 1.42) | <0.001 | 1.28 (1.12 to 1.46) | <0.001 |
| In patients without hypotensiond | ||||||
| Postoperative AKI | ||||||
| SD | 1.11 (1.01 to 1.22) | 0.03 | 1.00 (0.89 to 1.11) | 0.95 | 1.02 (0.90 to 1.15) | 0.79 |
| Coefficient of variation | 1.12 (1.00 to 1.25) | 0.04 | 1.00 (0.88 to 1.14) | 0.94 | 1.03 (0.89 to 1.19) | 0.71 |
| Average real variability | 1.00 (0.90 to 1.11) | 0.96 | 0.94 (0.84 to 1.05) | 0.31 | 0.97 (0.85 to 1.10) | 0.62 |
| Variation independent of mean | 1.12 (1.01 to 1.24) | 0.04 | 1.00 (0.88 to 1.14) | 0.96 | 1.03 (0.89 to 1.18) | 0.72 |
| Critical AKI | ||||||
| SD | 0.96 (0.74 to 1.23) | 0.75 | 0.81 (0.60 to 1.09) | 0.18 | 0.83 (0.58 to 1.16) | 0.29 |
| Coefficient of variation | 1.01 (0.76 to 1.33) | 0.97 | 0.82 (0.58 to 1.15) | 0.26 | 0.85 (0.57 to 1.26) | 0.44 |
| Average real variability | 0.91 (0.68 to 1.18) | 0.49 | 0.84 (0.61 to 1.13) | 0.27 | 0.86 (0.60 to 1.2) | 0.39 |
| Variation independent of mean | 1.00 (0.75 to 1.31) | 0.99 | 0.82 (0.58 to 1.14) | 0.24 | 0.85 (0.57 to 1.24) | 0.41 |
All variability parameters were included in the regression model as continuous variables, and standardized odds ratios per 1 SD higher are presented; the 1-SD values were 4.2 mm Hg, 4.7%, 2.8 mm Hg/measurement, and 0.03 unit for SD, coefficient of variation, average real variability, and variation independent of mean parameters, respectively. SPARK, simple postoperative AKI risk; sOR, standardized odds ratio.
Multivariable model 1 was adjusted for preoperative risk factors: age, sex, eGFR (continuous, ml/min per 1.73 m2), diabetes mellitus, surgery duration (continuous, hours), emergency operation, usage of renin-angiotensin-aldosterone system blockades, dipstick albuminuria, anemia (<13 g/dl for male, <12 g/dl for female), hypoalbuminemia (<3.5 g/dl), hyponatremia (<135 mEq/L), and hypotensive variables, including area under curve (minutes multiplied by subtraction [mm Hg×min]) of mean arterial pressure <65 mm Hg, and the lowest mean arterial pressure value during surgery, without missing values.
In multivariable model 2, estimated blood loss (ml) and red blood cell transfusion amount (ml) during surgery were added to multivariable model 1. The model was constructed with 32,446 patients with existing estimated blood loss records.
The numbers of postoperative AKI events were 2230 (5%) and the number of critical AKI events was 443 (1%) in the SPARK-discovery cohort with 45,520 patients.
Subgroups were divided according to presence of any mean arterial pressure <65 mm Hg during surgery. The subgroup with hypotension included 32,101 patients with 1827 (6%) AKI and 383 (1%) critical AKI events, respectively. The subgroup without hypotension included 13,419 patients with 403 (3%) AKI and 60 (0%) critical AKI events, respectively.