Intraoperative oliguria modifies the association between cardiac power index and postoperative acute kidney injury: a retrospective cohort study

Figures

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  Fig. 1. Flow chart illustrating study inclusion and exclusion criteria. Abbreviations: n, number

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  Fig. 2. Average marginal effect of increased urine output on model‑predicted AKI probability across levels of CPI0.4_AUT The horizontal axis shows CPI0.4_AUT, calculated by summing over time the difference between the threshold value of 0.40 W/m2 and the observed CPI whenever CPI is below this threshold (units: W·min/m2). The vertical axis shows the average marginal effect (AME) on the predicted probability of postoperative AKI associated with increasing urine output by 1 mL/kg/h. Positive AME values indicate that a 1 mL/kg/h higher urine output is associated with a higher model‑predicted probability of postoperative AKI, whereas negative AME values indicate an association with a lower model‑predicted probability of postoperative AKI. The solid line represents the estimated AME, and the shaded area represents its 95% confidence interval. As shown in the figure, AME values are generally below zero across the observed range of CPI0.4_AUT, indicating that a 1 mL/kg/h higher urine output is consistently associated with a change in the model‑predicted probability of AKI toward lower values. Moreover, as CPI0.4_AUT increases (i.e., as CPI remains below the threshold for longer periods and/or…

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  Fig. 3. Average marginal effect of increases in CPI0.4_AUT on model‑predicted AKI probability across levels of urine output The horizontal axis shows urine output (mL/kg/h), and the vertical axis shows the average marginal effect (AME) on the predicted probability of postoperative AKI associated with a 1‑unit increase in CPI0.4_AUT (1 W·min/m2). CPI0.4_AUT was calculated by summing over time the difference between the threshold value of 0.40 W/m2 and the observed CPI whenever CPI is below this threshold. Positive AME values indicate that a 1-unit higher CPI0.4_AUT is associated with a higher model-predicted probability of postoperative AKI, whereas negative AME values indicate an association with a lower model-predicted probability of postoperative AKI. The solid line represents the estimated AME, and the shaded area represents its 95% confidence interval. At low urine output levels (in this cohort, approximately < 0.8 mL/kg/h), AME values are greater than zero, indicating that larger CPI0.4_AUT is associated with a higher model‑predicted probability of AKI. As urine output increases, AME values move toward zero, and at urine outputs of approximately ≥ 0.9 mL/kg/h, the AME estimates are…