Decreased mean perfusion pressure as an independent predictor of acute kidney injury after cardiac surgery

Adverse renal effects associated with cardiopulmonary bypass

Cardiac surgery on cardiopulmonary bypass (CPB) is associated with postoperative renal dysfunction, one of the most common complications of this surgical cohort. Acute kidney injury (AKI) is associated with increased short-term morbidity and mortality and has been the focus of much research. There is increasing recognition of the role of AKI as the key pathophysiological state leading to the disease entities acute and chronic kidney disease (AKD and CKD). In this narrative review, we will consider the epidemiology of renal dysfunction after cardiac surgery on CPB and the clinical manifestations across the spectrum of disease. We will discuss the transition between different states of injury and dysfunction, and, importantly, the relevance to clinicians. The specific facets of kidney injury on extracorporeal circulation will be described and the current evidence evaluated for the use of perfusion-based techniques to reduce the incidence and mitigate the complications of renal dysfunction after cardiac surgery.

Hemodynamic Determinants of Cardiac Surgery-Associated Acute Kidney Injury

OBJECTIVES

Examine the: 1) relative role of hemodynamic determinants of acute kidney injury (AKI) obtained in the immediate postcardiac surgery setting compared with established risk factors, 2) their predictive value, and 3) extent mediation via central venous pressure (CVP) and mean arterial pressure (MAP).

DESIGN

Retrospective observational study. The main outcome of the study was moderate to severe AKI, per kidney disease: improving global outcomes, within 14 days of surgery.

SETTING

U.S. academic medical center.

PATIENTS

Adult patients undergoing cardiac surgery between January 2000 and December 2019 (n = 40,426) in a single U.S.-based medical center. Pulmonary artery catheter measurements were performed at a median of 102 minutes (11, 132) following cardiopulmonary bypass discontinuation.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

The median age of the cohort was 67 years (58, 75), and 33% were female; 70% had chronic hypertension, 29% had congestive heart failure, and 3% had chronic kidney disease. In a multivariable model, which included comorbidities and traditional intraoperative risk factors, CVP (p < 0.0001), heart rate (p < 0.0001), cardiac index (p < 0.0001), and MAP (p < 0.0001), were strong predictors of AKI, and superseded factors such as surgery type and cardiopulmonary bypass duration. The cardiac index had a significant interaction with heart rate (p = 0.026); a faster heart rate had a differentiating effect on the relationship of cardiac index with AKI, where a higher heart rate heightened the risk of AKI primarily in patients with low cardiac output. There was also significant interaction observed between CVP and MAP (p = 0.009); where the combination of elevated CVP and low MAP had a synergistic effect on AKI incidence.

CONCLUSIONS

Hemodynamic factors measured within a few hours of surgery showed a strong association with AKI. Furthermore, determinants of kidney perfusion, namely CVP and arterial pressure are interdependent; as are constituents of stroke volume, that is, cardiac output and heart rate.

Organ perfusion pressure at admission and clinical outcomes in patients hospitalized for acute heart failure

AIMS

Hypoperfusion portends adverse outcomes in acute heart failure (AHF). The gradient between end-organ inflow and outflow pressures may more closely reflect hypoperfusion than mean arterial pressure (MAP) alone. The aim of this study was to investigate organ perfusion pressure (OPP), calculated as MAP minus central venous pressure (CVP), as a prognostic marker in AHF.

METHODS AND RESULTS

The Sodium NItroPrusside Treatment in Acute Heart Failure (SNIP)-AHF study was a multicentre retrospective cohort study of 200 consecutive patients hospitalized for AHF treated with sodium nitroprusside. Only patients with both MAP and invasive CVP data available from the SNIP-AHF cohort were included in this analysis. The primary endpoint was to assess OPP as a predictor of worsening heart failure (WHF), defined as the worsening of signs and symptoms of heart failure leading to intensification of therapy at 48 h. One hundred and forty-six patients fulfilling the inclusion criteria were included [mean age: 61.1 ± 13.5 years, 32 (21.9%) females; mean body mass index: 26.2 ± 11.7 kg/m2; mean left ventricular ejection fraction: 23.8%±11.4%, mean MAP: 80.2 ± 13.2 mmHg, and mean CVP: 14.0 ± 6.1 mmHg]. WHF occurred in 14 (9.6%) patients. At multivariable models including hemodynamic variables (OPP, shock index, and CVP), OPP at admission was the best predictor of WHF at 48 h [OR 0.91 (95% confidence interval 0.86-0.96), P-value = 0.001] with an optimal cut-off value of 67.5 mmHg (specificity 47.3%, sensitivity 100%, and AUC 0.784 ± 0.054). In multivariable models, including univariable significant parameters available at first bedside assessment, namely New York Heart Association functional class, OPP, shock index, CVP, and left ventricular end-diastolic diameter, OPP consistently and significantly predicted WHF at 48 h.

CONCLUSION

In this retrospective analysis on patients hospitalized for AHF treated with sodium nitroprusside, on-admission OPP significantly predicted WHF at 48 h with high sensitivity.

Comparison of various surrogate markers for venous congestion in predicting acute kidney injury following cardiac surgery: A cohort study

BACKGROUND

Venous congestion has been demonstrated to increase the risk of acute kidney injury (AKI) after cardiac surgery. Although many surrogate markers for venous congestion are currently used in clinical settings, there is no consensus on which marker is most effective in predicting AKI.

METHODS

We evaluated various markers of venous congestion, including central venous pressure (CVP), inferior vena cava (IVC) diameter, portal pulsatility fraction (PPF), hepatic vein flow pattern (HVF), intra-renal venous flow pattern (IRVF), and venous excess ultrasound grading score (VExUS) in adult patients undergoing cardiac surgery to compare their ability in predicting AKI.

RESULTS

Among the 230 patients enrolled in our study, 53 (23.0%) developed AKI, and 11 (4.8%) required continuous renal replacement therapy (CRRT). Our multivariate logistic analysis revealed that IRVF, PPF, HVF, and CVP were significantly associated with AKI, with IRVF being the strongest predictor (odds ratio [OR] 2.27; 95% confidence interval [CI], 1.38-3.73). However, we did not observe any association between these markers and CRRT.

CONCLUSION

Venous congestion is associated with AKI after cardiac surgery, but not necessarily with CRRT. Among the markers tested, IRVF exhibits the strongest correlation with AKI.

Assessment of Individualized Mean Perfusion Pressure Targets for the Prevention of Cardiac Surgery-Associated Acute Kidney Injury-The PrevHemAKI Randomized Controlled Trial

BACKGROUND

Retrospective studies support that mean perfusion pressure (MPP) deficit in cardiac surgery patients is associated with a higher incidence of acute kidney injury (CS-AKI). The aim of our study was to apply an algorithm based on MPP in the postoperative period to determine whether management with an individualized target reduces the incidence of CS-AKI.

METHODS

Randomized controlled trial of patients undergoing cardiac surgery with extracorporeal circulation. Adult patients submitted to valve replacement and/or bypass surgery with a high risk of CS-AKI evaluated by a Leicester score >30 were randomized to follow a target MPP of >75% of the calculated baseline or a standard hemodynamic management during the first postoperative 24 h.

RESULTS

Ninety-eight patients with an eGFR of 54 mL/min were included. There were no differences in MAP and MPP in the first 24 h between the randomized groups, although a higher use of noradrenaline was found in the intervention arm (38.78 vs. 63.27, p = 0.026). The percentage of time with MPP < 75% of measured baseline was similar in both groups (10 vs. 12.7%, p = 0.811). MAP during surgery was higher in the intervention group (73 vs. 77 mmHg, p = 0.008). The global incidence of CS-AKI was 36.7%, being 38.6% in the intervention group and 34.6% in the control group (p = 0.40). There were no differences in extrarenal complications between groups as well.

CONCLUSION

An individualized hemodynamic management based on MPP compared to standard treatment in cardiac surgery patients was safe but did not reduce the incidence of CS-AKI in our study.

Dilemmas of Adopting Goal-Directed Perfusion in Extracorporeal Circulation: A Narrative Review

OBJECTIVE

Extracorporeal circulation (ECC) is generally based on standards established in the last decade. In recent years, a concept of perfusion management during ECC, goal-directed perfusion (GDP), has emerged to create optimal conditions for oxygen delivery and extraction, initiated by Rannuci et al. The aim of the present work was to determine whether the ECC procedure can truly be optimized with the current state of knowledge and understanding of human physiology.

METHODS

Discussed articles from 2017 to 2022 were selected from the MEDLINE (PubMed) database using the keywords "cardiopulmonary bypass" AND "cardiac surgery" AND "oxygen delivery" with the conditions of "clinical trial" OR "randomized controlled trial."

RESULTS

The concept of GDP is an attempt to reproduce the physiological conditions of tissue respiration during ECC. Published articles, also due to their retrospective nature, are based on standards and recommendations that do not fully fit the field of physiological circulation. There are still insufficient tools to assess the relationship between volemia, perfusion pressure, and pump performance. Limitations include indications for vasoactive drugs. Methodology has rarely taken into account the period of starting and stopping the heart-lung machine, the most pronounced periods of circulatory destabilization with reduced oxygen delivery.

CONCLUSIONS

Problems associated with ECC such as acute kidney injury, liver failure, vasoplegic syndrome, and others must await its resolution. The use of advanced monitoring technology and data engineering may allow the development of baseline hemodynamic models, which may make the ECC procedure more physiologic and thus improve the safety of the procedure.

Effect of preoperative risk on the association between intraoperative hypotension and postoperative acute kidney injury in cardiac surgery

BACKGROUND

Acute kidney injury (AKI), a common and severe complication after cardiac surgery, has been demonstrated to be associated with intraoperative hypotension (IOH). The reproducibility of this finding and whether preoperative risk modifies the association remain unclear. We hypothesised that the relationship between IOH and AKI after cardiac surgery varies by preoperative risk.

METHODS

We conducted a single-centre, retrospective cohort study to analyse the association between IOH and postoperative AKI by stratifying patients using preoperative risk factors. IOH was defined as a mean arterial pressure (MAP) of less than 65 mmHg and characterised by the cumulative duration and area under the curve (AUC).

RESULTS

Ten variables could be identified as risk factors: age, smoking status, NYHA III/Ⅳ, emergency surgery, peripheral vascular disease, cerebrovascular disease, heart failure, hypertension, previous cardiac surgery, and NT-proBNP concentration. The risk prediction model divided the patients into three equal-sized preoperative risk groups. Low-risk patients demonstrated no association between AKI and IOH of any severity, while high-risk patients demonstrated a statistically significant association between AKI and IOH with a cumulative duration greater than 104 min (adjusted odds ratio [OR]: 2.27, 95% confidence interval [CI]: 1.10-4.74; and adjusted OR: 3.63, 95% CI: 1.77-7.58) and an AUC greater than 905 mmHg min (adjusted OR: 2.08, 95% CI: 1.01-4.36; and adjusted OR: 4.00, 95% CI: 1.95-8.43).

CONCLUSION

IOH is a significant independent risk factor for AKI after cardiac surgery. Patients with higher baseline risk showed a more prominent relationship between IOH and postoperative AKI than low-risk patients.

Severe fluctuation in mean perfusion pressure is associated with increased risk of in-hospital mortality in critically ill patients with central venous pressure monitoring: A retrospective observational study

BACKGROUND

The mean perfusion pressure (MPP) was recently proposed to personalize tissue perfusion pressure management in critically ill patients. Severe fluctuation in MPP may be associated with adverse outcomes. We sought to determine if higher MPP variability was correlated with increased mortality in critically ill patients with CVP monitoring.

METHODS

We designed a retrospective observational study and analyzed data stored in the eICU Collaborative Research Database. Validation test was conducted in MIMIC-III database. The exposure was the coefficient of variation (CV) of MPP in the primary analyses, using the first 24 hours MPP data recorded within 72 hours in the first ICU stay. Primary endpoint was in-hospital mortality.

RESULTS

A total of 6,111 patients were included. The in-hospital mortality of 17.6% and the median MPP-CV was 12.3%. Non-survivors had significantly higher MPP-CV than survivors (13.0% vs 12.2%, p<0.001). After accounting for confounders, the highest MPP-CV in decile (CV > 19.2%) were associated with increased risk of hospital mortality compared with those in the fifth and sixth decile (adjusted OR: 1.38, 95% Cl: 1.07-1.78). These relationships remained remarkable in the multiple sensitivity analyses. The validation test with 4,153 individuals also confirmed the results when MPP-CV > 21.3% (adjusted OR: 1.46, 95% Cl: 1.05-2.03).

CONCLUSIONS

Severe fluctuation in MPP was associated with increased short-term mortality in critically ill patients with CVP monitoring.

Intraoperative Urine Oxygen in Cardiac Surgery and 12-Month Outcomes

Low intraoperative urinary oxygen during cardiac surgery is associated with increased risk of poor 12-month outcomes. With decreasing urinary oxygen thresholds, the risk of poor 12-month outcomes increases.

Provisional Decision-Making for Perioperative Blood Pressure Management: A Narrative Review

Blood pressure (BP) is a basic determinant for organ blood flow supply. Insufficient blood supply will cause tissue hypoxia, provoke cellular oxidative stress, and to some extent lead to organ injury. Perioperative BP is labile and dynamic, and intraoperative hypotension is common. It is unclear whether there is a causal relationship between intraoperative hypotension and organ injury. However, hypotension surely compromises perfusion and causes harm to some extent. Because the harm threshold remains unknown, various guidelines for intraoperative BP management have been proposed. With the pending definitions from robust randomized trials, it is reasonable to consider observational analyses suggesting that mean arterial pressures below 65 mmHg sustained for more than 15 minutes are associated with myocardial and renal injury. Advances in machine learning and artificial intelligence may facilitate the management of hemodynamics globally, including fluid administration, rather than BP alone. The previous mounting studies concentrated on associations between BP targets and adverse complications, whereas few studies were concerned about how to treat and multiple factors for decision-making. Hence, in this narrative review, we discussed the way of BP measurement and current knowledge about baseline BP extracting for surgical patients, highlighted the decision-making process for BP management with a view to providing pragmatic guidance for BP treatment in the clinical settings, and evaluated the merits of an automated blood control system in predicting hypotension.

Postoperative Acute Kidney Injury in Williams Syndrome Compared With Matched Controls

OBJECTIVES

Cardiovascular manifestations occur in over 80% of Williams syndrome (WS) patients and are the leading cause of morbidity and mortality. One-third of patients require cardiovascular surgery. Renal artery stenosis (RAS) is common in WS. No studies have assessed postoperative cardiac surgery-related acute kidney injury (CS-AKI) in WS. Our objectives were to assess if WS patients have higher risk of CS-AKI postoperatively than matched controls and if RAS could contribute to CS-AKI.

DESIGN

This was a retrospective study of all patients with WS who underwent cardiac surgery at our center from 2010 to 2020. The WS study cohort was compared with a group of controls matched for age, sex, weight, and surgical procedure.

SETTING

Patients underwent cardiac surgery and postoperative care at Lucile Packard Children's Hospital Stanford.

PATIENTS

There were 27 WS patients and 43 controls (31% vs 42% female; p = 0.36). Median age was 1.8 years (interquartile range [IQR], 0.7-3.8 yr) for WS and 1.7 years (IQR, 0.8-3.1 yr) for controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Postoperative hemodynamics, vasopressor, total volume input, diuretic administration, and urine output were collected in the first 72 hours. Laboratory studies were collected at 8-hour intervals. Multivariable analysis identified predictors of CS-AKI.Controlled for renal perfusion pressure (RPP) and vasoactive inotrope score (VIS), compared with controls, the odds ratio (OR) of CS-AKI in WS was 4.2 (95% CI, 1.1-16; p = 0.034). Higher RPP at postoperative hours 9-16 was associated with decreased OR of CS-AKI (0.88 [0.8-0.96]; p = 0.004). Increased VIS at hour 6 was associated with an increased OR of CS-AKI (1.47 [1.14-1.9]; p = 0.003). Younger age was associated with an increased OR of CS-AKI (1.9 [1.13-3.17]; p = 0.015).

CONCLUSIONS

The OR of CS-AKI is increased in pediatric patients with WS compared with controls. CS-AKI was associated with VIS at the sixth postoperative hour. Increases in RPP and mean arterial pressure were associated with decreased odds of CS-AKI.