Oxygen delivery-guided perfusion for the prevention of acute kidney injury: A randomized controlled trial.

OBJECTIVES: The reduction of postoperative acute kidney injury in patients undergoing cardiopulmonary bypass surgery using an oxygen delivery-guided perfusion strategy (oxygen delivery strategy) for cardiopulmonary bypass management compared with a fixed flow perfusion (conventional strategy) remains controversial. The purpose of this study was to determine whether a oxygen delivery strategy would reduce the incidence of postoperative acute kidney injury in patients undergoing cardiopulmonary bypass surgery. METHODS: We randomly enrolled 300 patients undergoing cardiopulmonary bypass surgery. Patients were randomly assigned to a oxygen delivery strategy (maintaining a oxygen delivery index value >300 mL/min/m2 through pump flow adjustments during cardiopulmonary bypass) or a conventional strategy (a target pump flow was determined on the basis of the body surface area). The primary end point was the development of acute kidney injury. Secondary end points were the red blood cell transfusion rate and number of red blood cell units, intubation time, postoperative length of stay in the intensive care unit and the hospital, predischarge estimated glomerular filtration rate, and hospital mortality. RESULTS: Acute kidney injury occurred in 20 patients (14.6%) receiving the oxygen delivery strategy and in 42 patients (30.4%) receiving the conventional strategy (relative risk, 0.48; 95% confidence interval, 0.30-0.77; P = .002). The secondary end points were not significantly different between strategies. In a prespecified subgroup analysis of patients who had nadir hematocrit less than 23% or body surface area less than 1.40 m2, the oxygen delivery strategy seemed to be superior to the conventional strategy and the existence of quantitative interactions was suggested. CONCLUSIONS: An oxygen delivery strategy for cardiopulmonary bypass management was superior to a conventional strategy with respect to preventing the development of acute kidney injury.

Risk factors for postoperative delirium on oxygen delivery-guided perfusion.

BACKGROUND: Studies have demonstrated the efficacy of oxygen delivery-guided perfusion (ODGP) in preventing postoperative acute kidney injury, but the benefit of ODGP for delirium has not been confirmed. We retrospectively investigated the risk factors for postoperative delirium in patients who underwent ODGP (with oxygen delivery index [DO2i] > 300 mL/min/m2). METHODS: Consecutive patients who underwent on-pump cardiovascular surgery with ODGP from January 2018 to December 2020 were retrospectively analyzed. In addition to examining patients' DO2i during cardiopulmonary bypass (CPB), we quantified the two primary DO2 components-hematocrit (Hct) and pump flow. Delirium was defined based on the Intensive Care Delirium Screening Checklist (ICDSC). Patients were divided into three groups: no delirium (ICDSC score = 0), subsyndromal delirium (ICDSC score = 1-3), and clinical delirium (ICDSC score ≥ 4). RESULTS: Multivariate analysis identified only the number of red blood cell (RBC) units transfused, intubation time, and the cumulative time below the Hct threshold of 25% as predictive factors of postoperative delirium. Although patients with higher ICDSC scores had greater hemodilution during CPB, ODGP resulted in a higher pump flow, and DO2i was maintained above 300 mL/min/m2, with no significant difference between the three groups. CONCLUSIONS: A low Hct level during CPB with ODGP, the number of RBC units transfused, and intubation time were associated with postoperative delirium. Further investigations are needed to determine the ability of ODGP to prevent low Hct during CPB.

Factors influencing activated clotting time following heparin administration for the initiation of cardiopulmonary bypass.

OBJECTIVES: Initiation of cardiopulmonary bypass (CPB) for open-heart surgery requires that heparin be administered and reach an adequate value of activated clotting time (ACT). We previously introduced a new heparin formula that considered the preoperative ACT. In this study, we determined other factors affecting ACT. METHODS: Adult patients who underwent cardiac surgery using CPB were divided into two groups according to their ACT value after the initial administration of heparin during surgery. ACT above 450 s was defined as "Reach", and this group was compared to the "Short" group with ACT below 450 s. RESULTS: The Reach and Short groups included 334 (64.7%) and 182 (35.3%) cases, respectively. Univariate analysis indicated that preoperative heparin use, age ≥ 80 years, New York Heart Association classification 4, white blood cell counts above the higher limit, hematocrit below the lower limit, platelet cell counts below the lower limit, low albumin levels, moderate renal dysfunction, high C-reactive protein levels, high brain natriuretic peptide levels, and moderate deterioration of left ventricular ejection fraction were associated with the effects of heparin. Multivariate analysis revealed that age ≥ 80 years (odds ratio [OR] 2.53, 95% confidence interval [95%CI] 1.41-5.24), New York Heart Association classification 4 (OR = 4.44, 95%CI 1.59-15.35), and platelet count below the lower limit (OR 0.37, 95%CI 0.31-0.85) were associated with the effects of heparin. CONCLUSION: Old age, heart failure, and lower platelet counts affected heparin activity. The dose of heparin should be considered in those patients to reach the target ACT.

Free triiodothyronine (fT3) and B-type natriuretic peptide (BNP) predict in-hospital mortality after valve surgery.

BACKGROUND: Increased B-type natriuretic peptide (BNP) and decreased free triiodothyronine (fT3) are associated with increased mortality after cardiac surgery. However, previous studies have addressed mortality primarily in patients undergoing coronary artery bypass graft, and not in those undergoing valve surgery. We assessed abilities of BNP and fT3 to predict mortality after valve surgery. METHODS: This retrospective study included 1050 consecutive patients who underwent valve surgery with normothermic cardiopulmonary bypass (CPB). Predictors of in-hospital mortality were identified with logistic regression analyses. Cutoff values were determined with receiver operating curve analyses. RESULTS: There were 23 deaths (2.2%). By univariate analyses, fT3, log-transformed BNP (log BNP), cholinesterase, estimated glomerular filtration rate, and albumin were profoundly associated with in-hospital mortality (p < 0.0001 for each). By a multivariate analysis, however, only fT3 and log BNP remained significant (p = 0.0053 and p = 0.0449, respectively). fT3 and log BNP remained significant after adjustment for CPB time, and also after adjustment for the EuroSCORE II or JapanSCORE (p < 0.05 for each). Odds ratio and 95% confidence interval from univariate binary analysis for in-hospital mortality were 7.22 (3.12-17.58) for fT3 ≤ 2.21 pg/mL, 6.01 (2.54-15.77) for BNP ≥ 219 pg/mL, and 9.79 (4.21-22.74) for both combined (p < 0.0001 for each). CONCLUSIONS: fT3 and BNP predict in-hospital mortality after valve surgery, independent of each other, independent of CPB time, and independent of established mortality risk SCOREs. Additions of fT3 and BNP may enhance predictive utilities of established mortality risk SCOREs.

Time-dose response of oxygen delivery during cardiopulmonary bypass predicts acute kidney injury.

OBJECTIVE: Previous studies have reported that nadir oxygen delivery during cardiopulmonary bypass is associated with the occurrence of postoperative acute kidney injury (AKI). However, these measurements only considered the bottom point of the oxygen delivery (DO2) but did not consider the duration of DO2. We aimed to examine whether the time-dose response of DO2 during cardiopulmonary bypass can be used to estimate the risk for postoperative AKI. METHODS: We evaluated 112 patients who underwent cardiac surgeries with cardiopulmonary bypass. We analyzed the perfusion parameters recorded every 20 seconds. To obtain time-dose response of DO2 index (DO2i), the area under the curve was calculated as below the 300 mL/min/m2 threshold, which accounts for depth and duration of cumulative oxygen debt. In addition, the cumulative time below DO2i 300 mL/min/m2 was also calculated. Receiver operating characteristic analysis, univariate regression analysis, and multivariate regression analysis were used to evaluate associations between perioperative variables and postoperative AKI. RESULTS: Patients who developed AKI had larger area under the curve below the 300 mL/min/m2 threshold (1581 vs 632; P < .01) and cumulative time below DO2i 300 mL/min/m2 (34.7 vs 15.3 minutes; P < .01). Nadir DO2i was not significantly different between the non-AKI and AKI groups (263.4 vs 247.0 mL/min/m2; P = .291). CONCLUSIONS: The time-dose response of DO2i during cardiopulmonary bypass is a better indicator than nadir DO2i in evaluating AKI risk. Maintaining DO2i levels >300 mL/min/m2 may result in decreased risk for postoperative AKI.

Continuous renal replacement therapy with a polymethyl methacrylate membrane hemofilter suppresses inflammation in patients after open-heart surgery with cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) induces a complex inflammatory response involving an increase in inflammatory cytokines, called postperfusion syndrome. Previous studies demonstrated that adsorption of the serum cytokines can reduce acute inflammation and improve clinical outcomes. In this study, patients were placed on continuous renal replacement therapy (CRRT) with a polymethyl methacrylate (PMMA) membrane hemofilter immediately after the start of an open-heart surgery with CPB and throughout the postoperative course to prevent postperfusion syndrome. The aim of this study was to assess whether continuous CRRT using a PMMA filter (PMMA-CRRT) could affect cytokine expression and improve perioperative outcomes. We designed a randomized controlled trial, which included 19 consecutive adult patients on maintenance dialysis and 7 consecutive adult patients who were not on maintenance dialysis (NHD group). Patients on maintenance dialysis were randomly divided into two groups: Ten patients who received CRRT with a polysulfone membrane hemofilter (PS group) and nine patients who received CRRT with a PMMA membrane (PMMA group). Blood samples were collected from the radial or brachial artery at five different time points. Comparisons between the PS, PMMA, and NHD groups revealed a significant main effect of time on changes in serum IL-6 and IL-8 concentrations (p < 0.01) and an interaction (p < 0.05) between time and group. Plasma IL-6 and IL-8 levels after surgery were significantly lower in the PMMA group than in the PS group, while other cytokines measured in this study were not significantly different. In addition, clinical outcomes were not significantly different between the groups. The continuous use of PMMA-CRRT throughout the perioperative period suppressed serum IL-6 and IL-8 concentrations, although there were no differences in clinical outcomes.

B-Type Natriuretic Peptide and Hemoglobin are Two Major Factors Significantly Associated With Baseline Cerebral Oxygen Saturation Measured Using the INVOS Oximeter in Patients Undergoing Off-Pump Coronary Artery Bypass Graft Surgery.

OBJECTIVES: To investigate an association between the preoperative plasma B-type natriuretic peptide (BNP) concentration and cerebral regional saturation (rSO2) measured using the INVOS oximeter (Medtronic, Minneapolis, MN). DESIGN: A retrospective data analysis. SETTING: Single university hospital. PARTICIPANTS: Patients undergoing off-pump coronary artery bypass (OPCAB) surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Associations of variables obtained from preoperative blood laboratory tests and transthoracic echocardiography with baseline rSO2 before induction of general anesthesia were investigated using bivariate and multivariate regression analyses in 330 OPCAB patients. With bivariate analyses, age; body size-related variables such as weight and body surface area; hematologic function-related variables such as blood hemoglobin (Hb) concentration and arterial oxygen saturation; renal function-related variables including estimated glomerular filtration rate, creatinine, and blood urea nitrogen; hepatic function-related variables including cholinesterase, albumin, total bilirubin, and alanine aminotransferase; serum electrolytes including sodium, chloride, and phosphorus; BNP or log-transformed BNP; and 13 transthoracic echocardiography variables such as left ventricular ejection fraction highly significantly correlated with baseline rSO2 (p < 0.0001). However, the multiple regression analysis revealed that only BNP and Hb remained major factors significantly associated with baseline rSO2 (p < 0.0001), while estimated glomerular filtration rate, arterial oxygen saturation, and body surface area remained minor factors (p < 0.05). Baseline rSO2 correlated better with log-transformed BNP than with BNP, indicating that rSO2 correlated with BNP in an exponential fashion. CONCLUSIONS: Preoperative BNP and Hb concentrations were 2 major factors associated with INVOS rSO2 in patients undergoing OPCAB.

Brain natriuretic peptide (BNP) may play a major role in risk stratification based on cerebral oxygen saturation by near-infrared spectroscopy in patients undergoing major cardiovascular surgery.

PURPOSE: A previous study reported that low baseline cerebral oxygen saturation (ScO2) (≤50%) measured with near-infrared spectroscopy was predictive of poor clinical outcomes after cardiac surgery. However, such findings have not been reconfirmed by others. We conducted the current study to evaluate whether the previous findings would be reproducible, and to explore mechanisms underlying the ScO2-based outcome prediction. METHODS: We retrospectively investigated 573 consecutive patients, aged 20 to 91 (mean ± standard deviation, 67.1 ± 12.8) years, who underwent major cardiovascular surgery. Preanesthetic baseline ScO2, lowest intraoperative ScO2, various clinical variables, and hospital mortality were examined. RESULTS: Bivariate regression analyses revealed that baseline ScO2 correlated significantly with plasma brain natriuretic peptide concentration (BNP), hemoglobin concentration (Hgb), estimated glomerular filtration rate (eGFR), and left ventricular ejection fraction (LVEF) (p < 0.0001 for each). Baseline ScO2 correlated with BNP in an exponential manner, and BNP was the most significant factor influencing ScO2. Logistic regression analyses revealed that baseline and lowest intraoperative ScO2 values, but not relative ScO2 decrements, were significantly associated with hospital mortality (p < 0.05), independent of the EuroSCORE (p < 0.01). Receiver operating curve analysis of ScO2 values and hospital mortality revealed an area under the curve (AUC) of 0.715 (p < 0.01) and a cutoff value of ≤50.5% for the baseline and ScO2, and an AUC of 0.718 (p < 0.05) and a cutoff value of ≤35% for the lowest intraoperative ScO2. Low baseline ScO2 (≤50%) was associated with increases in intubation time, intensive care unit stay, hospital stay, and hospital mortality. CONCLUSION: Baseline ScO2 was reflective of severity of systemic comorbidities and was predictive of clinical outcomes after major cardiovascular surgery. ScO2 correlated most significantly with BNP in an exponential manner, suggesting that BNP plays a major role in the ScO2-based outcome prediction.