External Validation and Updating of the Cardiac Surgery Score for Prediction of Mortality in a Cardiac Surgery Intensive Care Unit.

OBJECTIVE: To externally validate the predictive performance of the logistic and additive Cardiac Surgery Score (CASUS), a postoperative severity of illness score designed specifically for prediction of mortality in the cardiac surgery intensive care unit. DESIGN: A retrospective analysis of prospectively collected data between July 1, 2012, and September 30, 2015. SETTING: Single university cardiac surgery intensive care unit in Canada. PARTICIPANTS: Consecutive adult patients (n = 4,519) admitted to the intensive care unit after cardiac surgery. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: The mortality predicted by logistic CASUS was calculated for each patient on admission day 0 and postoperative days 2, 4, 7, and 10 using the original model equation. The mortality predicted by additive CASUS was determined on each day with separate logistic regression models, using the total score as a single variable. The observed mortality was 1.8%. Logistic CASUS overestimated mortality by 78%, 59%, 51%, 52%, and 29% on days 0, 2, 4, 7, and 10, respectively. After model updating with logistic calibration, logistic CASUS consistently provided estimates of death comparable with the observed mortality, as determined with the Hosmer-Lemeshow goodness-of-fit test. The stability of those estimates was confirmed by bootstrapping. Similar calibration results were obtained with additive CASUS. Logistic and additive CASUS had good discrimination with areas under the receiver operating characteristic curve greater than 0.7 on each study day. CONCLUSIONS: Recalibrated logistic CASUS reliably predicts mortality in the intensive care unit after cardiac surgery. Logistic regression models derived from additive CASUS perform as well as logistic CASUS.

Ischemic and bleeding outcomes after coronary artery bypass grafting among patients initially treated with a P2Y12 receptor antagonist for acute coronary syndromes: Insights on timing of discontinuation of ticagrelor and clopidogrel prior to surgery.

BACKGROUND: Clinical outcomes in acute coronary syndrome patients treated with P2Y12 inhibitors who require urgent coronary artery bypass grafting (CABG) have not been well studied. METHODS: We examined clinical outcomes in acute coronary syndrome patients in relation to the timing of CABG following P2Y12 inhibitor discontinuation (<72 h, 72 h to five days, >5 days). The primary ischemic outcome was a composite of death, reinfarction, need for revascularization, or stroke. The primary safety outcome was bleeding of at least moderate severity as defined by a Universal Definition of Perioperative Bleeding class ≥2. RESULTS: Among 508 patients (95 ticagrelor, 413 clopidogrel), the timing of CABG following P2Y12 inhibitor discontinuation was <72 h in 32.1%, 72 h to five days in 23.2% and >5 days in 44.7%. Compared with CABG within 72 h, CABG 72 h to five days (adjusted odds ratio (OR) 0.35; 95% confidence interval (CI) 0.14-0.85; p=0.02) but not >5 days (adjusted OR 0.62; 95% CI 0.33-1.16; p=0.14) after P2Y12 inhibitor discontinuation was associated with lower odds of the primary ischemic outcome. Compared with CABG within 72 h, CABG 72 h to five days (adjusted OR 0.38; 95% CI 0.22-0.66; p=0.001) and >5 days (adjusted OR 0.33; 95% CI 0.20-0.53; p<0.001) after P2Y12 inhibitor discontinuation were associated with lower rates of Universal Definition of Perioperative Bleeding class ≥2 bleeding. CONCLUSIONS: CABG within 72 h after P2Y12 inhibitor discontinuation is associated with excess ischemia and bleeding. The rates of ischemic and bleeding events were comparable in patients undergoing CABG 72 h to five days compared with >5 days after P2Y12 inhibitor discontinuation.

Utility of Novel Cardiorenal Biomarkers in the Prediction and Early Detection of Congestive Kidney Injury Following Cardiac Surgery.

Acute Kidney Injury (AKI) in the context of right ventricular failure (RVF) is thought to be largely congestive in nature. This study assessed the utility of biomarkers high sensitivity cardiac troponin T (hs-cTnT), N-Terminal Pro-B-Type Natriuretic Peptide (NT-proBNP), and neutrophil gelatinase-associated lipocalin (NGAL) for prediction and early detection of congestive AKI (c-AKI) following cardiac surgery. This prospective nested case-control study recruited 350 consecutive patients undergoing elective cardiac surgery requiring cardiopulmonary bypass. Cases were patients who developed (1) AKI (2) new or worsening RVF, or (3) c-AKI. Controls were patients free of these complications. Biomarker levels were measured at baseline after anesthesia induction and immediately postoperatively. Patients with c-AKI had increased mean duration of mechanical ventilation and length of stay in hospital and in the intensive care unit (p < 0.01). For prediction of c-AKI, baseline NT-proBNP yielded an area under the curve (AUC) of 0.74 (95% CI, 0.60⁻0.89). For early detection of c-AKI, postoperative NT-proBNP yielded an AUC of 0.78 (0.66⁻0.91), postoperative hs-cTnT yielded an AUC of 0.75 (0.58⁻0.92), and ∆hs-cTnT yielded an AUC of 0.80 (0.64⁻0.96). The addition of baseline creatinine to ∆hs-cTnT improved the AUC to 0.87 (0.76⁻0.99), and addition of diabetes improved the AUC to 0.93 (0.88⁻0.99). Δhs-cTnT alone, or in combination with baseline creatinine or diabetes, detects c-AKI with high accuracy following cardiac surgery.

Association of Frailty and Long-Term Survival in Patients Undergoing Coronary Artery Bypass Grafting.

BACKGROUND: Frailty is increasing in prevalence and poses a formidable challenge for clinicians. The cardiac surgery literature consists primarily of small single-center studies with limited follow-up, and the epidemiological features of frailty remain to be elucidated in long-term follow-up. METHODS AND RESULTS: We conducted a population-based, retrospective, cohort study in Ontario, Canada, between 2008 and 2015. Frailty was defined using the Johns Hopkins Adjusted Clinical Groups frailty indicator (a multidimensional instrument validated for research using administrative data). The primary outcome was mortality. Mortality rates were calculated using the Kaplan-Meier method. The hazard of death was assessed using a multivariable Cox proportional hazard model. Of 40 083 patients, 8803 (22%) were frail. At 4±2 years of follow-up, age- and sex-standardized mortality rate per 1000 person-years was higher in frail (33; 95% confidence interval, 29-36) compared with nonfrail (22; 95% confidence interval, 19-24) patients. Frailty was associated with an increased risk of long-term mortality (adjusted hazard ratio, 1.20; 95% confidence interval, 1.12-1.28) and greater differences in the survival of patients between 40 and 74 years of age than in those who were ≥85 years old. CONCLUSIONS: Frailty was present in a large proportion of patients undergoing coronary artery bypass grafting and was independently associated with long-term mortality. The adjusted risk of frailty-related death was inversely proportional to age. Our findings highlight the need for more comprehensive preoperative risk stratification models to assist with optimal selection of operative candidates. In addition, we identified the <75 years age group as a potential target for comprehensive preoperative optimization programs, such as cardiac prehabilitation, nutritional augmentation, and psychosocial support.

Prospective External Validation of Three Preoperative Risk Scores for Prediction of New Onset Atrial Fibrillation After Cardiac Surgery.

BACKGROUND: Postoperative atrial fibrillation (POAF) is associated with early and late morbidity and mortality of cardiac surgical patients. Prophylactic treatment of atrial fibrillation (AF) has been recommended to improve outcome in cardiac surgical patients at high risk of developing POAF. Reliable models for prediction of POAF are needed to achieve that goal. This study attempted to externally validate 3 risk models proposed for preoperative prediction of POAF in cardiac surgical patients: the POAF score, the CHA2DS2-VASc score, and the Atrial Fibrillation Risk Index. METHODS: This was a prospective cohort study of 1416 adult patients who underwent nonemergent coronary artery bypass graft and/or valve surgery in a single cardiac surgical center between February 2014 and September 2015. A risk score for each of the 3 prediction models was calculated in each patient. All patients were followed for up to 2 weeks, or until hospital discharge, to observe the primary outcome of new onset AF requiring treatment. Discrimination was assessed using receiver operating characteristic curves. Calibration was assessed using the Pearson χ goodness-of-fit test and calibration plots. Utility of the score to implement AF prophylaxis based on the risk of POAF, in comparison to strategies of treating all patients, or not treating any patients, was assessed via a net benefit analysis. RESULTS: Of the 1416 patients included in this study, 478 had the primary outcome (33.8%). The areas under the receiver operating characteristic curve for prediction of POAF in the population subsets for which the scores were validated were as follows: 0.651 (95% confidence interval [CI], 0.621-0.681) for the POAF score, 0.593 (95% CI, 0.557-0.629) for the CHA2DS2-VASc score (P < .001 versus POAF score, P < .222 versus Atrial Fibrillation Risk Index), and 0.563 (95% CI, 0.522-0.604) for the Atrial Fibrillation Risk Index (P < .001 versus POAF score). The calibration analysis showed that the predictive models had a poor fit between the observed and expected rates of POAF. Net benefit analysis showed that AF preventive strategies based on these scores, and targeting patients with moderate or high risk of POAF, improve decision-making in comparison to preventive strategies of treating all patients. CONCLUSIONS: The 3 prediction scores evaluated in this study have limited ability to predict POAF in cardiac surgical patients. Despite this, they may be useful in preventive strategies targeting patients with moderate or high risk of PAOF in comparison with preventive strategies applied to all patients.

Predicting New-Onset Postoperative Atrial Fibrillation in Cardiac Surgery Patients.

OBJECTIVE: To derive a simple clinical prediction rule identifying patients at high risk of developing new-onset postoperative atrial fibrillation (POAF) after cardiac surgery. DESIGN: Retrospective analysis on prospectively collected observational data. SETTING: A university-affiliated cardiac hospital. PARTICIPANTS: Adult patients undergoing coronary artery bypass grafting and/or valve surgery. INTERVENTIONS: Observation for the occurrence of new-onset postoperative atrial fibrillation. MEASUREMENTS AND MAIN RESULTS: Details on 28 preoperative variables from 999 patients were collected and significant predictors (p<0.2) were inserted into multivariable logistic regression and reconfirmed with recursive partitioning. A total of 305 (30.5%) patients developed new-onset POAF. Eleven variables were associated significantly with atrial fibrillation. A multivariable logistic regression model included left atrial dilatation, mitral valve disease, and age. Coefficients from the model were converted into a simple 7-point predictive score. The risk of POAF per score is: 15.0%, if 0; 20%, if 1; 27%, if 2; 35%, if 3; 44%, if 4; 53%, if 5; 62%, if 6; and 70%, if 7. A score of 4 has a sensitivity of 44% and a specificity of 82% for POAF. A score of 6 has a sensitivity of 11% and a specificity of 97%. Bootstrapping with 5,000 samples confirmed the final model provided consistent predictions. CONCLUSIONS: This study proposed a simple predictive score incorporating three risk variables to identify cardiac surgical patients at high risk of developing new-onset POAF. Preventive treatment should target patients ≥ 65 years with left atrial dilatation and mitral valve disease.

Off-label use of recombinant activated factor VII in surgical and non-surgical patients at 16 Canadian hospitals from 2007 to 2010 (Canadian Registry Report).

PURPOSE: Recombinant activated factor VII (rFVIIa) is a pro-hemostatic drug that is approved for treatment of bleeding in hemophilia patients, but it is frequently used off-label in non-hemophiliacs. The purpose of this study was to determine if the off-label use of rFVIIa is expanding and whether this poses a net harm to patients. METHODS: For this historical cohort study, data were collected on all non-hemophilia patients who received rFVIIa from 2007 to 2010 at 16 Canadian centres, and the pattern of use was examined. Logistic regression was used to determine the prognostic importance of severity of bleeding and the presence of an rFVIIa dose-effect relationship with major adverse events. RESULTS: One thousand three hundred seventy-eight patients received rFVIIa off-label, and 987 (72%) of these patients underwent cardiac surgery. The median [interquartile range] dose was 57 [36-85] µg·kg(-1). Usage increased from 2007 to 2008 (n = 341 and 380, respectively) but decreased in 2009 and 2010 (n = 350 and 307, respectively). Dose of rFVIIa and bleeding severity were associated with measured adverse events (P < 0.05). After adjusting for bleeding severity, dose was not associated with any of the adverse events. CONCLUSIONS: The off-label use of rFVIIa in Canada remains stable. Since severity of bleeding is prognostically important, the benefits of rapidly gaining control of bleeding that is non-responsive to conventional therapies may at times warrant the use of potent hemostatic drugs with established risk profiles, such as rFVIIa.

Off-pump coronary artery bypass grafting does not preserve renal function better than on-pump coronary artery bypass grafting: results of a case-matched study.

OBJECTIVE: Controversy exists regarding the perioperative renal effects of off-pump versus on-pump coronary artery bypass grafting. Large case-matched and randomized comparisons have shown conflicting results. This study focuses on this clinical controversy. METHODS: We studied 5589 consecutive patients from a single center who underwent off-pump or on-pump coronary artery bypass grafting between 2002 and 2010. All preoperative, intraoperative, and postoperative data were prospectively collected. Patients were matched by using a nearest neighbor matching estimation method for average treatment effects, with bias correction (Stata 11.2, StataCorp, College Station, Tex). The matching characteristics were age, gender, body mass index, hypertension, diabetes, peripheral vascular disease, cerebrovascular disease, left ventricular grade, preoperative serum creatinine, operative priority, and Cardiac Anesthesia Risk Evaluation score. RESULTS: The mean patient age was 64.9 ± 10.0 years, and 4387 (78.5%) were male. Mean calculated preoperative creatinine clearance was 82.0 ± 32.6 mL/min. Perioperative mortality was 1.5% with off-pump coronary artery bypass grafting and 1.7% with on-pump coronary artery bypass grafting (P = .6). The mean change in creatinine clearance, from the preoperative value to the lowest postoperative value, was -6.3 ± 14.1 mL/min with off-pump coronary artery bypass grafting versus -5.0 ± 15.5 mL/min with on-pump coronary artery bypass grafting (P = .06). After matching, patients undergoing off-pump coronary artery bypass grafting had a greater creatinine increase and greater loss of creatinine clearance postoperatively compared with patients undergoing on-pump coronary artery bypass grafting (both P < .05). Requirements for de novo postoperative dialysis were equivalent at 2.6% in off-pump coronary artery bypass grafting versus 2.1% in on-pump coronary artery bypass grafting (P = .4). Median postoperative hospital stay was 8 days in both groups (P = .8). CONCLUSIONS: Off-pump coronary artery bypass grafting does not preserve renal function to a greater extent than on-pump coronary artery bypass grafting. In fact, a trend to the reverse exists with no clinically harmful effects.

Comparison of the EuroSCORE and Cardiac Anesthesia Risk Evaluation (CARE) score for risk-adjusted mortality analysis in cardiac surgery.

OBJECTIVE: The European System for Cardiac Operative Risk Evaluation (EuroSCORE) and the Cardiac Anesthesia Risk Evaluation (CARE) score are risk indices designed in the mid-1990 s to predict mortality after cardiac surgery. This study assesses their ability to provide risk-adjusted mortality in a contemporary cardiac surgical population. METHODS: The mortality probability was estimated with the additive and logistic EuroSCORE, and CARE score, for 3818 patients undergoing cardiac surgery at one institution between 1 April 2006 and 31 March 2009. Model discrimination was obtained using the area under the receiver operating characteristics (ROC) curve and calibration using the appropriate chi-square goodness-of-fit test. Recalibration of risk models was obtained by logistic calibration, when needed. Calculation of risk-adjusted mortality was performed for the institution and eight surgeons, using each model before and when needed, after recalibration. RESULTS: The area under the ROC curve is 0.72 (95% confidence interval (CI): 0.71-0.74) with the additive EuroSCORE, 0.84 (95% CI: 0.83-0.85) with the logistic EuroSCORE, and 0.79 (95% CI: 0.78-0.81) with the CARE score. The additive and logistic EuroSCORE have poor calibration, predicting a hospital mortality of 6.24% and 7.72%, respectively, versus an observed mortality of 3.25% (P < 0.001). Consequently, the risk-adjusted mortality obtained with those models is significantly underestimated for the institution and all surgeons. The CARE score has good calibration, predicting a mortality of 3.38% (P = 0.50). The hospital risk-adjusted mortality with the recalibrated additive and logistic EuroSCORE and CARE score is 3.24% (95% CI: 3.05-3.43%), 3.25% (95% CI: 3.05-3.44%), and 3.12% (95% CI: 2.94-3.34%), respectively. The individual surgeons' risk-adjusted mortality is similar with the recalibrated EuroSCORE models and CARE score, identifying two surgeons with higher rates than the hospital average mortality. CONCLUSIONS: The original additive and logistic EuroSCORE models significantly overestimate the risk of mortality after cardiac surgery. However, after recalibration both models provide reliable risk-adjusted mortality results. Despite its lower discrimination as compared with the logistic EuroSCORE, the CARE score remains calibrated a decade after its development. It is as robust as the recalibrated additive and logistic EuroSCORE to perform risk-adjusted mortality analysis.

A multicenter randomized controlled trial to assess the feasibility of testing modified ultrafiltration as a blood conservation technology in cardiac surgery.

OBJECTIVES: Modified ultrafiltration is a technique after cardiopulmonary bypass whereby blood withdrawn from the aortic cannula is passed across a semipermeable membrane to hemoconcentrate. Unblinded trials have suggested that modified ultrafiltration is efficacious for blood conservation. The objective of this trial was to assess the feasibility of a model testing modified ultrafiltration in which all members of the surgical team were blinded to the intervention. METHODS: Patients (<65kg) undergoing procedures involving cardiopulmonary bypass were randomized to undergo either modified ultrafiltration (n=29) or sham (circulation without an interposed filter, n=36) for 15minutes. The circuit was shielded from all members of the team except the perfusionist. A questionnaire was administered to determine the blinding success. RESULTS: Modified ultrafiltration resulted in a removal of 1000+/-251mL of fluid and a reduction in the pump balance (1025+/-807 vs 1804+/-838; P < .001) with an increase in hemoglobin immediately after intervention (increase of 7.7+/-8.8g/L in modified ultrafiltration vs 3.8+/-5.1g/L in sham; P=.04). Introduction or increase in dose of vasopressors was more frequent in the modified ultrafiltration group (52% vs 28%; P=.048). Differences in red cell transfusion rates between groups did not reach statistical significance (P=.59). Blinding was successful for the anesthetist (blinding index 0.13 [95% confidence interval, 0.11-0.38] and the intensivist (blinding index, 0.09 [95% confidence interval, 0.14-0.31]) but not for the surgeon (blinding index, 0.24 [95% confidence interval, 0.05-0.42]). The compliance rate for the transfusion protocol was greater than 90%. CONCLUSIONS: Modified ultrafiltration was effective for hemoconcentration after cardiopulmonary bypass in patients of low body weight, but it is associated with an increased need for vasopressor support. The anesthetist and intensivist were successfully blinded to the intervention.

Acute kidney injury after cardiac surgery: focus on modifiable risk factors.

BACKGROUND: Acute kidney injury (AKI) after cardiac surgery is a major health issue. Lacking effective therapies, risk factor modification may offer a means of preventing this complication. The objective of the present study was to identify and determine the prognostic importance of such risk factors. METHODS AND RESULTS: Data from a multicenter cohort of 3500 adult patients who underwent cardiac surgery at 7 hospitals during 2004 were analyzed (using multivariable logistic regression modeling) to determine the independent relationships between 3 thresholds of AKI (>25%, >50%, and >75% decrease in estimated glomerular filtration rate within 1 week of surgery or need for postoperative dialysis) with death rates, as well as to identify modifiable risk factors for AKI. The 3 thresholds of AKI occurred in 24% (n=829), 7% (n=228), and 3% (n=119) of the cohort, respectively. All 3 thresholds were independently associated with a >4-fold increase in the odds of death and could be predicted with several perioperative variables, including preoperative intra-aortic balloon pump use, urgent surgery, and prolonged cardiopulmonary bypass. In particular, 3 potentially modifiable variables were also independently and strongly associated with AKI. These were preoperative anemia, perioperative red blood cell transfusions, and surgical reexploration. CONCLUSIONS: AKI after cardiac surgery is highly prevalent and prognostically important. Therapies aimed at mitigating preoperative anemia, perioperative red blood cell transfusions, and surgical reexploration may offer protection against this complication.

Predicting outcomes in cardiac surgery: risk stratification matters?

PURPOSE OF REVIEW: To illustrate the limitations of predictive risk models in cardiac surgery, highlight the difficulty in interpreting risk-adjusted outcome analysis and discuss the challenges of making clinical decisions based on risk predictions, particularly in high-risk patients. RECENT FINDINGS: Predictive risk models developed after logistic regression or other complex statistical analysis are commonly perceived as rigorous means to determine risk-adjusted mortality in cardiac surgery. However, the discrimination provided by those predictive models is barely better than clinical judgment. Moreover, validation studies of those models show that their calibration is inconsistent, limiting their application for comparisons between different patient cohorts. Recent data also show that, without a reasonable overlap of case-mix distributions, apparently calibrated models used for risk-adjusted outcome analysis may lead to inaccurate side-by-side comparisons of provider performance. Finally, most predictive models overestimate risk, particularly in the high-risk patients. SUMMARY: Failure to account for many biological and procedural variables and for the constantly evolving practice of surgery and perioperative medicine likely contributes to the modest predictive performance of risk models in cardiac surgery. Consequently, those models should have limited input in the analysis of provider performance and in the decision to accept or deny surgery to the high-risk patients.

Variability and predictability of large-volume red blood cell transfusion in cardiac surgery: a multicenter study.

BACKGROUND: In cardiac surgery, excessive blood loss requiring large-volume red blood cell (RBC) transfusion is a common occurrence that is associated with significant morbidity and mortality. The objectives of this study were to measure the interinstitution variation and predictability of large-volume RBC transfusion. STUDY DESIGN AND METHODS: Data were retrospectively collected on 3500 consecutive cardiac surgical patients at seven Canadian hospitals during 2004. The crude and risk-adjusted institutional odds ratios (ORs) for large-volume (>or=5 U) RBC transfusion were calculated with logistic regression. The predictive accuracy of an existing prediction rule for large-volume RBC transfusion was calculated for each institution. RESULTS: Large-volume RBC transfusion occurred in 538 (15%) patients. When compared to the reference hospital (median crude rate), the institutional unadjusted and adjusted ORs for large-volume RBC transfusion ranged from 0.29 to 1.26 and 0.14 to 1.15, respectively (p<0.0001 for interinstitution variation). The variation was lower, but still considerable, for excessive blood loss, defined as at least 5-U RBC transfusion or reexploration; the ORs ranged from 0.42 to 1.22 (p<0.0001). The prediction rule performed well at most sites; its pooled positive predictive value for excessive blood loss was 71 percent (range, 63%-89%), and its negative predictive value was 90 percent (range, 87%-93%). CONCLUSIONS: There is marked interinstitution variation in large-volume RBC transfusion in cardiac surgery that is not explained by patient- or surgery-related factors. Despite this variation, patients at high or low risk for large-volume RBC transfusion can be accurately identified by a prediction rule composed of readily available clinical variables.

Neuroprotective effect of mild hypothermia in patients undergoing coronary artery surgery with cardiopulmonary bypass: five-year follow-up of a randomized trial.

OBJECTIVE: In a randomized trial of 223 patients undergoing coronary artery surgery with cardiopulmonary bypass, we have reported a neuroprotective effect of mild hypothermia. To determine whether the beneficial effect of mild hypothermia was long-lasting, we repeated the psychometric tests in 131 patients after 5 years. METHODS: Patients were cooled to 32 degrees C during aortic crossclamping and then randomized to rewarming to either 34 degrees C or 37 degrees C, with no further rewarming until arrival in intensive care unit. Cognitive function was measured preoperatively and 1 week and 5 years postoperatively with a battery of 11 psychometric tests interrogating verbal memory, attention, and psychomotor speed and dexterity. RESULTS: Patients who had greater cognitive decline 1 week after surgery showed poorer performance 5 years later. The magnitude of cognitive decline over 5 years was modest. The incidence of deficits defined as a 1 standard deviation [SD] decline in at least 1 of 3 factors was not different between temperature groups. Fewer patients in the hypothermic group had deficits that persisted over the 5 years, but this difference did not attain statistical significance (RR = 0.64, P = .16). CONCLUSIONS: The effect of surgery on cognitive function observed early after surgery is an important predictor of cognitive performance 5 years later. Although there was evidence of a neuroprotective effect of mild hypothermia early after surgery in the original cohort, the results after 5 years were inconclusive. In general, the magnitude of cognitive changes over 5 years was modest. We believe that further trials investigating the efficacy of mild hypothermia in patients having cardiac surgery are warranted.

Derivation and validation of a simplified predictive index for renal replacement therapy after cardiac surgery.

CONTEXT: A predictive index for renal replacement therapy (RRT; hemodialysis or continuous venovenous hemodiafiltration) after cardiac surgery may improve clinical decision making and research design. OBJECTIVES: To develop a predictive index for RRT using preoperative information. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort of 20 131 cardiac surgery patients at 2 hospitals in Ontario, Canada. The derivation cohort consisted of 10,751 patients at Toronto General Hospital (1999-2004). The validation cohorts consisted of 2566 patients at Toronto General Hospital (2004-2005) and 6814 patients at Ottawa Heart Institute (1999-2003). MAIN OUTCOME MEASURE: Postoperative RRT. RESULTS: RRT rates in the derivation, Toronto validation, and Ottawa validation cohorts were 1.3%, 1.8%, and 2.2%, respectively. Multivariable predictors of RRT were preoperative estimated glomerular filtration rate, diabetes mellitus requiring medication, left ventricular ejection fraction, previous cardiac surgery, procedure, urgency of surgery, and preoperative intra-aortic balloon pump. The predictive index was scored from 0 to 8 points. An estimated glomerular filtration rate less than or equal to 30 mL/min was assigned 2 points; other components were assigned 1 point each: estimated glomerular filtration rate 31 to 60 mL/min, diabetes mellitus, ejection fraction less than or equal to 40%, previous cardiac surgery, procedure other than coronary artery bypass grafting, intra-aortic balloon pump, and nonelective case. Among the 53% of patients with low risk scores (< or =1), the risk of RRT was 0.4%; by comparison, this risk was 10% among the 6% of patients with high-risk scores (> or =4). The predictive index had areas under the receiver operating characteristic curve in the derivation, Toronto validation, and Ottawa validation cohorts of 0.81, 0.78, and 0.78, respectively. When these cohorts were stratified based on index scores, likelihood ratios for RRT were more concordant than observed RRT rates. CONCLUSIONS: RRT after cardiac surgery is predicted by readily available preoperative information. A simple predictive index based on this information discriminated well between low- and high-risk patients in derivation and validation cohorts. The index had improved generalizability when used to predict likelihood ratios for RRT.

Clinical predictions and decisions to perform cardiac surgery on high-risk patients.

The proportion of high-risk patients undergoing cardiac surgery has increased steadily over the last two decades. Many of those patients have a catastrophic postoperative course and use hospital resources in a proportion that largely outweighs their number. Consequently, the appropriateness of invasive and intensive interventions in those patients has been questioned. If futility of care were predictable preoperatively, cardiac surgery would probably be denied to many high-risk patients. Logistic regression has been used to develop many complex predictive models to identify high-risk patients and predict their outcome; however, those models do not provide much more discrimination than clinical judgment alone. Moreover, with continuous improvement in medical care all risk models lose their calibration over time. As a result, they often overestimate the probabilities of poor outcome in the individual patients. Many high-risk cardiac surgical patients require a prolonged stay in the intensive care unit (ICU). The analysis of small cohorts of patients who had a prolonged postoperative stay in the ICU shows that 50% and 40% of them are still alive at 1- and 2-year follow-up, respectively; and most survivors report a good quality of life. Considering the limitations of predictive risk models and the satisfaction of cardiac surgical patients who survive after a prolonged ICU stay, it is reasonable to recognize that cardiac surgery should rarely be denied to high-risk patients unless technically unfeasible, and clinical predictions should have only a marginal role in the decision to operate on those patients.

Safety of deliberate intraoperative and postoperative hypothermia for patients undergoing coronary artery surgery: a randomized trial.

BACKGROUND: Hypothermia in the perioperative period is associated with adverse effects, particularly bleeding. Before termination of cardiopulmonary bypass, rewarming times and perfusion temperatures are often increased to avoid post-cardiopulmonary bypass hypothermia and the presumed complications. This practice may, however, also have adverse effects, particularly cerebral hyperthermia. We present safety outcomes from a trial in which patients undergoing coronary artery surgery were randomly assigned to normothermia or hypothermia for the entire surgical procedure. METHODS: Consenting patients over the age of 60 years presenting for a first, elective coronary artery surgery with cardiopulmonary bypass were randomly assigned to having their nasopharyngeal temperature maintained at either 37 degrees C (group N; 73 patients) or 34 degrees C (group H; 71 patients) throughout the intraoperative period, with no rewarming before arrival in the intensive care unit. All received tranexamic acid. RESULTS: There was no clinically important difference in intraoperative blood product or inotrope use. Temperatures on arrival in the intensive care unit were 36.7 degrees C +/- 0.38 degrees C and 34.3 degrees C +/- 0.38 degrees C in groups N and H, respectively. Blood loss during the first 12 postoperative hours was 596 +/- 356 mL in group N and 666 +/- 405 mL in group H (mean difference +/- 95% confidence interval, 70 +/- 126 mL; P =.28). There was no significant difference in blood product utilization, intubation time, time in the hospital, myocardial infarction, or mortality. The mean time in the intensive care unit was 8.4 hours less in the hypothermic group (P =.02). CONCLUSIONS: Our data support the safety of perioperative mild hypothermia in patients undergoing elective nonreoperative coronary artery surgery with cardiopulmonary bypass. These findings suggest that complete rewarming after hypothermic cardiopulmonary bypass is not necessary in all cases.