Colleen G. Koch

Morbidity and mortality risk associated with red blood cell and blood-component transfusion in isolated coronary artery bypass grafting

Objective:Our objective was to quantify incremental risk associated with transfusion of packed red blood cells and other blood components on morbidity after coronary artery bypass grafting. Design:The study design was an observational cohort study. Setting:This investigation took place at a large tertiary care referral center. Patients:A total of 11,963 patients who underwent isolated coronary artery bypass from January 1, 1995, through July 1, 2002. Interventions:None. Measurements and Main Results:Among the 11,963 patients who underwent isolated coronary artery bypass grafting, 5,814 (48.6%) were transfused. Risk-adjusted probability of developing in-hospital mortality and morbidity as a function of red blood cell and blood-component transfusion was modeled using logistic regression. Transfusion of red blood cells was associated with a risk-adjusted increased risk for every postoperative morbid event: mortality (odds ratio [OR], 1.77; 95% confidence interval [CI], 1.67–1.87; p < .0001), renal failure (OR, 2.06; 95% CI, 1.87–2.27; p < .0001), prolonged ventilatory support (OR, 1.79; 95% CI, 1.72–1.86; p < .0001), serious infection (OR, 1.76; 95% CI, 1.68–1.84; p < .0001), cardiac complications (OR, 1.55; 95% CI, 1.47–1.63; p < .0001), and neurologic events (OR, 1.37; 95% CI, 1.30–1.44; p < .0001). Conclusions:Perioperative red blood cell transfusion is the single factor most reliably associated with increased risk of postoperative morbid events after isolated coronary artery bypass grafting. Each unit of red cells transfused is associated with incrementally increased risk for adverse outcome.

Gender and outcomes after coronary artery bypass grafting: A propensity-matched comparison

OBJECTIVE Our objective is to determine whether gender is a marker or a causal influence for poor outcomes after coronary revascularization. METHODS Propensity-modeling techniques were used to investigate whether gender adversely impacts outcomes after coronary revascularization. A parsimonious explanatory model was developed by bootstrap bagging with variable selection from 64 baseline and 37 operative variables. Propensity scores were calculated from a logistic model that included the parsimonious model and additional baseline variables. Greedy matching techniques were applied to match female and male patients to the nearest propensity scores. Comparisons were made among the propensity-matched women and men. RESULTS Of the 15,597 patients undergoing isolated coronary artery bypass graft surgery, only 26% of the 3596 women were matched on propensity scores with men. Distribution of covariates among the matched pairs was, on average, equal. Postoperative mortality (P =.76), neurologic morbidity (global deficit P =.07, focal deficit P =.51), infection (sepsis P =.88), mediastinitis (P =.18), renal failure (P =.84), intra-aortic balloon pump usage (P =.61), and reoperation for bleeding (P =.10) were similar among women and men. Occurrence of Q-wave myocardial infarction (P = <.01), postoperative inotropic usage (P = <.01), and prolonged ventilatory support (P =.02) were more common in women compared with propensity-matched men. CONCLUSIONS The preoperative profiles of women and men are markedly different. Propensity matching women and men was difficult, because only 26% of women were able to be matched with men. However, in well-matched patients, female gender was not associated with increased mortality and had minimal impact on morbidity after coronary artery bypass grafting.

Morbidity of Bleeding After Cardiac Surgery: Is It Blood Transfusion, Reoperation for Bleeding, or Both?

BACKGROUND Etiology for increased morbidity in patients (2% to 8%) undergoing reoperation for bleeding after cardiac surgery is unclear. Recent work suggests that it may be related to red-cell transfusion, but what role does reoperation itself play? We sought to determine prevalence of and risk factors for reoperation for bleeding, separate the effect of reoperation from that of transfusion on hospital mortality and major morbidity, and identify the source of bleeding. METHODS From January 1, 2000 to January 1, 2010, 18,891 primary and repeat coronary artery bypass grafting, valve, or combined operations were performed. Risk factors for reoperation were identified by multivariable logistic regression. Hospital mortality and major morbidity were compared in propensity-matched patients requiring reoperation and not. Medical records from 2005 to 2010 were reviewed to determine bleeding source. RESULTS A total of 566 patients (3.0%) underwent reoperation for bleeding, with considerable variability over time. Risk factors included older age, higher acuity, greater comorbidity, aortic valve surgery, longer myocardial ischemic and cardiopulmonary bypass durations, and surgeon. Mortality was higher for propensity-matched patients requiring reoperation; 8.5% (68% confidence interval [CI] 7.3% to 9.9%) versus 1.8% (CI 1.2% to 2.5%). Both greater transfusion and reoperation were independently associated with increased risk of mortality and major morbidity. At reoperation, technical factors (74%), coagulopathy (13%), both (10%), or other (3.3%) causes were responsible for bleeding. CONCLUSIONS Transfusion and reoperation for bleeding both contribute to postoperative mortality and morbidity. Technical reasons are at the root of most bleeding, emphasizing a major focus for process improvement to minimize need for reoperation and blood use.

Role of Intraoperative and Postoperative Blood Glucose Concentrations in Predicting Outcomes after Cardiac Surgery

Background:Severe hyperglycemia is associated with adverse outcomes after cardiac surgery. Whether intraoperative and postoperative glucose concentrations equally impact outcomes is unknown. The objective of this investigation was to compare the ability of perioperative glucose concentrations and glycemic variability to predict adverse outcomes. Risk associated with decreasing increments of glucose concentrations, hypoglycemia, and diabetic status was also examined. Methods:This retrospective analysis of prospectively collected data included 4,302 patients who underwent cardiac surgery between October 3, 2005 and May 31, 2007 at the Cleveland Clinic. Time-weighted mean intraoperative (GlcOR) and postoperative (GlcICU) glucose concentrations were calculated. Patients were categorized as follows: Glc more than 200, 171–200, 141–170, and less than or equal to 140 mg/dl. Coefficient of variation was used to calculate glycemic variability. Logistic regression model with backward selection assessed the relationship between glucose concentrations, variability, and adverse outcomes while adjusting for potential confounders. Another model assessed the predictability of GlcOR and GlcICU on adverse outcomes. Results:Both GlcOR and GlcICU predicted risk for mortality and morbidity. Increased postoperative glycemic variability was associated with increased risk for adverse outcomes. Severe hyperglycemia (GlcOR and GlcICU > 200 mg/dl) was associated with worse outcomes; however, decreasing increments of GlcOR did not consistently reduce risk. GlcOR less than or equal to 140 mg/dl was not associated with improved outcomes compared with severe hyperglycemia, despite infrequent hypoglycemia. Diabetic status did not influence the effects of hyperglycemia. Conclusion:Perioperative glucose concentrations and glycemic variability are important in predicting outcomes after cardiac surgery. Incremental decreases of intraoperative glucose concentrations did not consistently reduce risk. Despite rare hypoglycemia, intraoperative glucose concentrations closest to normoglycemia were associated with worse outcomes.

The concordance of intraoperative left ventricular wall-motion abnormalities and electrocardiographic S-T segment changes: Association with outcome after coronary revascularization

BACKGROUND Transesophageal echocardiography (TEE) and Holter electrocardiography (ECG) are used to detect intraoperative ischemia during coronary artery bypass graft surgery (CABG). Concordance of these modalities and sensitivity as indicators of adverse perioperative cardiac outcomes are poorly defined. The authors tried to determine whether routine use of Holter ECG and TEE in patients with CABGs has clinical value in identifying those patients in whom myocardial infarction (MI) is likely to develop. METHODS A total of 351 patients with CABG and both ECG- and TEE-evaluable data were examined for the occurrence of ischemia and infarction. The TEE and five-lead Holter ECGs were performed continuously during cardiac surgery. The incidence of MI (creatine kinase-MB > or = 100 ng/ml) within 12 h of arrival in the intensive care [ICU] unit, new ECG Q wave on ICU admission or on the morning of postoperative day 1, or both, were recorded. RESULTS Electrocardiographic or TEE evidence of intraoperative ischemia was present in 126 (36%) patients. The concordance between modalities was poor (positive concordance = 17%; Kappa statistic = 0.13). Myocardial infarction occurred in 62 (17%) patients, and 32 (52%) of them had previous intraoperative ischemia. Of these, 28 (88%) were identified by TEE, whereas 13 (41%) were identified by ECG. Prediction of MI was greater for TEE compared with ECG. CONCLUSIONS Wall-motion abnormalities detected by TEE are more common than S-T segment changes detected by ECG, and concordance between the two modalities is low. One half of patients with MI had preceding ECG or TEE ischemia. Logistic regression revealed that TEE is twice as predictive as ECG in identifying patients who have MI.

What are the real rates of postoperative complications: Elucidating inconsistencies between administrative and clinical data sources

BACKGROUND Comparison of quality outcomes generated from administrative and clinical datasets have shown inconsistencies. Understanding this is important because data designed to drive performance improvement are used for public reporting of performance. We examined administrative and clinical data and 2 clinical data sources in 4 surgical morbidity outcomes. STUDY DESIGN Patients who underwent operations between January 2009 and May 2010 had outcomes compared for postoperative hemorrhage, respiratory failure, deep vein thrombosis (DVT), and sepsis. Three data sources were examined: administrative (Agency for Healthcare Research and Quality [AHRQ] Patient Safety Indicators [PSIs]), a national clinical registry (National Surgical Quality Improvement Program [NSQIP]), and an institutional clinical registry (Cardiovascular Information Registry [CVIR]). Cohens Kappa (K) coefficient was used as a measure of agreement between data sources. RESULTS For 4,583 patients common to AHRQ and NSQIP, concordance was poor for sepsis (K = 0.07) and hemorrhage (K = 0.14), moderate for respiratory failure (K = 0.30), and better concordance for DVT (K = 0.60). For 7,897 patients common to AHRQ and CVIR, concordance was poor for hemorrhage (K = 0.08), respiratory failure (K = 0.02), and sepsis (K = 0.16), and better for DVT (K = 0.55). For 886 patients common to NSQIP and CVIR, concordance was poor for sepsis (K = 0.054), moderate for hemorrhage (K = 0.27) and respiratory failure (K = 0.4), and better for DVT (K = 0.51). CONCLUSIONS We demonstrate considerable discordance between data sources measuring the same postoperative events. The main contributor was difference in definitions, with additional contribution from data collection and management methods. Although any of these sources can be used for their original intent of performance improvement, this study emphasizes the shortcomings of using these sources for grading performance without standardizing definitions, data collection, and management.

Impact of Prosthesis–Patient Size on Functional Recovery After Aortic Valve Replacement

Background—Prosthesis–patient size mismatch results when an implanted prosthetic aortic valve is of insufficient size for a patient’s body surface area. The relation between prosthesis–patient size and functional capacity and adverse postoperative outcome is inconsistent. Our objectives were to examine the impact of valve replacement, continuous prosthesis–patient size, and other factors on functional recovery after aortic valve replacement (AVR) with the Duke Activity Status Index (DASI). Methods and Results—From June 15, 1995, through May 14, 1998, 1108 patients underwent AVR after completing a DASI survey. Of these, 1014 completed a postoperative DASI survey at an average of 8.3 months postoperatively. Logistic ordinal regression was used to examine the influence of demographic variables, comorbidities, baseline DASI scores, indexed valve orifice area, standardized orifice size, and postoperative morbid events on postoperative DASI. There was overall improvement in postoperative functional recovery reflected by median preoperative and postoperative DASI scores of 29 and 46, P<0.001, respectively. Neither indexed orifice area, P=0.94, nor standardized orifice size, P=0.96, was associated with functional recovery. Female sex, increasing age, elevated serum creatinine, increased central venous pressure, and red blood cell transfusion were factors associated with poor postoperative functional recovery. Conclusions—A majority of patients report improvement in functional quality of life early after AVR. Similar functional recovery was demonstrated for patients along the full spectrum of valve sizes indexed to body size, even for values considered to represent severe mismatch for patient size. Factors other than prosthesis–patient size influence functional quality of life early after AVR.

Influence of Concentric Left Ventricular Remodeling on Early Mortality After Aortic Valve Replacement

BACKGROUND Severe left ventricular (LV) hypertrophy increases risk for adverse outcome after aortic valve replacement. Whether LV geometry influences mortality risk after aortic valve replacement is unclear. And, whether LV mass or relative wall thickness (RWT) better predicts risk for adverse postoperative outcomes is unknown. The purpose of this investigation was to examine the influence of LV geometry and LV hypertrophy on morbidity and in-hospital mortality after aortic valve replacement, and to determine whether LV mass or RWT had better prognostic ability. METHODS Between January 1996 and June 2004, 5,083 patients underwent aortic valve replacement. Preoperative echocardiographic data was used to calculate LV mass and RWT. Left ventricular geometry was classified into one of four categories on the basis of LV mass indexed to body height and RWT: (1) concentric hypertrophy, (2) eccentric hypertrophy, (3) concentric remodeling, and (4) normal. Postoperative mortality and multisystem morbidities of patients with concentric geometries were compared to patients with nonconcentric geometries by propensity and logistic regression modeling. Also, prognostic ability of RWT and LV mass was compared. RESULTS Nine hundred sixty-four patients with concentric geometry were propensity-matched to 964 patients with nonconcentric geometry. In-hospital mortality (38 [3.9%] versus 18 [1.9%]; p = 0.007), cardiac morbidity (33 [3.4%] versus 17 [1.8%]; p = 0.022), and prolonged intubation (85 [8.8%] versus 58 [6.0%]; p = 0.019) were higher in patients with concentric versus nonconcentric geometry. Increasing RWT, not LV mass, was associated with adverse outcomes. CONCLUSIONS Concentric geometries are associated with increased risk for in-hospital mortality after aortic valve replacement. Increased RWT is associated with adverse outcomes. Preoperative risk stratification should include assessments of LV hypertrophy and LV geometry.

Outcome of Patients Who Refuse Transfusion After Cardiac Surgery A Natural Experiment With Severe Blood Conservation

BACKGROUND Jehovahs Witness patients (Witnesses) who undergo cardiac surgery provide a unique natural experiment in severe blood conservation because anemia, transfusion, erythropoietin, and antifibrinolytics have attendant risks. Our objective was to compare morbidity and long-term survival of Witnesses undergoing cardiac surgery with a similarly matched group of patients who received transfusions. METHODS A total of 322 Witnesses and 87 453 non-Witnesses underwent cardiac surgery at our center from January 1, 1983, to January 1, 2011. All Witnesses prospectively refused blood transfusions. Among non-Witnesses, 38 467 did not receive blood transfusions and 48 986 did. We used propensity methods to match patient groups and parametric multiphase hazard methods to assess long-term survival. Our main outcome measures were postoperative morbidity complications, in-hospital mortality, and long-term survival. RESULTS Witnesses had fewer acute complications and shorter length of stay than matched patients who received transfusions: myocardial infarction, 0.31% vs 2.8% (P = . 01); additional operation for bleeding, 3.7% vs 7.1% (P = . 03); prolonged ventilation, 6% vs 16% (P < . 001); intensive care unit length of stay (15th, 50th, and 85th percentiles), 24, 25, and 72 vs 24, 48, and 162 hours (P < . 001); and hospital length of stay (15th, 50th, and 85th percentiles), 5, 7, and 11 vs 6, 8, and 16 days (P < . 001). Witnesses had better 1-year survival (95%; 95% CI, 93%-96%; vs 89%; 95% CI, 87%-90%; P = . 007) but similar 20-year survival (34%; 95% CI, 31%-38%; vs 32% 95% CI, 28%-35%; P = . 90). CONCLUSIONS Witnesses do not appear to be at increased risk for surgical complications or long-term mortality when comparisons are properly made by transfusion status. Thus, current extreme blood management strategies do not appear to place patients at heightened risk for reduced long-term survival.

Recent metformin ingestion does not increase in-hospital morbidity or mortality after cardiac surgery.

BACKGROUND:Perioperative treatment of type 2 diabetes with metformin, an oral hypoglycemic drug, is thought to increase the risk of life-threatening postoperative lactic acidosis. In contrast, metformin improves serum glucose control and has beneficial cardiovascular effects, which may decrease the risk of adverse outcomes. In this investigation we sought to determine the influence of metformin treatment on mortality and morbidity compared with treatment with other oral hypoglycemic drugs in diabetic patients undergoing cardiac surgery. METHODS:In this retrospective investigation, 1284 diabetic patients, with recent oral hypoglycemic ingestion (presumed to be 8–24 h preoperatively), underwent cardiac surgery from 1994–2004. Propensity scores were calculated from a logistic model which included baseline characteristics and perioperative variables. Four-hundred-forty-three (85%) of the metformin-treated patients were matched on nearest propensity score using greedy matching techniques with 443 nonmetformin-treated patients. Postoperative outcomes were compared between matched metformin- and nonmetformin-treated patients. RESULTS:In-hospital mortality, cardiac, renal, and neurologic morbidities were similar between groups. Metformin-treated patients had less postoperative prolonged tracheal intubation [OR (95% CI), 0.3 (0.1, 0.7), P = 0.003], infection [0.2 (0.1, 0.7), P = 0.007] and overall morbidities [0.4 (0.2, 0.8), P = 0.005]. CONCLUSIONS:These data suggest that recent metformin ingestion is not associated with increased risk of adverse outcome in cardiac surgical patients. Alternatively, metformin treatment may have beneficial effects.