The Association of Complication Type with Mortality and Prolonged Stay After Cardiac Surgery with Cardiopulmonary Bypass

Transcription

1 The Association of Complication Type with Mortality and Prolonged Stay After Cardiac Surgery with Cardiopulmonary Bypass Ian J. Welsby, FRCA*, Elliott Bennett-Guerrero, MD*, Darryl Atwell, MD*, William D. White, MPH*, Mark F. Newman, MD*, Peter K. Smith, MD, and Michael G. Mythen, FRCA* Departments of *Anesthesiology and Surgery, Duke University Medical Center, Durham, North Carolina Outcome after cardiac surgery varies depending on complication type. We therefore sought to determine the association between complication type, mortality, and length of stay in a large series of patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Multivariate logistic regression was used to test for differences between complication types in mortality and prolonged length of stay ( 10 days) while controlling for preoperative and intraoperative risk factors. In 2609 consecutive cardiac surgical patients requiring CPB, the mortality rate was 3.6%; 36.5% had one or more complications, and 15.7% experienced an adverse outcome (death or prolonged length of stay). Multivariate logistic regression demonstrated that complication type was significantly associated with adverse outcome (P 0.001) independent of Parsonnet score and CPB time (c-index 0.80). The development of noncardiac complications only (Group NC) and cardiac complications with other organ involvement (Group B) significantly increased mortality and hospital and intensive care unit length of stay (P 0.001) when compared with cardiac complications only (Group C). The incidences of adverse outcome in Groups C, NC, and B were 15%, 43%, and 67%, respectively; the mortality rates were 3%, 7%, and 20%, respectively. All these intergroup comparisons were significantly different (adjusted P 0.05). Complications involving organs other than the heart appear to be more deleterious than cardiac complications alone, underscoring the need for strategies to reduce noncardiac complications. (Anesth Analg 2002;94:1072 8) Complications have a negative and variable effect on outcome after cardiac surgery (1 4), the extent of which may be difficult to separate from the well described influence of preoperative and intraoperative factors (2,5 8). Before describing this complex relationship, it is necessary to determine an appropriate definition of outcome. Since the late 1980s, much attention has been focused on cardiac surgical mortality rates after the publication of the results of open-heart surgery in the Medicare population (9). The importance of risk stratification to allow the reporting of risk-adjusted mortality rates was quickly realized (8), and many preoperative risk scores were developed (6,7,8,10 14). The Society of Thoracic Surgeons established the National Database for Cardiothoracic Surgery in 1989; this has Accepted for publication December 19, Address correspondence and reprint requests to Ian J. Welsby, FRCA, Box 3094, Department of Anesthesiology, Duke University Medical Center, Durham, NC Address to welsb001@mc.duke.edu. identified a nationwide improvement in the observed versus expected mortality rates from 1990 to 1997 (15). Reporting mortality as an outcome has the advantage of being a relatively unambiguous, albeit uncommon, end point that is almost universally recorded. Morbidity, however, may be more closely related to the length of hospital and intensive care unit (ICU) stay, quality of life after surgery, overall resource utilization, and cost (5,7,16). There is a relatively frequent incidence of morbidity; 15% 30% of cardiac surgical patients experience some degree of morbidity, making it necessary to consider both mortality and morbidity when describing outcome (1,2,5,7,16). Despite its importance, the optimal method of quantifying morbidity is unclear. Complication rates have been used as a measure of morbidity (1,3), and although they offer no direct data on the effect on resource utilization, complications do prolong hospital stay (1,2). Some studies (5,7) chose certain predefined, serious morbidities. This helps focus on serious complications and provides specific end points but does not address the effect on resource utilization. Hospital 2002 by the International Anesthesia Research Society 1072 Anesth Analg 2002;94: /02

2 ANESTH ANALG CARDIOVACULAR ANESTHESIA WELSBY ET AL ;94: COMPLICATIONS, OUTCOMES, AND CARDIAC SURGERY and ICU lengths of stay are major components of postoperative resource utilization; they provide objective, continuous data related to the severity of morbidity and have been advocated as an alternative to complication data (17). Length of stay, however, is a surrogate marker of morbidity and is influenced by other factors, such as individual and institutional practice. Confining a study to a single institution with a standardized postoperative care pathway significantly limits this variability. Serious morbidity can be defined by a length of stay that is considered consistent with a significant complication (2,5) and includes patients who died (7). Thus, in the absence of a standardized definition of morbidity, we elected to combine mortality with length of stay and report complication rates when assessing outcome. The influence of preoperative and intraoperative factors on outcome in terms of mortality and morbidity has been well described (2,5 8). Although it is clinically observed that the outcome after cardiac surgery depends on the complication type, this relationship has not been systematically explored and quantified. Therefore, we examined complication rates and the association of complication type with mortality and length of stay after cardiac surgery with cardiopulmonary bypass (CPB), after controlling for preoperative and intraoperative risk by using Parsonnet scores (8) and duration of CPB, respectively. Methods We selected a cohort of consecutive cardiac surgical cases over a 2-yr period (January 1993 to January 1995) to study the effects of complication type on outcome after cardiac surgery with CPB. All cases were included, because the effects of procedure type and urgency were included as preoperative risk factors in the Parsonnet score (8). We did not include patients undergoing off-pump coronary artery bypass grafting surgery, because this group was not included in the development of established preoperative risk scores (6,8,11,13,14). To avoid selection bias by excluding this group, we chose our study period from before the introduction of off-pump coronary artery bypass grafting surgery at our institution. With IRB approval, patient demographics, the variables required for preoperative risk scoring, CPB time, and postoperative outcome data were recorded as components of the Duke Cardiovascular Database (18). These data were collected by dedicated nonmedical personnel from contemporaneous medical records, custom datasheets, and records of laboratory results. Quality assurance involved random chart review for data confirmation and continuing assessment of data completeness. Incomplete fields were updated by medical personnel on a chart review basis. The Parsonnet additive score (Parsonnet score) was used to quantify preoperative risk. The sum of the integer points assigned to weighted risk factor components derived from a logistic regression model (8) was used to calculate these Parsonnet scores. This established mortality risk score was validated in our study population by calculating the c-index pertaining to the outcomes in question. The preoperative variables used to calculate the Parsonnet score included age, sex, type of procedure, severity of presenting condition, left ventricular ejection fraction, and comorbidities such as hypertension, diabetes, morbid obesity, and dialysis dependency. CPB time (in minutes) is significantly associated with both postoperative mortality (7,19) and morbidity (7) and was used to adjust for intraoperative risk. A patient was deemed to have developed a clinical complication if any of 35 specific predefined complications occurred. These are listed in Appendix 1 and are categorized into one of nine body systems; the miscellaneous category included decubitus ulcers and adverse drug reactions. For much of the statistical analysis, patients were divided into four groups that represented different complication types: Group N (none of the 35 complications reported), Group C (complications in the cardiac category only; Appendix 1), Group NC (complications in noncardiac categories only), and Group B (complications in both cardiac and noncardiac categories). The purpose of this classification of complications was to expand the focus from the operative site, because many serious complications seen in the cardiac ICU involve organs other than the heart. Group B, per se, represents multiorgan dysfunction and included end-organ sequelae of cardiac complications. The incidence of in-hospital mortality and the cardiac ICU and hospital lengths of stay were noted. Hospital length of stay was defined as the number of days from the date of surgery to the date of live discharge. An adverse outcome was defined as death or prolonged length of stay (longer than 10 days). This definition was chosen because 10 days is twice as long as the planned postoperative stay of 5 days and is regarded by our clinicians as a length of stay associated with a clinically important complication rather than social or nursing issues related to suitability for hospital discharge. In addition, death was included in our assessment of morbidity because it may preclude the diagnosis of other serious morbidities (7) or foreshorten the length of stay. After oral methadone or diazepam premedication, anesthesia was typically induced with midazolam, fentanyl, and thiopental and maintained with a balanced technique that used midazolam, fentanyl, and isoflurane. In general, patients were monitored with

3 1074 CARDIOVACULAR ANESTHESIA WELSBY ET AL. ANESTH ANALG COMPLICATIONS, OUTCOMES, AND CARDIAC SURGERY 2002;94: electrocardiogram (with ST trending capability), invasive arterial pressure, and pulmonary artery catheter measurements. Nonpulsatile hypothermic (28 C 34 C) CPB was conducted using a membrane oxygenator (Cobe CML; Cobe Inc., Arvada, CO), a crystalloid and mannitol prime and an arterial line filter (Cobe). Porcine heparin was administered as a bolus of 300 U/kg and supplemented during CPB to maintain an activated clotting time (Hemochron 801; International Technidyne Corp., Edison, NJ) of 450 s. During CPB, temperature-adjusted flow rates of 2.5 L min 1 m 2 were used, and mean arterial blood pressure was generally maintained between 50 and 60 mm Hg or 60 and 70 mm Hg if previous evidence of cerebrovascular disease was noted. Anesthesia was maintained with isoflurane (0.5% 1.0%) via the oxygenator, and -stat management for maintenance of normal ph, Po 2, and Pco 2 values was used. A hematocrit of 0.18 to 0.20 was typically acceptable during CPB, and this was increased to 0.20 for separation from CPB. Insulin was administered by the anesthesiologist to maintain glucose levels 300 mg/dl. Cold blood or crystalloid cardioplegia solution was used for myocardial protection and infused either antegrade, retrograde, or antegrade/retrograde, according to the surgeon s preference and the clinical circumstance. The intraoperative management of patients undergoing cardiac surgery at this institution did not significantly change during the time period studied. Inotropic and vasoactive drugs were used to maintain a cardiac index of 2.0 L min 1 m 2,amean arterial blood pressure of 60 mm Hg, and a systolic arterial blood pressure of 140 mm Hg. Patients were tracheally extubated if they were hemodynamically stable with minimal mediastinal bleeding, were awake and appropriate with normal or baseline arterial blood gas values, and had a temperature 36 C. There was a 24-h respiratory therapist and resident coverage to allow for extubation at night. Extubated patients were discharged from the ICU provided their respiratory status was stable on a fraction of inspired oxygen of 0.4, they were cardiovascularly stable with minimal chest tube drainage, their temperature was 38 C, and there were no clinical concerns regarding renal dysfunction. Ideally, patients were monitored in the ICU for 12 h after tracheal extubation. Aspirin and -adrenergic blockers were prescribed on the first postoperative day unless clinically contraindicated. Criteria for discharge from the hospital included temperature 38 C (provided the white blood count was decreasing and urine analysis was negative); cardiovascular stability (on aspirin and -adrenergic blockers, if tolerated, and oral antiarrhythmic drugs, if required); resolution of any new pulmonary insufficiency, as determined clinically; tolerance of light diet and bowel movement; the ability to pass urine (with an indwelling catheter if in situ preoperatively or after the diagnosis of benign prostatic hypertrophy); normal or baseline mentation; adequate analgesia on oral medication; and suitable social support provided by family, home help, or a nursing facility. A postoperative care protocol was previously initiated to facilitate timely discharge by the end of Postoperative Day 5, and this was aggressively pursued provided the previous criteria were satisfied. Occasionally, discharge at the end of Postoperative Day 3 or 4 was possible. The Kolmogorov-Smirnov test showed that only age and weight could satisfactorily be approximated by a normal distribution. These data are presented as mean sd. All other values are presented as the median with the interquartile range (IQR), with the mean sometimes quoted for comparison. Descriptive statistics are expressed as numbers and percentages. For the composite end-point of mortality or prolonged length of stay, logistic regression was used to test differences among complication type, adjusting for Parsonnet score, CPB time, and the two-way interactions of the last two with complication type. Starting with a full model, predictors with P 0.10 were removed stepwise until only significant predictors remained, except that it was determined a priori to keep the Parsonnet score in the model as a required adjustment. After a significant overall effect, pairwise comparisons were made from the same model with a Bonferroni adjustment. The c-index (equivalent to the area under the receiver operating characteristic curve) is reported to express the predictive value of the models (20). Differences among complication types in hospital and ICU length of stay were tested by using the Kruskal-Wallis test or Wilcoxon s two-sample nonparametric test, as appropriate. Results were confirmed with multivariate analysis of variance adjusting for Parsonnet score and CPB time, with use of the Tukey-Kramer adjustment for multiple paired comparisons. Patients who died were excluded from length-of-stay comparisons, because we defined length of stay as time to live discharge. Kaplan-Meier plots of time to discharge by complication type were compared by using Wilcoxon s test and log-rank tests, censoring values for patients who died. For all comparisons, a P value 0.05 was considered statistically significant. Statistical analysis was performed with SAS version 6.12 (SAS Institute, Cary, NC). Results From 2609 patients, 45 (1.7%) were excluded from regression analysis because of missing values for response or explanatory variables; the demographics of

4 ANESTH ANALG CARDIOVACULAR ANESTHESIA WELSBY ET AL ;94: COMPLICATIONS, OUTCOMES, AND CARDIAC SURGERY this cohort are listed in Table 1. The distribution according to surgical priority was as follows: 5% emergent, 23% urgent, and 72% elective, with mortality rates of 9.7%, 4.3%, and 3%, respectively. Overall, the mortality rate was 3.6%; 949 patients (36.5%) experienced at least one complication, and 409 patients (15.7%) experienced an adverse outcome (death or prolonged length of stay). The mean Parsonnet score was 10.3 ( 7.7), and the mean CPB time was 112 ( 42) min. In survivors, the median (IQR) postoperative hospital length of stay was 6 (5 8) days, and 315 (12.6%) of these patients were in the hospital for longer than 10 days. For total number of days spent in the ICU, the overall median (IQR) was 1 (1 2) day; 884 patients (35.3%) stayed more than 1 day, and 426 patients (17%) stayed more than 2 days. The incidence of complications by organ system category (Appendix 1) and the associated outcomes are described in Table 2. A patient with a complication in any category had a significantly increased length of hospital stay (P ) when compared with patients with no complications. With regard to complication type, there were 1618 patients (62%) in Group N (no complications), 552 (21.2%) in Group C (cardiac complications only), 228 (8.7%) in Group NC (noncardiac complications only), and 211 (8.1%) in Group B (both cardiac and noncardiac complications). The distributions of Parsonnet scores and CPB times by complication type are listed in Table 3. Of note, there was no significant difference in Parsonnet scores or CPB times between Groups NC and C. Group B had significantly higher and Group N significantly lower Parsonnet scores and CPB times than the other groups. Table 4 lists mortality and hospital and ICU lengths of stay by complication type. The multivariate analysis of variance confirmed all two-group comparisons, except that between Groups N and C with respect to ICU length of stay, to be significantly different (adjusted P 0.05). Notably, Group B had the worst outcomes. Patients who exhibited noncardiac complications only (Group NC) had a significantly prolonged length of stay and increased mortality compared with those exhibiting cardiac complications only (Group C). A more detailed illustration of hospital length of stay, by complication type, is depicted in the Kaplan- Meier plot of estimated time to discharge (Fig. 1). There is a significant difference (P 0.001) between all four curves; this graph emphasizes the influence of complication type on length of stay. Logistic regression on the outcome adverse outcome demonstrated that complication type was significantly and independently associated with adverse outcomes, after controlling for Parsonnet score and CPB time. Complication type (P ), Parsonnet score (P ), and CPB time (P ) were Table 1. Demographic Characteristics (n 2609) Variable Data Age (yr) Weight (kg) Sex (% male) 64% Parsonnet score CPB time (min) Procedure CABG 2095 (80.3%) Redo CABG 72 (11.8%) Valve 309 (2.8%) Redo valve 29 (1.1%) CABG and valve 76 (2.9%) Other 28 (1.1%) Data are presented as mean sd or n (%). CABG Coronary artery bypass grafting; CPB cardiopulmonary bypass. independently and significantly associated with adverse outcomes. The following odds ratio estimates (95% confidence limits) were calculated for the occurrence of adverse outcomes by complication type: ( ) for Group B versus Group C and 4.4 ( ) for Group NC versus Group C. Assessment of the predictive value of this model revealed a c-index value of Mortality and length of stay were not reported for every complication, because there was an infrequent incidence of many noncardiac complications. However, noncardiac complications were represented in Groups B and NC. Discussion This large cohort presents a mortality rate comparable to Society of Thoracic Surgeons data covering a similar period (15) and emphasizes the considerable morbidity experienced by many patients, particularly morbidity associated with noncardiac complications. The development of postoperative complications has been associated with an increased risk of death and prolonged hospital stay (1,2), and this is supported by our data (Table 3). Our data also show that cardiac complications are more common but are associated with less mortality and morbidity than noncardiac complications (Table 4). Patients with noncardiac complications only (Group NC) stayed in the hospital twice as long and had double the mortality rate and three times the adverse outcome rate than those with cardiac complications only (Group C). Multivariate analysis demonstrated that the difference in mortality and prolonged length of stay between complication types is not solely attributable to preoperative risk factors (Parsonnet score) or the duration of CPB. Logistic regression and odds ratio estimates demonstrated the extent to which noncardiac complications and cardiac complications associated

5 1076 CARDIOVACULAR ANESTHESIA WELSBY ET AL. ANESTH ANALG COMPLICATIONS, OUTCOMES, AND CARDIAC SURGERY 2002;94: Table 2. Incidence and Outcome of Complications by Organ Category Complication d All cases Adverse LOS b ICU days c Death outcome a n % (%) e (%) e Mean Median Mean Median None Cardiac Respiratory Infectious Neurological Bleeding Gastrointestinal Renal Miscellaneous Thrombotic a Death or hospital length of stay 10 days. b LOS hospital length of stay (excluding subjects who died in the hospital). c Total days in the intensive care unit (ICU) (excluding subjects who died in the hospital). d The specific complications listed in each category are listed in Appendix 1. Adverse outcome in the category none (no complications) is due to complications other than those listed. e Percentage of cases in this category who died or had an adverse outcome. Table 3. Risk Stratification Group Parsonnet score CPB time (min) Mean Median (IQR) Mean Median (IQR) N (4 16) (85 129) C (7 19) (89 142) NC (7 18) (92 153) B (10 23) (97 162) CPB cardiopulmonary bypass; IQR interquartile range. Only the intergroup comparisons C versus NC for Parsonnet score and CPB time and B versus NC for CPB time do not reach statistical significance (P 0.05). N no complication; C cardiac; NC noncardiac; B both cardiac and noncardiac complications. with other organ involvement (Group B) are associated with poorer outcome, independent of the effect of preoperative risk and CPB time. Patients in Group B had increased preoperative risk and longer CPB times, so it is not surprising that they had an increased rate of mortality and a prolonged length of stay. Because there was no significant difference in Parsonnet scores or CPB time between Groups C and NC, the reasons that patients were in Groups C or NC are more difficult to explain. This will be an important question to address prospectively, because the outcomes in Group NC appear to be worse. In our series, Parsonnet scores were significantly associated with death and prolonged length of stay, confirming that preoperative risk stratification can contribute to predicting both these outcomes. Including CPB time (as a surrogate marker of intraoperative events or complexity of procedure) in the logistic regression model for morbidity increased the c-index to 0.80, which is similar to risk indices that include additional intraoperative factors (5,7). However, our aim was not to develop a means of risk stratification for morbidity, but rather to use it in logistic regression. We elected to study hospital stay in survivors only to avoid underestimating the effect on hospital stay of early deaths reducing the median or mean stay. In fact our data show that those patients who died stayed in hospital for a median (IQR) of 10 (6 22) days and a mean of 18 days. Because of the relatively small mortality rate in this series, including or excluding those who died in our analysis would have made no significant difference to the distribution of hospital stay, as presented in Results. Quantifying morbidity is difficult, and using hospital stay as an index of morbidity is convenient but not ideal, because it may underestimate the degree of postoperative morbidity. In-hospital audit underestimates morbidity after cardiac surgery (21). One study (22) showed that 39% of cardiac surgery patients with a neurological complication were discharged from the hospital to an intermediate care facility. Indeed, early hospital discharge may switch the burden of care to the family (23). Bearing this limitation in mind, length of stay is an objective, continuous end-point that is not likely to overestimate morbidity, because of strong economic pressures to limit hospital stay (17). Unfortunately, however, there is still no standardized definition of morbidity, and this is why we described morbidity in terms of complication incidence, length of stay, and the composite end point of death and prolonged stay. A standardized definition of morbidity is required before any attempt can be made to report risk-adjusted morbidity rates. In conclusion, this study demonstrates that cardiac surgery with CPB is associated with infrequent mortality but considerable morbidity. Of note, we have demonstrated the extent to which this mortality and morbidity are independently associated with the type of postoperative complications, after controlling for Parsonnet score and CPB time. On the basis of these

6 ANESTH ANALG CARDIOVACULAR ANESTHESIA WELSBY ET AL ;94: COMPLICATIONS, OUTCOMES, AND CARDIAC SURGERY Table 4. Postoperative Outcomes Group Incidence, n (%) Mortality rate (%) Adverse outcome (%) Hospital LOS (days) Mean Median (IQR) Mean ICU LOS (days) Median (IQR) N 1618 (62) (5 7) (1 2)* C 552 (21.2) (6 8) (1 2)* NC 228 (8.7) (6 13) (1 3) B 211 (8.1) (8 21) (1 8) Group N refers to patients with no complications (Appendix), Group C to those with cardiac complications only, Group NC to those with noncardiac complications only, and Group B to those with both types. An adverse outcome is defined as death or prolonged length of stay (LOS). All pairwise comparisons between groups, other than those noted (*), were significantly different (P 0.001, after correction for multiple comparisons) for mortality, adverse outcomes, and hospital and intensive care unit (ICU) lengths of stay. IQR interquartile range. Figure 1. Kaplan-Meier estimated time to discharge. Group N refers to patients with no complications (Appendix 1), Group C to those with cardiac complications only, Group NC to those with noncardiac complications only, and Group B to those with both types. For clarity, the upper and lower 95% confidence limits are not shown, and the x axis is truncated at 30 days. The y axis refers to the percentage of survivors per group remaining in hospital. There is a significant difference among all four groups (P 0.001). Values for patients who died were censored. data, strategies to limit noncardiac morbidity may be expected to favorably affect length of stay after cardiac surgery. References 1. Lazar HL, Fitzgerald C, Gross S, et al. Determinants of length of stay after coronary artery bypass graft surgery. Circulation 1995;92:II Weintraub WS, Jones EL, Craver J, et al. Determinants of prolonged length of hospital stay after coronary bypass surgery. Circulation 1989;80: Hammermeister KE, Burchfiel C, Johnson R, Grover FL. Identification of patients at greatest risk for developing major complications at cardiac surgery. Circulation 1990;82:IV Chertow GM, Levy EM, Hammermeister KE, et al. Independent association between acute renal failure and mortality following cardiac surgery. Am J Med 1998;104: Dupuis JY, Wang F, Nathan H, et al. The cardiac anesthesia risk evaluation score: a clinically useful predictor of mortality and morbidity after cardiac surgery. Anesthesiology 2001;94: Hannan EL, Kilburn H, Racz M, et al. Improving the outcomes of coronary artery bypass surgery in New York State. JAMA 1994;271: Higgins TL, Estafanous FG, Loop FD, et al. ICU admission score for predicting morbidity and mortality risk after coronary artery bypass grafting. Ann Thorac Surg 1997;64: Parsonnet V, Dean D, Bernstein AD. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease. Circulation 1989;79:I Rosen HM, Green BA. The HCFA excess mortality lists: a methodological critique. Hosp Health Serv Adm 1987;32: Edwards FH, Grover FL, Shroyer AL, et al. The society of thoracic surgeons national cardiac surgery database: current risk assessment. Ann Thorac Surg 1997;63: Higgins TL, Estafanous FG, Loop FD, et al. Stratification of morbidity and mortality outcome by preoperative risk factors in coronary artery bypass patients: a clinical severity score. JAMA 1992;267: Jones RH, Hannan EL, Hammermeister KE, et al. Identification of preoperative variables needed for risk adjustment of shortterm mortality after coronary artery bypass graft surgery: the Working Group Panel on the Cooperative CABG Database Project. J Am Coll Cardiol 1996;28: O Connor GT, Plume SK, Olmstead EM, et al. Multivariate prediction of in-hospital mortality associated with coronary artery bypass graft surgery. Circulation 1992;85: Tu JV, Jaglal SB, Naylor CD. Multicenter validation of a risk index for mortality, intensive care unit stay, and overall hospital length of stay after cardiac surgery. Circulation 1995;91: Ferguson TB Jr, Dziuban SW Jr, Edwards FH, et al. The STS National Database: current changes and challenges for the new millennium. Ann Thorac Surg 2000;69: Tuman KJ, McCarthy RJ, March RJ, et al. Morbidity and duration of ICU stay after cardiac surgery: a model for preoperative risk assessment. Chest 1992;102: Silber JH, Rosenbaum PR, Koziol LF, et al. Conditional length of stay. Health Serv Res 1999;34: Jones RH, Kesler K, Phillips HR, et al. Long-term survival benefits of coronary artery bypass grafting and percutaneous transluminal angioplasty in patients with coronary artery disease. J Thorac Cardiovasc Surg 1996;111: Hill SE, van Wermeskerken GK, Lardenoye JW, et al. Intraoperative physiologic variables and outcome in cardiac surgery. I. In-hospital mortality. Ann Thorac Surg 2000;69: Hanley JA, McNeil BJ. The meaning and use of the area under a receiver operating characteristic (ROC) curve. Radiology 1982; 143: Birdi I, Izzat MB, Angelini GD, Bryan AJ. In-hospital audit underestimates early postoperative morbidity after cardiac surgery. Br Heart J 1995;74: Roach GW, Kanchuger M, Mangano CM, et al. Adverse cerebral outcomes after coronary bypass surgery. N Engl J Med 1996; 335: Lahey SJ, Campos CT, Jennings B, et al. Readmission after cardiac surgery: does fast track cardiac surgery result in cost saving or cost shifting? Circulation 1998;98:II35 40.

7 1078 CARDIOVACULAR ANESTHESIA WELSBY ET AL. ANESTH ANALG COMPLICATIONS, OUTCOMES, AND CARDIAC SURGERY 2002;94: Appendix Cardiac complications Recurrent angina Q wave infarction Cardiac arrest Intraaortic balloon pump Low-output syndrome Ventricular arrhythmias Atrial arrhythmias Respiratory complications Acute respiratory distress syndrome Pneumonia Pulmonary edema Pneumothorax Hemothorax Reintubation Tracheostomy Neurological complications Cerebrovascular accident/stroke Transient ischemic attack Coma Acute confusion or delirium Renal complications Renal failure Dialysis access line Infectious complications Mediastinitis Leg wound infection Sternal wound infection Nosocomial infection Urinary tract infection Line-related sepsis Positive blood culture Takeback for debridement was noted for sternal wound, mediastinal and leg wound infections. Gastrointestinal complications Gastrointestinal bleed Significant abdominal Laparotomy Miscellaneous complications Decubitus ulcer Adverse drug reaction Bleeding complications Resternotomy Anticoagulant-related bleeding Thrombotic complications Deep venous thrombosis Pulmonary embolus Typical angina pain not secondary to vessel occlusion or leading to myocardial infarction Myocardial infarction with development of Q waves Advanced cardiac life support; cardiac or respiratory arrest postprocedure Intraoperative or postoperative insertion Cardiac index 2 L min 1 m 2 for 24 h Significant (requiring drug treatment, pacing or defibrillation) Significant (requiring drug treatment, pacing or defibrillation) Pao 2 50 mm Hg despite fraction of inspired oxygen 50% and pulmonary capillary wedge pressure 18 mm Hg Infiltrate on radiograph and growth of respiratory pathogen or 4 growth of other pathogen Dyspnea, rales, and chest radiograph findings compatible with edema Documented by chest radiograph Documented by chest radiograph Loss of neurological function by ischemia, lasting 24 h with residual signs Loss of neurological function by ischemia, abrupt onset, for 24 h Complete mental and motor unresponsiveness to stimulation Clouding of consciousness with impaired alertness, awareness, or attention Rapid decline of renal function with creatinine increase 2 mg/dl over the preoperative level For new-onset dialysis or ultrafiltration requirement Documented infection Incisional infection requiring IV antibiotics Incisional infection requiring IV antibiotics Infection occurring at least 48 h after hospital admission Positive urine culture Pathogen isolated from blood unrelated to other infection Hematemesis, melena, anemia, and occult blood in stool Problem delaying discharge without laparotomy Disruption of skin integrity In-hospital reaction causing increased stay Documented by venogram or duplex ultrasound Documented by ventilation/perfusion scan