Effect of a Preoperative Intervention on Preoperative and Postoperative Outcomes in Low-Risk Patients Awaiting Elective Coronary Artery Bypass Graft Surgery

In Ontario, Canada, the discrepancy between the high demand for coronary artery bypass graft surgery (CABG) and the low immediate supply results in waiting lists. In 1990, a consensus panel of cardiologists and surgeons developed criteria to ensure that high-risk patients were given priority for this procedure (1). Each patient receives an acuity score that corresponds to a recommended maximum delay. Aggregated acuity scores of 4, 5, 6, and 7 indicate elective status and represent a waiting time ranging from greater than 14 days to a maximum of 6 months. The mortality rate for patients awaiting CABG has been shown to be remarkably stableapproximately 0.5% to 0.6% per year over the past 10 years (2). Despite this, however, evidence shows that patients' functional and psychological status can deteriorate during the wait for surgery (3-5). Through its effects on the autonomic nervous system, emotional stress also influences catecholamines, myocardial oxygen demand, and platelet aggregation; this may affect morbidity during the waiting period (6-8). Such factors as preoperative anxiety and little social support have adverse psychological effects during extended preoperative waiting periods and, in addition, have been found to predict poor physical recovery from heart surgery (9). Therefore, psychological factors and physical deconditioning, both of which occur during the waiting period (10-12), may negatively affect patients' in-hospital course, including length of stay. Because waiting for health services will probably continue to be a reality in publicly funded health care systems that value universal access, careful study of simple, affordable methods to improve patient outcomes during the waiting period is warranted. We examined the effect of a minimum 8-week, multidimensional, preoperative intervention on the presurgery and postsurgery outcomes of patients awaiting elective CABG. We hypothesized that a combination of exercise training, education, and social support would affect patients' physical and psychological readiness for surgery and thereby reduce postoperative length of hospital stay. We further hypothesized that the effectiveness of the preoperative intervention would be sustained into the first 6 months of the postoperative period. Methods Patients Patients were recruited from the waiting lists of all seven cardiovascular surgeons operating in the Hamilton Health Sciences Corporation surgical center, Hamilton, Ontario, Canada. Each year, approximately 1300 open-heart surgeries are performed in this center. Roughly 60% of patients awaiting CABG have elective status and are placed on the waiting list. During the time of our study, elective waiting times ranged from 3 weeks to greater than 20 weeks. Approximately 40% of elective patients are usually awaiting first-time CABG (nonvalve replacement). Only patients awaiting a first CABG whose surgery dates were at least 10 weeks away were approached to participate in our study. Patients were excluded if they were having combined CABG and valve surgery, if their ejection fractions were less than 0.40, if they could not attend the exercise classes because of geographic inaccessibility, or if they were unable to participate because of physical limitations. After these inclusion and exclusion criteria were applied, our pool of potential participants was approximately 250 patients per year. We intended to select low-risk patients because it is not common to test an exercise intervention in patients awaiting CABG. Design We designed a two-group randomized, controlled trial. Eligible patients were randomly assigned to 8 weeks of multidimensional preoperative intervention or to usual care. Those assigned to usual care were followed by their primary care physicians, cardiologists, or surgeons. During the waiting period, the intervention group received individualized, prescribed exercise training twice per week in a supervised environment; education and reinforcement; and monthly nurse-initiated telephone calls to answer questions and provide reassurance. After surgery, patients in both the treatment and control groups were given the opportunity to join the existing cardiac rehabilitation program (Appendix). Outcomes The primary outcome was postoperative length of hospital stay. Secondary outcomes were peak exercise performance, health-related quality of life, social support, anxiety, and utilization of health care services. Measurements were taken at baseline, 1 week before surgery, 6 to 8 weeks after surgery, and 6 months after surgery. All of the secondary outcome variables were measured at baseline and 1 week before surgery. At 6 weeks and 6 months after surgery, only exercise performance, quality of life, and social support were measured. Determination of Sample Size Sample size was determined by using 19941995 data on length of stay in our surgical center. According to a random sample of 20 patients undergoing elective CABG, the mean total length of stay SD was 9.4 3.5 days. On the basis of these data, and accounting for a loss of 10% to 15% of patients, we determined that a sample size of 125 patients per group had sufficient power (0.8) to detect a 1-day reduction in hospital stay (=0.05). Procedures The Research Ethics Board of McMaster University (Hamilton, Ontario) and the study hospital approved the study. On a weekly basis, staff at each of the surgeon's offices supplied the names of patients who were scheduled to wait at least 10 weeks for surgery. Patients were telephoned, and the study was explained to them. The recruitment officer was completely candid about the random assignment and the treatments that would be offered to each group. Within 1 week after giving verbal consent, patients came to the clinic to provide written informed consent. At this visit, we collected complete baseline data and patients underwent an exercise test. Baseline data included demographic information (age, sex, socioeconomic status, living arrangements, education, and employment status); medical history; past and present smoking status; and history of myocardial infarction, angina, congestive heart failure, and diabetes. Baseline data were also collected on anxiety, health-related quality of life, utilization of health care services, and social support. Data later obtained from medical records included total length of hospital stay, length of postoperative stay, number of hours spent in the intensive care unit (ICU) before receiving a discharge order, and actual hours spent in the ICU. Randomization and Blinding The study coordinator randomly assigned patients to study groups by using a concealed randomization process. A consultant prepared the randomization schedule, and assignments were sealed in opaque envelopes that were opened in sequence after consent and baseline data were obtained. Patients were not blinded to their group assignments. However, the patients' physicians (cardiologists, surgeons, and general practitioners) were blinded to group assignment and were not informed of it at any point in the study by patients or health care staff. Persons involved in offering the intervention (nurses, kinesiologists, dietitians) were aware of the patients' group assignments but had no role in determining the patients' readiness for discharge from the ICU or from the hospital; therefore, they did not directly affect the primary outcome. Assessment of Outcomes Data on length of stay were collected by individual chart review. Total length of stay and total length of ICU stay were easily determined by using admission and discharge dates. However, after discussion with the cardiovascular surgeons before the study began, we realized that total length of ICU stay would misrepresent patients' postoperative progress. On many occasions, the patient is ready for discharge from the ICU but bed or staffing issues substantially delay his or her actual departure. Therefore, we collected data on length of ICU stay in hours and, more particularly, in hours until order for ICU discharge. This required detailed chart review to locate time in and time out information as well as the time that the physician's discharge order was given. Although the physicians often did not record the times of their orders, these data were found in nurses' ICU notes. In approximately 5% of cases, the data were not retrievable and the mean time until order for discharge was imputed. Exercise performance was measured by using a symptom-limited, upright-cycle ergometer exercise test. General health-related quality of life was measured by using the Medical Outcomes Study 36-item Short Form Survey (SF-36) (13). Social support was measured by using the Interpersonal Support Evaluation List (14), and the total scale score was used in analysis. Anxiety was measured with the Spielberger StateTrait Anxiety Inventory (15), from which both a trait score and a state anxiety score were computed. The total score from the Health Services Utilization Questionnaire (16) was computed and used in the analysis (Appendix). Statistical Analysis All analyses were performed by using the SPSS statistical package (17), versions 6.0 and 8.0 (SPSS, Inc., Chicago, Illinois). We analyzed data on patients whose status was elective from study entry until 1 week before surgery (n =220). Data were complete for the primary outcome variables. When a measurement tool did not supply an approach for dealing with missing data, we used an imputation strategy, the hot deck approach (18), in which the score from a matched patient in the same group is substituted for the missing score. The defining characteristics for matching patients were age, sex, and number of bypasses required. At the measurement point 6 months after surgery, 78% of patients returned for all final assessments. Follow-up to establish vital status was complete for all patients. Data on length of stay are usually positively skewed. Therefore, we selected the MannWhitney test for non-norm