Randomized Assessment of Resource Use in Fast-track Cardiac Surgery 1-Year after Hospital Discharge

After institutional review board approval and written informed consent, 120 patients younger than age 75, who were initially randomized to an FTCA group or a conventional anesthetic management group for primary elective CABG surgery 7,8between 1993 and 1995, were followed for 1-year after index surgery.

Premedication included 2 mg sublingual lorazepam 1 to 2 h before surgery. Radial and pulmonary artery pressure was monitored in all patients.

Anesthesia was induced with fentanyl 15 μg/kg and pancuronium 0.15 mg/kg, and maintained with 0.5–2.0% end-tidal isoflurane. A propofol 2–6 mg · kg⁻¹· h⁻¹infusion was commenced after initiation of cardiopulmonary bypass (CPB) and continued until 1–4 h postoperatively in the postcardiac surgery unit (PCSU). Postoperative analgesia was maintained with intravenous morphine 1–4 mg/h. Patients were assessed for tracheal extubation within 1–6 h after arrival in PCSU.

Anesthesia was induced with fentanyl 50 μg/kg and pancuronium 0.15 mg/kg and maintained with midazolam 0.1 mg/kg and 0.5–2.0% end-tidal isoflurane as required. Postoperative analgesia and sedation were achieved with morphine 2–10 mg/h and midazolam 1–3 mg/h. Patients were assessed for tracheal extubation at 7:00 am the next morning.

Both groups received indomethacin 50–100 mg suppositories for analgesia. Shivering was treated with meperidine 25–50 mg. Sedation was titrated to maintain a Ramsey score of 3 to 4. 9 

All patients underwent a median sternotomy, with harvesting of saphenous veins and internal thoracic arteries as conduits. Myocardial protection was achieved with intermittent antegrade cold blood cardioplegia infusion through the aortic root, and systemic temperature was allowed to drift to 33°C during CPB. Hematocrit was maintained between 20–25%. CPB flow was maintained at 2.0–2.5 l · min⁻¹· m⁻²and perfusion pressure between 50 and 70 mmHg. Patients were rewarmed to 37°C before removal of the aortic cross-clamp and weaning from CPB. Management of the separation from CPB and in particular, the choice of inotropes was at the discretion of the anesthesia care team.

Perioperative data collection during the surgical course from hospital admission to discharge has been previously described. 7,8Follow-up data were obtained through linkage to administrative databases held at the Institute for Clinical Evaluative Sciences [ICES], which serves as Ontario's main nongovernmental health data custodian. The relevant databases are listed as follows:

1. Canadian Institute for Health Information (CIHI) Hospital Discharge database: includes computerized abstracts of all general, rehabilitation, and convalescent hospital admissions and major outpatient procedures.

2. Ontario Drug Benefit Claims database: includes prescription drug use among trial enrollees aged 65-yr and older.

3. Ontario Health Insurance Plan (OHIP) database: inpatient and outpatient claims for physician services.

4. Ontario Registered Persons database: serves as both a linkage file and an accurate source for vital statistics.

Patients’ names, chart numbers, dates of birth, gender, and dates of admission and discharge were obtained from the prospective randomized trial database and medical records for the index admission. These identifiers were linked to the Registered Persons Database to obtain an encrypted health care number. As a safeguard against violation of patient confidentiality, these names were then stripped from the file and the anonymized file was transferred to another programmer at ICES. The resulting file was then used to follow health service use by those individuals over a 1-year period from index hospital discharge.

We predetermined that three temporal periods would be examined. The 0- to 3-month period reflects the continuing recovery phase and early postoperative complications with short to medium term effects. The 0- to 12-month period reflects the additional effect of ongoing disease processes, late complications, complications with long-term consequences, and overall patient health and severity of illness. Along with these two periods, we also examined the 3- to 12-month period (reported selectively below) to isolate any late effects.

Major morbidity was assessed by comparing rates of readmission for primary cardiac diagnoses and the downstream use of major procedures (i.e. , coronary angiograms, PTCA, and repeat CABG). Mortality data were also examined.

We examined overall counts of any physician visits (both in general and also considered separately for family physicians/GPs vs.  specialists); numbers of readmissions to, and transfers to other acute care institutions or to rehabilitation or convalescent facilities after the index CABG; at any point during the defined follow-up periods and for the full year.

Average resource use was also analyzed as hospital-bed days per enrollee; Ministry of Health expenditures per patient on physician services as calculated from the relevant Ontario Health Insurance Plan (OHIP) fee schedule on claims submitted for trial enrollees; and average drug ingredient expenditures for cardiac drugs per enrollee aged 65 or older, as determined from Ontario Drug Benefit claims. All costs are in Canadian dollars.

Analyses of the data were performed before breaking the randomization code, thus the identity of the two groups under study was not known during the analysis. The SAS statistical software package (SAS Institute, Cary, NC) was used for data extraction and analysis. Since the data were not normally distributed, the nonparametric bootstrap analysis 10was carried out to compare the means of the different study outcomes between the FTCA and conventional. Five thousand bootstrap resample was used in the analysis. P  values and 95% confidence intervals are reported for each outcome. Data are expressed as mean (SD) or else indicated.

The study population consists of 120 elective CABG patients, evenly randomized according to a computer-generated code into the early and conventional studied groups. The two groups had comparable demographic data: age (59.3 ± 8.8 vs.  61.2 ± 8.7 yr old), weight (79.5 ± 14.4 vs.  78.7 ± 13.7 kg), equal distribution of ventricular function grade, number of grafts (median 3.7 [range 1–5]vs.  median 3.7 [range 1–5]), CPB time (84.8 ± 28.3 vs.  86.8 ± 25.5 min), aortic cross clamp time (62.1 ± 19 vs.  64.1 ± 19.5 min), and treated complications in the intensive care unit (ICU) postoperation respectively.

Postoperative extubation time (4.1 ± 1.1 vs.  18.9 ± 1.4 h, P < 0.02), and hospital lengths of stay (7.55 ± 2.87 vs.  9.95 ± 7.10 days, P < 0.02) were significantly shorter in the FTCA group. Nine patients in each group did not satisfy extubation criteria within the defined period after surgery; however, these patients had comparable causes of extubation failure (resternotomy for bleeding, low cardiac output syndrome, significant A-a oxygen gradient, pneumonia, CVA). A total of four patients died in the hospital after surgery. Three patients were in the conventional group and one in the FTCA group. The causes of death were perioperative myocardial infarction (one patient in each group) and stroke (two patients in the conventional group).

None of the remaining 116 patients who were discharged from the hospital died during the 12-month follow-up period.

During the first 3 months after discharge, 5 (8.3%) patients from the FTCA group and 8 (13.3%) from the conventional group were readmitted to acute care hospitals. By 1 yr, the FTCA and conventional groups increased to 15 (25%) and 15 (25%) patients respectively (table 1). However, the mean length of stay for acute care readmission was significantly shorter in the FTCA group than in the conventional group at 3 months and at 12 months (table 1). The discharge diagnoses for readmissions to acute care hospitals are listed in table 2.

Two patients from the FTCA group and nine patients from the conventional group were transferred to rehabilitation facilities after discharge from the index surgery of the acute care hospital (table 3). The number of patients did not change during the follow-up period. Differences in average transfer rates rehabilitation center LOS and total rehabilitation center LOS all favored the FTCA group (table 3).

Frequency of outpatient physician visits during the 3 month and 1-yr periods after index CABG surgery are shown in table 4. There was increased frequency of outpatient specialist visits in the FTCA versus  the conventional group; but there was no difference between the two groups with respect to general practitioner visits from index surgery to 1-yr follow-up.

Claims submitted to OHIP for procedure fees and professional services are summarized in table 5. Both groups were comparable with respect to out-of-hospital incurred OHIP costs during the 3 and 12-month follow-up periods, but the in-hospital OHIP claim numbers and costs favor the FTCA group.

A list and frequency of the most commonly prescribed cardiac drugs are shown in table 6. There was a similar distribution of cardiovascular drug use for patients aged 65 and older between the two groups. The most commonly used drugs after hospital discharge included aspirin, β-blockers, and digitalis preparations.

Total cost was based on in-hospital and out-of-hospital OHIP charges, rehabilitation facilities, and indirect hospital budget costs. Daily cost in a surgical ward of an acute care hospital has been previously estimated 7as $518.90 and that of rehabilitation center as $400.00. Patients in the FTCA group used significantly fewer resources at both the 3 month and 1-yr follow-up periods (table 7).

This study provides data concerning resource use during a 3-month and 1-year follow-up of patients after index CABG surgery randomized to FTCA versus  conventional anesthetic management. Our findings indicate that FTCA patients require significantly less resource use during both the first 3-months until 1-yr after elective CABG surgery.

The strongest predictors of cost for cardiac surgical patients are hospital LOS, intensive care unit (ICU) LOS, operating room time, patient age, and postoperative complications. 7,11,12Our earlier studies have demonstrated that early extubation anesthesia shortened postoperative LOS, resulting in reduction in health care resource use with associated potential cost savings. 7,8The predominant saving was from reduction in ICU costs. Other savings were reduced costs for respiratory therapy and laboratory blood tests. In our experience, early extubation allowed an increase in caseload with significantly fewer cardiac surgery cancellations (0.3%vs.  2.0%) when compared with the conventional extubation practice. The ICU readmission rate was actually 28% lower among patients undergoing early extubation anesthesia. 7In 885 consecutive CABG patients undergoing FTCA, 25% had delayed extubation, 17% had prolonged ICU LOS, and 2.6% died. The risk factors of delayed extubation were increased age, female gender, postoperative use of intraaortic balloon pump, inotropes, bleeding, and atrial arrhythmia. The risk factors of prolonged ICU LOS were those of delayed extubation plus preoperative myocardial infarction and postoperative renal insufficiency. The risk factors of mortality were female gender, emergency surgery, and poor left ventricular function. 13This further supports the perioperative safety and effectiveness of FTCA. The fast-track cardiac anesthesia has also been demonstrated to have a lower incidence of the feared complication of intraoperative recall in cardiac surgery. 14 

Does this promising strategy promote significant cost saving or merely cost shifting? The work by Jenkins et al.  antedates the reintroduction of early extubation practice. 15Wahl et al.  found significant impact on long-term survival and functional ability in a small cohort of patients sustaining major complications requiring prolonged ICU stays after cardiac surgery. 16Wahl et al.  did not specifically address the impact of early versus  conventional extubation. In an observational study, Lahey et al.  reported a 20.9% hospital readmission rate, and 49% readmission rate to outside hospitals after FTCS. However, their study covered only a 30-day post-discharge period and the sole outcome measure was in-patient hospital readmission data. 17 

Ott et al.  reported a 29% discharge rate in 100 patients by postoperative day 3, 18while Walji et al.  coined a new acronym of “ultra-fast tracking” and reported that 56% of 258 patients could be discharged by postoperative day 4 with 23% discharged by postoperative day 2. 19Again, long-term outcome data for these reports are lacking.

The Canadian health care system, with its universal public coverage of hospital and physician services, generates administrative data that are a unique tool for longitudinal follow-up of patients and resource use analysis. Drawing on linkage from a randomized trial to these administrative databases, we have now demonstrated that FTCA does not lead to increases in costs during the 1-yr follow-up after CABG surgery.

The major costs after discharge from hospital were attributable to physician OHIP billings for outpatients and hospital costs for readmitted patients. It is difficult to determine in advance which patients are more likely to require readmission to either acute care hospital or a transfer to rehabilitation facilities after surgery. We found that 25% of patients in both groups were readmitted to acute care hospitals during the 1-yr follow-up period. Readmission rates were similar between the two groups although the readmission diagnoses varied widely. Fewer than half of all readmissions were related to coronary artery disease. These findings are in concordance with other studies of similar patient populations. 17,20,21Significantly fewer patients were transferred to rehabilitation centers, comprising 3.3% and 15% in the FTCA and conventional groups respectively. Actual dollar costs were defined as a sum of OHIP charges and direct fixed costs per each day of stay. Although the OHIP charges were similar between the two groups, savings in the FTCA group were made by a reduction in hospital budget expenditure, primarily caused by decreased LOS in the rehabilitation centers.

The number of CABG surgeries continues to increase in our aging population. This surgery consumes more health-care resources than any other single treatment. 22The 1-year follow-up usage costs rank fourth after operating room coasts, cardiovascular ICU costs, and postoperative ward costs in elective CABG surgery. Patient readmissions to acute care hospitals and rehabilitation facilities were the two major contributors to the total postdischarge costs. Further research should be directed to provide a method to identify individuals at risk for substantial long-term morbidity and necessity for readmission to health care facilities.

One limitation of our study is that the drug costs after CABG surgery were not analyzed for all subjects. However, the drug usage in patients 65 yr or older was not different between the two groups. A second limitation is that our results cannot be generalized and apply only to the patient population studied (< 75 yr olds undergoing elective CABG surgery). Finally, this study is not designed to determine differences in the incidence of complications such as myocardial infarction, cerebrovascular accident, and death.

We emphasize that we are not seeking to reduce all services to a single dollar denominator. Cost of cardiac surgery may be calculated precisely in some circumstances, with individual assessments of direct and indirect variable and fixed costs. However we believe a pragmatic approach to profiling major resource consequences and third party payer expenses is sufficient for our purposes.

Our sample size is inevitably constrained by the original sample size of the randomized trial. Our statistical approach was to minimize tests with P  values, but to emphasize the absolute and relative intergroup differences, and to look for consistency in the comparisons drawn. If, as we expected, virtually none of the comparisons showed any meaningful differences, this could be taken as strong prima facie  evidence in support of the null hypotheses that motivate the study. Since the data were not normally distributed, sensitivity analysis using a permutations test was carried out, which showed that similar results were obtained. The nonparametric bootstrapping method we use in calculating the P  values and the 95% confidence intervals for the difference of means between groups is a very robust and powerful data-based simulation approach. 10Five thousand bootstrap resamples were used in the computation in this study.

No other randomized data are available for linkage to such a comprehensive group of administrative databases. It will be difficult to ever answer these questions definitively using nonrandomized data alone, because of the potential for confounding by selection biases. Thus, while an observational long-term comparison of the two extubation strategies could have greater power, its findings would be considerably more credible if they were consistent with findings from this randomized comparison.

In this prospective randomized study, we have demonstrated that fast-track cardiac anesthesia and surgery is a safe practice that decreases resource use after patient discharge from the index hospitalization over a 1-year follow-up period.

The authors thank Jennifer Bruce, M.D. (Cardiac Anesthesia Fellow, Department of Anesthesia, Toronto General Hospital, Toronto, Ontario, Canada) for retrieving missing data from the medical record.