(Circulation. 1995;92:20-24.)
© 1995 American Heart Association, Inc.
Articles |
Determinants of Length of Stay After Coronary Artery Bypass Graft Surgery
Presented at the 67th Scientific Sessions of the American Heart Association, Dallas, Tex, November 14 to 17, 1994.
From the Department of Cardiothoracic Surgery, The Boston University Medical Center, Boston, Mass.
Correspondence to Harold L. Lazar, MD, Department of Cardiothoracic Surgery, The Boston University Hospital, 88 E Newton St, B402, Boston, MA 02118.
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Abstract |
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 Top Abstract IntroductionMethods Results Discussion References |
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Background Rising healthcare costs have prompted limitations in the length of stay (LOS) for patients undergoing coronary artery bypass graft surgery (CABG). Because not all patients are candidates for early discharge, in the present study our aim was to determine factors that prolong LOS.
Methods and Results In 194 consecutive patients undergoing
CABG procedures, LOS was >7 days in 37%. Stepwise multiple regression
procedures and 
2 testing were used to determine
what factors prolonged LOS for >7 days. Preoperative factors that
significantly (P<.05) prolonged LOS included repeat CABG,
CABG plus valve surgery, congestive heart failure, preoperative
coronary care unit stay, renal failure, and
insulin-dependent diabetes mellitus. Patients with at least one
risk factor had a significantly higher incidence of LOS of >7 days
(47% versus 17%; P<.001). Significant (P<.05)
postoperative factors prolonging LOS included arrhythmias,
respiratory insufficiency, pneumonia, and wound infection. Of patients
with at least one risk factor, 83% had LOS of >7 days
(P<.001).
Conclusions The presence of certain preoperative and postoperative risk factors can be predicted to prolong LOS after CABG surgery. This should be taken into consideration when defining reimbursement policies.
Key Words: bypass • surgery • risk factors
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Introduction |
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TopAbstractIntroductionMethods Results Discussion References |
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Rising health care costs have prompted physicians and third-party payors to attempt to limit the length of stay after major surgical procedures.1 This is especially true for patients who undergo coronary artery bypass graft surgery (CABG), which is the most commonly performed major operation in the United States and accounts for considerable expenditure of health care costs.2 3 4 Currently, the majority of CABG patients are already hospitalized with unstable angina syndromes, so the preoperative length of stay is more difficult to control. Therefore, attention has been directed to curtailing the postoperative length of stay.
In 1986, we reported on the determinants of length of stay for 177 patients undergoing isolated CABG at The Boston University Medical Center.5 At that time, only 28% of CABG patients were discharged before the eighth postoperative day. Since that time, changes in health care reimbursement policies have prompted us to introduce programs such as same-day admissions, early extubation, critical pathways, and "fast-tracking" in an attempt to shorten the length of stay after CABG. Concomitantly, the profiles of patients undergoing CABG have changed, resulting in more older patients with more extensive coronary disease and unstable symptoms, increasing comorbid diseases, and a higher incidence of repeat surgery. Therefore, not all patients will be candidates for early discharge. We undertook the present study to determine what preoperative and postoperative variables would contribute to prolonged length of stay after CABG. Furthermore, we were interested to see whether the presence of certain preoperative and postoperative risk factors could predict which patients were more likely to require longer hospitalization after CABG.
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Methods |
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TopAbstractIntroductionMethods Results Discussion References |
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The records of 194 consecutive patients who had undergone a CABG-related procedure and were discharged alive from The Boston University Hospital between January 1993 and April 1993 were retrospectively reviewed. During this time, fast-track and early extubation protocols were developed in an attempt to discharge patients by the seventh postoperative day. Patients discharged after the seventh postoperative day were considered to have a prolonged length of stay. Data sheets were developed to evaluate preoperative and postoperative variables that might prolong length of stay (Tables 1
and
2).
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Surgical Protocol
All surgical procedures were performed with
a membrane
oxygenator at systemic temperatures of 34°C. Multidose cold blood
cardioplegic solutions were given antegrade, retrograde, or
antegrade/retrograde at the surgeon's discretion. Cell-saving
techniques were routinely used in all patients.
Postoperative Management
Inotropic agents were used as
necessary to maintain a cardiac
index of at least 2.0 L/m2. Patients were extubated as soon
as possible. Candidates for early extubation (6 to 8 hours after
surgery) included patients with stable hemodynamics and
no significant mediastinal bleeding and patients who were awake and
alert with normal arterial blood gases. All extubated
patients were transferred from the intensive care unit on the first
postoperative day unless the use of inotropic or vasodilator drugs was
necessary. ß-Blocking agents were instituted on the first
postoperative day in all patients with an ejection fraction of >40%.
Criteria for discharge from the hospital included stable cardiac
rhythm, an oral temperature of <99°F, hematocrit of 
25%, oral
intake of at least 1000 calories per day, successful completion of an
exercise test that included independent ambulation and the ability to
climb one flight of stairs, no significant wound complications, and
adequate home support systems.
Statistical Analysis
Values are given as mean±SD. An
association between a risk
factor and length of stay in days was analyzed with the
independent-sample t test, which was used to compare
mean length of stay for those with and those without the risk factor.
The association between risk factor and a stay of >7 days was
analyzed with the 2 test, which was used
to compare the proportion of patients with extended stays among those
with and those without the risk factor. In addition, summary
categorizations were made for any preoperative risk factor and any
postoperative risk factor. The effects of these summary risk categories
were analyzed with two-factor ANOVA (for the outcome of
length of stay in days) and multiple logistic regression (for the
outcome of length of stay of >7 days). Stepwise multiple regression
(for length of stay in days) and stepwise logistic regression (for the
categorical outcome of length of stay of >7 days) were used to
identify risk factors that had an independent effect on outcome. For
both versions of the outcome, a model was first fit using early
preoperative risk factors as predictors. A second model was then fit to
determine which postoperative risk factors contribute additional
information toward predicting length of stay while controlling for the
identified preoperative factors. All statistical analyses were
performed by Dr Timothy Heeran (Department of
Epidemiology, The Boston University School of
Public Health, Boston, Mass). Differences were considered significant
at the P<.05 level.
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Results |
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TopAbstractIntroductionMethods Results Discussion References |
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The results of the present study are summarized in Tables 1 through 4
and the
Figure. Of the 194 study patients, the
age range was from 32 to 86 years (mean±SD, 65±11.7). There were
137
men (71%) and 57 women (29%). The most frequently performed procedure
was CABG (173 patients [84%]); 18 patients (9%) underwent repeat
CABG; 8 patients (4%) underwent CABG with aortic valve replacement,
and 5 patients (3%) underwent CABG with mitral valve replacement.
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The length of stay ranged from 4 to 47 days (mean±SD, 8.7±5.9
days
[Figure]). In 69 patients (37%), the length of stay
was >7 days.
The preoperative factors that significantly prolonged length of stay
are summarized in Table 1. Univariate analyses with
2 testing identified patients with repeat CABG,
CABG plus valve surgery, congestive heart failure,
insulin-dependent diabetes mellitus, a preoperative length of stay
of >8 days, emergency surgery, creatinine level of 1.5,
transfer to the operating room from the coronary care unit, and
the need for intravenous nitroglycerin as
significant independent variables that prolonged length of stay.
When multivariate analyses were applied,
significant variables prolonging length of stay included repeat
CABG (P<.05), CABG plus valve surgery (P<.001),
congestive heart failure (P<.01), insulin-dependent
diabetes mellitus (P<.05), creatinine level of
1.5 (P<.001), and transfer to the operating room from the
coronary care unit (P<.001).
Postoperative factors that significantly prolonged length of stay are
summarized in Table 2. Univariate analysis
identified patients with arrhythmias, intubation for 48
hours, lobar pneumonia, wound infection, weight gain of 20 lb,
inotropic support for 48 hours, and myocardial infarction as
significant variables prolonging length of stay. When
multivariate analyses were applied, significant
risk factors included arrhythmia (P<.01),
intubation for 48 hours (P<.05), lobar pneumonia
(P<.001), and wound infection (P<.001).
The effects of both preoperative and postoperative risk factors in
prolonging the length of stay are shown in Table 3. In
patients with no preoperative risk factors (66), the mean length of
stay was 6.6 days, and only 18% of patients remained hospitalized for
>7 days. However, in patients with at least one preoperative risk
factor, the mean length of stay increased to 9.8 days, and 45% of
these patients remained hospitalized for >7 days (P<.001).
The group of patients without any preoperative or postoperative risk
factors had the shortest length of stay (mean, 6.3 days; 13% of
patients had a length of stay of >7 days). Patients with at least one
preoperative and one postoperative risk factor had the longest length
of stay (mean, 14.2 days; 73% of patients had a length of stay of >7
days [P<.001]). Development of a postoperative risk
factor significantly prolonged length of stay (mean, 8.2 days; 45% of
patients had a length of stay of >7 days [P<.001]),
whereas avoidance of postoperative risk factors despite the presence of
a preoperative risk factor significantly decreased length of stay
(mean, 7.1 days; 30% of patients had a length of stay of >7 days
[P<.05]).
The reason for the prolonged length of stay in the 37% of patients
hospitalized for >7 days postoperatively is shown in Table
4. The most common cause was
respiratory insufficiency, followed closely by the development of an
arrhythmia. In the 21 patients in whom an arrhythmia
extended the length of stay, 17 experienced atrial fibrillation. Wound
infection, stroke, and postoperative myocardial infarction were the
next most common variables prolonging length of stay.
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Discussion |
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TopAbstractIntroductionMethods Results Discussion References |
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In 1986, only 28% of patients undergoing CABG at The Boston University Medical Center were discharged by the 8th postoperative day.5 The majority (45%) were discharged between the 9th and 11th postoperative days, and in 79% of these patients, no identifiable reason could be determined to account for the prolonged length of stay. In the past 3 years, changes in health care reimbursement policies have prompted the introduction of various changes in the practice of cardiac surgery that have had a dramatic impact on the length of stay. All elective cases are now admitted on the same day of surgery. Anderson et al6 have shown that patients admitted for same-day surgery have a length of stay that is 1.5 days less than that for patients admitted the day before CABG. Loop et al7 also showed that same-day patients had a decreased length of stay and a significantly lower hospital bill. We continue to use blood cardioplegia with both antegrade and antegrade/retrograde techniques in the vast majority of our patients. A recent study from the Cleveland Clinic compared the use of blood cardioplegia techniques with crystalloid cardioplegia.8 Time in the intensive care unit, length of hospitalization, and length of stay outlier status were significantly decreased in the blood cardioplegia group. The net savings in hospital cost was $2196 per patient. By introducing an early extubation program, we also decreased the length of stay in the intensive care unit, which accounts for a significant percentage of hospital costs for CABG.6 9 Several factors led to a reduction in hospital stay once the patient leaves the intensive care unit. The introduction of "critical pathways" and "fast-tracking" has helped to focus on potential complications before they occur. Patients are mobilized faster, increased weight gain is treated aggressively with diuretics, and discharge planning is instituted as soon as the patient is discharged from the intensive care unit. Recent studies have shown that fast tracking results in a significant reduction in length of stay after CABG.10 11 We and others have found that nurse case managers are invaluable in making sure that patients stay "on track" on their critical pathways.12 13 In addition to tracking patients for discharge, they coordinate and screen patients for transfer to rehabilitation and chronic care units, thus minimizing length of stay in acute care facilities.
The results of the present study show that these interventions have
had a dramatic impact on the length of stay at our institution.
Compared with our earlier series, only 37% of patients remained
hospitalized past the seventh postoperative day. Similarly, there has
also been a change in preoperative risk factors that prolong length of
stay. In our earlier study, univariate analyses
identified female sex, age of 65 years, unstable angina, and
congestive heart failure as predictors of prolonged length of stay.
Because the profiles of patients who undergo CABG have changed, age and
female sex are no longer predictors of prolonged length of stay in our
present study. However, congestive heart failure and symptoms of
unstable angina, including preoperative coronary care unit stay
and the need for intravenous nitroglycerin,
continue to be predictive of prolonged length of stay. Repeat CABG,
CABG plus valvular surgery, insulin-dependent diabetes
mellitus, and creatinine level of >1.5 have also emerged
as predictors of prolonged length of stay. As in our earlier series,
patients who develop major postoperative complications, including wound
infection, pneumonia, and respiratory insufficiency, as well as
arrhythmias tend to remain hospitalized longer. Similar
findings were noted by Weintraub et al14 and Welsh et
al,15 who noted that the development of postoperative
complications was a significant contributor to prolonged length of
stay.
In contrast to earlier studies, our results indicate that the presence or absence of certain preoperative and postoperative risk factors can be used to predict which patients will require prolonged length of stay.14 Patients without preoperative risk factors who do not develop postoperative risk factors have the shortest length of stay and are more likely to be candidates for fast-track pathways. In contrast, patients with preoperative risk factors who develop postoperative complications will have the longest length of stay. However, patients with preoperative risk factors who do not develop postoperative risk factors will still have significantly shorter lengths of stay. It is this group of patients who should be targeted in an attempt to decrease postoperative length of stay. In the present study, the two most common reasons for prolonged length of stay were pulmonary insufficiency and atrial arrhythmias. To decrease postoperative respiratory complications, we have made an attempt to have all patients stop smoking for at least 1 week before surgery when possible. All in-house patients are seen before surgery by a physical therapist. Patients are mobilized by the morning after surgery; intensive pulmonary physiotherapy is instituted, and inhalant and bronchodilator therapy is used when necessary. Diuretics are used to decrease early weight gain, which may compromise pulmonary function. In an attempt to decrease the incidence of atrial arrhythmias, ß-blocking agents are instituted on the first postoperative day in patients with ejection fractions of >40%.
Despite the tremendous gains made in lowering the length of stay after CABG procedures, there still will be groups of patients who will require longer lengths of stays. Our study shows that the presence or absence of certain preoperative and postoperative risk factors can be used to predict which patients will require longer hospitalizations. Furthermore, due to the profiles of patients having surgery continuing to change as a result of increasing age and comorbid disease and the influence of invasive cardiology interventions, variables that influence the length of stay may also change. Health care providers must take these factors into consideration when defining reimbursement policies for CABG procedures.
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Acknowledgments |
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The secretarial assistance of Ellie LaBombard and the administrative support of Elizabeth Clifford are greatly appreciated.
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