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a Department of Cardiac Surgery, Saint John Regional Hospital, New Brunswick, Canada
b Department of Cardiovascular Sciences, East Carolina University and East Carolina Heart Institute, Greenville, North Carolina
Accepted for publication October 11, 2011.
* Address correspondence to Dr Rodriguez, Department of Cardiovascular Sciences and Pediatrics, East Carolina Heart Institute, 115 Heart Dr, Rm 3213, Greenville, NC 27834 (Email: rodrigueze{at}ecu.edu).
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Abstract |
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Methods: All cases of coronary artery bypass grafting (CABG), aortic valve, mitral valve, and combined CABG/valve surgical procedures performed at a single institution from July 2002 to July 2007 were identified. All-cause mortality in patients discharged alive from the hospital was determined until December 2007 through linkage with the Social Security Death Index. Patients who experienced intraoperative death or those with missing or invalid social security numbers were excluded. The definition of prICULOS was total ICULOS greater than 7 days.
Results: A total of 3,478 patients met inclusion criteria. One hundred thirty-seven of three thousand four hundred seventy-eight patients (3.9%) experienced prICULOS. These patients were more likely to be older than 70 years (55.5% versus 30.5%; p < 0.0001) and to have had recent myocardial infarction (28.5% versus 20.1%; p = 0.02), previous cardiac operation (18.3% versus 6.9%; p < 0.0001), and emergent status (9.5% versus 1.6%; p < 0.0001). They experienced greater in-hospital mortality (37.2% versus 1.7%; p < 0.0001) and those who were discharged alive had worse long-term survival (log-rank, p < 0.0001). After risk adjustment, prICULOS emerged as a significant predictor of in-hospital death (odds ratio [OR] 20.9; 95% confidence interval [CI], 12.9–33.7) and decreased long-term survival (hazard ratio [HR] 2.9; 95% CI, 2.0–4.3).
Conclusions: Patients with prICULOS after cardiac operations have worse overall outcomes. These data may be used to inform these patients and their families of realistic expectations regarding their clinical course.
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Introduction |
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The purpose of this study was to examine the effect of prICULOS on short-term and long-term outcomes in a current cohort of patients undergoing cardiac surgical procedures at a single institution.
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Material and Methods |
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Patients who experienced intraoperative mortality (n = 16) or those who had a missing or invalid social security number (n = 410) were excluded from analysis. The remaining patients (n = 3,904) formed the final study population.
Variable Definitions
PrICULOS was defined as any total stay in the ICU after cardiac operation exceeding 7 days. The period greater than 7 days did not have to occur consecutively. As such, instances in which a patient was initially discharged from the ICU within 7 days and then readmitted to the ICU for a total stay of greater than 7 days were considered as being prICULOS. In the literature, a variety of times have been used to define prICULOS, ranging from 48 hours [12] to 14 days [7]. The authors arbitrarily chose 7 days because they felt that this best represented an ICULOS that would have been the result of significant postoperative complications and that would ultimately have an impact on long-term survival were the patient to survive to the point of discharge.
The primary outcome of interest was long-term all-cause mortality among those patients who were discharged alive from the hospital. Secondary outcomes of interest included measures of in-hospital morbidity (atrial fibrillation, renal failure, perioperative transfusion, deep sternal wound infection, permanent stroke, reoperation for bleeding, prolonged ventilation greater than 24 hours, respiratory failure requiring reintubation, readmission to ICU) and in-hospital mortality.
Statistical Analysis
Patients with prICULOS were compared with those with normal ICULOS on the basis of preoperative, intraoperative, and postoperative characteristics. Continuous variables were compared using the 2-sided t test for mean values and the Kruskal-Wallis test for median values, whereas categorical variables were compared using the 
2 test and Fisher's exact test.
To further determine the effect of prICULOS on in-hospital mortality, a nonparsimonious multiple logistic regression model was constructed. Kaplan-Meier survival curves and a nonparsimonious Cox proportional hazards model were then constructed to determine the effect of prICULOS on long-term all-cause mortality after initial discharge from the hospital. All recorded preoperative variables were included in the multiple logistic regression and Cox proportional hazards models. This all-inclusive modeling methodology was used because it was not the intent of the authors to identify significant independent predictors of either in-hospital mortality or long-term survival but rather to determine the risk-adjusted effect of prICULOS on these outcomes of interest.
Statistical significance was defined at a p value less than 0.05. All statistical analyses were performed using SAS, version 9.2 (SAS Institute, Cary, NC).
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Results |
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A total of 137 of 3,478 of patients (3.9%) experienced prICULOS, of whom 43 of the 137 (31.4%) had an initial consecutive ICULOS greater than 7 days. Median ICULOS was 20 days in patients with prICULOS and 1 day in patients without. Patients with prICULOS were more likely to be older than 70 years of age; to be women; to have comorbid disease in the form of diabetes, renal failure, cerebral vascular disease, chronic lung disease, and congestive heart failure; and to have an urgent or emergent presentation at the time of surgery (Table 1). Patients with prICULOS were also more likely to have had previous CABG or valve surgery, or both. Intraoperatively, patients with prICULOS appeared more likely to have undergone mitral valve replacement or a combined CABG/valve procedure (Table 2). They also had significantly longer cross-clamping and total bypass times. Postoperative in-hospital outcomes were uniformly worse among patients with prICULOS (Table 3). Of note, in-hospital mortality in patients with prICULOS was 37.2% compared with 1.7% in those without. After adjustment for differences in baseline clinical characteristics, prICULOS emerged as an independent predictor of in-hospital mortality (OR 20.9; 95% CI, 12.9–33.7).
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Comment |
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A few studies have presented favorable results among patients with prICULOS who were eventually discharged from the hospital [2, 8, 9, 11]. However the majority of studies confirm the findings presented in this study: patients with prICULOS have worse in-hospital and long-term outcomes [1, 3–7, 10, 12, 15]. The resulting burden on patients and their families and the significant increase in cost to the health care system [4, 10, 16] have prompted the creation of numerous risk-predictive models designed to identify those patients at greatest risk for experiencing prICULOS [6, 17–24].
It remains unclear as to how the findings from this study may be implemented in a clinical setting. For patients who would be identified before operation as being at increased risk for prICULOS, a more thorough or "informed" consenting process could be carried out such that the patient would be aware of the increased risk of being admitted to the ICU for a prolonged period. In turn, this would allow patients and their families to be better prepared for the postoperative period that lay ahead or for patients who had a legitimate alternative therapeutic option to refuse operation altogether. For those patients who had already undergone cardiac operations and were admitted to the ICU for greater than 7 days, the surgeon or intensivist, or both, may take the findings from this study and proactively approach the patient and their family regarding early withdrawal of care in light of the patient's poor in-hospital and long-term prognosis.
Of note, this study is one of the first, to our knowledge, to use a linkage between the STS database and an administrative data registry, such as the Social Security Death Index, to gain long-term survival data. This study demonstrates the immense utility of such a linkage in following patients long term and determining the effect of cardiac surgical interventions beyond the point of discharge. It is envisioned that in the near future, the STS will routinely establish similar links to administrative data sets such as the Centers for Medicare and Medicaid Services Medicare database [25] and the Social Security Death Master File [26] in order to allow all participants of the STS database to determine long-term survival and freedom from readmission in patients who have undergone cardiac operations.
This study does have the following limitations. First of all, the clinical indication underlying the patient's admission to the ICU is not recorded. When no institutional policy existed regarding which patient was to be admitted to the ICU and which patient was to be admitted to the ward, the potential exists for patients to be managed differently depending on the individual care provider and the particular threshold for maintaining a patient in the ICU versus discharging them to the ward. It is for this reason that the authors chose an ICULOS greater than 7 days because this cutoff would more accurately represent a patient population that experienced a complicated enough postoperative course to warrant a significantly prolonged LOS in the ICU.
Second, cause and location of death in patients with prICULOS who were successfully discharged from the hospital are not known. What is known, however, is that the greatest burden of mortality in these patients occurs within the first year after discharge from the hospital. Further study is needed to better understand the mechanism of death in these patients during this period. In the meantime, interventions may be proposed that may ultimately reduce the patient's long-term mortality risk. Specifically, patients with prICULOS may be subject to increased follow-up during the first year after discharge from the hospital. In addition to routinely scheduled follow-up appointments, recurring appointments may be scheduled throughout the year to assess clinical and functional status to proactively identify medical issues that may be potentially fatal in this high-risk patient population.
In conclusion, patients with prICULOS experience worse in-hospital and long-term outcomes. These data may be used to inform these patients and their families of realistic expectations regarding their clinical course and may appropriately guide decisions regarding pursuit or withdrawal of long-term care.
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This article has been cited by other articles:
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  G. Soppa, C. Woodford, M. Yates, R. Shetty, M. Moore, O. Valencia, N. Fletcher, and M. Jahangiri Functional status and survival after prolonged intensive care unit stay following cardiac surgery Interact CardioVasc Thorac Surg, June 1, 2013; 16(6): 750 - 754. [Abstract] [Full Text] [PDF]
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