Outcomes and Cost-effectiveness of Initiating Dialysis and Continuing Aggressive Care in Seriously Ill Hospitalized Adults

The development of renal failure requiring dialysis in the setting of intensive treatment for serious illness is a poor prognostic sign [1-5]. The decision to initiate dialysis in this context requires assessment of the patient's likelihood of survival with maximal support and determination of the usefulness and appropriateness of continuing aggressive care. This decision often represents a clinical cross-roads at which patients and their families and physicians face the difficult choice between one course of treatment focused on extending life and another focused on maximizing patient comfort and allowing death to occur. The quality of these decisions can be enhanced by improved understanding of expected outcomes of aggressive treatment. Information about the cost-effectiveness of initiating dialysis and continuing aggressive care for seriously ill hospitalized patients with renal failure may also prove useful to society as decisions about how best to allocate finite health care resources become increasingly difficult to make. We examined clinical outcomes and estimated health care costs for 490 seriously ill patients who developed renal failure requiring dialysis. We stratified patients according to an objective estimate of prognosis and determined the cost-effectiveness of initiating dialysis and continuing aggressive care in patients who were at low, average, and high risk for dying within 6 months. Methods Patients We studied seriously ill patients enrolled in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT) who had renal failure after enrollment and were treated with hemodialysis or peritoneal dialysis. Patients who were already undergoing dialysis at the time of hospital admission were excluded. The Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatment was a prospective study of outcomes, preferences, and decision making for seriously ill hospitalized adults. Full descriptions of the objectives and methods of SUPPORT have been published elsewhere [6, 7]. Inpatients were enrolled prospectively from June 1989 to January 1994 at five geographically diverse academic medical centers. During the intervention phase of SUPPORT, clinicians who had been randomly assigned to the intervention group were given information about their patients' prognoses and preferences for care; skilled nurses facilitated communication between patients and clinicians. Because the intervention did not affect mortality or resource use, we included patients in the intervention and control groups in our analyses. Patients were eligible for SUPPORT if they were 18 years of age or older and met defined criteria for at least one of nine diagnostic categories: acute respiratory failure, chronic obstructive pulmonary disease, congestive heart failure, cirrhosis, non-traumatic coma, metastatic colon cancer, advanced non-small-cell lung cancer, multiorgan system failure with sepsis, or multiorgan system failure with malignancy. Specific diagnostic criteria [6] were designed to identify patients at late or advanced stages of illness who, on average, had an estimated 6-month survival probability of approximately 50%. All patients were screened for eligibility at hospital admission; patients in intensive care units were screened daily. Eligible patients who were discharged or died within 48 hours of study entry were excluded from SUPPORT and were not available for inclusion in our analyses. The design of SUPPORT was approved by the institutional review boards of the participating hospitals, and informed consent was obtained verbally before interviews were conducted with patients, their families, and their physicians. Data Collection Data were collected by chart abstraction and interview. Research nurses reviewed medical records throughout patient hospitalization and abstracted data on patient diagnoses; comorbid conditions; and Acute Physiology Scores [8] on study days 1, 3, 7, 14, and 25. Comorbid conditions (such as diabetes mellitus, congestive heart failure, and stroke) were abstracted by chart reviewers by using a list that had been developed as part of the APACHE (Acute Physiology and Chronic Health Evaluation) II scoring system; a comorbidity score was calculated by a simple count of comorbid conditions [9]. The Acute Physiology Score has been previously shown to predict in-hospital mortality; a higher score indicates increased risk. Detailed data on resource utilization that included a revised version of the Therapeutic Intervention Scoring System (TISS) were also collected on study days 1, 3, 7, 14, and 25. The Therapeutic Intervention Scoring System, an additive measure of intensity of resources used, assigns 1 point for minor interventions (such as pulse oximetry, physical therapy of the chest, and peripheral intravenous therapy) and 2 to 4 points for more substantial interventions (such as intubation, thrombolytic therapy, endoscopy, and surgery). This system has been shown to be a valid and reliable measure of hospital resource use [10, 11]. Hospital charts were also reviewed periodically during patient hospitalizations and retrospectively to determine whether hemodialysis or peritoneal dialysis had been initiated. Trained interviewers questioned patients and their surrogates. A surrogate was defined as the person who would make decisions on the patient's behalf if the patient were unable to do so. Patients were not interviewed if they were unable to communicate because of coma, intubation, cognitive impairment, or other reasons. Data gathered at the initial interview, conducted with the patient or surrogate between study day 2 and day 6, provided information on the patient's functional status 2 weeks before study entry, as measured by a modified version of the Katz Index of Activities of Daily Living [12, 13]. Interviewers also obtained this information 6 months after study entry. When a patient's report was unavailable, we substituted a surrogate's report of the patient's abilities to perform activities of daily living. Surrogate reports of patient functional status before admission were used for 279 of the 345 patients for whom we gathered information at baseline and for 32 of the 94 patients for whom we reported functional status at the 6-month follow-up visit. Interviewers asked patients to rate their quality of life as excellent, very good, good, fair, or poor. To measure utilities (quality-of-life weights) [14-16], patients were asked to state the amount of time spent in excellent health that they would equate with living for 12 months in their current state of health (a time-tradeoff question). A patient who was willing to trade 12 months in his or her current health for 6 months in perfect health, for example, would have a utility of 0.5 (6 12). Cost Estimates For each patient, total hospital charges were gathered from the billing systems of participating hospitals for the index hospitalization and for all readmissions to the same hospital during the 6 months after study entry. Hospital costs were estimated by adjusting charges using Medicare cost-to-charge ratios for UB82 (Uniform Bill 1982) cost centers at each participating hospital. For the four patients for whom no billing information on the index hospitalization was available, we imputed hospital costs on the basis of a linear regression model that considered length of stay and average TISS score after dialysis was initiated. We transformed all estimated costs into 1994 U.S. dollars using the medical component of the consumer price index. From the cost of the index hospitalization, we estimated hospital costs incurred after dialysis was initiated. Hospital costs have been shown to be highly correlated with the product of the length of stay and average TISS score [7]. We assumed that this relation would hold for the portion of the hospitalization that occurred after the initiation of dialysis. Therefore, we estimated the cost of the portion of the index admission incurred after the initiation of dialysis by using the following equation: Cost = total cost of index hospitalization x [length of stay x TISS score after dialysis] [length of stay x TISS score for entire hospitalization] Data on hospital costs were collected for readmissions to the study hospitals during the 6-month SUPPORT period and were used to estimate additional hospital costs incurred during the first 6 months of follow-up. These cost estimates were based on the mean number of readmissions between discharge from the hospital and the end of the 6-month study period multiplied by the mean cost of hospitalization for patients who had only one readmission (62% of patients had no readmissions, 22% had one, 13% had two to three, and 3% had four to five). We estimated the cost of each readmission on the basis of patients who had only one readmission, because available cost data included only aggregated costs for all readmissions. Hospital costs beyond 6 months were estimated from Medicare data that reported annual hospital costs for patients with end-stage renal disease who were treated with dialysis [17]. We assumed that although most patients in our cohort would not require long-term dialysis, the nature of the illnesses that qualified them for SUPPORT suggested that they have chronic illness and would require hospitalization at a rate similar to that of patients who had a serious illness, such as dialysis-dependent kidney disease. We also assumed that patients would not receive a kidney transplant. For survivors who remained dialysis-dependent, we estimated outpatient costs of long-term dialysis as follows. In a comprehensive cost analysis comparing the costs of dialysis with the costs of transplantation, we estimated the total annual cost of dialysis to be $32 800 in 1989 dollars ($46 322 in 1994 dollars) [17]. Because 41% of those costs were for inpatient care, we subtracted 41% from this figure to avoid double counting inpatient