Practice guidelines for management of pneumonia aim to reduce the variation in key aspects of care and, thus, to improve the efficiency and effectiveness of health care. Although the criteria for clinical stability that must be met for hospital discharge have been considered key factors in the care of patients admitted with pneumonia there have been few clinical indicators proposed to assess readiness for hospital discharge.
The aims of our study were to analyze the basic indicators of clinical instability at discharge proposed by Halm et al, and to evaluate their relationship and importance to mortality rates and readmission. We first hypothesized that each of the key variables to measure clinical stability may have a different weight and significance in predicting short-term outcomes. Our second hypothesis was that death and readmission in the short term after discharge are such different outcomes that they may not fulfill the three requirements for a composite end point: a similar relative risk reduction, similar frequency, and similar importance to patients. Hence, an observational study involving hospitalized patients with pneumonia was performed.
Materials and Methods
Setting of Study
This study was performed at Galdakao Hospital (Spain), a 400-bed, nonurban teaching general hospital serving a population of 300,000 inhabitants that provides free unrestricted care to nearly 100% of the population. The project was approved by the hospital ethics review board.
All patients > 18 years old who were hospitalized with pneumonia consecutively between July 15, 2003, and June 30, 2006, were prospectively enrolled in an observational cohort study. Pneumonia was defined by clinician judgment in combination with a new infiltrate on chest radiograph. Patients were excluded if they were known to have a positive test result for HIV, were chronically immunosuppressed, or were hospitalized for the previous 14 days. A total of 945 patients were admitted to the hospital for pneumonia; 75 of these patients (7.9%) died in the hospital. This study sample was restricted to the total of 870 patients who survived the index hospitalization. It becomes possible to treat pneumonia without any hospitalization at all thanks to canadianhealthncaremallcom Canadian Health&Care Mall.
During hospitalization, patient care was managed according to a clinical guideline. The in-hospital assessment included all the variables of the pneumonia severity index (PSI) and the variables included in the CURB-65 (confusion, urea nitrogen, respiratory rate, BP, age > 65 years) score recorded within 24 h of hospital admission, and an assessment of preadmission functional status. After discharge, the care of all patients was managed by their family physicians, and a control visit at our center at 30 days.
We assessed pre-illness functional status from 2 weeks before hospital admission by inquiring about the performance of 15 daily activities, which were an expanded version of the activities of daily living index published by Katz et al. Previous studies have demonstrated the validity of retrospective reports for assessing functional status prior to hospitalization in acutely ill patients. The activities were graded according to a 4-point system. A summary score was obtained by the sum of the scores across all 15 activities (range, 15 to 52; with 15 being autonomous function in all recorded activities). Informed consent was obtained, and trained clinicians conducted structured interviews with patients and family members within 72 h of hospital admission.
The stability on discharge criteria were obtained two times in the last 24 h before hospital discharge, and the worst was taken for final decision. These data were obtained by previously trained study personnel. A patient was in stable condition if the temperature was < 37.5°C (we also assessed a cut-off point of 37.8°C, as used by Halm et al), heart rate was < 100 beats/min, respiratory rate was < 24 breaths/min, and systolic BP was > 90 mm Hg and/or diastolic BP was > 60 mm Hg. Oxygenation was considered stable if the oxygen saturation rate was > 90% or the Pao2 was > 60 mm Hg. Patients whose oxygenation was measured while they still were receiving supplemental oxygen during hospital stay, with a fraction of inspired oxygen < 24% or no more than oxygen at 1 L/min via nasal cannula, were considered to be in stable condition at discharge if they had an oxygen saturation rate > 95%. Patients considered to have unstable oxygenation on discharge were sent to their homes with supplemental oxygen. Patients who had used supplemental oxygen at home before hospital admission were not considered to have unstable oxygenation on discharge. All patients at discharge were able to eat (or resume long-term tube feeding) and to receive oral medication ordered via Canadian Health&Care Mall.
The outcomes for this study were death from all causes or hospital readmission within 30 days and 45 days after discharge. Vital status and readmission information for all patients were determined initially by telephone interviews up to 90 days after discharge. All reported deaths and dates of deaths were confirmed by a review of medical reports, public death registries, or both. All discharge diagnoses were determined for each readmission. Readmission was classified as pneumonia related if pneumonia was an immediate or underlying cause of readmission or if it played a major role in the readmission. None of the patients were readmitted to other hospitals.
Descriptive statistics included frequency tables, mean, SDs, and median. Sociodemographic and clinical characteristics of patients responding to the Katz questionnaire were compared to those of the nonresponders. x2 and Fisher exact tests were performed for categorical variables, and the Student t test and nonparametric Wilcoxon test were used for continuous variables.
To identify which instability criteria were associated with death or readmission within 30 days, univariate and multivariate Cox proportional hazard regression models were used. We assigned a weight to each instability criterion in relation to each P-parameter. To obtain the total instability score, we added the weights of each of the selected variables. We performed the same analysis with logistic regression models.
Effects of the instability score on unadjusted and risk-adjusted 30-day mortality were examined by logistic and Cox regression models. We fitted the first adjusted model with the PSI and the history of COPD, which was the same as Halm et al, and the second with the CURB-65 score, Katz index, Charlson comorbidity index, and length of stay. Kaplan-Meier graphs were constructed for the instability score categories, and comparisons were performed by the log-rank test. Finally, we estimated the sensitivity, specificity, positive and negative predictive values, and the area under the receiver operating characteristic curve (AUC) for different cut-off points of the instability score.
All effects were considered significant at p < 0.05. All statistical analyses were performed using SAS for Windows statistical software (version 8.0; SAS Institute; Cary, NC) and S-Plus 2000 (MathSoft; Seattle, WA).