The mean total cost of hospitalization was $18,086 (SD $26,736), with a range from $762 to $544,797 and a median total cost of $10,454. Change in median cost is reported in this study due to the wide variability in cost. This wide range may be due in part to several factors. The setting is a large academic referral center and 35 percent of the hospitalizations included invasive diagnostic procedures for heart failure (e.g., cardiac catheterizations and coronary arteriography) while 60 percent included invasive cardiovascular therapeutic procedures (e.g., operating room procedures related to open heart surgery and angioplasty and peripheral vascular surgeries), the latter having the greatest impact on hospital median cost of any single variable included in the model.
The study included 1,435 hospitalizations by 1,075 patients. A total of 183 variables were entered into the analysis with 31 significantly associated with total hospital cost in the final model (). The mean age of the sample was 72.7 years, consistent with other studies (Munger and Carter 2003
). A younger age was significantly associated with greater cost with initial bivariate analysis (p
= .005), also consistent with other reports (Wexler et al. 2001
), but when other patient characteristics variables were added, this association disappeared. None of the patient characteristics were significantly related to cost in the final model (see ).
Only two clinical conditions remained in the final model: the comorbidity of deficiency anemia and severity of illness (). Of the 30 comorbid conditions used in the Elixhauser et al. (1998)
method, 27 were related to hospital cost at p
≤.15 in step one bivariate analysis, but only one, deficiency anemia, remained when all variables were entered sequentially in the final model (). Deficiency anemia
was associated with a 5 percent increase in median cost in the final model with an estimated additional cost of $536 for heart failure patients with this comorbid condition (). The clinical condition, severity of illness
, was significant in step one bivariate analysis and also was significant in the final model (see ). However, there were no statistically significant differences in the final model between the costs of higher levels of severity when compared with minor levels of severity ().
Two of the four nursing unit characteristics were significant in the final model. The number of units resided on during hospitalization was significantly associated with increased hospital cost when the patient was on 2, 3, or 4 units. Residing on 2 units (p = .0015) added about 10 percent to median cost, or an estimated $1,007; residing on three or 4 units added about 17 percent, or $1,748 to median cost per hospitalization (p = .0001) (). Interestingly, the cost difference for 5 or more units added only about 3 percent to median cost and was not significant. The variable registered nurse (RN)/patient dip proportion was also significantly associated with increased cost in the final model (p<.0001) (). The mean RN/patient dip proportion, which represents the largest drop in available RN care during a hospitalization, was 0.4321 with a range of 0.04–0.89. The larger the RN dip proportion, the fewer RN hours available for patient care. For every 0.2 increments in RN dip proportion value, there was a 15.2 percent increase in median cost per hospitalization, or $1,589 (). The RN to patient ratio, which measures the overall amount of RN hours of care to number of patients, was not significantly related to cost.
Medical, pharmacy, and nursing treatments were each significantly associated with total hospital cost ( and ). The total number of medical procedures was associated with cost (p<.0001); with the addition of each medical procedure, median costs were estimated to increase $623 (see ). Types of medical procedures included both medical and surgical procedures. There were 123 different types of medical procedures performed, for a total of 5,193 medical and surgical procedures for the 1,035 heart failure patients. To distinguish between the cost effects of nonsurgical versus surgical procedures, the different types of procedures were grouped into nine subgroups (see ). Three of these nine groups were significantly associated with cost; two of the three were invasive ( and ). Noninvasive heart failure diagnostic procedures, such as echocardiograms and radioisotope scans, were associated with an increase in median cost of about $800, or 8 percent; Invasive cardiovascular diagnostic procedures (e.g., coronary angiography) were associated with an increased cost of $736, or 7 percent; and invasive cardiovascular therapeutic procedures (e.g., angioplasties, open-heart surgeries) were associated with an increased median hospital cost of $5,294.
The number of different medications used during hospitalization and several specific medications were significantly related to cost ( and ). The addition of any one unique type of medication added $179 to the median costs. Miscellaneous GI (gastrointestinal) medications reduced median costs by over $1,000 per hospitalization. Benzodiazepines were used in 57 percent of hospitalizations at an estimated additional cost of $885 per hospitalization. Nursing interventions included in the study were those used in at least 5 percent of the hospitalizations. The number of different nursing interventions employed during the hospital stay, was statistically significant, and associated with an estimated increased cost of $289 for each additional type of nursing treatment (p<.0001) ( and ).
Ten types of nursing interventions were significantly associated with cost in the final model ( and ). The average number of times the intervention was used in 24 hours (use rate) was reported in quartiles (for interventions used in ≥95 percent of the hospitalizations) or in thirds (for interventions used in <95 percent but ≥5 percent of hospitalizations) (see further explanation in the Supplementary Material Appendix A
). Follow-up tests for these 10 were conducted by use rate categories. Six of the 10 interventions were also significant for use rate effect on cost (): Fluid Management
, Pressure Ulcer Care
, Oral Health Restoration
, Bowel Management
, Infection Protection
, and Medication Management
(). The Fluid Management
intervention, used in 99.7 percent of hospitalizations, was significantly associated with cost (p
= .017). When comparing a daily use rate of 6.08 times/24 hours with a daily use rate of 1.19 times/24 hours, the Fluid Management
intervention was estimated to save $870 per hospitalization (see ). Performing this nursing intervention two or more times a day is estimated to save $571–$870 per hospitalization. Pressure Ulcer Care
was used in 89.3 percent of the hospitalizations but in very small doses. When the average use rate was less than one time per day, the intervention (or lack thereof) appears to increase cost; a use rate of 0.22 is associated with an additional estimated median cost of $1,116 per hospitalization. However, when performed even one time per day (use rate 0.90), the intervention was estimated to save $2,232 per hospitalization (p
<.0001). The intervention Oral Health Restoration
was used in 83.5 percent of hospitalizations and was estimated to save money when used between 0.8 and 1.75 times per day ($1,016–$1,123). Bowel Management
was significantly associated with an estimated $784 reduction in median hospital cost. Infection Protection
was used in 73 percent of the hospitalizations and was estimated to reduce cost by more than $1,180 at a use rate of 2.6 times per day. Finally, Medication Management
was documented in only 11 percent of the hospitalizations but was estimated to save $2,027 per hospitalization with the top one-third use rate of 1.58 times per day (p
<.0001). In the lower one-third use rate, (0.13 times per 24 hours), the “lack” of Medication Management
was estimated to add an additional $2,295 to median costs (p
GEE analysis does not result in an R2
statistic, so to estimate the extent of variance in cost explained by the statistical model, a GLM procedure was used (SAS Institute, Inc. 2003
). As the GLM procedure requires that the unit of analysis be independent, repeat hospitalizations for the same patient were removed, thereby reducing the sample size to 1,075 patients. The resulting R 2
was 0.877 indicating that the model accounts for 88 percent of the variance in hospital costs for heart failure patients 60 years of age and older.