The effects of dehydration on rehabilitation outcomes of elderly orthopedic patients

Objective: To study the effects of dehydration, by using the indices of prerenal azotemia and orthostasis, on the rehabilitation outcomes of elderly orthopedic patients. Design: Prospective, pilot study. Setting: Regional inpatient rehabilitation center. Participants: A consecutive sample of 39 patients (29 women, 10 men), ranging in age from 58 to 94 years (mean, 78y), of whom 13 had total hip replacements, 12 had total knee replacements, and 14 had hip fractures. Interventions: Not applicable. Main Outcome Measures: Length of stay (LOS), change in the FIM(TM) instrument score, and discharge to home. Results: The mean LOS was significantly longer in the group with prerenal azotemia (n=21. 12.9+/-3.0d, t=2.49, P<.01) than in the nonazotemic group (n = 18, 9.4+/-4.6d). LOS was also significantly longer in the orthostatic group (n = 18, 13.7+/-3.4d, t=2.94, P<.01) than in the nonorthostatic group (n=21, 9.8+/-3.9d). Two-way analysis of variance showed a statistically significant effect on LOS for both azotemia (F=8.4. P=.006) and orthostasis (F=10.5, P=.003). A statistical interaction existed (F=4.7, P=.038), but it was more pronounced in the absence of both conditions. as opposed to the presence of both. LOS for the group with both azotemia and orthostasis was 13.6+/-2.7 days (n=10, F=4.7, P=.038). in contrast to 7.2+/-2.8 days in the group without either condition (n =10), Of the patients who had neither azotemia nor orthostasis. 100% (n = 10) went homed 80% (n = 8) of patients who had both conditions went home. Logistic regression analysis, however. did not show a statistically significant correlation between discharge to home and the presence of azotemia, orthostasis, or both. Conclusion: Prerenal azotemia and orthostasis are present in a significant number of elderly orthopedic patients and have a major effect on rehabilitation outcomes.