Signs of Dehydration after Hip Fracture Surgery: An Observational Descriptive Study

Abstract

Background and Objectives: Dehydration might be an issue after hip fracture surgery, but the optimal tools to identify the dehydrated condition have not been determined. The aim of the present study was to compare the characteristics of elderly postoperative patients who were classified as dehydrated according to the methods used in the clinic. Materials and Methods: Thirty-eight patients aged between 65 and 97 (mean, 82) years were studied after being admitted to a geriatric department for rehabilitation after hip fracture surgery. Each patient underwent blood analyses, urine sampling, and clinical examinations. Results: Patients ingested a mean of 1,008 mL (standard deviation, 309 mL) of fluid during their first day at the clinic. Serum osmolality increased significantly with the plasma concentrations of sodium, creatinine, and urea. Seven patients had high serum osmolality (≥300 mosmol/kg) that correlated with the presence of tongue furrows (p < 0.04), poor skin turgor (p < 0.03), and pronounced albuminuria (p < 0.03). Eight patients had concentrated urine (urine-specific gravity ≥ 1.025) that correlated with a low intake of liquid and with a decrease in body weight during the past month of -3.0 kg (25-75 th percentiles, -5.1 to -0.9) versus +0.2 (-1.9 to +2.7) kg (p < 0.04). Conclusions: Renal fluid conservation of water, either in the form of hyperosmolality or concentrated urine, was found in 40% of the patients after hip fracture surgery. Hyperosmolality might not indicate a more severe fluid deficit than is indicated by concentrated urine but suggests an impaired ability to concentrate the urine.

Keywords: dehydration; frail elderly patient; urine color; urine osmolality.

Figure 1

Biomarker of inflammation vs. time after surgery (A) and intake of food (B). Data could be logarithm-transformed or square root-transformed, as indicated on the appropriate axis, before being tested for correlation by linear regression analysis.

Figure 2

Serum osmolality vs. biomarkers of kidney function. (A) plasma sodium, (B) creatinine, and (C) creatinine vs. urea).

Figure 3

(A) Lower urine-specific gravity for higher fluid intake; (B) Correlation between urine osmolality and urinary creatinine.

Figure 4

The change in body weight during the past 6 weeks (mean, 38 d) vs. (A) the intake of fluid on the day of admission on a linear scale (B) whether fluid intake was higher or lower than 800 mL on the day of admission (C) whether the urine was normal or concentrated (urine-specific gravity ≥1.025), and (D) whether none, one of both of these two variables was present in the patient.