Recognition of Hyponatremia As a Risk Factor for Hip Fractures in Older Persons

Abstract

To the Editor: Hyponatremia is the most common electrolyte abnormality, especially in older persons.1 It independently increases morbidity, mortality, hospital length of stay, and costs.2 Even mild hyponatremia is associated with unsteady gait, falls, impaired concentration, and risk of fracture.3-5 In elderly ambulatory adults, hyponatremia is associated with 9.2% of all bone fractures, of which 55% are hip and femur fractures.4 Despite hyponatremia being a common clinical problem, one study found that approximately 70% of hospitalized individuals with hyponatremia were discharged without hyponatremia being recorded as a discharge diagnosis.6 This may be especially important in individuals with hip fracture, to which hyponatremia could have been a contributory factor. Failure to transmit this information to the outpatient primary care provider could conceivably leave the person at risk of subsequent falls and fractures if the hyponatremia is not recognized as a risk factor. The current study was conducted in individuals admitted for hip fracture to determine the frequency of documentation of hyponatremia in discharge summaries. This was an institutional review board–approved cross-sectional study of adults admitted with a diagnosis of hip fracture from June 2013 to October 2013 to a community-based university-affiliated hospital. All data were obtained from chart review. Data were collected on demographic characteristics, comorbid conditions, reason for fracture, serum sodium level, and outcomes including death and readmission within 1 month. Individuals were deemed to have hyponatremia if they had a serum sodium of 135 mEq/L or less upon admission or at a later point in their hospital stay. A discharge diagnosis of hyponatremia was deemed present if the International Classification of Diseases, Ninth Revision, code for hyponatremia (276.1) or mention of hyponatremia was recorded in the discharge summary. Of 133 individuals admitted in these 5 months with hip fracture, 30 had hyponatremia. Characteristics of the population are summarized in Table 1. The mean age at admission was 78 in the group without and 82 in the group with hyponatremia. Of the 30 individuals with hyponatremia, 24 (80%) did not have a documented discharge diagnosis of hyponatremia. In-hospital mortality was 10.0% in the group with hyponatremia and 1.9% in the group without, but this did not reach statistical significance. Readmission rates within 30 days of discharge were 16.7% in group with and 9.7% in the group without hyponatremia, although this did not reach statistical significance either. Individuals with chronic hyponatremia have significantly more inattention, gait imbalance, and falls, which results in substantial physical and mental distress, disability, hospital and nursing home admission,7 and death in elderly adults.8 Falls in elderly adults with hyponatremia appear to occur at equal frequency across a wide range of sodium levels, from 115 to 132 mEq/L.5 Furthermore, hyponatremia is associated with osteoporosis,3 increasing the likelihood that a fall will result in fracture. Older persons suffer disproportionately from falls and fractures, with approximately 30% falling annually.9 This leads to traumatic fractures in 4% to 6% of cases, the majority being hip fractures, with death resulting in 2% of cases.8 In addition to functional disability, hip fractures reduce life expectancy by 1.8 years. The lifetime attributable cost to hip fractures is about $81,300, and in 1997, total cost for all hip fractures exceeded $20 billion.10 The current study found that 24 of 30 (80%) of individuals with hyponatremia with hip fracture did not have hyponatremia documented in the discharge summary. Although outpatient primary care providers can readily diagnose hyponatremia by doing their own laboratory testing, failure to include hyponatremia in the discharge information may lead to an underappreciation of hyponatremia's potential role in the individual's hospital admission, perhaps leading to undertreatment of this risk factor. Electronic health records may provide an opportunity to address this problem by incorporating a clinical reminder. This would prompt the provider in the hospital to document hyponatremia in the discharge summary if it was present during the admission, along with a statement highlighting its potential relationship to the fracture. In summary, older persons are especially prone to falls and fractures, and hyponatremia may play a contributory role. This small, single-center study suggests that hyponatremia may not be optimally documented in discharge summaries and might predispose people to hospital readmission. Efforts to improve recognition and treatment of hyponatremia in the outpatient setting may help reduce falls and fractures in older persons with this risk factor. Conflict of Interest: None. Author Contributions: All authors contributed to this paper. Sponsor's Role: None.