Clinical significance of hyponatremia in hip fracture in elderly patients

Abstract

Objective: To investigate the outcome of hip fracture patients associated with hyponatremia. Methods: From January 2012 to December 2016, the data of 1 001 elderly patients with hip fracture treated in the Seventh Medical Center of PLA General Hospital were analyzed retrospectively. According to the level of serum sodium, the patients were divided into hyponatremia group (sodium<135 mmol/L) and non-hyponatremia group (sodium≥135 mmol/L), in which≥130-135 mmol/L was mild hyponatremia, ≥125-130 mmol/L was moderate hyponatremia, and<125 mmol/L was severe hyponatremia. The length of hospital stay, incidence of complications and mortality were compared between patient with hyponatremia and without; and the above three indexes between patients with mild hyponatremia and moderate severe hyponatremia were also analyzed. Results: There were 126 patients with hyponatremia, including 98 with mild hyponatremia (9.8%, 98/1 001), 18 with moderate hyponatremia (1.8%, 18/1 001), and 10 with severe hyponatremia (1.0%, 10/1001); of those patients, there were 53 males and 73 females, aged 82(78, 87) years. There were 875 patients in non-hyponatremia group, including 274 males and 601 females, and aged 81(75, 85) years. The mortality of 30 days, 1 year and overall were 9.5% (12/126), 26.2% (33/126) and 40.5% (51/126) in hyponatremia group, 3.5% (31/875), 14.2% (124/875) and 27.7% (242/875) in non-hyponatremia group, respectively; the differences between the two groups were all statistically significant (χ2=9.583, 12.031, 9.839, all P<0.05). After adjusting the age, sex, fracture type and coexisting diseases, hyponatremia was an independent risk factor for 30 days, 1 year and overall mortality, the OR(95%CI) was 2.744(1.331-5.654), 1.975(1.251-3.119), 1.637(1.099-2.440), respectively (all P<0.05). The 30 days, 1 year and overall mortality for mild hyponatremia were 6.1%, 24.5% and 37.8%, respectively; and those were 21.4%, 32.1% and 50.0% in patients with moderate and severe hyponatremia, respectively; only the difference for 30 days mortality was statistically different between two groups (χ²=4.278, P=0.039). The length of hospital stay for mild hyponatremia patients were 11 (9,16) d, and it was 12(10,18) d in patients with moderate and severe hyponatremia patients, and there was no significant difference between the two groups (Z=1.613, P=0.107). The incidence of complications was 22.9% (200/875) in non-hyponatremia group and 32.5%(41/126) in hyponatremia group, and there was significant difference between the two groups (χ²=5.649, P=0.017). Conclusions: Compared with non-hyponatremia, patients with hyponatremia have higher incidence of perioperative complications, longer hospital stay and higher mortality. With the increasing degree of hyponatremia, the above indicators tend to be serious.