Hyponatraemia is one of the most common electrolyte disorders in the elderly and has considerable associated morbidity and mortality. In this study we report the prevalence and independent risk factors for the development of post-operative hyponatraemia after surgery for hip fracture. We conducted a retrospective cohort study of 144 consecutive patients who underwent surgery after sustaining a hip fracture. Patient medical case-notes, operative notes and online biochemistry results were used to obtain relevant data which was entered into a database. Pre-operative (30/144, 21%) and post-operative hyponatraemia (49/144, 34%) was common. However, most cases were mild (plasma sodium >130 mmol/l) and only 1% of pre-operative and 6% of post-operative patients had moderate/severe hyponatraemia (plasma sodium <130mmol/l). One of 3 post-operative deaths involved a patient with moderate hyponatraemia as a consequence of severe congestive cardiac failure. In order to determine the independent relationship between several reported risk factors and hyponatraemia we constructed a multivariable logistic regression model. Female gender, pre-operative hyponatraemia and hypotonic fluid administration were all significantly associated with the development of post-operative hyponatraemia. Age and thiazide diuretics both had positive risk associations however were not statistically significant. Hyponatraemia is a common problem in hip fracture patients. While the majority of cases in this series were mild, 6% of patients suffered from moderate/severe hyponatraemia post-operatively. Female gender, pre-operative hyponatraemia and hypotonic fluid administration are all important and independent risk factors for the development of hyponatraemia. Hypotonic intravenous fluids should be avoided unless clinically indicated in this patient group.
Prophylactic antibiotics administered prior to joint arthroplasty have become standard practice. Due to concern over the risk that 2nd generation cephalosporins posed to the elderly, as regards clostridium difficile associated infections the antimicrobial management team in our unit changed the protocol for prophylactic antibiotics. As of 1st September 2009, flucloxacillin and gentamicin were preferred over cefuroxime as the first choice of prophylactic antibiotic. However, it was noted that postoperatively patients were experiencing a decrease in renal function. One hundred patients who underwent a total hip replacement following the policy change were randomly selected from the departmental joint arthroplasty database. This group was age and sex matched to 100 patients undergoing their surgery prior to the change. Data was collected on renal function, length of stay, antibiotic and age. Any change in renal function was categorised using the RIFLE criteria. Exclusion secondary to variations from protocol or treatment for femoral neck fractures resulted in a total number of 156 patients with 78 in each arm. The average age for both groups was 64 years. Non-parametric analysis of preoperative and postoperative serum creatinine concentrations and Glomerular Filtration Rate (GFR) demonstrated a significant difference between the two groups, showing that GFR decreased (p=0.041) and serum creatinine concentration increased (p=0.037) in the cohort receiving gentamicin. Classing the impaired renal function as: risk, injury or failure (RIFLE criteria) demonstrated a statistically significant difference for any criterion positive (p=0.016) but no significant difference for the specific RIFLE groups (p=0.068). Acknowledging the small numbers and potential confounders for renal impairment, this study was able to show a difference in renal function for patients receiving gentamicin over cefuroxime as prophylaxis for joint arthroplasty.
