Intraoperative vasopressor use and early postoperative acute kidney injury in elderly patients undergoing elective noncardiac surgery.

BACKGROUND: Intraoperative hypotension is a risk factor for postoperative acute kidney injury (AKI). Elderly patients are susceptible due to reduced responses to acute hemodynamic changes. AIMS: Determine the association between hypotension identified from anesthetic charts and postoperative AKI in elderly patients. METHODS: Retrospective cohort study of elective noncardiac surgery patients ≥65 years, at an Australian tertiary hospital (December 2019-March 2021), with the primary outcome of AKI ≤48 h of surgery. Factors of interest were intraoperative hypotension determined from anesthetic charts (mean arterial pressure <60 mmHg, systolic blood pressure <90 mmHg, recorded 5-min) and intraoperative vasopressor use. RESULTS: In 830 patients (mean age 75 years), systolic hypotension was more frequent than mean arterial hypotension (25.7% vs. 11.9%). Most hypotensive episodes were brief (7.2% of systolic and 4.2% of mean arterial hypotension lasted >10 min) but vasopressors were used in 84.7% of cases. The incidence of postoperative AKI was 13.9%. Systolic hypotension >20 min was associated with AKI (OR, 3.88; 95% CI: 1.38-10.9), which was not significant after adjusting for vasopressors, creatinine, American Society of Anesthesiologists class, and hemoglobin drop. The cumulative dose of any specific vasopressor >20 mg (or >10 mg epinephrine) was independently associated with AKI (adjusted OR, 2.47; 95% CI: 1.34-4.58). Every 5 mg increase in the total dose of all intraoperative vasopressors used during surgery was associated with 11% increased odds of AKI (95% CI: 3-19%). CONCLUSIONS: High vasopressor use was associated with postoperative AKI in elderly patients undergoing noncardiac surgery, independent of hypotension identified from anesthetic charts.

Observational Study of the Association between Hyponatremia and Rhabdomyolysis in Patients Presenting to Hospital.

Hyponatremia may be a risk factor for rhabdomyolysis, but the association is not well defined and may be confounded by other variables. The aims of this study were to determine the prevalence and strength of the association between hyponatremia and rhabdomyolysis and to profile patients with hyponatremia. In a cross-sectional study of 870 adults admitted to hospital with rhabdomyolysis and a median peak creatine kinase of 4064 U/L (interquartile range, 1921−12,002 U/L), glucose-corrected serum sodium levels at presentation showed a U-shape relationship to log peak creatine kinase. The prevalence of mild (130−134 mmol/L), moderate (125−129 mmol/L), and severe (<125 mmol/L) hyponatremia was 9.4%, 2.5%, and 2.1%, respectively. We excluded patients with hypernatremia and used multivariable linear regression for analysis (n = 809). Using normal Na+ (135−145 mmol/L) as the reference category, we estimated that a drop in Na+ moving from one Na+ category to the next was associated with a 25% higher creatine kinase after adjusting for age, alcohol, illicit drugs, diabetes, and psychotic disorders. Multifactorial causes of rhabdomyolysis were more common than single causes. The prevalence of psychotic and alcohol use disorders was higher in the study population compared to the general population, corresponding with greater exposure to psychotropic medications and illicit drugs associated with hyponatremia and rhabdomyolysis. In conclusion, we found an association between hyponatremia and the severity of rhabdomyolysis, even after allowing for confounders.