To evaluate trough serum vancomycin concentrations and identify their influencing factors in critically ill neurosurgical patients.

A retrospective study was conducted. Adult patients who received vancomycin with at least one appropriate monitoring of trough serum vancomycin concentration and admitted to neurosurgical intensive care unit (ICU) of the First Affiliated Hospital of Sun Yat-sen University from November 2017 to July 2019 were enrolled. General information including gender, age, comorbidities, etc., trough serum vancomycin concentrations, vancomycin dosage, duration of vancomycin therapy, urine output, serum creatinine (SCr), concurrent medications (including mannitol, diuretic, vasopressors, non-steroidal anti-inflammatory drugs, polymyxin, aminoglycosides and contrast medium, etc.) were collected for analysis. Trough serum vancomycin concentrations were evaluated and their influencing factors were analyzed by multiple linear regression method.

In total, 81 trough serum vancomycin concentration data sets obtained from 28 patients were evaluated. ① The initial daily dose of vancomycin was 2.00 (2.00, 2.00) g/d. After 4-6 doses, the trough serum vancomycin concentration obtained from initial blood draw was 10.99 (6.98, 16.25) mg/L, of which only 17.9% (5/28) achieving targeted concentrations (15-20 mg/L), 71.4% (20/28) subtherapeutic level and 10.7% (3/28) supratherapeutic level. ② The duration of vancomycin therapy was 8.0 (6.0, 15.0) days. With average daily dose of 2.00 (1.75, 3.00) g/d, targeted trough vancomycin concentrations were achieved in only 30.9% (25/81) of all cases, subtherapeutic concentrations in 49.4% (40/81) and supratherapeutic concentrations in 19.7% (16/81). ③ There were significant differences in age, comorbidities, vancomycin dosage, diuretics use and mannitol dosage, etc. among different vancomycin concentration groups. Multiple linear regression analysis suggested that the trough serum vancomycin concentration increased by 0.14 mg/L [95% confidence interval (95%CI) was 0.06-0.22] for every 1 year increase in age, increased by 7.22 mg/L (95%CI was 2.08-12.36) in patients with multiple comorbidities (concomitant hypertension, diabetes and coronary heart disease) compared with those without comorbidities, increased by 2.78 mg/L (95%CI was 0.20-5.35) in patients treated with diuretics compared with those without diuretics. The effect of other variables was not statistically significant. It suggested that age, multiple comorbidities (concomitant hypertension, diabetes and coronary heart disease), and diuretic usage affected trough serum vancomycin concentrations.

Targeted trough serum vancomycin level is not often achieved in neurosurgical ICU patients following standard dosing. Younger patients are associated with lower trough serum vancomycin concentrations, while diuretic usage, combined with multiple comorbidities are associated with higher trough serum vancomycin concentrations.

Vancomycin; Therapy; Trough serum concentration; Therapeutic drug monitoring