Vancomycin Dosing and Pharmacokinetics in Postoperative Pediatric Cardiothoracic Surgery Patients

Comparison of Amikacin Pharmacokinetics in Neonates With and Without Congenital Heart Disease

OBJECTIVES

The primary objective was to compare the volume of distribution (Vd), clearance (CL), elimination rate (K_e), and half-life (t½) of amikacin in neonates with cyanotic defects, acyanotic defects, and controls, adjusted for gestational and postnatal age. Secondary objectives were to compare the incidence of acute kidney injury (AKI) between controls and the congenital heart disease (CHD) group and to identify potential risk factors.

METHODS

This retrospective cohort study included neonates receiving amikacin from January 1, 2013 to August 31, 2016. Patients were excluded if concentrations were not appropriately obtained or if AKI or renal anomalies were identified prior to amikacin initiation. Congenital heart disease was classified as acyanotic or cyanotic. Patients with CHD were matched 1:1 with non-CHD controls according to postmenstrual age. Bivariate analyses were performed using Wilcoxon-Mann-Whitney test, Pearson χ² tests, or Fisher exact as appropriate with a p value <0.05. Regression analyses included logistic and analysis of covariance.

RESULTS

Fifty-four patients with CHD were matched with 54 controls. Median (IQR) postnatal age (days) at amikacin initiation significantly differed between CHD and controls, 3.0 (1.0-16.0) versus 1.0 (1.0-3.0), p = 0.016. After adjusting for gestational and postnatal age, there was no difference in the mean (95% CI) Vd (L/kg) and CL (L/kg/hr) between CHD and controls, 0.47 (0.44-0.50) versus 0.46 (0.43-0.49), p = 0.548 and 0.05 (0.05-0.05) versus 0.05 (0.05-0.05), p = 0.481, respectively. There was no difference in K_e or t½ between groups. There was no difference in AKI between the CHD and controls, 18.5% versus 9.3%, p = 0.16.

CONCLUSIONS

Clinicians should consider using standard amikacin dosing for neonates with CHD and monitor renal function, since they may have greater AKI risk factors.

Evaluation of vancomycin initial trough levels in children: A 1-year retrospective study

Background and objectives

Achieving vancomycin therapeutic levels is essential for antibacterial success and resistance prevention. Multiple studies have shown that most of the children fail to reach therapeutic trough levels (10-20 µg/mL). This study aims to determine the frequency of achieving therapeutic vancomycin initial trough levels in children, evaluate the effect of age on that achievement and the mean initial trough levels, and the frequency of supratherapeutic levels.

Methods

Children aged 1 month to 12 years who received three or more vancomycin doses 15 mg/kg every 6 h while admitted at our hospital from February 2016 to January 2017, and had a level before the fourth dose were included. Cases with high baseline serum creatinine, acute kidney injury, and congenital heart disease were excluded.

Results

Out of 75 included cases, one third, 28/75 (37.3%), achieved goal. The lowest frequency was 6/28 (21.4%) of the 2-5 years group, which were statistically less likely to achieve, and had significantly lower mean initial trough than the 1-23 months group (P = 0.026 and 0.013, respectively). Mean initial trough levels were 10.1, 7.3, and 8.2 µg/mL in the 1-23 months, 2-5 years, and 6-12 years groups, respectively (P = 0.014). No supratherapeutic levels were observed.

Conclusion

Vancomycin dose of 60 mg/kg/day is insufficient to attain target levels for most of the children. Children aged 2-5 years are the least likely to achieve and have the lowest mean levels. More intensified doses are warranted to be studied prospectively to identify the most effective empiric dose for children.

Optimizing Vancomycin Use Through 2-Point AUC-Based Therapeutic Drug Monitoring in Pediatric Patients

The 24-hour vancomycin area under the serum concentration-time curve (AUC₂₄ ) divided by the minimum inhibitory concentration (MIC) (AUC₂₄ /MIC) is more closely related to patient outcomes than serum trough concentrations (C_trough ). Two-point simplified equations for calculating AUC based on serum peak concentrations (C_peak ) and C_trough , named equation A (EqA) and equation B (EqB), have recently been adopted into clinical use for adult pediatric patients. We aimed to find the agreement between predicted AUC₂₄ using the reference method (ref) relative to EqA and EqB and the correlation between C_trough and AUC₂₄ . From June to December 2018, 43 pediatric patients with normal renal function, receiving 15 mg/kg of vancomycin intravenously every 6 hours, were enrolled. The pediatric patients' median age was 2.2 years (range 0.1-15.3). At steady state, vancomycin C_peak and C_trough were measured at 2 hours after infusion completion and within 30 minutes before the next dosing, respectively. AUC₂₄ was estimated using ref, EqA, and EqB. From Bland-Altman analysis, the 2 AUC₂₄ s estimated by ref and EqA showed less bias than those estimated by ref and EqB (bias 1.3 and -72.1 mg⋅h/L, respectively). C_trough and AUC₂₄ using either ref or EqA were correlated more closely (r² = 0.94) than with EqB (r² = 0.86). Assuming a vancomycin MIC of 1 mg/L, an AUC₂₄ ≥400 mg⋅h/L was targeted. Regardless of the method used, AUC₂₄ ≥400 mg⋅h/L was never seen with C_trough <8 mg/L but was always seen with C_trough >10 mg/L. In conclusion, EqA based on the 2 measured serum concentrations was sufficiently accurate for AUC₂₄ estimation. C_trough >10 mg/L correlated highly to AUC₂₄ ≥400 mg⋅h/L.

Population Pharmacokinetics of Vancomycin in the Pediatric Cardiac Surgical Population

OBJECTIVE

Vancomycin is often used in the pediatric cardiac surgical population, but few pharmacokinetic data are available to guide dosing.

METHODS

A retrospective, population pharmacokinetic study was performed for patients <19 years of age initiated on vancomycin after cardiac surgery in the cardiac intensive care unit from 2011-2016 in our institution. Patient data were summarized by using descriptive statistical methods, and population pharmacokinetic analysis was performed by using NONMEM. Simulation was performed to determine a dosing strategy that most frequently obtained an AUC_0-24:MIC (minimum inhibitory concentration) ratio of >400.

RESULTS

A total of 261 patients (281 cardiac surgical procedures, cardiopulmonary bypass 82.3%) met inclusion criteria (60.1% male, median age 0.31 [IQR, 0.07-0.77] years). Vancomycin (14.5 ± 1.7 mg/kg/dose) was administered at median postoperative day 9 (IQR, 4-14), with a mean serum concentration of 11.5 ± 5.5 mg/L at 8.9 ± 3.8 hours after a dose. Population pharmacokinetic analysis demonstrated that a 1-compartment proportional error model with allometrically scaled weight best fit the data, with creatinine clearance and postmenstrual age as significant covariates. Simulation identified that a dosing regimen of 20 mg/kg/dose every 8 hours was most likely to achieve an AUC_0-24:MIC ratio > 400 at a mean trough serum concentration of 12.9 ± 3.2 mg/L.

CONCLUSIONS

Vancomycin dosing in the postoperative pediatric cardiac surgical population should incorporate postmenstrual age and creatinine clearance. A vancomycin dose of 20 mg/kg every 8 hours is a reasonable empiric strategy.

Vancomycin associated acute kidney injury in pediatric patients

INTRODUCTION

Vancomycin associated acute kidney injury (vAKI) is a well known complication in pediatric patients. Identification and characterization of the incidence and risk factors for vAKI in the pediatric population would assist clinicians in potentially preventing or mitigating vAKI.

METHODS AND MATERIALS

A 6 year retrospective cohort study was designed. Patients were included if they were < 19 years of age, received vancomycin as inpatients, and had a baseline SCr and one other SCr drawn during and up to 72 hours after the discontinuation of vancomycin. Data collection included patient demographics, vancomycin doses and length of therapy, vancomycin serum concentrations, and concomitant medications. The Kidney Disease Improving Global Outcomes (KDIGO) criteria were used to characterize acute kidney injury. Descriptive statistical methods were used and ordinal logistic regression was employed to determine variables significantly associated with vAKI.

RESULTS

A total of 7,095 patients met study criteria (55.4% male, median age 4.1 years (IQR 0.67-11.2 years)). Mechanical ventilation was used in 7.9% (n = 563) and mortality was 4.9% (n = 344). A total of 153 concomitant medications were identified. A median of 5 (IQR 3-7) SCr values were obtained and median SCr prior to vancomycin was 0.39 (IQR 0.28-0.57) mg/dL (CrCl 134±58 mL/min/1.73m2). Vancomycin was administered for a median of 2 (IQR 1-3) days (14.9±1.6 mg/kg/dose). vAKI was present in 12.2% (n = 862: KDIGO stage 1 (8.30%, n = 589), KDIGO stage 2 (1.94%, n = 138) KDIGO stage 3 (1.89%, n = 134)). Mean vancomycin serum concentration at 6-8 hours after a dose for patients with vAKI (10.7±8.9 mg/L) was significantly, but not clinically different for patients with no vAKI (7.5±6.3 mg/L). (p<0.05) Ordinal logistic regression identified total dose of vancomycin, vancomycin administration in the intensive care unit, and concomitant medication administration as significant for vAKI. In particular, concomitant administration of several different medications, including nafcillin, clindamycin, and acetazolamide, were noted for strong associations with vAKI. (p<0.05).

CONCLUSIONS

Moderate to severe acute kidney injury due to vancomycin is infrequent in children and associated with concomitant medication use and total dose of vancomycin. Serum vancomycin concentrations are not useful predictors of vAKI in the pediatric population.

The Relationship Between Vancomycin Trough Concentrations and AUC/MIC Ratios in Pediatric Patients: A Qualitative Systematic Review

BACKGROUND

In adults, the area under the concentration-time curve (AUC) divided by the minimum inhibitory concentration (MIC) is associated with better clinical and bacteriological response to vancomycin in patients with methicillin-resistant Staphylococcus aureus who achieve target AUC/MIC ≥ 400. This target is often extrapolated to pediatric patients despite the lack of similar evidence. The impracticalities of calculating the AUC in practice means vancomycin trough concentrations are used to predict the AUC/MIC.

OBJECTIVE

This review aimed to determine the relationship between vancomycin trough concentrations and AUC/MIC in pediatric patients.

METHODS

We searched the MEDLINE and Embase databases, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials using the medical subject heading (MeSH) terms vancomycin and AUC and pediatric* or paediatric*. Articles were included if they were published in English and reported a relationship between vancomycin trough concentrations and AUC/MIC.

RESULTS

Of 122 articles retrieved, 11 met the inclusion criteria. One trial reported a relationship between vancomycin trough concentrations, AUC/MIC, and clinical outcomes but was likely underpowered. Five studies found troughs 6-10 mg/l were sufficient to attain an AUC/MIC > 400 in most general hospitalized pediatric patients. One study in patients undergoing cardiothoracic surgery found a trough of 18.4 mg/l achieved an AUC/MIC > 400. Two oncology studies reported troughs ≥ 15 mg/l likely attained an AUC/MIC ≥ 400. In critical care patients: one study found a trough of 9 mg/l did not attain the AUC/MIC target; another found 7 mg/l corresponded to an AUC/MIC of 400.

CONCLUSIONS

Potential vancomycin targets varied based on the population studied but, for general hospitalized pediatric patients, troughs of 6-10 mg/l are likely sufficient to achieve AUC/MIC ≥ 400. For MIC ≥ 2 mg/l, higher troughs are likely necessary to achieve an AUC/MIC ≥ 400. More research is needed to determine the relationships between vancomycin trough concentrations, AUC/MIC, and clinical outcomes.