What is new in the use of aminoglycosides in critically ill patients?

Quantification and Explanation of the Variability of First-Dose Amikacin Concentrations in Critically Ill Patients Admitted to the Emergency Department: A Population Pharmacokinetic Analysis

BACKGROUND

There may be a difference between the determinants of amikacin exposure in emergency department (ED) versus intensive care (ICU) patients, and the peak amikacin concentration varies widely between patients. Moreover, when the first dose of antimicrobials is administered to septic patients admitted to the ED, fluid resuscitation and vasopressors have just been initiated. Nevertheless, population pharmacokinetic modelling data for amikacin in ED patients are unavailable.

OBJECTIVE

The aim of this study was to quantify the interindividual variability (IIV) in the pharmacokinetics of amikacin in patients admitted to the ED and to identify the patient characteristics that explain this IIV.

METHODS

Patients presenting at the ED with severe sepsis or septic shock were randomly assigned to receive amikacin 25 mg/kg or 15 mg/kg intravenously. Blood samples were collected at 1, 6 and 24 h after the onset of the first amikacin infusion. Data were analysed using nonlinear mixed-effects modelling.

RESULTS

A two-compartment population pharmacokinetic model was developed based on 279 amikacin concentrations from 97 patients. The IIV in clearance (CL) and central distribution volume (V₁) were 71% and 26%, respectively. Body mass index (BMI), serum total protein level, serum sodium level, and fluid balance 24 h after amikacin administration explained 30% of the IIV in V₁, leaving 18% of the IIV unexplained. BMI and creatinine clearance according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation 24 h after amikacin administration explained 46% of the IIV in CL, and 39% remained unexplained.

CONCLUSION

The IIV of amikacin pharmacokinetics in ED patients is large. Higher doses may be considered in patients with low serum sodium levels, low total protein levels, or a high fluid balance.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT02365272.

Use of Gentamicin for Sepsis and Septic Shock in Anaesthesia-Intensive Care Unit: A Clinical Practice Evaluation

Objective

Numerous cases of gentamicin underdosing have been described in the literature in the context of sepsis and septic shock in anaesthesia-intensive care units (ICU). A survey of clinical practice was conducted with the aim to rationalise the use of gentamicin in the unit. The secondary objective was to propose a corrective formula for adjusting individual dosage.

Methods

A single-centre survey was used to determine the initial dose of gentamicin administered, in an anaesthesia-ICU, during the first hours of sepsis/septic shock. An initial retrospective phase allowed focusing on the points of improvement in terms of prescription. A second prospective phase enabled the evaluation of benefits following the implemented changes.

Results

Fifty-one patients were included during the retrospective phase (2014–2015) and 28 patients during the prospective phase (2016–2017). Out-of-guideline prescriptions significantly decreased between these two study periods (i.e., pulmonary infections decreased from 70.5% to 18%, p<0.001) and the mean±standard deviation administered dosage increased from 7.3±1.2 mg kg⁻¹ to 9.5±1.5 mg kg⁻¹ (p<0.001). Nevertheless, the proportion of Cmax (peak plasma concentration) ≥30 mg L⁻¹ and the mean Cmax did not change significantly. A significant association (p<0.05) was found between Cmax, body mass index, haematocrit and creatinine, enabling a corrective formula to be proposed.

Conclusion

The present study allowed improvement in gentamicin prescription in an anaesthesia-ICU. A Cmax ≥30 mg L⁻¹ remains difficult to achieve, but a Cmax ≥16 mg L⁻¹ could be considered relevant for community infections and would be more attainable. A corrective formula could be used to adjust the dosage.

Optimal and responsible use of antibiotics

PURPOSE OF REVIEW

In this review, we focus on the dual face of antibiotic therapy in the critically ill that must harmonize the need for early, appropriate and adequate antibiotic therapy in the individual-infected patient with the obligation to limit antibiotic selection pressure as much as possible to preserve its future potential.

RECENT FINDINGS

Recent articles have highlighted and detailed the various aspects, which determine antibiotic efficacy, and have identified adjunctive treatments, such as source control, which impact outcome. In addition, settings and indications where antibiotics do not improve outcome and may cause harm have been identified.

SUMMARY

Reconciling antibiotic efficacy with the limitations of their use is feasible but requires a dedicated and sustained effort throughout the whole process of clinical decision-making, from initial suspicion of sepsis to its definitive treatment.

Propensity-based study of aminoglycoside nephrotoxicity in patients with severe sepsis or septic shock

To assess the risk of acute kidney injury (AKI) attributable to aminoglycosides (AGs) in patients with severe sepsis or septic shock, we performed a retrospective cohort study in one medical intensive care unit (ICU) in France. Patients admitted for severe sepsis/septic shock between November 2008 and January 2010 were eligible. A propensity score for AG administration was built using day 1 demographic and clinical characteristics. Patients still on the ICU on day 3 were included. Patients with renal failure before day 3 or endocarditis were excluded. The time window for assessment of renal risk was day 3 to day 15, defined according to the RIFLE (risk, injury, failure, loss, and end-stage renal disease) classification. The AKI risk was assessed by means of a propensity-adjusted Cox proportional hazards regression analysis. Of 317 consecutive patients, 198 received AGs. The SAPS II (simplified acute physiology score II) score and nosocomial origin of infection favored the use of AGs, whereas a preexisting renal insufficiency and the neurological site of infection decreased the propensity for AG treatment. One hundred three patients with renal failure before day 3 were excluded. AGs were given once daily over 2.6 ± 1.1 days. AKI occurred in 16.3% of patients in a median time of 6 (interquartile range, 5 to 10) days. After adjustment to the clinical course and exposure to other nephrotoxic agents between day 1 and day 3, a propensity-adjusted Cox proportional hazards regression analysis showed no increased risk of AKI in patients receiving AGs (adjusted relative risk = 0.75 [0.32 to 1.76]). In conclusion, in critically septic patients presenting without early renal failure, aminoglycoside therapy for less than 3 days was not associated with an increased risk of AKI.