Does selective digestive decontamination (SDD) increase antibiotic resistance? Long-term comparison of two intensive care units (with and without SDD) of the same tertiary hospital

PURPOSE

The aim of this study was to to compare the antimicrobial resistance rate and its relationship with the antibiotic consumption in two separate Intensive Care Units (ICUs) of the same hospital, one with and other without selective decontamination of the digestive tract (SDD).

METHODS

We performed a retrospective study in the two ICUs of the Araba University Hospital. Trauma and neurosurgical patients are admitted to the SDD-ICU, and general digestive surgery patients go to the no SDD-ICU. From 2014 to 2018 we analyzed the number of isolates, and the bacterial resistance trends of 47 antimicrobial-microorganism combinations. Additionally, antimicrobial consumption was estimated in both ICUs. Resistance rates were also compared with those reported in ENVIN-HELICS Spanish national registry.

RESULTS

In the ICU with SDD protocol, there was a significant decrease in the resistance of E. coli to amoxicillin/clavulanic acid and in the resistance of E. faecalis to high concentration of gentamycin and high concentration of streptomycin. A significant increase of resistance of Staphylococcus coagulasa negative (CoNS) to linezolid in the no SDD-ICU was also detected. Overall, the level of resistance in the SDD-ICU was lower or of the same order than in the ICU without SDD and that reported in the Spanish national registry.

CONCLUSIONS

SDD had neither a clinically relevant impact on emergence and spread of resistance, nor in the overall systemic antimicrobial use. The patient type rather than the SDD protocol showed to condition the ecology and therefore, the resistance rate in the ICUs.

Ceftaroline and Avibactam Removal by Continuous Renal Replacement Therapies: An in vitro Study

INTRODUCTION

Continuous renal replacement therapies (CRRTs) are frequently used in critically ill patients; however, there are scarce in vitro and in vivo studies showing the extracorporeal elimination of ceftaroline and avibactam. The aim of this study was to assess, through an in vitro model, the extracorporeal elimination of ceftaroline and avibactam by continuous veno-venous hemofiltration (CVVH), continuous veno-venous hemodiafiltration (CVVHDF), and continuous veno-venous hemodialysis (CVVHD), using a polysulfone hemofilter.

METHODS

Simulated in vitro experiments were performed using a multiFiltrate machine with a 1.4 m2 Ultraflux® AV600S polysulfone hemofilter. Isofundin® without or with bovine serum albumin was circulated as vehicle for ceftaroline or avibactam. Pre-filter, post-filter, and effluent samples were taken over a period of 60 min, and they were immediately stored at 4°C until processed in the same day. The quantification of ceftaroline and avibactam in the samples was performed by high-performance liquid chromatography with ultraviolet detection. Protein binding, extraction coefficient (EC), and extracorporeal clearance (CLCRRT) were calculated.

RESULTS

The elimination of both ceftaroline and avibactam during the three extracorporeal modalities followed first-order pharmacokinetics. Regardless of the CRRT technique, EC values for both molecules were around 1, similar to the unbound fraction of avibactam (0.96) and higher than the unbound fraction of ceftaroline (0.79). CLCRRT of ceftaroline ranged from 15.63 to 17.66 mL/min when CVVH and CVVHD were used with a flow rate of 1,000 mL/h, and from 29.25 to 32.95 mL/min for the CVVHDF modality with a flow rate of 2,000 mL/h. For avibactam, CLCRRT ranged from 15.07 to 18.82 mL/min for CVVH and CVVHD, and from 33.74 to 34.13 mL/min for CVVHDF.

DISCUSSION

Avibactam and ceftaroline are extensively removed through the polysulfone membrane, and a dose adjustment may be recommended for patients under CRRT to ensure pharmacodynamic target achievement.

Optimization of levetiracetam dosing regimen in critically ill patients with augmented renal clearance: a Monte Carlo simulation study

Background

Levetiracetam pharmacokinetics is extensively altered in critically ill patients with augmented renal clearance (ARC). Consequently, the dosage regimens commonly used in clinical practice may not be sufficient to achieve target plasma concentrations. The aim of this study is to propose alternative dosage regimens able to achieve target concentrations in this population. Furthermore, the feasibility of the proposed dosing regimens will be discussed from a clinical point of view.

Methods

Different dosage regimens for levetiracetam were evaluated in critically ill patients with ARC. Monte Carlo simulations were conducted with extended or continuous infusions and/or high drug doses using a previously developed population pharmacokinetic model. To assess the clinical feasibility of the proposed dosages, we carried out a literature search to evaluate the information on toxicity and efficacy of continuous administration or high doses, as well as the post-dilution stability of levetiracetam.

Results

According to the simulations, target concentrations in patients with CrCl of 160 or 200 mL/min can be achieved with the 3000 mg daily dose by prolonging the infusion time of levetiracetam. For patients with CrCl of 240 mL/min, it would be necessary to administer doses higher than the maximum recommended. Available evidence suggests that levetiracetam administration in continuous infusion or at higher doses than those approved seems to be safe. It would be desirable to re-examinate the current recommendations about drug stability and to achieve a consensus in this issue.

Conclusions

Conventional dosage regimens of levetiracetam (500–1500 mg twice daily in a short infusion) do not allow obtaining drug plasma concentrations among the defined target in critically ill patients with ARC. Therefore, new dosing guidelines with specific recommendations for patients in this subpopulation are needed. This study proposes new dosages for levetiracetam, including extended (4 or 6 h) infusions, continuous infusions or the administration of doses higher than the recommended in the summary of product characteristics (> 3000 mg). These new dosage recommendations take into account biopharmaceutical and pharmacokinetic aspects and meet feasibility criteria, which allow them to be transferred to the clinical environment with safety and efficacy. Nevertheless, further clinical studies are needed to confirm these results.

Population Pharmacokinetics of Levetiracetam and Dosing Evaluation in Critically Ill Patients with Normal or Augmented Renal Function

Levetiracetam is a broad-spectrum antiepileptic drug commonly used in intensive care units (ICUs). The objective of this study is to evaluate the adequacy of levetiracetam dosing in patients with normal or augmented renal clearance (ARC) admitted to the ICU by population modelling and simulation. A multicentre prospective study including twenty-seven critically ill patients with urinary creatinine clearance (CrCl) > 50 mL/min and treated with levetiracetam was developed. Levetiracetam plasma concentrations were best described by a two-compartment model. The parameter estimates and relative standard errors (%) were clearance (CL) 3.5 L/h (9%), central volume of distribution (V1) 20.7 L (18%), intercompartmental clearance 31.9 L/h (22%), and peripheral volume of distribution 33.5 L (13%). Interindividual variability estimates were, for the CL, 32.7% (21%) and, for V1, 56.1% (29%). The CrCl showed significant influence over CL. Simulations showed that the administration of at least 500 mg every 8 h or 1000 mg every 12 h are needed in patients with normal renal function. Higher doses (1500 or 2000 mg, every 8 h) are needed in patients with ARC. Critically ill patients with normal or ARC treated with levetiracetam could be at high risk of being underdosed.

Quantification of Ceftaroline in Human Plasma Using High-Performance Liquid Chromatography with Ultraviolet Detection: Application to Pharmacokinetic Studies

This study was conducted to develop a rapid, simple and reproducible method for the quantification of ceftaroline in plasma samples by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Sample processing consisted of methanol precipitation and then, after centrifugation, the supernatant was injected into the HPLC system, working in isocratic mode. Ceftaroline was detected at 238 nm at a short acquisition time (less than 5 min). The calibration curve was linear over the concentration range from 0.25 to 40 µg/mL, and the method appeared to be selective, precise and accurate. Ceftaroline in plasma samples was stable at -80 °C for at least 3 months. The method was successfully applied to characterize the pharmacokinetic profile of ceftaroline in two critically ill patients and to evaluate whether the pharmacokinetic/pharmacodynamic (PK/PD) target was reached or not with the dose regimen administered.

SARS-CoV-2 in Spanish Intensive Care Units: Early experience with 15-day survival in Vitoria

Purpose

Community transmission of SARS-CoV-2 was detected in Spain in February 2020, with 216% intensive care unit (ICU) capacity expanded in Vitoria by March 18^th, 2020.

Methods

We identified patients from the two public hospitals in Vitoria who were admitted to ICU with confirmed infection by SARS-CoV-2. Data reported here were available in April 6th, 2020. Mortality was assessed in those who completed 15-days of ICU stay.

Results

We identified 48 patients (27 males) with confirmed SARS-CoV-2. Median [interquartile range (IQR)] age of patients was 63 [51–75] years. Symptoms began a median of 7 [5–12] days before ICU admission. The most common comorbidities identified were obesity (48%), arterial hypertension (44%) and chronic lung disease (37%). All patients were admitted by hypoxemic respiratory failure and none received non-invasive mechanical ventilation. Forty-five (94%) underwent intubation, 3 (6%) high flow nasal therapy (HFNT), 1 (2%) extracorporeal membrane oxygenation (ECMO) and 22 (46%) required prone position. After 15 days, 14/45 (31%) intubated patients died (13% within one week), 10/45 (22%) were extubated, and 21/45 (47%) underwent mechanical ventilation. Six patients had documented super-infection. Procalcitonin plasma above 0.5 μg/L was associated with 16% vs. 19% (p = 0.78) risk of death after 7 days.

Conclusion

This early experience with SARS-CoV-2 in Spain suggests that a strategy of right oxygenation avoiding non-invasive mechanical ventilation was life-saving. Seven-day mortality in SARS-CoV-2 requiring intubation was lower than 15%, with 80% of patients still requiring mechanical ventilation. After 15 days of ICU admission, half of patients remained intubated, whereas one third died.

Impact of augmented renal clearance on the pharmacokinetics of linezolid: Advantages of continuous infusion from a pharmacokinetic/pharmacodynamic perspective

OBJECTIVES

The aim of this study was to assess the influence of renal function, in particular the presence of augmented renal clearance (ARC), on the pharmacokinetics of linezolid in critically ill patients. The effect of continuous infusion on the probability of therapeutic success from a pharmacokinetic/pharmacodynamic (PK/PD) perspective was also evaluated.

METHODS

Seventeen patients received linezolid (600 mg every 12 h) as a 30-min infusion and 26 as a continuous infusion (50 mg/h). The PK parameters were calculated and the probability of PK/PD target attainment (PTA) was estimated by Monte Carlo simulation (MCS) for different doses administered by intermittent (600 mg every 12 h or 600 mg every 8 h) or continuous infusion (50 mg/h or 75 mg/h).

RESULTS

In patients without ARC, the standard dose was adequate to attain the PK/PD target. However, linezolid clearance was significantly higher in ARC patients, leading to sub-therapeutic concentrations. Continuous infusion (50 mg/h) provided concentrations ≥2 mg/l in 70% of the ARC patients. MCS revealed that concentrations ≥2 mg/l would be reached in >90% of patients receiving 75 mg/h.

CONCLUSIONS

ARC increases linezolid clearance and leads to a high risk of underexposure with the standard dose. Continuous infusion increases the PTA, but an infusion rate of 75 mg/h should be considered to ensure concentrations ≥2 mg/ml.

Novel Population Pharmacokinetic Model for Linezolid in Critically Ill Patients and Evaluation of the Adequacy of the Current Dosing Recommendation

Antimicrobial treatment in critically ill patients remains challenging. The aim of this study was to develop a population pharmacokinetic model for linezolid in critically ill patients and to evaluate the adequacy of current dosing recommendation (600 mg/12 h). Forty inpatients were included, 23 of whom were subjected to continuous renal replacement therapies (CRRT). Blood and effluent samples were drawn after linezolid administration at defined time points, and linezolid levels were measured. A population pharmacokinetic model was developed, using NONMEM 7.3. The percentage of patients that achieved the pharmacokinetic/pharmacodynamic (PK/PD) targets was calculated (AUC₂₄/MIC > 80 and 100% T_>MIC). A two-compartment model best described the pharmacokinetics of linezolid. Elimination was conditioned by the creatinine clearance and by the extra-corporeal clearance if the patient was subjected to CRRT. For most patients, the standard dose of linezolid did not cover infections caused by pathogens with MIC ≥ 2 mg/L. Continuous infusion may be an alternative, especially when renal function is preserved.

Antibiotic susceptibility trend before and after long-term use of selective digestive decontamination: a 16 year ecological study

Objectives

The aim of this study was to compare antimicrobial susceptibility rates in a Spanish ICU before and after the introduction of selective digestive decontamination (SDD) and also to compare these with susceptibility data from other Spanish ICUs without SDD.

Methods

We performed a retrospective study in the ICU of the University Hospital of Alava, where SDD was implemented in 2002. The SDD protocol consisted of a 2% mixture of gentamicin, colistin and amphotericin B applied on the buccal mucosa and a suspension of the same drugs in the gastrointestinal tract; additionally, for the first 3 days, systemic ceftriaxone was administered. From 1998 to 2013 we analysed the susceptibility rates for 48 antimicrobial/organism combinations. Interrupted time series using a linear dynamic model with SDD as an intervention was used. Data from other ICUs were obtained from the ENVIN-HELICS national registry.

Results

Only amoxicillin/clavulanic acid against Escherichia coli and Proteus mirabilis, and a high concentration of gentamicin against Enterococcus faecalis, resulted in a significant decrease in the susceptibility rate after the implementation of SDD, with a drop of 20%, 27% and 32%, respectively. Compared with other Spanish ICUs without SDD, the susceptibility rate was higher in the ICU of our hospital in most cases. When it was lower, differences were <10%, except for a high concentration of streptomycin against Enterococcus faecium, for which the difference was 19%.

Conclusions

No relevant changes in the overall susceptibility rate after the implementation of SDD were detected. Susceptibility rates were not lower than those in the Spanish ICUs without SDD.

Pharmacokinetics of linezolid in critically ill patients on continuous renal replacement therapy: Influence of residual renal function on PK/PD target attainment

PURPOSE

To assess the pharmacokinetics of linezolid in septic patients undergoing continuous renal replacement therapy (CRRT) and investigate whether residual renal function affects the probability of attaining the pharmacokinetic/pharmacodynamic (PK/PD) target.

MATERIAL AND METHODS

Prospective study conducted in three Spanish hospitals. Linezolid concentrations were measured in plasma and effluent samples and pharmacokinetic parameters were calculated. The probability of target attainment (PTA) and the cumulative fraction of response (CFR) were calculated considering AUC₂₄/MIC>80 and %T_>MIC > 85% as the PK/PD indexes related to efficacy.

RESULTS

In anuric patients (CrCl<10 mL/min), the contribution of extracorporeal Cl to total Cl was higher (47% vs 16%) than in patients with residual renal function (CrCl≥10 mL/min). For an MIC of 2 mg/L, AUC₂₄/MIC>80 was achieved in >85% of the anuric patients, but in <15% of the patients with residual renal function.

CONCLUSIONS

The standard dose (600 mg q12h) ensures a moderately high probability of treatment success in anuric patients when the infection is due to microorganisms with MIC≤2 mg/L; although higher doses increase the probability of treatment success, the safety is compromised. In patients with residual renal function, the standard dose is insufficient, but 900 mg q8h provide higher probability of treatment success without compromising the safety.

Population pharmacokinetics of daptomycin in critically ill patients

Daptomycin has shown activity against a wide range of Gram-positive bacteria; however, the approved dosages usually seem insufficient for critically ill patients. The aim of this study was to develop a population pharmacokinetic model for daptomycin in critically ill patients and to estimate the success of the therapy by applying pharmacokinetic/pharmacodynamic (PK/PD) criteria. Sixteen intensive care unit patients were included, four of whom underwent continuous renal replacement therapies (CRRT). Blood and, when necessary, effluent samples were drawn after daptomycin administration at previously defined time points. A population approach using NONMEM 7.3 was performed to analyse data. Monte Carlo simulations were executed to evaluate the suitability of different dosage regimens. The probabilities of achieving the PK/PD target value associated with treatment success (ratio of the area under the plasma concentration-time curve over 24 h divided by the minimum inhibitory concentration (AUC₂₄/MIC ≥ 666)) and to reach daptomycin concentrations linked to toxicity (minimum concentration at steady-state (Cmin_ss) ≥ 24.3 mg/L) were calculated. The pharmacokinetics of daptomycin was best described by a one-compartment model. Elimination was conditioned by the creatinine clearance (Clcr) and also by the extra-corporeal clearance when patients were subjected to continuous renal replacement therapy (CRRT). The PK/PD analysis confirmed that 280- and 420-mg/d dosages would not be enough to achieve high probabilities of target attainment for MIC values ≥ 1 mg/L in patients with Clcr ≥ 60 mL/min or in subjects with lower Clcrs but receiving CRRT. In these patients, higher dosages (560-840 mg/d) should be needed. When treating infections due to MIC values ≥ 4 mg/L, even the highest dose would be insufficient.