Higher renal replacement therapy dose delivery influences on drug therapy

Prescribing Continuous Kidney Replacement Therapy in Acute Kidney Injury: A Narrative Review

Severe acute kidney injury is a common complication in critically ill patients, often necessitating support with a modality of kidney replacement therapy. Continuous kidney replacement therapies (CKRTs) have become a mainstay in the management of patients with acute kidney injury in the intensive care unit. Understanding the fundamentals of CKRT is necessary to safely and effectively prescribe treatment. In this narrative review, we summarize critical aspects of CKRT management, including selection of the mode of therapy; choice of hemofilter/hemodialyzer used; determination of the blood flow rate, composition and flow rates of dialysate and/or replacement fluids, and the ultrafiltration rate; and use and methods of anticoagulation. Requirements for vascular access and appropriate monitoring and dose adjustment of medications and a plan for monitoring the delivery of therapy and ensuring appropriate nutritional management are also discussed.

Factors relating to mortality in septic patients in Vietnamese intensive care units from a subgroup analysis of MOSAICS II study

Sepsis is the most common cause of in-hospital deaths, especially from low-income and lower-middle-income countries (LMICs). This study aimed to investigate the mortality rate and associated factors from sepsis in intensive care units (ICUs) in an LMIC. We did a multicenter cross-sectional study of septic patients presenting to 15 adult ICUs throughout Vietnam on the 4 days representing the different seasons of 2019. Of 252 patients, 40.1% died in hospital and 33.3% died in ICU. ICUs with accredited training programs (odds ratio, OR: 0.309; 95% confidence interval, CI 0.122-0.783) and completion of the 3-h sepsis bundle (OR: 0.294; 95% CI 0.083-1.048) were associated with decreased hospital mortality. ICUs with intensivist-to-patient ratio of 1:6 to 8 (OR: 4.533; 95% CI 1.621-12.677), mechanical ventilation (OR: 3.890; 95% CI 1.445-10.474) and renal replacement therapy (OR: 2.816; 95% CI 1.318-6.016) were associated with increased ICU mortality, in contrast to non-surgical source control (OR: 0.292; 95% CI 0.126-0.678) which was associated with decreased ICU mortality. Improvements are needed in the management of sepsis in Vietnam such as increasing resources in critical care settings, making accredited training programs more available, improving compliance with sepsis bundles of care, and treating underlying illness and shock optimally in septic patients.

Population Pharmacokinetic Modeling and Simulations of Imipenem in Burn Patients With and Without Continuous Venovenous Hemofiltration in the Military Health System

Continuous venovenous hemofiltration (CVVH) is a life‐sustaining procedure in patients with severe burns and acute kidney injury. Physiologic changes from burn injury and use of CVVH may alter imipenem pharmacokinetics (PK). We aimed to compare imipenem clearance (CL) in burn patients with and without CVVH, determine the effect of burn on imipenem volume of distribution (CVVH, n = 12; no CVVH, n = 11), in combination with previously published models. Model qualification was performed with standard diagnostics and comparing predicted PK parameters/time‐concentration profiles with those in the existing literature. Monte Carlo simulations were conducted to evaluate the probability of target attainment. A 2‐compartment model best described the data. Utilizing albumin as a covariate on volume parameters and leveraging the clearance model from prior literature, our model predicted imipenem central volume and CL within a 10% margin of error across healthy, renally impaired, and burn populations. We provide direct comparison of imipenem CL in burn patients with and without CVVH. Notably, there was no significant difference. Large imipenem V_d in patients with severe burns is likely explained by increased capillary permeability, for which serum albumin may be a reasonable surrogate. Dosing 500 mg every 6 hours is adequate for burn patients on renally dosed CVVH; however, suspicion of augmented renal clearance or patients placed on CVVH without renal impairment may necessitate dosing of 1000 mg every 6 hours.

Renal replacement therapy in critically ill patients with acute kidney injury: 2020 nephrologist's perspective

Renal replacement therapies (RRT) as support for acute kidney injury in critically ill patients have become a routine and essential practice in their management, resulting in the widespread use of various techniques among these patients, such as intermittent hemodialysis (IHD), extended hemodialysis and continuous RRT (CRRT). In this review we aim to summarize current evidence of indication, choice of modality, timing of initiation, dosing and technical aspects of RRT. We carried out a narrative review based on guidelines, consensus documents by main working groups and the latest relevant clinical trials on RRT in the critically ill. We did not find enough evidence of any RRT modality having superior benefits in terms of patient survival, length of intensive care unit/hospital stay or renal outcomes among critically ill patients, in spite of optimization of clinical indication, modality, timing of initiation and intensity of initial therapy. This is still a controverted matter, since only early start of high-flux CRRT has been proven beneficial over IHD among hemodynamically unstable postoperative patients. Our objective is to portrait current RRT practices in multidisciplinary management of critically ill patients by intensive care and nephrology professionals. Implication of a nephrologist in the assessment of hemodynamic status, coexisting medical conditions, renal outcome expectations and management of resources could potentially have benefits at the time of RRT selection and troubleshooting.

Intensity of Renal Replacement Therapy and Duration of Mechanical Ventilation: Secondary Analysis of the Acute Renal Failure Trial Network Study

BACKGROUND

Randomized clinical trials have failed to show benefit from increasing intensity of renal replacement therapy (RRT) for acute kidney injury, but continue to be frequently used. In addition, intensive RRT is associated with an increase in adverse events potentially secondary to small solute losses, such as phosphate. We hypothesized that, compared with less-intensive RRT, intensive RRT would lead to longer duration of mechanical ventilation.

RESEARCH QUESTION

Does more-intensive renal replacement therapy in critically ill patients with acute kidney injury increase time to extubation from mechanical ventilation when compared with less-intensive therapy?

STUDY DESIGN AND METHODS

The Acute Renal Failure Trial Network study was a randomized multicenter trial of more-intensive (hemodialysis or sustained low-efficiency dialysis six times per week or continuous venovenous hemodiafiltration at 35 mL/kg per hour) vs less-intensive (hemodialysis or sustained low-efficiency dialysis three times per week or continuous venovenous hemodiafiltration at 20 mL/kg per hour) RRT in critically ill patients with acute kidney injury. Of 1124 patients, 907 who were supported by mechanical ventilation on study initiation were included in this Cox-proportional hazards analysis. The primary outcome was the time to first successful extubation off mechanical ventilation.

RESULTS

Patients who were assigned randomly to more-intensive RRT had a 33.3% lower hazard rate of successful extubation (hazard ratio, 0.67; 95% CI, 0.52-0.88; P < .001) when compared with patients who were assigned to less-intensive RRT. Patients who were assigned to more-intensive RRT had, on average, 2.07 ventilator-free days, compared with 3.08 days in those who were assigned to less-intensive RRT (P < .001) over 14 days from start of the study.

INTERPRETATION

Critically ill mechanically ventilated patients who were assigned randomly to more-intensive RRT had longer duration of mechanical ventilation compared with those who were assigned to less-intensive RRT. The reasons for this, such as excessive phosphate loss from more-intensive RRT, deserve further study to optimize the safety and effectiveness of CRRT delivery. This was a post hoc analysis of the Acute Renal Failure Trial Network study; clinical trial registration of the original trial is NCT00076219.

A Guide to Understanding Antimicrobial Drug Dosing in Critically Ill Patients on Renal Replacement Therapy

A careful management of antimicrobials is essential in the critically ill with acute kidney injury, especially if renal replacement therapy is required. Acute kidney injury may lead per se to clinically significant modifications of drugs' pharmacokinetic parameters, and the need for renal replacement therapy represents a further variable that should be considered to avoid inappropriate antimicrobial therapy. The most important pharmacokinetic parameters, useful to determine the significance of extracorporeal removal of a given drug, are molecular weight, protein binding, and distribution volume. In many cases, the extracorporeal removal of antimicrobials can be relevant, with a consistent risk of underdosing-related treatment failure and/or potential onset of bacterial resistance. It should also be taken into account that renal replacement therapies are often not standardized in critically ill patients, and their impact on plasma drug concentrations may substantially vary in relation to membrane characteristics, treatment modality, and delivered dialysis dose. Thus, in this clinical scenario, the knowledge of the pharmacokinetic and pharmacodynamic properties of different antimicrobial classes is crucial to tailor maintenance dose and/or time interval according to clinical needs. Finally, especially for antimicrobials known for a tight therapeutic range, therapeutic drug monitoring is strongly suggested to guide dosing adjustment in complex clinical settings, such as septic patients with acute kidney injury undergoing renal replacement therapy.

Continuous Renal Replacement Therapy: Who, When, Why, and How

Continuous renal replacement therapy (CRRT) is commonly used to provide renal support for critically ill patients with acute kidney injury, particularly patients who are hemodynamically unstable. A variety of techniques that differ in their mode of solute clearance may be used, including continuous venovenous hemofiltration with predominantly convective solute clearance, continuous venovenous hemodialysis with predominantly diffusive solute clearance, and continuous venovenous hemodiafiltration, which combines both dialysis and hemofiltration. The present article compares CRRT with other modalities of renal support and reviews indications for initiation of renal replacement therapy, as well as dosing and technical aspects in the management of CRRT.

Pharmacokinetics-pharmacodynamics issues relevant for the clinical use of beta-lactam antibiotics in critically ill patients

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients and beta-lactams are the most common antibiotic class used. Critically ill patient's pathophysiological factors lead to altered pharmacokinetics and pharmacodynamics of beta-lactams.A comprehensive bibliographic search in PubMed database of all English language articles published from January 2000 to December 2017 was performed, allowing the selection of articles addressing the pharmacokinetics or pharmacodynamics of beta-lactam antibiotics in critically ill patients.In critically ill patients, several factors may increase volume of distribution and enhance renal clearance, inducing high intra- and inter-patient variability in beta-lactam concentration and promoting the risk of antibiotic underdosing. The duration of infusion of beta-lactams has been shown to influence the fT > minimal inhibitory concentration and an improved beta-lactam pharmacodynamics profile may be obtained by longer exposure with more frequent dosing, extended infusions, or continuous infusions.The use of extracorporeal support techniques in the critically ill may further contribute to this problem and we recommend not reducing standard antibiotic dosage since no drug accumulation was found in the available literature and to maintain continuous or prolonged infusion, especially for the treatment of infections caused by multidrug-resistant bacteria.Prediction of outcome based on concentrations in plasma results in overestimation of antimicrobial activity at the site of infection, namely in cerebrospinal fluid and the lung. Therefore, although no studies have assessed clinical outcome, we recommend using higher than standard dosing, preferably with continuous or prolonged infusions, especially when treating less susceptible bacterial strains at these sites, as the pharmacodynamics profile may improve with no apparent increase in toxicity.A therapeutic drug monitoring-guided approach could be particularly useful in critically ill patients in whom achieving target concentrations is more difficult, such as obese patients, immunocompromised patients, those infected by highly resistant bacterial strains, patients with augmented renal clearance, and those undergoing extracorporeal support techniques.

Daptomycin Pharmacokinetics and Pharmacodynamics in Septic and Critically Ill Patients

Infections, including sepsis, are associated with high mortality rates in critically ill patients in the intensive care unit (ICU). Appropriate antibiotic selection and adequate dosing are important for improving patient outcomes. Daptomycin is bactericidal in bloodstream infections caused by Staphylococcus aureus and other Gram-positive pathogens cultured in ICU patients. The drug has concentration-dependent activity, and the area under the curve/minimum inhibitory concentration ratio is the pharmacokinetic/pharmacodynamic (PK/PD) index that best correlates with daptomycin activity, whereas toxicity correlates well with daptomycin plasma trough concentrations (or minimum concentration [C min]). Adequate daptomycin exposure can be difficult to achieve in ICU patients; multiple PK alterations can result in highly variable plasma concentrations, which are difficult to predict. For this reason, therapeutic drug monitoring could help clinicians optimize daptomycin dosing, thus improving efficacy while decreasing the likelihood of serious adverse events. This paper reviews the literature on daptomycin in ICU patients with sepsis, focusing on dosing and PK and PD parameters.

Individualised antimicrobial dosing in critically ill patients undergoing continuous renal replacement therapy: focus on total drug clearance

Background

Continuous renal replacement therapy (CRRT) is common practice in critical care patients with acute renal failure.

Objectives

To evaluate the adequacy of antimicrobial doses calculated based on the total drug clearance and dose recommended by different guides in critically ill patients undergoing CRRT.

Methods

Retrospective observational study. Patients admitted to a critical care unit during May 2014 to May 2016 and subjected to CRRT were included. The recommended dose was established as the product of the usual dose of the drug by total drug clearance.

Results

177 antimicrobial agents, used in 64 patients were analysed; 45 (25.4%) antimicrobials were given in an insufficient dose (<20%) according to the theoretical calculation. Following the recommendations in the revised guidelines, between 10% and 20% of antimicrobials were given in insufficient doses. A higher success rate of treatment in those patients not receiving a low drug dosage was seen (35.2% vs 24.0%).

Conclusions

There is a great disparity between the antimicrobial dose prescribed, recommended and calculated based on drug clearance in critically ill patients undergoing CRRT.

Population pharmacokinetics of daptomycin in adult patients undergoing continuous renal replacement therapy

Aim

The objective of this population pharmacokinetic (PK) analysis was to provide guidance for the dosing interval of daptomycin in patients undergoing continuous renal replacement therapy (CRRT).

Methods

A previously published population PK model for daptomycin was updated with data from patients undergoing continuous veno‐venous haemodialysis (CVVHD; n = 9) and continuous veno‐venous haemodiafiltration (CVVHDF; n = 8). Model‐based simulations were performed to compare the 24 h AUC, C_max and C_min of daptomycin following various dosing regimens (4, 6, 8, 10, and 12 mg kg⁻¹ every [Q] 24 h and Q48 h), with the safety and efficacy exposure references for Staphylococcus aureus bacteraemia/right‐sided infective endocarditis.

Results

The previously developed daptomycin structural population PK model could reasonably describe data from the patients on CRRT. The clearance in patients undergoing CVVHDF and CVVHD was estimated at 0.53 and 0.94 l h⁻¹, respectively, as compared with 0.75 l h⁻¹ in patients with creatinine clearance (CrCl) ≥ 30 ml min⁻¹. Daptomycin Q24 h dosing in patients undergoing CRRT resulted in optimal exposure for efficacy, with AUC comparable to that in patients with CrCl ≥ 30 ml min⁻¹. In contrast, Q48 h dosing was associated with considerably lower AUC_24–48h in all patients for doses up to 12 mg kg⁻¹ and is therefore inappropriate.

Conclusions

Q24 h dosing of daptomycin up to 12 mg kg⁻¹ provides comparable drug exposure in patients on CVVHD and in those with CrCl ≥ 30 ml min⁻¹. Daily daptomycin use up to 8 mg kg⁻¹ doses are appropriate for patients on CVVHDF, but higher doses may increase the risk of toxicity.

Comparison of Urine Output among Patients Treated with More Intensive Versus Less Intensive RRT: Results from the Acute Renal Failure Trial Network Study

BACKGROUND AND OBJECTIVES

Intensive RRT may have adverse effects that account for the absence of benefit observed in randomized trials of more intensive versus less intensive RRT. We wished to determine the association of more intensive RRT with changes in urine output as a marker of worsening residual renal function in critically ill patients with severe AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Acute Renal Failure Trial Network Study (n=1124) was a multicenter trial that randomized critically ill patients requiring initiation of RRT to more intensive (hemodialysis or sustained low-efficiency dialysis six times per week or continuous venovenous hemodiafiltration at 35 ml/kg per hour) versus less intensive (hemodialysis or sustained low-efficiency dialysis three times per week or continuous venovenous hemodiafiltration at 20 ml/kg per hour) RRT. Mixed linear regression models were fit to estimate the association of RRT intensity with change in daily urine output in survivors through day 7 (n=871); Cox regression models were fit to determine the association of RRT intensity with time to ≥50% decline in urine output in all patients through day 28.

RESULTS

Mean age of participants was 60±15 years old, 72% were men, and 30% were diabetic. In unadjusted models, among patients who survived ≥7 days, mean urine output was, on average, 31.7 ml/d higher (95% confidence interval, 8.2 to 55.2 ml/d) for the less intensive group compared with the more intensive group (P=0.01). More intensive RRT was associated with 29% greater unadjusted risk of decline in urine output of ≥50% (hazard ratio, 1.29; 95% confidence interval, 1.10 to 1.51).

CONCLUSIONS

More intensive versus less intensive RRT is associated with a greater reduction in urine output during the first 7 days of therapy and a greater risk of developing a decline in urine output of ≥50% in critically ill patients with severe AKI.

Phenytoin removal by continuous venovenous hemofiltration

OBJECTIVE

To describe 2 cases of clinically significant phenytoin removal during continuous venovenous hemofiltration (CVVH) and review the relevant literature regarding phenytoin removal by renal replacement modalities.

CASE SUMMARY

A 64-year-old female with chronic kidney disease and cirrhosis was admitted to the intensive care unit (ICU) with a traumatic subdural hematoma and seizures. The patient received a loading dose of intravenous phenytoin 1000 mg, followed by maintenance intravenous administration of phenytoin 100 mg and levetiracetam 250 mg every 12 hours. CVVH was initiated for acidosis. A 63-year-old male was admitted to the ICU after cardiac surgery complicated by hypotension. CVVH was initiated for fluid overload, and phenytoin was initiated 3 days later for seizures. A loading dose of intravenous phenytoin 2700 mg was administered, followed by maintenance dosing of intravenous phenytoin 150 mg every 8 hours. Concentrations of unbound phenytoin in serum and CVVH effluent samples were measured during concomitant treatment in each patient. In both patients, serum and effluent concentrations of unbound phenytoin fell steadily while they were on CVVH. Clearance of phenytoin by CVVH was calculated, as was the daily removal of phenytoin, as a percentage of total daily phenytoin dosage during each sampling period. Phenytoin clearance by CVVH ranged from 11 to 13 mL/min in these patients.

DISCUSSION

The clearance of phenytoin with CVVH in these 2 patients was much higher than the renal clearance of phenytoin reported in healthy volunteers with normal renal function. Previous case reports have demonstrated that only small, clinically insignificant amounts of phenytoin are removed by hemodialysis, and the only published report of phenytoin removal by continuous renal replacement therapy used hemofiltration rates much lower than those used in the 2 cases described here.

CONCLUSIONS

These cases demonstrate that a substantial amount-approximately 30%-of total daily phenytoin dose may be removed by CVVH, and patients may require higher than expected empiric doses. Phenytoin concentrations should be closely monitored in critically ill patients receiving CVVH.

Effect of continuous venovenous hemofiltration dose on achievement of adequate vancomycin trough concentrations

The vancomycin dose necessary for the achievement of target serum trough concentrations during continuous venovenous hemofiltration (CVVH) remains to be elucidated. This was a retrospective cohort study of critically ill adults at a tertiary medical center on concurrent CVVH and vancomycin between 2006 and 2010 with a steady-state vancomycin trough concentration. The 87 included patients were grouped according to low (≤30 ml/kg/h; n = 10) or high (>30 ml/kg/h; n = 77) CVVH hemofiltration rate (HFR) for analysis. Vancomycin goal trough achievement occurred in only 32 (37%) patients. The primary endpoint of trough attainment significantly differed between HFR subgroups: 90% versus 30% in low- and high-HFR individuals, respectively (P < 0.001). Patients with subtherapeutic trough concentrations had a median (interquartile range) HFR of 40 ml/kg/h (range, 37 to 47 ml/kg/h) compared to 36 ml/kg/h (range, 30 to 39 ml/kg/h) in those who achieved the trough goal. Irrespective of goal trough, an inverse correlation existed between HFR and serum vancomycin concentration (r = -0.423; P < 0.001). In the subgroup of 14 methicillin-resistant Staphylococcus aureus (MRSA) patients, trough achievement was similar to the aggregate cohort (36%). Mortality at 28 days was unrelated to trough achievement in both the overall sample (P = 0.516) and in culture-positive MRSA patients (P = 0.396). Critically ill patients undergoing CVVH therapy may experience clinically significant reductions in goal vancomycin troughs. The results of the present study justify prospective evaluations in this population to determine the optimal vancomycin dosing strategy for attainment of goal trough concentrations.

Longitudinal hemodiafilter performance in modeled continuous renal replacement therapy

BACKGROUND/AIMS

With advanced anticoagulation, many institutions operate continuous renal replacement therapy (CRRT) circuits longer than manufacturers' recommendations. This extended use may change hemodiafilter performance and clearance properties. However, hemodiafilter performance over time has not been assessed. We investigated solute clearance over time in modeled CRRT.

METHODS

In vitro continuous hemofiltration (CH) and continuous hemodialysis (CD) were operated for 48 h using AN69 polyacrylonitrile, cellulose triacetate, F70 polysulfone, and Optiflux F160NR polysulfone hemodiafilters with citrated bovine blood. Urea, creatinine, gentamicin, vancomycin, and albumin clearances were assessed in CH (ultrafiltration rates = 1 and 3 l/h). Clearances of urea, creatinine, gentamicin, and albumin, were assessed in CD with dialysate flow rate of 2 l/h.

RESULTS

Solute CH clearances were significantly higher at 3 l/h. Only creatinine and gentamicin clearances were affected by time. Creatinine CD clearance significantly declined at 48 h for all hemodiafilters, especially polysulfone hemodiafilters.

CONCLUSIONS

CRRT duration affects solute transmembrane clearance. Clinicians should consider hemodiafilter age when assessing hemodialysis dose or drug clearance.

Antibiotic dosing in critically ill patients with acute kidney injury

A common cause of acute kidney injury (AKI) is sepsis, which makes appropriate dosing of antibiotics in these patients essential. Drug dosing in critically ill patients with AKI, however, can be complicated. Critical illness and AKI can both substantially alter pharmacokinetic parameters as compared with healthy individuals or patients with end-stage renal disease. Furthermore, drug pharmacokinetic parameters are highly variable within the critically ill population. The volume of distribution of hydrophilic agents can increase as a result of fluid overload and decreased binding of the drug to serum proteins, and antibiotic loading doses must be adjusted upwards to account for these changes. Although renal elimination of drugs is decreased in patients with AKI, residual renal function in conjunction with renal replacement therapies (RRTs) result in enhanced drug clearance, and maintenance doses must reflect this situation. Antibiotic dosing decisions should be individualized to take into account patient-related, RRT-related, and drug-related factors. Efforts must also be made to optimize the attainment of antibiotic pharmacodynamic goals in this population.

Therapeutic drug monitoring of piperacillin-tazobactam using spent dialysate effluent in patients receiving continuous venovenous hemodialysis

Sepsis and multisystem organ failure are common diagnoses affecting nearly three-quarters of a million Americans annually. Infection is the leading cause of death in acute kidney injury, and the majority of critically ill patients who receive continuous dialysis also receive antibiotics. Dialysis equipment and prescriptions have gradually changed over time, raising concern that current drug dosing recommendations in the literature may result in underdosing of antibiotics. Our research group directed its attention toward antibiotic dosing strategies in patients with acute renal failure (ARF), and we sought data confirming that patients receiving continuous dialysis and antibiotics actually were achieving therapeutic plasma drug levels during treatment. In the course of those investigations, we explored "fast-track" strategies to estimate plasma drug concentrations. As most antimicrobial antibiotics are small molecules and should pass freely through modern high-flux hemodialyzer filters, we hypothesized that continuous renal replacement therapy (CRRT) effluent could be used as the medium for drug concentration measurement by reverse-phase high-pressure liquid chromatography (HPLC). Here we present the first data demonstrating this approach for piperacillin-tazobactam. Paired blood and dialysate trough-peak-trough samples were drawn from 19 patients receiving piperacillin-tazobactam and continuous venovenous hemodialysis (CVVHD). Total, free, and dialysate drug concentrations were measured by HPLC. Dialysate drug levels predicted plasma free drug levels well (r(2) = 0.91 and 0.92 for piperacillin and tazobactam, respectively) in all patients. These data suggest a strategy for therapeutic drug monitoring that minimizes blood loss from phlebotomy and simplifies analytic procedures.

Review article: Renal support in critical illness

PURPOSE

This review provides a focused and comprehensive update on established and emerging evidence in acute renal replacement therapy (RRT) for critically ill patients with acute kidney injury (AKI).

PRINCIPAL FINDINGS

There have been considerable technological innovations in the methods and techniques for provision of extracorporeal RRT in critical illness. These have greatly expanded our capability to provide both renal and non-renal life-sustaining organ support for critically ill patients. Recent data suggest earlier initiation of RRT in AKI may confer an advantage for survival and renal recovery. Two large trials have recently shown no added benefit to augmented RRT dose delivery in AKI. Observational data have also suggested that fluid accumulation in critically ill patients with AKI is associated with worse clinical outcome. However, several fundamental clinical questions remain to be answered, including issues regarding the time to ideally initiate/discontinue RRT, the role of high-volume hemofiltration or other blood purification techniques in sepsis, and extracorporeal support for combined liver-kidney failure. Extracorporeal support with RRT in sepsis, rhabdomyolysis, and liver failure are discussed, along with strategies for drug dosing and management of RRT in sodium disorders.

CONCLUSIONS

We anticipate that this field will continue to expand to promote research and innovation, hopefully for the benefit of sick critically ill patients.

The dark side of high-intensity renal replacement therapy of acute kidney injury in critically ill patients

The impact of intensity or dose of renal replacement therapy (RRT) on outcome of critically ill patients has been a matter of controversy. Most definitions of an adequate dose of acute RRT are based on urea removal, while ignoring other crucial aspects of RRT adequacy in acute kidney injury (AKI). Although some clinical trials have found an improvement in survival with higher doses of intermittent hemodialysis or continuous RRT, results have not been consistent across all studies. The largest trials suggest that there is no additional survival benefit with doses of 35-45 ml/kg/h (CRRT) or daily intermittent hemodialysis. On the other hand, high-intensity treatment may cause life-threatening complications and thereby counteract the benefits of higher small-solute clearance. One important area for future investigations is the need to characterize the potential harm of high-dose RRT for AKI in critically ill patients.

Dosing of daptomycin in intensive care unit patients with acute kidney injury undergoing extended dialysis--a pharmacokinetic study

BACKGROUND

Daptomycin is a new intravenous cyclic lipopeptide antibiotic, licensed for the treatment of complicated skin and soft tissue infections caused by Gram-positive organisms including both susceptible and resistant strains of Staphylococcus aureus and for the treatment of various infections due to susceptible organisms, including serious and life-threatening Gram-positive infections, vancomycin-resistant enterococcal infections and right-sided endocarditis with associated bacteremia. Currently, no dosing recommendations exist for this drug for patients with acute kidney injury (AKI) undergoing renal replacement therapy. The aim of this study was to evaluate pharmacokinetics of daptomycin in critically ill patients with AKI undergoing extended dialysis (ED), a frequently used mean of renal replacement therapies in intensive care units (ICUs) around the world. Patients and methods. A prospective, single-dose pharmacokinetic study was performed in the medical and surgical ICUs of a tertiary care center. The aim was to investigate critically ill patients with anuric AKI being treated with ED and receiving daptomycin (n = 10). Daptomycin (6 mg/kg) was administered 8 h before ED was started.

RESULTS

Key pharmacokinetic parameters like half-life in critically ill patients treated with ED were comparable to healthy controls. The dialyser clearance for daptomycin was 63 +/- 9 ml/min. Based on the amount of the drug recovered from the collected spent dialysate, the mean fraction of the drug removed by one dialysis treatment was 23.3%.

CONCLUSION

Our data suggest that patients treated with ED using a high-flux dialyzer (polysulphone, 1.3 m(2); blood and dialysate flow, 160 ml/min; ED time, 480 min) and employing current dosing regimen, 6 mg/kg daptomycin every 48 h, run the risk of becoming significantly under dosed if one adheres to a twice daily dosing schedule that is recommended for patients on maintenance haemodialysis. Our data suggest that a daily dose of 6 mg/kg daptomycin is necessary in this special patient population to avoid under dosing, which may have detrimental effects in critically ill patients suffering from life-threatening infections.

The impact of continuous renal replacement therapy on drug therapy

Critically ill patients with multisystem organ failure often require daily administration of large volumes of fluid to provide electrolyte and nutrition support, medications, and blood products. This often results in fluid overload, which has historically been managed with intermittent hemodialysis (IHD). Unfortunately, IHD entails a high rate of fluid and solute removal that often exacerbates hemodynamic instability. Accordingly, continuous renal replacement therapy (CRRT), involving slow and continuous removal of water and solutes from the plasma, is currently preferred for managing these patients.

Drug dosing during continuous renal replacement therapy

Continuous renal replacement therapy (CRRT) has given clinicians an important option in the care of critically ill patients. The slow and continuous dialysate and ultrafiltrate flow rates that are employed with CRRT can yield drug clearances similar to an analogous glomerular filtration rate of the native kidneys. Advantages such as superior volume control, excellent metabolic control, and hemodynamic tolerance by critically ill patients are well documented, but an understanding of drug dosing for CRRT is still a bit of a mystery. Although some pharmaceutical companies have dedicated postmarket research in this direction, many pharmaceutical companies have chosen not to pursue this information as it is not mandated and represents a relatively small part of their market. This lack of valuable information has created many challenges in the care of the critically ill patient as intermittent hemodialysis drug dosing recommendations cannot be extrapolated to CRRT. This drug dosing review will highlight factors that clinicians should consider when determining a pharmacotherapy regimen for a patient receiving CRRT.

[Drugs dosing in intensive care unit during continuous renal replacement therapy]

Drug dosing in the intensive care unit can be challenging. Acute kidney injury (AKI) is a common complication of sepsis and a part of multiple organ dysfunction syndrome. Continuous renal replacement therapy (CRRT) is increasingly used as dialysis therapy in this critically ill population. Available data demonstrate that sepsis, AKI and different modalities of CRRT can profoundly change drugs pharmacokinetic. The severity of these changes depends on molecules characteristics (volume of distribution, plasma protein binding, molecular weight, plasma half-life, plasma clearance), patient itself (volemia, residual renal function, tissue perfusion, hepatic dysfunction) and modality of CRRT (diffusion, convection, adsorption). There are no available recommendations to adapt drug dosing in a given critically ill patient with a given modality of CRRT. It is necessary to fully understand the different methods of CRRT and drug pharmacokinetic to prescribe the appropriate dose and to avoid under or potentially toxic overdosing. Monitoring the plasma level of drug - when available - can establish a relation between the blood concentration and its effect; thus, facilitating drug dosing.

Ertapenem clearance during modeled continuous renal replacement therapy

PURPOSE

To determine ertapenem transmembrane clearance (CLtm) during continuous renal replacement therapy (CRRT) using a validated in vitro model.

METHODS

Ertapenem clearance during continuous hemofiltration and hemodialysis was assessed with AN69 and polysulfone hemodiafilters at 4 dialysate (Qd) and ultrafiltration rates (Quf): 1, 2, 3, and 6 l/hour. Blood and dialysate samples were collected at each flow rate and assayed for urea (control solute) and ertapenem concentrations. The experiment was repeated 5 times for each hemodiafilter type. Ertapenem and urea sieving coefficient (SC) and saturation coefficient (SA) were assessed, and CLtm calculated.

RESULTS

In continuous hemofiltration mode, urea and ertapenem SC ranged from 1.00 to 1.19 at all Quf and did not differ between hemodiafilter types. Consequently, convective CLtm also did not differ between hemodiafilters. In continuous dialysis mode, urea Cltm did not differ between hemodiafilter types at any Qd. However, ertapenem SA and CLtm were significantly different between hemodiafilter types at Qd 6l/hour (p<0.001). As Qd increased, mean +/- SD AN69 SA declined significantly from 0.87 +/- 0.12 at Qd 1 l/hour to 0.45 +/- 0.02 at Qd 6 l/hour (p<0.001). Ertapenem SA did not differ at any Qd with the polysulfone hemodiafilter (range 0.71-0.80).

CONCLUSION

Ertapenem was cleared substantially in these in vitro CRRT models. However, our findings illustrate discordance between our observed SC and SA and the published unbound fraction of ertapenem. This finding has been reported with many other drugs, including carbapenem antibiotics. If in vivo studies corroborate our SA and SC findings, dosage adjustment for patients receiving CRRT will be required.

Antimicrobial dosing strategies in critically ill patients with acute kidney injury and high-dose continuous veno-venous hemofiltration

PURPOSE OF REVIEW

Delivery of appropriate antimicrobial therapy is a great challenge during continuous veno-venous hemofiltration (CVVH), particularly if the recommended higher doses are applied. The present contribution discusses the principles of drug dosing during CVVH and compares the various proposed dosing strategies.

RECENT FINDINGS

The basic principles underlying removal of antibiotics during CVVH and the published dosing strategies are reviewed. The key factor to consider is the fractional CVVH clearance (FrCVVH). Critical illness and acute kidney injury, however, may dramatically affect the pharmacokinetic properties of a drug and thus FrCVVH. Five dosing strategies have been proposed on the basis of either available references, total creatinine clearance, the reduction in total body clearance, the maintenance dose multiplication factor, or therapeutic drug monitoring. Dose predictions according to the various strategies show reasonable approximations for some but not all antibiotics.

SUMMARY

The delivery of appropriate antimicrobial therapy during CVVH leaves us with uncertainty and presents a great challenge. To ensure efficacy and prevent toxicity, therapeutic drug monitoring is highly recommended. In the absence of therapeutic drug monitoring, adequate concentrations can only be inferred from clinical response. For nontoxic antibiotics overdosing is preferred to underdosing because the danger of underdosing is far greater than that of overdosing.

Risk of underdosing of ampicillin/sulbactam in patients with acute kidney injury undergoing extended daily dialysis--a single case

The fixed antibacterial combination of ampicillin and sulbactam is frequently used for various infections. The normal kidneys eliminate approximately 60% of ampicillin (371.39 Da) and sulbactam (255.22 Da). Concomitant with the decline in renal function, the terminal elimination half-life increases from 1 up to 24 h in patients with ESRD. Patients on three times weekly low flux haemodialysis exhibit a half-life of 2.3 h on and 17.4 h off dialysis. In contrast, in the present observation the elimination half-life in a single patient with acute kidney injury undergoing extended daily dialysis (EDD) with a polysulphone membrane was 1.5 h, indicating that the current dosing regimen for haemodialysis outpatients (ampicillin/sulbactam 2.0/1.0 g/day) would result in a significant underdosing for patients undergoing EDD.

Pharmacokinetics/pharmacodynamics of antibacterials in the Intensive Care Unit: setting appropriate dosing regimens

Patients admitted to Intensive Care Units (ICUs) are at very high risk of developing severe nosocomial infections. Consequently, antimicrobials are among the most important and commonly prescribed drugs in the management of these patients. Critically ill patients in ICUs include representatives of all age groups with a range of organ dysfunction related to severe acute illness that may complicate long-term illness. The range of organ dysfunction, together with drug interactions and other therapeutic interventions (e.g. haemodynamically active drugs and continuous renal replacement therapies), may strongly impact on antimicrobial pharmacokinetics in critically ill patients. In the last decade, it has become apparent that the intrinsic pharmacokinetic (PK) and pharmacodynamic (PD) properties are the major determinants of in vivo efficacy of antimicrobial agents. PK/PD parameters are essential in facilitating the translation of microbiological activity into clinical situations, ensuring a successful outcome. In this review, we analyse the typical patterns of antimicrobial activity and the corresponding PK/PD parameters, with a special focus on a PK/PD dosing approach of the antimicrobial agent classes commonly utilised in the ICU setting.

The adsorption of vancomycin by polyacrylonitrile, polyamide, and polysulfone hemofilters

The aim of this study was to characterize vancomycin adsorption by polyacrylonitrile (PAN), polyamide, and polysulfone hemofilters using an in vitro model of hemofiltration. Vancomycin (36 mg) was added to a blood-crystalloid mixture of known volume (target concentration of 50 mg/L) and pumped around a closed circuit. Adsorption, which was calculated from the fall in concentration over 120 min, was significantly greater by 0.6-m(2) PAN filters (10.08 +/- 2.26 mg) than by 0.6-m(2) polyamide (5.20 +/- 1.82 mg) or 0.7-m(2) polysulfone (4.80 +/- 2.40 mg) filters (P < 0.05). Cumulative adsorption was not changed by the addition of 500-mL lactated Ringer's solution (to reduce the circulating vancomycin concentration). These data show that although adsorption of vancomycin by PAN, polyamide, and polysulfone hemofilters occurs, the absolute adsorption is small. Adsorption is dependent on filter material and is not reversed by a decrease in circulating concentration.

Drug dosing considerations in alternative hemodialysis

The provision of renal replacement therapy for patients with chronic kidney disease has been reasonably standardized for decades, with thrice-weekly hemodialysis being the standard. Short-daily and nocturnal hemodialysis are 2 new hemodialysis techniques, each are administered 6 to 7 days a week but differ primarily in the duration of the treatment and blood-flow rate. The emergence of these hemodialysis regimens has shown promise in attenuating some of the complications associated with chronic kidney disease. The benefits of these daily regimens are postulated to be a result of enhanced solute clearance and improved extracellular volume management. The improved solute clearance associated with daily hemodialysis is likely to lead to altered dialytic clearance of drugs given to patients receiving these therapies. The purpose of this paper is to review the concepts pertinent to drug removal by hemodialysis and discuss the issues related to these new dialysis techniques and how they may have a impact on drug removal and the design of dosing regimens.

Pharmacokinetics of Moxifloxacin and Levofloxacin in Intensive Care Unit Patients Who Have Acute Renal Failure and Undergo Extended Daily Dialysis

Extended daily dialysis (EDD) is increasingly popular in the treatment of acute renal failure (ARF). EDD could remove drugs to a much different degree compared with intermittent standard hemodialysis or continuous renal replacement therapies; however, there are only scarce data on how EDD influences the pharmacokinetics of frequently used drugs. The aim of this study was to determine the pharmacokinetics of two quinolone antibiotics in patients who had anuric ARF and were being treated with EDD. Adult patients who were in the intensive care unit at a tertiary care university hospital and receiving moxifloxacin (n = 10) or levofloxacin (n = 5) therapy were included. The antibiotics were administered intravenously 8 h (400 mg of moxifloxacin) or 12 h (500 mg of levofloxacin) before EDD to study pharmacokinetics off and on EDD. Treatment lasted 8 h; blood and dialysate flow rates were 160 ml/min. In addition to standard pharmacokinetic parameters, the total dialysate concentration of both drugs was measured using a technically simple single-pass batch dialysis system for EDD. Moxifloxacin pharmacokinetics in critically ill patients who had ARF and were undergoing EDD were similar to those in healthy subjects without renal impairment. Levofloxacin, although removed by EDD, had a lower total clearance compared with healthy subjects. According to these findings, anuric critically ill patients who are undergoing EDD should be treated with the standard dosage of moxifloxacin (400 mg/d intravenously). The levofloxacin dosage, however, should be reduced according to the intensity of renal replacement therapy.

Antimicrobial therapy in critically ill patients: a review of pathophysiological conditions responsible for altered disposition and pharmacokinetic variability

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients. Selecting the appropriate antimicrobial at the commencement of therapy, both in terms of spectrum of activity and dose and frequency of administration according to concentration or time dependency, is mandatory in this setting. Despite appropriate standard dosage regimens, failure of the antimicrobial treatment may occur because of the inability of the antimicrobial to achieve adequate concentrations at the infection site through alterations in its pharmacokinetics due to underlying pathophysiological conditions. According to the intrinsic chemicophysical properties of antimicrobials, hydrophilic antimicrobials (beta-lactams, aminoglycosides, glycopeptides) have to be considered at much higher risk of inter- and intraindividual pharmacokinetic variations than lipophilic antimicrobials (macrolides, fluoroquinolones, tetracyclines, chloramphenicol, rifampicin [rifampin]) in critically ill patients, with significant frequent fluctuations of plasma concentrations that may require significant dosage adjustments. For example, underexposure may occur because of increased volume of distribution (as a result of oedema in sepsis and trauma, pleural effusion, ascites, mediastinitis, fluid therapy or indwelling post-surgical drainage) and/or enhanced renal clearance (as a result of burns, drug abuse, hyperdynamic conditions during sepsis, acute leukaemia or use of haemodynamically active drugs). On the other hand, overexposure may occur because of a drop in renal clearance caused by renal impairment. Care with all these factors whenever choosing an antimicrobial may substantially improve the outcome of antimicrobial therapy in critically ill patients. However, since these situations may often coexist in the same patient and pharmacokinetic variability may be unpredictable, the antimicrobial policy may further benefit from real-time application of therapeutic drug monitoring, since this practice, by tailoring exposure to the individual patient, may consequently be helpful both in improving the outcome of antimicrobial therapy and in containing the spread of resistance in the hospital setting.

Technology Insight: treatment of renal failure in the intensive care unit with extended dialysis

Sustained low-efficiency dialysis (SLED) is an increasingly popular extracorporeal renal replacement therapy for patients with renal failure in the intensive care unit (ICU). Several centers across the world employ this 'hybrid' technique, which has advantages of both intermittent and continuous methods. The goal of these centers is to provide an easy-to-perform treatment with reduced solute clearances for prolonged periods. Many centers use standard, sophisticated dialysis equipment for SLED. An increasing number of hospitals in Europe and South America employ a single-pass batch dialysis system, the procedural simplicity of which makes it an ideal modality for SLED in the ICU. All systems offer the advantages of flexible timing of treatment and reduced costs; their ease of handling means that SLED is readily accepted by ICU staff. Prospective controlled studies have shown that SLED clears small solutes with an efficacy comparable to that of intermittent hemodialysis and continuous venovenous hemofiltration (even when the latter employs high rates of fluid substitution). Cardiovascular tolerability associated with SLED is similar to that associated with continuous renal replacement therapy, even in severely ill patients. Nocturnal dialysis -- a special form of SLED -- has all the advantages outlined above, with the added benefit of unrestricted physician access to the patient during the day, minimizing the interference of renal replacement therapy with other ICU activities.