Deborah A. Pasko

Drug dosing consideration in patients with acute and chronic kidney disease—a clinical update from Kidney Disease: Improving Global Outcomes (KDIGO)

Drug dosage adjustment for patients with acute or chronic kidney disease is an accepted standard of practice. The challenge is how to accurately estimate a patients kidney function in both acute and chronic kidney disease and determine the influence of renal replacement therapies on drug disposition. Kidney Disease: Improving Global Outcomes (KDIGO) held a conference to investigate these issues and propose recommendations for practitioners, researchers, and those involved in the drug development and regulatory arenas. The conference attendees discussed the major challenges facing drug dosage adjustment for patients with kidney disease. In particular, although glomerular filtration rate is the metric used to guide dose adjustment, kidney disease does affect nonrenal clearances, and this is not adequately considered in most pharmacokinetic studies. There are also inadequate studies in patients receiving all forms of renal replacement therapy and in the pediatric population. The conference generated 37 recommendations for clinical practice, 32 recommendations for future research directions, and 24 recommendations for regulatory agencies (US Food and Drug Administration and European Medicines Agency) to enhance the quality of pharmacokinetic and pharmacodynamic information available to clinicians. The KDIGO Conference highlighted the gaps and focused on crafting paths to the future that will stimulate research and improve the global outcomes of patients with acute and chronic kidney disease.

Calcium channel blockers: pharmacology and place in therapy of pediatric hypertension

Abstract The calcium channel blockers (CCBs) are a diverse group of antihypertensive medications with variable pharmacokinetics and clinical effects. Although CCBs have been widely applied to the treatment of hypertensive children, data regarding the pharmacokinetics, efficacy and safety of these agents in children are extremely limited. In this review we briefly summarize the mechanism of action of CCBs and then summarize pertinent pharmacokinetic information on each of the CCBs commonly used in children, including amlodipine, diltiazem, felodipine, isradipine, intravenous nicardipine, nifedipine and verapamil. Clinically important drug interactions and adverse effects are discussed, as well as the potential role of CCBs in renal protection. Available pediatric efficacy and safety data are summarized, and recommendations made regarding the rational use of CCBs in the management of pediatric hypertension.

Daptomycin clearance during modeled continuous renal replacement therapy

Background/Aims: Pharmacotherapy in critically ill patients receiving continuous renal replacement therapies (CRRT) is challenging due to the lack of published information to base dosing regimens. Methods: Daptomycin’s transmembrane clearance during continuous hemofiltration and hemodialysis was assessed using an in vitro model with AN69 and polysulfone hemodiafilters at varying ultrafiltrate and dialysate flow rates (1, 2, 3 and 6 l/h). Results: During continuous hemofiltration, mean daptomycin sieving coefficient ranged from 0.14 to 0.20. Transmembrane clearances were significantly different between filter types for ultrafiltration rates of 2, 3 and 6 l/h. For continuous hemodialysis, mean daptomycin saturation coefficient ranged from 0.05 to 0.15. AN69-based daptomycin clearances were significantly lower than polysulfone values at dialysate flow rates of 2, 3 and 6 l/h. Conclusion: The extent of daptomycin’s transmembrane clearance is dependent on hemodiafilter type, dialysate and ultrafiltration rates. CRRT with high ultrafiltrate or dialysate rates may result in substantial daptomycin clearances.

The epidemiology of drug-induced disorders: the kidney

The epidemiology of drug-induced renal disorders is a complex topic. Drug-associated nephrotoxicity accounts for 18 – 27% of all acute kidney injury cases in US hospitals. Medications can affect all aspects of the kidney, and drugs that are associated with renal dysfunction are used commonly in clinical practice. The article reviews six major mechanisms of drug-induced renal dysfunction as well as lists the major medications involved. NSAIDs, aminoglycosides, amphotericin B and calcineurin inhibitors are just some examples of drugs that contribute to renal dysfunction. The medical community must be aware of patient risk factors for nephrotoxicity, as well as the drugs inherent nephrotoxic potential, when prescribing and administering medications.

Enhanced clearance of highly protein-bound drugs by albumin-supplemented dialysate during modeled continuous hemodialysis

BACKGROUND In 2006, there were 16 796 toxic exposures attributed to valproic acid (VPA), carbamazepine (CBZ) and phenytoin (PHT) reported to the US Toxic Exposure Surveillance System. Of these, 30% (5046) were treated in a health care facility with 12 cases resulting in death. These drugs are highly protein bound and poorly dialyzable; however, it has been suggested that albumin-supplemented dialysate may enhance dialytic clearance. We investigated whether the addition of albumin to dialysate affects dialytic clearance of VPA, CBZ and PHT. METHODS VPA, CBZ and PHT were added to a bovine blood-based in vitro continuous hemodialysis circuit, which included a polysulfone or an AN69 hemodialyzer. VPA, CBZ and PHT clearances were calculated from spent dialysate and pre-dialyzer plasma concentrations. VPA, CBZ and PHT clearances with control (albumin-free) dialysate were compared to clearances achieved with 2.5% or 5% human albumin-containing dialysate. The influences of blood flow (180 and 270 mL/min) and dialysate flow (1, 2 and 4 L/h) on dialysis clearance were also assessed. RESULTS The addition of 2.5% albumin to dialysate significantly enhanced dialytic clearance of VPA and CBZ, but not PHT. Use of 5% albumin dialysate further increased VPA and CBZ clearance. Overall, drug clearance was related directly to dialysate flow but independent of blood flow. CONCLUSION Continuous hemodialysis with albumin-supplemented dialysate significantly enhanced VPA and CBZ, but not PHT, clearance compared to control dialysate. Continuous hemodialysis with albumin-supplemented dialysate may be a promising therapy to enhance dialytic clearance of selected highly protein-bound drugs.

In vitro clearance of dexmedetomidine in extracorporeal membrane oxygenation.

Dexmedetomidine (DMET) is a useful agent for sedation, both alone and in combination with other agents, in critically ill patients, including those on extracorporeal membrane oxygenation (ECMO) therapy. The drug is a clonidine-like derivative with an 8-fold greater specificity for the alpha 2-receptor while maintaining respiratory and cardiovascular stability. An in vitro ECMO circuit was used to study the effects of both “new” and “old” membrane oxygenators on the clearance of dexmedetomidine over the course of 24 hours. Once primed, the circuit was dosed with 840 μg of dexmedetomidine for a final concentration of 0.9 μg/ml. Serial samples, both pre- and post-oxygenator, were taken at 5, 60, 360, and 1440 minutes. Concentrations of the drug were expressed as a percentage of the original concentration remaining at each time point, both for new and old circuits. The new circuits were run at a standard flow for 24 hours, after which time the circuit was considered old and re-dosed with dexmedetomidine and the trial repeated. Results show that dexmedetomidine losses occur early in the circuits and then continue to decline. Initial losses in the first hour were 11+-65% and 59-73% pre- and post-oxygenator in the new circuit and 36-50% and 42-72% in the old circuit. The clearance of the drug through the membrane oxygenator exhibits no statistical difference between pre and post or new and old circuits. Dexmedetomidine can be expected to exhibit concentration changes during ECMO therapy. This effect appears to be more related to adsorption to the polyvinyl chloride (PVC) tubing rather than the membrane oxygenator. Dosage adjustments during dexmedetomidine administration during ECMO therapy may be warranted in order to maintain adequate serum concentrations and, hence, the desired degree of sedation.*(Lack of equilibrium)

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.

Safety and efficacy of recombinant activated factor VII for refractory hemorrhage in pediatric patients on extracorporeal membrane oxygenation: a single center review

Background: Medically refractory hemorrhage in patients on ECMO (extracorporeal membrane oxygenation) support can have catastrophic complications. Recombinant-Activated Factor VII (rFVIIa; NovoSeven®) may provide lifesaving hemostasis; however, there are reports of catastrophic thrombosis related to its administration. Objective: This review attempts to add safety and efficacy data to existing literature regarding the use of rFVIIa for refractory hemorrhage in pediatric patients on ECMO support. Design/Methods: A retrospective chart review was performed for all pediatric patients on ECMO who received rFVIIa for refractory hemorrhage from 2004 to 2009. Data was extracted for each refractory bleeding event, including patient blood loss and transfused blood products in the 6 hours before the first dose, between rFVIIa doses and in the 6 hours after the final dose. For purposes of data collection, a hemorrhagic event was defined as new onset hemorrhage or a hemorrhage occurring at least 12 hours after the most recent dose of rFVIIa. Results: In total, seven patients aged 1 month to 15 years received rFVIIa for 14 different hemorrhagic events. There was no significant difference in blood loss or blood product transfusion associated with rFVIIa administration. There was one patient-related and one ECMO-related complication temporally associated with rFVIIa administration: decreased ECMO circuit oxygenator efficiency and the development of an intra-gastric clot requiring surgical evacuation. Conclusion: These data suggest limited efficacy for rFVIIa use for refractory hemorrhage in pediatric patients on ECMO support. There were two non-catastrophic complications temporally associated with its administration.

A systematic approach to improving medication safety in a pediatric intensive care unit.

Safety and quality improvement are major issues in childrens hospitals. Improving pediatric medication safety often takes on a larger role in pediatric units than in adult units due to the larger size differences and dose ranges found in a pediatric intensive care unit. This article reviews the literature and our own experience at the CS Mott Childrens Hospital, University of Michigan, to improve medication safety. The issues identified include (1) an effective pediatric medication safety governance structure within a larger hospital, (2) practice standardization strategies for physicians, nurses, and pharmacists, (3) use of pharmacy technicians as unit medication managers, which reduces medication costs and decreases nursing time spent hunting for medications, and (4) methods to improve the safety culture in a pediatric intensive care unit.

A Case Series Describing the Use of Argatroban in Patients on Extracorporeal Circulation

Anticoagulation for extracorporeal life support (ECLS) is routinely achieved using heparin, which can be difficult in patients suspected of having heparin-induced thrombocytopenia. We describe a case series of five patients in which we used argatroban, a direct thrombin inhibitor, as an alternative to heparin for systemic anticoagulation during ECLS in patients suspected to have heparin-induced thrombocytopenia. Argatroban was used to achieve target systemic anticoagulation for activate clotting times between 210 and 230. Duration of argatroban use while on ECLS ranged from 6 to 184 hours. Argatroban dosage ranged from 0.2 to 3.5 &mgr;g/kg/min. Activated clotting times showed good agreement with aPTT. In conclusion, we illustrate that argatroban is a reasonable alternative to heparin anticoagulation for patients requiring ECLS.