Pharmacologic issues in the critically ill

Treatments of new-onset atrial fibrillation in critically ill patients: a systematic review with meta-analysis

BACKGROUND

New-onset atrial fibrillation (NOAF) is common in hospitalised patients with critical illness and associated with worse outcomes. Several interventions are available in the management of NOAF, but the overall effectiveness and safety of these interventions compared with placebo or no treatment are unknown.

METHODS

We conducted a systematic review with meta-analysis and trial sequential analysis (TSA) of randomised clinical trials (RCT) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses, the Cochrane Collaboration, and Grading of Recommendations Assessment, Development and Evaluation statements. We searched RCTs assessing any pharmacological and non-pharmacological treatment compared with placebo or no treatment in critically ill hospitalised patients with NOAF. The primary outcomes were all-cause mortality, adverse events, and health-related quality of life.

RESULTS

We included 16 trials (n = 1891) evaluating seven interventions. All trials were adjudicated 'some concerns' or 'high risk' of bias. The evidence is very uncertain for mortality (RR 0.53, 95% CI 0.03-8.30), adverse events (RR 1.28, 95% CI 0.85-1.92), and treatment efficacy i.e. rhythm control (RR 1.54, 95% CI 1.20-1.97; TSA-adjusted CI 0.56-4.53) between pharmacological treatment and placebo/no treatment (very low certainty evidence). There were no data for health-related quality of life or most of our secondary outcomes.

CONCLUSIONS

The existing data are insufficient to firmly conclude on effects of any intervention against NOAF on any outcome in hospitalised patients with critical illness. Randomised trials of the most frequently used interventions against NOAF are warranted in these patients.

Is Busulfan Clearance Different in Patients With Sickle Cell Disease? Let's Clear Up That Case With Some Controls

In busulfan-based conditioning regimen for hematopoietic stem cell transplantation in children, accurate a priori determination of the first dose is important because of its narrow therapeutic window. Sickle cell disease (SCD) influences pharmacokinetics of the commonly used drugs by affecting organs responsible for drug metabolism and elimination. This pharmacokinetics study assesses the influence of SCD on the metabolic pathway of busulfan that is mainly metabolized in the liver. In this retrospective cross-sectional case-control study, 16 patients with SCD were matched to 50 patients without SCD on known busulfan clearance's covariates (glutathione-S-transferase alpha1 polymorphisms, age, weight). Clearance of the first dose of busulfan was not significantly different independently of genetic or anthropometric factors in patients with or without SCD.

Treatment strategies for new-onset atrial fibrillation in critically ill patients: Protocol for a systematic review

BACKGROUND

New-onset atrial fibrillation is frequent in critically ill patients and associated with poorer outcomes in these patients. Numerous interventions are used for the management of new-onset atrial fibrillation, but it is unknown if these interventions improve patient-important outcomes as compared with placebo or no active intervention in adult critically ill patients.

METHODS/DESIGN

We will conduct a systematic review with meta-analysis and trial sequential analysis of randomized clinical trials assessing pharmacological and non-pharmacological interventions of new-onset atrial fibrillation as compared with placebo or no active intervention in adult critically ill patients. The primary outcomes are mortality, adverse events and health-related quality of life. We will search the following databases: MEDLINE, EMBASE, Cochrane Library, ClinicalTrials.gov, Science Citation Index and BIOSIS and follow the recommendations by the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We will evaluate the overall certainty of evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

DISCUSSION

New-onset atrial fibrillation is common in adult critically ill patients. However, the balance between the desirable and undesirable effects of pharmacological and non-pharmacological interventions is unknown. The outlined systematic review aims to provide updated data on this topic.

REGISTRATION

Submitted to PROSPERO (CRD42020187178 ). Status: accepted.

Pharmacokinetic and Pharmacodynamic Evaluation of Doripenem in Critically Ill Trauma Patients with Sepsis

BACKGROUND

Doripenem is approved by the Food and Drug Administration for the treatment of patients with complicated intra-abdominal infections and complicated urinary tract infections. While studies have described the pharmacokinetics/pharmacodynamics (PK/PD) of doripenem in the critically ill, no study has described the probability of target attainment profile among trauma patients with sepsis.

PATIENTS AND METHODS

This study was a prospective, open-label, pharmacokinetic study in the surgical intensive care unit (SICU) at Grady Health System. Thirty trauma patients with sepsis admitted to the SICU received doripenem 1 g infused over 4 hours every 8 hours for three doses. Blood samples were taken just before and after the third dose. A two-compartment model was fit to the data using non-parametric population PK modeling software. Embedded with the final PK model, a Monte Carlo Simulations (MCS) was performed to determine the PK/PD profile of doripenem 1 g, infused over 4 hours, every 8 hours after administration of the first and fourth doses.

RESULTS

Overall, the model fit the data well, and mean (standard deviation) clearance and volume of the central compartment were 16.9 (11.4) L/h and 28.5 (16.0) L, respectively. In the MCS analyses, doripenem 1 g, infused over 4 hours, administered every 8 hours, conferred >90% probabilities of achieving 30-50% time greater than the minimum inhibitory concentration (30-50% T>MIC) for MICs ≤2 mg/L after infusion of both the first and fourth doses. The MCS indicated that more intensive doripenem dosing schemes should be considered for organisms with MIC values in excess of 2 mg/L.

CONCLUSIONS

This is the first study to describe the doripenem PK/PD in critically ill patients with trauma. Among these patients, the MCS analyses suggest that current dosing strategies may be ineffective when the MIC value for the infecting pathogen is expected to be above 2 mg/L.

Clinical Pharmacology Studies in Critically Ill Children

Developmental and physiological changes in children contribute to variation in drug disposition with age. Additionally, critically ill children suffer from various life-threatening conditions that can lead to pathophysiological alterations that further affect pharmacokinetics (PK). Some factors that can alter PK in this patient population include variability in tissue distribution caused by protein binding changes and fluid shifts, altered drug elimination due to organ dysfunction, and use of medical interventions that can affect drug disposition (e.g., extracorporeal membrane oxygenation and continuous renal replacement therapy). Performing clinical studies in critically ill children is challenging because there is large inter-subject variability in the severity and time course of organ dysfunction; some critical illnesses are rare, which can affect subject enrollment; and critically ill children usually have multiple organ failure, necessitating careful selection of a study design. As a result, drug dosing in critically ill children is often based on extrapolations from adults or non-critically ill children. Dedicated clinical studies in critically ill children are urgently needed to identify optimal dosing of drugs in this vulnerable population. This review will summarize the effect of critical illness on pediatric PK, the challenges associated with performing studies in this vulnerable subpopulation, and the clinical PK studies performed to date for commonly used drugs.

Pharmacokinetic considerations and recommendations in palliative care, with focus on morphine, midazolam and haloperidol

INTRODUCTION

A variety of medications are used for symptom control in palliative care, such as morphine, midazolam and haloperidol. The pharmacokinetics of these drugs may be altered in these patients as a result of physiological changes that occur at the end stage of life.

AREAS COVERED

This review gives an overview of how the pharmacokinetics in terminally ill patients may differ from the average population and discusses the effect of terminal illness on each of the four pharmacokinetic processes absorption, distribution, metabolism, and elimination. Specific considerations are also given for three commonly prescribed drugs in palliative care: morphine, midazolam and haloperidol).

EXPERT OPINION

The pharmacokinetics of drugs in terminally ill patients can be complex and limited evidence exists on guided drug use in this population. To improve the quality of life of these patients, more knowledge and more pharmacokinetic/pharmacodynamics studies in terminally ill patients are needed to develop individualised dosing guidelines. Until then knowledge of pharmacokinetics and the physiological changes that occur in the final days of life can provide a base for dosing adjustments that will improve the quality of life of terminally ill patients. As the interaction of drugs with the physiology of dying is complex, pharmacological treatment is probably best assessed in a multi-disciplinary setting and the advice of a pharmacist, or clinical pharmacologist, is highly recommended.

The prevalence of long QT interval in post-operative intensive care unit patients

The severity of patient illnesses and medication complexity in post-operative critically ill patients increase the risk for a prolonged QT interval. We determined the prevalence of prolonged QTc in surgical intensive care unit (SICU) patients. We performed a prospective cross-sectional study over a 15-month period at a major academic center. SICU pre-admission and admission EKGs, patient demographics, and laboratory values were analyzed. QTc was evaluated as both a continuous and dichotomous outcome (prolonged QTc > 440 ms). 281 patients were included in the study: 92 % (n = 257) post-operative and 8 % (n = 24) non-operative. On pre-admission EKGs, 32 % of the post-operative group and 42 % of the non-operative group had prolonged QTc (p = 0.25); on post-admission EKGs, 67 % of the post-operative group but only 33 % of the non-operative group had prolonged QTc (p < 0.01). The average change in QTc in the post-operative group was +30.7 ms, as compared to +2 ms in the non-operative group (p < 0.01). On multivariable adjustment for long QTc as a dichotomous outcome, pre-admission prolonged QTc (OR 3.93, CI 1.93-8.00) and having had an operative procedure (OR 4.04, CI 1.67-9.83) were associated with developing prolonged QTc. For QTc as a continuous outcome, intra-operative beta-blocker use was associated with a statistically-significant decrease in QTc duration. None of the patients developed a lethal arrhythmia in the ICU. Prolonged QTc is common among post-operative SICU patients (67 %), however lethal arrhythmias are uncommon. The operative experience increases the risk for long QTc.

IV enoxaparin in pediatric and cardiac ICU patients

OBJECTIVES

To report our experience with the use of IV enoxaparin in neonatal and pediatric patients in the ICU.

DESIGN

We performed a case control from January 1, 2009, to June 30, 2012, comparing patients that received IV enoxaparin to controls that received subcutaneous enoxaparin. Cases were matched to controls in a 1:2 manner. IV enoxaparin doses were infused over 30 minutes and anti-Factor Xa levels were drawn 4 hours after the start of the IV infusion or 4 hours after a subcutaneous dose.

SETTING

The pediatric and cardiac ICUs of a tertiary/quaternary, free-standing, academic children's hospital.

PATIENTS

Forty-five neonatal and pediatric patients receiving prophylactic or therapeutic enoxaparin.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Fifteen cases and 30 controls were included. Of 15 patients, 13 received IV enoxaparin for treatment and two received IV enoxaparin for prophylaxis as compared with 25 of 30 controls receiving subcutaneous enoxaparin for treatment and five receiving subcutaneous enoxaparin for prophylaxis. The ages for the cases ranged from 21 days to 16 years with a median weight of 5 kg, and the ages for controls ranged from 10 days to 23 years with a median weight of 31 kg. The median duration of IV therapy was 11 days (range, 1-120 d) and the median duration for subcutaneous therapy was 15 days (range, 3-85 d). The mean initial IV dose was 1.14 ± 0.38 mg/kg/dose q12h, and the mean initial subcutaneous dose was 0.85 ± 0.2 mg/kg/dose subcutaneous q12h (p = 0.003). The mean therapeutic IV dose was 1.31 ± 0.52 mg/kg/dose q12h, and the mean therapeutic subcutaneous dose was 0.9 ± 0.3 mg/kg/dose q12h (p = 0.016). There were no adverse events reported related to bleeding, thrombosis, or hypersensitivity in any of the cases or controls evaluated.

CONCLUSION

The pharmacodynamics of a 30-minute IV enoxaparin infusion was found to produce therapeutic 4 hour anti-Factor Xa levels similar to subcutaneous doses. Although this was a small study, there were no adverse events, suggesting the safety profile of IV enoxaparin may be similar to subcutaneous dosing with the added benefit of less pain associated with IV dosing. These findings suggest that IV enoxaparin may be a viable option for anticoagulating critically ill children and its use warrants further study.

Newer anticoagulants in critically ill patients

Critically ill patients are at increased risk for development of thrombosis. In addition, thrombosis is often unrecognized in this population. Furthermore, these patients are particularly susceptible to bleeding complications from anticoagulants. Herein the authors review the pharmacology, data from clinical trials, management of bleeding complications, and perioperative use of these agents in the intensive care unit population. Well-designed clinical trials are needed to improve our understanding of the safety and efficacy of these newer agents in critically ill patients.

Alterations of drug metabolism in critically ill animals

Critically ill animals are by nature a diverse group with multiple presenting complaints and differing levels of organ function. Pharmacokinetics and pharmacodynamics of administered compounds are affected both by the disease processes and by the interventions of the treating veterinarian. Polypharmacy is not an exception but a rule within this caseload. Basic principles of pharmacology allow for safe and effective administration of pharmaceuticals, especially in the critically ill. Future research evaluating the pharmacokinetics and pharmacodynamics of drugs important in the management of critically ill animals is imperative, and will allow evidence-based dose modification.

Case Report: Persistent Elevation in Creatine Phosphokinase Associated with High-Dose Daptomycin Therapy

Objective

To report a persistent elevation in creatine phosphokinase (CPK) associated with high-dose daptomycin therapy that did not resolve following discontinuation of daptomycin.

Summary

A 34-year-old male with HIV/AIDS and stage IV Burkitt lymphoma was admitted for pain management. The patient's initial hospital course was complicated by left brachial deep vein thrombosis (DVT), Clostridium difficile colitis, and pancytopenia. The patient later developed severe sepsis and septic shock secondary to methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), Candida albicans, and Escherichia coli infection. High-dose daptomycin (12 mg/kg) was initiated to treat MRSA and VRE bacteremia. The patient's baseline CPK was 118 U/L, which increased to 327 U/L following 2 days of therapy. The patient's CPK continued to increase to 1648 U/L on day 10 of daptomycin, thereby necessitating a discontinuation of daptomycin and the initiation of linezolid. Six days after discontinuation of therapy, the patient's CPK remained elevated at 1940 U/L.

Discussion

A Naranjo scale score of 6 was calculated, indicating that daptomycin was the probable cause for the increase in CPK. Although daptomycin is known to cause elevations in CPK, there are limited published data describing this adverse event with high-dose daptomycin therapy.

Conclusion

High-dose daptomycin is becoming more frequently used in clinical practice, so clinicians should monitor for and report any adverse events associated with this dosing strategy.

Grading the severity of drug-drug interactions in the intensive care unit: a comparison between clinician assessment and proprietary database severity rankings

BACKGROUND

Computerized provider order entry with decision support software offers an opportunity to identify and prevent medication-related errors, including drug-drug interactions (DDIs), through alerting mechanisms. However, the number of alerts generated can overwhelm and lead to "alert fatigue." A DDI alert system based on severity rankings has been shown to reduce alert fatigue; however, the best method to populate this type of database is unclear.

OBJECTIVE

To compare the severity ranking of proprietary databases to clinician assessment for DDIs occurring in critically ill patients.

METHODS

This observational, prospective study was conducted over 8 weeks in the cardiac and cardiothoracic intensive care unit. Medication profiles of patients were screened for the presence of DDIs and a severity evaluation was conducted using rankings of proprietary databases and clinician opinion using a DDI severity assessment tool. The primary outcome measure was the number of DDIs considered severe by both evaluation methods.

RESULTS

A total of 1150 DDIs were identified after 400 patient medication profiles were evaluated. Of these, 458 were unique drug pairs. Overall, 7.4% (34/458) were considered a severe interaction based upon proprietary database ratings. The assessment by clinicians ranked 6.6% (30/458) of the unique DDIs as severe. Only 3 interactions, atazanavir-simvastatin, atazanavir-tenofovir, and aspirin-warfarin, were considered severe by both evaluation methods.

CONCLUSIONS

Since proprietary databases and clinician assessment of severe DDIs do not agree, developing a knowledge base for a DDI alert system likely requires proprietary database information in conjunction with clinical opinion.

Bioavailability of fondaparinux to critically ill patients

INTRODUCTION

Venous thromboembolism is a common problem in the intensive care unit (ICU). To decrease its incidence, prophylactic pharmacologic interventions are part of the ICU routine. However, common ICU conditions may impair the bioavailability of subcutaneously administered agents. The present study evaluates the bioavailability of prophylactic subcutaneous fondaparinux to critically ill patients.

PURPOSE

The purpose of the study was to evaluate vasopressor effect on the bioavailability of subcutaneously administered fondaparinux.

MATERIALS AND METHODS

A 2-center, prospective, observational study was performed. Forty patients were enrolled and divided into 2 groups depending on their vasopressor requirements. All subjects were critically ill patients admitted to a medical ICU for an anticipated stay of more than 72 hours.

INTERVENTIONS

All patients received subcutaneous fondaparinux 2.5 mg/d, and serum anti-Xa factor was serially assessed during the first 100 hours of medical ICU stay.

RESULTS

Therapeutic anti-factor Xa levels among patients receiving vasopressors were observed. In hemodynamically normal patients, subtherapeutic concentrations were detected during the first 48 hours of fondaparinux administration.

CONCLUSIONS

Vasopressor therapy does not appear to affect fondaparinux bioavailability or to reduce anti-factor Xa levels. Subtherapeutic concentrations were detected during the first 48 hours of fondaparinux administration in hemodynamically stable patients. The clinical significance of reduced levels during the first 2 days of fondaparinux administration remains unknown.

Genetic predisposition to adverse drug reactions in the intensive care unit

Adverse drug reactions are a significant public health problem that leads to mortality, hospital admissions, an increased length of stay, increasing healthcare costs, and withdrawal of drugs from market. Intensive care unit patients are particularly vulnerable and are at an elevated risk. Critical care practitioners, regulatory agencies, and the pharmaceutical industry aggressively seek biomarkers to mitigate patient risk. The rapidly expanding field of pharmacogenomics focuses on the genetic contributions to the variability in drug response. Polymorphisms may explain why some groups of patients have the expected response to pharmacotherapy whereas others experience adverse drug reactions. Historically, genetic association studies have focused on characterizing the effects of variation in drug metabolizing enzymes on pharmacokinetics. Recent work has investigated drug transporters and the variants of genes encoding drug targets, both intended and unintended, that comprise pharmacodynamics. This has led to an appreciation of the role that genetics plays in adverse drug reactions that are either predictable extensions of a drug's known therapeutic effect or idiosyncratic.This review presents the evidence for a genetic predisposition to adverse drug reactions, focusing on gene variants producing alterations in drug pharmacokinetics and pharmacodynamics in intensive care unit patients. Genetic biomarkers with the strongest associations to adverse drug reaction risk in the intensive care unit are presented along with the medications involved. Variant genotypes and phenotypes, allelic frequencies in different populations, and clinical studies are discussed. The article also presents the current recommendations for pharmacogenetic testing in clinical practice and explores the drug, patient, research study design, regulatory, and practical issues that presently limit more widespread implementation.

Common drug interactions leading to adverse drug events in the intensive care unit: management and pharmacokinetic considerations

Critically ill patients are predisposed to drug interactions because of the complexity of the drug regimens they receive in the intensive care setting. Drugs may affect the absorption, distribution, metabolism, and/or elimination of an object drug and consequently alter the intended pharmacologic response and potentially lead to an adverse event. Certain disease states that afflict critically ill patients may also amplify an intended pharmacologic response and potentially result in an unintended effect. A team approach is important to identify, prevent, and address drug interactions in the intensive care setting and optimize patient outcomes.

Enoxaparin versus unfractioned heparin as anticoagulant for continuous venovenous hemodialysis: a randomized open-label trial

AIM

In this study we aimed to compare the efficacy and safety of enoxaparin with unfractioned heparin (UFH) as anticoagulant for continuous venovenous hemodialysis (CVVHD).

METHODS

An open-label randomized controlled trial was carried out in an intensive care unit (ICU) where 40 patients with acute renal failure (ARF) who needed continuous renal replacement therapy were randomized to receive UFH (n=21) or enoxaparin (n=19). Coagulation parameters were evaluated, and antithrombotic activity of UFH was measured by activated partial thromboplastin time (aPTT) and for enoxaparin by anti-factor Xa activity. Primary outcomes were thrombosis of the extracorporeal circuit and bleeding, classified as major or minor.

RESULTS

Minor bleeding episodes were observed only in patients anticoagulated with enoxaparin (26 vs. 0%, p=0.018). Comparing patients with or without bleeding after 24 hours of therapy, the level of anticoagulation tended to be higher (anti-factor Xa: 1.62 vs. 1.13 IU/mL, p=0.09) and the platelet count to be lower [107+/-53 vs. 229+/-84 (x10(3)/microL), p=0.09] in patients who bled, but without statistical difference. Filter life span of enoxaparin and UFH groups was similar (43+/-15 vs. 52+/-18 hr, p=0.10), as well as the proportion of circuit clotting.

CONCLUSION

Weight-unadjusted enoxaparin in patients with ARF in CVVHD was associated with an increased rate of bleeding, a finding that addresses the need to adjust drug dose and to monitor anti-factor Xa activity during dialysis. No benefit to prolong dialysis circuit survival was found with enoxaparin. In patients who do not present contraindication for systemic anticoagulation, UFH remains an effective and low-cost option.

Argatroban therapy for heparin-induced thrombocytopenia in ICU patients with multiple organ dysfunction syndrome: a retrospective study

Introduction

Heparin-induced thrombocytopenia (HIT) is a serious, prothrombotic, immune-mediated adverse reaction triggered by heparin therapy. When HIT is diagnosed or suspected, heparins should be discontinued, and an alternative, fast-acting, parenteral, nonheparin anticoagulation such as argatroban should be initiated. Limited and inconsistent data exist about dosing of argatroban in intensive care unit (ICU) patients with critical illnesses.

Methods

Retrospective analysis of 12 ICU patients with multiple organ dysfunction syndrome (MODS) treated with argatroban for suspected or diagnosed HIT.

Results

The 12 ICU patients with a mean platelet count of 46,000 ± 30,310 had a mean APACHE II score of 26.7 ± 7.8 on ICU admission and a mean SAPS II score of 61.5 ± 16.3 on the first day of argatroban administration. A mean argatroban starting dose of 0.32 ± 0.25 μg/kg/min (min, 0.04; max, 0.83) was used to achieve activated partial thromboplastin times (aPTTs) >60 sec or aPTTs of 1.5 to 3 times the baseline aPTT. Adjustment to aPTT required dose reduction in six (50%) patients. Patients were treated for a mean of 5.5 ± 3.3 days. The final mean dose in these critically ill patients was 0.24 ± 0.16 μg/kg/min, which is about one eighth of the usually recommended dose and even markedly lower than the previously suggested dose for critically ill ICU patients. In all patients, desired levels of anticoagulation were achieved. The mean argatroban dose was significantly lower in patients with hepatic insufficiency compared with patients without hepatic impairment (0.10 ± 0.06 μg/kg/min versus 0.31 ± 0.14 μg/kg/min; P = 0.026). The mean argatroban dose was significantly correlated with serum bilirubin (r = -0.739; P = 0.006).

Conclusions

ICU Patients with MODS and HIT can be effectively treated with argatroban. A decrease in the initial dosage is mandatory in this patient population. Further studies are needed to investigate argatroban elimination and dosage adjustments for critically ill patients.

Mini-series: II. clinical aspects. clinically relevant CYP450-mediated drug interactions in the ICU

BACKGROUND

In the critically ill, multiple drug therapies for acute and chronic conditions are often used at the same time and adverse drug events occur frequently. Many pharmacological and disease-related factors, e.g. altered renal and hepatic function, catecholamine-related circulatory changes, altered drug volume of distribution, enteral versus parenteral feeding and morbid obesity, along with concomitant multiple drug regimens may account for the wide inter-individual variability in drug exposure and response in critically ill patients and for the high risk for drug-drug interactions to occur. The practicing intensivist must remain aware of the major mechanisms for drug-drug interactions, among which the drug-metabolizing enzyme inhibitory or induction potential of associated chemical entities are paramount. Metabolism-based drug-drug interactions are largely due to changes in levels of drug-metabolizing enzymes caused by one drug, leading to changes in the systemic exposure clearance of another. Among the numerous drug-metabolizing enzymes identified to date, the activity of cytochrome P450s (CYP450) is a critical determinant of drug clearance and appears to be involved in the mechanism of numerous clinically relevant drug-drug interactions observed in critically ill patients.

DISCUSSION

This manuscript will cover a practical overview of clinically relevant CYP450-mediated drug-drug interactions. Medications frequently used in the intensive care unit such as benzodiazepines, immunosuppressive agents, opioid analgesics, certain anticonvulsants, the azoles and macrolides have the potential to interact with CYP450-mediated metabolism and may lead to toxicity or therapeutic failure.

Experience with intravenous enoxaparin in critically ill infants and children

OBJECTIVE

Subcutaneous administration of enoxaparin is often difficult in special populations, such as premature infants and critically ill children with severe edema. The difficulty achieving adequate anticoagulation in these patients has led to the employment of intravenous enoxaparin in some cases. However, little pharmacodynamic data are available for determining the appropriate dosing and monitoring (by anti-Factor Xa levels) of intravenous enoxaparin. The objective of this study is to report our experience with the use of intravenous enoxaparin in pediatric patients in the intensive care unit.

DESIGN

Retrospective review of medical records.

SETTING

Single institution pediatric intensive care unit.

PATIENTS

All pediatric patients receiving intravenous enoxaparin in the pediatric intensive care unit at Children's Medical Center Dallas between April 1, 2005 and March 31, 2006 were identified using hospital pharmacy records.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Seven patients were identified as having received intravenous enoxaparin while in the intensive care unit. Higher anti-Xa levels were found at 1-2 hrs after administration of intravenous enoxaparin rather than at the 4-6 hrs documented with subcutaneous administration and these levels decreased substantially 6-8 hrs after an intravenous dose. Mean therapeutic dose for children <1 yr of age was 2.40 mg/kg/dose (+/-sd 0.58). For children > or =1 yr of age, the mean therapeutic dose was 1.11 mg/kg/dose (+/-sd 0.13). The mean prophylactic dose for the two children was 0.93 mg/kg/dose (+/-sd 0.43).

CONCLUSIONS

Our data show that the pharmacodynamics of intravenous administration is different from subcutaneous administration and deserves further study.

Treating seizures in renal and hepatic failure

INTRODUCTION: Renal and hepatic diseases cause seizures and patients with epilepsy may suffer from such diseases which change antiepileptic drugs (AEDs) metabolism. OBJECTIVES: To revise how seizures may be caused by metabolic disturbances due to renal or hepatic diseases, by their treatment or by comorbidities and how AEDs choice might be influenced by these conditions. RESULTS: Seizures arise in renal failure due to toxins accumulation and to complications like sepsis, hemorrhage, malignant hypertension, pH and hydroelectrolytic disturbances. Hemodialysis leads to acute dysequilibrium syndrome and to dementia. Peritoneal dialysis may cause hyperosmolar non-ketotic coma. Post-renal transplant immunosupression is neurotoxic and cause posterior leukoencephalopathy, cerebral lymphoma and infections. Some antibiotics decrease convulsive thresholds, risking status epilepticus. Most commonly used AEDs in uremia are benzodiazepines, ethosuximide, phenytoin and phenobarbital. When treating epilepsy in renal failure, the choice of AED remains linked to seizure type, but doses should be adjusted especially in the case of hydrosoluble, low-molecular-weight, low-protein-bound, low apparent distribution volume AEDs. Hepatic failure leads to encephalopathy and seizures treated by ammonium levels and intestinal bacterial activity reductions, reversal of cerebral edema and intracranial hypertension. Phenytoin and benzodiazepines are usually ineffective. Seizures caused by post-hepatic immunosupression can be treated by phenytoin or levetiracetam. Seizures in Wilson's disease may result from D-penicillamine dependent piridoxine deficiency. Porphyria seizures may be treated with gabapentin, oxcarbazepine and levetiracetam. Hepatic disease changes AEDs pharmacokinetics and needs doses readjustments. Little liver-metabolized AEDs as gabapentin, oxcarbazepine and levetiracetam are theoretically more adequate. CONCLUSIONS: Efficient seizures treatment in renal and hepatic diseases requires adequate diagnosis of these disturbances and their comorbidities besides good knowledge on AEDs metabolism, their pharmacokinetic changes in such diseases, careful use of concomitant medications and AEDs serum levels monitoring.

Pharmacokinetics and pharmacodynamics in the critically ill child

An understanding of pharmacokinetics and pharmacodynamics can allow for a rational approach to prescribing medications for critically ill children. Absorption, distribution, metabolism, elimination, and the response to medications are affected by age and disease state. Various medications are used in the care of critically ill children. Many medications are prescribed for children based on dosing guidance from adult studies, however. Care providers must be cautious of the high risk for drug interactions and adverse reactions in the intensive care setting.

Anti-Xa activity after subcutaneous administration of dalteparin in ICU patients with and without subcutaneous oedema: a pilot study

INTRODUCTION

Intensive care unit (ICU) patients often suffer from subcutaneous oedema, due to administration of large fluid volumes and the underlying pathophysiological condition. It is unknown whether the presence of subcutaneous oedema impairs the absorption of dalteparin, a low molecular weight heparin, when it is given by subcutaneous administration for venous thromboembolism prophylaxis. The objective of this study is to compare the anti-Xa activity of dalteparin after subcutaneous administration in ICU patients with and without subcutaneous oedema.

METHODS

This non-randomized open parallel group follow-up pilot study was conducted in two mixed medical-surgical intensive care units at two teaching hospitals. Seven ICU patients with subcutaneous oedema (index group) and seven ICU patients without subcutaneous oedema (reference group) were studied. Anti-Xa activity was determined at 0, 3, 4, 6, 8, 12 and 24 hours after subcutaneous administration of 2,500 IU dalteparin. Plasma concentrations of factor anti-Xa activity were measured using a chromogenic factor Xa inhibition assay.

RESULTS

The characteristics of the index group were: age, 58 years; male/female ratio, 5/2; body mass index at admission, 23.4 kg/m2 (at study day, 30.6 kg/m2). The characteristics of the reference group were: age, 49 years; male/female ratio, 6/1; body mass index at admission, 24.8 kg/m2 (at study day, 25.0 kg/m2). In the index group, creatinine clearance was lower compared to the reference group (71 versus 131 ml/minute, p = 0.003). Sequential organ failure assessment score did not differ between index and reference groups (4 versus 5). Mean arterial pressure was comparable between index and reference groups (91 versus 95 mmHg) and within the normal range. The mean Cmax value was not different between ICU patients with and without subcutaneous oedema (0.15 +/- 0.02 versus 0.14 +/- 0.02 IU/ml, p = 0.34). In the index group, the mean AUC(0-24 h) value was slightly higher compared with the reference group (1.50 +/- 0.31 versus 1.15 +/- 0.25 h.IU/ml, p = 0.31). This difference was not significant.

CONCLUSION

In this pilot study, there was no clinically relevant difference in anti-Xa activity after subcutaneous administration of 2,500 IU dalteparin for venous thromboembolism prophylaxis between ICU patients with and without subcutaneous oedema. Critically ill patients seem to have lower anti-Xa activity levels than healthy volunteers.

Pharmacology of palliative medicine

OBJECTIVE

To describe the concepts of both pharmacokinetics and pharmacodynamics and how it applies to palliative medicine.

DATA SOURCES

Research and review articles and textbooks.

CONCLUSION

Most patients who have an illness that requires palliation are elderly, have co-morbid conditions, and are on many medications. Both age and disease can alter the way drugs are handled by the body (pharmacokinetics) and how they affect the body (pharmacodynamics).

IMPLICATIONS FOR NURSING PRACTICE

The oncology nurse, armed with the correct knowledge about medications, can have an important inmpact on improving the patient's care, safety, and quality of life.