Evaluation of furosemide regimens in neonates treated with extracorporeal membrane oxygenation

Micellar Encapsulation of Propofol Reduces its Adsorption on Extracorporeal Membrane Oxygenator (ECMO) Circuit

Extracorporeal membrane oxygenation (ECMO) is a life-saving cardiopulmonary bypass device used on critically ill patients with refractory heart and lung failure. Patients supported with ECMO receive numerous drugs to treat critical illnesses and the underlying diseases. Unfortunately, most drugs prescribed to patients on ECMO lack accurate dosing information. Dosing can be variable in this patient population because the ECMO circuit components can adsorb drugs and affect drug exposure substantially. Propofol is a widely used anesthetic in ECMO patients and is known to have high adsorption rates in ECMO circuits due to its high hydrophobicity. In an attempt to reduce adsorption, we encapsulated propofol with Poloxamer 407 (Polyethylene-Polypropylene Glycol). Size and polydispersity index (PDI) were characterized using dynamic light scattering. Encapsulation efficiency was analyzed using High performance liquid chromatography. Cytocompatibility of micelles was analyzed against human macrophages and the formulation was finally injected in an ex-vivo ECMO circuit to determine the adsorption of propofol. Size and PDI of micellar propofol were 25.5 ± 0.8 nm and 0.08 ± 0.01, respectively. Encapsulation efficiency of the drug was 96.1 ± 1.3%. Micellar propofol demonstrated colloidal stability at physiological temperature for a period of 7 days, and was cytocompatible with human macrophages. Micellar propofol demonstrated a significant reduction in adsorption of propofol in the ECMO circuit at earlier time points compared to free propofol (Diprivan®). We observed 97 ± 2% recovery of the propofol from the micellar formulation after an infusion. These results demonstrate the potential of micellar propofol to reduce drug adsorption to ECMO circuit.

Cefepime Extraction by Extracorporeal Life Support Circuits

Extracorporeal life support (ECLS) devices are lifesaving for critically ill patients with multi-organ dysfunction. Despite this, patients supported with ECLS are at high risk for ECLS-related complications, including nosocomial infections, and mortality rates are high in this patient population. The high mortality rates are suspected to be, in part, a result of significantly altered drug disposition by the ECLS circuit, resulting in suboptimal antimicrobial dosing. Cefepime is commonly used in critically ill patients with serious infections. Cefepime dosing is not routinely guided by therapeutic drug monitoring and treatment success is dependent upon the percentage of time of the dosing interval that the drug concentration remains above the minimum inhibitory concentration of the organism. This ex vivo study measured the extraction of cefepime by continuous renal replacement therapy (CRRT) and extracorporeal membrane oxygenation (ECMO) circuits. Cefepime was studied in four closed-loop CRRT circuit configurations and a single closed-loop ECMO circuit configuration. Circuits were primed with a physiologic human blood-plasma mixture and the drug was dosed to achieve therapeutic concentrations. Serial blood samples were collected over time and concentrations were quantified using validated assays. In ex vivo CRRT experiments, cefepime was rapidly cleared by dialysis, hemofiltration, and hemodiafiltration, with greater than 96% cefepime eliminated from the circuit by 2 hours. In the ECMO circuits, the mean recovery of cefepime was similar in both circuit and standard control. Mean (standard deviation) recovery of cefepime in the ECMO circuits (n = 6) was 39.2% (8.0) at 24 hours. Mean recovery in the standard control (n = 3) at 24 hours was 52.2% (1.5). Cefepime is rapidly cleared by dialysis, hemofiltration, and hemodiafiltration in the CRRT circuit but minimally adsorbed by either the CRRT or ECMO circuits. Dosing adjustments are needed for patients supported with CRRT.

Fluid Homeostasis and Diuretic Therapy in the Neonate

Understanding physiologic water balance and homeostasis mechanisms in the neonate is critical for clinicians in the NICU as pathologic fluid accumulation increases the risk for morbidity and mortality. In addition, once this process occurs, treatment is limited. In this review, we will cover fluid homeostasis in the neonate, explain the implications of prematurity on this process, discuss the complexity of fluid accumulation and the development of fluid overload, identify mitigation strategies, and review treatment options.

Amiodarone Extraction by the Extracorporeal Membrane Oxygenation Circuit

Amiodarone is an anti-arrhythmic agent that is frequently used to treat tachycardias in critically ill adults and children. Because of physicochemical properties of amiodarone, extracorporeal membrane oxygenation (ECMO) circuits are expected to extract amiodarone from circulation, increasing the risk of therapeutic failure. The present study seeks to determine amiodarone extraction by the ECMO circuit. Amiodarone was administered to three ex vivo circuit configurations (n = 3 per configuration) to determine the effect of each circuit component on drug extraction. The circuits were primed with human blood; standard amiodarone doses were administered; and serial samples were collected over 24 hours. Additional circuits were primed with crystalloid fluid to analyze the effect of blood on extraction and to investigate circuit saturation by drug. The crystalloid circuits were dosed multiple times over 72 hours, including a massive dose at 48 hours. For both setups, the flow was set to 1 L/min. Drug was added to separate tubes containing the prime solution to serve as controls. Drug concentrations were quantified with a validated assay, and drug recovery was calculated for each sample. Mean recovery for the circuits and controls were compared to correct for drug degradation over time. Amiodarone was heavily extracted by all ECMO circuit configurations. Eight hours after dosing, mean recovery in the blood prime circuits was 13.5-22.1%. In the crystalloid prime circuits, drug recovery decreased even more rapidly, with a mean recovery of 22.0% at 30 minutes. Similarly, drug recovery decreased more quickly in the crystalloid prime controls than in the blood prime controls. Saturation was not achieved in the crystalloid prime circuits, as final amiodarone concentrations were at the lower limit of quantification. The results suggest that amiodarone is rapidly extracted by the ECMO circuit and that saturation is not achieved by standard doses. In vivo circuit extraction may cause decreased drug exposure.

Continuous intravenous sildenafil as an early treatment in neonates with congenital diaphragmatic hernia

BACKGROUND

Pulmonary hypertension (PH) is an important contributor of morbidity and mortality in infants with congenital diaphragmatic hernia (CDH). Treatment options are limited, but sildenafil might improve oxygenation and PH in neonates with CDH.

OBJECTIVE

Aim of this study is to assess effects of intravenous sildenafil on oxygenation and PH in neonates with CDH.

METHODS

A retrospective chart review was performed in all neonates with CDH born in our institution between September 2012 and December 2014. Indication for sildenafil was an OI > 15, PH > 2/3 systemic pressure, or a difference in pre- and postductal oxygen saturation (≥8%). A sildenafil bolus was administered followed by a maintenance infusion of 1.6 mg/kg/d. Primary outcome was improved oxygenation after starting sildenafil. Patients were compared according to improvement in oxygenation (responder vs non-responder).

RESULTS

A total of 26 of 44 neonates were treated with intravenous sildenafil and in all sildenafil were initiated within the first 24 h of life (median age 3.1 h). Improved oxygenation was observed in 11 infants (42.3%). Among the 15 non-responders (57.6%) ECMO was started in 13 and two infants died without ECMO. Vasopressor support increased significantly during the first hours after commencing sildenafil in responders and non-responders. Echocardiographic indices demonstrated an effect on pulmonary arterial pressure within the first 24 h after starting sildenafil.

CONCLUSIONS

Treatment of neonates with intravenous sildenafil during the first day of life was associated with acute improvement in oxygenation in more than 40% of patients. However, a significant increase in vasopressor support was observed.

Optimising drug dosing in patients receiving extracorporeal membrane oxygenation

Optimal pharmacological management during extracorporeal membrane oxygenation (ECMO) involves more than administering drugs to reverse underlying disease. ECMO is a complex therapy that should be administered in a goal-directed manner to achieve therapeutic endpoints that allow reversal of disease and ECMO wean, minimisation of complications (treatment of complications when they do occur), early interruption of sedation and rehabilitation, maximising patient comfort and minimising risks of delirium. ECMO can alter both the pharmacokinetics (PK) and pharmacodynamics (PD) of administered drugs and our understanding of these alterations is still evolving. Based on available data it appears that modern ECMO circuitry probably has a less significant impact on PK when compared with critical illness itself. However, these findings need further confirmation in clinical population PK studies and such studies are underway. The altered PD associated with ECMO is less understood and more research is indicated. Until robust dosing guidelines become available, clinicians will have to rely on the principles of drug dosing in critically ill and known PK alterations induced by ECMO itself. This article summarises the PK alterations and makes preliminary recommendations on possible dosing approaches.

Antifungal Extraction by the Extracorporeal Membrane Oxygenation Circuit

Invasive candidiasis is common and often fatal in patients supported with extracorporeal membrane oxygenation (ECMO), and treatment relies on optimal antifungal dosing. The ECMO circuit can extract drug and decrease drug exposure, placing the patient at risk of therapeutic failure. This ex vivo study determined the extraction of antifungal drugs by the ECMO circuit. Fluconazole and micafungin were studied separately in three closed-loop circuit configurations to isolate the impact of the oxygenator, hemofilter, and tubing on circuit extraction. Each circuit was primed with human blood, and flow was set to 1 L/min. Drug was dosed to achieve therapeutic concentrations. Each antifungal was added to a separate tube of blood to serve as a control. Serial blood samples were collected over 24 hours and concentrations were quantified with a validated assay. Drug recovery was calculated at each time point: (C t /C i )*100, with C t and C i the concentrations at time = t and 1 minute, respectively. After 24 hours of recirculation, mean recovery of fluconazole in the ECMO circuit (95-98%) and controls (101%) was high. In contrast, mean recovery of micafungin was dependent on the time and circuit configuration. Recovery at 4 hours was only 46% when a hemofilter was in-line but was much higher when the hemofilter was removed (91%). By 24 hours, however, micafungin recovery was low in all circuit configurations (26-43%), regardless of the presence of a hemofilter, as well as in the controls (57%). In conclusion, these results suggest that micafungin is extracted by the ECMO circuit, which may result in decreased drug exposure in vivo.

Pharmacotherapy during pediatric extracorporeal membrane oxygenation: a review

INTRODUCTION

Pediatric critical illness and associated alterations in organ function can change drug pharmacokinetics (PK). Extracorporeal membrane oxygenation (ECMO), a life-saving therapy for severe cardiac and/or respiratory failure, causes additional PK alterations that affect drug disposition.

AREAS COVERED

The purposes of this review are to discuss the PK changes that occur during ECMO, the associated therapeutic implications, and to review PK literature relevant to pediatric ECMO. We discuss various classes of drugs commonly used for pediatric patients on ECMO, including sedatives, analgesics, antimicrobials and cardiovascular drugs. Finally, we discuss future areas of research and recommend strategies for future pediatric ECMO pharmacologic investigations.

EXPERT OPINION

Clinicians caring for pediatric patients treated with ECMO must have an understanding of PK alterations that could lead to either therapeutic failures or increased drug toxicity during this life-saving therapy. Limited data currently exist for optimal drug dosing in pediatric populations who are treated with ECMO. While there are clear challenges to conducting and analyzing data associated with clinical pharmacokinetic-pharmacodynamic studies of children on ECMO, we present techniques to address these challenges. Improved understanding of the physiology and drug disposition during ECMO combined with PK-PD modeling will allow for more adaptable and individualized dosing schemes.

Peritoneal dialysis: an alternative modality of fluid removal in neonates requiring extracorporeal membrane oxygenation after cardiac surgery

Extracorporeal membrane oxygenation (ECMO) is a lifesaving therapy for patients with cardiopulmonary failure after cardiac surgery. Fluid overload (FO) is associated with increased morbidity and mortality in this population. We present our experience using peritoneal dialysis (PD) as an adjunct for fluid removal in eight consecutive neonates requiring ECMO after cardiac surgery between 2010 and 2012. PD was added to FO management when fluid removal goals were not being met by hemofiltration (HF) or hemodialysis (HD). Percent FO was 36% at ECMO initiation; 88% (seven of eight) achieved negative fluid balance before discontinuation of ECMO. PD removed median 119 mL/kg/day (interquartile range [IQR], 70-166) compared with median 132 mL/kg/day (IQR, 47-231) removed by HF/HD. PD and HF/HD fluid removal were performed concurrently 38% of the time. Unlike HF/HD, PD was never stopped secondary to hemodynamic compromise. Median duration of ECMO was 155 hours (IQR, 118-215). Six of eight patients were successfully decannulated. These results suggest PD safely and effectively removes fluid in neonates on ECMO after cardiac surgery. PD may increase total fluid removal potential when combined with other modalities.

Ethacrynic Acid continuous infusions in critically ill pediatric patients

OBJECTIVES

The purpose of this study was to describe dosage regimens and treatment outcomes in critically ill children receiving ethacrynic acid continuous infusions (CI).

METHODS

This retrospective cross-sectional study evaluated patients less than 18 years of age who received ethacrynic acid CI with a duration exceeding 12 hours, from January 1, 2007, through January 31, 2012. The primary objective was to determine the mean/median doses of ethacrynic acid CI. Secondary objectives were to assess surrogate efficacy markers (e.g., urine output [UOP], fluid balance) and the number of patients with electrolyte abnormalities or metabolic alkalosis. Descriptive statistics were used. A series of repeated measures analyses of variance were conducted to assess differences in surrogate efficacy markers and in adverse events that occurred pre-, mid-, and posttherapy.

RESULTS

Nine patients were included. The mean ± SD initial and maximum doses (mg/kg/hr) were 0.13 ± 0.07 (median 0.1; range, 0.08-0.3) and 0.17 ± 0.08 (median, 0.16; range 0.09-0.3), respectively. The median UOP (mL/kg/hr) pre-, mid-, and postinfusions (interquartile range [IQR]) were 2.4 (1.8-3.2), 4.2 (3.5-6), and 4 (3.4-5.3), respectively. The median fluid balance (mL; IQR) was 189 (90-526), -258 (-411.7 to 249) and -113.5 (-212.5 to 80.2), respectively. There were statistically significant differences in UOP and fluid balance pre- versus mid-therapy (0.014) and pre- versus posttherapy (p=0.010). No significant differences were noted with magnesium and potassium. Five children (55.6%) developed metabolic alkalosis.

CONCLUSIONS

This study provides preliminary evidence for ethacrynic acid CI in children. The median initial dose and maximum dose in this cohort were 0.13 mg/kg/hr and 0.17 mg/kg/hr, respectively. Larger prospective studies are needed to confirm these findings.

Clinical pharmacology of furosemide in neonates: a review

Furosemide is the diuretic most used in newborn infants. It blocks the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending limb of the loop of Henle increasing urinary excretion of Na⁺ and Cl⁻. This article aimed to review the published data on the clinical pharmacology of furosemide in neonates to provide a critical, comprehensive, authoritative and, updated survey on the metabolism, pharmacokinetics, pharmacodynamics and side-effects of furosemide in neonates. The bibliographic search was performed using PubMed and EMBASE databases as search engines; January 2013 was the cutoff point. Furosemide half-life (t_1/2) is 6 to 20-fold longer, clearance (Cl) is 1.2 to 14-fold smaller and volume of distribution (Vd) is 1.3 to 6-fold larger than the adult values. t_1/2 shortens and Cl increases as the neonatal maturation proceeds. Continuous intravenous infusion of furosemide yields more controlled diuresis than the intermittent intravenous infusion. Furosemide may be administered by inhalation to infants with chronic lung disease to improve pulmonary mechanics. Furosemide stimulates prostaglandin E2 synthesis, a potent dilator of the patent ductus arteriosus, and the administration of furosemide to any preterm infants should be carefully weighed against the risk of precipitation of a symptomatic patent ductus arteriosus. Infants with low birthweight treated with chronic furosemide are at risk for the development of intra-renal calcifications.

Acute kidney injury is a frequent complication in critically ill neonates receiving extracorporeal membrane oxygenation: a 14-year cohort study

Introduction

Newborns in need of extracorporeal membrane oxygenation (ECMO) support are at high risk of developing acute kidney injury (AKI). AKI may occur as part of multiple organ failure and can be aggravated by exposure to components of the extracorporeal circuit. AKI necessitates adjustment of dosage of renally eliminated drugs and avoidance of nephrotoxic drugs. We aimed to define systematically the incidence and clinical course of AKI in critically ill neonates receiving ECMO support.

Methods

This study reviewed prospectively collected clinical data (including age, diagnosis, ECMO course, and serum creatinine (SCr)) of all ECMO-treated neonates within our institution spanning a 14-year period. AKI was defined by using the Risk, Injury, Failure, Loss of renal function, and End-stage renal disease (RIFLE) classification. SCr data were reviewed per ECMO day and compared with age-specific SCr reference values. Accordingly, patients were assigned to RIFLE categories (Risk, Injury, or Failure as 150%, 200%, or 300% of median SCr reference values). Data are presented as median and interquartile range (IQR) or number and percentage.

Results

Of 242 patients included, 179 (74%) survived. Median age at the start of ECMO was 39 hours (IQR, 26 to 63); median ECMO duration was 5.8 days (IQR, 3.9 to 9.4). In total, 153 (64%) patients had evidence of AKI, with 72 (30%) qualifying as Risk, 55 (23%) as Injury, and 26 (11%) as Failure. At the end of the study period, only 71 (46%) patients of all 153 AKI patients improved by at least one RIFLE category. With regression analysis, it was found that nitric oxide ventilation (P = 0.04) and younger age at the start of ECMO (P = 0.004) were significant predictors of AKI. Survival until intensive care unit discharge was significantly lower for patients in the Failure category (35%) as compared with the Non-AKI (78%), Risk (82%), and Injury category (76%), with all P < 0.001, whereas no significant differences were found between the three latter RIFLE categories.

Conclusions

Two thirds of neonates receiving ECMO had AKI, with a significantly increased mortality risk for patients in the Failure category. As AKI during childhood may predispose to chronic kidney disease in adulthood, long-term monitoring of kidney function after ECMO is warranted.

Clinical pharmacology of the loop diuretics furosemide and bumetanide in neonates and infants

The loop diuretics furosemide and bumetanide are used widely for the management of fluid overload in both acute and chronic disease states. To date, most pharmacokinetic studies in neonates have been conducted with furosemide and little is known about bumetanide. The aim of this article was to review the published data on the pharmacology of furosemide and bumetanide in neonates and infants in order to provide a critical analysis of the literature, and a useful tool for physicians. The bibliographic search was performed electronically using PubMed and EMBASE databases as search engines and March 2011 was the cutoff point. The half-life (t(½)) of both furosemide and bumetanide is considerably longer in neonates than in adults and consequently the clearance (CL) of these drugs is reduced at birth. In healthy volunteers, plasma t(½) of furosemide ranges from 33 to 100 minutes, whereas in neonates it ranges from 8 to 27 hours. The volume of distribution (V(d)) of furosemide undergoes little variation during neonate maturation. The dose of furosemide, administered by intermittent intravenous infusion, is 1 mg/kg and may increase to a maximum of 2 mg/kg every 24 hours in premature infants and every 12 hours in full-term infants. Comparison of continuous infusion versus intermittent infusion of furosemide showed that the diuresis is more controlled with fewer hemodynamic and electrolytic variations during continuous infusion. The appropriate infusion rate of furosemide ranges from 0.1 to 0.2 mg/kg/h and when the diuresis is <1 mL/kg/h the infusion rate may be increased to 0.4 mg/kg/h. Treatment with theophylline before administration of furosemide results in a significant increase of urine flow rate. Bumetanide is more potent than furosemide and its dose after intermittent intravenous infusion ranges from 0.005 to 0.1 mg/kg every 24 hours. The t(½) of bumetanide in neonates ranges from 1.74 to 7.0 hours. Up to now, no data are available on the continuous infusion of bumetanide. Extracorporeal membrane oxygenation (ECMO) is used for a variety of indications including sepsis, persistent pulmonary hypertension, meconium aspiration syndrome, cardiac defects and congenital diaphragmatic hernia. There are two studies of furosemide in neonates undergoing ECMO and only one on the pharmacokinetics of bumetanide under ECMO. When ECMO was conducted for 72 hours, the total amount of furosemide administered was 7.0 mg/kg, and the urine production in the 3 days of treatment was about 6 mL/kg/h, which is the target value. The t(½) of bumetanide in neonates during ECMO was extremely variable. CL, t(½), and V(d) were 0.63 mL/min/kg, 13.2 hours, and 0.45 L/kg, respectively. Furosemide may be administered by inhalation and inhibits the bronco-constrictive effect of exercise, cold air ventilation and antigen challenge. However, inhaled furosemide is not active in infants with viral bronchiolitis and its effect on broncho-pulmonary dysplasia is still uncertain. Furosemide does not significantly increase the risk of failure of patent ductus arteriosus closure when indomethacin or ibuprofen have been co-administered. Infants with low birth weight treated long-term with furosemide are at risk for the development of intra-renal calcification. Furosemide therapy above 10 mg/kg bodyweight cumulative dose had a 48-fold increased risk of nephrocalcinosis. The use of furosemide in combination with indomethacin increased the incidence of acute renal failure. The maturation of the kidney governs the pharmacokinetics of furosemide and bumetanide in the infant. CL and t(½) are influenced by development, and this must be taken into consideration when planning a dosage regimen with these drugs.

Pharmacokinetic changes in patients receiving extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a form of prolonged cardiopulmonary bypass used to temporarily sustain cardiac and/or respiratory function in critically ill patients. Extracorporeal membrane oxygenation further complicates the management of critically ill patients who already have profound physiologic derangements with consequent altered pharmacokinetics. The purpose of this study is to identify and critically review the published literature describing pharmacokinetics in the presence of ECMO. This review revealed a dearth of data describing pharmacokinetics during ECMO in critically ill adults, with most of the available data originating in neonates. Of concern, the present data indicate substantial variability and a lack of predictability in drug behavior in the presence of ECMO. The most common mechanisms by which ECMO affects pharmacokinetics are sequestration in the circuit, increased volume of distribution, and decreased drug elimination. While lipophilic drugs and highly protein-bound drugs (eg, voriconazole and fentanyl) are significantly sequestered in the circuit, hydrophilic drugs (eg, β-lactam antibiotics, glycopeptides) are significantly affected by hemodilution and other pathophysiologic changes that occur during ECMO. Although the published literature is insufficient to make any meaningful recommendations for adjusting therapy for drug dosing, this review systematically describes the available data enabling clinicians to make conclusions based on available data. Furthermore, this review serves to highlight the need for well-designed and conducted clinical and laboratory-based studies to provide the data from which robust dosing guidance can be developed to improve clinical outcomes in this most unwell cohort of patients.

Neonatal diuretic therapy: furosemide, thiazides, and spironolactone

Diuretics are commonly used to treat infants with oxygen-dependent chronic lung disease. However, there are limited data suggesting a beneficial effect of long-term diuretic therapy on pulmonary function or clinical outcome in this population. Furthermore, data available for review were primarily obtained before the widespread use of antenatal steroids or surfactant replacement therapy, before recognition of the new bronchopulmonary dysplasia. If used in this population, limitations of diuretic therapy as well as significant side effects need to be understood and a rationale approach to clinical use developed on a patient-centered basis.

Use of extracorporeal life support in adults with severe acute respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a recognized and accepted therapeutic option in the treatment of neonatal and pediatric respiratory failure. However, early studies in adults did not demonstrate a survival benefit associated with the utilization of ECMO for severe acute respiratory failure. Despite this historical lack of benefit, use of ECMO in adult patients has seen a recent resurgence. Local successes and a recently published randomized trial have both demonstrated promising results in an adult population with high baseline mortality and limited therapeutic options. This article will review the history of ECMO use for respiratory failure; investigate the driving forces behind the latest surge in interest in ECMO for adults with refractory severe acute respiratory failure; and describe potential applications of ECMO that will likely increase in the near future.

Pediatric cardiovascular drug dosing in critically ill children and extracorporeal membrane oxygenation

Cardiovascular disease in children is common and results in significant morbidity and mortality. The sickest children with cardiovascular disease may require support with extracorporeal membrane oxygenation (ECMO), which provides life-saving assistance for children with refractory cardiorespiratory failure. Many classes of cardiovascular drugs are used in children, but very few of these agents have been well studied in children. The knowledge gap is even more pronounced in children supported by ECMO. Pharmacokinetic (PK) data collected to date (primarily from antibiotics and sedatives) suggest that the ECMO circuit has the potential to significantly alter the PK of drugs including changes in clearance and volume of distribution. Of all cardiovascular drugs administered to children supported by ECMO, only 11 have been partially studied and reported in the medical literature. Esmolol, amiodarone, nesiritide, bumetanide, sildenafil, and prostaglandin E1 seem to require dosing modifications in children supported by ECMO, whereas it seems that hydralazine, nicardipine, furosemide, epinephrine, and dopamine can be dosed similarly to children not supported by ECMO. However, trials evaluating the PK of these drugs in patients supported by ECMO are extremely limited (ie, case reports), and therefore, definitive dosing recommendations are not plausible. Research efforts should focus on evaluating the PK of drugs in patients on ECMO to avoid therapeutic failures or unnecessary toxicities.

A systematic review on pharmacokinetic changes in critically ill patients: role of extracorporeal membrane oxygenation

OBJECTIVE

Several factors including disease condition and different procedures could alter pharmacokinetic profile of drugs in critically ill patients. For optimizing patient's outcome, changing in dosing regimen is necessary. Extracorporeal Membrane Oxygenation (ECMO) is one of the procedures which could change pharmacokinetic parameters.The aim of this review was to evaluate the effect of ECMO support on pharmacokinetic parameters and subsequently pharmacotherapy.

METHOD

A systematic review was conducted by reviewing all papers found by searching following key words; extracorporeal membrane oxygenation, ECMO, pharmacokinetic and pharmacotherapy in bibliography database.

RESULTS

Different drug classes have been studied; mostly antibiotics. Almost all of the studies have been performed in neonates (as a case series). ECMO support is associated with altered pharmacokinetic parameters that may result in acute changes in plasma concentrations with potentially unpredictable pharmacological effect. Altreation in volume of distribution, protein binding, renal or hepatic clearance and sequestration of drugs by ECMO circuit may result in higher or lower doses requirement during ECMO. As yet, definite dosing guideline is not available. ECMO is extensively used recently for therapy and as a procedure affects pharmacokinetics profile along with other factors in critically ill patients. For optimizing the pharmacodynamic response and outcome of patients, drug regimen should be individualized through therapeutic drug monitoring whenever possible.

Haemofiltration in newborns treated with extracorporeal membrane oxygenation: a case-comparison study

INTRODUCTION

Extracorporeal membrane oxygenation is a supportive cardiopulmonary bypass technique for patients with acute reversible cardiovascular or respiratory failure. Favourable effects of haemofiltration during cardiopulmonary bypass instigated the use of this technique in infants on extracorporeal membrane oxygenation. The current study aimed at comparing clinical outcomes of newborns on extracorporeal membrane oxygenation with and without continuous haemofiltration.

METHODS

Demographic data of newborns treated with haemofiltration during extracorporeal membrane oxygenation were compared with those of patients treated without haemofiltration in a retrospective 1:3 case-comparison study. Primary outcome parameters were time on extracorporeal membrane oxygenation, time until extubation after decannulation, mortality and potential cost reduction. Secondary outcome parameters were total and mean fluid balance, urine output in mL/kg/day, dose of vasopressors, blood products and fluid bolus infusions, serum creatinin, urea and albumin levels.

RESULTS

Fifteen patients with haemofiltration (HF group) were compared with 46 patients without haemofiltration (control group). Time on extracorporeal membrane oxygenation was significantly shorter in the HF group: 98 hours (interquartile range (IQR) = 48 to 187 hours) versus 126 hours (IQR = 24 to 403 hours) in the control group (P = 0.02). Time from decannulation until extubation was shorter as well: 2.5 days (IQR = 0 to 6.4 days) versus 4.8 days (IQR = 0 to 121.5 days; P = 0.04). The calculated cost reduction was euro5000 per extracorporeal membrane oxygenation run. There were no significant differences in mortality. Patients in the HF group needed fewer blood transfusions: 0.9 mL/kg/day (IQR = 0.2 to 2.7 mL/kg/day) versus 1.8 mL/kg/day (IQR = 0.8 to 2.9 mL/kg/day) in the control group (P< 0.001). Consequently the number of blood units used was significantly lower in the HF group (P< 0.001). There was no significant difference in inotropic support or other fluid resuscitation.

CONCLUSIONS

Adding continuous haemofiltration to the extracorporeal membrane oxygenation circuit in newborns improves outcome by significantly reducing time on extracorporeal membrane oxygenation and on mechanical ventilation, because of better fluid management and a possible reduction of capillary leakage syndrome. Fewer blood transfusions are needed. All in all, overall costs per extracorporeal membrane oxygenation run will be lower.

An exploratory study with an adaptive continuous intravenous furosemide regimen in neonates treated with extracorporeal membrane oxygenation

INTRODUCTION

The objective of the present study was to explore a continuous intravenous furosemide regimen that adapts to urine output in neonates treated with extracorporeal membrane oxygenation (ECMO).

METHODS

Seven neonates admitted to a paediatric surgical intensive care unit for ECMO therapy were treated with a furosemide regimen consisting of a loading bolus (1-2 mg/kg) followed by a continuous infusion at 0.2 mg/kg per hour, which was adjusted according to the target urine production of 6 ml/kg per hour. Therapeutic drug monitoring for furosemide concentrations in blood was performed.

RESULTS

The mean +/- standard deviation furosemide dose was 0.17 +/- 0.06 mg/kg per hour, 0.08 +/- 0.04 mg/kg per hour and 0.12 +/- 0.07 mg/kg per hour, respectively, on the first day, second day and third day of the study. The median (range of the urine production of the study subjects) urine production over the consecutive study days was 6.8 (0.8-8.4) mg/kg per hour, 6.0 (4.7-8.9) mg/kg per hour and 5.4 (3.4-10.1) ml/kg per hour. The target urine production was reached after a median time of 7 (3-37) hours. The regimen was haemodynamically well tolerated and the median furosemide serum concentration was 3.1 (0.4-12.9) mug/ml, well below the toxic level.

CONCLUSION

The evaluated furosemide infusion appears an effective means to reduce volume overload in neonates treated with ECMO. The data of this preliminary study suggest that the starting dose of furosemide was too high, however, because the urine output was excessive and required frequent adaptations. The results of this study therefore indicate that a novel pharmacokinetic/pharmacodynamic model needs to be developed for neonates treated with ECMO.

Year in review 2006: Critical Care--Paediatrics

In 2006, paediatric intensive care-related subjects were discussed in a number of papers published in various journals, including Critical Care. Because they focused on the cardiovascular system and its support, we summarize them here. In particular, these papers highlighted the management of refractory septic shock, extracorporeal support, outcome markers in sepsis, and outcome after cardiac arrest.

Pharmacotherapy during neonatal extracorporeal membrane oxygenation: toward an evidence-based approach

Van der Vorst and coworkers recently illustrated the large variability in furosemide regimens used in their unit. This finding at least suggests that we need more data on the pharmacokinetics and pharmacodynamics of this drug in neonates during treatment with extracorporeal membrane oxygenation, in order to ensure quality of care and safety, and to promote evidence-based prescription. The implementation of population pharmacokinetic models can further increase both the feasibility of such studies and the relevance of the results generated.