Filtration of fentanyl is not the cause of the elevation of arterial blood pressure associated with post-bypass ultrafiltration in children

Effects of Modified Ultrafiltration on Thromboelastographic Profile after Pediatric Cardiac Surgery

Modified ultrafiltration (MUF) is still used after pediatric cardiopulmonary bypass (CPB) in some pediatric cardiac surgery centers to decrease transfusion requirements. Other potential benefits of MUF include clearance of inflammatory markers and improvement in myocardial function. Our hypothesis is that MUF will hemoconcentrate coagulation factors and improve thromboelastography (TEG) parameters after pediatric CPB. Patients younger than 6 months were prospectively enrolled over a year. TEG was carried out before MUF, after MUF, and after protamine administration. Paired t tests were conducted to compare values pre-MUF and post-MUF as well as post-MUF and post-protamine administration. Thirty patients were enrolled in the study, with 20 (67%) neonates in the cohort. Seven arterial switch operations and nine Norwood procedures were found to be performed among the cohort. Reaction time (R), angle (α), and maximum amplitude (MA) were significantly worse post-MUF compared with pre-MUF (p < .001). They improved significantly after protamine administration compared with post-MUF (p < .001). The amount of fluid removal was significantly associated with a worse post-MUF R, angle, and MA and worse post-protamine administration, angle, and MA but with no effect on post-protamine R. MUF caused worsening of TEG parameters that is reversed by protamine administration.

Dosing Recommendations for Pediatric Patients With Renal Impairment

A treatment gap exists for pediatric patients with renal impairment. Alterations in renal clearance and metabolism of drugs render standard dosage regimens inappropriate and may lead to drug toxicity, but these studies are not routinely conducted during drug development. The objective of this study was to examine the clinical evidence behind current renal impairment dosage recommendations for pediatric patients in a standard pediatric dosing handbook. The sources of recommendations and comparisons included the pediatric dosing handbook (Lexicomp), the U.S. Food and Drug Administration-approved manufacturer's labels, and published studies in the literature. One hundred twenty-six drugs in Lexicomp had pediatric renal dosing recommendations. Only 14% (18 of 126) of Lexicomp pediatric renal dosing recommendations referenced a pediatric clinical study, and 15% of manufacturer's labels (19 of 126) described specific dosing regimens for renally impaired pediatric patients. Forty-two products had published information on pediatric renal dosing, but 19 (45%) were case studies. When pediatric clinical studies were not referenced in Lexicomp, the renal dosing recommendations followed the adult and pediatric dosing recommendations on the manufacturer's label. Clinical evidence in pediatric patients does not exist for most renal dosing recommendations in a widely used pediatric dosing handbook, and the adult renal dosing recommendations from the manufacturer's label are currently the primary source of pediatric renal dosing information.

Pharmacokinetics of Fentanyl and Its Derivatives in Children: A Comprehensive Review

Fentanyl and its derivatives sufentanil, alfentanil, and remifentanil are potent opioids. A comprehensive review of the use of fentanyl and its derivatives in the pediatric population was performed using the National Library of Medicine PubMed. Studies were included if they contained original pharmacokinetic parameters or models using established routes of administration in patients younger than 18 years of age. Of 372 retrieved articles, 44 eligible pharmacokinetic studies contained data of 821 patients younger than 18 years of age, including more than 46 preterm infants, 64 full-term neonates, 115 infants/toddlers, 188 children, and 28 adolescents. Underlying diagnoses included congenital heart and pulmonary disease and abdominal disorders. Routes of drug administration were intravenous, epidural, oral-transmucosal, intranasal, and transdermal. Despite extensive use in daily clinical practice, few studies have been performed. Preterm and term infants have lower clearance and protein binding. Pharmacokinetics was not altered by chronic renal or hepatic disease. Analyses of the pooled individual patients' data revealed that clearance maturation relating to body weight could be best described by the Hill function for sufentanil (R ² = 0.71, B _max 876 mL/min, K ₅₀ 16.3 kg) and alfentanil (R ² = 0.70, B _{max (fixed)} 420 mL/min, K ₅₀ 28 kg). The allometric exponent for estimation of clearance of sufentanil was 0.99 and 0.75 for alfentanil clearance. Maturation of remifentanil clearance was described by linear regression to bodyweight (R ² = 0.69). The allometric exponent for estimation of remifentanil clearance was 0.76. For fentanyl, linear regression showed only a weak correlation between clearance and bodyweight in preterm and term neonates (R ² = 0.22) owing to a lack of data in older age groups. A large heterogeneity regarding study design, clinical setting, drug administration, laboratory assays, and pharmacokinetic estimation was observed between studies introducing bias into the analyses performed in this review. A limitation of this review is that pharmacokinetic data, based on different modes of administration, dosing schemes, and parameter estimation methods, were combined.

Correction to: Pharmacokinetics of Fentanyl and Its Derivatives in Children: A Comprehensive Review

Fentanyl and its derivatives sufentanil, alfentanil, and remifentanil are potent opioids. A comprehensive review of the use of fentanyl and its derivatives in the pediatric population was performed using the National Library of Medicine PubMed. Studies were included if they contained original pharmacokinetic parameters or models using established routes of administration in patients younger than 18 years of age. Of 372 retrieved articles, 44 eligible pharmacokinetic studies contained data of 821 patients younger than 18 years of age, including more than 46 preterm infants, 64 full-term neonates, 115 infants/toddlers, 188 children, and 28 adolescents. Underlying diagnoses included congenital heart and pulmonary disease and abdominal disorders. Routes of drug administration were intravenous, epidural, oral-transmucosal, intranasal, and transdermal. Despite extensive use in daily clinical practice, few studies have been performed. Preterm and term infants have lower clearance and protein binding. Pharmacokinetics was not altered by chronic renal or hepatic disease. Analyses of the pooled individual patients' data revealed that clearance maturation relating to body weight could be best described by the Hill function for sufentanil (R ² = 0.71, B _max 876 mL/min, K ₅₀ 16.3 kg) and alfentanil (R ² = 0.70, B _{max (fixed)} 420 mL/min, K ₅₀ 28 kg). The allometric exponent for estimation of clearance of sufentanil was 0.99 and 0.75 for alfentanil clearance. Maturation of remifentanil clearance was described by linear regression to bodyweight (R ² = 0.69). The allometric exponent for estimation of remifentanil clearance was 0.76. For fentanyl, linear regression showed only a weak correlation between clearance and bodyweight in preterm and term neonates (R ² = 0.22) owing to a lack of data in older age groups. A large heterogeneity regarding study design, clinical setting, drug administration, laboratory assays, and pharmacokinetic estimation was observed between studies introducing bias into the analyses performed in this review. A limitation of this review is that pharmacokinetic data, based on different modes of administration, dosing schemes, and parameter estimation methods, were combined.

The effects of modified ultrafiltration on clinical outcomes of adult and pediatric cardiac surgery

Background

Cardiopulmonary bypass (CPB) can contribute to the development of an inflammatory response and postsurgical morbidity. Conventional ultrafiltration and modified ultrafiltration (MUF) can mitigate the adverse effects of CPB by removing free water and inflammatory mediators, at least in part.

Objectives

To evaluate evidence for the effects of MUF on clinical outcomes of cardiac surgery in pediatric and adult patients.

Methods

A literature review of MEDLINE-indexed articles published between 1990 and June 2014 was conducted on PubMed. A search on the CTS.net website and the Cochrane Central Register of Controlled Trials was also performed with relevant keywords. The search was limited to English language articles and human studies.

Results

Our primary search identified 84 potential articles, of which 55 articles were relevant to conventional ultrafiltration, modified ultrafiltration, ultrafiltration, cardiopulmonary bypass, extracorporeal circulation, pediatric and adult cardiac surgery. There were 3 meta-analyses, 7 review literatures, 21 randomized controlled trials. The remainder consisted of 18 controlled and 6 observational studies. MUF has been beneficial effects on postoperative bleeding, chest drainage, transfusion requirement, and improvement cardiac function, but effects in adult cardiac surgery inconclusive because data was relatively limited.

Conclusions

MUF may improve post-CPB hemodynamic activity and cardiac function in pediatric cardiac surgery. By contrast, the clinical trials in adults are limited mostly by small sample sizes that preclude an adequately powered assessment of clinically relevant outcomes. The available data are conflicting and several studies show no differential outcomes. Further studies are required to identify patients who will most likely benefit from ultrafiltration and to establish standard protocols.

Modified Ultrafiltration in Children

Pediatric cardiopulmonary bypass (CPB) results in increased total body water and capillary permeability. Ultrafiltration has been effective in removing this excess water. The con ventional method of ultrafiltration is restricted by the vol ume in the venous reservoir and therefore is inefficient in smaller children and neonates, whose blood volume is dis proportionately smaller than the circuit volume. Modified ultrafiltration, performed in the immediate post-CPB period, is more effective in these patients. Blood from the aorta is pumped through the ultrafilter, and warm concentrated blood is returned to the right atrium. This removes excess water from the patient and provides a method of salvaging volume from the circuit. Modified ultrafiltration results in consistent improvements in systolic blood pressure, cardiac index, and lung compliance, as well as a reduction in pul monary vascular resistance. Removal of various inflamma tory mediators, such as tumor necrosis factor a, interleu kin-6, and interieukin-8, has been reported after modified ultrafiltration. Other advantages include an increase in he matocrit, colloid osmotic pressure, and coagulation factors, resulting in decreased bleeding and a decreased need for transfusions. In the animal model, improvement in cerebral recovery after deep hypothermic circulatory arrest has been reported. The disadvantages of this technique include the risk of air entrapment, delay in heparin reversal, and poten tial for cooling.

Impact of Modified Ultrafiltration on Morbidity after Pediatric Cardiac Surgery

Cardiopulmonary bypass is a double-edged sword. Without it, corrective cardiac surgery would not be possible in the majority of children with congenital heart disease. However, much of the perioperative morbidity that occurs after cardiac surgery can be attributed to a large extent to pathophysiologic processes engendered by extracorporeal circulation. One of the challenges that has confronted pediatric cardiac surgeons has been to minimize the consequences of cardiopulmonary bypass. Ultrafiltration is a strategy that has been used for many years in an effort to attenuate the effects of hemodilution that occur when small children undergo surgery with cardiopulmonary bypass. Over the past several years, a modified technique of ultrafiltration, commonly known as modified ultrafiltration, has been used with increasing enthusiasm. Multiple studies have been undertaken to assess the effects of modified ultrafiltration on organ function and postoperative morbidity following repair of congenital heart defects. This review attempts to evaluate current available scientific evidence on the impact of modified ultrafiltration on organ function and morbidity after pediatric cardiac surgery.

Modified ultrafiltration during cardiopulmonary bypass and postoperative course of pediatric cardiac surgery

Context:

The use of cardiopulmonary bypass (CPB) provokes the inflammatory responses associated with ischemic/reperfusion injury, hemodilution and other agents. Exposure of blood cells to the bypass circuit surface starts a systemic inflammatory reaction that may causes post-CPB organ dysfunction, particularly in lungs, heart and brain.

Evidence Acquisition:

We investigated in the MEDLINE, PUBMED, and EMBASE databases and Google scholar for every available article in peer reviewed journals between 1987 and 2013, for related subjects to CPB with conventional or modified ultrafiltration (MUF) in pediatrics cardiac surgery patients.

Results:

MUF following separation from extracorporeal circulation (ECC) provides well known advantages in children with improvements in the hemodynamic, pulmonary, coagulation and other organs functions. Decrease in blood transfusion, reduction of total body water, and blood loss after surgery, are additional benefits of MUF.

Conclusions:

Consequently, MUF has been associated with attenuation of morbidity after pediatric cardiac surgery. In this review, we tried to evaluate the current evidence about MUF on the organ performance and its effect on post-CPB morbidity in pediatric patients.

Use of modified ultrafiltration after repair of congenital heart defects

The use of cardiopulmonary bypass (CPB) for repair of congenital heart defects exposes children to extremes of hemodilution and hypothermia. Exposure of blood to the foreign surfaces of the oxygenator and bypass circuit initiates a systemic inflammatory response. Adverse effects of CPB include increased capillary permeability and increased total body water (TBW), which often results in tissue edema and multiple organ dysfunction. A variety of techniques have been developed for reversing tissue edema and hemodilution after CPB, including ultrafiltration during CPB, postoperative peritoneal dialysis, postoperative continuous arterial venous hemofiltration, and aggressive use of diuretics. A technique termed modified ultrafiltration (MUF) has been developed at the Hospital for Sick Children in London. Unlike conventional ultrafiltration, MUF is performed in the immediate post-CPB period and removes excess water from the patient as well as provides a method of salvaging blood from the circuit. MUF has been shown to modulate the inflammatory response to CPB by removing inflammatory mediators including interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF). A prospective randomized trial of MUF showed improved hemodynamics with a reduction in TBW and decreased need for blood transfusion when compared with nonfiltered controls. MUF has been shown to improve left ventricular systolic function after CPB, resulting in increased systolic blood pressure and cardiac index. In a recent study, use of MUF significantly reduced the incidence of pleural effusions after cavopulmonary connection and the Fontan procedure. MUF is a useful adjunct to CPB in children and significantly decreases perioperative morbidity. Copyright 1998 by W.B. Saunders Company

Modified ultrafiltration in paediatric cardiac surgery

The effect of modified ultrafiltration (MUF) after cardiopulmonary bypass for paediatric cardiac surgery was evaluated in 138 children with moderate to severe congenital heart disease. The median age was 0.4 years (0 days to 6.5 years), and the weight 5.3 kg (2.2-20 kg). The operation was discontinued in six cases, three because of technical problems and three because of unstable circulation. One-hundred-and-thirty-four patients were ultrafiltrated for a median of 12 min (2-27 min) with an ultrafiltrate of median 44 ml/kg (6-118 ml/kg). Haematocrit was significantly increased from 28% (20-39%) to 36% (26-51%) and systolic arterial pressure from 56 mmHg (30-85 mmHg) to 74.0 mmHg (32-118 mmHg). Furthermore arterial oxygenation was significantly increased from 30.8 kPa (4.8-70.4 kPa) to 34.1 kPa (4.9-80.6 kPa), and arterial carbon dioxide tension from 4.8 kPa (3.1-7.3 kPa) to 5.1 kPa (3.1-7.6 kPa). Heart rate was significantly reduced from 145 beats/min (92-201 beats/min) to 136 beats/min (88-200 beats/min). There were no significant differences in central venous pressure, left atrial pressure and base excess before and after MUF. MUF increases systolic blood pressure, haematocrit, arterial oxygen and carbon dioxide tension coming off bypass in paediatric cardiac surgery and reduces heart rate and postoperative fluid overload.

Modified ultrafiltration improves left ventricular systolic function in infants after cardiopulmonary bypass

OBJECTIVE

Our objective was to test the hypothesis that use of modified ultrafiltration after cardiopulmonary bypass improves intrinsic left ventricular systolic function in children.

METHODS

Twenty-one infants undergoing cardiopulmonary bypass were instrumented with ultrasonic dimension transducers, to measure the anteroposterior minor axis diameter, and a left ventricular micromanometer. Patients were randomized to modified ultrafiltration (n = 11, age 226 +/- 355 days, weight 6.7 +/- 3.1 kg) or control (n = 10, age 300 +/- 240 days, weight 7.0 +/- 2.5 kg) (all differences p > 0.05 between groups). Left ventricular systolic function was assessed by means of the slope of the preload-recruitable stroke work index. Myocardial cross-sectional area was measured by echocardiography. Data were acquired immediately after separation from bypass, at steady state, and during transient vena caval occlusion. Data acquisition was repeated after 13 +/- 5 minutes of modified ultrafiltration or after 12 +/- 5 minutes without modified ultrafiltration in the control group. Inotropic drug support was the same at both study points.

RESULTS

In the modified ultrafiltration group, the filtrate volume was 363 +/- 262 ml. The hematocrit value increased from 26.0% +/- 2.7% to 36.7% +/- 9.5% (p = 0.018), myocardial cross-sectional area decreased from 3.72 +/- 0.35 cm2 to 3.63 +/- 0.36 cm2 (p = 0.04), end-diastolic length increased from 25.6 +/- 9.0 mm to 28.8 +/- 9.9 mm (p = 0.01), and end-diastolic pressure fell from 5.6 +/- 0.8 mm Hg to 4.2 +/- 0.8 mm Hg (p = 0.005), suggesting an improved diastolic compliance. In the control group, the hematocrit value, myocardial cross-sectional area, end-diastolic length, and pressure did not change (all p > 0.05). Mean ejection pressure increased in the ultrafiltration group (p = 0.001) but did not change in the control group (p = 0.22). The slope of the preload-recruitable stroke work index increased after ultrafiltration from 52.3 +/- 52.0 to 74.2 +/- 66.0 (10[3] erg/cm3) (p = 0.02) but did not change in the control group (p = 0.07). One patient from each group died in the postoperative period. Patients in the ultrafiltration group received less inotropic drug support in the first 24 hours after the operation (156.62 +/- 92.31 microg/kg in 24 hours) than patients in the control group (865.33 +/- 1772.26 microg/kg in 24 hours, p = 0.03).

CONCLUSIONS

Use of modified ultrafiltration after cardiopulmonary bypass improves intrinsic left ventricular systolic function, improves diastolic compliance, increases blood pressure, and decreases inotropic drug use in the early postoperative period.