Population Pharmacokinetics of Milrinone in Neonates with Hypoplastic Left Heart Syndrome Undergoing Stage I Reconstruction

Comparison of Levosimendan Versus Milrinone After the Arterial Switch Operation for Infants ≤3 kg

Background: Various inotropes and inodilators have been utilized to treat low cardiac output syndrome after the arterial switch operation. The use of levosimendan, a calcium sensitizer has been limited in this setting. This study compares the effects of levosimendan with milrinone in managing low cardiac output after the arterial switch operation. Methods: A retrospective, comparative study was conducted in a tertiary care hospital on patients weighing up to 3 kg undergoing the arterial switch operation between January 2017 and January 2022. Patients received a loading dose followed by continuous infusion of either levosimendan or milrinone. Echocardiographic, hemodynamic and biochemical parameters were compared. Results: Forty-three patients received levosimendan and 42 patients received milrinone as the primary test drug. Cardiac index of less than 2.2 L/min/m2 on postoperative day 1 and 2 was found in 9.3% and 2.3% of patients receiving levosimendan versus 26.2% and 11.9% in those receiving milrinone, respectively (P = .04 and .08, respectively). Early lactate-clearance and better central venous oxygen saturations were noted in the levosimendan group. Prevalence of acute kidney injury was higher in the milrinone group (50% vs 28%; P = .03). Use of peritoneal dialysis in the milrinone group versus levosimendan was 31% and 16.3%, respectively (P = .11). There was no difference in hospital mortality between the groups (milrinone, 3; levosimendan, 2, P = .62). Conclusions: Levosimendan is safe and as effective as milrinone to treat low cardiac output syndrome occurring in neonates after the arterial switch operation. In addition we found that levosimendan was renal protective when compared with milrinone.

Milrinone for treatment of elevated lactate in the pre-operative newborn with hypoplastic left heart syndrome

BACKGROUND

There is a paucity of information reported regarding the use of milrinone in patients with hypoplastic left heart syndrome prior to the Norwood procedure. At our institution, milrinone is initiated in the pre-operative setting when over-circulation and elevated serum lactate levels develop. We aimed to review the responses associated with the administration of milrinone in the pre-operative hypoplastic left heart syndrome patient. Second, we compared patients who received high- versus low-dose milrinone prior to Norwood procedure.

METHODS

Single-centre retrospective study of patients diagnosed with hypoplastic left heart syndrome between January 2000 and December 2019 who underwent Norwood procedure. Patient characteristics and outcomes were compared.

RESULTS

During the study period, 375 patients were identified; 79 (21%) received milrinone prior to the Norwood procedure with median lactate 2.55 mmol/l, and SpO2 93%. Patients who received milrinone were older at the time of Norwood procedure (6 vs. 5 days) and were more likely to be intubated and sedated. In a subset analysis stratifying patients to low- versus high-dose milrinone, median lactate decreased from time of initiation (2.39 vs 2.75 to 1.6 vs 1.8 mmol/l) at 12 hours post-initiation, respectively. Repeated measures analysis showed a significant decrease in lactate levels by 4 hours following initiation of milrinone, that persisted over time, with no significant difference in mean arterial pressure.

CONCLUSIONS

The use of milrinone in the pre-operative over-circulated hypoplastic left heart syndrome patient is well tolerated, is associated with decreased lactate levels, and was not associated with significant hypotension or worsening of excess pulmonary blood flow.

Pulmonary vasodilator strategies in neonates with acute hypoxemic respiratory failure and pulmonary hypertension

The management of acute hypoxemic respiratory failure (AHRF) in newborns continues to be a clinical challenge with elevated risk for significant morbidities and mortality, especially when accompanied with persistent pulmonary hypertension of the newborn (PPHN). PPHN is a syndrome characterized by marked hypoxemia secondary to extrapulmonary right-to-left shunting across the ductus arteriosus and/or foramen ovale with high pulmonary artery pressure and increased pulmonary vascular resistance (PVR). After optimizing respiratory support, cardiac performance and systemic hemodynamics, targeting persistent elevations in PVR with inhaled nitric oxide (iNO) therapy has improved outcomes of neonates with PPHN physiology. Despite aggressive cardiopulmonary management, a significant proportion of patients have an inadequate response to iNO therapy, prompting consideration for additional pulmonary vasodilator therapy. This article reviews the pathophysiology and management of PPHN in term newborns with AHRF while highlighting both animal and human data to inform a physiologic approach to the use of PH-targeted therapies.

Assessment of the effect of two regimens of milrinone infusion in paediatric patients with pulmonary artery hypertension undergoing corrective cardiac procedure: A prospective observational study

Background

The aim of the study was to compare the effect of two different regimens of milrinone in pediatric patients with pulmonary artery hypertension (PAH) undergoing corrective procedure.

Materials and Methods

This randomized prospective study included 100 pediatric patients undergoing corrective cardiac surgeries. Group E: Milrinone was started as infusion 0.5 μg/kg/min without a loading dose after induction of anesthesia and continued as infusion 0.5-0.75 μg/kg/min in the pediatric cardiac surgical intensive care unit (PSICU). Group L: Milrinone was started as a loading dose 50 μg/kg over 10 min before weaning from cardiopulmonary bypass (CPB) followed by infusion 0.5-0.75 μg/kg/min in the PSICU. We compared heart rate, mean arterial blood pressure, central venous pressure, cardiac index (CI), mean pulmonary arterial pressure (MPAP), serum lactate level, urine output, vasoactive inotropic score, mechanical ventilation duration, and intensive care unit (ICU)- and hospital length of stay between the groups.

Results

There was an increase in mean arterial blood pressure, CI, and urine output in Group E compared to Group L (P < 0.05). MPAP, serum lactate level, and requirement of inotropes and vasopressors were lower in Group E compared to Group L (P < 0.05). Mechanical ventilation duration, ICU, and hospital length of stay were shorter in Group E than Group L (P < 0.05).

Conclusions

Early use of milrinone in patients with PAH undergoing corrective cardiac surgeries improved CI and mean arterial pressure, decreased MPAP, improved urine output, decreased serum lactate level, and decreased requirement of inotropes and vasopressors after weaning from CPB compared to the milrinone bolus group.

Hemodynamic response to milrinone for refractory hypoxemia during therapeutic hypothermia for neonatal hypoxic ischemic encephalopathy

OBJECTIVE

Characterize the impact of milrinone on arterial pressure of neonates with persistent hypoxemic respiratory failure (HRF) and hypoxic ischemic encephalopathy (HIE) treated with inhaled nitric oxide and therapeutic hypothermia (TH).

STUDY DESIGN

Retrospective cohort study. Arterial pressure was assessed hourly for 24 h. The primary outcome was change in diastolic arterial pressure (DAP).

RESULTS

56 patients were included [(i) cases: HIE/TH who received milrinone (n = 9), (ii) Milrinone controls (n = 17), (iii) HIE controls (n = 30)]. Baseline demographics, severity of HRF and arterial pressure were comparable between groups. Only milrinone treated patients with HIE/TH had a marked drop in DAP in the first hour, which persisted for more than 12 h despite escalation in inotropes (p = 0.008).

CONCLUSION

Milrinone treated patients with HRF and HIE/TH develop profound reduction in DAP and require escalation of cardiovascular support. The risk benefit profile of milrinone should be considered and pharmacological studies are warranted to evaluate drug metabolism and clearance in this population.

Population Pharmacokinetics of Milrinone in Infants, Children, and Adolescents

Milrinone is a type 3 phosphodiesterase inhibitor used to improve cardiac output in critically ill infants and children. Milrinone is primarily excreted unchanged in the urine, raising concerns for toxic accumulation in the setting of renal dysfunction of critical illness. We developed a population pharmacokinetic model of milrinone using nonlinear mixed-effects modeling in NONMEM to perform dose-exposure simulations in children with variable renal function. We included children aged <21 years who received intravenous milrinone per clinical care. Plasma milrinone concentrations were measured using a validated liquid chromatography-tandem mass spectrometry assay (range 1-5000 ng/mL). We performed dose-exposure simulations targeting steady-state therapeutic concentrations of 100-300 ng/mL previously established in adults and children with cardiac dysfunction. We simulated concentrations over 48 hours in typical subjects with decreasing creatinine clearance (CrCl), estimated using the updated bedside Schwartz equation. Seventy-four patients contributed 111 plasma samples (concentration range, 4-634 ng/mL). The median (range) postmenstrual age (PMA) was 3.7 years (0-18), and median weight (WT) was 13.1 kg (2.6-157.7). The median serum creatinine and CrCl were 0.5 mg/dL (0.1-3.1) and 117.2 mL/min/1.73 m2 (13.1-261.3), respectively. A 1-compartment model characterized the pharmacokinetic data well. The final model parameterization was: Clearance (L/h) = 15.9*(WT [kg] / 70)0.75 * (PMA1.12 / (67.71.12 +PMA1.12 )*(CrCl / 117)0.522 ; and Volume of Distribution (L) = 32.2*(WT [kg] / 70). A loading dose of 50 µg/kg followed by a continuous infusion of 0.5 µg/kg/min resulted in therapeutic concentrations, except when CrCl was severely impaired at ≤30 mL/min/1.73 m2 . In this setting, a 25 µg/kg loading dose and 0.25 µg/kg/min continuous infusion resulted in therapeutic exposures.

Population Pharmacokinetic/Pharmacodynamic Modeling of Methylprednisolone in Neonates Undergoing Cardiopulmonary Bypass

Methylprednisolone is used in neonates to modulate cardiopulmonary bypass (CPB)–induced inflammation, but optimal dosing and exposure are unknown. We used plasma methylprednisolone and interleukin (IL)‐6 and IL‐10 concentrations from neonates enrolled in a randomized trial comparing one vs. two doses of methylprednisolone to develop indirect response population pharmacokinetic/pharmacodynamic models characterizing the exposure–response relationships. We applied the models to simulate methylprednisolone dosages resulting in the desired IL‐6 and ‐10 exposures, known mediators of CPB‐induced inflammation. A total of 64 neonates (median weight 3.2 kg, range 2.2–4.3) contributed 290 plasma methylprednisolone concentrations (range 1.07–12,700 ng/mL) and IL‐6 (0–681 pg/mL) and IL‐10 (0.1–1125 pg/mL). Methylprednisolone plasma exposure following a single 10 mg/kg intravenous dose inhibited IL‐6 and stimulated IL‐10 production when compared with placebo. Higher (30 mg/kg) or more frequent (twice) dosing did not confer additional benefit. Clinical efficacy studies are needed to evaluate the effect of optimized dosing on outcomes.

Population Pharmacokinetics and Dosing of Milrinone After Patent Ductus Arteriosus Ligation in Preterm Infants

OBJECTIVES

The postoperative course of patent ductus arteriosus ligation is often complicated by postligation cardiac syndrome, occurring in 10-45% of operated infants. Milrinone might prevent profound hemodynamic instability and improve the recovery of cardiac function in this setting. The present study aimed to describe the population pharmacokinetics of milrinone in premature neonates at risk of postligation cardiac syndrome and give dosing recommendations.

DESIGN

A prospective single group open-label pharmacokinetics study.

SETTINGS

Two tertiary care neonatal ICUs: Tallinn Children's Hospital and Tartu University Hospital, Estonia.

PATIENTS

Ten neonates with postmenstrual age of 24.6-30.1 weeks and postnatal age of 5-27 days undergoing patent ductus arteriosus ligation and at risk of postligation cardiac syndrome, based on echocardiographic assessment of left ventricular output of less than 200 mL/kg/min 1 hour after the surgery.

INTERVENTIONS

Milrinone at a dose of 0.73 μg/kg/min for 3 hours followed by 0.16 μg/kg/min for 21 hours. Four blood samples from each patient for milrinone plasma concentration measurements were collected.

MEASUREMENTS AND MAIN RESULTS

Concentration-time data of milrinone were analyzed with nonlinear mixed-effects modeling software (NONMEM Version 7.3 [ICON Development Solutions, Ellicott City, MD]). Probability of target attainment simulations gave a dosing schedule that maximally attains concentration targets of 150-250 μg/L. Milrinone pharmacokinetics was described by a one-compartmental linear model with allometric scaling to bodyweight and an age maturation function of glomerular filtration rate. Parameter estimates for a patient with the median weight were 0.350 (L/hr) for clearance and 0.329 (L) for volume of distribution. The best probability of target attainment was achieved with a loading dose of 0.50 μg/kg/min for 3 hours followed by 0.15 μg/kg/min (postmenstrual age < 27 wk) or 0.20 μg/kg/min (postmenstrual age ≥ 27 wk).

CONCLUSIONS

Population pharmacokinetic modeling and simulations suggest a slow loading dose followed by maintenance infusion to reach therapeutic milrinone plasma concentrations within the timeframe of the postligation cardiac syndrome.

Acute Kidney Injury Biomarkers Predict an Increase in Serum Milrinone Concentration Earlier Than Serum Creatinine-Defined Acute Kidney Injury in Infants After Cardiac Surgery

BACKGROUND

Milrinone, an inotropic agent used ubiquitously in children after cardiac surgery, accumulates in acute kidney injury (AKI). We assessed if urinary AKI biomarkers are predictive of an increase in milrinone concentrations in infants after cardiac surgery.

METHODS

Multicenter prospective pilot study of infants undergoing cardiac surgery. Urinary AKI biomarkers were measured in the urine at specific time intervals after cardiopulmonary bypass initiation. AKI was defined using the Kidney Disease: Improving Global Outcomes serum creatinine criteria. Serum milrinone concentrations were measured at specific intervals after drug initiation, dose changes, and termination. Excessive milrinone activity was defined as a 20% increase in serum concentration between 6 and 36 hours after initiation. The temporal relationship between urinary AKI biomarker concentrations and a 20% increase in milrinone concentration was assessed.

RESULTS

AKI occurred in 31 (33%) of infants. Milrinone clearance was lower in patients with AKI (4.2 versus 5.6 L/h/70 kg; P = 0.02). Excessive milrinone activity was associated with development of serum creatinine-defined AKI [odds ratio (OR) 3.0; 95% confidence interval (CI), 1.21-7.39; P = 0.02]. Both tissue inhibitor metalloproteinase type 2 and insulin-like growth factor-binding protein type 7 (TIMP-2*IGFBP-7) ≥0.78 at 12 hours (OR 2.72; 95% CI, 1.01-7.38; P = 0.04) and kidney injury molecule 1 (KIM-1) ≥529.57 at 24 hours (OR 2.76; 95% CI, 1.06-7.17; P = 0.04) predicted excessive milrinone activity before a diagnosis of AKI.

CONCLUSIONS

In this pilot study, urine TIMP-2*IGFBP-7 and KIM-1 were predictive of AKI and excessive milrinone activity. Future studies that include a pharmacodynamics assessment of patient hemodynamics, excessive milrinone activity, and AKI biomarker concentrations may be warranted to integrate this concept into clinical practice.

Assessment of the effect of two regimens of milrinone infusion in pediatric patients undergoing fontan procedure: A randomized study

Objective:

The aim of the study was to compare the effect of two different regimens of milrinone on hemodynamics and oxygen saturation in pediatric patients undergoing Fontan procedure.

Design:

This was a randomized study.

Setting:

Cardiac centers.

Patients:

This study included 116 patients undergoing Fontan procedure.

Material and Methods:

Group E: Milrinone was started as infusion 0.5 μg/kg/min without a loading dose at the beginning of cardiopulmonary bypass (CPB) followed by infusion 0.5–0.75 μg/kg/min in the pediatric cardiac surgical intensive care unit (PSICU). Group L: Milrinone was started as a loading dose 50 μg/kg over 10 min before weaning from CPB followed by infusion 0.5–0.75 μg/kg/min in the PSICU.

Measurements:

Heart rate, mean arterial blood pressure, central venous pressure, transpulmonary pressure, cardiac index, pharmacological support, lactate level, urine output, oxygen saturation, ICU, and hospital length of stay.

Main Results:

There were no changes in the heart rate and mean arterial blood pressure (P > 0.05). The increase in the postoperative central venous pressure, transpulmonary pressure and lactate level was lower in Group E than Group L (P < 0.05). The increase in the postoperative cardiac index, oxygen saturation, and urine output was higher in Group E than Group L (P < 0.05). The requirement for pharmacological support was lower in the Group E (P < 0.05). The ICU and hospital length of stay were shorter in the Group E than Group L (P < 0.05).

Conclusion:

Early use of milrinone during Fontan procedure facilitated the weaning from CPB, decreased the elevation in the central venous pressure, transpulmonary gradient pressure, and the requirement for pharmacological support. Furthermore, it increased the cardiac index and arterial oxygen saturation.

Treating Hypotension in Preterm Neonates With Vasoactive Medications

Preterm neonates often have hypotension which may be due to various etiologies. While it is controversial to define hypotension in preterm neonates, various vasoactive medications are commonly used to provide the cardiovascular support to improve the blood pressure, cardiac output, or to treat shock. However, the literature on the systemic and regional hemodynamic effects of these antihypotensive medications in neonates is deficient and incomplete, and cautious translation of findings from other clinical populations and animal studies is required. Based on a literature search on published reports, meta-analytic reviews, and selected abstracts, this review discusses the current available information on pharmacologic actions, clinical effects, and side effects of commonly used antihypotensive medications including dopamine, dobutamine, epinephrine, norepinephrine, vasopressin, and milrinone in preterm neonates.

Cardiovascular Supportive Therapies for Neonates With Asphyxia - A Literature Review of Pre-clinical and Clinical Studies

Asphyxiated neonates often have hypotension, shock, and poor tissue perfusion. Various "inotropic" medications are used to provide cardiovascular support to improve the blood pressure and to treat shock. However, there is incomplete literature on the examination of hemodynamic effects of these medications in asphyxiated neonates, especially in the realm of clinical studies (mostly in late preterm or term populations). Although the extrapolation of findings from animal studies and other clinical populations such as children and adults require caution, it seems appropriate that findings from carefully conducted pre-clinical studies are important in answering some of the fundamental knowledge gaps. Based on a literature search, this review discusses the current available information, from both clinical studies and animal models of neonatal asphyxia, on common medications used to provide hemodynamic support including dopamine, dobutamine, epinephrine, milrinone, norepinephrine, vasopressin, levosimendan, and hydrocortisone.

The Perspective of the Intensivist on Inotropes and Postoperative Care Following Pediatric Heart Surgery: An International Survey and Systematic Review of the Literature

Introduction:

Inotropes are frequently being used in children undergoing heart surgery to prevent or treat low cardiac output syndrome (LCOS). There is only limited evidence that inotropes actually positively influence postoperative outcome. Our aim was to describe the current international practice variation in the use of inotropes following congenital heart surgery.

Methods:

We developed an online survey regarding the postoperative use of inotropes. We sent an invitation to all 197 registered members of the Pediatric Cardiac Intensive Care Society (PCICS) to participate in the survey. We also performed a systematic review of the literature.

Results:

Ninety-eight people (50%) responded, representing 62 international centers. Milrinone is routinely used perioperatively by 90 respondents (97%). Adrenaline/epinephrine is routinely used by 43%, dopamine by 36%, dobutamine by 11%, and levosimendan by 6%. Steroids are used routinely by 54% before initiating cardiopulmonary bypass. Vasopressin is used by 44% of respondents. The development of LCOS is monitored with lactate in 99% of respondents, physical examination (98%), intermittent mixed venous saturation (76%), continuous mixed venous saturation (13%), echocardiography (53%), core–peripheral temperature gap (29%), near-infrared spectrometry (25%), and 4% use cardiac output monitors (PiCCO, USCOM). To improve cardiac output, 42% add/increase milrinone, 37% add adrenaline, and 15% add dopamine. Rescue therapy is titrated individually, based on the patients’ pathophysiology. A systematic review of the literature failed to show compelling evidence with regard to the benefit of inotropes.

Conclusions:

Despite the lack of sufficient evidence, milrinone is used by the vast majority of caregivers following congenital heart surgery.

Milrinone Pharmacokinetics and Pharmacodynamics in Neonates with Persistent Pulmonary Hypertension of the Newborn

Objective To describe the pharmacokinetics and pharmacodynamics of milrinone in infants with persistent pulmonary hypertension of the newborn (PPHN) and to explore the impact of age on milrinone disposition. Design Randomized, open label pilot study. Setting Multicenter; level 3 and level 4 neonatal intensive care units. Patients Six infants ≥34 weeks' gestational age and <10 days of life with persistent hypoxemia receiving inhaled nitric oxide. Intervention Intravenous milrinone lactate in one of two dosing regimens: (1) low dose, 20 mcg/kg bolus followed by 0.2 mcg/kg/minute, and (2) standard dose, 50 mcg/kg bolus followed by 0.5 mcg/kg/minute. Measurements and Main Results The final structural model was a two-compartment disposition model with interindividual variability estimated on clearance (CL). The estimated value of CL is 7.65 mL/minute/3.4 kg (3.05 mL/minute/kg). The addition of age improved the precision of the CL estimate, and CL increased with chronological age in days. The oxygenation index was highly variable within each participant and improved with time. There were no observed safety concerns in either dosing group. Conclusion The CL of milrinone in newborns with PPHN is reduced and increases with age. In this pilot study, we did not see significant pharmacodynamic or safety effects associated with drug exposure.

Dosing of Milrinone in Preterm Neonates to Prevent Postligation Cardiac Syndrome: Simulation Study Suggests Need for Bolus Infusion

BACKGROUND

Milrinone has been suggested as a possible first-line therapy for preterm neonates to prevent postligation cardiac syndrome (PLCS) through decreasing systemic vascular resistance and increasing cardiac contractility. The optimal dosing regimen, however, is not known.

OBJECTIVE

To model the dosing of milrinone in preterm infants for prevention of PLCS after surgical closure of patent ductus arteriosus (PDA).

METHODS

Milrinone time-concentration profiles were simulated for 1,000 subjects using the volume of distribution and clearance estimates based on one compartmental population pharmacokinetic model by Paradisis et al. [Arch Dis Child Fetal Neonatal Ed 2007;92:F204-F209]. Dose optimization was based on retrospectively collected demographic data from neonates undergoing PDA ligation in Estonian PICUs between 2012 and 2014 and existing pharmacodynamic data. The target plasma concentration was set at 150-200 ng/ml.

RESULTS

The simulation study used demographic data from 31 neonates who underwent PDA ligation. The median postnatal age was 13 days (range: 3-29) and weight was 760 g (range: 500-2,351). With continuous infusion of milrinone 0.33 μg/kg/min, the proportion of subjects within the desired concentration range was 0% by 3 h, 36% by 6 h, and 61% by 8 h; 99% of subjects exceeded the range by 18 h. The maximum proportion of total simulated concentrations in the target range was attained with a bolus infusion of 0.73 μg/kg/min for 3 h followed by a 0.16-μg/kg/min maintenance infusion.

CONCLUSION

Mathematical simulations suggest that in preterm neonates the plasma time-concentration profile of milrinone can be optimized with a slow loading dose followed by maintenance infusion.

Milrinone Dosing Issues in Critically Ill Children With Kidney Injury: A Review

Milrinone is an inotropic drug used in a variety of clinical settings in adults and children. The efficacy of milrinone in pediatric low-cardiac output syndrome after cardiac surgery is reported. Its primary route of removal from the body is through the kidney as unchanged drug in the urine. Milrinone is not known to be efficiently removed by extracorporeal dialytic therapies and thus has the potential to cause serious adverse effects and potentially worsens renal function in patients experiencing acute kidney injury (AKI). AKI is an important public health issue that is associated with increased morbidity, mortality, and cost. It is a known risk factor for the development of chronic kidney disease. There are no specific therapies to mitigate AKI once it has developed, and interventions are focused on supportive care and dose adjustment of medications. Estimating glomerular filtration rate based on height and serum creatinine is the most commonly used clinical method for assessing kidney function and modification of medication doses. The purpose of this review is to discuss our current understanding of milrinone pharmacokinetics and pharmacodynamics in children with AKI and to describe the potential use of urinary biomarkers to guide therapeutic decision making for milrinone dosing.

Postoperative management of heart failure in pediatric patients

Low cardiac output syndrome (LCOS) is a well-described entity occurring in 25-65% of pediatric patients undergoing open-heart surgery. With judicious intensive care management of LCOS, most patients have an uncomplicated postoperative course, and within 24 h after cardiopulmonary bypass, the cardiac function returns back to baseline. Some patients have severe forms of LCOS not responsive to medical management alone, requiring temporary mechanical circulatory support to prevent end-organ injury and to decrease myocardial stress and oxygen demand. Occasionally, cardiac function does not recover and heart transplantation is necessary. Long-term mechanical circulatory support devices are used as a bridge to transplantation because of limited availability of donor hearts. Experience in usage of continuous flow ventricular assist devices in the pediatric population is increasing.

Prophylactic milrinone for the prevention of low cardiac output syndrome and mortality in children undergoing surgery for congenital heart disease

BACKGROUND

Children with congenital heart disease often undergo heart surgery at a young age. They are at risk for postoperative low cardiac output syndrome (LCOS) or death. Milrinone may be used to provide inotropic and vasodilatory support during the immediate postoperative period.

OBJECTIVES

This review examines the effectiveness of prophylactic postoperative use of milrinone to prevent LCOS or death in children having undergone surgery for congenital heart disease.

SEARCH METHODS

Electronic and manual literature searches were performed to identify randomised controlled trials. We searched CENTRAL, MEDLINE, EMBASE and Web of Science in February 2014 and conducted a top-up search in September 2014 as well as clinical trial registries and reference lists of published studies. We did not apply any language restrictions.

SELECTION CRITERIA

Only randomised controlled trials were selected for analysis. We considered studies with newborn infants, infants, toddlers, and children up to 12 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data according to a pre-defined protocol. We obtained additional information from all study authors.

MAIN RESULTS

Three of the five included studies compared milrinone versus levosimendan, one study compared milrinone with placebo, and one compared milrinone verus dobutamine, with 101, 242, and 50 participants, respectively. Three trials were at low risk of bias while two were at higher risk of bias. The number and definitions of outcomes were non-uniform as well. In one study comparing two doses of milrinone and placebo, there was some evidence in an overall comparison of milrinone versus placebo that milrinone lowered risk for LCOS (risk ratio (RR) 0.52, 95% confidence interval (CI) 0.28 to 0.96; 227 participants). The results from two small studies do not provide enough information to determine whether milrinone increases the risk of LCOS when compared to levosimendan (RR 1.22, 95% CI 0.32 to 4.65; 59 participants). Mortality rates in the studies were low, and there was insufficient evidence to draw conclusions on the effect of milrinone compared to placebo or levosimendan or dobutamine regarding mortality, the duration of intensive care stay, hospital stay, mechanical ventilation, or maximum inotrope score (where available). Numbers of patients requiring mechanical cardiac support were also low and did not allow a comparison between studies, and none of the participants of any study received a heart transplantation up to the end of the respective follow-up period. Time to death within three months was not reported in any of the included studies. A number of adverse events was examined, but differences between the treatment groups could not be proven for hypotension, intraventricular haemorrhage, hypokalaemia, bronchospasm, elevated serum levels of liver enzymes, or a reduced left ventricular ejection fraction < 50% or reduced left ventricular fraction of shortening < 28%. Our analysis did not prove an increased risk of arrhythmias in patients treated prophylactically with milrinone compared with placebo (RR 3.59, 95% CI 0.83 to 15.42; 238 participants), a decreased risk of pleural effusions (RR 1.78, 95% CI 0.92 to 3.42; 231 participants), or a difference in risk of thrombocytopenia on milrinone compared with placebo (RR 0.86, 95% CI 0.39 to 1.88; 238 participants). Comparisons of milrinone with levosimendan or with dobutamine, respectively, did not clarify the risk of arrhythmia and were not possible for pleural effusions or thrombocytopenia.

AUTHORS' CONCLUSIONS

There is insufficient evidence of the effectiveness of prophylactic milrinone in preventing death or low cardiac output syndrome in children undergoing surgery for congenital heart disease, compared to placebo. So far, no differences have been shown between milrinone and other inodilators, such as levosimendan or dobutamine, in the immediate postoperative period, in reducing the risk of LCOS or death. The existing data on the prophylactic use of milrinone has to be viewed cautiously due to the small number of small trials and their risk of bias.

Off-label drug use in a single-center pediatric cardiac intensive care unit

BACKGROUND

The frequency of off-label drug use and its association with morbidity and mortality in the cardiac intensive care unit (CICU) has not been previously studied.

METHODS

Patients less than 18 years of age admitted to the CICU from June to August 2008 were retrospectively identified. Patient demographics were collected for 30 days or until CICU discharge. Off-label drug use was defined as the prescription of a medication that lacked a labeled indication based on patient's age as reported in the Micromedex drug database and electronic Physician's Desk Reference.

RESULTS

Eighty-two patients were admitted to the CICU during the study period. In all, 40 (46%) patients were male; the median age was 10.6 months. Common diagnoses were left-to-right shunt lesions (20.7%) and single-ventricle lesions (20.7%), with an overall mortality of 2.4%. Of all drugs prescribed, 36% were off-label. In all, 94% of the patients received ≥1 drug off-label. The median number of drugs prescribed off-label was four. Patients receiving more than four off-label medications were younger, had longer CICU lengths of stay (median 9.5 vs 2 days, P < .001), and increased ventilator days (median two vs one day, P < .001).

CONCLUSIONS

Off-label drug use in the CICU is common. Frequency of use is likely higher in patients with a higher severity of illness. Further safety, efficacy, and pharmaceutical trials are warranted to optimize the use of these drugs to improve outcomes.

Limitations and vulnerabilities of the neonatal cardiovascular system: considerations for anesthetic management

Development of the cardiovascular system through the last trimester of pregnancy and the subsequent neonatal period is profound. Morphological changes within the myocardium make the heart vulnerable to challenges such as fluid shifts and anesthetic drugs. The sensitivity of the myocardium to metabolic challenges and potential harm of drugs needed to maintain adequate blood pressure and cardiac output are highlighted. Traditional monitoring under anesthesia has focussed on maintaining oxygenation and heart rate in the neonate with less attention paid to blood pressure, cardiac output, and more importantly organ well-being. There is now a better understanding of the limitations of blood pressure homeostasis in the neonate and the potential consequences of marginal hypoperfusion. This article highlights some of these vulnerabilities particularly as they relate to anesthesia and surgery in the very young.

Population pharmacokinetic analysis during the first 2 years of life: an overview

Three decades after its introduction, pharmacokinetic population approaches have become a reference method for drug modelling, particularly in paediatrics. The main practical limitation in this specific population is the collected blood volume. Pharmacokinetic population approaches using sparse sampling may resolve this issue. The pharmacokinetics of many drugs have been studied during the last 25 years using such methods. This review summarizes all of the published studies concerning population pharmacokinetic approaches in paediatric subjects from neonate to 2 years old. A literature search was conducted using the PubMed database, from 1985 to December 2010, using the following terms: pharmacokinetic(s), population, paediatric/pediatric and neonate(s). Articles were excluded if they were not pertinent according to our criteria. References of all relevant articles were also evaluated. Ninety-eight studies were included in this review. The following information was extracted from the articles: drug name, therapeutic class, population size, age of patients, number of samples per patient, covariates used for clearance and volume of distribution estimates, software used for modelling and validation methods. An increasing rate of publications over the years was observed; 44 different drugs were studied using a pharmacokinetic population approach. Antibacterials were the most studied class of drugs, including a large number of studies devoted to vancomycin and gentamicin. It must be underlined that few studies have been performed on anticonvulsant drugs and anaesthetics used in clinical daily practice conditions.

Strategic biomarkers for drug development in treating rare diseases and diseases in neonates and infants

There are similar challenges in developing a product designed to treat patients with a rare disease and drugs to treat critically ill neonates and infants. Part of the challenge in developing such products as well as identifying the optimal dosing regimen for the treatment of young children arises from the complex interrelationship between developmental changes and changes in biomarkers responsive to drug therapy. These difficulties are further compounded by our lack of understanding of the key physiological factors that cause the differences in clinical responses between adults and neonates and infants. Regulatory efforts have succeeded in overcoming these challenges in many areas of pediatric and orphan drug development. Strategic applications of biomarkers and surrogate endpoints for the development and approval of a product used to treat an orphan disease will be highlighted with examples of approved products. Continued efforts are still needed to fill in our knowledge gap and to strategically link biomarkers and surrogate endpoints to clinical responses for rare diseases and diseases affecting neonates and infants.

Phase 1 study of two inodilators in neonates undergoing cardiovascular surgery

BACKGROUND

Inodilators are routinely used in cardiovascular surgery with cardiopulmonary bypass (CPB). Information regarding safety and tolerability of the novel molecule, levosimendan (LEVO), in newborns is anecdotal; no pharmacokinetic data in this population are available.

METHODS

This was a phase I, randomized, and blinded study. Neonates undergoing surgical repair for congenital heart defects received stepwise dose increases of milrinone (MR; 0.5-1 μg/kg/min, n = 9) or LEVO (0.1-0.2 μg/kg/min, n = 11) as an i.v. continuous infusion, starting before CPB. Infants had continuous, time-locked, physiological, and near-infrared spectroscopy (NIRS) (cerebral and peripheral) recordings during the first 24 h, and at 48 and 96 h postsurgery. Serial biochemistry and pharmacokinetic studies were performed.

RESULTS

During the first 24 h postsurgery, patients showed time-related, group-independent increased cerebral tissue oxygenation and decreased diastolic blood pressure; in addition, group-dependent differences in heart rate and peripheral perfusion were found. Early postsurgery, MR-treated infants showed lower pH, higher glycemia, and higher inotrope score. The groups differed in cerebral NIRS-derived variables from 24 to 96 h. Study drug withdrawal at 96 h was more frequent with LEVO. LEVO intermediate metabolites were detected in plasma at day 14 after surgery.

CONCLUSION

LEVO is well tolerated in critically ill neonates. LEVO may have advantages over MR in terms of the dosing regimen.

Pharmacology of milrinone in neonates with persistent pulmonary hypertension of the newborn and suboptimal response to inhaled nitric oxide

OBJECTIVES

Persistent pulmonary hypertension of the newborn is a common problem with significant morbidity and mortality. Inhaled nitric oxide is the standard care, but up to 40% of neonates are nonresponders. Milrinone is a phosphodiesterase III inhibitor which increases the bioavailability of cyclic adenosine monophosphate and has been shown to improve pulmonary hemodynamics in animal experimental models. The primary objective was to investigate the pharmacological profile of milrinone in persistent pulmonary hypertension of the newborn. Secondary objectives were to delineate short-term outcomes and safety profile.

SUBJECTS AND METHODS

An open label study of milrinone in neonates with persistent pulmonary hypertension of the newborn was conducted. Patients received an intravenous loading dose of milrinone (50 μg/kg) over 60 mins followed by a maintenance infusion (0.33-0.99 μg/kg/min) for 24-72 hrs. Physiologic indices of cardiorespiratory stability and details of cointerventions were recorded. Serial blood milrinone levels were collected after the bolus, following initiation of the maintenance infusion to determine steady state levels, and following discontinuation of the drug to determine clearance. Echocardiography was performed before and after (1, 12 hrs) milrinone initiation.

INTERVENTIONS

Milrinone.

MEASUREMENTS AND MAIN RESULTS

Eleven neonates with a diagnosis of persistent pulmonary hypertension of the newborn who met eligibility criteria were studied. The median (SD) gestational age and weight at birth were 39.2 ± 1.3 wks and 3481 ± 603 g. The mean (± sd) half-life, total body clearance, volume of distribution, and steady state concentration of milrinone were 4.1 ± 1.1 hrs, 0.11 ± 0.01 L/kg/hr, 0.56 ± 0.19 L/kg, and 290.9 ± 77.7 ng/mL. The initiation of milrinone led to an improvement in PaO2 (p = 0.002) and a sustained reduction in FIO2 (p < 0.001), oxygenation index (p < 0.001), mean airway pressure (p = 0.03), and inhaled nitric oxide dose (p < 0.001). Although a transient reduction in systolic arterial pressure (p < 0.001) was seen following the bolus, there was overall improvement in base deficit (p = 0.01) and plasma lactate (p = 0.04) with a trend towards lower inotrope score. Serial echocardiography revealed lower pulmonary artery pressure, improved right and left ventricular output, and reduced bidirectional or right-left shunting (p < 0.05) after milrinone treatment.

CONCLUSIONS

The pharmacokinetics of milrinone in persistent pulmonary hypertension of the newborn is consistent with published data. The administration of intravenous milrinone led to better oxygenation and improvements in pulmonary and systemic hemodynamics in patients with suboptimal response to inhaled nitric oxide. These data support the need for a randomized controlled trial in neonates.

Use of milrinone in critically ill children

BACKGROUND

Optimal dose adjustment of milrinone in critically ill children is challenging because of conflicting information about the association between dose and outcomes in this age group.

OBJECTIVES

To describe the use of milrinone in critically ill children and to explore associations between milrinone dosing and clinical outcomes, specifically effectiveness and adverse events.

METHODS

This retrospective cohort study was performed in a consecutive sample of children admitted to a university-affiliated critical care unit (January to June 2004). The relations between milrinone dosing and its effectiveness (based on prevention of low cardiac output syndrome, defined as a difference in oxygen saturation between arterial and mixed venous blood of at least 30% or an increase in serum lactate > 2 mmol/L) and its adverse effects (thrombocytopenia, arrhythmia) were evaluated by logistic regression.

RESULTS

A total of 197 children from 213 admissions (ranging in age from newborn to 18 years) were included in the study. Milrinone was initiated with a median loading dose of 99.2 μg/kg (range 22.1-162.2 μg/kg). The initial loading dose was higher if given in the operating room rather than the Critical Care Unit (median 99.7 versus 51.0 μg/kg; p < 0.001). Subsequent loading doses, for patients who received them, were lower (median 49 μg/kg). Milrinone was infused at a median rate of 0.64 μg/kg per minute (range 0.13-2.08 μg/kg per minute) for a median of 43.1 h. There was no relation between serum creatinine level and the maintenance dose of milrinone (r2 ≤ 0.0335). Low cardiac output syndrome was relatively frequent (166 [77.9%] of the 213 admissions). There was a trend for occurrence of this syndrome in patients with greater average milrinone dose rate (odds ratio [OR] 8.21, 95% confidence interval [CI] 0.98-69.15, p = 0.053) and with longer duration of milrinone therapy (OR 1.01, 95% CI 1.01-1.02, p < 0.05). Adverse events were relatively frequent (thrombocytopenia for 27 admissions [12.7%], arrhythmia for 82 admissions [38.5%]) but were not significantly associated with milrinone dosing.

CONCLUSIONS

A retrospective evaluation of milrinone use in critically ill children revealed variable utilization and frequent occurrence of both low cardiac output syndrome and adverse events. Further prospective research is needed to understand the impact of individual pharmacokinetic differences on pharmacodynamic responses, to guide optimal dose adjustment, improve outcomes, and minimize toxic effects.

Heart Failure Treated with Low-dose Milrinone in a Full-term Newborn

A term newborn with a hypocontractile myocardium complicating persistent pulmonary hypertension of the newborn was successfully treated with a low-dose phosphodiesterase III inhibitor milrinone. Echocardiography diagnosed heart failure with a left ventricular ejection fraction of 35% and a left ventricular shortening fraction of 18% and severe persistent pulmonary hypertension of the newborn with oxygenation index of 28. Milrinone was started at an initial dose of 50 mcg/kg, followed by continuous infusion of 0.20 mcg/kg/min. With lowdose milrinone oxygenation index decreased to 3 within 6 hours, left ventricular ejection fraction and left ventricular shortening fraction increased to 57%, and 30%, respectively. Low doses of milrinone might be promising in the treatment of heart failure and persistent pulmonary hypertension of the newborn in term newborns.

Contemporary management of pulmonary and systemic circulations after the Norwood procedure

Hypoplastic left heart syndrome remains one of the most challenging pathologies in pediatric cardiac surgery. The surgical techniques, and anesthetic and intensive care management, have evolved over the last decades, which has resulted in improved outcomes. A central component in the postoperative management of hypoplastic left heart syndrome patients is to achieve an optimal balance between the pulmonary and systemic circulations. This article discusses the contemporary postoperative management of pulmonary and systemic circulations in detail.

Heart failure treatment in the intensive care unit in children

Although pediatric heart failure is generally a chronic, progressive disorder, recovery of ventricular function may occur with some forms of cardiomyopathy. Guidelines for the management of chronic heart failure in adults and children have recently been published by the International Society for Heart and Lung Transplantation the American College of Cardiology, and the American Heart Association. The primary aim of heart failure therapy is to reduce symptoms, preserve long-term ventricular performance, and prolong survival primarily through antagonism of the neurohormonal compensatory mechanisms. Because some medications may be detrimental during an acute decompensation, physicians who manage these patients as inpatients must be knowledgeable about the medications and therapeutic goals of chronic heart failure treatment. Understanding the mechanisms of chronic heart failure may foster improved understanding of the treatment of decompensated heart failure.

Rotating inotrope therapy in a pediatric population with decompensated heart failure

OBJECTIVE

To describe the clinical course of a group of patients who received a rotating inotrope regimen, including levosimendan, for decompensated congestive heart failure.

DESIGN

Case series.

SETTING

Pediatric intensive care unit in a tertiary care children's hospital.

PATIENTS

Nine pediatric patients with severe, decompensated heart failure.

INTERVENTION

The study patients received a rotating inotrope regimen, including levosimendan, dobutamine, and, in some cases, milrinone.

MEASUREMENTS AND MAIN RESULTS

Six patients were weaned from positive-pressure ventilation. Eight patients were discharged from the intensive care unit, and seven survived to hospital discharge. Two patients were successfully bridged to orthotopic cardiac transplantation. The therapies were generally well tolerated.

CONCLUSIONS

Rotating inotropes were safe and seemed to be effective in this heterogeneous population of infants and children with decompensated heart failure. This therapeutic regimen warrants prospective comparative analysis.

Milrinone for persistent pulmonary hypertension of the newborn

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is a clinical syndrome characterized by suboptimal oxygenation as a result of sustained elevation in pulmonary vascular resistance after birth. Currently, the therapeutic mainstay for PPHN is optimal lung inflation and selective vasodilatation with inhaled nitric oxide (iNO). However, iNO is not available in all countries and not all infants will respond to iNO. Milrinone is a phosphodiesterase III inhibitor which induces pulmonary vasodilatation by its actions through a cyclic adenylate monophosphate mediated signaling pathway.

OBJECTIVES

To assess efficacy and safety in infants with PPHN either treated with: milrinone compared with placebo or no treatment; milrinone compared with iNO; milrinone as an adjunct to iNO compared with iNO alone; milrinone compared with potential treatments for PPHN other than iNO.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2010), MEDLINE and EMBASE databases from their inception until January 2010. We searched the reference lists of potentially relevant studies without any language restriction.

SELECTION CRITERIA

Fully published randomized controlled trials (RCTs) and quasi-RCTs comparing milrinone with placebo, iNO or potential treatments other than iNO in neonates with PPHN were included if trials reported any clinical outcome.

DATA COLLECTION AND ANALYSIS

We found no studies meeting the criteria for inclusion in this review.

MAIN RESULTS

We found no studies meeting the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

The efficacy and safety of milrinone in the treatment of PPHN are not known and its use should be restricted within the context of RCTs. Such studies should address a comparison of milrinone with placebo (in clinical situations where iNO is not available) or, in well resourced countries, should compare milrinone with iNO or as an adjunct to iNO compared with iNO alone.

Postoperative course in the cardiac intensive care unit following the first stage of Norwood reconstruction

The medical records of all patients born between 1 September, 2000, and 31 August, 2002, and undergoing the first stage of Norwood reconstruction, were retrospectively reviewed for details of the perioperative course. We found 99 consecutive patients who met the criterions for inclusion. Hospital mortality for the entire cohort was 15.2%, but was 7.3%, with 4 of 55 dying, in the setting of a "standard" risk profile, as opposed to 25.0% for those with a "high" risk profile, 11 of 44 patients dying in this group. Extracorporeal membrane oxygenation was utilized in 7 patients, with 6 deaths. Median postoperative length of stay in the hospital was 14 days, with a range from 2 to 85 days, and stay in the cardiac intensive care unit was 11 days, with a range from 2 to 85 days. Delayed sternal closure was performed in 18.2%, with a median of 1 day until closure, with a range from zero to 5 days. Excluding isolated delayed sternal closure, and cannulation and decannulation for extracorporeal support, 24 patients underwent 33 cardiothoracic reoperations, including exploration for bleeding in 12, diaphragmatic plication in 4; shunt revision in 4, and other procedures in 13. The median duration of total mechanical ventilation was 4.0 days, with a range from 0.7 to 80.5 days. Excluding those who died, the median total duration of mechanical ventilation was 3.8 days, with a range from 0.9 to 46.3 days. Reintubation for cardiorespiratory failure or upper airway obstruction was performed in 31 patients. Postoperative electroencephalographic and/or clinical seizures occurred in 13 patients, with 7 discharged on anti-convulsant medications. Postoperative renal failure, defined as a level of creatinine greater than 1.5 mg/dl, was present in 13 patients. Eleven had significant thrombocytopenia, with fewer than 20,000 platelets per microl, and injury to the vocal cords was identified in eight patients. Risk factors for longer length of stay included lower Apgar scores, preoperative intubation, early reoperations, reintubation and sepsis, but not weight at birth, genetic syndromes, the specific surgeon, or the duration of surgery. Although mortality rates after the first stage of reconstruction continue to fall, the course in the intensive care unit is remarkable for significant morbidity, especially involving the cardiac, pulmonary and central nervous systems. These patients utilize significant resources during the first hospitalization. Further studies are necessary to stratify the risks faced by patients with hypoplasia of the left heart in whom the first stage of Norwood reconstruction is planned, to determine methods to reduce perioperative morbidity, and to determine the long-term implications of short-term complications, such as diaphragmatic paresis, injury to the vocal cords, prolonged mechanical ventilation, and postoperative seizures.

Hypoplastic left heart syndrome: consensus and controversies in 2007

Variability in practice can be considered to foster clinical innovation, and allow for individualized therapeutic plans and independence of practitioners. The Institute of Medicine, however, has issued a report suggesting that variability in patterns of practice are "illogical", and should be avoided whenever possible. Perhaps nowhere in the field of congenital cardiac disease is variability in practice more apparent than in the management of hypoplastic left heart syndrome. This review assesses the variability in practice at a large number of centres that manage neonates with hypoplastic left heart syndrome, with an emphasis on practice before, during, and after the first stage of the Norwood sequence of operations. We also suggest changes in future strategies for research. In March, 2007, colleagues were contacted to respond to an internet-based survey using commercially available software (www.surveymonkey.com) to collect responses about the management practices for neonates with "straight-forward" hypoplastic left heart syndrome. No attempt was made to correlate management practices with any measures of outcome, as neither the practices themselves, nor the outcomes of interest, could be externally validated. Data is reported from 52 centers thought to manage over 1000 neonates with hypoplastic left heart syndrome on an annual basis. The first stage of the Norwood sequence was "recommended" to families by approximately five-sixths (86.5%) of the centres. No centre recommended primary cardiac transplantation, a "hybrid" approach, or non-intervention. In 7 centres (14.5%), it was reported that there was discussion of some or all of the above options, but ultimately the families decided upon the appropriate strategy. Most centres preferentially used antegrade cerebral perfusion (54%) in contrast to deep hypothermia with circulatory arrest (24%), albeit that 11% of centres used a combination of these techniques and in 9% the support strategy was based on surgeon preference. The source of flow of blood for the lungs following the first stage of reconstruction was also highly variable. Of the 51 centres that responded to the question, 13 (25.5%) were participating in a multi-centric randomized clinical trial comparing the modified Blalock-Taussig shunt to the conduit placed from the right ventricle to the pulmonary arteries, the so-called "Sano" modification. Of the remaining 38 centres, 18 "usually" placed a conduit from the right ventricle to the pulmonary artery, 14 "usually" placed a modified Blalock-Taussig shunt, and at six centres, the decision was made "based upon the preference of the surgeon and/or the cardiologist". Similarly, significant variability in practice was evident in preoperative management, other surgical strategies, postoperative medical support, monitoring and discharge planning. Other than the randomized clinical trial of shunt type, no other medical or surgical management strategy was currently under investigation in a multi-centric or randomized trial in the centres who responded to the survey. The survey emphasises the extreme variability in our current practices for treatment of children with hypoplastic left heart syndrome. While there are some areas for which there is consensus in management, the majority of our practices are variable between and within centres. These results emphasize that large multicentric trials and registries are necessary to improve care, and to answer important clinical questions, emphasizing the need to shift from analysis of experiences of single centres to multi-centric and multi-disciplinary collaboration.