Pharmacodynamics and pharmacokinetics of esmolol, a short-acting beta-blocking agent, in children

Pediatric antiarrhythmics and toxicity: A clinical review

Antiarrhythmic medications are fundamental in the acute and chronic management of pediatric arrhythmias. Particularly in the pediatric patient population, associated antiarrhythmic toxicities represent important potential adverse effects. Emergency medicine clinicians must be skilled in the detection, workup, and management of antiarrhythmic toxicity. This is a clinical review of the indications, pharmacology, adverse effects, and toxicologic treatment of antiarrhythmics commonly used in the pediatric patient population.

PICU Pharmacology

The care of the critically-ill child often includes medications used to optimize organ function, treat infections, and provide comfort. Pediatric pharmacology has some key differences that should be leveraged for safe pharmacologic management.

Use of an ultrashort-acting selective β1-adrenergic receptor antagonist esmolol in ear, nose and throat surgery

Background / Aim: The concept of general balanced anaesthesia was devised in order to assure cardiovascular stability and fast post-anaesthesia recovery. This clinical trial was organised in order to investigate the parameters of cardiovascular function and emergence from anaesthesia in elective ear, nose and throat (ENT) surgery patients. Methods: A total of 40 ASA I and II patients of both sexes scheduled for elective ENT surgery were randomly divided into two equal groups. Both groups received a continuous IV infusion of glucose 5 % solution and in the esmolol group this infusion also contained esmolol. Esmolol infusion rate was 0.3 mg/kg/min during the first 5 min and thereafter 0.1 mg/kg/min. In critical phases of anaesthesia and operation (induction, intubation, first incision, surgical manipulations, wound suture, extubation), systolic and diastolic blood pressure were monitored. Recovery after anaesthesia was assessed based on times of eye opening on command, spontaneous eye opening and regaining of full orientation. Increases in cardiovascular parameters by 20 % of the baseline values or more were treated with IV boluses of fentanyl, alone or with droperidol and, if necessary, by adding isoflurane 0.5 % to the inhalational mixture. Consumption of drugs was recorded. Results: Esmolol assured stable values of cardiovascular parameters that were in most critical phases of anaesthesia and operation lower than in the control group. The duration of anaesthesia did not differ between the groups. In the esmolol group, lower consumption of fentanyl, droperidol and sevoflurane was registered. Patients in the esmolol group emerged from anaesthesia faster than patients in the control group. Conclusion: Continuous IV infusion of esmolol assures better cardiovascular stability, necessitates lower consumption of analgesics and anaesthetics and results in faster emergence from general anaesthesia in elective ENT surgery.

Esmolol as an adjunct to general balanced anaesthesia in neurosurgery

Background/Aim: In surgery, and especially in the neurosurgical operations, maintenance of cardiovascular stability during and in the phase of the immediate postoperative recovery is of vital importance. The aim of this study was to investigate the effects of continuous esmolol infusion on the values of cardiovascular parameters and quality of the emergence from anaesthesia in neurosurgical patients. Methods: A total of 40 patients of both sexes scheduled for elective supratentorial surgery were randomly assigned to two groups. Esmolol group received intravenous (iv) infusion of esmolol dissolved in 5 % glucose solution (during the first 5 min at a rate of 0.3 mg/kg/min and thereafter at a rate of 0.1 mg/kg/min), while the ones from the control group received a 5 % glucose solution without esmolol at the same volume and rate. Cardiovascular parameters were registered at critical phases of anaesthesia and operation (induction, intubation, placement of Mayfield frame, craniotomy, skull closure, extubation). Recovery after anaesthesia was assessed based on times of eye opening on command, spontaneous eye opening and regaining of full orientation. Results: Values of systolic blood pressure and heart rate were significantly lower in the esmolol than in the control group of patients. Although the durations of anaesthesia did not differ, patients from the esmolol group required significantly less opioids and isoflurane and recovered after the anaesthesia significantly faster than the patients in the control group. Conclusion: Ultrashort-acting beta-adrenergic receptor antagonist esmolol, administered as a continuous iv infusion, assures better cardiovascular stability and smoother emergence from the balanced inhalation general anaesthesia than the control glucose infusion in elective neurosurgical patients.

Pharmacologic Control of Blood Pressure in Infants and Children

Alterations in blood pressure are common during the perioperative period in infants and children. Perioperative hypertension may be the result of renal failure, volume overload, or activation of the sympathetic nervous system. Concerns regarding end-organ effects or postoperative bleeding may mandate regulation of blood pressure. During the perioperative period, various pharmacologic agents have been used for blood pressure control including sodium nitroprusside, nitroglycerin, β-adrenergic antagonists, fenoldopam, and calcium channel antagonists. The following manuscript outlines the commonly used pharmacologic agents for perioperative BP including dosing regimens and adverse effect profiles. Previously published clinical trials are discussed and efficacy in the perioperative period reviewed.

Management of Supraventricular Tachycardia in Infants

Supraventricular tachycardia is the most common tachyarrhythmia encountered in infants. In older children and adults, definitive treatment of the supraventricular tachycardia substrate with catheter ablation is a common approach to management. However, in infants, the risks of catheter ablation are significantly higher, and the patients often outgrow the potential to experience episodes. Therefore, antiarrhythmic medications are often utilized to minimize the likelihood of experiencing episodes. This article reviews the common arrhythmia mechanisms encountered in infants and the medications used to treat these patients.

Evaluation and treatment of hypertensive crises in children

Hypertensive crises in children are medical emergencies that must be identified, evaluated, and treated promptly and appropriately to prevent end-organ injury and even death. Treatment in the acute setting typically includes continuous intravenous antihypertensive medications with monitoring in the intensive care unit setting. Medications commonly used to treat severe hypertension have been poorly studied in children. Dosing guidelines are available, although few pediatric-specific trials have been conducted to facilitate evidence-based therapy. Regardless of what medication is used, blood pressure should be lowered gradually to allow for accommodation of autoregulatory mechanisms and to prevent cerebral ischemia. Determining the underlying cause of the blood pressure elevation may be helpful in guiding therapy.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Antihypertensives

OBJECTIVE

Hypertension remains a common condition in pediatric cardiac intensive care. The physiologic effects of hypertension in this population are complex and are impacted by patient age, comorbidities, and primary cardiac disease. The objective of this study is to review current pharmacotherapies for the management of systemic hypertension in the pediatric cardiac ICU.

DATA SOURCES

Relevant literature to the treatment of systemic hypertension in children was included. Specific focus was given to literature studying the use of therapies in critically ill children and those with heart disease. Reference textbooks and drug packaging inserts were used for drug-specific pediatric guidelines.

STUDY SELECTION

A search of MEDLINE, PubMed, and the Cochrane Database was performed to find literature about the management of hypertension in children. Metaanalyses and pediatric-specific studies were primarily considered and cross-referenced. Pertinent adult studies were included.

DATA EXTRACTION

Once the studies for inclusion were finalized, priority for data extraction was given to pediatric-specific studies that focused on children with heart disease and critical illness.

CONCLUSIONS

Systemic hypertension is common, and there is significant heterogeneity in the patient population with critical heart disease. There are limited large, prospective analyses of safety and efficacy for pediatric drug antihypertensive agents. Despite patient heterogeneity, most pharmacotherapies are safe and efficacious.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Antiarrhythmics

OBJECTIVE

Arrhythmias are a common occurrence in critically ill pediatric patients. Pharmacotherapy is a usual modality for treatment and prevention of arrhythmias in this patient population. This review will highlight particular arrhythmias in the pediatric critical care population and discuss salient points of pharmacotherapy of these arrhythmias. The mechanisms of action for the various agents, potential adverse events, place in therapy, and evidence for their use will be summarized.

DATA SOURCES

The literature was searched for articles related to the topic. Expertise of the authors and a consensus of the editors were additional sources of data in the article.

DATA SYNTHESIS

The author team synthesized the current pharmacology and recommendations and present them in this review. Tables were generated to summarize the state of the art evidence-based practice.

CONCLUSION

Specialized knowledge as to the safe and effective use of the antiarrhythmic pharmacotherapy in the intensive care setting can lead to safe and effective rhythm management in patients with complex heart disease.

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.

Drug treatment of hypertensive crisis in children

Hypertensive crisis is a relatively rare event and is associated with significant morbidity and mortality in adults and pediatric patients alike. Rapid, safe, and effective treatment is imperative to alleviate immediate presenting clinical symptoms, prevent devastating morbidity, preserve long-term quality of life, and prevent mortality. Many medications in the hypertensive crisis arsenal have been used for nearly half a century. Nearly all treatment options have been utilized in children for decades, yet reliable data and sound clinical literature remain elusive. Every agent considered to be a first-line, second-line, or adjunctive option has yet to be evaluated in a randomized controlled trial in pediatric patients. With a paucity of clinical data to form evidence-based decisions, the clinician must rely entirely on the extrapolation from adult data and small retrospective studies, case series, and case reports of medication use in pediatric patients. Although more research in the treatment of pediatric hypertensive crisis is desperately needed, current practice demands a sharp knowledge of the pediatric clinical literature and pharmacology in this area as an essential tool to consistently improve patient outcomes with respect to morbidity and mortality.

The safety, efficacy, and pharmacokinetics of esmolol for blood pressure control immediately after repair of coarctation of the aorta in infants and children: a multicenter, double-blind, randomized trial

OBJECTIVES

Blood pressure control is important after repair of coarctation of the aorta. We report the first prospective multi-institutional trial addressing the safety and efficacy of esmolol after repair of coarctation of the aorta in infants and children.

METHODS

The primary objective of this phase IIIb, multicenter, double-blind, randomized, dose-ranging trial was the efficacy of esmolol to control hypertension. Candidates included subjects younger than 6 years and weighing 2.5 kg or more who underwent surgical intervention for coarctation of the aorta and required therapy for systemic hypertension. One hundred sixteen subjects received esmolol: 36 received a low dose (125 microg/kg), 43 received a medium dose (250 microg/kg), and 37 received a high dose (500 microg/kg). The primary outcomes were the change in systolic blood pressure and the need for additional antihypertensive rescue medication 5 minutes after the initiation of esmolol.

RESULTS

All dose groups showed a significant decrease from baseline in systolic blood pressure (-9.6 +/- 16.3 mm Hg, P < .001). There were no differences in systolic blood pressure response at 5 minutes between dose groups (high, medium, or low) or age groups. The need for rescue medication at 5 minutes was not different between dose groups. All dose groups showed similar incidences of adverse events. There were no serious adverse events.

DISCUSSION

Esmolol can be administered safely to patients younger than 6 years after repair of coarctation of the aorta. In the dose range of 125 to 500 microg/kg, esmolol significantly decreased systolic blood pressure.

The pharmacokinetics of esmolol in pediatric subjects with supraventricular arrhythmias

Esmolol is often used in the acute management of children with arrhythmias and/or hypertension; however, pharmacokinetic studies of the drug in children have been limited. The objective of this study was to determine the pharmacokinetics of esmolol in children with a history of supraventricular arrhythmias (SVT) who were scheduled for diagnostic electrophysiology study or a catheter ablation procedure. Subjects were stratified into two age groups: 2-11 and 12-16 years. After an episode of stimulated or spontaneous SVT, esmolol was administered intravenously as a 1,000 microg/kg bolus followed by continuous infusion at 300 microg/kg/min. Blood samples were collected before, at 5, 10 and 15 min after the loading dose, and 3, 6, 9, 12, 15 and 20 min after the end of the infusion. Plasma concentration of esmolol was quantitated by a specific LC/MS assay. Pharmacokinetic data were available for 25 subjects. Arterial esmolol concentrations were approximately five times greater than venous concentrations. Esmolol had an extremely short distribution half-life (0.6 min), a rapid terminal elimination half-life (6.9 min), and a rapid clearance (119 +/- 51 mL/min/kg) which was not related to subject age or weight. Seventeen of the subjects (63%) converted to normal sinus rhythm in an average of 2 min (range 0-5 min). The pharmacokinetics of esmolol and its efficacy in terminating SVT in children is similar to that observed in adults.

Advances in the pathogenesis and management of hypertensive crisis

PURPOSE OF REVIEW

This review summarizes recent insights into to the pathophysiology of hypertensive crisis with the emphasis on newly discovered molecular mechanisms underlying hypertension and also updates current therapeutic options for treating hypertensive crisis in children.

RECENT FINDINGS

There is growing evidence that the renin-angiotensin system plays a key role in the pathogenesis of hypertensive crises. Recent studies have shown that oxidative stress and factors affecting endothelial function are also important. Treatment of hypertensive crisis still focuses on lowering of blood pressure in an expeditious but safe manner. There is growing experience with IV nicardipine, which is becoming a viable alternative to sodium nitroprusside in children.

SUMMARY

Current knowledge of hypertensive crisis emphasizes the need for additional animal and translational studies with the goal of identifying the underlying molecular pathogenesis and developing new therapies to optimize future treatment of hypertensive emergencies.

Liquid chromatography-electrospray mass spectrometry (LC-MS) method for determination of esmolol concentration in human plasma

Esmolol is a very short-acting beta-blocker commonly used in critically ill patients. To study the pharmacokinetics of esmolol in pediatric patients, a liquid chromatography-electrospray mass spectrometry (LC-MS) method to quantitate esmolol concentration in plasma was developed. Following methylene chloride extraction from 200 microl aliquots of plasma containing internal standard and reconstitution in 0.05% formic acid, 10 microl are injected onto column, eluted using a methanol/formic acid gradient over 15 min, and monitored with selected ion recording at 296.2 and 282.2. The assay is linear between 2 and 1000 ng/ml. The intra-day and inter-day coefficients of variation are less than 8 and 10%, respectively.

Successful treatment of long QT syndrome-induced ventricular tachycardia with esmolol

Esmolol is a cardioselective beta-blocker with very rapid onset of action and short half-life due to its metabolism by blood-borne esterases. This unique profile among currently available beta-blockers renders esmolol highly useful in critical care situations. However, published experience with the use of esmolol in critically ill children is scant. The case of a 4-year-old boy with secondary long QT syndrome and ventricular tachycardia successfully treated with esmolol is presented.

Esmolol for the management of pediatric hypertension after cardiac operations

OBJECTIVE

Hypertension frequently occurs during the immediate postoperative period in children after repair of aortic coarctation but may also occur after repair of other congenital heart defects. Nitroprusside has often been used to control blood pressure in this setting. Because hypertension after coarctation repair is frequently associated with elevations in catecholamines, esmolol, a short-acting beta-blocking agent, may be an effective alternative. Therefore we undertook the first systematic investigation to determine the efficacy and disposition of esmolol in pediatric patients with acute hypertension after cardiac operations.

METHODS

Twenty patients aged 1 month to 12 years (median 25.6 months) with acute hypertension after cardiac operations received esmolol in an opened-labeled trial. Esmolol was titrated to a blood pressure less than or equal to the 90th percentile for age.

RESULTS

Ten patients had coarctation repair and the remaining patients underwent repair of other congenital heart defects. On final esmolol dose (mean +/- standard deviation dosage 700 +/- 232 microg/kg/min) there was a significant percent decrease in heart rate and systolic and diastolic blood pressures from postoperative values. Esmolol dose was significantly associated with percent reduction in systolic blood pressure. Final esmolol dose and total body clearance were significantly higher in patients after coarctation repair. There were significant associations between esmolol dose and esmolol blood concentrations at steady state.

CONCLUSIONS

The dosage required to control hypertension in patients after repair of aortic coarctation was higher than patients who underwent repair of other congenital heart defects. Esmolol was effective in controlling blood pressure in 19 of 20 patients without adverse effects.