β-Adrenergic Blockade in Children

Antihypertensive agents: a long way to safe drug prescribing in children

Recently updated clinical guidelines have highlighted the gaps in our understanding and management of pediatric hypertension. With increased recognition and diagnosis of pediatric hypertension, the use of antihypertensive agents is also likely to increase. Drug selection to treat hypertension in the pediatric patient population remains challenging. This is primarily due to a lack of large, well-designed pediatric safety and efficacy trials, limited understanding of pharmacokinetics in children, and unknown risk of prolonged exposure to antihypertensive therapies. With newer legislation providing financial incentives for conducting clinical trials in children, along with publication of pediatric-focused guidelines, literature available for antihypertensive agents in pediatrics has increased over the last 20 years. The objective of this article is to review the literature for safety and efficacy of commonly prescribed antihypertensive agents in pediatrics. Thus far, the most data to support use in children was found for angiotensin-converting enzyme inhibitors (ACE-I), angiotensin receptor blockers (ARB), and calcium channel blockers (CCB). Several gaps were noted in the literature, particularly for beta blockers, vasodilators, and the long-term safety profile of antihypertensive agents in children. Further clinical trials are needed to guide safe and effective prescribing in the pediatric population.

β-Adrenergic blockade in cardiovascular disease

The development and subsequent clinical application of the β-adrenergic receptor blocking drugs represent one of the major advances in human pharmacotherapeutics. No other class of synthetic drugs has demonstrated such widespread therapeutic utility for the treatment and prevention of so many cardiovascular diseases. In addition, these drugs have proven to be molecular probes that have contributed to our understanding of the disease, and on the molecular level, both the structure and function of the 7 transmembrane G protein receptors that mediate the actions of many different hormones, neurotransmitters, and drugs. The evolution of β-blocker drug development has led to refinements in their pharmacodynamic actions that include agents with relative β1-selectivity, partial agonist activity, concomitant α-adrenergic blockers activity, and direct vasodilator activity. In addition, long-acting and ultra-short-acting formulations of β-blockers have also demonstrated a remarkable record of clinical safety in patients of all ages.

Effect of preoperative use of propranolol on postoperative outcome in patients with tetralogy of Fallot

The aim of this study was to determine if preoperative propranolol therapy has a deleterious effect on postoperative variables in patients with tetralogy of Fallot. Data from 97 patients who underwent complete repair of tetralogy of Fallot were reviewed. The patients were divided into 2 groups: those receiving preoperative propranolol therapy (n = 32) and those not receiving therapy (n = 65). Preoperative and intraoperative variables did not differ between groups. There were no differences in postoperative inotrope scores on arrival to the intensive care unit and through the first 12 hours postoperatively. There was a trend toward increased inotrope scores at 24 hours (median 8 vs 5, p = 0.05) and 48 hours (median 8 vs 3, p = 0.05) postoperatively in the patients treated with propranolol. Temporary pacing in the early postoperative period occurred more often in the propranolol group (16% vs 3%, p = 0.04). There was no difference between groups in length of mechanical ventilation, intensive care unit stay, or total hospital postoperative stay. In conclusion, propranolol therapy can be used in patients with tetralogy of Fallot until the time of surgery, without important effects on their postoperative courses. Any blunting of inotropic or chronotropic activity in propranolol-treated patients appears to be easily overcome with increased inotropic medications or temporary pacing, without increased morbidity or mortality.

Pharmacologic treatment of chronic pediatric hypertension

Improved recognition of the relationship between childhood and adult blood pressures and identification of end-organ damage in children, adolescents, and young adults with hypertension has led to increased focus by pediatricians and general practitioners on the detection, evaluation, and treatment of hypertension. Notably, detection, evaluation, and treatment of pediatric hypertension has increased significantly since the first Task Force Report on High Blood Pressure in Children and Adolescents in 1977 with advances in both nonpharmacologic and pharmacologic treatments.Angiotensin-converting enzyme inhibitors (e.g. captopril, enalapril, lisinopril, ramipril) and calcium channel antagonists (e.g. nifedipine, amlodipine, felodipine, isradipine) are the most commonly prescribed antihypertensive medications in children due to their low adverse-effect profiles. Diuretics (e.g. thiazide diuretics, loop diuretics, and potassium-sparing diuretics) are usually reserved as adjunct therapy. Newer agents, such as angiotensin receptor antagonists (e.g. irbesartan), are currently being studied in children and adolescents. These agents may be an option in children with chronic cough secondary to angiotensin-converting enzyme inhibitors. beta-Adrenoreceptor antagonists (e.g. propranolol, atenolol, metoprolol, and labetalol), alpha-adrenoreceptor antagonists, alpha-adrenoreceptor agonists, direct vasodilators, peripheral adrenoreceptor neuron agonists, and combination products are less commonly used in pediatric patients because of adverse events but may be an option in children unresponsive to calcium channel blockers, angiotensin converting-enzyme inhibitors, or angiotensin receptor blockers.

Cost-effectiveness and implications of newborn screening for prolongation of QT interval for the prevention of sudden infant death syndrome

OBJECTIVE

To determine the cost-effectiveness of universal and high-risk neonatal electrocardiographic (ECG) screening for QT prolongation as a predictor of sudden infant death syndrome (SIDS) risk in a theoretical group of neonates.

STUDY DESIGN

Incremental cost-effectiveness analysis with decision analytic modeling. A hypothetical cohort of healthy, term infants was modeled, comparing options of no screening, high-risk neonate screening, and universal screening. The high-risk strategy is speculative, because no currently accepted methodology is known for identifying infants at high risk for SIDS. Given the uncertain mechanisms of association between prolonged corrected QT interval (QTc) and SIDS, analyses were repeated under different assumptions. Sensitivity analyses were also performed on all input variables for both costs and effectiveness.

RESULTS

Under the assumption that neonatal electrocardiographic screening detects long QT syndrome responsive to conventional therapy, the cost-effectiveness of high-risk screening was $3403 per life year gained, whereas universal screening cost $18,465 per additional life year gained. However, if the effectiveness of SIDS therapy falls below 10%, the cost-effectiveness deteriorates to $28,376 per life year saved for the high-risk strategy and $118,900 for universal screening. The analyses were robust to a broad array of sensitivity analyses.

CONCLUSIONS

The acceptability of the cost-effectiveness of neonatal electrocardiographic screening is heavily dependent on the pathophysiologic mechanism of SIDS and on the efficacy of monitoring and antiarrhythmic treatment. The nature of this association must be elucidated before routine neonatal electrocardiographic screening is warranted.

Treatment of pediatric hypertension

We conducted a MEDLINE search from January 1966-March 1999 to obtain information on clinical trials of treatment of pediatric hypertension. An article was selected for review if it described a randomized or nonrandomized study; randomized studies were given priority. Case reports were considered when studies were unavailable. Review articles were useful in identifying references. According to data we collected, hypertension is present in 1-3% of the pediatric population. Nonpharmacologic treatment may be effective initially in those with mild to moderate disease or as an adjunct to drug therapy. Drugs for treatment of chronic hypertension include calcium channel blockers, angiotensin-converting enzyme inhibitors, diuretics, and beta-blockers. Patient and drug characteristics determine therapy. Intravenous labetalol, nicardipine, and nitroprusside are effective for treating hypertensive emergencies.