Nicardipine: perioperative applications in children

Managing severe hypertension in children

Severe childhood hypertension is uncommon and frequently not recognised and is best defined as a systolic blood pressure (SBP) above the stage 2 threshold of the 95th centile + 12 mmHg. If no signs of end-organ damage are present, this is urgent hypertension which can be managed by the slow introduction of oral or sublingual medication, but if signs are present, the child has emergency hypertension (or hypertensive encephalopathy if they include irritability, visual impairment, fits, coma, or facial palsy), and treatment must be started promptly to prevent progression to permanent neurological damage or death. However, detailed evidence from case series shows that the SBP must be lowered in a controlled manner over about 2 days by infusing short-acting intravenous hypotensive agents, with saline boluses ready in case of overshoot, unless the child had documented normotension within the last day. This is because sustained hypertension may increase pressure thresholds of cerebrovascular autoregulation which take time to reverse. A recent PICU study that suggested otherwise was significantly flawed. The target is to reduce the admission SBP by its excess, to just above the 95th centile, in three equal steps lasting about ≥ 6 h, 12 h, and finally ≥ 24 h, before introducing oral therapy. Few of the current clinical guidelines are comprehensive, and some advise reducing the SBP by a fixed percentage, which may be dangerous and has no evidence base. This review suggests criteria for future guidelines and argues that these should be evaluated by establishing prospective national or international databases.

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.

Clevidipine for perioperative blood pressure control in infants and children

Various pharmacologic agents have been used for perioperative BP control in pediatric patients, including sodium nitroprusside, nitroglycerin, β-adrenergic antagonists, fenoldopam, and calcium channel antagonists. Of the calcium antagonists, the majority of the clinical experience remains with the dihydropyridine nicardipine. Clevidipine is a short-acting, intravenous calcium channel antagonist of the dihydropyridine class. It undergoes rapid metabolism by non-specific blood and tissue esterases with a half-life of less than 1 minute. As a dihydropyridine, its cellular and end-organ effects parallel those of nicardipine. The clevidipine trials in the adult population have demonstrated efficacy in rapidly controlling BP in various clinical scenarios with a favorable adverse effect profile similar to nicardipine. Data from large clinical trials regarding the safety and efficacy of clevidipine in children is lacking. This manuscript aims to review the commonly used pharmacologic agents for perioperative BP control in children, discuss the role of calcium channel antagonists such as nicardipine, and outline the preliminary data regarding clevidipine in the pediatric population.

The management of hypertensive emergencies in children after stem cell transplantation

AIM OF THE REVIEW

This work presents a short overview on the available data about drugs that are currently used to treat hypertensive emergencies in children with a focus on incidents after stem cell transplantation. It shows that the pediatric use of all hypotensive agents appears to be mainly based on personal experience of the attending physicians rather than on convincing clinical trials.

METHOD

A literature search was performed in MEDLINE, through PubMed, using the medical subject headings (MeSH) hypertensive emergencies, nifedipine, nicardipine, and children. Further articles were identified by checking cross-references of articles and books.

RESULTS

Hypertensive emergencies in children after stem cell transplantation usually have a renal etiology, because of the treatment with the calcineurin inhibitors cyclosporine and tacrolimus. In these severe cases an immediate action is necessary to avoid possible appearance or exacerbation of endorgan damage. Because of their mechanism of action and a potential nephroprotective effect calcium channel blockers may be particularly suitable in cases of hypertensive emergencies. An intravenous application of nifedipine may compensate the difficulties of accurate dosing, but keeping in mind possible severe side effects and the lack of published experience its use in children is at least questionable. Nicardipine appears to be the hypotensive agent of first choice. In adults, the treatment of hypertensive emergencies with intravenous nicardipine is well-documented, but for an evaluation of safety in pediatric use, the published studies and case reports appear to be barely adequate.

CONCLUSION

The actual treatment approaches vary widely, demonstrating the lack of hard science on which current treatment of hypertensive emergencies in children is based. The hypotensive agent for the individual situation should be chosen considering the properties, side effects, the limited experiences with its use and the patient's anamnesis.

A review of calcium channel antagonists in the treatment of pediatric hypertension

All children aged > or = 3 years should have an annual blood pressure (BP) measurement taken during a routine physical examination. Physicians should become familiar with recommended pediatric normative BP tables. BP above the 95th percentile may require drug therapy. There are several categories of antihypertensives available to the clinician. Calcium channel antagonists (CCAs) are a class of drugs that exert their antihypertensive effect by inhibiting the influx of calcium ions across the cell membranes. This results in dilatation of peripheral arterioles. When given orally, CCAs are metabolised in the liver by cytochrome P450 (CYP) enzyme CYP3A4; hence, some CCAs will affect the half-life of drugs that share this enzyme system for their metabolism. CCAs can be safely used in children with renal insufficiency or failure and as a general rule there is no need to modify drug dosage in this population. CCAs are generally well tolerated; most adverse effects appear to be dose related. Headache, flushing, gastrointestinal upset, and edema of the lower extremities are the most common symptoms reported with the use of CCAs. Pediatric data regarding safety and efficacy of CCAs have mostly been obtained from retrospective analyses. Extended-release nifedipine and amlodipine are the two most commonly used oral CCAs in the management of pediatric hypertension. These drugs can be given once a day, although many children require twice-daily administration. Extended-release nifedipine has to be swallowed whole; hence, its use in younger children who cannot swallow pills is limited. Amlodipine can be made into a solution without compromising its long duration of action; therefore, it is the CCA of choice for very young children. Oral short-acting nifedipine and intravenous nicardipine are safe and effective CCAs for the management of hypertensive crisis in children. Short-acting nifedipine can cause unpredictable changes in BP; hence, it should be used cautiously and in low doses. Intravenous nicardipine has a rapid onset of action and a short half-life. Intravenous infusion of nicardipine can be titrated for effective control of BP. Intravenous nicardipine has been used safely in hospitalized children and newborns for the management of hypertensive crisis, and for controlled hypotension during surgery. CCAs are a class of antihypertensives that are safe and effective in pediatric patients. They have relatively few adverse effects and are well tolerated by children. This article reviews CCAs as antihypertensives in the management of pediatric hypertension.

Preliminary Experience with Amlodipine in the Pediatric Population

The authors retrospectively examined their experience with amlodipine in the treatment of hypertension in 32 pediatric-aged patients, ranging in age from 4 to 26 years, with blood pressure (BP) readings greater than the 90th percentile for age. Amlodipine was used as the sole therapy in 9 patients and with other antihypertensive therapy in 23 patients. Additional antihypertensive drugs used in combination with amlodipine included beta-adrenergic antagonists, ACE inhibitors, and diuretics. The starting dose of amlodipine was 0.13+/-0.09 mg/kg/d. The dose was increased in 20 of 32 patients to 0.23+/-0.13 mg/kg/d. Amlodipine was administered once daily to 26 patients and twice daily to 6 patients. After therapy with amlodipine was initiated, the systolic BP decreased from 141+/-15 to 132+/-9 mm Hg (P=0.01) and the diastolic BP decreased from 84+/-16 to 77+/-8 mmHg (P=0,03). There were a total of 2145 follow-up BP readings. The follow-up systolic BP was lower than the initial BP prior to starting amlodipine 59% of the time and the diastolic BP was lower than the initial BP 61% of the time. The follow-up systolic BP was lower than the 90th percentile predicted for age 33% of the time after starting amlodipine and the diastolic BF was lower than the 90th percentile for age 52% of the time. Adverse effects were noted in 4 of the 32 patients (12.5%). These included fatigue (n=2), dizziness (n=1), and ankle edema (n=1). Amlodipine therapy was discontinued in only 1 patient (the patient with ankle edema). Given its efficacy, the low incidence of adverse effects, and availability as a suspension, amlodipine is an effective agent for the treatment of hypertension in the pediatric-aged patient.

Intravenous nicardipine for treatment of postcoarctectomy hypertension in children

Our objective was to evaluate the efficacy of intravenous (IV) nicardipine for the treatment of postcoarctectomy hypertension in children with coarctation of the aorta. We carried out a retrospective review in a pediatric intensive care unit at a tertiary care children's hospital. The patients were children with coarctation of the aorta treated for postcoarctectomy hypertension. Children with postcoarctectomy hypertension defined as a systolic blood pressure >95th percentile for age measured by indwelling arterial catheter were treated with IV nicardipine. We measured change in mean arterial blood pressure (MAP), mean systolic and diastolic blood pressure, and mean heart rate (HR) from baseline after initiating treatment with IV nicardipine. The outcome measure was a reduction in MAP and mean systolic and diastolic blood pressure after treatment with IV nicardipine. During a 4-year period, 10 children met the study criteria. Median age was 3.25 months (range, 0.25 to 180 months). Initial median treatment dose of IV nicardipine was 1.0 micro g/kg/min (range, 0.5 to 6 micro g/kg/min); median dose used to control hypertension was 1.5 micro g/kg/min (range, 0.25 to 6 micro g/kg/min). Median duration of therapy was 26.3 h (range, 13 to 49 h). Treatment with IV nicardipine resulted in a 26.5% decrease in MAP from baseline during the first hour of treatment ( p = 0.0006). Mean systolic blood pressure decreased from 133 to 105 mmHg ( p = 0.005), and mean diastolic blood pressure decreased from 75 to 52.5 mmHg ( p = 0.001) during the first hour of therapy with nicardipine. There was a significant reduction ( p = 0.0005) in MAP during continued treatment with IV nicardipine. The mean HR of 150 remained unchanged during the first hour of therapy with nicardipine, and no significant change in mean HR or adverse effects was noted during continued therapy. Two children receiving other antihypertensive therapy demonstrated further reduction in their blood pressure when IV nicardipine was initiated. Tachycardia and hypotension were not observed in any child treated with IV nicardipine. We concluded that IV nicardipine reduced MAP with no significant change in mean HR and no adverse effects in patients with postcoarctectomy hypertension. Nicardipine produced a further reduction in MAP in children receiving other antihypertensive agents. Nicardipine is an effective agent for treatment of postcoarctectomy hypertension in children with coarctation of the aorta.

Nicardipine to control mean arterial pressure after cardiothoracic surgery in infants and children

Nicardipine is the first intravenously administered dihydropyridine calcium channel blocker. Its primary physiologic action includes vasodilatation with limited effects on the inotropic and dromotropic function of the myocardium. Several previous reports document its use in adult patients for pharmacologic control of blood pressure. The current report describes the use of nicardipine to control mean arterial pressure (MAP) in nine infants and children after cardiothoracic surgical procedures. The patients ranged in age from 6 days to 9 years (mean, 3.3 +/- 4.1 years) and in weight from 4.1 to 49 kg (mean, 15.3 +/- 14.4). The surgical procedures included aortic coarctation repair (three), repair of tetralogy of Fallot (two), arterial switch for transposition of the great vessels (two), pulmonary valvotomy (one), and aortic valvotomy (one). The target systolic blood pressure was 90 mm Hg in patients younger than 4 years of age and < or = 110 mm Hg in patients 5 years of age or older. The nicardipine infusion was started at 5 microg/kg/min in all patients. The target blood pressure was achieved within 15 minutes in eight of nine patients. One patient required an initial infusion rate of 10 microg/kg/min to achieve the target blood pressure. The maintenance infusion rate varied from 2.5 to 5.5 mcg/k/min (mean 3.0 +/- 1.1). The duration of the infusion varied from 30 to 42 hours (mean, 37.4 +/- 4.2). In the nine patients, nicardipine was infused for a total of 337 hours. No adverse effects such as excessive hypotension were noted. Nicardipine is an effective agent for controlling MAP after cardiothoracic surgical procedures in infants and children.

The perioperative management of children with phaeochromocytoma

The safe anaesthetic management of a child with a phaeochromocytoma requires an understanding of the pathophysiology of the disease, together with a thorough knowledge of its pharmacology, in order to avoid or minimize the potentially harmful cardiovascular changes that may occur during anaesthesia. Although there is a considerable amount of information on the management of the adult with phaeochromocytoma, much less has been written concerning children with the disease. Children differ significantly from adults in the incidence, location, presentation and management of this condition and these differences are discussed here together with some of the more controversial issues of management.

Nicardipine is a safe and effective agent in pediatric hypertensive emergencies

Nicardipine is the first dihydropyridine calcium channel blocker capable of intravenous administration. Seven pediatric patients with hypertensive emergencies attributable to various pathological processes were treated with intravenous nicardipine, starting at 1 microg/kg/min. Nicardipine appeared to be safe and effective in controlling hypertension in these patients. Two patients who received nicardipine through peripheral lines developed superficial thrombophlebitis. None of the five patients receiving nicardipine through a central line experienced phlebitis, and no other adverse effects were noted.

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.