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Hypertension and Hypertensive Crisis in Children

                                                             
 

Acute Hypertension and Hypertensive Crisis in Children

               Dr  A. George Koshy, Govt Medical College ,Thiruvananthapuram

 

Introduction:

Pediatric Hypertension is defined as systolic or diastolic blood pressure (BP) exceeding the 95th percentile for gender, age and height. The risk of hypertension increases with the Body Mass Index (BMI). Approximately 30% of children with BMI greater than 95th percentile have hypertension. The spectrum of hypertension that presents to the Emergency Department ranges from mild and asymptomatic to a true hypertensive emergency. 
A definition of hypertension ideally is based on a threshold level of blood pressure that divides those at risk for adverse outcomes from those who have no increased risk. The important conclusions of the fourth report on the diagnosis, evaluation and treatment of high blood pressure in children and adolescents of The National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. (Pediatrics 2004; 114: 555-576) are as follows:

• Hypertension is defined as average systolic and /or diastolic blood pressure >95th percentile for gender, age and height on > 3 occasions.
• Pre hypertension is defined as average systolic or diastolic pressures between 90- 95th percentile. These children should be observed carefully and evaluated if risk factors like obesity are present; tracking data suggest that this subgroup is more likely to develop overt hypertension over time than normotensive children.
• Adolescents with blood pressure levels more than 120/80 mm Hg should be considered pre hypertensive.
• A patient with blood pressure levels >95th percentile in a physician’s office or clinic, who is normotensive outside a clinical setting, has white-coat hypertension. Ambulatory blood pressure monitoring is helpful for confirmation.
• If the blood pressure is >95th percentile, it should be staged. If stage 1 (95th percentile to the 99th percentile plus 5 mm Hg), measurements should be repeated on 2 more occasions. If hypertension is confirmed, evaluation should proceed. If blood pressure is stage 2 (>99th percentile plus 5 mm Hg), prompt referral should be made for evaluation and therapy. If the patient is symptomatic, immediate referral and treatment are indicated.

• All children should have yearly blood pressure evaluation beyond 3 years of age. There is an increased risk of hypertension in children with history of hypertension in family members, those who are obese, had IUGR or have urinary infections and renal scars.

Evaluation:

When confronted with newly diagnosed hypertension in the child, the physician should consider three important issues: 1) Is the hypertension primary or secondary? 2) Is there evidence of target organ damage? and 3) Are there associated risk factors that would worsen the prognosis if the hypertension were not treated immediately?.
A brief, but careful history and physical examination should be performed. Some key features in the history would be the duration and onset of hypertension, degree of compliance with any drug therapy, and possibility of renal disease (any history of urinary tract infections, hematuria, edema, or umbilical artery catheterization). One should also enquire for any history of joint pain, palpitations, weight loss, flushing, weakness, drug ingestion, headaches, nausea, vomiting and a family history of renal disease or hypertension.
After several determinations of the blood pressure, a focused physical examination should be performed immediately. One should check for any evidence of neurologic dysfunction and left ventricular dysfunction / cardiac failure. Fundoscopy should be performed looking for hemorrhage, infarcts or papilledema. The peripheral pulses should be palpated carefully. Weak and delayed femorals suggest coarctation of aorta. Any discrepancy in the upper and lower extremity BP measurements should be noted. The presence of an abdominal bruit suggests renovascular hypertension.
An improper cuff size can significantly record a wrong blood pressure. By convention, an appropriate cuff size is a cuff with an inflatable bladder width that is at least 40% of the arm circumference at a point midway between the olecranon and the acromion. For such a cuff to be optimal for an arm, the cuff bladder length should cover 80% to 100% of the circumference of the arm. Blood pressure measurements are overestimated to a greater degree with a cuff that is too small than they are underestimated by a cuff that is too large. If a cuff is too small, the next largest cuff should be used, even if it appears large

Etiology

Hypertension is usually described as primary (essential) or secondary due to a definable cause. The secondary cause will be found more likely when the patient is younger and hypertension is more severe. Most acute hypertension in childhood is due to glomerulonephritis. Chronic hypertension is commonly associated with renal parenchymal disease and only a small proportion have renovascular hypertension, pheochromocytoma or coarctation of the aorta . Late in the first decade and into the second decade of life, primary hypertension begins to predominate. Coarctation of the aorta accounts for one third cases of hypertension in neonatal period and infancy. Renovascular causes are amongst the curable forms of hypertension. 


Common causes of Hypertension in different age groups
 

 



Hypertensive Crisis in Children.

Hypertensive emergency is distinguished from hypertensive urgency by the presence of acute end-organ dysfunction discovered in the history, physical examination or investigations, and not by the height of the BP. 


Hypertensive Emergency

Hypertension associated with evidence of end-organ dysfunction constitutes hypertensive emergency. 
Malignant hypertension is characterized by marked elevations in systolic and/or diastolic BP (e.g., 160 mm Hg or higher systolic/ 105 mm Hg or higher diastolic for those less than 10 years of age; 170 mm Hg or higher systolic/ 110 mm Hg or higher diastolic for those more than 10 years of age) and is often associated with spasm and tortuosity of the retinal arteries, papilledema, and hemorrhages and exudates on fundoscopic examination.
Hypertensive encephalopathy(an example of hypertensive emergency) is seen often in malignant hypertension and consists of a combination of symptoms and signs that often vary from patient to patient (nausea, vomiting, headaches, altered mental status, visual disturbances, seizures, stroke). 

Patients with hypertensive emergency/ malignant hypertension usually are admitted to an intensive care unit for continuous cardiac monitoring and frequent assessment of neurologic status and urine output. An IV line is started for fluids and medications. Patients typically have altered blood pressure autoregulation, and overzealous reduction of blood pressure to reference range levels may result in organ hypoperfusion. The initial goal of therapy is to reduce the mean arterial pressure by approximately 25% over the first 8 to 12 hours. An intra- arterial line is helpful for continuous titration of blood pressure. Sodium and volume depletion may be severe, and volume expansion with isotonic sodium chloride must be considered. Urine output should be monitored from the outset. Any serious complications must be recognized and managed along with the treatment for hypertension. Anti convulsants should be administered to a child with seizure.

 

A number of medications are available for hypertensive emergencies. The choice of drugs depend on several factors such as the clinical condition of the patient, the presumed cause, whether there is a change in cardiac output or total peripheral resistance and whether there is end-organ involvement. It is important to select an agent with a rapid and predictable onset of action and to monitor the blood pressure carefully as is being reduced. Because hypertensive encephalopathy is a possible complication of hypertensive emergencies, antihypertensive agents with minimal CNS side effects should be chosen to avoid confusion between symptoms of disease and adverse effects of the drug. Centrally acting drugs like Alpha Methyl Dopa and Clonidine are usually not preferred because of the CNS side effects. Intravenous administration is generally preferred in order to carefully titrate the fall in blood pressure. Too rapid reduction in blood pressure can interfere with adequate organ perfusion and hence a stepwise reduction should be planned. Hypertensive emergencies should be treated by an intravenous antihypertensive that can produce a controlled reduction in the blood pressure, aiming to decrease the pressure by 25% over the first 8 hours after presentation and then gradually normalizing the BP over the next 48 hours. Each of the most commonly used medications offers distinct advantages and disadvantages and each clinical situation requires its own mode of management. However, some general guidelines are usually helpful.

Sodium nitroprusside is an arteriolar and venous vasodilator that is invariably effective. BP decreases with little change in cardiac output, and reflex tachycardia is not usually an important problem. It is administered by constant infusion. Its effect is immediate, and lasts only as long as the infusion is continued. Its use requires intensive observation and therefore may not be indicated in the ED. Other disadvantages are that the drug requires 10 minutes to prepare and is photosensitive, and there is a potential for cyanide accumulation. The infusion bottle and tubing should be covered and protected from light.

Diazoxide is an arteriolar vasodilator, has little effect on capacitance vessels and has no direct cardiac effect. It is very potent with a rapid onset, and the effect can be dramatic. It may provide a long duration of BP control (8 to 12 hours). It causes marked salt and water retention, and in patients with edema, it should be followed with a diuretic agent. It also causes reflex tachycardia and hyperglycemia.

Hydralazine is an arteriolar vasodilator that is not as potent as diazoxide or nitroprusside. However, it has an excellent safety profile. The half-life is short (3 to7 hours), necessitating frequent dosing. Reflex tachycardia often occurs, and may require the introduction of a beta blocker.

Labetalol is an alpha 1 and nonselective -adrenergic blocker. Dosing is independent of renal function. It has been reported to be effective in the management of severe hypertension that results from pheochromocytoma and coarctation of the aorta and is a reasonable alternative in the treatment
of hypertensive crises in patients with end stage renal disease.

Nifedipine, a calcium channel blocker, reduces peripheral vascular resistance and does not affect cardiac output. It can be administered sublingually, but biting the capsule and swallowing its contents achieves measurable blood levels more rapidly than the sublingual route. Its use depends on the patient’s state of consciousness. It is contraindicated in the presence of intracerebral bleeding.

Nicardipine, another calcium channel blocker is an excellent drug for use in emergencies, since it can be administered as an infusion that can be easily prepared and titrated.

Phentolamine is a pure -adrenergic blocker used almost exclusively for the treatment of catecholamine crisis (as seen in patients with pheochromocytoma or ingestion of sympathomimetic agents such as cocaine). The effect is immediate. There is a high risk of hypotension after 
the primary lesion (e.g. pheochromocytoma) is excised, and care should be exercised and the surgeons should be alerted to this possibility.
Most children with hypertensive crisis have chronic or acute renal disease. In these patients, management of blood pressure also requires careful attention to fluid balance and diuresis. Intravenous Frusemide is usually effective even though glomerular filtration may be impaired.


Hypertensive Urgency:

A hypertensive urgency is defined as severe hypertension without evidence of end-organ involvement. Patients with known hypertension who present in an urgent hypertensive crisis may not require hospitalization if the therapy in the emergency department is successful, and adequate follow-up can be ensured. Often, oral antihypertensive agents are sufficient, although there are occasions when parenteral therapy is indicated.

 




Other Drug Therapy:

Calcium channel blockers like amlodipine, felodipine, isradipine, intravenous nicardipine and nitrendipine have been studied in children. They are well tolerated, effective and safe. Enalapril, an angiotensin converting enzyme inhibitor is a commonly used pediatric antihypertensive agent. The maximum serum concentration occurs approximately 1 hour after administration, and that of the metabolite, enalaprilat peaks between 4 and 6 hours after the first dose, and 3 and 4 hours after multiple doses. Intravenous Enalaprilat is available for management of hypertensive crisis but only limited data are available in children. Captopril has shorter duration of action and can be given sublingually for faster action. Limited data are available on the efficacy and safety of Angiotensin Receptor Blockers like Losartan.


Conclusions: 

Most children who present with hypertensive crisis have secondary hypertension. Renal parenchymal disease is the commonest underlying etiological factor .With the increase in the prevalence of obesity in children, the incidence of hypertension among children is also on rise. Hypertensive encephalopathy and acute left ventricular failure and are frequent modes of presentation. Intracranial hemorrhage and renal failure are less frequent and often overlooked modes of clinical presentation. Hypertensive emergencies in symptomatic children should be treated without delay to avoid further damage to vital organs. BP should be brought down by no more than 25% within the first 8 hours. Asymptomatic children with hypertensive urgency require less aggressive approach and blood pressure can be brought down more gradually. Once the acute phase has been tackled, extensive work up is required to identify the underlying etiological factor. One should not forget that many cases of secondary hypertension are eminently curable.

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