Acute Hypertension n Emergencies

7/23/2019 Acute Hypertension n Emergencies

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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. Thespectrum of hypertension that presents to the Emergency Department rangesfrom mild and asymptomatic to a true hypertensive emergency.A definition of hypertension ideally is based on a threshold level of bloodpressure that divides those at risk for adverse outcomes from those who haveno increased risk. The important conclusions of the fourth report on thediagnosis, evaluation and treatment of high blood pressure in children andadolescents of The National High Blood Pressure Education Program WorkingGroup 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 between90- 95th percentile. These children should be observed carefully and evaluatedif risk factors like obesity are present; tracking data suggest that this subgroupis more likely to develop overt hypertension over time than normotensivechildren.• Adolescents with blood pressure levels more than 120/80 mm Hg should beconsidered pre hypertensive.• A patient with blood pressure levels >95th percentile in a physician’s officeor clinic, who is normotensive outside a clinical setting, has white-coathypertension. Ambulatory blood pressure monitoring is helpful forconfirmation.• If the blood pressure is >95th percentile, it should be staged. If stage 1 (95thpercentile to the 99th percentile plus 5 mm Hg), measurements should berepeated on 2 more occasions. If hypertension is confirmed, evaluation shouldproceed. If blood pressure is stage 2 (>99th percentile plus 5 mm Hg), promptreferral should be made for evaluation and therapy. If the patient issymptomatic, 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 haveurinary infections and renal scars.

Evaluation:

When confronted with newly diagnosed hypertension in the child, thephysician should consider three important issues: 1) Is the hypertensionprimary or secondary? 2) Is there evidence of target organ damage? and 3) Arethere associated risk factors that would worsen the prognosis if thehypertension were not treated immediately?.

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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, orumbilical 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 orhypertension.After several determinations of the blood pressure, a focused physicalexamination should be performed immediately. One should check for anyevidence of neurologic dysfunction and left ventricular dysfunction / cardiacfailure. Fundoscopy should be performed looking for hemorrhage, infarcts orpapilledema. The peripheral pulses should be palpated carefully. Weak anddelayed femorals suggest coarctation of aorta. Any discrepancy in the upperand lower extremity BP measurements should be noted. The presence of anabdominal bruit suggests renovascular hypertension.An improper cuff size can significantly record a wrong blood pressure. Byconvention, an appropriate cuff size is a cuff with an inflatable bladder widththat is at least 40% of the arm circumference at a point midway between theolecranon 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 acuff 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 adefinable cause. The secondary cause will be found more likely when thepatient is younger and hypertension is more severe. Most acute hypertensionin childhood is due to glomerulonephritis. Chronic hypertension is commonlyassociated with renal parenchymal disease and only a small proportion haverenovascular hypertension, pheochromocytoma or coarctation of the aorta .Late in the first decade and into the second decade of life, primaryhypertension begins to predominate. Coarctation of the aorta accounts for onethird cases of hypertension in neonatal period and infancy. Renovascularcauses 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 thepresence of acute end-organ dysfunction discovered in the history, physicalexamination or investigations, and not by the height of the BP.

Hypertensive Emergency

Hypertension associated with evidence of end-organ dysfunction constituteshypertensive emergency.Malignant hypertension is characterized by marked elevations in systolicand/or diastolic BP (e.g., 160 mm Hg or higher systolic/ 105 mm Hg or higherdiastolic for those less than 10 years of age; 170 mm Hg or higher systolic/ 110mm Hg or higher diastolic for those more than 10 years of age) and is oftenassociated with spasm and tortuosity of the retinal arteries, papilledema, andhemorrhages and exudates on fundoscopic examination.Hypertensive encephalopathy(an example of hypertensive emergency) is seen

often in malignant hypertension and consists of a combination of symptomsand 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 areadmitted to an intensive care unit for continuous cardiac monitoring andfrequent assessment of neurologic status and urine output. An IV line is startedfor fluids and medications. Patients typically have altered blood pressureautoregulation, and overzealous reduction of blood pressure to reference rangelevels may result in organ hypoperfusion. The initial goal of therapy is toreduce the mean arterial pressure by approximately 25% over the first 8 to 12hours. An intra- arterial line is helpful for continuous titration of bloodpressure. Sodium and volume depletion may be severe, and volume expansionwith isotonic sodium chloride must be considered. Urine output should be

monitored from the outset. Any serious complications must be recognized andmanaged along with the treatment for hypertension. Anti convulsants shouldbe administered to a child with seizure.






A number of medications are available for hypertensive emergencies. Thechoice of drugs depend on several factors such as the clinical condition of thepatient, the presumed cause, whether there is a change in cardiac output ortotal 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 tomonitor the blood pressure carefully as is being reduced. Because hypertensiveencephalopathy is a possible complication of hypertensive emergencies,antihypertensive agents with minimal CNS side effects should be chosen toavoid confusion between symptoms of disease and adverse effects of the drug.Centrally acting drugs like Alpha Methyl Dopa and Clonidine are usually notpreferred because of the CNS side effects. Intravenous administration isgenerally preferred in order to carefully titrate the fall in blood pressure. Toorapid reduction in blood pressure can interfere with adequate organ perfusionand hence a stepwise reduction should be planned. Hypertensive emergenciesshould be treated by an intravenous antihypertensive that can produce acontrolled reduction in the blood pressure, aiming to decrease the pressure by25% over the first 8 hours after presentation and then gradually normalizingthe BP over the next 48 hours. Each of the most commonly used medicationsoffers distinct advantages and disadvantages and each clinical situationrequires its own mode of management. However, some general guidelines areusually helpful.

Sodium nitroprusside is an arteriolar and venous vasodilator that is invariablyeffective. BP decreases with little change in cardiac output, and reflextachycardia is not usually an important problem. It is administered by constantinfusion. Its effect is immediate, and lasts only as long as the infusion iscontinued. Its use requires intensive observation and therefore may not beindicated in the ED. Other disadvantages are that the drug requires 10 minutesto prepare and is photosensitive, and there is a potential for cyanideaccumulation. The infusion bottle and tubing should be covered and protectedfrom light.

Diazoxide is an arteriolar vasodilator, has little effect on capacitance vesselsand has no direct cardiac effect. It is very potent with a rapid onset, and theeffect can be dramatic. It may provide a long duration of BP control (8 to 12hours). 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 andhyperglycemia.

Hydralazine is an arteriolar vasodilator that is not as potent as diazoxide ornitroprusside. 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 themanagement of severe hypertension that results from pheochromocytoma andcoarctation of the aorta and is a reasonable alternative in the treatmentof 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, butbiting the capsule and swallowing its contents achieves measurable bloodlevels more rapidly than the sublingual route. Its use depends on the patient’sstate of consciousness. It is contraindicated in the presence of intracerebralbleeding.

Nicardipine, another calcium channel blocker is an excellent drug for use inemergencies, since it can be administered as an infusion that can be easilyprepared and titrated.

Phentolamine is a pure -adrenergic blocker used almost exclusively for thetreatment of catecholamine crisis (as seen in patients with pheochromocytomaor ingestion of sympathomimetic agents such as cocaine). The effect isimmediate. There is a high risk of hypotension afterthe primary lesion (e.g. pheochromocytoma) is excised, and care should beexercised and the surgeons should be alerted to this possibility.Most children with hypertensive crisis have chronic or acute renal disease. Inthese patients, management of blood pressure also requires careful attention tofluid balance and diuresis. Intravenous Frusemide is usually effective eventhough 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 anurgent hypertensive crisis may not require hospitalization if the therapy in theemergency department is successful, and adequate follow-up can be ensured.Often, oral antihypertensive agents are sufficient, although there are occasionswhen parenteral therapy is indicated.

Other Drug Therapy:

Calcium channel blockers like amlodipine, felodipine, isradipine, intravenousnicardipine and nitrendipine have been studied in children. They are welltolerated, effective and safe. Enalapril, an angiotensin converting enzyme

inhibitor is a commonly used pediatric antihypertensive agent. The maximumserum concentration occurs approximately 1 hour after administration, andthat of the metabolite, enalaprilat peaks between 4 and 6 hours after the firstdose, and 3 and 4 hours after multiple doses. Intravenous Enalaprilat isavailable for management of hypertensive crisis but only limited data areavailable in children. Captopril has shorter duration of action and can be givensublingually for faster action. Limited data are available on the efficacy andsafety of Angiotensin Receptor Blockers like Losartan.

Conclusions:

Most children who present with hypertensive crisis have secondaryhypertension. 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. Hypertensiveencephalopathy and acute left ventricular failure and are frequent modes of presentation. Intracranial hemorrhage and renal failure are less frequent andoften overlooked modes of clinical presentation. Hypertensive emergencies insymptomatic children should be treated without delay to avoid further damage






to vital organs. BP should be brought down by no more than 25% within thefirst 8 hours. Asymptomatic children with hypertensive urgency require lessaggressive approach and blood pressure can be brought down more gradually.Once the acute phase has been tackled, extensive work up is required toidentify the underlying etiological factor. One should not forget that manycases of secondary hypertension are eminently curable.

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Acute Hypertension n Emergencies