Hypertensive Encephalopathy: Definition, Symptoms, Causes, Diagnosis, Treatment, Consequences and Prevention

In pediatric patients, hypertension is defined as a persistent elevation of systolic or diastolic blood pressure.

Stage 1 hypertension exists if blood pressure (BP) is between the 95th percentile and 5 mm Hg greater than the 99th percentile.

Stage 2 (or severe) hypertension, which warrants immediate evaluation and treatment, is defined by a BP greater than 5 mm Hg greater than the 99th percentile.

In patients with severe hypertension or stage 2, presentation varies between an urgent medical condition and a life-threatening emergency.

There is a spectrum among these categories, but it is generally considered that patients who present severe elevation of the BP accompanied by signs of acute damage in the terminal organs have a hypertensive emergency.

The affected organs can include kidney, heart, eyes and brain; The most commonly affected organ is the brain, which produces a phenomenon known as hypertensive encephalopathy (HE).

In the setting where MRI is available, the often reversible changes in white matter found in the setting of HD are called reversible posterior encephalopathy syndrome (PES).

What is hypertensive encephalopathy?

Hypertensive encephalopathy is characterized by alterations in mental status, visual changes or seizures associated with severe hypertension. If this medical emergency is not treated, coma, status epilepticus and death can develop rapidly.

As with any hypertensive emergency, immediate confirmation of the diagnosis of HD, the evaluation of antihypertensive contraindications and the initiation of intravenous drug treatment are essential.

Current guidelines based on expert opinion recommend close monitoring of BP, the use of intravenous infusions for the adjusted reduction of BP and the transfer to a critical care setting for these patients.

The goal is an initial reduction of no more than 25% in 8 hours (10% in the first hour, then up to 15% more in the next 7 hours), followed by a more gradual decrease in blood pressure for days to weeks.

A more rapid initial decrease in BP may be associated with ischemic conditions, such as stroke, as a result of altered self-regulatory mechanisms.

What are the symptoms of hypertensive encephalopathy?

The symptoms of hypertensive encephalopathy include severe hypertension and neurological changes caused by cerebral edema.

Early symptoms, such as headache and nausea, will cause confusion and / or irritability and, ultimately, coma and / or seizures if left untreated.

Although blood pressure will generally be classified as stage 2 hypertension, the rapid increase in BP can cause symptoms at a lower absolute pressure than would be expected with chronic high blood pressure; therefore, any patient with hypertension and altered mental status should be evaluated for possible HD.

Patients with HD may or may not have evidence of another final organ injury, such as kidney disease (hematuria and / or proteinuria, occasionally acute renal failure), ophthalmic disease (hemorrhage / retinal exudate and / or papilloedema) or heart disease (insufficiency cardiac).

Findings in any of these other organ systems would represent a hypertensive emergency even in the absence of neurological findings, and management should be equally aggressive for these conditions.

What other illness / condition does some of these symptoms share?

All patients with emergency or hypertensive emergency should be carefully evaluated to determine the extent of the disease, if appropriate.

Urgent hypertension should be treated promptly, but the need for critical care management or intravenous drug administration depends on local circumstances and resources.

Other conditions that must be ruled out include:

Massive intracranial lesions: these lesions, such as a tumor, stroke or occult trauma, can present with altered mental status and hypertension (in response to increased intracranial pressure).

The differentiation of this condition is essential because the pharmacological decrease in BP in this situation would compromise cerebral perfusion.

Ophthalmic hypertensive emergency : This can cause visual changes in the context of severe hypertension but without any intracerebral abnormality. The management of this condition is similar to that of EH.

Sympathetic stimulation : Such stimulation may be due to endogenous causes (eg, pain, fear / panic disorder) or exogenous agents (eg, ingestion of sympathomimetic agents), which may cause hypertension and mental state abnormalities.

Management should focus on the main problem in these circumstances, but often also includes control of BP.

What causes hypertensive encephalopathy and how common is it?

As discussed above, HD is caused by severe uncontrolled hypertension with overwhelmed brain self-regulating mechanisms.

Although hypertension and HD are more common in adults than in children, the risk of permanent neurological dysfunction due to uncontrolled HD or an excessively aggressive treatment of hypertension is similar in children and adults.

The predisposing factors for the development of HE include the same factors that cause hypertension.

Brain self-regulation allows constant blood flow to the brain. The upper and lower limits of self-regulation may change in disease states (such as chronic hypertension).

Additionally, there is likely to be considerable individual variation in these limits. However, for all patients, the risk of HD increases as the upper limit of self-regulation is exceeded.

Additional increases in BP are transmitted directly to the cerebral vasculature, resulting in endothelial dysfunction, capillary leak, cerebral edema, and subsequent neurological symptoms.

In adult patients, the most common cause of hypertensive emergencies is poorly controlled primary (essential) hypertension.

Although this diagnosis is increasing in frequency in children due to the current epidemic of pediatric obesity, hypertension in children is much more likely to be a secondary finding in another disease process.

EH can be caused by the following:

  • Chronic kidney disease or renovascular disease.
  • Acute kidney disease such as glomerulonephritis.
  • Toxidromes such as amphetamine poisoning or serotonin syndrome.
  • Excess levels of catecholamines as in pheochromocytoma, hyperthyroidism.
  • Pharmacological effects such as corticosteroids or immunosuppressants.

Cerebrovascular circulation is able to self-regulate, that is, to maintain a constant blood flow over a range of perfusion pressures by adjusting the diameters of the cerebral vessels as the pressure increases.

However, beyond a maximum constriction level of the vessels, the limit of self-regulation is reached, and additional pressure increases are transmitted directly to the cerebral vasculature.

This results in endothelial damage and cerebral edema, which causes the neurological findings. With a chronically elevated BP, this self-regulating mechanism is shifted in such a way that self-regulation is maintained.

The timing of the presentation may be the result of an acute onset of hypertension in a previously normotensive patient or the eventual failure of a displaced self-regulation mechanism in patients with long-standing hypertension.

In any case, the primary pathogenesis is that it has exceeded the cerebral self-regulating mechanisms.

What laboratory studies should be requested to help confirm the diagnosis?

No laboratory studies are necessary to make the diagnosis of HD, the diagnosis is based on vital signs (hypertension) and clinical / neurological examination.

However, patients with HD are at risk of further damage to the terminal organs, such as heart, kidney and eye.

Therefore, most experts recommend the evaluation of these conditions with appropriate tests. Additional tests are aimed at determining the cause of hypertension.

A full evaluation may include the following:

  • Urinalysis for evidence of renal dysfunction.
  • Pregnancy test / human chorionic gonadotropion in urine to rule out preeclampsia / eclampsia.
  • Toxicological screen of urine / serum for ingestion.
  • Measurement of catecholamine to evaluate pheochromocytoma.
  • Determination of glucose to evaluate diabetes.
  • Electrolytic panel and renal function test.

Would imaging studies be useful? If so, what?

Computed tomography (CT) is essential to exclude cerebrovascular accidents, tumors, intracerebral hemorrhage or trauma as alternative diagnoses. In the case of HD, CT may show cerebral edema or it may be normal.

Chest x-ray and electrocardiography should also be performed to evaluate left ventricular hypertrophy (evidence of long-standing hypertension) or congestive heart failure (acutely related to hypertensive emergency).

Renal ultrasound and echocardiography may also be useful as complementary tests to evaluate renal or cardiac pathologies.

Magnetic resonance imaging (MRI) may show parietooccipital leukoencephalopathy (PRES).

However, care must be taken to ensure that proper administration is never stopped pending the results of the MRI, since MRI tests can be very time-consuming and delays in therapy can be catastrophic.

In addition, magnetic resonance imaging in pediatric patients often requires sedation or anesthesia, and the risks of performing sedation in the patient with altered mental status and hemodynamic lability (as seen with HD) are significant.

What is the treatment of hypertensive encephalopathy?

Before the start of medical therapy, secondary causes of hypertension should be ruled out quickly as discussed above.

For example, the administration of analgesics for the patient with pain or a specific antidote for a patient who ingested a toxin can resolve the elevation of the BP without the need for an additional intervention.

Within 8 hours of diagnosis, the therapeutic goal is to reduce BP by 20% -25% maximum basal BP.

Most experts recommend a rapid reduction by 10% in the first hour, followed by a slower decrease of up to 15% more in the next 7 hours.

Due to the displacement of self-regulation curves, irreversible damage to the brain and another ischemic organ can occur at the end with an excessively rapid reduction in BP.

This objective will reduce the emerging risk of an ongoing lesion of terminal organ hypertension while preserving perfusion of the organ within the self-regulation zone.

In the following hours or days, the patient must be managed in a critical care environment by a multidisciplinary team composed of an intensivist and an expert in hypertension (usually a nephrologist or pediatric cardiologist, depending on the environment).

This management will consist of an expanded evaluation of the cause of hypertension, the evaluation of other secondary lesions in the organs, the gradual gradual reduction of BP to normal levels and the transition of antihypertensive agents to a stable enteral regimen for chronic treatment. .

What are the adverse effects associated with each treatment option?

The main adverse effect of concern for the professional is the risk of irreversible ischemic damage in the final organ as a result of an excessively aggressive BP reduction.

This is best avoided with the careful administration of a continuous infusion of medication as discussed above.

Specific adverse effects of medications:

Beta-blockers (including labetalol, esmolol, and others) can decrease cardiac output in children.

This is particularly true in young infants, in whom cardiac output depends on an adequate heart rate with a relatively fixed ventricular stroke volume.

Beta-blockers can also precipitate bronchospasm in at-risk (asthmatic) patients due to the direct pharmacological effects of beta-antagonism on bronchial smooth muscle.

Vasodilators (calcium channel blockers, hydralazine, nitroprusside ) generally cause reflex tachycardia in children with intact baroreceptor mechanisms.

Prolonged or high administration of nitroprusside may precipitate cyanide toxicity.

This has a limited clinical use of nitroprusside in some centers. However, nitroprusside remains a potent, fast-acting, readily available second-line agent for the treatment of patients with HD.

What are the possible consequences of hypertensive encephalopathy?

Patients with neurological dysfunction and hypertension generally belong to one of three categories.

The first group includes those patients with hypertension resulting from an underlying intracranial abnormality (eg, tumor, elevated intracranial pressure) for whom the prognosis depends on the prognosis of the underlying condition.

The second group includes those patients for whom an unrelated cause (eg, cocaine ingestion) has caused both hypertension and altered mental status.

The elimination or reversal of the underlying cause over time will allow a more accurate neurological evaluation of these patients.

The third group of patients, those with hypertensive encephalopathy, have an altered mental state directly caused by elevated BP.

In many cases, neurological dysfunction and MRI findings are often reversible with BP control, as indicated above, caution should be exercised to avoid rapid reduction of BP to reduce permanent neurological sequelae.

In general, the diagnosis of hypertension predicts greater morbidity and long-term mortality for patients. However, for any individual patient, the prognosis will depend on the treatment options and the prognosis of the underlying disease process.

This is particularly true in pediatric patients, for whom secondary hypertension is much more common than primary / essential hypertension.

Major complications include permanent neurological sequelae as a result of a rapid reduction in BP or the severity of hypertension. Secondary complications caused by the side effects of medications are discussed above.

Even in the absence of intracerebral hemorrhage, a known complication of severe hypertension, untreated HE can progress rapidly (in a matter of hours) to unconsciousness, status epilepticus, and death.

For this reason, HD should be treated as a true medical emergency, and proper consultation of specialists is essential.

Are there additional laboratory studies available?

All laboratory and radiological tests should be directed toward assessing the severity and cause of HD.

There are no confirmatory tests that are specific for HD, although findings in T2-weighted brain magnetic resonance of reversible parietooccipital leukoencephalopathy are common.

How can hypertensive encephalopathy be prevented?

In patients with known hypertension, it is better to avoid HD with adequate control of BP and, for those with secondary hypertension, treatment of the underlying disease process.

Many cases of HD concomitantly present a new diagnosis of severe hypertension in the environment of the emergency department.

For this population, the most effective prevention may be the maintenance of an appropriate population selection for hypertension.

Screening for hypertension in children at risk (for example, those with a history of umbilical artery catheterization) can also provide early detection and prevention of severe and uncontrolled hypertension.