Introduction:
Hypertensive encephalopathy is a type of hypertensive emergency characterized by changes in mental status, increased blood pressure, seizures, headache, nausea, vomiting, and visual disturbances. The term was first coined in the year 1928. It is a life-threatening condition where damage to the target organ occurs due to severely increased blood pressure. It is usually diagnosed after the symptoms resolve by lowering the blood pressure. This is one of the manifestations of a hypertensive emergency that requires immediate treatment. Hypertensive encephalopathy is also one of the causes of posterior reversible encephalopathy syndrome (PRES). Detecting the syndrome in the earlier stages is necessary, thus allowing prompt treatment. The pathophysiology leading to PRES is not clearly understood. Most people recover completely after the treatment.
What Causes Hypertensive Encephalopathy?
Hypertensive encephalopathy is caused by:
- Improperly controlled blood pressure.
- Cerebral edema (swelling of the brain).
- Hypertensive brainstem encephalopathy (brain disease).
- Eclampsia (seizure in a pregnant woman).
- Evaluation for acute or chronic kidney disease.
- Medications such as Amphetamines and Cocaine.
- Drug side-effects such as immunosuppressive agents.
- Preeclampsia (high blood pressure during pregnancy).
What Is the Pathophysiology of Hypertensive Encephalopathy?
Most of the time, the brain functions well with normal blood perfusion range without getting affected by the changes in systemic blood pressure. The normal cerebral perfusion pressure (CPP) ranges from 50 to 150 mm Hg or mean arterial pressure (MAP) from 60 to 160 mm Hg. With an increase in MAP, the blood vessels in the brain contract, and with a crease in MAP, the brain blood vessels dilate to keep the CPP constant. This process keeps cerebral blood pressure constant despite fluctuations in systemic blood pressure.
Severe, abrupt fluctuations in blood pressure can exceed this regulatory mechanism as the blood vessels can constrict only to a limited extent. As a result, the elevated blood pressure in the brain causes a disruption in the blood-brain barrier, and blood diffuses into the brain. This leads to the development of cerebral edema, raised intracranial pressure, altered mental status, changes in vision, and seizures.
In people with chronic high blood pressure, the brain's blood vessels undergo certain changes to allow a higher range of regulation. Hence, reducing teh blood pressure quickly in them can lead to a reduced blood supply to the brain (ischemia) at an increased MAP.
What Are Hypertensive Emergencies?
Hypertensive emergencies are emergency situations in which elevated blood pressure is associated with acute life-threatening organ damage involving either or any two of the following organs: brain, arteries, retina, kidneys, and/or heart (BARKH). In hypertensive emergencies, systolic blood pressure is higher than 180 mm Hg or diastolic blood pressure is higher than 120 mm Hg, along with acute organ damage. Hypertensive encephalopathy is one such hypertensive emergency. Such people need affection and fast-acting medications intravenously to securely reduce elevated blood pressure, protect the target organ's function, improve the symptoms, decrease the complications, and improve the clinical results.
How To Manage Hypertensive Encephalopathy in Emergency?
The foremost goal in treating any hypertensive emergency is to decrease blood pressure as quickly as possible with intravenous blood pressure medications to prevent further damage to the organs. Hypertensive encephalopathy is initially treated in the emergency department, and the definitive treatment for the condition is carried out in an intensive care unit (ICU).
The first line of treatment for hypertensive encephalopathy is the administration of antihypertensive drug therapy to reduce the MAP by 10 % to 15 % during the first hour. The MAP should not be reduced by greater than 25 % of the original MAP on the first day of treatment. This careful blood pressure reduction decreases the risk of ischemia, thus allowing the healing of the brain blood vessels. If the MAP falls below the auto-regulatory range in the brain, there is an increased risk of stroke and complications in other organs.
Initially, parenteral antihypertensive drugs are used. Oral administration of antihypertensive drugs should be avoided at this stage due to the slower onset of action. The parenteral drugs commonly used are Nicardipine, Labetalol, Fenoldopam, and Clevidipine. Fenoldopam is usually the drug of choice in people with kidney impairment as it has been found to have a protective effect on the kidneys. After the gradual diminishing of the initial intravenous therapy, oral antihypertensive drugs may be started and discontinued after a period of eight to 24 hours of reaching the normal blood pressure range.
In pregnant ladies with hypertension, antihypertensive therapies are chosen according to the health of the fetus and placenta.
Antiseizure medications can be continued until the symptoms improve. These medications can be gradually reduced after one or two weeks, as the recurrence of seizures after the resolution of encephalopathy is rarely reported.
Individuals with PRES who also have hypertension can also be treated with antihypertensive drugs. However, the dosage of the immunosuppressive drugs may be reduced or discontinued if the individual develops PRES.
If not adequately treated, hypertensive encephalopathy can progress to cerebral hemorrhage, coma, and death. However, an appropriate and prompt treatment can lead to complete recovery.
What Is the Prognosis?
In several cases, hypertensive encephalopathy can be reversed with an immediate but careful blood pressure reduction. The prognosis can vary depending on the presence or absence of other comorbidities. After discharge, careful monitoring, as well as management of the blood pressure, is necessary. Such people are at risk of developing other types of hypertensive crises if they do not take the medications regularly as prescribed. Once discharged, a follow-up with the physician is essential to encourage continuous blood pressure monitoring and mangement of hypertension. Specific lifestyle changes such as exercise, quitting smoking, and healthy eating habits should be incorporated.
Conclusion:
Hypertensive encephalopathy is one of the rare types of hypertensive crisis that requires immediate treatment. Failure or late treatment of the condition can lead to kidney failure, retinopathy, heart failure, and stroke. Without immediate treatment of excessively high blood pressure, brain edema can progress to epilepsy, coma, or death. Aggressive management of hypertensive encephalopathy is not advised as it can lead to ischemic conditions in the brain leading to a reduced cerebral blood supply. Prompt and cautious treatment is the key to complete recovery.
