Malignant hypertension is characterised by highly elevated blood pressure with papilledema, extravasation and retinal exudates and by hypertensive encephalopathy sings: severe headache, vomiting, vision disorders, paresis, epileptic seizures, in extreme cases – semicoma and coma. Those symptoms are caused by spasm in the cerebral arteries and brain edema. Sometimes autopsy performs plural little thrombi in cerebral arteries. Gallop cardiac and renal insufficiency are also possible to occur. Oligohydruria can be found by the time of diagnostics. Fibroid necrosis of arterial and arteriolar walls is typical, but those changes are reversible depending on treatment. Pathogenesis of malignant hypertension is unknown. Clinical image is determined by two independent processes: cerebral artery dilatation and general fibrinoid degeneration of arteriole walls. Cerebral artery dilatation is caused by loss of self-regulation arterial tone capacity in elevated blood pressure. Excessive cerebral blood flow leads to hypertensive encephalopathy. Generally, excess in renin plasma activity and aldosterone excretion can play a big role in vessels injury.
Malignant hypertension is developed in 1% of patients subjected to arterial hypertension. It is also possible in cases of high blood pressure and symptomatic hypertension. There are known cases of malignant hypertension when symptomatic hypertension was the first symptom. If patient receives treatment, then malignant hypertension has no chances to develop. Average age of these patients – 40 years and mostly it is diagnosed in men. Before the hypotensive treatment discovering, patients with malignant hypertension died within 2 years from renal insufficiency, hemorrhagic stroke or cardiac failure. In the modern conditions five-year survival rate exceeds 50%.
Malignant hypertension and hypertonic crisis treatment
Hypertonic crisis and malignant hypertension are exigent conditions demanding for immediate medical intervention. Those should be distinguished from severe arterial hypertension. Sharp decrease in pressure can lead to myocardial ischemia and cerebral ischemia. Urgent measures:
- 1. Complications control
- 2. 30% drop in diastolic pressure (not less than 95 mmHg)
Drugs that are used for malignant hypertension and crisis treatment are divided in two groups by their rate of action.
1. Drugs that serve to immediate pressure drop, for instance, in cases of epileptic seizures, can not be used as long-term treatment options. Intravenous fluid therapy is done with sodium nitroprussid, trimetafan camsilate and nitroglycerine (keeping an eye on pressure). The best medicine in case of emergency is “Sodium nitroprussid” that acts upon arterial and venous beds. It is infused at speeds of 0,25-8 ppb/min. Alternatively to ganglioblockers it does not have addicting property and it can be injected within several days at minimum risk of getting any of side effects. “Nitroglycerine” is infused at the rate of 5-100 mcg/min. It acts more effectively in patients who have undergone bypass surgery or were subjected to myocardial ischemia, left heart failure or instable angina. Mainly diazoxide acts on arterioles being infused at doses of 50-150 mg and it also helps to drop pressure within 1-5 minutes. The same dosage can be infused repeatedly within 5-10 minutes or several hours, when pressure rises. Total dose can not exceed the amount of 600 mg/day. Sometimes pressure drops too low and the drug is counter-indicative at suspicion on thoracic aortic aneurysm and cardiac infarction.
As far as diazoxide can increase myocardial contractility, it is recommended to administer beta-adrenoblockers along with it. “Enalaprilat” (enalapril mode for intravenous use) is especially recommended in cases of left heart failure and labetalol – intravenously in myocardial infarction and angina (as far as it prevents from heart rate acceleration). “Labetalol” can be ineffective if the patient has administered beta-adrenoblockers previously and it is counter-indicative at cardiac insufficiency, asthma, bradycardia and AV-blockade. It can be used in cases of eclampsia, if hydralazine is ineffective. Trimetafan camsilate (intravenously 0,5-5 mcg/min) is rarely prescribed. It acts on arterial and venous beds. In the process of infusion patient should be in a sitting posture and his pressure should be kept under a regular control at the hands of medical staff. The accurate dosage of trimetafan camsilate is harder to define than sodium nitropussid’s, but camsilate works better on thoracic aortic aneurysm.
2. Long-term drugs decrease pressure not that fast (action spike is reached after 30 minutes) but the administration method can be changed to ingestion. If that kind of delay is admissible, then Hydralazine is used intravenously. It usually acts within 10 minutes; every 10-15 minutes 10 mg of hydralazine are injected up to achievement of needed pressure level or before the exceedance of dosage at 50 mg. Whole hydralazine dose that was needed for primary pressure decrease can be injected repeatedly i.m. or i.v. every 6 hours. In severe CAD “Hydralazine” should be used carefully as it is counter-indicative at angina attack and thoracic aortic aneurysm. In contrast, it is prescribed in preeclampsia. Moreover, to get a quick drop in pressure level “Procardia” can be used sublingually but it causes tachycardia. “Furosemide” (per os or i.v.) – is a major treatment component. It promotes natriuresis, helps to overcome hypertensive encephalopathy and cardiac insufficiency, encourages sensibility to the main hypotensive drug. Cardiac glycoside is essential in the events of cardiac failure. Drugs activating catecholamine (methyldopa, reserpine, guanetidine) expulsion are counter-indicative even at suspicion on pheochromocitoma. The right option is “Phentolamine” i.v. that has a trade name of “Regitin”, but it also should be injected carefully to avoid a sharp drop in pressure.
If in presence of malignant hypertension, the treatment is ineffective and renal insufficiency is progressive, it is recommended to undertake peritoneal dialysis and hemodialysis: hypovolemia sometimes decreases pressure level and improves renal function. If that does not help and there is no response to hypotensive therapy (including minoxidil), arterial pressure decrease, especially in renin plasma high activity level, can cause bilateral nephrectomy, then permanent hemodialysis or renal transplantation can be placed on. Bilateral nephrectomy is used as a last resort for patient’s survival, when all the others options have been already used.