Blood Pressure

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Secondary Hypertension

 

In 5% of cases the cause of hypertension is known (secondary hypertension). An important cause is hypertension related to pregnancy, which includes gestational hypertension, pre-eclampsia and eclampsia. Gestational hypertension is a blood pressure of 140/90 mmHg or greater after the 20th week of pregnancy. Pre-eclampsia, often seen in primagravidas, consists of hypertension, proteinuria and sometimes edema (eclampsia is pre-eclampsia with seizures, which may occur if pre-eclampsia is untreated). Headache and visual disturbances are common.
Treatment for pre-eclampsia is hospitalization, fetal monitoring, and intravenous magnesium sulfate for seizure control.
For a diastolic pressure of 110 mmHg or greater, hydralazine (Apresoline) 5 mg IV may be given. After the 36th week, induction of labor is the preferred treatment.

Renovascular hypertension is a common cause of secondary hypertension.
Treatment: in renal failure, nitroprusside is begun at 0.5 µg/kg/ min IV with the goal of maintaining the diastolic pressure at about 100 mmHg. Dialysis may be required.

Other causes of secondary hypertension are hypersecretion of steroid hormones from the adrenal cortex in Cushing’s disease and Conn’s syndrome (primary aldosteronism), and pheochromocytoma, which is an adrenaline-secreting tumor of the adrenal medulla causing episodic spells of headache, sweating and heart palpitations from surges of epinephrine and norepinephrine.
Treatment: if the cause of Cushing’s disease, Conn’s syndrome or pheochromocytoma is a tumor, removal is the therapy.

A rare cause of episodic hypertension in a young person is coarctation of the aorta, a congenital narrowing of the thoracic aorta near the left subclavian artery causing high pressures in the upper body and low in the lower. Blood pressure must be determined in the arms and legs to detect the condition.
Treatment: aortic resection or balloon angioplasty.

Drugs or drug withdrawal may cause a hypertensive crisis. Cocaine and amphetamines stimulate the adrenergic nervous system.
Treatment: most of the time the cocaine abuser with hypertension responds to diazepam (Valium) 5 mg IV or lorazepam (Ativan) 2 mg IV. In severe cases nitroprusside is added.

Occasionally a person taking one of the monoamine oxidase inhibitor antidepressants indulges in Chianti wine, beer, cheese, or pickled herring containing the amino acid tyramine. Tyramine releases norepinephrine from sympathetic nerve endings normally inactivated by monoamine oxidase. Suppression of the mechanism causes excessive norepinephrine release and a hypertensive crisis.
Treatment: nitroprusside 0.5 µg/kg/min.

Withdrawal from alcohol, opiates, or noncompliance with antihypertensive drugs such as clonidine (Catapres), may also cause a hypertensive event.
Treatment: the hypertension of alcohol withdrawal usually responds to diazepam (Valium) 5-10 mg IV or lorazepam (Ativan) 2 to 4 mg IV followed by diazepam 10 mg or chlordiazepoxide (Librium) 50 mg PO every 6 hours. The abrupt cessation of antihypertensive drugs such as clonidine may cause rebound hypertension. Treatment consists of reinstitution of the drug and tapering.