Hypertensive emergencies

Introduction
A hypertensive emergency is high blood pressure with acute impairment of one or more organ systems (especially the central nervous system, cardiovascular system and/or the renal system) that can result in irreversible organ damage. In a hypertensive emergency, the blood pressure should be slowly lowered over a period of minutes to hours with an anti hypertensive agent.

Hypertensive emergency pathophysiology includes:

·         Abrupt increase in systemic vascular resistance, likely related to humoral vasoconstrictors 

·         Endothelial injury

·         Fibrinoid necrosis of the arterioles 

·         Deposition of platelets & fibrin

·         Breakdown of normal autoregulatory function  (Heartorg, 2015)

Terminology	Systolic Pressure (mm Hg)	Diastolic Pressure (mm Hg)
Normal	< 120	< 80
Hypertensive crisis - emergency	≥ 180	≥ 120

Uncontrolled high blood pressure can lead to:

• Loss of consciousness
• Memory loss
• Loss of kidney function
• Aortic dissection
• Angina (unstable chest pain)
• Pulmonary edema (fluid backup in the lungs)
• Eclampsia

·        Heart attack or stroke. 

·        Aneurysm. 

·        Heart failure. 

·        Weakened and narrowed blood vessels in your kidneys.

·        Thickened, narrowed or torn blood vessels in the eyes.This can result in vision loss.

·        Metabolic syndrome. 

Signs & symptoms

·         Headache.

·         Fits.

·         Nausea and vomiting.

·         Visual disturbance.

·         Chest pain.

·         Neurological deficit, eg CVE.

·         Bleeding due to disseminated intravascular coagulopathy (DIC).
(Mayoclinicorg, 2015)

Causes

·         Unilateral renovascular hypertension, e.g renal artery stenosis

·         Renin-secreting neoplasms.

·         Trauma to the kidneys.

·         Renal vasculitis, eg scleroderma, polyarteritis & systemic lupus erythematosus. 

·         Phaeochromocytoma.

·        Cocaine abuse

·         Drugs such as monoamine-oxidase inhibitors, combind oral contraceptives or the withdrawal of alcohol, alpha stimulants such as clonidine, or beta-blockers.

·         Sodium-volume overload and low renin levels, eg acute glomerulonephritis, primary aldosteronism. 

·         Eclampsia.

·        Hyperthyroidism or hypothyroidism

Investigations

·         Full history - including:

·         Past medical history.

·         Full systems review.

·         Drug history including over-the-counter, herbal remedies and recreational drugs.

·         Full examination - including:

·         Blood pressure measurements - lying, standing and in both arms (looking for coarctation or aortic dissection).

·         Fundoscopy - retinopathy, eg grade III (flame haemorrhages, dot and blot haemorrhages, hard and soft exudates) to grade IV (papilloedema).

·         Cardiovascular examination - lying and standing blood pressure; look for signs of cardiac failure or pulmonary oedema, carotid or renal bruits, left ventricular heave, cardiac murmurs, third or fourth heart sounds.

·         Neurological examination.

·         Blood tests:

·         FBC ± clotting screen.

·         U&Es, creatinine.

·         Liver and TFTs.

·         Blood sugar measurement.

·         ± Cardiac enzymes and fasting blood lipids.

·         Urine dip testing for protein and blood.

·         CXR - cardiac size, cardiac failure, etc.

·         ECG - left ventricular hypertrophy or left atrial enlargement.

Subsequent investigations may include:

·         CT/MRI scan of the head or kidneys.

·         Plasma renin activity.

·         Plasma aldosterone level.

·         24-hour urine for vanillylmandelic acid (VMA) and catecholamine levels.

·         Auto-antibody levels, eg antinuclear factor.

Management

·         IV Nitroprusside is the drug that most often use for hypertensive emergencies. Phentolamine is the drug of choice for a Pheochromocytoma crisis. Also available parenterally are diltiazem, verapamil and Enalapril. Hydralazine is reserved for use in pregnant patient 

Also using,

·         Thiazide diuretics. Diuretics are medications that act on kidneys to help the body to eliminate sodium and water, reducing blood volume.

·         Beta blockers. 

·         Angiotensin-converting enzyme (ACE) inhibitors. 

·         Angiotensin II receptor blockers (ARBs). 

·         Calcium channel blockers. 

·         Renin inhibitors. 

 Additional medications to treat high blood pressure

·         Alpha-beta blockers. In addition to reducing nerve impulses to blood vessels, alpha-beta blockers slow the heartbeat to reduce the amount of blood that must be pumped through the vessels.

·         Vasodilators. 

·          Aldosterone antagonists. Examples are spironolactone (Aldactone) and eplerenone (Inspra). These drugs block the effect of a natural chemical that can lead to salt and fluid retention, which can contribute to high blood pressure. (Uptodatecom, 2015)

References

Uptodatecom. 2015. Uptodatecom. [Online]. [8 May 2015]. Available from: http://www.uptodate.com/contents/drugs-used-for-the-treatment-of-hypertensive-emergencies

Mayoclinicorg. 2015. Mayoclinicorg. [Online]. [9 May 2015]. Available from: http://www.mayoclinic.org/diseases-conditions/high-blood-pressure/basics/causes/con-20019580

Heartorg. 2015. Heartorg. [Online]. [8 May 2015]. Available from: http://www.heart.org/HEARTORG/Conditions/HighBloodPressure/AboutHighBloodPressure/Hypertensive-Crisis_UCM_301782_Article.jsp