Hypotension (Low Blood Pressure)

Hypotension (Low Blood Pressure):-

·         Low blood pressure; the force of blood pushing by the heart against the walls of the arteries lower than normal.

·         Hypotension is generally considered as systolic blood pressure less than 90 mm Hg or diastolic less than 60 mm Hg.

·         Severely hypotension can deprive the brain and other vital organs of oxygen and nutrients, leading to a life-threatening condition called shock.

·         Causes of hypotension can ranged from dehydration to serious medical or surgical disorders

 

Ø  Symptoms:-

·         Dizziness or lightheadedness.

·         Fainting (syncope).

·         Lack of concentration.

·         Blurred vision.

·         Nausea.

·         Cold, clammy, pale skin.

·         Rapid, shallow breathing.

·         Fatigue.

·         Depression.

·         Thirst.

Ø  Causes:-

·         Conditions that can cause low blood pressure:

- Decrease blood volume (Hypovolemia or Dehydration);

o   Hemorrhage (blood loss).

o   Insufficient fluid intake (starvation).

o   Excessive fluid losses (diarrhea or vomiting).

- N.B; hypovolemic shock; is a life-threatening complication of dehydration.

                             - Decrease cardiac output;

o   Extremely low heart rate, heart failure or heart valve problems.

                             - Excessive vasodilation;

o   Severe infection (septicemia); can lead to a life-threatening drop in blood pressure called septic shock.

o   Severe allergic reaction (anaphylaxis); is a severe and potentially life- threatening allergic reaction.

                             - Endocrine problems;

o   Adrenal insufficiency (Addison's disease; hyposecretion secretion of adrenocortical hormones)

o   Hypothyroidism and parathyroid disease.

o   Low blood sugar (hypoglycemia).

                            - Pregnancy;

o   Hypotension during pregnancy may occurs because the circulation expands during pregnancy and hormonal changes cause the blood vessels to dilate, leading to a lowering of blood pressure.

                            - Lack of nutrients in diet;

o   Lack of the essential vitamins B12 and folic acid can cause anemia.

                            - Prolonged bed rest.

·         Medications that can cause low blood pressure:

ü  Diuretics and other antihypertensive drugs, tricyclic antidepressants, erectile dysfunction drugs (such as sildenafil) particularly in combination with nitroglycerin.

 

 

Ø  Types of hypotension:-

·         Most common types of hypotension depending on the causes and other factors;

Orthostatic (Postural) Hypotension (Low blood pressure on standing up)

§  Sudden drop in blood pressure when stand up from a sitting position or after lying down à the gravity cause blood to pool in the legs à the body compensates this by reflex tachycardia and vasoconstriction, but in people with orthostatic hypotension this compensating mechanism fails and blood pressure falls leading to dizziness, lightheadedness, blurred vision and even fainting. Orthostatic hypotension is especially common in older adults, with as many as 20% of those older than age 65, but orthostatic hypotension can also affect young.

Postprandial Hypotension (Low blood pressure after eating)

§  Sudden drop in blood pressure after eating à due to large amount of blood flows to the digestive tract after eating à the body compensates this by reflex tachycardia and vasoconstriction, but in people with postprandial hypotension the autonomic nervous system not compensating appropriately, because of aging or a specific disorder such as Parkinson's disease. Postprandial hypotension is especially common in older adults.

Neurally Mediated Hypotension (Low blood pressure from faulty brain signals)

§  Blood pressure drop after standing for long periods, leading to signs and symptoms such as dizziness nausea and fainting. §  It occurs because of a miscommunication between heart and brain. §  Mostly affects young people. §  Stand for extended periods à blood pools in legs à nerves in the heart send faulty signals to the brain (that blood pressure is too high) àAs a result, the brain decrease the heart rate à decreasing blood pressure. This causes more blood to pool in the legs and less blood to reach the brain, leading to lightheadedness and fainting (Neurocardiogenic syncope). §  Dysautonomia; is an autonomic nervous system (ANS) malfunctions, is a type of neuropathy affecting the nerves that carry information from the brain and spinal cord to the heart, bladder, intestines, sweat glands, pupils, and blood vessels.

Multiple System Atrophy (MSA) with Orthostatic Hypotension (Low blood pressure due to nervous system damage)

§  Multiple System Atrophy (MSA), also called Shy-Drager syndrome. §  This rare disorder causes progressive autonomic nervous system. §  ANS controls involuntary functions such as blood pressure, heart rate, breathing and digestion. §  This condition can be associated with muscle tremors, slowed movement, problems with coordination and speech, and incontinence, its main characteristic is severe orthostatic hypotension combination with very high blood pressure when lying down.

 

 

 

Ø  Complications:-

·         Moderate forms of low blood pressure can cause not only dizziness and weakness but also fainting and a risk of injury from falls.

·         Severely low blood pressure from any cause can deprive the body of enough oxygen to carry out its normal functions, leading to damage of heart and brain.

·         Shock and death are the end result of prolonged low blood pressure.

Ø  N.B:-

·         Acute hypotension; often associated with the different forms of shock including: septic (septicaemia), cardiogenic (MI), hypovolaemia (haemorrhage, burns and dehydration), anaphylactic (hypersensitivity reaction), neurogenic (trauma to the spine).

·         Chronic hypotension; often associated with disease of the adrenals (Addison's disease).

 

 

Ø  Diagnosis:-

·         Blood pressure test.

·         Blood tests; shows blood sugar level and anemia.

·         Electrocardiogram (ECG), shows irregularities in heart rhythm.

·         Echocardiogram; ultrasound of chest, shows detailed images of for heart structure and function.

·         Tilt table test for orthostatic hypotension; which evaluates body reacts to changes in position

 

 

Ø  Treatments:-

Lifestyle Modification

§  Drink enough amount of water; to increase blood volume.

§  Add more salt in diet: to increase blood volume.

§  Eat healthy diet; contains all nutrients for good health by focusing on a variety of foods, including whole grains, fruits, vegetables, and lean chicken and fish.

§  Eat small, low-carbohydrate meals; to help prevent blood pressure from dropping sharply after meals.

§  A morning dose of caffeine; as coffee or tablet form can be effective.

§  Stand up gradually; to reduce the dizziness and lightheadedness.

§  Avoid standing for long periods of time; to prevent neurally mediated hypotension.

§  Wear compression stockings: to reduce the pooling of blood in the legs.

Antihypotensive Drugs

Ø  Antihypotensive Agents:-

·         Also known as a vasopressor agents.

·         Classes,

o    Sympathomimetic Agents; vasoconstrictors or cardiac stimulants.

o    Synthetic Mineralocorticoids: increase sodium and water retention.

Sympathomimetic Agents

Etilefrine (Effortil®)

- Etilefrine is a cardiac stimulant used as an antihypotensive, suggesting to stimulation of both α and β   adrenergic receptors. - Used for symptomatic treatment of orthostatic hypotension (OH). - Dosage forms, oral solution (drops), tablets and injection. - Oral solution (10 drops = about 5 mg) should be taken with liquid before meals: ·         Under 2 years: 2-5 drops three times a day. ·         2-6 years: 5-10 drops three times a day. ·         Over 6 years: 10-20 drops three times a day.

Midodrine (Gutron®)

- Midodrine is a prodrug that is hydrolysed to Desglymidodrine. - Desglymidodrine, is an α1-agonist, does not stimulate cardiac β-adrenergic receptors. - It is used orally for symptomatic treatment of orthostatic hypotension (OH). - Dose; adult, 10 mg orally three times a day. Do not give more frequently than every 3 hours, after   the evening meal, or less than 4 hours before bedtime. Because desglymidodrine is excreted renally,   dosing in patients with abnormal renal function should it is recommended that treatment of these   patients be initiated using 2.5-mg doses.

Heptaminol (Corasore®)

- Heptaminol is a cardiac stimulant drug, it have a positive inotropic action, with a slight peripheral   vasoconstrictor properties. - Uses; hypotension, fainting tendency and circulatory collapse. - Dose; o    Infants and children under 12 years: 4-16 drops (25-100 mg) depending on age, 2-4 times                                                                                daily, up to 6 times daily if necessary. o    Children over 12 years and adults: One tablet or 25 drops, (150 mg) 2-4 times daily, up to                                                                6 times daily if necessary.

Sympathomimetic agents used in hypotensive shock

- Epinephrine; used in anaphylactic shock. Norepinephrine , Dopamine and Dobutamine;   used in cardiogenic and septic shock.

 

Synthetic Mineralocorticoids

Fludrocortisone (Astonin-H®)

- Fludrocortisone (also called  9α-fluorocortisol or 9α-fluorohydrocortisone) is a synthetic    corticosteroid with moderate glucocorticoid potency and much greater mineralocorticoid potency. - It is used primarily to replace the missing aldosterone hormone in adrenal insufficiency (Addison's   disease), it cause ↑ salt and water retention à ↑ blood volume à↑ CO à↑ BP. - Used with caution in diabetes mellitus, CHF, glaucoma, children and pregnancy. - Most common side effects; ankle edema, hypokalemia, headache and rarely congestive heart   failure. - Dose; 0.05 to 0.1 mg orally/24 hours.

Ø  N.B:-

·         Administration of fluid and sodium chloride to supplement volume expansion.

·         Anemia, infections or dehydration must be treated firstly.

·          Vasopressin analogues (Desmopressin; see endocrine chapter) may be used to supplement volume expansion.

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