Orthostatic hypotension definition
Orthostatic hypotension is also known as postural hypotension. It is characterized by a drop in the patient’s blood pressure by15 to 20 mmHg with heart rates of at least 20 beats per minutes. Orthostatic hypotension may occur with or without an increase in the heart rates. The drop in the blood pressure occurs when the patient rises from supine position into a standing or sitting position. This can be detected by measuring the blood pressure of the patient every 5 minutes when he or she changes the position. Orthostatic hypotension indicates the failure of the vasomotor compensatory mechanism /response alteration in the position of the patient. Orthostatic hypotension typically present with blurred vision, syncope and light headedness. Orthostatic hypotension pathologically may occur because of side effects of the drugs, systemic disorders, endocrine disorders, electrolytes and fluid imbalance as well as prolonged bed rest.
Orthostatic hypotension is detected by measuring the blood pressure of the patient in standing, siting and supine position. If orthostatic hypotension is detected considered checking the patient for alteration of the patient level of consciousness, tachycardia, clammy and pale skin. The present of all these signs indicates the present of hypovolemic shock. Blood and fluid replacement via the large bore IV line are required. Every 15 minutes, the patient’s vital signs are taken. Encourage bed rest and monitor the fluid intake and urine output.
History is taken if the patient is not in a dangerous situation. The patient is asked if he often suffers from fainting, weakness or dizziness while standing. The present of any associated symptoms such as chest / abdominal discomfort, headache, nausea, impotence, orthopnea, fatigue or gastrointestinal bleeding should be asked. Focus on history on drugs intake.
The physical examination is performed by palpating the peripheral pulses and auscultate the lung/chest. Observe the gait and the strength of the patient and always check the skin turgors of the patient.
The differential diagnoses of orthostatic hypotension are hypovolemia, hyponatremia, hyperaldosteronism, alcoholism, adrenal insufficiency and amyloidosis.
Hypovolemia is also known as dehydration. Besides orthostatic hypotension, dehydrate patient may present with dry mucous membrane, poor skin turgors, sunken eyeballs, oliguria, dizziness, profound thirst, nausea, anorexia, muscle weakness, fatigue and apathy.
Hyponatremia is caused by syndrome of inappropriate antidiuretic hormone secretion, hypothyroidism, adrenal insufficiency and the use of thiazide diuretics. Orthostatic hypotension is accompanied by decrease level of consciousness , seizures, irritability, poor skin turgor, cold clammy skin, anuria, oliguria, fatigue, muscle weakness, twitching, abdominal cramps, vomiting, nausea, tachycardia, profound thirst.
Hyperaldosteronism may cause diabetes mellitus, orthostatic hypotension and hypokalemia. Hypokalemia present with muscle weakness, neuromuscular irritability, fatigue, intermittent flaccid paralysis, paraesthesia, headache, tetany, positive Chvostek’s sign and Trousseau’s sign. Other findings are personality changes, polydipsia, polyuria and visual disturbance.
Orthostatic hypotension is also associated with amyloidosis. Amyloidosis is an infiltration of the amyloid into the autonomic nerve. Other symptoms and signs vary and include cough, fatigue, orthopnea, dyspnea, tachycardia and angina.
Alcoholism may cause peripheral neuropathy. Peripheral neuropathy is associated with orthostatic hypotension. Other symptoms and signs of alcoholism are nausea, tingling, vomiting, numbness, bizarre behavior, changes in bowel habit and impotence.
Adrenal insufficiency is associated with progressive symptoms and signs. Adrenal insufficiency is presented with orthostatic hypotension, weight loss, weak , irregular pulse, irritability, abdominal pain, fasting hypoglycemia, nausea and vomiting, anorexia, poor co - ordination, bronze coloration of the skin ( hyper pigmentation) on the knee, waist, knuckle, palms, elbow, buccal mucosa, tongue, gum, lips, constipation, diarrhea, craving for salty food and enhanced hearing, smell and taste along with syncope, amenorrhea and decrease in libido.
Orthostatic hypotension is also present because of sympathectomy that effects the mechanism of vasoconstrictive as well as prolonged bed rest.
Orthostatic hypotension may also cause by intake of specific drugs. These drugs will reduce the circulating blood volume, causing depression of the sympathetic nervous system and dilation of the blood vessel. These drugs are morphine, spinal anesthesia, bretylium tosylate, monoamine oxidase inhibitors, nitrate, levodopa, phenothiazines, tricyclic antidepressant and the initial dosage of prazosin hydrochloride or guanethidine monosulfate.
The patient’s fluid balance is inspected by weighing him daily and monitor his fluid intake and urine output. The patient is advised to change his position gradually to minimize orthostatic hypotension. The head of the bed is elevated. The patient should be in a sitting position with the feet dangling over the sides of the bed. The patient may sit in a chair for a brief period of time. Then return him to the bed, if he is pale or felt dizzy and display other signs of hypotension.
The safety of the patient is the main priorities. The patient need for assistive device such as walker or cane should be assessed. Never leave the patient alone.
The diagnostic test required are drugs level, serum electrolytes, hematocrit and urinalysis. Chest X ray and 12 lead ECG are also important. It is important to avoid depletion of body volume and gradually changed the position.
Elderly patient is more likely to develop orthostatic hypotension as a result of autonomic neuropathy. Elderly patient is also more prone in developing post- prandial hypotension that occurs 45-60 minutes after a meal.
Children have a lower blood pressure than the adult. It is important to know the age related blood pressure to diagnose orthostatic hypotension in children. From birth to 3 months, 40-80mmHg is the normal systolic blood pressure. 80mmHg to 100mmHg from 3 months to 1 year and 100 mmHg plus 2 every year after 1 years old. (1- 12 years old). At 4 years old diastolic blood pressure is first present and normally it is 60mmHg. This will gradually increase to 70mmHg at 12 years of age. The causes of orthostatic hypotension are similar to adult.
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