HYPOTENSION

HYPOTENSION – Etiology, Pathophysiology, Clinical Manifestations, Diagnostic Evaluations, Treatment Management and Prevention

• Low blood pressure means that blood pressure is lower (less than 90/60 mm Hg) than normal (< 120/80 mm Hg) called hypotension
• Low blood pressure occurs when blood pressure is much lower than normal. This means the heart, brain, and other parts of the body do not get enough blood. Normal blood pressure is usually between 90/60 mm Hg and 130/80 mm Hg.

ETIOLOGY

• Dehydration: it is common among patients with prolonged nausea, vomiting, diarrhea, or excessive exercise which shunts blood away from the organs to the muscles. Large amounts of water are lost when vomiting and with diarrhea, especially if the person does not drink adequate amounts of fluid to replace the depleted water.
• Moderate or severe bleeding: it can quickly deplete an individual’s body of blood, leading to low blood pressure or orthostatic hypotension. Bleeding can result from trauma, surgical complications, from GI abnormalities, such as ulcers, tumors, or diverticulosis. Occasionally, the bleeding may be so severe and rapid (ruptured aortic aneurysm) that it causes shock and death rapidly.
• Severe inflammation of organs inside the body: such as acute pancreatitis can cause low blood pressure. In acute pancreatitis, fluid leaves the blood vessels to enter the inflamed tissues around the pancreas as well as the abdominal cavity, concentrating blood and reducing its volume.
• Weakened heart muscle: can cause the heart to fail and reduce the amount the blood is pumps. One common cause of weakened heart muscle is the death of a large portion of the heart’s muscle due to a single, large heart attack or repeated smaller heart attacks.
• Pericarditis: it is an inflammation of the pericardium. Pericarditis can cause fluid to accumulate within the pericardium and compress the heart, restricting the ability of the heart to expand, fill, and pump blood.
• Pulmonary embolism: it is a condition in which a blood clot in a vein (deep vein thrombosis) breaks off and travels to the heart and eventually the lung. A large blood clot can block the flow of blood into the left ventricle from the lungs and severely diminish the blood returning to the heart for pumping. Pulmonary embolism is a life-threatening emergency.
• Bradycardia: it can decrease the amount of blood pumped by the heart. The resting heart rate for a healthy adult is between 60 and 100 beats/minute. Bradycardia does not always cause low blood pressure. In fact, some highly trained athletes can have resting heart rates in the 40s and 50s (beats per minute) without any symptoms. The slow heart rates are offset by more forceful contractions of the heart that pump more blood than in nonathletes. But in many patients, bradycardia can lead to low blood pressure, light-headedness, dizziness, and even fainting.
• Sick sinus syndrome: sick sinus syndrome occurs when the diseased electrical system of the heart cannot generate electrical signals fast enough to maintain a normal heart rate.
• Heart block: heart block occurs when the specialized tissues that transmit current in the heart are damaged by heart attacks, degeneration from atherosclerosis, and medications. Heart block prevents some or all of the electrical signals from reaching parts of the heart, and this prevents the heart from contracting as well as it otherwise would.
• Drug toxicity: drugs such as digoxin or beta blockers for high blood pressure can slow the transmission of electricity in the heart chemically and can cause bradycardia and hypotension
• Tachycardia: it also can cause low blood pressure. The most common example of tachycardia causing low blood pressure in atrial fibrillation. Atrial fibrillation is a disorder of the heart characterized by rapid and irregular electrical discharges from the muscle of the heart causing the ventricles to contract irregularly and rapidly. The rapidly contracting ventricles do not have enough time to fill maximally with blood before each contraction, and the amount of blood that is pumped decreases in spite of the faster heart rate. Other normally rapid heart rhythms such as ventricular tachycardia also can produce low blood pressure, sometimes even life-threatening shock
• Medications

Medications, such as calcium channel blockers, beta blockers, and digoxin can slow the rate at which the heart contracts. Some elderly people are extremely sensitive to these medications since they are more likely to have diseased hearts and electrical conduction tissues. In some individuals, the heart rate can become dangerously slow even with small doses of these medications.

Medication used in treating high blood pressure (such as ACE inhibitors, angiotensin receptor blockers, beta blockers, calcium channel blockers, and alpha blockers) can excessively lower blood pressure and result in symptomatic low blood pressure, especially among the elderly.

Diuretics, such as hydrochlorothiazide and furosemide (lasix) can decrease blood volume by causing excessive urination

Medications used for treating depression, such as amitriptyline, parkinson’s disease, such as levodopa-cardidopa and erectile dysfunction (impotence)

Alcohol and narcotics can also cause low blood pressure

• Vasovagal reaction: it is a common condition in which a healthy person temporarily develops low blood pressure, slow heart rate, and sometimes, fainting. A vasovagal reaction typically is brought on by emotions of fear or pain, such as having blood drawn, starting an intravenous infusion, or by gastrointestinal upset. Vasovagal reactions are caused by activity of the involuntary (autonomic) nervous system, especially the vagus nerve, which releases hormones that slow the heart and widen the blood vessels. The vagus nerve also controls digestive tract function and senses activity in the digestive system. Thus, some people can have a vasovagal reaction from straining at a bowel movement or vomiting.
• Postural hypotension: it is a sudden drop in blood pressure when an individual stands up from a sitting, squatting, or supine (lying) position. When a person stands up, gravity causes blood to settle in the veins in the legs so that less blood returns to the heart for pumping, and as a result, the blood pressure drops.
• Micturition syncope: it is a temporary drop in blood pressure and loss of consciousness brought about by urinating. This condition typically occurs in elderly patients and may be due to the release by the autonomic nerves of hormones that lower blood pressure.
• Adrenal insufficiency: addison’s disease can cause low blood pressure. It is a disorder in which the adrenal glands are destroyed. The destroyed adrenal glands can no longer produce sufficient adrenal hormones (specifically cortisol) necessary to maintain normal bodily functions. Cortisol has many functions, one of which is to maintain blood pressure and the function of the heart. Addison’s disease is characterized by weight loss, muscle weakness, fatigue, low blood pressure, and sometimes, darkening of the skin.
• Septicemia: it is a severe infection in which bacteria (or other infectious organisms such as fungi) enter the blood. The infection typically originates in the lungs, bladder, or in the abdomen due to diverticulitis or gallstones. The bacteria then enter the blood where they release toxins and cause life-threatening and profound low blood pressure (septic shock), often with damage to several organs.
• Anaphylaxis (anaphylactic shock): it is a potentially fatal allergic reaction to medications, such as penicillin, intravenous iodine used in some X-ray studies, foods such as peanuts, or bee stings (insect stings). In addition to a severe drop in blood pressure, individuals may also experience hives and wheezing due to constriction of the airways, and a swollen throat which cause difficulty breathing. The shock is caused by enlargement of blood-containing blood vessels and escape of water from the blood into the tissues.

PATHOPHYSIOLOGY

Blood pressure is continuously regulated by the autonomic nervous system —- using an elaborate network of receptors, nerves and hormones —- to balance the effects of the symptomatic nervous system which tends to raise blood pressure, and the parasympathetic nervous system, which lowers it —- the vast and rapid compensation abilities of the ANS —- allow normal individuals to maintain an acceptable blood pressure over a wide range of activities and in many disease states

CLINCIAL MANIFESTATIONS

• Chest pain
• Shortness of breath
• Irregular heartbeat
• Fever higher than 38.3 degree celcius
• Headache
• Stiff neck
• Severe upper back pain
• Cough with phlegm
• Prolonged diarrhea or vomiting
• Dyspepsia (indigestion)
• Dysuria (painful urination)
• Adverse effect of medications
• Acute, life-threatening allergic reaction
• Seizures
• Loss of consciousness
• Profound fatigue
• Temporary blurring or loss of vision
• Connective tissue disorder (Ehlers-Danlos syndrome)
• Black tarry stools

DIAGNOSTIC EVALUATION

• Complete blood count: CBC may reveal anemia from blood loss or elevated white blood cells due to infection
• Blood electrolyte measurements: it may show dehydration and mineral depletion, renal failure or acidosis
• Cortisol levels: it can be measured to diagnose adrenal insufficiency and Addison’s disease
• Blood and urine culture: it can be performed to diagnose septicemia and bladder infections, respectively.
• Radiology studies: such as chest X-rays, abdominal ultrasounds, and computerized tomography (CT or CAT) scans may detect pneumonia, heart failure, gallstones, pancreatitis and diverticulitis.
• Electrocardiogram: ECG can detect abnormally slow or rapid heartbeats, pericarditis, and heart muscle damage from either previous heart attacks or a reduced supply of blood to the heart muscle that has not yet caused a heart attack
• Holter monitor recordings: these are used to diagnose intermittent episodes of abnormal heart rhythms. A Holter monitor is a continuous recording of the heart’s rhythm for 24 hours that often is used to chart and diagnose intermittent episodes of bradycardia or tachycardia
• Patient-activated event recorder: if the episodes of bradycardia or tachycardia are infrequent, a 24-hour Holter recording may not capture these sporadic episodes. In this situation, a patient can wear a patient-activated event recorder for up to 4 weeks. The patient presses a button to start the recording when he or she senses the onset of an abnormal heart rhythm or symptoms possibly caused by low blood pressure. The doctor then analyzes the recordings at a later date to identify the abnormal episodes
• Echocardiograms: echocardiograms can detect pericardial fluid due to pericarditis, the extent of heart muscle damage from heart attacks, diseases of the heart valves, and rare tumors of the heart.
• Tilt-table tests: it is used to evaluate patients suspected of having postural hypotension or syncope due to abnormal function of the autonomic nerves. During a tilt-table test, the patient lies on an examination table with an intravenous infusion administered while the heart rate and blood pressure are monitored. The table then is tilted upright for 15 minutes to 45 minutes. Heart rate and blood pressure are monitored every few minutes. The purpose of the test is to try to reproduce postural hypotension. Sometimes a doctor may administer epinephrine intravenously to induce postural hypotension

TREATMENT MANAGEMENT

• Trendelenburg position: lying the person in dorsal decubitus position and lifting the legs increase venous return, thus making more blood available to critical organs in the chest and head
• Electrolytes to a diet can relieve symptoms of mild hypotension
• A morning dose of caffeine can also be effective
• Volume resuscitation (usually with crystalloid)
• Blood pressure support with a vasopressor, e.g. dopamine
• Ensure adequate tissue perfusion (maintain SvO₂ >70 with use of blood of dobutamine)
• Address the underlying problem (i.e. antibiotic for infection, stent or CABG (coronary artery bypass graft surgery) for infarction, steroids for adrenal insufficiency, etc)

Medium-term treatments of hypotension include:

• Blood sugar control (80-150 by one study)
• Early nutrition (by mouth or by tube to prevent ileus)
• Steroid support

According to diseases condition:

• Dehydration: it is treated with fluids and minerals (electrolytes)

Mild dehydration without nausea and vomiting can be treated with oral fluids and electrolytes

Moderate to severe dehydration usually is treated in the hospital or emergency room with intravenous fluids and electrolytes

• Blood loss: it can be treated by treating the cause of the bleeding, and with intravenous fluids and blood transfusions. Continuous and severe bleeding needs to be treated immediately
• Septic shock: it is a medical emergency and is treated with intravenous fluids and antibiotics
• Blood pressure medications or diuretics: there are adjusted, changed, or stopped by the doctor if they are causing low blood pressure symptoms
• Bradycardia: it may be due to a medication. Then change, or stop the medication
• Pacemaker: bradycardia due to sick sinus syndrome or heart block is treated with an implantable pacemaker
• Tachycardia: it is treated depending on the nature of tachycardia. Atrial fibrillation can be treated with oral medications, electrical cardioversion, or a catheterization procedure called pulmonary vein isolation. Ventricular tachycardia can be controlled with medications or with an implantable defibrillator
• Pulmonary embolism and deep vein thrombosis are treated with blood thinners, intravenous initially with heparin. Later, oral warfarin or other oral medications are substituted for heparin
• Pericardial fluid from pericarditis can be removed by a procedure called pericardiocentesis
• Postural hypotension

Changes in diet, such as increasing water and salt intake

Increasing intake of caffeinated beverages (because caffeine constricts blood vessels)

Using compression stockings to compress the leg veins and reduce the pooling of blood in the leg veins

Pyridostigmine, an anticholinesterase medication, works on the autonomic nervous system, especially when a person is standing up

• Postprandial hypotension refers to low blood pressure occurring after meals. Ibuprofen or indomethacin may be beneficial
• Vasovagal syncope: it can be treated with several types of drugs, such as:

Beta blockers: propranolol

Selective serotonin reuptake inhibitors: fluoxetine, escitalopram oxalate, paroxetine, sertraline, citalopram and fluvoxamine

Fludrocortisone: a drug that prevents dehydration by causing the kidneys to retain water also may be used

Pacemaker can also be helpful when a patient fails drug therapy

PREVENTION

• Stand up slowly
• Drink more water
• Drink little or no alcohol
• Limit or avoid caffeine
• Wear compression stockings