Blood pressure, decreased [Hypotension]
Low blood pressure refers to inadequate intravascular pressure to maintain the oxygen requirements of the body's tissues. Although commonly linked to shock, this sign may also result from a cardiovascular, respiratory, neurologic, or metabolic disorder. Hypoperfusion states especially affect the kidneys, brain, and heart, and may lead to renal failure, a change in the patient's level of consciousness (LOC), or myocardial ischemia. Low blood pressure may be drug-induced or may accompany diagnostic tests—most commonly those using contrast media. It may stem from stress or change of position—specifically, rising abruptly from a supine or sitting position to a standing position (orthostatic hypotension).
Normal blood pressure varies considerably; what qualifies as low blood pressure for one person may be normal for another. Consequently, every blood pressure reading must be compared against the patient's baseline. Typically, a reading below 90/60 mm Hg, or a drop of 30 mm Hg from the baseline, is considered low blood pressure.
Low blood pressure can reflect an expanded intravascular space (as in severe infections, allergic reactions, or adrenal insufficiency), reduced intravascular volume (as in dehydration and hemorrhage), or decreased cardiac output (as in impaired cardiac muscle contractility). Because the body's pressure-regulating mechanisms are complex and interrelated, a combination of these factors usually contributes to low blood pressure.
Action stat!
If the patient's systolic pressure is less than 80 mm Hg, or 30 mm Hg below his baseline, suspect shock. Quickly evaluate the patient for a decreased LOC. Check his apical pulse for tachycardia and his respirations for tachypnea. Inspect the patient for cool, clammy skin. Elevate the patient's legs above the level of his heart, or place him in Trendelenburg's position if the bed can be adjusted. Then insert a large-bore I.V. catheter to replace fluids and blood or to administer drugs. Prepare to administer oxygen with mechanical ventilation if necessary. Monitor the patient's intake and output and insert an indwelling urinary catheter to accurately measure urine output. The patient may need a central venous catheter or a pulmonary artery catheter to facilitate monitoring of his fluid status. Prepare for cardiac monitoring to evaluate cardiac rhythm. Be ready to insert a nasogastric tube to prevent aspiration in the comatose patient. Throughout emergency interventions, keep the patient's spinal column immobile until spinal cord trauma is ruled out.
History and physical examination
If the patient is conscious, ask him about associated symptoms. For example, does he feel unusually weak or fatigued? Has he had nausea, vomiting, or dark or bloody stools? Is his vision blurred? Is his gait unsteady? Does he have palpitations? Does he have chest or abdominal pain or difficulty breathing? Has he had episodes of dizziness or fainting? Do these episodes occur when he stands up suddenly? If so, take the patient's blood pressure while he's lying down, sitting, and then standing; compare readings. (See Ensuring accurate blood pressure measurement.)
A drop in systolic or diastolic pressure of 10 to 20 mm Hg or more and an increase in heart rate of more than 15 beats/minute between position changes suggest orthostatic hypotension.
Next, continue with a physical examination. Inspect the skin for pallor, sweating, and clamminess. Palpate peripheral pulses. Note paradoxical pulse—an accentuated fall in systolic pressure during inspiration—which suggests pericardial tamponade. Then auscultate for abnormal heart sounds (gallops, murmurs), rate (bradycardia, tachycardia), or rhythm. Auscultate the lungs for abnormal breath sounds (diminished sounds, crackles, wheezing), rate (bradypnea, tachypnea), or rhythm (agonal or Cheyne-Stokes respirations). Look for signs of hemorrhage, including visible bleeding and palpable masses, bruising, and tenderness. Assess the patient for abdominal rigidity and rebound tenderness; auscultate for abnormal bowel sounds. Carefully assess the patient for possible sources of infection such as open wounds.
Medical causes
Acute adrenal insufficiency.Orthostatic hypotension is characteristic with acute adrenal insufficiency, accompanied by fatigue, weakness, nausea, vomiting, abdominal discomfort, weight loss, fever, and tachycardia. The patient may also have hyperpigmentation of fingers, nails, nipples, scars, and body folds; pale, cool, clammy skin; restlessness; decreased urine output; tachypnea; and coma.
Anaphylactic shock.Following exposure to an allergen, such as penicillin or insect venom, a dramatic fall in blood pressure and narrowed pulse pressure signal anaphylactic reaction. Initially, anaphylactic shock causes anxiety, restlessness, a feeling of doom, intense itching (especially of the hands and feet), and pounding headache. Later, it may also produce weakness, sweating, nasal congestion, coughing, difficulty breathing, nausea, abdominal cramps, involuntary defecation, seizures, flushing, change or loss of voice due to laryngeal edema, urinary incontinence, and tachycardia.
Anthrax (inhalation).Inhalation anthrax is caused by inhalation of aerosolized spores. Initial signs and symptoms are flulike and include fever, chills, weakness, cough, and chest pain. The disease generally occurs in two stages with a period of recovery after the initial signs and symptoms. The second stage develops abruptly with rapid deterioration marked by fever, dyspnea, stridor, and hypotension, generally leading to death within 24 hours. Radiologic findings include mediastinitis and symmetric mediastinal widening.
Cardiac arrhythmias.With an arrhythmia, blood pressure may fluctuate between normal and low readings. Dizziness, chest pain, difficulty breathing, light-headedness, weakness, fatigue, and palpitations may also occur. Auscultation typically reveals an irregular rhythm and a pulse rate greater than 100 beats/ minute or less than 60 beats/minute. A life-threatening arrhythmia may cause absence of a pulse and no palpable blood pressure and requires emergency resuscitation measures.
Cardiac contusion.With cardiac contusion, low blood pressure occurs along with tachycardia and, at times, anginal pain and dyspnea.
Cardiac tamponade.An accentuated fall in systolic pressure (more than 10 mm Hg) during inspiration, known as paradoxical pulse, is characteristic in patients with cardiac tamponade. This disorder also causes restlessness, cyanosis, tachycardia, jugular vein distention, muffled heart sounds, dyspnea, and Kussmaul's sign (increased venous distention with inspiration).
Cardiogenic shock.A fall in systolic pressure to less than 80 mm Hg or to 30 mm Hg less than the patient's baseline because of decreased cardiac contractility is characteristic in patients with cardiogenic shock. Accompanying low blood pressure are tachycardia, narrowed pulse pressure, diminished Korotkoff sounds, peripheral cyanosis, and pale, cool, clammy skin. Cardiogenic shock also causes restlessness and anxiety, which may progress to disorientation and confusion. Associated signs and symptoms include angina, dyspnea, jugular vein distention, oliguria, ventricular gallop, tachypnea, and a weak, rapid pulse.
Cholera.Cholera may be mild and with uncomplicated diarrhea or severe and life-threatening. Signs include abrupt watery diarrhea and vomiting. Severe fluid and electrolyte loss leads to thirst, weakness, muscle cramps, decreased skin turgor, oliguria, tachycardia, and hypotension. Without treatment, death can occur within hours.
Diabetic ketoacidosis.Hypovolemia triggered by osmotic diuresis in hyperglycemia is responsible for the low blood pressure associated with diabetic ketoacidosis, which is usually present in patients with type 1 diabetes mellitus. It commonly produces polydipsia, polyuria, polyphagia, dehydration, weight loss, abdominal pain, nausea, vomiting, breath with fruity odor, Kussmaul's respirations, tachycardia, seizures, confusion, and stupor that may progress to coma.
Heart failure.With heart failure, blood pressure may fluctuate between normal and low readings. A precipitous drop in blood pressure may signal cardiogenic shock. Other signs and symptoms of heart failure include exertional dyspnea, dyspnea of abrupt or gradual onset, paroxysmal nocturnal dyspnea or difficulty breathing in the supine position (orthopnea), fatigue, weight gain, pallor or cyanosis, sweating, and anxiety. Auscultation reveals ventricular gallop, tachycardia, bilateral crackles, and tachypnea. Dependent edema, jugular vein distention, increased capillary refill time, and hepatomegaly may also occur.
Hyperosmolar hyperglycemic
nonketotic syndrome (HHNS).HHNS, which is common in the patient with type 2 diabetes mellitus, decreases blood pressure—at times dramatically—if he loses significant fluid from diuresis due to severe hyperglycemia and hyperosmolarity. It also produces dry mouth, poor skin turgor, tachycardia, confusion progressing to coma and, occasionally, generalized tonic-clonic seizure.
Hypovolemic shock.A fall in systolic pressure to less than 80 mm Hg or 30 mm Hg less than the patient's baseline, secondary to acute blood loss or dehydration, is characteristic in hypovolemic shock. Accompanying it are diminished Korotkoff sounds, a narrowed pulse pressure, and a rapid, weak, and irregular pulse. Peripheral vasoconstriction causes cyanosis of the extremities and pale, cool, clammy skin. Other signs and symptoms include oliguria, confusion, disorientation, restlessness, and anxiety.
Hypoxemia.Initially, blood pressure may be normal or slightly elevated, but as hypoxemia becomes more pronounced, blood pressure drops. The patient may display tachycardia, tachypnea, dyspnea, and confusion and may progress from stupor to coma.
Myocardial infarction (MI).With MI, a life-threatening disorder, blood pressure may be low or high. A precipitous drop in blood pressure may signal cardiogenic shock. Associated signs and symptoms include chest pain that may radiate to the jaw, shoulder, arm, or epigastrium; dyspnea; anxiety; nausea or vomiting; sweating; and cool, pale, or cyanotic skin. Auscultation may reveal an atrial gallop, a murmur and, occasionally, an irregular pulse.
Neurogenic shock.The result of sympathetic denervation due to cervical injury or anesthesia, neurogenic shock produces low blood pressure and bradycardia. The patient's skin remains warm and dry because of cutaneous vasodilation and sweat gland denervation. Depending on the cause of shock, there may also be motor weakness of the limbs or diaphragm.
Pulmonary embolism.Pulmonary embolism causes sudden, sharp chest pain and dyspnea accompanied by a cough and, occasionally, a low-grade fever. Low blood pressure occurs with a narrowed pulse pressure and diminished Korotkoff sounds. Associated signs include tachycardia, tachypnea, a paradoxical pulse, jugular vein distention, and hemoptysis.
Septic shock.Initially, septic shock produces fever and chills. Low blood pressure, tachycardia, and tachypnea may also develop early, but the patient's skin remains warm. Low blood pressure becomes increasingly severe—less than 80 mm Hg or 30 mm Hg less than the patient's baseline—and is accompanied by narrowed pulse pressure. Other late signs and symptoms include pale skin, cyanotic extremities, apprehension, thirst, oliguria, and coma.
Vasovagal syncope.Vasovagal syncope is the transient loss or near-loss of consciousness that's characterized by low blood pressure, pallor, cold sweats, nausea, palpitations or slowed heart rate, and weakness following stressful, painful, or claustrophobic experiences.
Other causes
Diagnostic tests.Diagnostic tests include the gastric acid stimulation test using histamine and X-ray studies using contrast media. The latter may trigger an allergic reaction, which causes low blood pressure.
Drugs.Calcium channel blockers, diuretics, vasodilators, alpha- and beta-adrenergic blockers, general anesthetics, opioid analgesics, monoamine oxidase inhibitors, anxiolytics (such as benzodiazepines), tranquilizers, and most I.V. antiarrhythmics (especially bretylium tosylate) can cause low blood pressure.
Nursing considerations
▪ Check the patient's vital signs frequently to determine if low blood pressure is constant or intermittent.
▪ If blood pressure is extremely low, assist in the insertion of an arterial catheter to allow close monitoring of pressures; alternatively, a Doppler flowmeter may be used.
▪ Prepare the patient for laboratory tests, which may include urinalysis, routine blood studies, an electrocardiogram, and chest, cervical, and abdominal X-rays or computed tomography scans.
▪ Administer fluid, blood products, and medication as ordered to improve blood pressure.
Patient teaching
▪ Advise the patient with orthostatic hypotension to stand up slowly from a sitting or lying position.
▪ For the patient with vasovagal syncope, discuss how to avoid triggers.
▪ Emphasize the importance of dangling the feet and rising slowly when getting out of bed.
▪ Explain diagnostic tests and procedures.
▪ Explain the underlying disorder and treatment plan.
Pictures
![Blood pressure, decreased [Hypotension] - 5492.1.png](/bookimages/16/5492.1.png)
Book Source Details
- Book Title: Nursing: Interpreting Signs and Symptoms
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.
Other Book Chapters Related to Low blood pressure
Read excerpts from these other book chapters related to Low blood pressure:
Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2008 Williams & Wilkins.
More About Causes of Low blood pressure
» Next page: Orthostatic hypotension [Postural hypotension] (Nursing: Interpreting Signs and Symptoms)
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