HYPOTENSION AND SHOCK

HYPOTENSION AND SHOCK: Excerpt from Differential Diagnosis in Primary Care

Many patients are told that they have a low blood pressure and are even treated for it when that blood pressure may be entirely normal for them. Asymptomatic hypotension may not be pathologic at all. At any rate, an expensive investigation into the causes of “hypotension” would seem unnecessary if the systolic pressure is above 80 mm Hg, especially when the patient is asymptomatic. The differential diagnosis of both hypotension and shock is best developed using physiology. There are three things that are necessary to sustain the blood pressure at the normal level: adequate blood volume, adequate cardiac output, and adequate tone in the arteries and arterioles. Alteration of any of these may produce hypotension. Low blood volume may result from any of the following conditions:

1. Hemorrhagic shock such as acute upper GI bleeding
2. Chronic blood loss (e.g., peptic ulcer) or anemia of decreased production (such as aplastic anemia) or increased destruction (hemolytic anemias)
3. Dehydration
4. Decreased sodium chloride (NaCl) in blood from pituitary and adrenal insufficiency, diuretics, diarrhea or vomiting, chronic nephritis, or severe diaphoresis
5. Decreased albumin in the blood from nephrosis, cirrhosis, and malnutrition or malabsorption syndrome.

Any one of the conditions listed above may be associated with hypotension. Decreased cardiac output usually results from CHF of many causes and from myocardial infarction. Many valvular lesions (e.g., mitral stenosis) may manifest hypotension without overt heart failure. Cor pulmonale may lead to hypotension from a decreased cardiac output. Decreased arterial tone (e.g., vasomotor shock) occurs in the following conditions:

1. When the sympathetic nerves are blocked by antihypertensive drugs (e.g., α -methyldopa, guanethidine, and pentolinium tartrate), by diabetic neuropathy, or after a sympathectomy
2. When there is increased vagal stimulation, as in neurogenic shock (common faint) and late stages of increased intracranial pressure
3. When toxins are introduced into the bloodstream from necrotic tissue, bacteria, or drugs that act directly on the arterioles

Examples of the last type of hypotension are pulmonary infarction (necrotic tissue), toxins, septicemia (bacterial toxins), and hydralazine therapy.

Approach to the Diagnosis

The workup of shock must be vigorous with emergency CBC, blood cultures, blood gases, ECG, electrolytes, blood urea nitrogen (BUN), and type- and cross-match of blood at the same time that vigorous antishock measures are applied. Checking the GI tract for blood loss with a rectal and nasogastric tube can be both diagnostic and therapeutic. To work up chronic hypotension, one should not forget venous pressure and circulation times (to diagnose decreased cardiac output and CHF), serial electrolytes and cortisol levels (to rule out adrenal insufficiency), and sedimentation rate and cultures of various body fluids (to exclude a chronic infectious disease [e.g., TB]).

Other Useful Tests

1. Blood volume study (dehydration, hypovolemic shock)
2. Electrolytes (Addison disease)
3. 24-hour blood pressure monitoring
4. ECG (CHF, valvular heart disease)
5. Visual field examination (pituitary tumor)
6. Thyroid profile (hypothyroidism)
7. CT scan of the brain (pituitary tumor)
8. Drug screen (drug or alcohol abuse)

CASE PRESENTATION #53 A 52-year-old white man complained of generalized fatigue, weight loss, and occasional diarrhea for the past year. His blood pressure was 75/50 mm Hg. He was treated for pulmonary TB several years ago.

Pictures

Book Source Details

• Book Title: Differential Diagnosis in Primary Care
• Author(s): R. Douglas Collins MD, FACP
• Year of Publication: 2007
• Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.

More About Hypotension

• Back to disease: Hypotension: Introduction
• Next Book Extract About Hypotension: Accurately measure the blood pressure (BP) in all pediatric patients older than age 3 and in youngerhigh-risk patients (Avoiding Common Pediatric Errors)
• More Book Extracts: All Online Books for Hypotension

More Medical Textbooks Online about Hypotension

Review other book chapters online related to Hypotension:

Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Differential Diagnosis in Primary Care Authors: R. Douglas Collins MD, FACP Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-7817-6812-8

 » Next page: Accurately measure the blood pressure (BP) in all pediatric patients older than age 3 and in youngerhigh-risk patients (Avoiding Common Pediatric Errors)

Rate This Website

What do you think about the features of this website? Take our user survey and have your say:

Website User Survey

Medical Tools & Articles:

Next articles:

• Accurately measure the blood pressure (BP) in all pediatric patients older than age 3 and in youngerhigh-risk patients (Avoiding Common Pediatric Errors)
• Surveys relating to Hypotension
• Ask Question about Hypotension

Tools & Services:

• Bookmark this page
• Symptom Search
• Symptom Checker
• Medical Dictionary
• Give your feedback

Medical Articles:

• Disease & Treatments Search
• Misdiagnosis Center
• Full list of interesting articles

Forums & Message Boards

• Ask or answer a question at the Boards:
• I cannot get a diagnosis. Please help.
• Tell us your medical story.
• Share your misdiagnosis story.
• What is the best treatment for my condition?
• See all the Boards.

Enter your search terms Submit search form
Search The Web Search wrongdiagnosis.com

Common Health Mistakes

Symptom
Checker

Search Specialists by State and City