Shock

Shock: Excerpt from Field Guide to Bedside Diagnosis

Differential Overview

Cardiogenic

❑ Anterior myocardial infarction

❑ Arrhythmia

❑ Dilated cardiomyopathy

❑ Aortic stenosis

❑ Acute mitral regurgitation

Obstructive

❑ Massive pulmonary embolism

❑ Pericardial tamponade

❑ Constrictive pericarditis

❑ Tension pneumothorax

Hypovolemic

❑ Hemorrhage

❑ Fluid depletion

Distributive

❑ Sepsis

❑ Anaphylaxis

❑ Adrenal insufficiency

❑ Neurogenic

Diagnostic Approach

A patient in shock will lie still, paying little attention to events around him. If agitated, he will answer in a weak voice. The pupils are dilated and react slowly to light. The coloration is gray and pale, with marbling of the skin on the back or the hands and legs, and cyanosis of the lips. The pulse is rapid and thready; temperature and blood pressure are low. Emergence of these findings corresponds to a 20% to 25% reduction in volume in low preload shock, a fall in the cardiac index to below 2.5 L/min/M ² or activation of mediators of the sepsis syndrome.

Clues to the underlying cause should be carefully searched for on physical examination. HEENT exam may reveal dilated or pinpoint pupils, dry conjunctivae, or scleral icterus. In the neck, jugular venous distension, delayed carotid upstroke, carotid bruits, or meningeal signs may be observed. Lung exam may show tachypnea, shallow breaths, rales, unilateral tympany or absent breath sounds. The cardiovascular exam may reveal tachycardia, bradycardia, irregular rhythm, S₃ gallop, right or left ventricular heave, murmurs, distant heart sounds, pulsus paradoxus, or rub. On abdominal exam, tenderness, guarding or rebound, high-pitched or absent bowel sounds, distension, pulsatile mass, hepatosplenomegaly, or ascites may be found. Rectal exam can reveal evidence of bleeding (occult positive, melena, or bright red blood) or decreased tone. The extremities can show a swollen calf or unequal pulses or blood pressures between the arms. Neurologic exam could exhibit agitation, confusion, delirium, obtundation, or coma. Finally, skin exam can reveal cool and clammy skin, warm and hyperemic skin, rashes, petechiae, urticaria, or cellulitis.

Prognosis in cardiogenic shock can be accurately stratified by Killip class, using observable clinical criteria:

Clinical Findings

Anterior myocardial infarction  Shock follows an episode of prolonged chest pain, when there is ischemic injury to 40% or more of left ventricular mass. In cardiogenic shock, pulmonary edema and a gallop rhythm are usually evident, the patient is frequently obtunded, there is oliguria, and the extremities are cold and cyanotic.

Arrhythmia  A rapid, slow, or irregular pulse will be felt. Acute atrial fibrillation, with a 25% decrease in ventricular filling, may produce hypotension in the presence of pre-existing left ventricular dysfunction.

Dilated cardiomyopathy  The patient presents with a gradual worsening of congestive heart failure, except in the setting of acute myocarditis, which can be recognized by the fever it produces.

Aortic stenosis  There is usually a loud upper right sternal border murmur that radiates into the carotids, but it may decrease in volume with a reduction in flow. The carotid upstroke will be delayed and small in volume (pulsus parvus et tardus). A₂ will be absent.

Acute mitral regurgitation  There will be a new loud apical systolic murmur with radiation to the axilla. This usually occurs with a ruptured papillary muscle caused by acute ischemia or myxomatous degeneration.

Massive pulmonary embolism  Acute-onset dyspnea, pleuritic chest pain, hemoptysis, and a swollen leg are all good clues, but these symptoms are variably present.

Pericardial tamponade  An exaggerated pulsus paradoxus, muffled heart sounds, and distended neck veins with Kussmaul sign (inspiratory filling) are present if the tamponade is advanced enough to cause hypotension.

Constrictive pericarditis  The findings are similar to pericardial tamponade, but there is no pulsus paradoxus.

Tension pneumothorax  Findings include an enlarged hemithorax with absent breath sounds, tympany to percussion, and a contralateral tracheal shift. It should be suspected in patients with trauma or mechanical ventilation.

Hemorrhage  Massive gastrointestinal hemorrhage with bright red blood or melena is usually evident, but occult bleeding, such as retroperitoneal hemorrhage or aortic dissection, may make the diagnosis more difficult.

Fluid depletion  Occurring in the setting of vomiting, diarrhea, burns, or dehydration in conditions such as diabetic ketoacidosis, fluid depletion can be recognized by such findings as decreased skin turgor and dry mucous membranes. The face is drawn, the eyes sunken, and the tongue dry and coated. The urine is decreased in volume and dark in color.

Sepsis  Spiking fever, rigors, and warm, mottled extremities are clues.

Anaphylaxis  Shock occurs cataclysmically after contact with allergens such as penicillin, sulfonamides, iodinated contrast, or hymenoptera venom. Additional findings include flushing, urticaria, angioedema, dyspnea, vomiting, diarrhea, and abdominal cramps.

Adrenal insufficiency  It should be considered in patients who chronically take steroids and in those with hyperpigmentation and orthostatic hypotension without evident cause.

Neurogenic  Spinal shock occurs in acute spinal cord transection, trauma with cord edema, or with a space-occupying spinal lesion. Acute cerebral hemorrhage can also cause hypotension.

Pictures

Book Source Details

• Book Title: Field Guide to Bedside Diagnosis
• Author(s): David S. Smith
• Year of Publication: 2007
• Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.

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More About This Book: Title: Field Guide to Bedside Diagnosis Authors: David S. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-78178-165-5

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