Clinical Pearl Series Edited from Yale-G First Aid: Crush USMLE Step 2CK & Step 3 by Yale Gong, MD, Sr. Medical Advisor at www.medicine.net (Copyrighted)

Emergency Medicine is the specialty that focuses on the stabilization, diagnosis, and management of individuals with acute illness and injury. It also includes the management of trauma resuscitation, advanced cardiac life support, advanced airway management, poisonings, pre-hospital care, and disaster preparedness.

Life-saving Knowledge: Shock and Cardiopulmonary Resuscitation

Etiology

Many conditions can cause cardiopulmonary shock and arrest, including:

(1) Cardiac—coronary or ischemic heart disease (major cause), cardiomyopathy, arrhythmia, hypertensive heart disease, and congestive heart failure.

(2) Non-cardiac—trauma, intoxication, infection, anaphylaxis, pulmonary embolism, suffocation, and drowning, etc. They are fatal and require emergent resuscitation.

Essentials of diagnosis

1. Severe hypoxia and impending respiratory arrest: Tachycardia, respiratory distress with cyanosis, stridor, agitation, confusion, exhaustion, and poor chest movement.

2. Cardiogenic shock: Pale, cold extremities, hypotension, pulmonary edema, jugular vein distention (JVD), heart murmurs (+/-); decreased cardiac output (CO); increased central venous pressure (CVP), systemic vascular resistance (SVR), and pulmonary capillary wedge pressure (PCWP). These signs mostly indicate more than 40% left ventricular myocardial infarction (LVMI, the No.1 cause) and over 80% in-hospital mortality.

3. Hypovolemic shock (“Cold shock”): Pale, cold extremities, an orthostatic BP drop > 20 mmHg; decreased cardiac output, CVP, and PCWP; increased SVR. Supine hypotension with systolic BP < 90 mmHg is a late sign of shock. Massive hemorrhage is the most common cause.

4. Neurologic shock: Warm extremities; decreased cardiac output, CVP, SVR, and PCWP. Spinal cord injury in the cervical or thoracic region is the most common cause.

5. Septic shock: Warm and faint; increased cardiac output; decreased CVP and SVR. E. coli and S. aureus are the most common pathogens.

6. Anaphylactic shock: A rare, serious allergic reaction caused by medicines (aspirin, penicillin), insect bites, or certain foods (nuts, milk, fish, shellfish, eggs, some fruits). Typical presentations start in minutes to hours: itchy rash, swollen mouth/tougue, difficult breathing, vomiting, lightheadedness, loss of consciousness, low blood pressure, and medical shock.

7. Lab tests: Increased BUN:creatinine ratio, AST, and ALT.

Urgent treatment—critical care

1. Follow the order of “ABC” — “Airway, Breathing, and Circulation.”

(A) Airway: Assessment of airway. Endotracheal intubation is immediately indicated for severe stridor, cyanosis, hypoxia, hypoventilation, chest wall exhaustion, apnea, or unconsciousness with vomiting. Foreign-body airway obstruction: Back blows-chest thrusts (if < 1 y/a); Heimlich maneuver (if > 1 y/a).

(B) Breathing: Mechanical ventilation, along with high-flow oxygen. For cardiopulmonary arrest, compression-ventilation ratio is 5 to 1. In mechanically ventilated adults with critical illness in ICU, intermittent sedative-analgesic medications (morphine, propofol, midazolam) are recommended.

(C) Circulation: Intravenous (IV) access and fluid, along with cardiac monitoring (by ECG). Large volumes of fluids are needed for hypovolemic shock.

2. Cardiac arrest (unresponsive, pulseless):

(1) Ventricular fibrillation (V-fib) or ventricular tachycardia (V-tach): Immediate defibrillation with 200, 300 and 360j as needed. If the V-fib or V-tach persists, cardiopulmonary resuscitation (CPR), tracheal intubation, oxygen and IV lines are started. IV amiodarone (most effective) or lidocaine is the drug of choice for V-fib or V-tach. Other options are bretylium, MgSO4, etc.

(2) Asystole (or pulseless electrical activity, PEA):

The treatment of choice is epinephrine (EP) or adrenaline (Ad) 1mg IV push every 3 min; electrical therapy is not effective.

(3) Reversible asystole:

Hypoxia: Treat with oxygen and ventilation.

Hyperkalemia: Treat with IV 10% CaCl2 and NaHCO3.

Hypothermia (rectal T < 30^oC): Supply warmed IV fluid, oxygen, etc.

3. Anaphylactic shock:

The primary treatment of anaphylaxis is epinephrine injection into a muscle, intravenous fluids, then placing the person “in a reclining position with feet elevated to help restore normal blood flow.”