SHOCK

INTRODUCTION

Optimal patient care requires that the EMT-I understand the physiology of shock. The following topics will be discussed during this lesson:

· Review of the cardiovascular system

· Pathophysiology of shock

· Signs and symptoms of shock

· Classifications of shock

· Assessment of patients in shock

· Field treatment and transport decisions for shock patients

LESSON OBJECTIVES

At the end of this lesson the participants will be able to:

1. Identify the structure and function of the cardiovascular system.

2. Define shock.

3. Explain the shock mechanism and the body’s defense mechanisms.

4. Describe the pathophysiology of hypovolemic, cardiogenic, and neurogenic shock.

5. Recognize the signs and symptoms of shock.

6. Discuss the proper method of assessing the patient in shock.

7. Identify abnormal findings during the assessment of patients in shock.

8. In a given situation, properly treat a patient in shock.

9. In a given situation, be able to determine where the patient should be transported.

KEY VOCABULARY

The following terms will be used during this lesson:

• Perfusion - blood flow into or through tissue.

• Shock - inadequate perfusion.

• PVR (Peripheral Vascular Resistance) - resistance to blood flow due to the peripheral blood vessels.

KEY CONCEPTS

The following section provides information and space for taking notes on the key concepts discussed by the instructor.

REVIEW OF THE CARDIOVASCULAR SYSTEM

Heart (the “pump”)

· Hollow muscular organ, which functions as a pump to circulate blood throughout the blood vessels.

· Right side of the heart receives unoxygenated blood from the venous system and pumps it to the lungs where it exchanges oxygen and waste products.

· Left side of the heart receives the oxygen enriched blood and pumps it to the organs and peripheral tissues via the arterial system.

· Stroke Volume (SV): Volume of blood ejected with each ventricular contraction; normal stroke volume = 60-130 ml

· Heart Rate (HR): Number of heart beats per minute

· Cardiac Output (CO): Amount of blood pumped by the heart in one minute; expressed in liters per minute (L/min)

· Stroke volume x heart rate = cardiac output

· SV x HR = CO

· Example: (SV) 70ml x (HR) 75/min = 532 ml/min or 5.3 L/min

Blood vessels (the “containers” or “pipes”)

· Comprised of a complex network of veins, arteries, and capillaries.

· Diameter of the smaller arteries is controlled by the sympathetic nervous system and determines the peripheral vascular resistance (PVR).

· As the arterial vessels narrow, resistance to blood flow increases; conversely, the more they dilate the lower the resistance will be.

Blood pressure

· Average pressure in the arteries throughout the cardiac cycle.

· Depends on the elastic properties of the arterial walls and blood volume in the arterial system; therefore, it depends on the cardiac output and the peripheral vascular resistance.

· Constantly regulated to maintain tissue perfusion during a wide range of conditions, i.e., exercise, change in position, change in blood volume, etc.

· BP = CO x PVR

Blood (the “fluid”)

· Delivers oxygen and nutrients to tissues; carries waste products away from tissues to be eliminated.

· Cardiovascular system (a closed system) must contain an adequate volume of blood to fill its structures as well as supply an adequate amount of blood cells to assure oxygenation.

· Normal circulating blood volume = 4.5 - 5 liters (L) or 70 ml/kg of body.

PATHOPHYSIOLOGY OF SHOCK

Shock

· Inadequate perfusion or inadequate blood flow to body tissues.

· Can lead to decreased cellular function and ultimately cell death.

· Caused when any component of the cardiovascular system fails.

Compensatory mechanisms

The body attempts to compensate and restore perfusion by:

· Increasing cardiac output

· Stimulation of the sympathetic nervous system causes an increase in heart rate, stroke volume, and PVR.

· Redistributing the circulating blood volume to vital organs

· Vasoconstriction

· Release of antidiuretic hormone (ADD) and renin to decrease urine production.

· Increasing oxygen delivery to cells

· Stimulation of sympathetic nervous system causes bronchodilation, increased respirations, and tidal volume.

SIGNS AND SYMPTOMS OF SHOCK

Early Stage (compensated shock): Compensatory mechanisms are able to maintain perfusion of vital organs

Heart Rate: mild tachycardia; bounding pulse

Level of Consciousness: lethargy, confusion, combativeness

Skin: delayed capillary refill; cool and clammy

Blood Pressure: normal or slightly elevated

Respirations: rapid and shallow

Middle Stage (uncompensated shock): Compensatory mechanisms are unable to maintain perfusion

Heart Rate: moderate tachycardia; weak and thready pulse

Level of Consciousness: confusion or unconsciousness

Skin: delayed capillary refill; cold, clammy, and cyanotic

Blood Pressure: decreased

Respirations: rapid and shallow

Late Shock

Heart Rate: bradycardia; severe dysrhythmias

Level of Consciousness: coma

Skin: pale, cold, marked diaphoresis

Blood Pressure: marked hypotension

Respirations: decreased rate and tidal volume

CLASSIFICATIONS OF SHOCK

• Hypovolemic

• Cardiogenic

• Neurogenic

• Anaphylactic

• Septic

Hypovolemic Shock

	• Pathophysiology: Inadequate blood volume • Causes: • Hemorrhage (internal or external) • Acute dehydration (diarrhea, vomiting, shifting of fluids out of the vascular space due to burns, diabetic ketoacidosis, etc.)
Field Management • BLS Procedures • Control bleeding • High flow oxygen • Shock position (consider Trendelenburg position for suspected spinal injury without head trauma) • Assist with ALS procedures • ALS Procedures • Advanced airway PRN • Monitor • Venous access • Fluid resuscitation •

Cardiogenic Shock