FMST Student Manual - 2008 Web Edition*

Field Medical Training Battalion
Camp Lejeune

 FMST 1401

Manage Shock Casualties

TERMINAL LEARNING OBJECTIVES

1.    Given a shock casualty in a combat environment and standard field medical equipment and supplies, manage shock casualties, to prevent further injury or death. (FMST-HSS-1401)

ENABLING LEARNING OBJECTIVES

1.    Without the aid of references, given a description or list, identify standard medical terminology related to the cardiovascular system, per the student handout.  (FMST-HSS-1401a)

2.    Without the aid of references, given a description or title, identify the anatomy of the cardiovascular system, per the student handout.  (FMST-HSS-1401b)

3.    Without the aid of references, given a description or list, identify the causes of different types of shock, per the student handout.  (FMST-HSS-1401c)

4.    Without the aid of references, given a list of symptoms, identify the types of shock, per the student handout.   (FMST-HSS-1401d)

5.      Without the aid of references, given a list of symptoms of shock, identify the appropriate treatment, per the student handout.  (FMST-HSS-1401e)

6.    Without the aid of references, given a simulated shock casualty and the standard field medical equipment and supplies, manage shock casualties, per the student handout. (FMST-HSS-1401f)

 1.    OVERVIEW

Shock is regarded as a state of generalized cellular hypoperfusion in which delivery of oxygen to the cells is inadequate to meet metabolic needs.  There is no laboratory test to diagnose shock.  The initial step for managing shock in the injured patient is to recognize its presence.  By far, the most common cause of shock in the trauma casualty is hemorrhage and the safest approach in managing the trauma casualty in shock is to consider the cause of it as being hemorrhagic until proven otherwise.

2.    MEDICAL TERMINOLOGY RELATED TO SHOCK

Systolic Blood Pressure (SBP) - the force of the blood against blood vessels produced by ventricular contraction. (Normal systolic B/P = 120-140 mmHg)

Diastolic Blood Pressure (DBP) - the pressure remaining in the blood vessels while the heart is refilling. (Normal diastolic B/P = 60-80 mmHg)

Preload - the amount of blood returning into the heart from the systemic circulatory system (venous return).

Afterload - the resistance to blood flow that the heart must overcome to pump blood out to the arterial system.

Stroke Volume - amount of blood pumped by the heart with each contraction.

Capillary Refill Test - quick test performed on the nail beds as an indicator of tissue perfusion (normal = less than 3 seconds).

Nervous System - autonomic nervous system is divided into two components:

Sympathetic nervous system (controls the fight-or-flight response):  The goal of this system is to maintain sufficient amounts of oxygenated blood to critical areas while shunting blood away from nonessential areas.  Response includes:

- Heart beats faster and stronger

- Increases ventilations

- Constricts blood vessels of nonessential organs

- Dilates blood vessels of muscles 

Parasympathetic nervous system (rest and digest):  Division of the nervous system that maintains normal body functions.  Response includes:

- Heart beats slower

- Decreases ventilations

- Increases dilation of blood vessels to nonessential organs

 3.      ANATOMY OF THE CARDIOVASCULAR SYSTEM 

The cardiovascular system consists of the heart (a pump), the blood (circulating fluid), and the vascular system (the container that holds the blood).

Pump - the heart is a muscle composed of four chambers, the right side receives blood from the body and the left side pumps blood to the body.  For the heart to work effectively, an adequate amount of blood must be present in the ventricles (preload).  When the preload is decreased, the heart muscles are not stretched enough and the stroke volume is reduced.  Too much blood in the heart creates a state of increased afterload, also reducing the stroke volume.

Fluid - blood is composed of many substances.  Red blood cells (RBC) contain hemoglobin and carry oxygen.  White blood cells (WBC) are used by the body to fight infection.  Platelets in the blood are essential for clotting.  The volume of fluid within the container must equal the capacity of the vascular system in order to properly perfuse the tissues of the body.

Container - arteries, veins, and capillaries are the highways that take the blood throughout the body.  The aorta is the largest artery in the body.  At the smallest level, the capillaries may be no bigger than a single cell wide.  The size of the entire “container” is controlled by muscles in the walls of the arteries and veins.  These muscles are under the control of the brain via the sympathetic nervous system.  By expanding and contracting the vessels, the size of the container is altered. 

4.      TYPES OF SHOCK

Shock is classified by its cause.  Shock can occur in three ways that are associated with failure of some component of the cardiovascular system, the pump, volume, and container. The major types of shock are: Hypovolemic, Distributive, and Cardiogenic (see figure 2). 

 Figure 2.  Signs Associated with Types of Shock 

Hypovolemic Shock - a state of shock caused by any loss of fluid volume either by blood loss, dehydration, burns, etc.  The container has retained its normal size but the fluid volume has decreased, creating an imbalance.  The most common cause of hypovolemic shock on the battlefield is due to massive hemorrhage which causes hemorrhagic shock.  

The amount of blood that can be lost before death occurs will vary from individual to individual.  The average adult blood volume is 5 to 6 liters.  Normally, a loss of 25-40% of the person's total blood volume will create a life-threatening condition.  Massive hemorrhage may be fatal within 60-120 seconds.  In a tactical environment, treatment should not be delayed.  Controlling major hemorrhage should be the first priority over securing an airway.

Signs and symptoms seen with hemorrhagic shock are usually linked with the amount of blood lost and the casualty’s internal reaction to this blood loss.  DO NOT rely on BP as the main indicator of shock!  More attention should be paid to the casualty’s mental status, quality of distal pulses, and tachycardia.  Hemorrhagic shock, which is hypovolemic shock resulting from blood loss, can be categorized into four classes, depending on the severity of hemorrhage.  Remember these parameters are only guidelines and should not be taken as absolute amounts of associated blood loss (see figure 3).

 Figure 3.  Classes of Hemorrhagic Shock

Class I Shock - this stage has few clinical manifestations.  The casualty's body is able to compensate to maintain homeostasis. 

Class II Shock - although the circulating blood volume is reduced, compensatory mechanisms such as the sympathetic nervous system are able to maintain blood pressure and tissue perfusion at a level sufficient to prevent cellular damage.

Class III Shock - at this point, unfavorable signs begin to appear.  The body’s compensatory systems can no longer maintain adequate perfusion.  The classic signs of shock (tachycardia, tachypnea, and confusion) become obvious.  You can see the importance of catching the casualty in the early stages of shock because by the time the casualty gets to this stage, he or she is in significant trouble.

Class IV Shock - this is a severe stage of shock!  These casualties truly have only minutes to live.  Survival depends on immediate control of hemorrhage (surgery for internal hemorrhage) and aggressive resuscitation. 

Signs and Symptoms

See figure 2.

Treatment

As stated in the Manage Hemorrhage lesson, you must stop the bleeding.  Depending on which phase of field care you are in; Care Under Fire phase use a tourniquet for life-threatening extremity hemorrhage and Tactical Field Care phase use direct pressure and/or a hemostatic dressing.  Once the bleeding is stopped, obtain vascular access; give resuscitative fluids, and CASEVAC (see Combat Fluid Resuscitation lesson).

Distributive (Vasogenic) Shock - shock that occurs when the vascular container (blood vessels) dilate (enlarge) without a proportional increase in fluid volume.  As a result, the hearts preload decreases, and cardiac output falls.  There is still the same amount of blood in the blood vessels but they are dilated too much and not enough blood is returning to the heart.  Causes can be from spinal cord trauma, simple fainting, severe infections, or allergic reactions. 

Septic Shock - life threatening infections occurring primarily in a hospital setting.  Toxins are released into the bloodstream and cause blood vessels to dilate.  Septic shock and hypovolemic shock have many similar signs and symptoms.  Septic shock is virtually never encountered within minutes of an injury.  You should focus on prevention of septic shock.  The Committee on Tactical Combat Casualty Care recommends administering the oral antibiotic maxofloxacin and the parental (injectable) antibiotic ertepenem at the time of injury to prevent wound infections.  You will learn more about medications during the lesson on Casualty Assessment.

Signs and Symptoms

See figure 2.

Treatment

It usually takes between 5-7 days for septic shock to develop.  However, you may be called on to care for a casualty who sustained an injury and did not promptly seek medical attention.  If so, your primary focus should be to CASEVAC the casualty to a higher echelon of care.  Additionally, the casualty will require IV antibiotic therapy with a broad spectrum antibiotic. 

Neurogenic Shock - shock caused by an injury that interrupts the spinal cord's sympathetic nervous system pathway, resulting in significant dilation of peripheral arteries.  Because of the loss of sympathetic control of the vascular system which controls the smooth muscle in the walls of the blood vessels, the peripheral vessels dilate below the level of injury.

Signs and Symptoms (see figure 2 and below)

- Injuries consistent with spinal injury

- Bradycardia with hypotension (low heart rate with low blood pressure should be a red flag, start suspecting neurogenic shock)

- The casualty with neurogenic shock, in the absence of traumatic brain injury, is alert, orientated, and lucid (clear in the mind) when in the supine (laying down on back) position

Treatment

- Maintain ABC’s

- Spinal Immobilization (if mechanism of injury causes a high suspicion of  spinal injury)

- Oxygen therapy to keep oxygen saturation >92% (if available)

- Obtain IV access and give fluids, if necessary

- Trendelenburg position (head down, feet elevated)

- Keep patient warm

- CASEVAC

Psychogenic (Vasovagal) Shock - also known as vasovagal syncope or fainting, this occurs when there is stimulation of the tenth cranial nerve (vagus nerve) which produces bradycardia and hypotension.  If the bradycardia and hypotension are severe enough, cardiac output falls, resulting in insufficient blood flow to the brain and the casualty loses consciousness.  Usually, normal blood pressure is quickly restored before systemic impairment of perfusion occurs.  Common causes are fear, receiving unexpected bad news, or the sight of blood.

Signs and Symptoms (see figure 2 and below)

The periods of bradycardia and vasodilation are generally limited to minutes.

Treatment

Because it is a self-limited condition, a vasovagal episode is unlikely to result in true “shock” and normal blood pressure is quickly restored when the casualty is placed in a horizontal position. 

Cardiogenic Shock - failure of the heart to adequately pump blood throughout the body, resulting from causes that can be categorized as either intrinsic (a result of direct damage to the heart itself, a heart attack, for instance) or extrinsic (related to a problem outside the heart, a tension pneumothorax, for example).  In this scenario, the container is the correct size and is filled with the right amount of fluid, it’s the pump that is not functioning properly.

Intrinsic Causes:  Any injury that weakens the cardiac muscle will affect its output.  The damage may result from a myocardial infarction or from a direct bruise to the heart muscle from a blunt cardiac injury that prevents the heart from pumping properly.

Signs and Symptoms (see figure 2 and below)

- Abnormal pulse (irregular rate and rhythm)

- Chest pain

- Shortness of breath

- Nausea and vomiting

      Treatment

            - Maintain ABC’s

            - Obtain IV access

            - Oxygen therapy to keep oxygen saturation >92% (if available)

            - CASEVAC  

Extrinsic Causes:  External factors that cause the heart not to work properly (i.e., tension pneumothorax and cardiac tamponade)

Signs and Symptoms

            Tension Pneumothorax:

- Chest trauma

- Shortness of breath/dyspnea

- Tachycardia

- Cyanosis

- Decreased/absent lung sounds on affected side

- Jugular vein distention/tracheal deviation

Cardiac Tamponade:

- Chest Trauma

- Shortness of breath/dyspnea

- Tachycardia

- Cyanosis

- Distant heart tones

- Narrowing pulse pressure

Treatment

- Maintain ABC’s

- Oxygen therapy to keep oxygen saturation >92% (if available)

- CASEVAC

- Specific treatment for a tension pneumothorax is needle decompression, which will be discussed in a future lesson. 

5.  VOLUME RESUSCITATION

Although volume resuscitation of a trauma casualty in shock makes sense, no research has demonstrated improved survival of critically injured trauma casualties when IV fluid therapy has been administered in the field.  In fact, one researcher found that IV fluids administered in the field were beneficial only when three conditions existed:

a.       the casualty is bleeding at a rate of 25 to 100 mL/min

b.      the IV fluid administration rate is equal to the bleeding rate

c.       the scene time and transport time exceed 30 minutes

Therefore, transport of the trauma casualty should never be delayed to start an IV.

You will receive training on the type of vascular access (PO, IV, or IO) to start and the type of fluids to give in the lesson on Combat Fluid Resuscitation.

REFERENCES

Pre-Hospital Trauma Life Support, Military Edition, 6^th Ed, Chapters 7 & 21

Emergency War Surgery Handbook, NATO, 2004

 REV: July 2008

Shock Review

1.  List the three major types of shock.

2.   Describe the signs or symptoms associated with Class III Shock.

3.   List the two medications administered to prevent a casualty from developing septic shock.

4.  Which is more important for a casualty in shock, IV fluid or rapid transport?  Why?