ShockShock

Daniel T. Johnston, MD, MPHMAJ, US Army MC

Department of Military and Emergency Medicine

2004 Johnston, MD

Shock

1. Describe the basic underlying pathology that exists in all forms of shock.

2. List the different types of shock.3. List the stages of shock.4. Describe the pathologic changes that occur in

patients who are in hemorrhagic shock5. Describe the general appearance and behavior

of a patient in hemorrhagic shock.

2004 Johnston, MD

What “Shock” is not

2004 Johnston, MD

What is “Shock?”

A medical condition, not a diagnosis Types:

– Hypovolemic (eg. Hemorragic)– Cardiogenic– Distributive (eg. Septic, neurogenic)– Obstructive (eg. Cardiac tamponade, Tension

Pneumothorax)

TYPES OF SHOCK

More than 100 TYPES OF SHOCK have been described– Often classified by the cause of the syndrome– Two or more types are often combined

• Hypovolemia may occur with septic shock• Elements of cardiogenic shock may occur in

other types of shock

The threeessential patternsof circulatoryshock

I II III

TYPES OF SHOCK

Regardless of the classification, the underlying defect is always inadequate tissue perfusion!!!!

Shock

• Tissue injury from trauma may exacerbate shock by causing microemboli and further activating the inflammatory and coagulation systems

BLOOD AND ITS COMPONENTS

Blood volume:– Average adult male has a blood

volume of 7% of total body weight (approx. 5 Kg or 5 L of blood)

– Average adult female has a blood volume of 6.5% of body weight

BLOOD AND ITS COMPONENTS

Red blood cells (erythrocytes) (RBCs):– Transport 99% of blood oxygen

• Remaining 1% is carried dissolved in plasma (0.3 ml O2/100 ml of blood)

– Make up approximately 45% of the blood (Hct) and are the most abundant cells in the body

BLOOD AND ITS COMPONENTS

Red blood cells (erythrocytes) (RBCs):– Provide oxygen to tissues and remove

carbon dioxide– Each RBC contains approximately 270

million hemoglobin molecules• Allow RBCs to pick up oxygen in the lungs and

release it to body tissues

FLUIDS AND ELECTROLYTES

Water is the main component of body mass:–Accounting for 50%-60% of

body weight in adults

Tissue Cells

InterstitialFluid in theInterstitialSpace

FluidSpaces

Basic Physiology of Basic Physiology of Hypovolemic ShockHypovolemic Shock

2004 Johnston, MD

Causes

Anything that causes rapid fluid loss– Most commonly rapid blood loss: penetrating

trauma, GI, acute internal blood loss– Also be caused by fluid loss: can you name 2?– We will focus on blood loss

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Pathophysiology

Acute hemorrhage results in a physiologic response from 4 systems: – Hematologic: Coagulation and Constriction– Cardiovascular: Inc. HR, SVR, Contractility;

blood shunted to heart, brain, kidneys and away from skin, muscle, GI tract

– Renal: Increase Renin production– Neuroendocrine: ADH release

STAGES OF SHOCKSTAGES OF SHOCK

THREE “DISTINCT” STAGES– COMPENSATED SHOCK– DECOMPENSATED SHOCK– “IRREVERSIBLE” SHOCK

With small volume and pressure declines, compensations canrestore pressure. If losses are large, no recovery may be possible

Time

Outcomes of same vol. lost over diff. periods of time. Slow losses (III, IV)allow compensations to take effect. Rapid loss (I, II) of same vol. is fatal

STAGES OF SHOCK

Compensated Shock– Entails some decreased tissue perfusion, but

the body's compensatory responses are sufficient to overcome the decrease in available fluid

– Cardiac output and a normal systolic blood pressure are maintained by increasing catecholamine production

STAGES OF SHOCK

Compensated Shock – Rate & Depth of Respirations Increase– The decrease in perfusion and the subsequent

increase in acidosis lead to a chemoreceptor response that increases the rate and depth of ventilation so as to -

• decrease metabolic acidosis by decreasing PCO2

STAGES OF SHOCK Compensated Shock

– Sympathetic stimulation:• Sympathetic constriction of veins decreases amount of blood

held in veins causing BP and Cardiac Output (CO) to be maintained.

• Increases heart rate and contractility (inc. cardiac output) - BP and CO are maintained

• Constriction of the arteries leading to increased peripheral vascular resistance (BP is maintained) - and decreased capillary flow (cool skin)

• Creates bronchodilation (improved air exchange)

STAGES OF SHOCK

COMPENSATED SHOCK– If the underlying cause of shock is

untreated, the compensatory mechanisms eventually collapse

Low Flow

Micro-CirculatorySystem

AV Shunt

Precapillary Sphincter

Control of A-V Shunt by Precapillary Sphincter

STAGES OF SHOCK COMPENSATED SHOCK - Vasoconstriction: Progression of shock in the microcirculation

produces a sequence of changes in capillary perfusion– Vasoconstriction begins as minimal perfusion to

capillaries continues• Oxygen and substrate delivery to the cells supplied by

these capillaries decreases

STAGES OF SHOCK

COMPENSATED SHOCK Vasoconstriction:– Due to a lack of oxygen - anaerobic

metabolism replaces aerobic metabolism• Production of lactate and hydrogen ions increases

(acid production)

STAGES OF SHOCK

COMPENSATED SHOCK Vasoconstriction:– Capillaries start to become “leaky” and

protein-containing fluid leaks into the interstitial spaces (leaky capillary syndrome)

STAGES IN SHOCK

COMPENSATED SHOCK Vasoconstriction:– AV shunts open (sphincters constrict),

particularly in the skin, muscle, GI tract• Causing less flow to the arterioles and less flow

through the capillaries– Sympathetic stimulation produces pale, sweaty

skin; rapid thready pulse; and elevated blood glucose levels

STAGES OF SHOCK

COMPENSATED SHOCK Vasoconstriction:– The release of epinephrine dilates coronary,

and cerebral arterioles and constricts other arterioles

• Blood is shunted to the heart, brain, and kidneys and capillary flow to skeletal muscle and other abdominal viscera decreases

Sympathetically mediated vasoconstriction

STAGES OF SHOCK

BLOOD PRESSURE IS MAINTAINED BY COMPENSATORY MECHANISMS– Blood stored in venous system is transferred into

arterial system by venous constriction– Increased cardiac contractions– Increased heart rate (variable)

STAGES OF SHOCK

COMPENSATED SHOCK:– If this stage of shock is not treated by prompt

restoration of circulatory volume, shock progresses to the next stage

HEMORRHAGIC SHOCK“One great consequence of blood loss is the intense vasoconstriction, the shrinkage of the capacity of the

vascular bed to accommodate the decreased blood volume...adjustments for blood loss take place...the entry of fluid into the blood vessels in a compensatory attempt.

The greatest extravascular store of readily available fluid in the body is...in the extracellular space. Dehydration and oligemia may make quite early demands not only on this

but also on the intracellular supply as well.”Beecher, Henry K, Simeone, Fiorindo, Mallory, Tracy B., et al: Recent Advances in Surgery I.

The Internal State of the Severely Wounded Man on Entry to the Most Forward Hospital. Surgery 22:672-711 Oct 1947

STAGES OF SHOCK DECOMPENSATED SHOCK

– MARKED INCREASE IN HEART RATE – PROLONGED CAPILLARY REFILL – BLOOD FLOW TO CRITICAL ORGANS DROPS

• Decreased urine output (decreased flow to kidneys)• Altered mental status (decreased flow to brain)

STAGES OF SHOCK DECOMPENSATED SHOCK - Capillary

and Venule Opening– As the shock state continues, the precapillary

sphincters relax, with some expansion of the vascular space

• Postcapillary sphincters resist local effects and remain closed, causing blood to pool or stagnate in the capillary system, producing capillary engorgement

Pre-Capillary Sphincters Relax Due to Shock Related Stimuli

STAGES OF SHOCK(please correct yours)

DECOMPENSATED SHOCK (Capillary and Venule Opening):– Arterial hypotension and closing of the AV shunts

results in more blood flow through capillary networks

• Contribute to stagnation of blood flow in the capillaries

STAGES OF SHOCK

DECOMPENSATED SHOCK (Capillary and Venule Opening):– As increasing hypoxemia and acidosis lead to

opening of additional venules and capillaries, the vascular space expands greatly

• Even a NORMAL blood volume may be inadequate to fill the container (this has implications for fluid resuscitation)

STAGES OF SHOCK

DECOMPENSATED SHOCK (Capillary and Venule Opening):– The capillary and venule capacity may become

great enough to reduce the volume of available blood for the great veins and vena cava

• Resulting in decreased venous return and a fall in cardiac output

STAGES OF SHOCK

DECOMPENSATED SHOCK (Capillary and Venule Opening):– The viscera (lung, liver, kidneys, and GI

mucosa) may become congested due to stagnant blood flow

STAGES OF SHOCK

DECOMPENSATED SHOCK (Capillary and Venule Opening):– The respiratory system attempts to compensate

for the acidosis by increasing ventilation to blow off carbon dioxide

• Increased respiratory rate• Producing a partially compensated metabolic

acidosis

STAGES OF SHOCK

DECOMPENSATED SHOCK (Capillary and Venule Opening):– Clotting mechanisms are also affected, leading

to hypercoagulability (DIC)– This stage of shock often progresses to

“irreversible” shock if fluid resuscitation is inadequate or delayed, or if the shock state is complicated by trauma or sepsis

STAGES OF SHOCKSTAGES OF SHOCK

“IRREVERSIBLE” SHOCK

2004 Johnston, MD

Question: What type of Shock would you expect in these victims?

STAGES OF SHOCK

“Irreversible” Shock– Occurs when the body is no longer able to

maintain systolic pressure– Both the systolic and diastolic pressure begin

to drop– Pulse pressure may be narrowed to such an

extent that it is not detectable with a blood pressure cuff

STAGES OF SHOCK Irreversible Shock

– Signs and symptoms• Bradycardia• Serious dysrhythmias• Frank hypotension• Evidence of multiple organ failure• Pale, cold, and clammy skin• Noticeably delayed capillary refill

– Cardiopulmonary collapse is usually imminent

Time (hr)Irreversible Shock. The loss of arterial pressure causes damage fromwhich ultimate recovery is not possible despite temp. restoration of BP

STAGES OF SHOCK

“Irreversible” Shock– As compensatory mechanisms fail

• Cerebral blood flow decreases– Marked alteration in mental status

• PO2 may drop

• PCO2 usually remains normal or low unless there is associated head or chest injury that leads to hypoventilation

STAGES OF SHOCK

“Irreversible” Shock– Myocardial strength may decrease from

ischemia secondary to:• A reduction of circulating RBCs• A lower oxygen saturation• Decreased coronary perfusion secondary to

hypotension (especially diastolic hypotension)

STAGES OF SHOCK “Irreversible” Shock-myocardial strength

decrease:– Necrosis of myocardium from same causes

associated with ischemia• Essentially simulating myocardial infarction

– Decreased preloading leading to decreased contractility

– Acidosis possibly leading to decreased contractility

CircumferentialSubendocardialInfarction dueto Shock

STAGES OF SHOCK

“Irreversible” Shock: Cardiac rhythm disturbances secondary to hypoxia (Impaired cardiac function)

STAGES OF SHOCK

“Irreversible” Shock– Manifested by the progression of

cellular ischemia and necrosis and by subsequent organ death despite restoration of oxygenation and perfusion

Complicationsof Shock

STAGES OF SHOCK “IRREVERSIBLE” SHOCK

– Disseminated Intravascular Coagulation (DIC)– Pulmonary capillaries become permeable,

leading to pulmonary edema• Decreases the absorption of oxygen and results in

possible alterations in carbon dioxide elimination• May lead to acute respiratory failure or adult

respiratory distress syndrome (ARDS)

ShockLung

Congestive atelectasis and diffuse alveolar damage due to shock (ARDS)

Acute passive congestion of the lung due to shock

Congested Lung Due to Shock

STAGES OF SHOCK

“IRREVERSIBLE” SHOCK Multiple Organ Failure

– The amount of cellular necrosis required to produce organ failure varies with each organ as well as the underlying condition of the organ

STAGES OF SHOCK

“IRREVERSIBLE” SHOCK Multiple Organ Failure:

– In this stage, blood pressure falls dramatically– Cells can no longer use oxygen, and

metabolism stops

STAGES OF SHOCK

“IRREVERSIBLE” SHOCK Multiple Organ Failure:

– Usually hepatic failure occurs, followed by renal failure, and then heart failure

• If capillary occlusion persists for more than 1-2 hours, the cells nourished by that capillary undergo changes that rapidly become irreversible

Acute congestion of liver due to shock

Acute centrilobular hemorrhage due to Shock

Acute cortical necrosis of the kidney due to shock

Acute tubular necrosis of the kidney due to shock

STAGES OF SHOCK

“IRREVERSIBLE” SHOCK Multiple Organ Failure:

– GI bleeding and sepsis may result from GI mucosal necrosis

– Pancreatic necrosis may lead to further clotting disorders and severe pancreatitis

Intestinal mucosal hemorrhages due to shock

Adrenal gland hemorrhage due to shock

STAGES OF SHOCK

Variations in Physiological Responses to Shock– Age and relative health

• General physical condition• Preexisting diseases

2004 Johnston, MD

A few of the patients [in shock] even presented a raised systolic blood pressure, while of those with a blood pressure of under 100 mm. Hg., some had rapid pulses, others only slightly more rapid than normal. A few, and these generally patients over fifty years, showed a pulse rate under seventy. In younger people the blood pressure was better maintained but the pulse rate tended to be faster.”

Surgery Chapter 3 “Shock and Resuscitation” by Sir Zachary Cope, Edited by Sir Zachary Cope, London, Her Majesty’s Stationary Office, 1953, p. 78-88

HEMORRHAGIC SHOCK

STAGES OF SHOCK Variations in Physiological Responses to

Shock– Ability to activate compensatory mechanisms

• Older adults are less able to compensate (develop hypotension early)

• Children compensate longer and deteriorate faster

• Medications may interfere with compensatory mechanisms

SHOCK IS A MOMENTARY

PAUSE IN THE ACT OF DYING

HEMORRHAGIC HEMORRHAGIC SHOCKSHOCK

“When much blood is lost, the pulse becomes feeble, the skin

extremely pale, the body covered with a malodorous

sweat, the extremities frigid, and death occurs speedily”

Aulus Conelius Celsus, First Century Roman Savant

HEMORRHAGIC SHOCK

“...the greatest loss of hemoglobin occurs in wounds that involve compound fractures of the long bones or traumatic amputation..it is

the wounds that are associated with great hemorrhage that cause the severe shock.”

Beecher, Henry K, Simeone, Fiorindo, Mallory, Tracy B., et al: Recent Advances in Surgery I. The Internal State of the Severely Wounded Man on Entry to the

Most Forward Hospital. Surgery 22:672-711 Oct 1947

2004 Johnston, MD

Shock and Trauma

HEMORRHAGIC SHOCK A word on autoregulation

– The body sacrifices less vital organ tissue to maintain oxygen and nutrient flow to the brain and heart

– Vital organs are also protected by local factors that provide these organs with the ability to autoregulate blood flow

– In the brain and heart, blood flow and oxygen delivery remain constant over a wide range of arterial pressures

2004 Johnston, MD

Clinical Classes of Shock

Class I hemorrhage (loss of 0-15%)– In the absence of complications, only

minimal tachycardia is seen.– Usually, no changes in BP, pulse

pressure, or respiratory rate occur.– A delay in capillary refill of longer than 3

seconds corresponds to a volume loss of approximately 10%.

2004 Johnston, MD

Class II hemorrhage (loss of 15-30%)– Clinical symptoms include tachycardia (rate >100

beats per minute), tachypnea, decrease in pulse pressure, cool clammy skin, delayed capillary refill, and slight anxiety.

– The decrease in pulse pressure is a result of increased catecholamine levels, which causes an increase in peripheral vascular resistance and a subsequent increase in the diastolic BP.

2004 Johnston, MD

Class III hemorrhage (loss of 30-40%)– patients usually have marked tachypnea and

tachycardia, decreased systolic BP, oliguria, and significant changes in mental status, such as confusion or agitation.

– In patients without other injuries or fluid losses, 30-40% is the smallest amount of blood loss that consistently causes a decrease in systolic BP.

– Most of these patients require blood transfusions, but the decision to administer blood should be based on the initial response to fluids.

2004 Johnston, MD

Class IV hemorrhage (loss of >40%)– Symptoms include the following: marked

tachycardia, decreased systolic BP, narrowed pulse pressure (or immeasurable diastolic pressure), markedly decreased (or no) urinary output, depressed mental status (or loss of consciousness), and cold and pale skin.

– This amount of hemorrhage is immediately life threatening.

2004 Johnston, MD

Clinical Classification of Shock

HEMORRHAGIC SHOCK“Possibly, too much attention has been given to the fact

that on many occasions [patients in shock may have a normal blood pressure]. ...[T]his has led to a tendency

to dismiss the blood pressure as a helpful sign even when it is low - a fatal error, on some occasions. More

helpful than the level of the blood pressure, is the direction of its swing - a falling blood pressure, a

rising pulse rate, are in most cases an urgent indication of the need for blood.”

Beecher, LTC Henry K: “Annals of Surgery” Vol 121, No. 6, June 1945. p769-792

HEMORRHAGIC SHOCK

Reminder: Critical Signs / Symptoms of Shock – pulse is usually rapid and weak– appearance of the wound, extent of blood-soaked

clothing, a history of delay in hospital admission, of exposure, of exhaustion - all important considerations when in the field

HEMORRHAGIC SHOCK

Critical Signs / Symptoms of Shock (cont.)– Research into “thirst”– Most important of all is the trend of the pulse and the

trend of the blood pressure• A rising pulse rate and a falling blood pressure nearly always

forecast immediate trouble, especially if associated with a cool skin

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Patient Evaluation

In a patient with possible shock secondary to hypovolemia, the history is vital in determining the possible causes and in directing the workup.

Symptoms of shock, such as weakness, lightheadedness, and confusion, should be assessed in all patients.

In the patient with trauma, determine the mechanism of injury and any information that may heighten suspicion of certain injuries

2004 Johnston, MD

In patients with GI bleeding, inquire about hematemesis, melena, drinking history, excessive nonsteroidal anti-inflammatory drug use, and coagulopathies

The chronology of vomiting and hematemesis should be determined.

If a gynecologic cause is being considered, gather information about the following: last menstrual period, risk factors for ectopic pregnancy, vaginal bleeding (including amount and duration), vaginal passage of products of conception, and pain.

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HEMORRHAGIC SHOCKTESTS FOR SHOCK

BLOOD PRESSURE PULSE PRESSURE PULSE RATE RESPIRATORY RATE CAPILLARY REFILL GEN. APPEARANCE & BEHAVIOR

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If conscious, the patient may be able to indicate the location of pain.

Vital signs, prior to arrival in the ED, should also be noted.

Chest, abdominal, or back pain may indicate a vascular disorder.

The classic sign of a thoracic aneurysm is a tearing pain radiating to the back. Abdominal aortic aneurysms usually result in abdominal or back pain.

HEMORRHAGIC SHOCK The usual mental lethargy associated with shock

may be replaced by remarkable mental acuity and activity which may easily deceive an observer into thinking that shock is not present

The very nature of shock dictates how difficult or impossible it is to find a pathognomonic sign/symptom or finding which is invariably associated with the presence of shock.

HEMORRHAGIC SHOCK

REMEMBER: Blood pressure and heart rate are unreliable indicators of rapid deterioration in young trauma

patients

HEMORRHAGIC SHOCK

RELATIVE (paradoxical) BRADYCARDIA– May be indicative of a profound blood loss– Penetrating abdominal injuries– Ectopic pregnancy– May also occur in extremity trauma

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Don’t Forget!

In the patient with trauma, hemorrhage usually is the presumed cause of shock.

However, it must be distinguished from other causes of shock. These include:

cardiac tamponade (muffled heart tones, distended neck veins), tension pneumothorax (deviated trachea, unilaterally decreased breath sounds), and spinal cord injury (warm skin, lack of expected tachycardia, neurological deficits).

2004 Johnston, MD

Remember, hemorrhage can occur through internal losses: chest, abdomen, thighs.

The chest should be auscultated for decreased breath sounds, because life-threatening hemorrhage can occur from myocardial, vessel, or lung laceration.

The abdomen should be examined for tenderness or distension, which may indicate intraabdominal injury.– The thighs should be checked for deformities or

enlargement (signs of femoral fracture and bleeding into the thigh).

2004 Johnston, MD

The patient's entire body should then be checked for other external bleeding.

In the patient without trauma, the majority of the hemorrhage is in the abdomen

2004 Johnston, MD

Pregnancy-related disorders include ruptured ectopic pregnancy, placenta previa, and abruption of the placenta. Hypovolemic shock secondary to an ectopic pregnancy is common.

Hypovolemic shock secondary to an ectopic pregnancy in a patient with a negative urine pregnancy test is rare but has been reported.

2004 Johnston, MD

“The upper limit of normal for adult women should be changed to 2.9 seconds, and the upper limit of normal for the elderly should be changed to 4.5 seconds....The temperature dependence of capillary refill raises questions regarding its reliability in the pre-hospital setting.”

Schriger, DL and Baraff, L: Defining Normal Capillary Refill: Variation with Age, Sex, and Temperature” Annals of Emerg Med 17:932-35

CAPILLARY REFILL TEST

CAPILLARY REFILL TEST“Given current “normal values” and the variables of

environmental temperature, age, sex and questions regarding the interpretation [which is affected by

such things as lighting], one is left with the impression that at present capillary refill testing

may be unreliable.”

Knopp, RK “Capillary Refill: New Concerns About an Old Bedside Test”, Editorial Annals of Emerg Med 17:990-1

2004 Johnston, MD

Final Question

22 yr old Special Forces jumper has canopy collapse 40 feet above drop zone and presents to your BAS with open facial fractures with blood and teeth in oropharynx. He is conscious, has obvious bilateral ankle fractures and an open angulated fracture of the left femur. The combat medic tells you his last vitals 5 minutes before arriving to the BAS were 110/80, pulse 130, and respirations 36.

2004 Johnston, MD

What should you do first? What should you do second? Are you concerned about shock? Why?

Thanks for participating!

2004 Johnston, MD

And Remember, Keep your Compensatory mechanisms always ready by escaping the sofa!

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