Shock

Question 1

What is the most common cause of shock in trauma patients?

Answer 1

Hemorrhage

Question 2

What is the equation for cardiac output?

Answer 2

CO = HR x SV

• SV consists of preload, contractility, and afterload
• cardiac output is the volume of blood pumped by the heart per minute

Question 3

What is the definition of preload?

-what are the determinants of preload? (3)

Answer 3

Preload = volume of venous blood returning to the left and right sides of the heart

• Preload is determined by:
  1. Venous capacitance (how much blood can sit in the veins ie. reservoir)
  2. Volume status
  3. Difference between mean venous systemic pressure and right atrial pressure

Question 4

How does decreased blood volume deplete preload?

Answer 4

Decreased blood volume = decreased venous volume –> decreased venous pressure compared to right atrial pressure –> decreased venous return to the heart –> decreased myocardial muscle fiber length after ventricular filling at the end of diastole –> decreased myocardial contractility

Question 5

What is the definition of afterload?

Answer 5

Resistance to the forward flow of blood (ie. peripheral vascular resistance)

Question 6

What is the physiological response to blood loss?

Answer 6

Compensatory mechanisms:

1. Peripheral vasoconstriction to redirect blood flow to kidneys/heart/brain
2. Increase in heart rate to preserve cardiac output in order to compensate from decreased stroke volume (decreased preload and decreased contractility)
3. Increased catecholamines increase peripheral vascular resistance which in turn increases diastolic blood pressure and reduces pulse pressure
4. Inadequately perfused and poorly oxygenated cells will switch to anaerobic metabolism, resulting in the formation of lactic acid and development of metabolic acidosis

Question 7

What is the most effective method of stopping hemorrhagic shock?

Answer 7

STOP THE BLEEDING!!!!
-need definitive control of hemorrhage and restoration of adequate circulating volume - these are the goals of treating hemorrhagic shock

Question 8

True or false: The presence of shock in a trauma patient warrants the immediate involvement of a surgeon.

Answer 8

True! Strongly consider early transfer of these patients to a trauma center

Question 9

How much blood volume can be lost before you see a fall in systolic blood pressure?

Answer 9

Up to 30%! Compensatory mechanisms can delay hypotension so do NOT rely solely on systolic blood pressure as an indicator of shock

Question 10

What are the 2 most early physical exam signs of hemorrhagic shock?

Answer 10

1. Tachycardia

2. Cutaneous vasoconstriction (cold extremities)

Question 11

Name two reasons why elderly patients may not exhibit tachycardia in shock?

Answer 11

1. Limited cardiac response to catecholamines

2. May be on beta blockers/other medications that decrease heart rate

Question 12

What are the two main classifications of shock in a trauma patient?

Answer 12

Hemorrhagic vs. non-hemorrhagic shock

Question 13

What are possible causes of non-hemorrhagic shock in a trauma patient?

Answer 13

. Cardiac tamponade

2. Blunt myocardial injury
3. Tension pneumothorax
4. Spinal cord injury

• **Obstructive shock = cardiac tamponade and tension pneumothorax
• Cardiogenic shock = blunt myocardial injury
• Neurogenic shock = spinal cord injury (loss of sympathetic tone leading to hypotension)
• Septic shock = think of this in trauma patients with delayed presentation

***Suspect cardiac tamponade/tension pneumothorax/blunt myocardial injury in any patient with injuries above the diaphragm

Question 14

What are the main sources of potential massive blood loss?

Answer 14

1. Chest
2. Abdomen
3. Retroperitoneum
4. Long bones
5. External bleeding
6. Pelvis

Question 15

What is the most common cause of cardiac tamponade in trauma patients?

Answer 15

Penetrating thoracic trauma - can also occur in blunt trauma but less likely

Question 16

What are the clinical signs of cardiac tamponade?

Answer 16

1. Hypotension
2. Muffled heart sounds
3. Distended neck veins
4. Minimal response to fluids
5. Tachycardia

Question 17

What are the clinical signs of tension pneumothorax?

Answer 17

1. Acute respiratory distress
2. Subcutaneous emphysema
3. Absent unilateral breath sounds
4. Hyperresonance to percussion
5. Distended neck veins
6. Hypotension
7. Tracheal shift

Question 18

True or false: Isolated intracranial injuries do not cause shock unless the brainstem is injured.

Answer 18

True!

Question 19

What is the classic presentation of neurogenic shock?

Answer 19

Hypotension without tachycardia or cutaneous vasoconstriction

Question 20

What is the normal adult blood volume?

-what about a child?

Answer 20

Adults: Approximately 7% of body weight (70 ml/kg)
-for example, a 70 kg person has approximately 5 L of blood volume

Child: Approximately 80 ml/kg

Question 21

What are the 4 classes of hemorrhage?

-how do you determine subsequent volume replacement?

Answer 21

Class 1: < 15% blood loss, equal to donating 1 unit of blood
Class 2: 15-30% blood loss, uncomplicated hemorrhage for which crystalloid fluid resuscitation is required
Class 3: 31-40% blood loss, complicated hemorrhagic state in which at least crystalloid infusion is required and perhaps also a blood replacement
Class 4: >40% blood loss, unless aggresive measures are taken, the patient will die within minutes. Blood transfusion is required!

Subsequent volume replacement is determined by the patient’s response to therapy

Question 22

What are the clinical symptoms of class I hemorrhage?
-management?

Answer 22

-Class 1: < 15% of blood loss
Minimal - minimal tachycardia occurs, no changes in blood pressure, pulse pressure or respiratory status.
-management: for otherwise healthy patients, this amount of blood loss does not require replacement since compensatory mechanisms will restore blood volume within 24 hours usually without need for blood transfusion

Question 23

What are the clinical symptoms of class 2 hemorrhage?
-management?

Answer 23

Class 2: 15-30% of blood volume loss

• Symptoms:
  1. Tachypnea
  2. Tachycardia
  3. DECREASED pulse pressure: you have increased diastolic blood pressure because of increased catecholamine release causing vasoconstriction but your systolic blood pressure is usually maintained
  4. Mild CNS changes: anxiety, fear, hostility
• U/O is usually preserved

Management: Usually these patients only need crystalloid therapy and respond well. Minority may require blood transfusion eventually

Question 24

What are the clinical symptoms of class 3 hemorrhage?
-management?

Answer 24

Class 3: 31-40% blood volume loss
Symptoms:
1. Marked tachycardia
2. Tachypnea
3. Decreased mental status
4. Hypotension: 30% of blood loss is the minimum at which decreased systolic blood pressure will occur
5. Decreased urine output

Management:

1. Stop the hemorrhage by emergency operation or embolization
2. Will need packed red blood cells and blood products to reverse the shock state

Question 25

``` What are the clinical symptoms of class 4 hemorrhage? -management? ```

Answer 25

``` Class 4: >40% of blood volume loss Symptoms: 1. Significantly marked tachycardia 2. Tachypnea 3. Profoundly depressed mental status 4. Hypotension and very narrow pulse pressure (since diastolic BP is increased by catecholamines but systolic BP is decreased due to blood loss) 5. No urine output ``` Management: 1. Rapid transfusion 2. Immediate surgical intervention **If this does not occur, patient will die

Question 26

What are possible confounding factors for the hemorrhage classification system?

Answer 26

1. Patient age 2. Patient medications that may alter response to hemorrhage 3. Prehospital fluid management 4. Time lapse between injury and initiation of treatment 5. Severity of injury, particularly type and anatomic location of injury

Question 27

What are two ways that major soft tissue injuries/fractures can compromise a patient's hemodynamic status? - considerations in obese patients - considerations in elderly patients

Answer 27

1. Direct blood loss into the site of injury: - tibia and humerus fractures can result in loss up to 750 ml of blood - femur fractures can result in loss up to 1500 ml of blood - obese patients: can lose significant amount of blood into soft tissues even in the absence of fractures - elderly: fragile skin, fragile subcutaneous tissues that bleed more easily, inelastic blood vessels that do not spasm to stop bleeding, blood vessels don't thrombose as easily when injured or transected 2. Secondary edema due to activation of systemic inflammatory response locally with release of cytokines. These result in increased permeability of vascular endothelium and you have fluid leaking out of intravascular space to extravascular space as a result of the altered endothelial permeability

Question 28

In a patient presenting with shock in trauma setting, what is the first type and amount of fluid you should give them?

Answer 28

Adults: 1 L of normal saline Kids: 20 ml/kg of normal saline ***This includes any amount already given in the prehospital setting

Question 29

Why is administering excessive crystalloid solution harmful in trauma patients?

Answer 29

By giving too much crystalloid solution before the hemorrhage has been definitively controlled, you are increasing the patient's blood pressure which can worsen bleeding. -in adults, this is why you have permission hypotension (aka controlled resuscitation, balanced resuscitation): you want to balance organ perfusion/tissue oxygenation with the avoidance of rebleeding by accepting a lower than normal blood pressure

Question 30

Early resuscitation with blood and blood products must be considered in patients with which classes of hemorrhage?

Answer 30

Class 3 and 4!

Question 31

What are the 3 categories of responses to initial fluid resuscitation and how do you define them?

Answer 31

1. Rapid response to initial fluid resuscitation (rapid responders) - vital signs return to normal with 1st fluid bolus and you get adequate tissue perfusion and oxygenation - estimated blood loss < 15% (class 1 hemorrhage) - need for blood: low - need for operative intervention: possibly - once this occurs, can slow the fluids to maintenance rates 2. Transient response to initial fluid resuscitation (transient responders) - vital signs initially improve but then have recurrence of decreased blood pressure or increased heart rate - these people respond to the initial fluid bolus but then get worse due to ongoing blood loss or inadequate resuscitation - estimated blood loss: 15-40% (class 2-3) - need for blood: moderate to high - need for operative intervention: likely - no further fluid bolus or immediate blood transfusion is indicated - for these patients, blood transfusion is indicated as opposed to continuing to give fluid boluses which may worsen bleeding! - even more important is recognizing that these patients require operative or angiographic control of hemorrhage - transient response to blood administration identifies patients who are still bleeding and require rapid surgical intervention - consider initiating a massive transfusion protocol 3. Minimal or no response to initial fluid resuscitation (non responders) - no vital sign changes at all to initial fluid bolus, remains abnormal - estimated blood loss: > 40% - need for blood: immediately!!! - need for operative intervention: highly likely - initiate massive transfusion protocol

Question 32

What is a useful determinant of adequate resuscitation beside vital signs?

Answer 32

Urine output! Inability to obtain urinary output suggests inadequate resuscitation

Question 33

How do you decide whether to initiate a blood transfusion in a trauma patient?

Answer 33

Initiate blood transfusion based on initial response to fluids: are they rapid, transient or non-responders? -transient or non-responders will need blood transfusion (including pRBCs, plasma, platelets)

Question 34

What temperature should fluid/blood be heated to in order to avoid hypothermia?

Answer 34

39 degrees celcius

Question 35

What is the definition of massive transfusion?

Answer 35

> 10 units of pRBC in first 24 hours of admission OR > 4 units pRBCs in first hour

Question 36

What is the optimal timing for administration of TXA in a trauma patient?

Answer 36

Within 3 hours of injury | -first dose usually given over 10 minutes and then follow up dose of 1 gram is given over 8 hours

Question 37

What is the equation for blood pressure?

Answer 37

BP = Cardiac output x Peripheral vascular resistance

Question 38

What are special considerations for shock in the elderly population?

Answer 38

1. Decreased cardiac response to catecholamines due to decreased receptor response 2. Decreased cardiac compliance/myocardial contraction 3. Unable to increase heart rate to compensate for decreased cardiac output 4. Atherosclerotic vascular occlusive disease can make vital organs very sensitive to even mild reductions in blood flow 5. May already be malnourished/dehydrated at baseline or be on meds that impact cardiovascular response to shock 6. Lung disease, renal disease can worsen impact of shock

Question 39

What is the lethal triad in trauma?

Answer 39

1. Hypothermia 2. Coagulopathy 3. Acidosis