lesson 6

Lesson 6
Shock


Objectives
 As a result of active participation in this lesson you should be able to
 Explain the pathophysiology of shock to include the role of shock in immediate and delayed trauma morbidity and mortality
 Relate mechanism of injury and assessment findings to identify patients in shock and patients with the potential to develop shock
 Describe the assessment and management
of the patient in shock or with the potential
for shock, including the limitations of
prehospital care


Scenario
It is just past noon on a Sunday. It is sunny and 64° Fahrenheit (18° Celsius). As you get out of your vehicle in a shopping center parking lot you hear a loud “boom.” Turning toward the sound, you see an airborne motorcyclist land in front of the stopped car he has just rear-ended.


Scenario
It appears that the car was stopped to turn into the parking lot when the motorcycle hit it from behind at about 45 miles (72 kilometers) per hour. The rider was ejected from the motorcycle and landed
in front of the stopped vehicle.


Scenario: Scene Size-Up
 What are the considerations for scene safety?
 What are the potential injuries associated with this mechanism?



Scenario
Noting that another bystander is calling 911, you jog the short distance to the scene, where the patient is lying on his back. You note that he is wearing a helmet. Although the day is mild and he is wearing a leather jacket, the patient is shivering uncontrollably.



Scenario: Primary Survey
 Is there evidence of shock?


Scenario: Primary Survey
 Awake, agitated, slow to process questions
 Shivering, pale
 Breathing is slightly faster than normal
 Skin is cool; radial pulse is over 100


Scenario: Critical Thinking
 What do these findings suggest?
 Is the patient in shock?


Scenario: Critical Thinking
 What is happening to this patient?


Shock
A state of generalized cellular hypoperfusion leading to inadequate cellular oxygenation to meet metabolic needs


Hypoperfusion
 The patient is losing blood volume
 Loss of circulating volume means fewer RBCs circulating through the capillary beds to deliver oxygen to the cells
 Lack of oxygen impairs metabolism
Every RBC counts!


Metabolism
 All cells require energy to function
 Aerobic metabolism
 Oxygen is required for efficient production of the energy molecule ATP and converting pyruvate to carbon dioxide and water through the Kreb’s cycle
 Anaerobic metabolism
 Inadequate oxygen results in decreased ATP (energy molecule) production and accumulation
of lactic acid


Consequences
 Decreased ATP (energy) for cell membrane function
 Potassium and lactic acid enter the blood
• Low pH results in release of cellular enzymes that autodigest cells
• Cellular death, organ failure result
 Sodium and water enter the cell
• Cellular edema
• Further loss of intravascular (blood) volume


Scenario: Critical Thinking
 What is happening to this patient?
 The use of ATP (energy) produces heat
 With inadequate ATP (energy), the patient is not producing heat
 Even with relatively mild temperatures, the patient is losing heat to the environment and cannot balance heat loss with heat production
 He is using what little ATP (energy) he is producing
to shiver and is producing lactic acid through anaerobic metabolism
 Hypothermia impairs blood clotting


Scenario: Critical Thinking
 What is happening to this patient?
 He is entering a downward spiral
 He needs your help
 What can you do for this patient before additional help arrives?



Shock
 Classifications
 Hypovolemic
• Hypovolemic shock due to hemorrhage is the most common cause of shock in the
trauma patient
• Assume hemorrhagic shock until proven otherwise
 Distributive
 Cardiogenic



Pathophysiology of
Hemorrhagic Shock
 Shock is progressive
 Compensatory mechanisms are short-term
 Events in hypovolemic shock
 Hemodynamic changes
 Cellular (metabolic) changes
 Microvascular changes


Pathophysiology of Shock
 Hemodynamics
 Perfusion of the body tissues requires
• An effective pump
• An adequate volume of blood
• Vascular resistance


Pathophysiology of Shock
 The heart must be an effective pump

CO = SV × HR

 Stroke volume depends on adequate return of blood to the heart
 If blood volume decreases, cardiac output will decrease unless the body alters the heart rate
Pathophysiology of Shock
 Adequate blood pressure is required for perfusion
 Cardiac output is one factor in maintaining blood pressure

BP = CO × SVR

 Vasoconstriction occurs to increase systemic vascular resistance if cardiac output falls
Pathophysiology of Shock
 Microvascular changes
 Early: precapillary and postcapillary sphincters constrict causing ischemia
 As acidosis increases: precapillary sphincters relax but postcapillary sphincters remain constricted causing stagnation
 Finally: postcapillary sphincters relax causing washout, releasing microemboli and aggravating acidosis


Pathophysiology of Shock
Pathophysiology of Shock
 Vasoconstriction
 Ischemic phase of shock
 Ischemic sensitivity
 Brain: 4 to 6 minutes
• Altered LOC occurs early
 Organs: 45 to 90 minutes
• Acute renal failure, ARDS
 Skin and skeletal muscle: hours


Classifications of Shock
 Distributive shock
 Neurogenic—decreased systemic vascular resistance
 Cardiogenic shock (in the trauma patient)
 Intrinsic
• Blunt cardiac trauma leading to muscle damage and/or dysrhythmia
• Valvular disruption
 Extrinsic
• Pericardial tamponade
• Tension pneumothorax



Scenario
 How does the pathophysiology of shock explain the patient’s presentation?



Signs of Shock
 Tachypnea
 Hypoxia and acidosis stimulate the respiratory center
 20 to 30 breaths per minute
 More than 30 breaths per minute
 Intolerance of oxygen face mask


Signs of Shock
 Circulation
 Assessment for hemorrhage
 Level of consciousness
 Heart rate
 Pulse
 Skin color and temperature
 Capillary refill
 Blood pressure



Signs of Shock
 Disability
 Decreased cerebral perfusion results in altered LOC
 Other causes of altered LOC will not kill the patient as rapidly as shock
 Assume altered LOC is due to shock and treat


Signs of Shock
 Musculoskeletal injuries
 Major or multiple fractures can lead to significant blood loss
 Of particular concern are femur and pelvic fractures
 Don’t underestimate blood loss due to multiple fractures excluding the femurs
and pelvis



Signs of Shock



Signs of Shock
 Internal organ injury
 Shock is assumed to be hypovolemic in the absence of other explanations
 Abdominal trauma is a cause of significant hidden hemorrhage
 Assume abdominal trauma if hypovolemic shock is not otherwise explainable



Scenario: Secondary Survey
 A BLS engine has arrived
 Findings
 HR 124
 RR 28
 BP 124/86
 Deformities
• Bilateral femurs
• Right humerus



Classifications of Hemorrhage



Scenario: Critical Thinking
 What class of hemorrhage do you suspect this patient is experiencing?
 How do you know?
 What is the likely source of the patient’s hemorrhage?


Assessment: Critical Thinking
 What factors may affect a patient’s presentation in shock?
 Pregnancy
 Medications
 Age
 Preexisting medical conditions
Shock Management
 Four questions guide resuscitation
 What is the cause of shock in this patient?
 What is the care of this type of shock?
 Where can the patient get this care?
 What can be done between now and the time the patient reaches definitive care?


Shock Management
 Reduced cardiac output and impaired tissue oxygenation are occurring before the blood pressure drops.
 Proper shock management improves the oxygenation of RBCs and improves the delivery of RBCs to the tissues.
 Airway
 Ventilation
 Oxygenation
 Circulation



Scenario: Airway
 What are the patient’s airway needs?



Scenario: Oxygenation
 What guides the
administration of
oxygenation for this
patient?



Scenario: Breathing
 Does the patient require assisted ventilations?



Scenario: Circulation
 What can be done to improve the patient’s circulation?



Hemorrhage Control
 Hemorrhage control is critical to perfusion
 Techniques
 Direct pressure will control most external hemorrhage
 Tourniquet
 Immobilization
 Consider elevation
 Consider use of arterial pressure points
 Topical hemostatic agents may be recommended for prolonged transport
situations



Circulation: Fluid Therapy
 Why fluid therapy?
 Controversies and disadvantages
 Areas of investigation



Circulation: Fluid Therapy
 Current recommended practice
 Classes II, III, and IV shock
 Initial rapid bolus of 1000 to 2000 mL of warmed lactated Ringer’s solution
 Pediatric patients: 20 mL/kg
 Maintain systolic BP at 85 to 90 mm Hg



Circulation: Patient Positioning
 Supine
 Not Trendelenburg
 No need to elevate lower extremities



Circulation: PASG
 Indications
 Contraindications
 Not effective for control of external hemorrhage



Transport Considerations
 Transport without delay does not mean “scoop and run”
 Patient compartment temperature should be 85° F (29° C)
 Considerations in prolonged transport



Complications of Shock
 Untreated, shock progresses
 Prehospital care can make a difference in the patient’s eventual outcome
 Acute renal failure
 Acute respiratory distress syndrome
 Hematologic failure
 Multiple organ dysfunction syndrome



Minimizing Complications
 Assess for shock
 Assume hemorrhagic shock until proven otherwise
 Remember: cardiac output and tissue oxygenation are impaired early
 Restore/maintain: airway, ventilation, oxygenation, circulation
 Hypothermia creates a cycle of worsening shock and hypothermia
 Transport without delay



Scenario: On-going Assessment
 En route to the ED, paramedics have started an IV on the patient. His blood pressure increased with a bolus of fluid, but decreased shortly after receiving the bolus.
 What does this tell you about the patient’s condition?



On-going Assessment
 There are three responses to fluid therapy:
 Rapid response
 Transient response
 Minimal or no response



Scenario: Outcome
 ED evaluation
 Orthopedic trauma
 Nonoperative injuries to kidney and spleen
 Orthopedic surgery
 Uncomplicated recovery



Summary
 Shock is a state of cellular hypoperfusion leading to inadequate energy production to meet metabolic needs
 The most common cause of shock in the trauma patient is hemorrhage
 Shock is hemorrhagic until proven otherwise



Summary
 The management of shock is aimed at improving oxygenation of RBCs and improving delivery of RBCs to the microcirculation
 How do we do this?



QUESTIONS?