What is Shock? Its epidemiology, clinical presentation, evaluation and management

Outline:

1. Definition
2. Epidemiology
3. Physiology
4. Classes of Shock
5. Clinical Presentation
6. Management
7. Controversies

Definition;
A physiologic state characterized by Inadequate tissue perfusion, Clinically manifested by

• Hemodynamic disturbances
• Organ dysfunction
  

Epidemiology:

• Mortality
• Septic shock – 35-40% (1 month mortality)
• Cardiogenic shock – 60-90%
• Hypovolemic shock – variable/mechanism
  

Pathophysiology:

• Imbalance in oxygen supply and demand
• Conversion from aerobic to anaerobic metabolism
• Appropriate and inappropriate metabolic and physiologic responses

Cellular physiology:

• Cell membrane ion pump dysfunction
• Leakage of intracellular contents into the extracellular space
• Intracellular pH dysregulation
  

Resultant systemic physiology;

• Cell death and end organ dysfunction
• MSOF and death
  

Characterized by three stages:

1. Preshock (warm shock, compensated shock)
2. Shock
3. End organ dysfunction
   

Compensated shock:

• Low preload shock – tachycardia, vasoconstriction, mildly decreased BP
• Low afterload (distributive) shock – peripheral vasodilation, hyperdynamic state
  

Shock:

• Initial signs of end organ dysfunction
• Tachycardia
• Tachypnea
• Metabolic acidosis
• Oliguria
• Cool and clammy skin
  

End Organ Dysfunction:

• Progressive irreversible dysfunction
• Oliguria or anuria
• Progressive acidosis and decreased CO
• Agitation, obtundation, and coma
• Patient death
  

Classification of Shock:
Major classes of shock

1. Hypovolemic
2. Cardiogenic
3. Distributive

Hypovolemic Shock:

• Results from decreased preload

Etiologic classes:
Hemorrhage - e.g. trauma, GI bleed, ruptured aneurysm
Fluid loss - e.g. diarrhea, vomiting, burns, third spacing, iatrogenic
Hemorrhagic Shock

Cardiogenic Shock:

• Results from pump failure
• Decreased systolic function
• Resultant decreased cardiac output
  

Etiologic categories
Myopathic
Arrhythmic
Mechanical
Extracardiac (obstructive)

Distributive Shock;

• Results from a severe decrease in SVR
• Vasodilation reduces afterload
• May be associated with increased CO
  

Etiologic categories:
Sepsis
Neurogenic / spinal

Other causes
Systemic inflammation – pancreatitis, burns
Toxic shock syndrome
Anaphylaxis and anaphylactoid reactions
Toxin reactions – drugs, transfusions
Addisonian crisis
Myxedema coma

Septic Shock;

Clinical Presentation
Clinical presentation varies with type and cause, but there are features in common

• Hypotension
• Cool, clammy skin (exceptions – early distributive, terminal shock)
• Oliguria
• Change in mental status
• Metabolic acidosis
  

Evaluation

• Done in parallel with treatment!
• H&P – helpful to distinguish type of shock
• Full laboratory evaluation (including H&H, cardiac enzymes, ABG)
• Basic studies – CxR, EKG, UA
• Basic monitoring – VS, UOP, CVP, A-line
• Imaging if appropriate – FAST, CT
• Echo vs. PA catheterization
• CO, PAS/PAD/PAW, SVR, SvO2
  

Treatment:

• Manage the emergency
• Determine the underlying cause
• Definitive management or support
  

Manage the Emergency
Your patient is in extremis – tachycardic, hypotensive, obtunded
How long do you have to manage this?
Suggests that many things must be done at once
Draw in ancillary staff for support!
What must be done?
One person runs the code!
Control airway and breathing
Maximize oxygen delivery
Place lines, tubes, and monitors
Get and run IVF on a pressure bag
Get and run blood (if appropriate)
Get and hang pressors
Call your senior/fellow/attending

Determine the Cause
Often obvious based on history
Trauma most often hypovolemic (hemorrhagic)
Postoperative most often hypovolemic (hemorrhagic or third spacing)
Debilitated hospitalized pts most often septic
Must evaluate all pts for risk factors for MI and consider cardiogenic
Consider distributive (spinal) shock in trauma
What if you’re wrong?

Definitive Management
Hypovolemic – Fluid resuscitate (blood or crystalloid) and control ongoing loss
Cardiogenic - Restore blood pressure (chemical and mechanical) and prevent ongoing cardiac death
Distributive – Fluid resuscitate, pressors for maintenance, immediate abx/surgical control for infection, steroids for adrenocortical insufficiency