SHOCK

Outline

Definition Epidemiology Physiology Classes of Shock Clinical Presentation Management 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

Pathophysiology

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

Physiology

Characterized by three stages Preshock (warm shock, compensated shock) Shock End organ dysfunction

Physiology

Compensated shock Low preload shock – tachycardia,

vasoconstriction, mildly decreased BP Low afterload (distributive) shock – peripheral

vasodilation, hyperdynamic state

Pathophysiology

Shock Initial signs of end organ dysfunction

Tachycardia Tachypnea Metabolic acidosis Oliguria Cool and clammy skin

Physiology

End Organ Dysfunction Progressive irreversible dysfunction

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

Classification

Schemes are designed to simplify complex physiology

Major classes of shock Hypovolemic Cardiogenic 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

Hypovolemic Shock

Hemorrhagic Shock

Parameter I II III IV

Blood loss (ml) <750 750–1500 1500–2000 >2000

Blood loss (%) <15% 15–30% 30–40% >40%

Pulse rate (beats/min) <100 >100 >120 >140

Blood pressure Normal Decreased Decreased Decreased

Respiratory rate (bpm) 14–20 20–30 30–40 >35

Urine output (ml/hour) >30 20–30 5–15 Negligible

CNS symptoms Normal Anxious Confused Lethargic

Crit Care. 2004; 8(5): 373–381.

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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 (next page)

Distributive Shock

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

Distributive Shock

Septic Shock

SIRS 2 or more of the following: Temp >38 or <36 HR > 90 RR > 20 WBC > 20K >10% bands

Sepsis SIRS in the presence of suspected or documented infection

Severe Sepsis Sepsis with hypotension, hypoperfusion, or organ dysfunction

Septic Shock Sepsis with hyotension unresponsive to volume resuscitation, and evidence of hypoperfusion or organ dysfunction

MODS Dysfunction of more than one organ

Clinical Presentation

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

Hypotension (SBP<90 or Delta>40) 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?

Manage the Emergency

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

Determine the Cause

What if you’re wrong?

85 y/o M 4 hours postop S/P sigmoid resection for perforated diverticulitis is hypotensive on a monitored bed at 70/40

Likely causes Best actions for the first 5 minutes?

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

Controversies

IVF Resuscitation Limited resuscitation in penetrating trauma Use of hypertonic saline resuscitation in trauma Endpoints for prolonged resuscitation

Pressors Best pressors for distributive shock

Monitoring Most appropriate timing and use for PA

catheterization or intermittent echocardiogram