Shock

Definition

• Inadequate tissue perfusion and oxygenation leading to multiorgan dysfunction

Shock Index

• Heart Rate / Systolic Blood Pressure
• Usual range 0.5 to 0.7
• If over 0.9, suggests impaired cardiac function and predicts mortality

Approach

graph TB

Start["BP = CO x SVR"] --> LowCO["Low cardiac output (CO)"]
Start --> LowSVR["Low systemic vascular resistance (SVR)"]

LowCO --> CNC["Cold and clammy"]
CNC --> HighJVP["High JVP"]
CNC --> LowJVP["Low JVP"]

HighJVP --> Cardio["Cardiogenic shock"]
HighJVP --> Obstruct["Obstructive shock"]
LowJVP --> Hypo["Hypovolemic shock"]

LowSVR --> WNB["Warm and bounding pulse"]
WNB --> Distro["Distributive shock"]

Differential Diagnosis

• Cardiogenic shock
• Obstructive shock
  • Massive pulmonary embolism
  • Tension pneumothorax
  • Cardiac tamponade
  • Right ventricular infarction
• Hypovolemic shock
• Distributive shock
  • Sepsis
  • Anaphylaxis
  • Systemic inflammatory response
  • Mitochondrial dysfunction
    • Cyanide poisoning
  • Adrenal crisis
  • Myxedema coma
  • Neurogenic

Clinical Presentation

• Hypoperfusion
  • Low BP (SBP < 90, MAP < 65, decrease in SBP by 40+)
  • BP unresponsive to fluid challenge
  • Long cap refill
• End-organ dysfunction
  • Lightheadedness
  • Confusion
  • Diaphoresis
  • Decreased urine output
  • Increased creatinine
  • Chest pain
  • Other ischemic pain

Classes of shock

	Class I	Class II	Class III	Class IV
Blood loss (mL)	<750	750-1500	1500-200	>2000
Blood loss (%)	<15%	15-30%	30-40%	>40%
HR	<100	>100	>120	>140
BP	Normal	Normal	Low	Low
Pulse pressure	Normal	Low	Low	Low
RR	14-20	20-30	30-40	>40
Urine output mL/h	>30	20-30	5-15	anuria
Mental status	anxious	anxious	confused	lethargic