Shock DDx

Reviewed and revised 31 August 2016

OVERVIEW

Shock is a state of circulatory failure characterised by globally impaired tissue perfusion that is insufficient for needs of the body.

CLASSIFICATION

Classification (shock can be classified as PROVED?)

• cardiogenic (Pump)
• Rhythm abnormalities (some purists exclude dysrhythmia as a cause of cardiogenic shock)
• Obstructive
• hypovolemia (Volume)
• Endocrine causes (often mixed classification, but a useful subheading to make sure endocrine causes aren’t missed!)
• Distributive (due to vasodilation)
• ? = is it real? (check the BP measurement, is the arterial line in an artery, is the transducer at the correct height?)

Remember that drugs and toxic exposures can contribute to cardiogenic, rhythm, or distributive causes of shock.

CARDIOGENIC SHOCK

Impaired contractility

• Myocardial ischemia and compliations
  • Infarction — anterior MI, reinfarction, right ventricular infarction, myocardial stunning
  • Acute mitral regurgitation due to papillary muscle rupture
  • Ventricular septal rupture
  • Left ventricular free wall rupture and tamponade
• Myocarditis
• Myocardial contusion
• Tako-Tsubo cardiomyopathy
• Septic shock
• Poisoning or toxic exposure including calcium channel blockers, beta-blockers and digoxin
• End stage cardiomyopathy

Dysrhythmia

• Tachycardias
• Bradycardias

Valvular dysfunction

• Severe aortic regurgitation
• Severe aortic or mitral stenosis

Left ventricular outflow tract obstruction

• Hypertrophic cardiomyopathy
• Left atrial myxoma

OBSTRUCTIVE SHOCK

Within the circulatory system

• Massive pulmonary embolus
• atrial thrombus or myxoma
• occulsive valvular lesion
• other emboli (e.g. air, amniotic fluid)

External to the circulatory system

• Cardiac tamponade
• abdominal compartment syndrome
• Tension pneumothorax
• Dynamic hyperinflation (e.g. severe asthma)
• Tension pneumomedistinum
• caval compression (e.g. supine hypotension syndrome in the pregnant female)

HYPOVOLAEMIC SHOCK

Hemorrhage

• Traumatic
  • Major vessel injury
  • Pelvic vessel disruption
  • Massive hemothorax
  • Intra-abdominal hemorrhage
  • Retroperitoneal hemorrhage
  • Long bone fracture
  • External blood loss
• Non traumatic
  • Gastrointestinal bleeding
  • Epistaxis
  • Hemorrhagic pancreatitis
  • Aneurysm rupture
  • Ectopic pregnancy
  • Postpartum
  • Coagulopathy

Fluid loss

• GI losses (vomiting, diarrhoea, short gut, etc)
• Excessive diuresis (diabetes insipidus, diuretics)
• Excessive diaphoresis (heat-related illness)
• Diabetic ketoacidosis
• Burns
• “Third spacing” (pancreatitis, severe sepsis, anaphylaxis)
• Iatrogenic (post-dialysis)

DISTRIBUTIVE SHOCK

• neurogenic shock
• liver failure
• adrenal insufficiency
• anaphylaxis
• septic shock
• post-bypass vasoplegia
• drugs and toxic exposures, e.g. calcium channel blockers, epidural anaesthesia

ENDOCRINE AND METABOLIC CAUSES OF SHOCK

• Adrenal insufficiency
• Hypothyroidism
• Hyperthyroidism
• Diabetic ketoacidosis
• Severe acidosis/ alkalosis and electrolyte disturbances (e.g. hypocalcemia)

? (ERRORS AND ARTEFACTS)

• non-invasive blood pressure measurement error
• arterial line inadvertently sited in a vein
• arterial line transducer position higher than the right atrium