3+ Circulatory Shock

Question 1

What is circulatory shock?

Answer 1

A life-threatening, generalised form fo circulatory failure with inadequate oxygen delivery to, and consequentially utilisation by, the cells

Question 2

What are the 4 types of shock?

Answer 2

1. Cardiogenic (pump dysfunction)
   - MI, arrythmia etc
2. Distributive shock (failure of vasoregulation)
   - Sepsis, anaphylaxis, brainstem injury/spinal injury (neurogenic)
3. Hypovolaemic shock (loss of intravascular volume)
   - Haemorrhagic causes: GIT bleeding, trauma, dehydration
   - Non-haemorrhagic: burns, ketoacidosis
4. Obstructive shock (barriers to cardiac flow or filling)
   - PE restricts pulmonary flow, cardiac tamponade, pneumothorax can cause cardiac filling restriction

Question 3

What are the causes of cardiogenic shock?

Answer 3

• Most commonly after an MI
• Tachyarrhythmias (AF, ventricular tachycardia)
• Bradyarrhythmia
• Toxic substances
• Infection: infective endocarditis, sepsis
• Acute mechanical causes: myocardial rupture, chest trauma, acute valvular incompetence

Question 4

What is the pathophysiology of cardiogenic shock?

Answer 4

• Tissue hypoperfusion from loss of cardiac output induces tissue inflammation
• Shock can self-perpetuate by inducing additional cellular-level shock response cytokines –> SIRS

Question 5

How does cardiogenic shock present?

Answer 5

• Hypotension
• Tachycardia
• Cool, clammy peripheries
• Mottled appearance
• Sweating
• Cyanosis
• Oliguria (low urine output)
• Mental state changes
• Fever if septic
• Dyspnoea, tachypnoea

Question 6

What Ix do you do for cardiogenic shock?

Answer 6

Bedside:
- ECG
- UA
- BSL

Labs:
- ABG: check lactate: if over 2mmol/l = shock
- VBG: metabolic acidosis
- FBC: Hb for bleeding, WCC for infection
- UEC: urea + creatinine = renal hypoperfusion
- Coags: trauma, DIC
- CRP
- High procalcitonin = sepsis

Imaging:
- CXR: consolidation, pleural effusion from HF, PE
- CT if suspect AAA
- CTPA if suspect PE

Question 7

How do you manage cardiogenic shock?

Answer 7

Airway: open, suction if needed, intubate if severe

Breathing: target O2 of 94-96 in patients not at risk of hypercapnia

Circulatory:
- Treat underlying cause
IV fluids in all patients except with cardiogenic pulmonary oedema (fluid challenge: bolus 500mL)
- Loop diuretic if pul oedema and fluid overload (frusemide)
- Vasopressor (NA) if hypotension despite fluids
- Inotrope (dobutamine) if impaired cardiac function and low CO + signs of tissue hypoperfusion after SV and HR have increased

Question 8

What are the complications of cardiogenic shock?

Answer 8

Volume overload-induced pulmonary oedema
Organ failure
Vasopressor induced gangrene