Shock

Question 1

What is the definition of shock

Answer 1

Acute circulatory failure causing inadequate perfusion and organ dysfunction

(Low MAP and evidence of organ dysfunction)

Question 2

Classify shock

Answer 2

Cardiogenic
- LV failure
- RV failure
- Obstruction (PE/Tamponade/Tension/Abdo compartment syndrome/high peep/stenotic valves)
- Dysrhythmias

Hypovolaemic
- Haemorrhage
- Dehydration: Urinary, GI, Skin, Lungs
- 3rd spacing: Pancreatitis, portal HPT, burns

Distributive
- Septic
- Anaphylactic
- Neurogenic spinal shock - sudden SNS collapse/vasodilation
- Adrenal insufficiency

Neurogenic
- Spinal shock (sudden collapse) - also distributive

Obstructive
- PE/Tamponade/Tension/Abdo compartment syndrome/ PEEP

Question 3

What is the formula for O2 consumption

Answer 3

VO2 = CO x (CaO2 - CvO2)

VO2 = CO x [(SaO2 x Hb x 1.34) - (SvO2 x Hb x 1.34)]

Question 4

What is the formula for O2 delivery

Answer 4

DO2 = CO x CaO2

Question 5

What is the formula for CaO2

Answer 5

CaO2 = SaO2 x Hb x 1.34 + (0.023 x PaO2)

Question 6

How can O2 delivery be optimized

Answer 6

DO2 = CO x [SaO2 x Hb x 1.34] + (PaO2 x 0.023)

1. Increased CO
2. Increased SaO2/PaO2
3. Increased Hb

Question 7

Describe the receptor, actions and classification of the following vasopressors
1. Adrenalin
2. Dobutamine
3. Dopamine

Answer 7

Adrenalin
- Receptor: a1, B1, B2
- Actions: Increase HR and SV. Peripheral VC
- Inopressor

Dobutamine
- Receptor: B1, B2
- Actions: Increase HR and SV. Peripheral VD
- Inodilator

Dopamine
- Receptor: DA, a1, B1
- Actions < 5ug/kg/min - DA receptors increase splanchnic and renal perfusion (but ineffective GFR)
- Actions > 5 ug/kg/min - Cardiac effects and vasoconstriction

Question 8

What is your approach to a patient who does not respond to vasopressors

Answer 8

1. Check equipment and monitoring
   - A-line zeroed, flushed, functional, add NIBP.
2. Optimize fluid status
3. Treat dysrhythmias
4. Exclude mechanical causes of low CO
   - Tension pneumothorax
   - Massive PE
   - Cardiac tamponade
   - High PEEP
5. Correct agent. Correct dose. Correct rate.
6. Consider NaHCO# if severely acidotic - myocardium responds poorly to inotropes in the presence of acidosis
7. Correct Ca
8. Consider tachyphylaxis –> change the agent

Question 9

List the adverse effects of vasoactive agents

Answer 9

1. Hypoperfusion
   - extremities
   - mesenteric organs
   - Kidneys
2. Dysrhythmias
3. Myocardial ischaemia
4. Peripheral extravasation into the surrounding tissue
5. Hyperglycaemia
6. Unique drug interactions and contraindications
   - Phaeochromocytoma
   - Monoamine oxidase inhibitors