Cardiac arrest

Question 1

What is cardiac arrest?

Answer 1

Acute cessation of cardiac function.

Question 2

What are the different causes of cardiac arrest?

Answer 2

1. Result of 4 specific cardiac arrhythmias → ventricular fibrillation (VF), pulseless ventricular tachycardia (VT), pulseless electrical activity (PEA), and asystole
2. Reversible Causes of Cardiac Arrest:
   - 4 H’s ⇒ hypoxia (give oxygen), hypothermia, hyperkalaemia/hypokalaemia, hypovolaemia (correct with IV fluids)
   - 4 T’s ⇒ thrombosis, tension pneumothorax (may cause PEA), tamponade (esp. in trauma), toxins
3. Other causes of cardiac arrest: 
   - Coronary artery disease- TOP CAUSE 
   - Left ventricle hypertrophy (LVH) due to; longstanding hypertension, hypertrophic cardiomyopathy (HOCM) or HF 
   - Inherited conduction abnormalities: long QT syndrome (type of VT) 
   - Non-cardiac causes: trauma, bleeding, overdose, drowning, PE 

Question 3

What signs of cardiac arrest can be found on physical examination?

Answer 3

• Sudden collapse 
• Loss of consciousness 
• Respiratory arrest 
• Absent carotid pulses 
• Enlarged pupils (within 45 seconds) 

Question 4

What investigations are used to diagnose/ monitor cardiac arrest?

Answer 4

1. Continuous Cardiac Monitoring → identify rhythm, may be shockable rhythm (VT/VF) or non-shockable rhythm (asystole/PEA)
2. ECG → should be performed immediately after return of spontaneous circulation
3. FBC → arrest may be due to hypovolaemia
4. Serum Electrolytes → arrest may be due to electrolyte abnormalities, particularly hyperkalaemia and hypokalaemia

Question 5

How would you manage a cardiac arrest?

Answer 5

1. Shockable Rhythms (Pulseless VT or VF) → CPR (30:2 ratio) and Defibrillation + Adrenaline. May also use anti-arrythmic such as amiodarone. Torsade de Pointes = IV magnesium sulphate:
   a. CPR and then defibrillate once
   b. Resume CPR for 2 minutes
   c. Administer IV adrenaline 1mg after third shock and then every other cycle (ie. every 3-5 mins, cycles 3,5,7…)
   d. If persisting after 3rd shock, administer IV amiodarone 300mg (one off dose)
   If witnessed in a monitored patient → 3 successive shocks (rather than 1 shock followed by CPR)
2. Non-Shockable Rhythms (PEA or Asystole) → CPR and Adrenaline
   a. CPR for 2 minutes, then reassess
   b. Administer IV adrenaline 1mg ASAP (after the first cycle), and then every other cycle (ie. every 3-5 mins, cycles 1,3,5…)
   c. Atropine (once) if rate <60bpm

Question 6

How can some reversible causes of cardiac arrest be reversed/ treated

Answer 6

Hypothermia- warm slowly with bair hugger 

Hypokalaemia and Hyperkalaemia- correction of electrolyte levels 

Hypovolaemia- IV colloids, crystalloids and blood products 

Tamponade- pericardiocentesis 

Tension Pneumothorax- aspiration & chest drain 

Thromboembolism- treat as PE or MI 

Toxins- use antidote for given toxin