Cardiac arrest Flashcards
What is cardiac arrest?
Acute cessation of cardiac function leading to circulatory failure.
What is the aetiology of cardiac arrest? (x8)
- Classical reversible causes of cardiac arrest are the four Hs and four Ts:
- Hypoxia, Hypothermia, Hypovolaemia, Hypo- or hyperkalaemia
- Tamponade, Tension pneumothorax, Thromboembolism, Toxins and other metabolic disorders such as drugs, therapeutic agents and sepsis
What is the pathophysiology of cardiac arrest? (x4 +1 point)
- Characterised by four different types of cardiac arrythmias:
- Ventricular fibrillation
- Pulseless VT (includes Torsades de pointes and often related to hypomagnesaemia)
- Pulseless electrical activity: organised electrical depolarisation of the myocardium without appropriate myocardial contraction, leading to inadequate circulation. The mechanism for this is loss of contractile force despite normal electrical stimulation
- Asystole
- ISCHAEMIA: mechanism for arrythmia is usually re-entrant circuit generated by surviving myofibrils within areas of fibrosis
What are the most common types of cardiac arrest?
VT and VF, most commonly with IHD aetiology.
Which cardiac arrest types are shockable?
Pulseless VT and VF
What is the definition of VT?
More than 3 successive ventricular extrasystoles (broad QRS complexes >120ms) at a rate of over 120/min.
What is the definition of VF?
Irregular, rapid ventricular activation with no CO.
What are the signs and symptoms of cardiac arrest?
Unconscious, not breathing, absent peripheral and central pulses. Often preceded by chest pain or dyspnoea
What are the risk factors for cardiac arrest?
IHD, hypertrophic cardiomyopathy, long QT syndrome, acute medical/surgical emergency, illicit substances such as cocaine and opioids, Brugada syndrome.
What is Brugada syndrome?
Autosomal dominant condition that affects depolarising sodium channels, associated with pseudo-right bundle branch block pattern and ST-segment elevations in leads V1 through V3.
What are the investigations for cardiac arrest? (x3)
- Cardiac monitoring as rhythm dictates management
- ABG, U&Es, FBC, cardiac biomarkers (troponin, CK, BNP), toxicology screen for aetiology
- Electrocardiography for aetiology (valvular disorders, tamponade, cardiomyopathy)
How is cardiac arrest managed: BLS?
- If the arrest is witnessed, precordial thump with ulnar aspect of hand (see photo)
- A: clear and maintain airway with head tilt, jaw thrust and chin lift if C-spine consideration
- B: look, listen AND feel. If not breathing, give two effective breaths immediately
- C: assess carotid pulse for 10 seconds. If absent, give 100 compressions/min. Continue cycles of 30 compressions for every two breaths
- Proceed to ALS
How is cardiac arrest managed: ALS? (x3 and x3 +1)
- Attach cardiac monitor and defibrillator
- Assess the rhythm:
- (A) If shockable, defibrillate once with 150-360 J for biphasic defibrillators or 360 J for monophasic defibrillators. Then resume CPR for 2 mins (cycles of 30 compressions for every two breaths), reassess, then continue to defibrillate/CPR. Administer 1mg IV adrenaline after second defibrillation and again every 3-5 mins. If shockable rhythm persists after third shock, administer amiodarone (anti-arrythmic) 300mg IV bolus (or lidocaine)
- (B) If PEA or asystole, CPR for 2 mins (cycles of 30 compressions for every two breaths), reassess, then continue CPR. Administer 1mg IV adrenaline every 3-5 mins, and 3mg IV atropine (once only) if asystole/PEA with rate less than 60/min
- During asystole, secure airway (endotracheal intubation and high-flow oxygen). Once airway is secure, give continuous compressions and breaths.
- Consider 2g IV magnesium over 5-10 mins as a single dose in patients with cardiac arrest due to Torsades des pointes
What are the complications of cardiac arrest? (x6)
- Death
- Rib fractures
- Irreversible hypoxic brain damage
- Ischaemic liver injury (‘shock liver’)
- Renal tubular necrosis
- Recurrence of cardiac arrest
