RCA Fundamentals

INCIDENCE

Australia: 112 per 100,000 population

Globally varies

Asia 53 per 100 000 person-years

Europe 86.4 per 100 000 person-years

North America 98 per 100 000 person-years

AGE & GENDER: 66

Median age: 66 years

Male: 66%

80% OOHCA have a cardiac cause of arrest.
This proportion is slightly decreasing with time.

Cardiac causes (up to 80%)

• Ischaemic heart disease
  • Acute myocardial infarction
• Non-atherosclerotic disease of the coronary arteries
• Lethal arrhythmia without ischaemic heart disease
  • Wolff-Parkinson-White syndrome
  • Long QT syndrome
  • Brugada syndrome
  • Catecholaminergic polymorphic ventricular tachycardia
• Cardiomyopathy
  • Acute on chronic heart failure
  • Acute heart failure secondary to valvular heart disease
  • Myocarditis
  • Dilated cardiomyopathy
  • Left ventricular non-compaction cardiomyopathy
  • Hypertrophic cardiomyopathy
  • Arrhythmogenic right ventricular cardiomyopathy
  • Other infiltrative or inflammatory myocardial disease, or both
• Valvular heart disease
• Congenital heart disease

Non-cardiac causes

• Trauma
• Malignancy
• Non-traumatic bleeding
  • Gastrointestinal
  • Gynaecological
  • Cerebrovascular
  • Acute aortic dissection
• Asphyxia
  • Submersion (near drowning)
  • Hanging
• Hypoxia
  • Pneumonia
  • Asthma or chronic obstructive pulmonary disease
  • Carbon monoxide poisoning
  • Pulmonary embolism
• Drug overdose
• Hypoglycaemia
• Hypothermia
• Epilepsy
• Septic shock
• Dehydration and malnutrition

The causes are not listed in order of frequency and the list is not intended to be exhaustive.

REVERSIBLE Causes (which include the above):

> Hypoxaemia

> Hypovolaemia

> Hypo/Hyperkalaemia and other metabolic disorders including acidosis and disturbances of magnesium and calcium

> Hypo/Hyperthermia

> Tension pneumothorax

> Tamponade: pericardial

> Toxins/poisons/drugs including carbon monoxide, and cyclic antidepressants

> Thrombosis: pulmonary embolus /acute myocardial infarction.

[Flow diagram, dividing into cardiac and non-cardiac causes?]
REF

LOCATION

Public (18%) vs other (82%) 1

BYSTANDER CPR

41% receive bystander CPR 1 

ATTEMPTED RESUSCITATION

48% have attempted resuscitation by EMS 1

INITIAL RHYTHM

[Pie chart]
VT/VF 28%
PEA 25%
Asystole 47% 1
The proportion of patients with an initial shockable rhythm is decreasing

OUTCOMES

Of those resuscitated:
28% survive the initial event
12% survive to hospital discharge or 30 days
95% of patients surviving to hospital discharge had an initial shockable rhythm 4
Only 4% of patients with PEA survive to hospital discharge 4

Receives 15% of cardiac output

• Cerebral blood flow (CBF) = approximately 750 mL/min

Accounts for 20% of body’s total basal O2 consumption

• Cerebral metabolic rate of O2 consumption (CMRO2) at rest = 50 mL/min
• Organ with the highest metabolic requirements despite being only 2% of total body weight

Very sensitive to interruptions in blood supply and hypoxia because:

• It has a high CMRO2 i.e. high oxygen demand
• It is almost entirely dependent on oxygen-dependent metabolism of glucose for energy and does not store any substrate (glucose or oxygen), therefore requires a constant and uninterrupted blood supply

> Loss of cardiac output results in cessation of cerebral blood flow

> Neurons are dependent on glucose for energy and have no nutrient stores → neuroglycopaenia and metabolic crisis occur within minutes → cell death

> Reduced cerebral oxygen delivery from loss of CBF → cerebral lactate accumulation and intracellular acidosis from anaerobic metabolism → cell death

> Dysfunction of energy-dependent ion channels leads to neuronal and endothelial dysfunction → cerebral oedema, formation of microthrombi and cell death

Subsequent brain injury may occur from:

• Reperfusion injury
• Microcirculatory dysfunction
• Impaired cerebral autoregulation
• Hypoxaemia/hyperoxia
• Hyperthermia
• Altered pCO2
• Anaemia

Most susceptible structures:

• Hippocampus
• Thalamus
• Basal ganglia
• Cerebral cortex
• Cerebellum
• Corpus striatum