Non-shockable Rhythm Arm of The ALS Algorithm – Reversible Causes of PEA

The reversible causes of PEA will now be discussed in detail:


Each patient’s inspired oxygen should be as close to 100% as possible. There is a need for quality bag-mask ventilation, with the use of airway adjuncts and a two-person technique as necessary.

Exhaled carbon dioxide identified by quantitative or qualitative end-tidal analysis reliably indicates the tracheal tube lies below the cords [3,4].

To check for correct tracheal tube placement, look for chest expansion, misting of the tube, and auscultate for presence of breath sounds in both axilla’s, and absence of breath sounds in epigastrium. However, these are all unreliable and secondary confirmation should be with waveform capnography. Use auscultation to check that the tube is not in the right main bronchus.

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Positive end-tidal carbon dioxide analysis reliably indicates the tracheal tube lies below the cords.


Seek out clues for massive blood or fluid loss in the history and examination.

Ruptured abdominal aortic aneurysm is a consideration in the elderly; these patients are not necessarily good candidates for surgery unless their resuscitation is prompt and successful, typically with aggressive (warmed) fluid challenge.


The most common metabolic emergency to result in cardiac arrest.

Hyperkalaemia should be considered, particularly in any renal patient. Typically, the QRS complexes are wide and sinusoidal at this stage. 10 mg IV 10% calcium chloride is warranted urgently. Proof of diagnosis should be readily available by means of venous or arterial blood gas analysis. Rarely, other electrolyte disturbances can cause cardiac arrest and are dealt with elsewhere.

Severe hyperkalaemia has been defined as a serum potassium concentration >6.5mmol/L.

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Consider hyperkalaemia as the cause of cardiac arrest in any renal patient.


Patients may well require and survive prolonged CPR, whilst attempts are made to warm them. The prognosis is largely dependent on the underlying cause.

A low reading thermometer is needed to measure core temperature and confirm the diagnosis.[1]

  • Oesophageal measurement correlates well with heart temperature but can only be used in patient with an advanced airway
  • rectal and bladder temperatures lag behind core temperature and are not recommended in patients with severe hypothermia.[1]

Withhold adrenaline and other CPR drugs until the patient has been warmed to a core temperature of ≥30°.

As normothermia is approached (≥35°), use standard drug protocols.

Note therapeutic hypothermia refers to hypothermia induced by the Emergency Physician in those patients with return of spontaneous circulation and who remain comatose.


Thrombosis, meaning massive pulmonary embolism, is a common cause of cardiac arrest, particularly PEA.

Consider a 50 mg bolus of alteplase if massive PE is thought to be the cause of cardiac arrest [5].

Whilst arterial blood gas analysis typically reveals oxygen saturation greater than 94% during quality CPR, reduced saturation is suspicious of massive pulmonary embolism.


Even if suspected, the treatment for most agents is supportive, carbon monoxide included.

Specific treatment exists for cyanide poisoning (consider in those patients rescued from fires), tricyclic antidepressants, opiates and many more.

Tension pneumothorax

Spontaneous tension pneumothorax is exceptionally rare but easily treated.

Tension pneumothorax is one of the immediately life-threatening injuries in the chest that needs identifying in the primary survey following trauma.

Tension pneumothorax following central line insertion should also be considered.

Simple pneumothoraces may tension during positive pressure ventilation.

Ventilation should become increasingly difficult by hand, or, if the patient is on a ventilator, it should alarm, if the parameters have been set appropriately.

Management of tension pneumothorax is with decompression and the method is guided by the skillset within the team.

  • Needle decompression –Followed by chest drain insertion.
  • Open thoracostomy – Followed by chest drain insertion at ROSC.
  • Clamshell thoracotomy – for use in traumatic cardiac arrest, only by appropriately trained clinicians.

Tamponade (meaning cardiac tamponade)

Tamponade should always be considered following penetrating injury.

Note the associated wound may have been inflicted to the posterior chest wall.

Clinical signs are unhelpful in cardiac arrest. Bedside ultrasound should confirm a haemopericardium.

Thoracotomy is indicated within 10 minutes of the cardiac arrest.

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