Cardiorespiratory arrest and ALS Flashcards
What are the most common potentially reversible causes of cardiac arrest?
four Hs and four Ts
- Hypoxia, Hypovolaemia, Hypo/Hyperkalaemia, Hypothermia
- Thrombosis, Tamponade, Toxins, Tension pneumothorax
If the most likely cause of a cardiac arrest is identified as hypoxia, how should this be managed?
- Ensure the airway is patent
- Ventilate the lungs using high-flow oxygen
- Although it has been common practice to hyperventilate a patient in cardiac arrest based on the premise that this will help to reduce any hypercarbia, this practice should be avoided as hyperventilation reduces coronary perfusion pressure and worsens outcome.
What would suggest that hypovolaemia is the cause of cardiac arrest? How should this be managed?
- Clues to hypovolaemia may come from the patient’s history, observation charts or clinical examination.
- The cause of hypovolaemia may be obvious (e.g. blood loss or severe diarrhoea) or more subtle (e.g. severe sepsis or anaphylaxis).
- If hypovolaemia is suspected, rapidly infuse intravenous fluids.
How would you rule out hyper/hypokalaemia as the cause of cardiac arrest?
- Near-patient-testing equipment allows the rapid measurement of potassium and glucose.
- Review the patient’s latest laboratory results.
How should hyperkalaemia be managed if found to be the cause of the cardiac arrest?
Immediate treatment of hyperkalaemia is administration of calcium chloride followed by insulin/dextrose infusion.
How should hypokalaemia be managed if found to be the cause of a cardiac arrest?
Low potassium/magnesium levels may be treated with an infusion of a solution containing the deficient substance.
Is hypothermia a common cause of in-hospital cardiac arrest?
No - it is rare
How would you rule out hypothermia as the cause of cardiac arrest?
Measure core temperature with a low-reading thermometer. (rectal thermometer)
How should hypothermia be managed if found to be the cause of cardiac arrest?
Use active re-warming techniques to treat a hypothermic patient in cardiac arrest.
Cardiopulmonary bypass may be considered if facilities are immediately available and active re-warming strategies fail.
Coronary thrombosis is a common cause of cardiac arrest. What should be done if coronary thrombosis is suspected to be the cause of cardiac arrest?
- If an ACS is suspected as the cause of refractory cardiac arrest it may be feasible to perform percutaneous coronary angiography and percutaneous coronary intervention during ongoing CPR.
- This would require the use of an automated CPR device and/or extracorporeal CPR to maintain circulation during the procedure.
Which conditions are classified as a ‘thrombosis’ cause of cardiac arrest?
- Coronary thrombosis
- Massive pulmonary embolism
If a massive pulmonary embolism is found to be the cause of cardiac arrest, how should the patient be managed?
- Consider giving a fibrinolytic drug immediately.
- Survival and good neurological outcome have been reported in cases requiring prolonged CPR. Consider performing CPR for at least 60-90 min in this setting.
Which cause of cardiac arrest warrants performing CPR for a prolonged period of time e.g. 30-90 mins?
Massive PE
When should cardiac tamponade be considered as the cause of cardiac arrest?
Tamponade should be considered after penetrating chest trauma or after cardiac surgery, device implantation (e.g. pacemaker) and percutaneous coronary intervention.
If you are suspecting cardiac tamponade as the cause of cardiac arrest, how should the diagnosis be confirmed?
Cardiac tamponade is difficult to diagnose without focussed cardiac ultrasound as many of the features on clinical examination are difficult or impossible to elicit during cardiac arrest.
What is the management of cardiac tamponade?
Treatment is with either needle pericardiocentesis or resuscitative thoracotomy.
When should drug toxicity be considered as a cause of cardiac arrest?
Drug toxicity is a relatively unlikely cause of cardiac arrest unless there is evidence of deliberate overdose or suspicion of substance abuse.
For in-patients, a review of the patient’s drug chart may be helpful.
What should be checked in an intubated patient who has arrested?
In an intubated patient patient check the tube position as intubation of the right main bronchus can further complicate a tension pneumothorax, which can be difficult to diagnose during cardiac arrest.
What would suggest tension pneumothorax as the cause of cardiac arrest?
It may be indicated by unilateral expansion of the chest, shift of the trachea, or subcutaneous emphysema.
Pleural ultrasound in skilled hands is faster and more sensitive than chest X-ray for the detection of pneumothorax.
How should tension pneumothorax be managed?
Early needle decompression (thoracocentesis) followed by chest drain insertion is needed. Needle decompression may fail if the needle used is too short.
In a ventilated patient, thoracostomy (a surgical hole in the chest wall and pleura) may be quicker to perform and more effective in releasing the tension.
It is now 5 mins into CPR. The anaesthetist has already ventilated the patient. The end-tidal CO2 has risen to 5.2 and the defibrillator is now showing sinus rhythm.
Should you continue with CPR or reassess the patient with an A-E approach?
The sudden rise in end-tidal CO2 suggests return of spontaneous circulation. When this is seen or when a patient starts displaying signs of life e.g. sinus rhythm, chest compressions should be paused and patient should be reassessed.
What is capnography used for?
Capnography represents the amount of carbon dioxide in exhaled air.
This assesses ventilation, which is different from oxygenation.
What is the difference between ventilation and oxygenation?
Ventilation is the air movement in and out of the lungs, while oxygenation is the amount of oxygen inhaled by the lungs that reaches the bloodstream.
How do you measure capnography?
Two sensors can be used to measure capnography.
- In patients who are breathing, nasal prongs can be applied that capture exhaled air. Those prongs can also be used to administer a small amount of oxygen, or applied underneath a non-rebreather or CPAP mask.
- In patients who require assisted ventilation, another adapter can be attached to a BVM and advanced airway device.


