Cardiac Arrest

I know I say this pretty much most posts, but this is really super important. Like super. I’ve never been in a cardiac arrest situation, never seen one, except on TV, but it’s good to know what to do should the need arise, even if you’re not a healthcare professional.

Cardiac Arrest

Definition: acute cessation of cardiac function

Aetiology/ risk factors:

Can be remembered as the 4 Hs and 4 Ts. In an advanced life support situation, whilst resuscitating the patient, try to ascertain the cause so it can be corrected, if possible.

4 Hs:


Hypovolaemia (shock)

Hypo/hyperkalaemia, metabolic e.g. hypoglycaemia and other U&E imbalances


4 Ts:

Thrombosis- coronary (MI) or pulmonary (PE)

Tamponade- cardiac

Toxins e.g. digoxin

Tension pneumothorax

Other: trauma, electrocution, hypercapnia

Signs and symptoms:

-unconscious, non-responsive

-apnoeic (not breathing), or abnormal breathing (e.g. occasional gasps)

-absent carotid pulse

Investigations and Management:

Basic Life Support (anyone can do this)



Danger- check for danger in surroundings and keep yourself self and the person safe

Response- check to see if person is responsive; do they respond to your voice? Pain?

-If unresponsive move onto next step.

Call for help as early as possible. (Definitely once you’ve realised that they are not breathing normally). This will be the resuscitation team if in hospital or an ambulance if on the street.)

Whenever we practiced BLS in med school and we were faking scenarios, you always had to tell the person next to you to call an ambulance and to come back when they were done so you weren’t left hanging. Also, send someone to fetch you a defibrillator, if possible, as this can really make a difference to the outcome.

Defibrillators can be found in many places, including tube stations and other large/ public buildings. They are labelled AED (Automated External Defibrillator) and look like this:

Image result for aed uk

Airway- head tilt (if no spine injury) + chin lift/ jaw thrust. Clear the mouth. Aim is to keep the airway open and clear. Remove any obstruction, even if it’s something gross.

Breathing- check breathing. If not breathing normally, give 2 breaths after 1st set of chest compressions, each inflation ~1 second. Use a specialised bag and mask system if available and you have a spare set of hands, otherwise, mouth to mouth with a valved pocket mask, and if you don’t have one of those, then literally mouth to mouth, making sure to form a tight seal.

Chest compressions- 30 compressions to 2 breaths. CPR should not be interrupted except to give shocks. Use the heel of your hand with straight elbows and one hand over the other, fingers interlocked, directing the weight of your body through your vertical, straight arms. Centre over the lower third of the sternum, aiming for a 5-6 cm compression at 100-120/min. (To the tune of ‘staying alive’- the chorus).

Alongside continuing with the CPR as outlined above, get someone to open the AED box and follow the voice instructions. It does pretty much the whole job and you don’t have to know anything about heart rhythms or how much shock to apply. Just open the box and do as it says. Don’t stop CPR, except when you need to apply shock to the person (if this is indicated). The AED will direct you as to how to put on the adhesive pads and when you should stand back so that shock can be applied. Continue CPR, and applying shock, as directed by the AED, until an ambulance arrives.


I’ve never done this for real but I’ve done quite a few dummies and chest compressions are really tiring. I suppose in real life, the adrenaline rush would keep you going, but on a model, 2 sets in and I’m already achey.

Also, in real life, you will probably have people around you and so once you start getting tired and ineffective, finish your set of compressions, give 2 breaths and then swap with another person.

And don’t worry if you break ribs, I’ve been told that this is likely if you are doing it correctly.


Advanced Life Support


This bit is for a hospital setting:

-Throughout this CPR should be continuous, as outlined above, and non-interrupted, except to defibrillate or intubate. Do not stop > 5s. Once you have defibrillated continue CPR immediately.

-Place defibrillator paddles on chest as soon as possible and set monitor to assess the rhythm through the paddles (if delay in attaching ECG leads).

Self-adhesive defibrillation/monitoring pads are placed: one below the right clavicle and the other in the V6 position in the midaxillary line.

Image result for defibrillator pads position

⇒Ventricular fibrillation/ pulseless ventricular tachycardia = shockable rhythms

Image result for ecg ventricular fibrillation


Image result for ventricular tachycardia

VT- regular, wide QRS complexes at a rate > 100 bpm. P waves are absent or non-related.

Defibrillate without delay- 360 J monophasic or 150-360J biphasic.

During shock administration, responders should stand back and oxygen delivery devices should be removed, as appropriate.

-Continue CPR.


Asystole/ Pulseless Electrical Activity = non-shockable rhythm

Whenever a diagnosis of asystole is made, check the ECG carefully for the presence of P waves because the patient may respond to cardiac pacing when there is ventricular standstill with continuing P waves.


Image result for asystole

VF to Asystole (flat-line)

PEA will show an ECG normally associated with cardiac output, but they will have no pulse.

-Do not defibrillate.

-Give ADRENALINE 1mg IV/IO as soon as IV/IO access achieved. (NB: different to anaphylaxis, which is 0.5mg IM)

-Continue CPR.

-Give ADRENALINE 1mg IV/IO every 3-5 minutes until return of spontaneous circulation is achieved.


-Obtain IV access and intubation if skilled person present, otherwise secure airway. If IV access fails, the intraosseous route is recommended.

-Give oxygen during CPR and consider an advanced airway.

Waveform capnography (monitoring concentration of CO2 patient is inspiring and expiring) must be used to confirm and continually monitor tracheal tube placement, and may be used to monitor the quality of CPR and to provide an early indication of return of spontaneous circulation (ROSC).

-Once advanced airway is in place, chest compressions are continuous (without the 2 breaths for every 30).

-Look for reversible causes of cardiac arrest and treat accordingly. Send for patient’s notes or their usual doctor to gain more information as to a possible cause.

Hypothermia = warm slowly

Hypo/hyperkalaemia = correct electrolytes

Hypovolaemia = IV fluids or blood products

Tamponade = pericardiocentesis (drain fluid in pericardium, under xiphisternum up and leftwards)

Tension pneumothorax = needle into 2nd intercostal space, mid-clavicular line.

Thromboembolism = PE management, MI management

Toxins = administer antidotes

-Check for pulse if ECG rhythm compatible with a cardiac output (has the pulseless VT corrected, have they gone out of PEA?)

Reassess ECG rhythm after every 2 minutes of CPR.


Still in VF/VT = Repeat defibrillation. All shocks now at 360J.

Continue CPR.

Repeat cycles of Assess rhythm- Shock- CPR.


Resistant VF/VT (after 3 shocks) =

AMIODARONE 300mg IV/IO. A further 150mg may be given (after a total of 5 shocks), (followed by an infusion of 900mg over 24h).


-Give ADRENALINE 1mg IV/IO  every 3-5 minutes until return of spontaneous circulation is achieved.

Lidocaine is a possible alternative to amiodarone (1mg/kg IV, can repeat once, then give 2-4mg/min IV infusion)

-Seek expert advice from cardiologist.

If at any point, the patient switches from a shockable to non-shockable rhythm, or vice versa,  switch to the management for that rhythm.

Return of spontaneous circulation.

-ABCDE approach (Airways, Breathing, Circulation, Disability, Exposure)

-Aim for SpO2 of 94-98% and normal PaCO2 (4.7-6 kPa)

-12-lead ECG, CXR, U&Es, glucose, FBC, troponin, ABG.

-Treat precipitating cause

-Targeted temperature management/ therapeutic hypothermia (cool to core temperature of 32-34oc)

-Once the patient is stable, pat yourself on the back.

If acidosis: Good ventilation

Sodium bicarbonate IV only in arrest secondary to hyperkalaemia or tricyclic antidepressant overdose. Otherwise it can worse intracellular acidosis and precipitate arrhythmias. (E.g 50mL of 8.4% solution)




-Irreversible hypoxic brain damage



Asystole/ PEA have poorer prognosis than VF and pulseless VT.

Resuscitation is less successful in arrests that occur outside hospital.

Duration of inadequate effective cardiac output is associated with poor prognosis.

References: Cheese & Onion, UK Resuscitation Guidelines, my med school BSL/ASL training, Rapid Medicine

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