Cardiac Arrest

Question 1

4 Key stages of BLS

Answer 1

1. Check for safety
2. Shout for help
3. Check airway (clear visible obstruction) – open airway with head tilt, chin lift or jaw thrust if cervical spine injury is suspected.
4. Check breathing (rise and fall of chest, breath sounds) & circulation (carotid pulse) simultaneously for maximum 10s
   (Agonal gasps occur in up to 40% of cardiac arrest cases)

If cardiac arrest confirmed: emergency call (999 or 2222 in hospital) and CPR commenced.

Question 2

Outline CPR (for cardiac arrest)

Answer 2

30 compressions : 2 breaths

5-6cm depth, 100-120 per minute

If definitive airway in place (e.g. endotracheal tube), continuous chest compressions should be given (placement of a definitive airway by trained person desirable, as this minimises interruptions to chest compressions). If there is no trained person, the risk of misplacement means that interrupted CPR at ratio of 30:2 should be given.

CPR should continue whilst defibrillator is obtained and/or attached. Once prepared: analyse cardiac rhythm – 4 rhythms identifiable when in arrest. Interruptions to CPR should be minimised (ideally <5s) & compressions should resume as soon as rhythm is identified.

Question 3

What are the 4 rhythms identifiable when in arrest?

Answer 3

Ventricular Fibrillation

Pulseless Ventricular Tachycardia (VT)

Asytole

Pulseless Electrical Activity (PEA)
or electromechanical dissociation (AMD) arrest – any pulseless rhythm that would ordinarily be associated with a cardiac output (except VT).

VF + VT are the initial rhythm in 25% of cases (25% of PEA/asystole arrests will convert to VT/VF at some point in resuscitation).

Question 4

Which 2 rhythms are shockable?

Which 2 are non-shockable?

Answer 4

VF & VT = shockable.

Asystole & PEA = non-shockable.

Question 5

If shockable rhythm identified during CPR - how to manage?

Answer 5

Once identified, shock should be administered ASAP - restart chest compressions while defibrillator is being prepared for administration of shock

When ready to be charged, all bystanders (except person performing compressions) should be asked to stand clear + oxygen should be removed.

Once charged, person operating defibrillator should instruct person performing chest compressions to stand clear so that shock can be administered

Compressions should resume immediately + continue for 2 mins. Person administering compressions should swap frequently (prevent ineffective compressions due to fatigue).

Check rhythm every 2 minutes, and if indicated, administer shock with above method. If rhythm has changed: assess for ROSC and if present, commence post arrest care. If no ROSC + rhythm now non-shockable, switch to the non-shockable side of the algorithm.

After the 3rd shock:
o IV adrenaline 1mg
o Single dose IV amiodarone 300mg
o Repeat adrenaline every 3-5 mins (every other CPR cycle)
o DO NOT interrupt chest compressions to deliver the drugs
o If IV access cannot be obtained, interosseous route can be used to administer drugs (interosseous access should only be obtained by trained team members)

Most hospitals use biphasic defibrillators at 150 Joules with self-adhesive pads, however, specifications differ between brands of machine.

Question 6

If non-shockable rhythm identified during CPR - how to manage?

Answer 6

If initial rhythm is asystole or PEA, administer 2 mins CPR before further rhythm check.

o Give IV adrenaline 1mg ASAP after non-shockable rhythm identified
o Give IV adrenaline 1mg every 3-5 mins thereafter

After 2 minutes of CPR, check rhythm again. If ROSC achieved, commence post-resuscitation care. If rhythm changes to VF / VT, follow the shockable rhythm algorithm EXCEPT that once adrenaline has been given it should still be given every 3-5 mins (i.e. you do not need to wait until after 3 shocks).

Question 7

What are the reversible causes of cardiac arrest?

Answer 7

The 4 H’s:
• Hypoxia
• Hypovolaemia
• Hypothermia
• Hypo / Hyperkalaemia

The 4 T’s:
• Thromboembolism
• Tamponade
• Toxins
• Tension pneumothorax

Question 8

If hypoxia is cause - mgmt?

Answer 8

Hypoxia is a common cause: ensuring airway open by using adjunct such as oropharyngeal (guedel) airway, or a more definitive airway e.g. Laryngeal Mask Airway or endotracheal tube whilst giving high flow oxygen & ventilating the patient will treat hypoxia.

Question 9

If hypovolaemia is cause - mgmt?

Answer 9

Hypovolaemia caused by blood or fluid loss: trauma common cause of blood loss but may also be hidden e.g. upper GI bleeding. Conditions such as diarrhoea, vomiting & sepsis can cause fluid loss. Treat with rapid fluid replacement to increase circulating blood volume & if large volume blood loss suspected, give O negative transfusion. Hb levels can be falsely reassuring in acute bleeds, as red cell concentration remains constant, therefore decision to give a transfusion should be guided by a thorough examination of the patient. If IV access not possible, consider the interosseous route for the administration of compatible fluids and/or drugs.

Question 10

If Hypo / Hyperkalaemia is cause - mgmt?

Answer 10

Hyperkalaemia & hypokalaemia usually diagnosed from electrolyte measurements on ABG analysers or on basis of recently obtained venous samples.

If serum K⁺ low: IV potassium replacement.

If serum K⁺ high: insulin & glucose infused (drives potassium into cells). IV calcium (e.g. calcium chloride) should also be given to stabilise the myocardium.

Sodium bicarbonate occasionally required (but calcium & sodium bicarbonate must not be given by same access!)

May need to correct other disturbances (e.g. Mg²⁺, Ca²⁺) if known to be deficient

Magnesium sulphate can be given for persistent VT or VF where hypomagnesaemia suspected (e.g. patients with hypokalaemia secondary to diuretics).

Question 11

If hypothermia is cause - mgmt?

Answer 11

Sudden Onset Hypothermia e.g. drowning, can cause cardiac arrest. Hypothermia is protective against effects of ischaemia, therefore resuscitation should continue until patient is warm. Dry patients ASAP after retrieval from cold water, and cover extremities to help warming. Infuse warm fluids to help warming and monitor core temperature.

Resuscitation Council UK guidelines state for ‘resuscitation after water rescue’:
o Core temp <30°C: limit defibrillation attempts to 3 (delivered at maximum defibrillator output) and withhold IV drugs until the core body temperature increases to >30°C. Withhold adrenaline & amiodarone until the patient has warmed to >30°C.
o Core temp 30-35°C: double intervals between drug doses compared to normothermia intervals
o Core temp >35°C: use standard drug protocol

Prehospital warming = limited effectiveness in unconscious patients, but heating blankets and warm ambient environment should be considered.

Question 12

If tension pnuemothorax is cause - diagnosis and mgmt?

Answer 12

Can occur spontaneously or after trauma (including medical procedures such as central line placement and pleural fluid aspiration). Typically, patient will complain of difficulty breathing prior to collapse. Examination of chest: hyperresonant percussion note on affected side, and chest expansion may decrease on affected side.

Treatment of tension pneumothorax is immediate decompression:

1. Large bore cannula 2nd intercostal space in mid-clav line (affected side)
2. ‘Hiss’ of air should be audible when cannula placed
3. Secure cannula + insert chest drain at earliest opportunity (in an arrest scenario, this will be after ROSC)
4. Whilst CPR ongoing, take care that cannula not knocked out or kinked – may need to insert second cannula if this occurs.

Question 13

If thromboembolism is cause - diagnosis and mgmt?

Answer 13

Pulmonary embolism main thromboembolic cause of cardiac arrest - preceding history may point to this (chest pain, SOB, recent immobility, signs of DVT).

Echocardiogram can be used at cardiac arrest to assist in diagnosis of thromboembolic disease but should only be undertaken by trained operators.

o Ongoing CPR not a contraindication to thrombolysis, but resuscitation may need to continue for up to 90 minutes post thrombolysis (thrombolysis has successfully treated massive PE causing cardiac arrest)

o Coronary thrombosis also common cause of cardiac arrest – if myocardial ischaemia is thought highly likely to be the cause of the arrest, it is possible to undertake coronary angiography and Primary Coronary Intervention (PCI) whilst compressions are ongoing, requires careful consideration of patient’s prognosis and access to a mechanical chest compression device or an extracorporeal circuit to maintain the circulation whilst the procedure is undertaken.

Question 14

If toxin is cause - diagnosis and mgmt?

Answer 14

often supportive tx – in hospital setting examine the patient’s drug chart for recent medication administration as possible causes of cardiac arrest.

Anaphylaxis (allergic reaction to drug): if possible give IM adrenaline 500mcg and an antihistamine and corticosteroid pre-arrest (note: Epipen contains 300mcg of adrenaline in a pre-filled syringe). If cardiac arrest occurs, give IV adrenaline 1mg as discussed previously.

Opioids (e.g. morphine): give naloxone (opioid receptor antagonist) – short half-life relative to opioids therefore close monitoring and repeated doses usually required

Tricyclic antidepressants (TCAs): overdose one of few circumstances in which sodium bicarbonate is recommended for treatment of acidosis

Benzodiazepines: flumazenil is a benzodiazepine antagonist – use can cause seizures in patients dependent on benzodiazepines and therefore routine administration not recommended in cases of drug overdose

Question 15

If tamponade is cause - diagnosis and mgmt?

Answer 15

Tamponade: occurs when fluid in pericardial space compresses the heart – can occur following a penetrating injury to the chest, cardiac surgery, MI or as a result of pericarditis. Commonly diagnosed by echocardiogram and is treated by pericardiocentesis.

If suspect cardiac tamponade to be cause of cardiac arrest, seek specialist assistance.

Question 16

Cardiac arrest in pregnancy?

Answer 16

Uncommon but difficult to manage

• Increased CO, blood volume and oxygen consumption in pregnancy. In later stages of pregnancy, gravid uterus can compress abdominal vessels causing reduced cardiac output

Seek urgent obstetric input in any life-threatening illness in a pregnant woman, if gestational age is >23 weeks, will need neonatology input

When managing arrest in later stages of pregnancy, manually displace uterus to the left (relieves pressure of the gravid uterus on the caval vessels, improves venous return and makes cardiac compressions more effective) – add left lateral tilt only if this is feasible.

May need to place hand position for chest compressions higher than normal (2-3cm) for patients with advanced pregnancy (>28 weeks) to allow for displacement of the contents of the chest by the uterus.

Consider emergency caesarean if initial resuscitation attempts are unsuccessful – decision should be made within 5 minutes of cardiac arrest – this can increase the chance of ROSC in the mother and also the chance of the infant surviving.

Question 17

How to manage arrest following cardiac catheterisation & surgery ?

Answer 17

Arrest following cardiac catheterisation or surgery generally follows the standard guidelines, however, if VF or VT then a series of three stacked DC shocks may be more successful in achieving ROSC than a single shock and therefore may be given in this circumstance.

Question 18

What is Post Cardiac Arrest Syndrome

Answer 18

o Brain injury caused by hypoxia
o Myocardial dysfunction
o Systemic response to ischaemia and reperfusion
o Potential ongoing effects of initial cause of cardiac arrest

Can lead to multiorgan failure. When ROSC achieved, continue management to prevent further cardiac arrest and to maximise likelihood of a good recovery.

Question 19

How to manage Post Cardiac Arrest Syndrome?

Answer 19

Titrate inspired oxygen to aim for saturations of 94-98% (not 100%) and normal CO₂ levels. Ongoing resp failure (hypoxia + / - hypercapnia) increases the likelihood of 2nd arrest and can increase ischaemic end-organ damage. However, also evidence that hyperoxia may be associated with a poor outcome.

Commence immediate temperature management to achieve a core temperature MAX 36°C. Passive cooling is appropriate; do not infuse cold IV fluids for cooling alone. This is not therapeutic hypothermia.. ?

If the cardiac arrest was caused by myocardial ischaemia, Percutaneous Coronary Intervention (PCI) may be indicated. PCI can be carried out in combination with therapeutic hypothermia where required.