2nd April 2024

Cardiorespiratory arrest

Introduction

The following section is based on the most recent 2021 Resuscitation Council UK guidelines. The adult advanced life support algorithm divides patients into shockable (ventricular fibrillation and pulseless ventricular tachycardia) versus non-shockable rhythms (PEA and asystole). 

Shockable rhythms have a better prognosis than non-shockable rhythms. Asystole has the worst survival prognosis. Less than a quarter of cardiac arrests are shockable both in and out of hospital. Pulseless electrical activity (PEA) is the most common rhythm identified in hospital. Return of spontaneous circulation (ROSC) is achieved in around half of those who are treated in hospital with a resuscitation team.

Assessment and management

The chain of survival stresses early recognition and calling for help, early commencement of CPR, early defibrillation and then post resuscitation care. The ratio of chest compressions to ventilation is 30:2. Compressions should be momentarily interrupted to assess the heart rhythm when connected to the monitor. After every two minute cycle, the rhythm should be reassessed and if a shockable rhythm is identified, defibrillation should be performed. This is repeated until ROSC is achieved. Adrenaline, an agonist of alpha and beta-adrenergic receptors, is used in all rhythms to increase arterial blood pressure and coronary perfusion.

Ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) are shockable rhythms. The energy level of the shock should initially be 150-200 joules biphasic. The 2nd shock should be 150-360 joules biphasic or 360 joules monophasic. A single precordial thump can be used in the first few seconds of a shockable rhythm. IV adrenaline (epinephrine) 1 mg (1 in 10000) and IV amiodarone 300mg should be given after the 3rd shock. Adrenaline should be continued every three to five minutes during alternative cycles of cardiopulmonary resuscitation (CPR). If there is refractory VF/VT, a further dose of amiodarone can be given. This should be followed by an infusion of 900mg over the next 24 hours. An alternative agent is lidocaine if amiodarone is unavailable. If the patient has a monitored cardiac arrest, typically in a cardiac unit or high dependency area, three successive shocks can be given immediately.

PEA and asystole are non-shockable rhythms (defibrillation is not recommended). IV adrenaline (epinephrine) 1 mg (1 in 10000) should be given immediately in this group and repeated every three to five minutes. If there is doubt as to whether rhythm is fine VF or asystole, defibrillation is not recommended.

The adult ALS algorithm:

Image Source: European Resuscitation Council (2021). cprguidelines.eu, Licensed under a creative commons licence. Available for free at: https://cprguidelines.eu/assets/guidelines/European-Resuscitation-Council-Guidelines-2021-Ad.pdf (Accessed: 12 March 2024).

The reversible causes of a cardiac arrest are listed below as the 4H’s and 4T’s:

Chest X-rays and bedside transthoracic echocardiogram can be useful in a cardiac arrest by diagnosing potentially treatable causes, including myocardial insufficiency, pericardial effusion and tamponade, pulmonary embolism, hypovolaemia and tension pneumothorax. Cardiac tamponade can be identified if there is early right ventricular diastolic collapse, a dilated IVC with loss of respiratory collapse and the swinging heart sign. When the ventricles are relaxed the intrapericardial pressure is higher than the RV pressure leading to collapse.

There are many special circumstances outlined in the guidance for CPR. Two notable areas include drowning and pulmonary embolism. Patients who have drowned should be lifted out of the water in a prone position to minimise the change in pressure. A head-out upright position leads to an immediate increase in cardiac output due to the surrounding water pressure being removed. This immediate change in pressure can lead to hypotension and circulatory collapse. The duration of submersion is the strongest predictor in outcome. Thrombolytic agents can be used in patients who have arrested secondary to a massive unstable pulmonary embolism. It is recommended that CPR should continue for at least 60 to 90 minutes in view of previous cases responding positively to extended periods of resuscitation.

Post resuscitation care

Post resuscitation care aims to optimise outcomes after the patient gains ROSC. This includes maintaining a mean arterial blood pressure of > 65mmHg. If seizure activity was detected the preferred agents include keppra (levetiracetam) or sodium valproate.  Targeted cooling in the range of 32 – 36 °C for the first 24 hours is neuroprotective. Fever should actively be prevented for at least 72 hours and a target blood glucose should be between 7.8-10 mmol/l.

Waveform capnography

Carbon dioxide (CO₂) is a byproduct of metabolism and is expired during respiration. It can be measured using capnography to monitor the concentration of CO₂ in expired gas. The highest concentration is at the end of expiration, termed end-tidal CO₂. The end-tidal CO₂ is the partial pressure of CO₂ at the end of every exhaled breath and reflects cardiac output and pulmonary blood flow. Waveform capnography enables continuous end-tidal CO₂ monitoring during CPR. It can be used to ensure that the endotracheal tube is in the correct position. It is a reliable method to identify ROSC when the end tidal volume significantly rises. During CPR, it can monitor the ventilation rate and avoid hyperventilation. As well as this, it can monitor the quality of chest compressions as end-tidal CO₂ values are associated with compression depth and ventilation rate.

Image Source: Wikimedia Commons (2024). Capnography, Licensed under a creative commons licence. Available for free at: https://en.wikipedia.org/wiki/Capnography (Accessed: 12 March 2024).

References

• Resuscitation Council UK. 2021 Resuscitation Guidelines. Available from https://www.resus.org.uk/library/2021- resuscitation-guidelines
• Tidy, C. (2023) Cardiopulmonary arrest in adults: Doctor, Patient.info. Edited by P. Vincent. Available at: https://patient.info/doctor/adult-cardiopulmonary-arrest
• Dee R, Smith M, Rajendran K. International Liaison Committee on Resuscitation Basic Life Support Task Force Collaborators. The effect of alternative methods of cardiopulmonary resuscitation – Cough CPR, percussion pacing or precordial thump – on outcomes following cardiac arrest. A systematic review. Resuscitation. 2021 May;162:73-81. doi: 10.1016/j.resuscitation.2021.01.027. Epub 2021 Feb 11. PMID: 33582257.
• Wu JP, Gu DY et al. Good neurological recovery after rescue thrombolysis of presumed pulmonary embolism despite prior 100 minutes CPR. J Thorac Dis. 2014 Dec;6(12):E289-93. doi: 10.3978/j.issn.2072-1439.2014.12.23. PMID: 25590010; PMCID: PMC4283306.
• European Resuscitation Council Guidelines 2021: Adult advanced life support. Resuscitation. 2021 Apr:161:115-151.