Should we intubate patients during cardiopulmonary resuscitation?BMJ 2017; 357 doi: https://doi.org/10.1136/bmj.j1772 (Published 18 April 2017) Cite this as: BMJ 2017;357:j1772
- Carl L Gwinnutt, emeritus consultant anaesthetist1
- 1Salford Royal NHS Foundation Trust, Salford M6 8HD, UK
- 2Resuscitation Council (UK), London WC1H 9HR, UK
As a trainee anaesthetist in the early 1980s, attendance at a “cardiac arrest” was frequent. My role was to intubate and ventilate the patient’s lungs with the highest possible concentration of oxygen. Other members of the team would insert a central line; attach an electrocardiogram monitor; give calcium, sodium bicarbonate, and intra-cardiac adrenaline; and defibrillate the patient, often in this sequence. Little attention was paid to chest compressions, a task usually delegated to the most junior person, often a student.
Over the years, most of these interventions have been abandoned as research has clarified which ones are associated with improved outcomes—namely good quality chest compressions and early defibrillation when the rhythm is ventricular fibrillation or ventricular tachycardia. So why are we still intubating patients’ tracheas as part of their management during cardiopulmonary resuscitation?
Perhaps the strongest reasons are the well known benefits of intubation during general anaesthesia—including effective ventilation in patients with poor pulmonary compliance, delivery of a high inspired oxygen concentration, the minimisation of gastric inflation, and protection against aspiration of gastric contents. During resuscitation, tracheal intubation allows ventilation to be continued without interrupting chest compressions.1
However, tracheal intubation also carries risks: multiple attempts, displacement of the tube, and unrecognised oesophageal intubation are relatively common, particularly in patients with out of hospital cardiac arrest (OHCA), where they have been reported to happen in up to 17% of patients.23 Furthermore, intubation can cause prolonged interruption to chest compressions4 which is associated with a poorer outcome. Skill retention is another problem, especially in the UK: paramedics in the London Ambulance Service perform an average of 3-4 intubations a year each, while those in the Hampshire division of South Central Ambulance Service average just one a year each.5
Does tracheal intubation during a cardiac arrest actually improve survival? The short answer is that we don’t yet know for certain. Research studies are mostly observational and findings are mixed. In one meta-analysis of observational studies, intubation during OHCA was associated with a significantly greater chance of return of spontaneous circulation, survival to hospital discharge, and neurologically intact survival than placement of a supraglottic airway.6 A secondary analysis of data from the PRIMED (Prehospital Resuscitation using an IMpedance valve and Early versus Delayed) trial reported similar findings—tracheal intubation was associated with more improved outcomes than insertion of a supraglottic airway during OHCA.7 Intubation was also associated with better survival than a supraglottic airway in the CARES study (Cardiac Arrest Registry to Enhance Survival), but, interestingly, the highest rate of survival was in those patients who received no airway intervention at all.8
In complete contrast, Andersen and colleagues have recently published the results of an observational analysis of data from the Get With The Guidelines resuscitation (GWTG-R) registry in the US. Using time dependent propensity score analysis, 43 314 patients who had an in-hospital cardiac arrest and were intubated during the first 15 minutes were paired with patients who, at each minute, had the same risk but were not intubated. Survival to discharge was significantly worse in the intubated group, as was the incidence of good neurological outcome in survivors. They conclude that “these findings do not support early intubation for adult in-hospital cardiac arrest.”9
It is important to recognise the limits of these observational analyses. Hidden confounders may cause bias and make it impossible to attribute cause and effect.10 In addition, Andersen and colleagues studied cardiac arrests in hospital, a situation very different to attempting intubation out of hospital.
So, at the moment we seem to be in a state of equipoise, but two trials currently underway may tip the balance one way or the other. Both compare tracheal intubation against placement of a supraglottic airway for initial management of OHCA. In the UK, the AIRWAYS-2 study aims to recruit 9000 patients to a cluster randomised design, with a primary outcome of neurologically intact survival to hospital discharge.11 In the US, the Pragmatic Airway Resuscitation Trial (PART) aims to cluster randomise 3000 adults with a primary outcome of 72 hour survival.12
The resuscitation world eagerly awaits the results of these trials, which are both expected to complete recruitment this year. Hopefully, they will provide some conclusive evidence to help us resolve current uncertainty about the benefits and harms of tracheal intubation during the resuscitation of OHCA patients. It is also hoped that this will encourage others to conduct similarly robust trials in in-hospital cardiac arrest.
The author would like to thank Jerry Nolan for his advice on the preparation of this editorial.
Competing interests: I have read and understood BMJ’s policy on declaration of interests and declare the following interests: I am president and a member of the executive committee of the Resuscitation Council (UK) (unpaid). I have provided advice on manikin design to Laerdal Medical (unpaid) and Innosonian Europe (unpaid).
Commissioned, not peer reviewed