In this blog for paramedics and other prehospital emergency medical providers, paramedic Scott Munro looks at new Cochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. More on approaches to cardiopulmonary resuscitation for out-of-hospital cardiac arrest
It’s half-way through a busy night shift when you get a call come in for a 64-year-old male that’s collapsed at home. En route, an update comes through. He’s not breathing. When you arrive, you scramble through the front door with your crew mate and kit and you see the patient lying on the floor of the cramped bedroom with a family member doing cardiopulmonary resuscitation (CPR). There’s a mobile phone on the floor on loud speaker and you can hear the call taker on the other end of the line, calmly giving advice to the family member, as they do their best to save their loved one. The family member is being instructed to give continuous chest compressions, to put their hands in the middle of their chest and press hard and fast. But no ventilations. As you and your crew mate take over care of the patient, is it best that you carry on continuous chest compressions or should you be doing compressions and ventilations?
Surviving cardiac arrest out of hospital
If you have a cardiac arrest outside of hospital, your chances of surviving aren’t fantastic. In the UK cardiopulmonary resuscitation (CPR) is attempted by the emergency medical services on 30,000 people every year, with survival rates as little as 7-8%. The chain of survival is an illustration that emphasises the important links involved in giving people the best chances of having a good outcome.
Early recognition and call for help; early CPR; early defibrillation; and post-resuscitation care.
Notice the emphasis on early?
If someone provides CPR very shortly after a patient goes into cardiac arrest, their chances of survival treble. However, at the moment only 30-40% of out-of-hospital cardiac arrests receive any bystander CPR before the ambulance service arrives.
Compressions and ventilation?
There are many questions and uncertainties surrounding the current care provided during out-of-hospital cardiac arrest. The International Liaison Committee on Resuscitation (ILCOR) published an international Consensus on Science and Treatment Recommendations in 2015, which is used by the Resuscitation Council UK to inform their guidelines on out of hospital resuscitation. Only 1% of these recommendations are based on high-level evidence.
One question raised around resuscitation is whether chest compressions should be provided with pauses for rescue breaths, or whether they should be provided continuously, without interruptions.
Chest compressions are provided to try and pump blood round circulatory system and keep up a blood supply to cardiac muscle and brain, while ventilations attempt to oxygenate the blood. Pauses in chest compressions have been shown to have associations with worse survival due to a reduction of coronary perfusion pressure.
Current guidelines in the UK from the Resuscitation Council advise that bystanders are given advice over the phone from a 999 call taker to provide continuous chest compressions, unless trained and competent in combining CPR with mouth-to-mouth, while emergency medical services (EMS) are advised to provide compressions and ventilations in a ratio of 30:2. If the patient is intubated or has a supraglottic device put in place, ventilations can then be provided at a rate of 10 per minute, without the need for a pause in chest compressions (given asynchronously).
What does the evidence say?
Zhane et al recently published a Cochrane review comparing continuous chest compressions versus interrupted chest compression for cardiopulmonary resuscitation for non-asphyxial out-of-hospital cardiac arrest. The review was really asking the same question for two different groups. What should untrained bystanders do? And what should EMS professionals do?
Asking these questions seems appropriate, because CPR provided by these two groups will in all likelihood be different. The bystander group will be providing CPR with advice over the telephone and little or no previous experience, while the EMS group will have received professional training and equipment and have more experience in providing CPR.
Three randomised controlled trials and one cross-over cluster A trial in which the people taking part are randomly divided into groups. A group (the intervention group) is given the intervention being tested (for example a drug, surgery, or exercise) and compared with a group which does not receive the intervention (the control group). More were found by the review authors, with a large sample of 26,742 participants included in the analysis.
The primary outcomes the authors were interested in were survival to hospital discharge and survival to hospital admission. Neurological outcomes were studied, but only as secondary outcomes.
The review only included patients that died of a presumed cardiac causes. Patients that died from drug overdoses, trauma, alcohol intoxication or asphyxia (choking, drowning, lack of oxygen) were excluded.
What did they find?
The results showed that untrained bystander CPR had better outcomes when given telephone advice from EMS services to perform continuous CPR, rather than interrupted CPR with rescue breaths. In fact, an additional 25 per 1000 would survive to hospital discharge if given continuous chest compressions by bystanders. This is high quality evidence, so we can be confident that further research is very unlikely to change the estimate of effect.
For trained EMS professionals, results showed that there was probably no benefit in survival to hospital discharge when performing continuous CPR versus CPR interrupted with rescue breaths. This evidence is moderate quality and it is possible that there is little or no difference between the two approaches. There were slightly lower rates of survival to admission or discharge following continuous chest compression, but little or no difference in neurological outcome or adverse effects.
So why the difference between the two groups? The authors suggest that the difference may be due to the quality of chest compressions delivered by bystanders, compared with EMS personnel.
There are questions still to be answered. The review authors highlight the need for research into adverse effects, longer term neurological outcomes and quality of life, as well as the influence of automated external defibrillator availability and use, and whether continuous chest compression CPR is appropriate for paediatric cardiac arrest.
You can connect with Scott @ScottFSMunro on Twitter, where he runs a prehospital journal club #PHJC
Scott Munro has nothing to disclose. Views are Scott’s own.
References may be found here.