Out-of-Hospital Cardiac Arrest data linkage project: 2017-2018 results

Discussion

The number of patients with OHCA that had resuscitation attempted in the community during 2017/18 was stable at 3,484 (compared to 3,455 in 2016/17). The proportion of incidents where data linkage is completed continues to improve - being possible for 88.7% of OHCA cases in 2017/18. This is likely to represent continued improvement in data recording by the Scottish Ambulance Service and improves the quality of information included in this report.

The key demographic descriptors of people having OHCA remains the same as in previous years. There were no changes in the mean age of OHCA patients (66 years) or the male vs female split (64% vs 36%). People living in the most deprived quintile (SIMD1) continue to have around twice as many OHCA as those in the least deprived (SIMD5). Arrests in SIMD1 areas happen at a younger age (8 years younger on average) and are more likely to be fatal than those occurring in SIMD5. People in the least deprived quintile (SIMD5) are more likely to receive bystander CPR (60% in SIMD5 vs 56% in SIMD1) and to have an initial cardiac rhythm treatable with defibrillation (31.7% SIMD5 vs 25.5% SIMD1).

Significantly, bystander CPR rates have increased to 55.5% in 2017/18 compared with 49.9% in 2016/17. This is likely to be due several factors. At the time of writing the Save a Life for Scotland partnership have equipped more than 300,000 people in Scotland with CPR skills, and coordinated a range of social marketing initiatives^[5]. Additionally, the Scottish Ambulance Service have implemented a range of improvements to enhance telephone support for bystander CPR.

Overall there has been an increase in the number of patients who had a pulse on arrival at hospital than in previous years with 'Return of Spontaneous Circulation' (ROSC) up to 23.3% in 2017/18 from 20.2% in 2016/17. However there was no significant change in 30-day survival. The reason for this is unclear, though the relationship between ROSC and 30-day survival is affected by a range of factors including pre-hospital resuscitation (e.g. the use of epinephrine) and in-hospital post-resuscitation care.

As we have pointed out in previous reports, the proportion of OHCA calls where resuscitation was attempted is variable^[2]. The threshold for attempting resuscitation has been found to vary significantly between ambulance services, which is one of the factors making the reliance on worked arrests as the denominator for calculating survival problematic^[6].

As the age and size of the population of Scotland is increasing the Scottish Ambulance Service is frequently called to deal with patients in the terminal stages of illness in their own homes. This patient group pose significant challenges in anticipatory care planning. Initiatives such as the Chief Medical Officer's 'Realistic Medicine', Health Improvement Scotland's 'What Matters to You' and the Scottish Government's '2020 Healthcare Strategy' set a priority of providing the right care to the patient in the right setting. With this in mind, the Scottish Ambulance Service is engaging with partners to develop safeguards and processes aimed at ensuring that these individuals and their carers are not exposed to inappropriate and distressing resuscitation attempts in the event of a cardiac arrest.

In response to this issue, the Global Resuscitation Alliance (an international body focused on implementation of the chain of survival in OHCA^[7]) have suggested that reporting number of survivors per million of the population may be a better way to structure outcome data than calculating the proportion of 'worked arrests'^[8]

This work continues to update our previous report on the initial results of the Scottish OHCA data linkage project. Our figures summarise the progress of all of the Strategy partner organisations against delivery of the OHCA Strategy^[1]. The data presented here show that the complex system of care summarised in the Chain of Survival has continued to improve in 2017/18. We have increased bystander CPR rates, a higher proportion of patients regaining a pulse after initial prehospital resuscitation and better quality OHCA data. Although the number of individuals surviving to 30 days after OHCA has remained stable compared to 2016/17, we would expect this crucial outcome figure to increase going forward, as a result of continued successful system optimisation.

Further updates from the data linkage project will be published during the course of the strategy.