Heartstart Scotland: Statistical Analysis of Survival From Out-of-Hospital Cardiac Arrest

Dalziel, Kirsty (1994) Heartstart Scotland: Statistical Analysis of Survival From Out-of-Hospital Cardiac Arrest. MSc(R) thesis, University of Glasgow.

Abstract

In 1988 the Scottish Ambulance Service set out to equip all its 395 accident and emergency ambulances with Laerdal semi-automatic defibrillators. Semi-automatic defibrillators are devices that can administer an electric shock to a patient in cardiac arrest and shock the patient's heart back into a viable rhythm. The Heartstart Scotland study was set up to audit the defibrillation program, in particular the resuscitation success rate. It became apparent quite early on that the program was extremely successful and in the first year of the study the ambulance service successfully resuscitated 12.5% of all patients who were defibrillated. In Chapter 1, I review the organisation of the Scottish Ambulance Service, the origins of the Heartstart Scotland study and the history of pre-hospital care from 1966 to date. It was in 1966 that Geddes introduced the concept of out-of-hospital defibrillation. Chapter 2 concentrates on the data collection and storage, and methods of patient follow-up. Data are collected from eight ambulance areas across Scotland's 76.000 km2 and there are inevitably problems with data quality and collection. These problems were more acute in the early stages of the study when there was little consideration to questionnaire design and accuracy of ambulance crew responses. Chapter 3 describes the Heartstart population in detail and touches on what factors during a patient's resuscitation attempt may influence their ultimate survival. It should be obvious to the reader that a cardiac arrest witnessed by a bystander is more likely to have a successful outcome than one that is not. Other factors, such as the effect of gender on outcome are less obvious. It is important that the reader fully understands the sequence of events that are being analysed here. Chapter 4 is an overview of the whole system from patient collapse to hospital discharge. In 1991 a strict set of guidelines were published for reporting out-of- hospital cardiac arrest. This style of reporting is known as the 'Utstein style'. In Chapter 5, factors influencing initial survival are identified using stepwise logistic regression techniques. Initial survival is defined as survival to hospital discharge. There are three stages leading to successful discharge. These are: presence of a shockable rhythm following collapse; admission to a hospital ward; discharge from hospital alive. Different factors are shown to be significant at each stage. Although there are many similar studies to Heartstart across the world, little research has been carried out into the long-term survival of patients following out-of-hospital cardiac arrest. Chapter 6 examines the characteristics of a group of 924 cardiac arrest patients who were admitted to a hospital ward. Long-term survival is defined as the duration of the patient's life following discharge from hospital. Product limit estimates of survival are presented for the 458 patients discharged alive to determine the univariate impact on survival of factors such as age, cause of arrest and drug therapy on discharge. Cox proportional hazards models were then applied to determine the multivariate effect on survival of the various factors. Patients were stratified according to underlying cause of arrest (Myocardial infarction (MI), ischaemia/non Q wave MI or primary ventricular fibrillation). Chapter 7 is a general summary of this type of research looking at problems with result presentation and interpretation. A review of current and future research interests is presented, followed by my interpretation of the most interesting results arising from this thesis.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Adviser: Stuart Cobbs
• Keywords: Biostatistics
• Date of Award: 1994
• Depositing User: Enlighten Team
• Unique ID: glathesis:1994-75695
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 18:55
• Last Modified: 19 Nov 2019 18:55
• URI: https://theses.gla.ac.uk/id/eprint/75695