Biomedical subjects
L H Soo
Publications and source records attributed to L H Soo.
Pathological features of witnessed out-of-hospital cardiac arrest presenting with ventricular fibrillation.
OBJECTIVES: To determine which characteristic pathological features are predictive of the presenting rhythm and survival in victims of community cardiac arrest. DESIGN: Case-controlled retrospective autopsy study. SETTING: County of Nottinghamshire with a total population of 993 914 and an area of 2183 square kilometers. SUBJECTS: Between January 1, 1991 and December 31, 1994, 1535 witnessed cardiac arrests attended by the Nottinghamshire Ambulance Service, of which 1083 had an autopsy performed. RESULTS: Ischaemic heart disease accounted for 72.3% of cases with a further 3.6% of deaths from other cardiac causes and the remainder from non-cardiac causes. Old healed myocardial infarction was present in 39.4%, and visible fresh occlusive thrombus was found in 23.8% of cases overall. Logistic regression analysis of deaths from cardiac causes revealed that younger age (odds ratio of 0.98 (95% CI 0.97-0.99)), two vessel coronary artery disease (odds ratio of 1.65 (95% CI 1.08-2.52)) and heart weight greater than 500 grams (odds ratio of 1.56 (95% CI 1.12-2.17)) were found to be independent predictors of developing ventricular fibrillation compared to other rhythms of arrest. Being male, visible occlusive thrombus and having survived a previous myocardial infarction were found not to be independent variables. There were no outstanding pathological features in the 31 patients who survived to hospital admission and subsequently died, compared with non-survivors who were considered to have died from a cardiac cause. CONCLUSIONS: Among those who had a witnessed out-of-hospital cardiac arrest from a cardiac cause, increasing heart weight (the most likely cause of which is left ventricular hypertrophy), younger age and two vessel coronary artery disease appear to be much more important pathological features in the development of ventricular fibrillation than a previous myocardial infarction and fresh visible occlusive thrombus.
Circadian variation in witnessed out of hospital cardiac arrest.
OBJECTIVES: To examine the effect on circadian variation of out of hospital cardiac arrest according to the underlying aetiology and presenting rhythm of arrest, and to explore strategies that might help to improve survival outcome using circadian variation. DESIGN: Population based retrospective study. SETTING: County of Nottinghamshire with a total population of 993 914 and an area of 2183 km(2). SUBJECTS: Between 1 January 1991 and 3 December 1994, all witnessed cardiac arrests attended by the Nottinghamshire Ambulance Service, of which 1196 patients had a cardiac cause for their arrest (ICD, 9th revision, codes 390-414 and 420-429) and 339 had a non-cardiac cause. RESULTS: The circadian variation of the cardiac cases was not significantly different from that of non-cardiac cases (p = 0.587), even when adjusted for age, sex, or presenting rhythm of arrest. For cardiac cases, the circadian variation of those who presented with ventricular fibrillation was significantly different from those presenting with a rhythm other than ventricular fibrillation (p = 0.005), but was similar to the circadian variation of bystander cardiopulmonary resuscitation (p = 0.306) and survivors (p = 0.542). Ambulance response time was also found to have a circadian variation. CONCLUSIONS: There is a common circadian variation of out of hospital cardiac arrest, irrespective of underlying aetiology, where the presenting rhythm is other than ventricular fibrillation. This is different from the circadian variation of cases of cardiac aetiology presenting with ventricular fibrillation. The circadian variation of ventricular fibrillation, and consequently survival, may be affected by the availability of bystander cardiopulmonary resuscitation and the speed of ambulance response.
Influence of ambulance crew's length of experience on the outcome of out-of-hospital cardiac arrest.
AIMS: To investigate whether an ambulance crew's length of experience affected the outcome of out-of-hospital cardiac arrest. METHODS AND RESULTS: This was a population-based, retrospective observational study of attempted resuscitations in 1547 consecutive arrests of cardiac aetiology by Nottinghamshire Emergency Ambulance Service crew. One thousand and seventy-one patients were managed by either a paramedic or a technician crew without assistance from other trained individuals at the scene of arrest. Overall, the chances of a patient surviving to be discharged from hospital alive did not appear to be affected by the paramedic's length of experience (among survivors, 18 months experience vs non-survivors 16 months experience, P = 0.347) but there appears to be a trend in the effect of a technician's length of experience on survival (among survivors, 60 months experience vs non-survivors 28 months experience, P = 0.075). However, when a technician had 4 years of experience or more and a paramedic 1 year's experience, survival rates did improve. Logistic regression analysis, adjusted for factors known to influence outcome, revealed that chances of survival increased once technicians had over 4 years of experience after qualification (odds ratio 2.71, 95% CI 1.17 to 6.32, P = 0.02) and paramedics after just 1 year of experience (odds ratio 2.68, 95% CI 1.05 to 6.82, P = 0.04). CONCLUSIONS: Survival from out-of-hospital cardiac arrest varies with the type of ambulance crew and length of experience after qualification. Experience in the field seems important as paramedics achieve better survival rates after just 1 year's experience, while technicians need to have more than 4 years' experience to improve survival.
Resuscitation from out-of-hospital cardiac arrest: is survival dependent on who is available at the scene?
OBJECTIVE: To determine whether survival from out-of-hospital cardiac arrest is influenced by the on-scene availability of different grades of ambulance personnel and other health professionals. DESIGN: Population based, retrospective, observational study. SETTING: County of Nottinghamshire with a population of one million. SUBJECTS: All 2094 patients who had resuscitation attempted by Nottinghamshire Ambulance Service crew from 1991 to 1994; study of 1547 patients whose arrest were of cardiac aetiology. MAIN OUTCOME MEASURES: Survival to hospital admission and survival to hospital discharge. RESULTS: Overall survival from out-of-hospital cardiac arrest remains poor: 221 patients (14.3%) survived to reach hospital alive and only 94 (6.1%) survived to be discharged from hospital. Multivariate logistic regression analysis showed that the chances of those resuscitated by technician crew reaching hospital alive were poor but were greater when paramedic crew were either called to assist technicians or dealt with the arrest themselves (odds ratio 6.9 (95% confidence interval 3.92 to 26.61)). Compared to technician crew, survival to hospital discharge was only significantly improved with paramedic crew (3.55 (1.62 to 7.79)) and further improved when paramedics were assisted by either a health professional (9.91 (3.12 to 26.61)) or a medical practitioner (20.88 (6.72 to 64.94)). CONCLUSIONS: Survival from out-of-hospital cardiac arrest remains poor despite attendance at the scene of the arrest by ambulance crew and other health professionals. Patients resuscitated by a paramedic from out-of-hospital cardiac arrest caused by cardiac disease were more likely to survive to hospital discharge than when resuscitation was provided by an ambulance technician. Resuscitation by a paramedic assisted by a medical practitioner offers a patient the best chances of surviving the event.