Validation of the new Vancouver Chest Pain Rule in Asian chest pain patients presenting at the emergency department.

OBJECTIVES: The new Vancouver Chest Pain (VCP) Rule recommends early discharge for chest pain patients who are at low risk of developing acute coronary syndrome (ACS), and thus can be discharged within 2 hours of arrival at the emergency department (ED). This study aimed to assess the performance of the new VCP Rule for Asian patients presenting with chest pain at the ED. METHODS: This prospective cohort study involved patients attended to at the ED of a large urban centre. Patients of at least 25 years old, presenting with stable chest pain and a non-diagnostic ECG, and with no history of active coronary artery disease were included in the study. The main outcome measures were cardiac events, angioplasty, or coronary artery bypass within 30 days of enrolment. RESULTS: The study included 1690 patients from 27 August 2000 to 1 May 2002, with 661 patients fulfilling the VCP criteria. Of those for early discharge, 24 had cardiac events and 13 had angioplasty or bypass at 30 days, compared to 91 and 41, respectively, for those unsuitable for discharge. This gave the rule a sensitivity of 78.1% for cardiac events, including angioplasty and bypass. Specificity was 41.0%, and negative predictive value (NPV) was 94.4%. CONCLUSION: We found the new VCP Rule to have moderate sensitivity and poor specificity for adverse cardiac events in our population. With an NPV of less than 100%, this means that a small proportion of patients sent home with early discharge would still have adverse cardiac events.

Reducing ambulance response times using geospatial-time analysis of ambulance deployment.

OBJECTIVES: This study aimed to determine if a deployment strategy based on geospatial-time analysis is able to reduce ambulance response times for out-of-hospital cardiac arrests (OOHCA) in an urban emergency medical services (EMS) system. METHODS: An observational prospective study examining geographic locations of all OOHCA in Singapore was conducted. Locations of cardiac arrests were spot-mapped using a geographic information system (GIS). A progressive strategy of satellite ambulance deployment was implemented, increasing ambulance bases from 17 to 32 locations. Variation in ambulance deployment according to demand, based on time of day, was also implemented. The total number of ambulances and crews remained constant over the study period. The main outcome measure was ambulance response times. RESULTS: From October 1, 2001, to October 14, 2004, a total of 2,428 OOHCA patients were enrolled into the study. Mean ± SD age for arrests was 60.6 ± 19.3 years with 68.0% male. The overall return of spontaneous circulation (ROSC) rate was 17.2% and survival to discharge rate was 1.6%. Response time decreased significantly as the number of fire stations/fire posts increased (Pearson χ(2) = 108.70, df = 48, p < 0.001). Response times for OOHCA decreased from a monthly median of 10.1 minutes at the beginning to 7.1 minutes at the end of the study. Similarly, the proportion of cases with response times < 8 minutes increased from 22.3% to 47.3% and < 11 minutes from 57.6% to 77.5% at the end of the study. CONCLUSIONS: A simple, relatively low-cost ambulance deployment strategy was associated with significantly reduced response times for OOHCA. Geospatial-time analysis can be a useful tool for EMS providers.

Comparison of chest compression only and standard cardiopulmonary resuscitation for out-of-hospital cardiac arrest in Singapore.

OBJECTIVE: Chest compression only cardiopulmonary resuscitation (CC-CPR) without ventilation has been proposed as an alternative to standard cardiopulmonary resuscitation (CPR) for bystanders. However, there has been controversy regarding the relative effectiveness of both of these techniques. We aim to compare the outcomes of cardiac arrest patients in the cardiac arrest and resuscitation epidemiology study who either received CC-CPR, standard CPR or no bystander CPR. METHODS: This prospective cohort study involved all out-of-hospital cardiac arrest (OHCA) patients attended to by emergency medical service (EMS) providers in a large urban centre. The data analyses were conducted secondarily on these collected data. The technique of bystander CPR was reported by paramedics who arrived at the scene. RESULTS: From 1 October 2001 to 14 October 2004, 2428 patients were enrolled into the study. Of these, 255 were EMS-witnessed arrests and were excluded. 1695 cases did not receive any bystander CPR, 287 had standard CPR and 154 CC-CPR. Patient characteristics were similar in both the standard and CC-CPR groups except for a higher incidence of residential arrests and previous heart disease sufferers in the CC-CPR group. Patients who received standard CPR (odds ratio (OR) 5.4, 95% confidence interval (CI) 2.1-14.0) or CC-CPR (OR 5.0, 95% CI 1.5-16.4) were more likely to survive to discharge than those who had no bystander CPR. There was no significant difference in survival to discharge between those who received CC-CPR and standard CPR (OR 0.9, 95% CI 0.3-3.1). CONCLUSION: We found that patients were more likely to survive with any form of bystander CPR than without. This emphasises the importance of chest compressions for OHCA patients, whether with or without ventilation.

Comparison of termination-of-resuscitation guidelines for out-of-hospital cardiac arrest in Singapore EMS.

CONTEXT: Termination of resuscitation (TOR) in the field for out-of-hospital cardiac arrest (OHCA) can reduce unnecessary transport to hospital and increase availability of resources for other patients. OBJECTIVES: To compare the performance of three TOR guidelines for Basic Life Support-Defibrillator (BLS-D) providers when applied to cardiac arrest patients in the Cardiac Arrest and Resuscitation Epidemiology (CARE) study. DESIGN: This prospective cohort study involved all OHCA patients attended by BLS-D providers in a large urban center. The data analyses were conducted secondarily on these prospectively collected data. Three TOR guidelines proposed by Marsden et al. [BMJ 1995;311:49-51], Petrie [CJEM 2001;3:186-92] and Verbeek et al. [Acad Emerg Med 2002;9:671-8] were applied to show the relationship between the guidelines and actual survival. RESULTS: From 1 October 2001 to 14 October 2004, 2269 patients were enrolled into the study. Thirty-two (1.4%) survived to hospital discharge. For the 3 TOR guidelines, sensitivity was 93.8% (95%CI=79.9-98.3) (Petrie), 81.3% (95%CI=64.7-91.1) (Verbeek) and 90.6% (95%CI=75.8-96.8) (Marsden). Negative predictive value was 99.7% (95%CI=99.0-100.0) (Petrie), 99.6% (95%CI=99.2-99.8) (Verbeek) and 99.8% (95%CI=99.4-99.9) (Marsden). Application of these guidelines would have resulted in transport of 68.4% (Petrie), 31.3% (Verbeek) and 36.1% (Marsden) of cases. The Petrie guidelines would have recommended TOR in two patients who eventually survived. Similarly TOR was recommended in six patients for Verbeek and three patients for Marsden who eventually survived. CONCLUSION: We found all three TOR guidelines to have high sensitivity and negative predictive value. However the specificity and transport rates varied greatly. Application of any TOR guidelines may be affected by local EMS and population factors which should be considered in any policy decision.

Survival outcomes with the introduction of intravenous epinephrine in the management of out-of-hospital cardiac arrest.

STUDY OBJECTIVE: The benefit of epinephrine in cardiac arrest is controversial and has not been conclusively shown in any human clinical study. We seek to assess the effect of introducing intravenous epinephrine on the survival outcomes of out-of-hospital cardiac arrest patients in an emergency medical services (EMS) system that previously did not use intravenous medications. METHODS: This observational, prospective, before-after clinical study constitutes phase II of the Cardiac Arrest and Resuscitation Epidemiology project. Included were all patients who are older than 8 years, with nontraumatic out-of-hospital cardiac arrest conveyed by the national emergency ambulance service. The comparison between the 2 intervention groups for survival to discharge was made with logistic regression and expressed in terms of the odds ratio (OR) and the corresponding 95% confidence interval (CI). RESULTS: From October 1, 2002, to October 14, 2004, 1,296 patients were enrolled into the study, with 615 in the pre-epinephrine and 681 in the epinephrine phase. Demographic and EMS characteristics were similar in both groups. Forty-four percent of patients received intravenous epinephrine in the epinephrine phase. There was no significant difference in survival to discharge (pre-epinephrine 1.0%; epinephrine 1.6%; OR 1.7 [95% CI 0.6 to 4.5]; adjusted for rhythm OR 2.0 [95% CI 0.7 to 5.5]); return of circulation (pre-epinephrine 17.9%; epinephrine 15.7%; OR 0.9 [95% CI 0.6 to 1.2]), or survival to admission (pre-epinephrine 7.5%; epinephrine 7.5%; OR 1.0 [95% CI 0.7 to 1.5]). There was a minimal increase in scene time in the epinephrine phase (10.3 minutes versus 10.7 minutes; 95% CI of difference 0.02 to 0.94 minutes). CONCLUSION: We were unable to establish a significant survival benefit with the introduction of intravenous epinephrine to an EMS system. More research is needed to determine the effectiveness of drugs such as epinephrine in resuscitation.