Venkataraman Anantharaman

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 Treatment of Supraventricular Tachycardia by Valsalva Maneuver and Carotid Sinus Massage

STUDY OBJECTIVE To compare the efficacy of the Valsalva maneuver with that of carotid sinus massage (CSM) in terminating paroxysmal supraventricular tachycardia (SVT) in the ED. METHODS This prospective, randomized case study was performed in the ED of a tertiary care institution. Patients were at least 10 years of age with regular narrow complex tachycardia and had an ECG diagnosis of SVT. Patients with regular narrow complex tachycardia were randomly assigned to undergo either the Valsalva maneuver or CSM. If the tachycardia was not terminated by the method chosen by randomization, then the alternative method of vagal maneuver was used. If the tachycardia was not converted by both methods of vagal stimulation, patients would undergo either synchronized electrical cardioversion or a pharmacologic method of conversion at the discretion of the treating physician, depending on the patients hemodynamic status. RESULTS One hundred forty-eight instances of SVT were studied. Sixty-two patients underwent Valsalva maneuver first with conversion in 12 (success rate of 19.4%). Eighty-six underwent CSM first with conversion in 9 (success rate 10.5%). Carotid sinus massage was used in the 50 cases of SVT in which conversion was not achieved with the Valsalva maneuver. Conversion occurred in 7 cases (success rate 14.0%). For the 77 cases of SVT in which initial CSM did not achieve conversion, conversion occurred in 13 with the Valsalva maneuver (success rate 16.9%). The Valsalva maneuver and CSM achieved conversion in a total of 41 instances of SVT (success rate 27.7%). CONCLUSION Vagal maneuvers are efficacious in terminating about one quarter of spontaneous SVT cases. There is no detectable difference in efficacy between the Valsalva maneuver and CSM. [Lim SH, Anantharaman V, Teo WS, Goh PP, Tan ATH: Comparison of treatment of supraventricular tachycardia by Valsalva maneuver and carotid sinus massage. Ann Emerg Med January 1998;31:30-35.].

Road traffic accident mortality in Singapore

The aim of this study was to identify factors that contribute to road traffic accident mortality and the patterns of injuries sustained by these victims, with a view to identifying areas for future intervention. All road traffic accident deaths that occurred in Singapore over a period of 1 year were reviewed. A total of 226 deaths occurred: 82.3% of the victims were male. The median age was 31 years. Blood alcohol was detected in 42 (18.7%) victims. In general, head (86.7%), followed by thoracic (67.7%) and abdominal (31.4%) injuries, were the most common injuries. Severe lower extremity trauma was most common among pedestrians and pedal cyclists (20.6% and 11.0%, respectively). The mean Injury Severity Score was 38.7. The relative risk of mortality between motorcyclists and motorcar drivers was 18.8:1. Suggestions for future prevention and intervention include stricter enforcement of speed limits, more severe penalties for drunk driving, helmet use among pedal cyclists, and the introduction of pre-hospital advanced airway management.

C ARDIAC A RREST AND R ESUSCITATION E PIDEMIOLOGY IN S INGAPORE (CARE I S TUDY )

Objectives. To describe the epidemiology of out-of-hospital cardiac arrest (OHCA) in Singapore, the emergency medical services (EMS) response, and to identify possible areas for improvement. Methods. This prospective observational study constitutes phase I of the Cardiac Arrest and Resuscitation Epidemiology (CARE) project. Included were all patients with nontraumatic OHCA conveyed by the national emergency ambulance service. Patient characteristics, cardiac arrest circumstances, EMS response, and outcomes were recorded according to the Utstein style. Results. From October 1, 2001, to April 30, 2002, 548 patients were enrolled into the study. Mean (standard deviation [SD]) age was 62.2 (17.9) years, with a male predominance (65.6%). A total of 59.8% of collapses occurred at home, 35.3% of arrests were not witnessed, and bystander cardiopulmonary resuscitation was present for 20.6%. Mean (SD) time from collapse to call received by EMS was 10.6 (13.1) minutes. Mean (SD) EMS response time was 10.2 (4.3) minutes. Mean (SD) time from call to defibrillation was 16.7 (7.2) minutes. Mean (SD) on-scene time was 9.9 (4.5) minutes. First presenting rhythm at the scene was asystole in 54.5%, pulseless electrical activity 22.9%, ventricular fibrillation 19.6%, and ventricular tachycardia 0.4%. Of all cardiac arrests, 351 had resuscitation attempted and were of cardiac origin. Among these patients, 17.9% had return of spontaneous circulation, 8.5% survived to hospital admission, and 2.0% survived to discharge. Conclusion. CARE I establishes the baseline for the evaluation of incremental introduction of prehospital Advanced Cardiac Life Support interventions planned for future phases. Continuing efforts should be made to strengthen all chains of survival. This represents the most comprehensive OHCA study yet conducted in Singapore.

Phonocardiographic Signal Analysis Method Using a Modified Hidden Markov Model

Auscultation is an important diagnostic indicator for cardiovascular analysis. Heart sound classification and analysis play an important role in the auscultative diagnosis. This study uses a combination of Mel-frequency cepstral coefficient (MFCC) and hidden Markov model (HMM) to efficiently extract the features for pre-processed heart sound cycles for the purpose of classification. A system was developed for the interpretation of heart sounds acquired by phonocardiography using pattern recognition. The task of feature extraction was performed using three methods: time-domain feature, short-time Fourier transforms (STFT) and MFCC. The performances of these feature extraction methods were then compared. The results demonstrated that the proposed method using MFCC yielded improved interpretative information. Following the feature extraction, an automatic classification process was performed using HMM. Satisfactory classification results (sensitivity ≥0.952; specificity ≥0.953) were achieved for normal subjects and those with various murmur characteristics. These results were based on 1398 datasets obtained from 41 recruited subjects and downloaded from a public domain. Constituents characteristics of heart sounds were also evaluated using the proposed system. The findings herein suggest that the described system may have the potential to be used to assist doctors for a more objective diagnosis.

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.

Slow infusion of calcium channel blockers compared with intravenous adenosine in the emergency treatment of supraventricular tachycardia.

INTRODUCTION The emergency treatment of supraventricular tachycardia (SVT) has, over the last two decades, changed from verapamil to adenosine primarily owing to documented hypotensive episodes occurring with rapid bolus infusions of the calcium channel blocker. Slow infusions of calcium channel blockers have not previously demonstrated hypotension to any significant degree. The aim of this study was to compare the efficacy and safety of bolus intravenous adenosine and slow infusion of the calcium channel blockers verapamil and diltiazem in the emergency treatment of spontaneous SVT. METHODS A prospective randomized controlled trial with one group receiving bolus intravenous adenosine 6 mg followed, if conversion was not achieved, by adenosine 12 mg; and the other group receiving a slow infusion of either verapamil at a rate of 1mg per minute up to a maximum dose of 20mg, or diltiazem at a rate of 2.5mg per minute up to a maximum dose of 50mg. These infusions would be stopped at time of conversion of the SVT or when the whole dose was administered. Heart rate and blood pressure was continuously monitored during drug infusion and for up to 2h post-conversion. RESULTS A total of 206 patients with spontaneous SVT were analysed. Of these, 102 were administered calcium channel blockers (verapamil=48, diltiazem=54) and 104 were given adenosine. The conversion rates for the calcium channel blockers (98%) were statistically higher than the adenosine group (86.5%), p=0.002, RR 1.13, 95% CI 1.04-1.23. The initial mean change in blood pressure post-conversion in the calcium channel blocker group was -13.0/-8.1 mmHg (verapamil) and -7.0/-9.4 mmHg (diltiazem) and 2.6/-1.7 mmHg for adenosine. Only one patient in the calcium channel group (0.98%) (95% CI 0.025-5.3) developed hypotension, and none in the adenosine group. CONCLUSION Slow infusion of calcium channel blockers is an alternative to adenosine in the emergency treatment of stable patients with SVT. Calcium channel blockers are safe and affordable for healthcare systems where the availability of adenosine is limited.

Bystander cardiopulmonary resuscitation in prehospital cardiac arrest patients in Singapore.

Introduction. The chain of survival emphasizes the importance of the four links associated with survival after cardiac arrest (CA). The involvement of laypersons has been increasing over the years. They have been contributing toward “early access,” “early cardiopulmonary resuscitation” (CPR), and, of late, “early defibrillation,” with the advent of automated external defibrillators (AEDs). Bystander CPR rates are difficult to assess due to the lack of formal documentation. Objective. To assess the bystander CPR rate for CA patients brought to the emergency department (ED) of an urban, tertiary teaching hospital in the central part of Singapore, over a period of 12 months. Methods. This was a retrospective cohort study carried out from May 1, 1999, to April 30, 2000. “Bystander CPR” refers to an attempt to perform basic CPR by someone who is not part of an organized emergency response system. In general, this refers to the person who witnesses the arrest. Results. There were 155 adult patients with CA who satisfied the inclusion criteria over the 12-month period. The median age was 62.1 ± 6.4 years, and the majority of patients were brought in by ambulances (126, or 81.3%). There were 142 (91.6%) non-trauma and 13 (8.4%) trauma CAs. Most patients had the CA at home (96, or 61.9%), and the most common initial rhythm at presentation upon the arrival of the paramedics was ventricular fibrillation (VF) (50 patients, or 32.2%). The bystander CPR rate was 20.0% (i.e., 31 of the 155 patients). A total of 32 (20.6%) patients had return of spontaneous circulation (ROSC, defined as the return of a palpable pulse) and 31 (96.9%, or 31/32) of them were those who had some form of bystander CPR performed. Of these 31 who had bystander CPR, four (12.9%) were subsequently admitted to the intensive care unit (ICU), while among those who did not have bystander CPR, all had death pronounced in the ED. Of the four patients admitted to the ICU, three (3 of 4, or 75.0%; or 3 of 155 CA patients, or 1.9%) were subsequently discharged alive from the hospital. Conclusion. The bystander CPR rate for prehospital CA was 20.0%. About 12.9% (4 patients) of those who had bystander CPR were admitted to the ICU, compared with none from the group that did not receive any form of bystander CPR. Three patients (1.9% of all prehospital CAs) were discharged alive from the hospital.

Delays in the EMS response to and the evacuation of patients in high-rise buildings in Singapore

Background. Singapore is a highly urbanized and cosmopolitan city situated at the crossroads of Southeast Asia. High-rise buildings and “vertical living” are common, and the city serves as a major business, financial, and industrial hub in the region. More than 80% of the population live in high-rise apartments. This poses unique problems and challenges for emergency ambulance services personnel in the access to and evacuation of patients. Objective. To estimate the arrival-to-patient contact delay when accessing patients in high-rise buildings and evacuating them to the hospital, compared with accessing patients in ground-level premises. Methods. This was a prospective study carried out from February 2 to March 1, 1998, for emergency calls from two of the busiest fire stations. The first 150 consecutive cases were enrolled into each of the two groups. Cases of road traffic accidents were excluded because these did not require the crew to get into a building. The times were clocked by one of the paramedics, using a stopwatch. A high-rise building was defined as one where the crew had to ascend at least one flight of stairs. A ground-level building did not involve any stair climbing. We set forth to determine whether the interval between the following was statistically significant when comparing high-rise vs ground-level premises: 1) time when the ambulance arrives at the scene (taken as the time when the driver turns the engine off) and time of arrival at the patients side; 2) time of leaving the dwelling with the patient and time when the ambulance starts its journey to the hospital (taken as the time when the driver starts the engine). Data analysis was done with the use of SPSS, and the one-tailed unpaired Students t-test was used for significance testing, with the alpha error rate set at 0.05. Results. One hundred fifty runs were analyzed for each group. The mean delay from arrival to patient contact was 2.49 ± 0.98 minutes for the high-rise group compared with 1.02 ± 1.41 minutes for the ground-level group (difference was statistically significant with 95% CI: 1.20, 1.74 minutes; p = 0.0106). The mean delays from the time of leaving the building with the patient to the time when the ambulance turned its engine on to start its journey to the hospital were 3.24 ± 1.58 minutes and 1.27 ± 0.71 minutes for the two groups, respectively (difference was statistically significant with 95% CI: 1.68, 2.04 minutes; p = 0.0098). Conclusion. There were significant delays present when accessing patients in high-rise buildings and evacuating them to the hospital. Modification to buildings and increasing public awareness and education have been suggested to help minimize these delays.

International Federation for Emergency Medicine model curriculum for medical student education in emergency medicine

There is a critical and growing need for emergency physicians and emergency medicine resources worldwide. To meet this need, physicians must be trained to deliver time-sensitive interventions and life-saving emergency care. Currently, there is no internationally recognized, standard curriculum that defines the basic minimum standards for emergency medicine education. To address this lack, the International Federation for Emergency Medicine (IFEM) convened a committee of international physicians, health professionals, and other experts in emergency medicine and international emergency medicine development to outline a curriculum for foundation training of medical students in emergency medicine. This curriculum document represents the consensus of recommendations by this committee. The curriculum is designed with a focus on the basic minimum emergency medicine educational content that any medical school should be delivering to its students during their undergraduate years of training. It is not designed to be prescriptive, but to assist educators and emergency medicine leadership in advancing physician education in basic emergency medicine content. The content would be relevant, not just for communities with mature emergency medicine systems, but also for developing nations or for nations seeking to expand emergency medicine within current educational structures. We anticipate that there will be wide variability in how this curriculum is implemented and taught, reflecting the existing educational milieu, the resources available, and the goals of the institutions’ educational leadership.