Outcome and prognostic factors of patients in out-of-hospital cardiac arrests presenting with non-shockable rhythm in Hong Kong

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1 Hong Kong Journal of Emergency Medicine Outcome and prognostic factors of patients in out-of-hospital cardiac arrests presenting with non-shockable rhythm in Hong Kong KL Leung, CT Lui, KH Cheung, KL Tsui, YH Tang Objective: To obtain the recent local epidemiological data and evaluate factors associated with outcomes of adult patients in non-traumatic non-shockable out-of-hospital-cardiac-arrest (OHCA) in Hong Kong. Methods: It was a cross-sectional study lasting for nine months (from July 2009 to March 2010) in two emergency departments (ED) which served a population of 1.1 million. All non-traumatic OHCA patients aged equal or greater than 18 years presented with non-shockable cardiac rhythms to ED without postmortem changes were included. The pre-hospital factors, managements and outcomes were recorded in a standardised data entry form at the time of patient consultation. Logistic regression was used to evaluate the relationship between survival to admission (STA) and various prognostic factors. Results: A total of 348 patients fulfilled the inclusion criteria. The mean age was 75.9 years old. Overall, there were 61 patients (17.5%) with restoration of spontaneous circulation and 58 patients (16.7%) had STA. The survival to hospital discharge (STD) rate was 0.86% (3 patients). Factors independently associated with better prognosis in terms of STA were initial pulseless electrical activity arrest (PEA) rhythm in ED (OR=4.72, 95% CI ), witnessed arrest (OR=8.00, 95% CI ) and non-cardiac cause of arrest (OR=2.17, 95% CI ). Conclusion: STA for adults presenting with non-traumatic non-shockable OHCA in our centre is 16.7%. Witnessed non-shockable OHCA patients presenting with initial PEA arrest rhythm and with a presumed non-cardiac in etiology are significantly associated with higher STA rate. (Hong Kong j.emerg. med. 2012;19:6-12) OHCA ED ( 110 ) OHCA STA STA STD STA : ED PEA OR= CI OR= CI OR= CI Correspondence to: Cheung Koon Ho, MRCSEd, FHKCEM, FHKAM(Emergency Medicine) Prince of Wales Hospital, Accident and Emergency Department, Ngan Shing Street, Shatin, New Territories, Hong Kong (previously at Tuen Mun Hospital, Accident and Emergency Department) koonhocheung@yahoo.com.hk Tuen Mun Hospital, Accident and Emergency Department, Tsing Chung Koon Road, Tuen Mun, New Territories, Hong Kong Leung Kwong Leung, MBChB Lui Chun Tat, MBBS(HK), FHKCEM, FHKAM(Emeregncy Medicine) Tsui Kwok Leung, FRCSEd, FHKCEM, FHKAM(Emergency Medicine) Tang Yiu Hang, FRCSEd, FHKCEM, FHKAM(Emergency Medicine)

2 Leung et al./ohca with non-shockable rhythm 7 OHCA STA 16.7 OHCA PEA STA Keywords: Asystole, cardiopulmonary resuscitation, heart arrest, pulseless electrical activity, survival to admission Introduction The overall survival for out-of-hospital cardiac arrest (OHCA) in the world was low all along. In 2002, rate of survival to hospital discharge (STD) ranged from 4% to 9% worldwide. 1 However, for those presented with non-shockable rhythm, only 1% to 4% survived. In North America, a prospective observational study in 2006 and 2007 revealed overall survival rate of 4.6% for OHCA. 2 In Hong Kong, according to a local study in 1999, the overall survival rate for non-traumatic OHCA was 1.3%. The survival rate for non-shockable rhythm was only 0.7%. 3 Since majority of OHCA cases are non-shockable cardiac arrest rhythm, we aimed at exploring the characteristics of OHCA and the factors affecting the STD. Methods Our study was a cross-sectional study carried out in two emergency departments (ED) in New Territories West region of Hong Kong. The period of study was from 1 July, 2009 to 31 March, It was a study nested on the Cardiac Arrest Project in our hospitals. We focused on non-shockable cardiac arrest rhythms and the study was approved by the local research ethics committee. During the study period (July 2009-March 2010), the updated cardiopulmonary resuscitation and emergency cardiovascular care guideline in-used was the American Heart Association (AHA) 2005 Guidelines. We applied the AHA 2005 resuscitation guidelines throughout our study period. All the outcomes and prognostic factors presenting in this study referred to the practice stated in the AHA 2005 guidelines. All patients aged 18 years or above who suffered from non-shockable OHCA and attended the ED were included. We selected cases only presented with initial non-shockable arrest rhythms of pulseless electrical activity (PEA) or asystole upon arrival in ED. Patients with shockable rhythms idenified or received defibrillation during pre-hospital or hospital cardiopulmonary resuscitation (CPR) were excluded. In this study, we defined shockable rhythm as ventricular fibrillation, pulseless ventricular tachycardia or rhythm initiated shock by automated external defibrillators. Patients with traumatic cause of cardiac arrest or those with post-mortem body changes upon arrival to the ED were also excluded. Several characteristics including age, gender, witness status, presence of bystander CPR, arrest site, pre-hospital airway, initial arrest rhythm, arrest aetiology and outcomes of patients were investigated. The study outcome was survival to admission (STA). Attending emergency physicians would classify causes of arrest based on their clinical assessment and bystander information. Patients were classified as presumed cardiac cause of arrest if they had clues suggestive of cardiac origin such as witnessed sudden collapse, cardiac rhythm showed myocardial infarction, or history of coronary artery disease presented with angina. Patients were classified as presumed noncardiac cause of arrest if they had clues suggestive of respiratory, poisoning, non-traumatic intracranial bleeding, malignancy, near drowning or other noncardiac causes. 4 For each arrest case, data was entered into a predesigned Cardiac Arrest Registry (CAR) form. The CAR form was designed with reference to Utstein reporting template. 5 The CAR form included 13 sets of optical marks, covering items like demographic,

3 8 Hong Kong j. emerg. med. Vol. 19(1) Jan 2012 management and outcome of patients. The attending doctors filled in the CAR forms immediately after disposal of patients. Nursing staff would cross-check the completeness of documents, including CAR form, photocopies of ambulance record, ambulance ECG record and ED resuscitation chart records. The documents would then be put into the data collection box. The researchers collected the data at a batch for review. Data was transcribed from CAR form to an electronic database by optical mark recognition. Survival outcomes were traced manually through electronic patient records system. We calculated our sample size by assuming a power of 80%, significance level 5%, baseline prevalence of STA in non-shockable OHCA as 9.4% to detect a moderate effect size of odds ratio (OR) 2 or higher. 6 An adjustment of regression of one independent variable on the other was made and R-Square was assumed to be The total sample size required would be 319 as calculated by PASS 2008 Software by NCSS, US. 7 The Statistical Package for Social Sciences (Version 16.0, SPSS Inc., Chicago) was employed for analysis. A p-value of less than 0.05 was regarded as statistically significant. Catagorical variables were expressed as percentages while continuous variables were expressed as mean and standard deviation. For analysis of STA versus various predictor variables, discrete variables were evaluated by chi-square test. Continuous variables were analysed by student's t-test. Potential prognostic factors were entered into binary logistic regression model. Model calibration was evaluated with Hosmer- Lemeshow goodness-of-fit test. Results Totally 421 patients aged at least 18 years presented with non-traumatic OHCA without post-mortem changes within the study period. Among them, 348 patients (82.7%) presented with non-shockable rhythms [62 patients (17.8%) exhibited PEA, 286 patients (82.2%) exhibited asystole] and fulfilled all the criteria for inclusion in this study. Sixty-one patients (17.5%) had a return of spontaneous circulation after resuscitation. Fifty-four patient survived at least 4 hours after admission and the STA rate was 16.7%. Three patients survived to discharge, therefore the STD rate was 0.86%. Among patients with non-shockable rhythms, 56% of them were male patients, and the mean age was 75.9 years old. A majority of them had cardiac arrest at home (39.4%) and 151 patients (43.4%) were assumed having cardiac origin as the cause of arrest. We classified combitube, laryngeal mask airway or endotracheal tube as pre-hospital advanced airways and they were applied in 11.8% of patients in this study. The characteristics and outcomes of subjects studied were listed in Table 1. Among patients with initial PEA arrested rhythm, 41.9% of them could survive to admission. Among patients with initial asystole arrest rhythm, only 11.2% of them had STA. Notably, 21.7% (10/46) of those who received bystander CPR and 17.1% (7/46) of those who received pre-hospital advanced airway management could survive to admission. Mean age of patients survived to admission was 72.0 years, which was younger than those who did not survived to admission (mean age 76.7 years). Univariate analysis of outcome in terms of STA was listed in Table 2. Binary logistic regression showed that witnessed arrest (OR=8.00, 95% CI= ), initial PEA arrest rhythm in ED (OR=4.72, 95% CI= ), and presumed non-cardiac origin of arrest (OR=2.17, 95% CI= ) were the three significant independent predictors for better STA with p-value less than 0.05 (Table 3). The model calibration of the logistic regression was satisfactory with p=0.674 in the Hosmer and Lemeshow goodness-of-fit test. Discussion OHCA is a big challenge faced by medical care. CAR had been implemented in the United State ten years ago, but is not well-established in Hong Kong. 8 Our Cardiac Arrest study aims to serve the purpose of CAR, so that OHCA data was recorded more accurately and updated resuscitation outcome could be obtained.

4 Leung et al./ohca with non-shockable rhythm 9 Overall survival rate reported for OHCA in Hong Kong was poor (STD rate 0.05% to 1.54%) 3,9,10 when compared to European or North America countries (STD rate 3% to 25%) 11 or even to the Province of Hainan in Mainland China (4.7%). 12 Our study results Table 1. Characteristics and outcomes of adult patients in non-traumatic out-of-hospital cardiac arrests presenting with non-shockable rhythms Characteristics of patients Number of patients (percentage, %) Mean age (years) ± SD 75.9 ± 16.1 Gender Male 195 (56.0) Female 153 (44.0) Witnessed arrest Yes 160 (46.1) No 187 (53.9) Bystander CPR Yes 46 (13.2) No 302 (86.8) Site of arrest Home 137 (39.4) Old age home 141 (40.5) Inside other building 36 (10.3) Open area 22 (6.4) Ambulance 12 (3.4) Pre-hospital airway Total: 321 (92.2) Combitube* 11 (3.2) Laryngeal mask airway* 30 (8.6) Endo-tracheal tube* 0 (0.0) Oropharyngeal airway 280 (80.5) Presumed arrest aetiology Cardiac cause 151 (43.4) Pulmonary disease 26 (7.5) Drug overdose 2 (0.6) Intracranial haemorrhage 1 (0.3) Terminal cancer 26 (7.5) Near drowning 1 (0.3) Other causes 141 (40.4) Outcomes Return of spontaneous circulation 61 (17.5) Survival to admission Total: 58 (16.7) General ward 44 (12.6) Intensive care unit/coronary care unit 14 (4.1) Survival to discharge 3 (0.86) CPR=cardiopulmonary resuscitation; SD=standard deviation; *classified as advanced pre-hospital airway (STA 16.7%, STD <1%) concurred to a poor outcome of OHCA locally especially among the subgroup with non-shockable rhythm. Factors significantly associated with STA included witnessed arrests (versus un-witnessed arrests), initial PEA arrest rhythm in ED (versus asystole) and presumed cause of arrest not due to cardiac origin (versus cardiac causes). Reason for witnessed arrest to have better survival could be easy to understand. When arrest was witnessed, delay to emergency medical service and transfer to emergency department would be less than in cases of un-witnessed arrest. 13 Concerning PEA versus asystole, PEA had better survival in our study, which was compatible with previous study results. It was because underlying reversible causes in PEA could be detected and corrected in some cases. Some of those classified PEA could be "pseudo PEA"; in those cases, the patients had some pulsatile blood flow despite no palpable pulses clinically. 14 For OHCA due to cardiac causes, coronary artery disease is by far the most common underlying aetiology and it is assumed to present more likely with a shockable rhythm. While early defibrillation may lead to a return of perfusing rhythm, they are usually associated with better survival. However, would the same observation hold for those OHCA due to cardiac cause but presenting with non-shokable rhythm? In our study, we found that OHCA with non-shockable rhythm due to cardiac causes had less STA than those with non-cardiac causes. The reason behind was not well understood. It is a general belief that younger age is associated with better outcome in many disease events. However, in this regression model analysis, age was found not to be a significant factor associated with STA (OR 0.99, p=0.151). It concurred with previous study reporting that age itself was not a major determinant of outcome for OHCA. However, their associated co-morbidities could be important predicting factors. 15 We noticed that among all cases with non-shockable arrest rhythm, 46% cases (160/348) were witnessed arrests.

5 10 Hong Kong j. emerg. med. Vol. 19(1) Jan 2012 However, only 13.2% of cases (46/348) had received bystander CPR. It reflected a low bystander CPR intention in the citizens of our locality. It was comparable to the reported rate of 15.5% by Chung & Wong. 16 It could be related to a diversified causes including inadequate training, afraid of legal consequences, or fear of mouth-to-mouth contact with strangers. 17 Bystander CPR itself was not a statistically significant prognostic factor for STA in our study, which was quite a surprise. Most of the bystanders CPR in our study were carried Table 2. Univariate analysis of survival to admission predicted by different variables among non-shockable cardiac arrests Predictive variables Number of patients (percentage, %) Survival to admission (percentage, %) p-value [Total no.=348] [Total no.=58] Pre-hospital advanced airway Yes 41 (11.8) 7 (17.1) No 307 (88.2) 51 (16.5) Arrest site at home Yes 137 (39.4) 22 (16.1) No 211 (60.6) 36 (17.1) Etiology of arrest Cardiac 151 (43.4) 30 (19.9) Non-cardiac 191 (56.6) 28 (14.2) Bystander CPR Yes 46 (13.2) 10 (21.7) No 302 (86.8) 48 (15.9) Witnessed arrest Yes 160 (46.0) 46 (28.8) <0.001 No 188 (54.0) 12 (6.4) Gender Male 195 (56.0) 27 (13.8) Female 153 (44.0) 12 (7.8) Arrest rhythm PEA 62 (17.8) 26 (41.9) <0.001 Asystole 286 (82.2) 32 (11.2) All variables given as numbers (percentages in parentheses). CPR=cardiopulmonary resuscitation; PEA: pulseless electrical activity Table 3. Logistic regression of survival to admission Independent predictors Odds ratio 95% confidence interval p-value Bystander CPR Advanced pre-hospital airway Witnessed arrest <0.001 Arrest at home Aetiology (Not due to cardiac cause) Initial arrest rhythm in ED <0.001 (PEA rhythm) Gender (Male) Age (years) *The model calibration was satisfactory as shown by Hosmer and Lemeshow goodness-of-fit test with p= ED=emergency department. PEA=pulseless electrical activity. CPR=cardiopulmonary resuscitation.

6 Leung et al./ohca with non-shockable rhythm 11 out in old age home, where cardiac arrest happened. It posed a query on the quality of bystander CPR performed by old age home staff. More public education of simplified CPR techniques should be advocated. Our study showed that initial PEA rhythm, noncardiac cause of arrest and witnessed arrest were statistically significant factors associated with better outcome in non-shockable OHCA. However, these factors were not directly affected by a simple change in practice or improvement in the standard of resuscitation delivered within hospital setting. However, these information could be useful to guide our approach, utilisation of resources and duration of resuscitation on further non-shockable OHCA cases. Although our study showed improvement in ROSC and STA, STD remained to be low (0.86%). One reason could be unsatisfactory post-resuscitation supports. In our study, there were 61 subjects (17.5%) with ROSC after resuscitation and 58 patients (16.7%) with STA, however only 14 patients (24.1%) were admitted to intensive care unit (ICU) or coronary care unit (CCU) and most of them were admitted to general ward. If more STA patients could receive intensive care support, survival outcomes might be better. Despite the poor survival outcome of our study with nonshockable OHCA, our reported ROSC and STA were slightly better than the rates reported in the previous local studies in Hong Kong. During , the overall ROSC rate of non-traumatic OHCA was 7.6% as shown in a study by Chung & Wong. 16 During , STA rate for asystole and PEA were 9.8% and 9.1% respectively reported by Lau et al 10 Based on 2002 data, a teaching hospital in Hong Kong reported ROSC rate as 26.8%, STA rate as 12.1% for witnessed cardiogenic OHCA patients presented with asystole and PEA. 18 In our study, the rate for ROSC and STA rate in non-shockable cardiac arrests were 17.5% and 16.7% respectively, while STD rate was 0.86%. The overall survival rate (in terms of ROSC and STA) was higher when compared with local rates before In 2005, there was the implementation of new guideline. Our study reflected resuscitation outcome with AHA 2005 Guidelines. Further studies would be required to monitor the impact on the outcomes of OHCA after the implementation of the new AHA 2010 resuscitation guidelines. Limitations A difficulty in our CAR was unsatisfactory on-site completion rate of CAR forms. We had an audit on this issue and found that around 29% cases had at least one missing data or incorrect input. Such missing information were filled retrospectively with reference to available documentations in A&E notes and ambulance records. Inadequate information in ambulance records regarding pre-hospital data were found in many cases. Another limitation of our study was absence of prehospital time interval. The reason was that while we could not get pre-hospital time data in Ambulance Journey Report, there was considerable problem of missing data and recall bias when pre-hospital time was obtained from bystanders. Furthermore, presumed causes of cardiac arrest were clinical judgment by the attending physicians instead of autopsy results. This could be a problem because clinical judgement could be inaccurate and leading to incorrect classification. 19 Finally, number of STD cases was too small to allow a proper analysis like the neurologically outcome of the survivors. Conclusion STA and STD for adults in non-traumatic nonshockable OHCA in our centre based on AHA 2005 Guidelines are 16.7% and 0.86% respectively. For nonshockable, non-traumatic OHCA aged 18 years or above, three independent prognostic factors are significantly associated with higher chance of STA: witnessed arrest, initial PEA arrest rhythm in ED, and causes not due to cardiac origin. In Hong Kong, use of CAR can monitor OHCA characteristics and identify rooms for improvement in our practice. We suggest continual maintenance and development of an uniform, territory-wide CAR in our locality.

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