non-shockable out-of-hospital cardiac arrest in hk

8/3/2019 Non-Shockable Out-Of-hospital Cardiac Arrest in HK

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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 post-mortem changes were included. The pre-hospital factors, managements and outcomes were recorded in astandardised 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 348patients 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 tohospital 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 2.30-9.69), witnessed arrest (OR=8.00, 95% CI 3.38-18.96) and non-cardiac cause of arrest (OR=2.17, 95% CI

1.00-4.67). Conclusion: STA for adults presenting with non-traumatic non-shockable OHCA in our centreis 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:xx-xx)

OHCA

ED ( 110 )

9 2009 7 2010 3 18

OHCA

STA

348 75.9 61 17.5

58 16.7 STA STD 0.86 3 STA

: ED PEA OR= 4.72 95 CI2.30-9.69

OR=8.00 95 CI 3.38-18.96 OR=2.17 95 CI1.00-4.67

Correspondence to:Cheung Koon Ho, MRCSEd, FHKCEM, FHKAM(Emergency Medicine)

Prince of Wales Hospital, Accident and Emergency Department,30-32 Ngan Shing Street, Shatin, New Territories, Hong Kong(previously at Tuen Mun Hospital, Accident and Emergency Department) Email: [email protected]

Tuen Mun Hospital, Accident and Emergency Department, TsingChung Koon Road, Tuen Mun, New Territories, Hong KongLeung 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)



Hong Kong j. emerg. med. Vol. 19(1) Jan 20122

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, 2010. 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 Associat ion (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

defibri l lat ion 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 andoutcomes 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 non-cardiac cause of arrest if they had clues suggestive of

respiratory, poisoning, non-traumatic intracranial

bleeding, malignancy, near drowning or other non-

cardiac causes.4

For each arrest case, data was entered into a pre-

designed 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,

OHCA STA 16.7

OHCA PEA STA

Keywords: Asystole, cardiopulmonary resuscitation, heart arrest, pulseless electrical activity, survival toadmission



Leung et al./OHCA with non-shockable rhythm 3

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 ECGrecord 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 s ize 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 0.40. 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 expressedas 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 75.9years 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=3.38-18.96),

initial PEA arrest rhythm in ED (OR=4.72, 95%

CI=2.30-9.69), and presumed non-cardiac origin of

arrest (OR=2.17, 95% CI=1.00-4.67) 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.

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

(STA 16.7%, STD <1%) concurred to a poor outcome

of OHCA locally especially among the subgroup withnon-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

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 air way 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

We noticed that among all cases with non-shockable arrest

rhythm, 46% cases (160/348) were witnessed arrests.

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




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) 0.820No 307 (88.2) 51 (16.5)

Arrest site at home Yes 137 (39.4) 22 (16.1) 0.806

No 211 (60.6) 36 (17.1)

Etiology of arrestCardiac 151 (43.4) 30 (19.9) 0.161Non-cardiac 191 (56.6) 28 (14.2)

Bystander CPR Yes 46 (13.2) 10 (21.7) 0.322No 302 (86.8) 48 (15.9)

Witnessed arrest Yes 160 (46.0) 46 (28.8) <0.001No 188 (54.0) 12 (6.4)

GenderMale 195 (56.0) 27 (13.8) 0.105

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 1.44 0.56-3.66 0.447

Advanced pre-hospital airway 1.09 0.39-3.11 0.865

Witnessed arrest 8.00 3.38-18.96 <0.001 Arrest at home 0.84 0.40-1.74 0.636

Aetiology 2.17 1.00-4.67 0.049(Not due to cardiac cause)

Initial arrest rhythm in ED 4.72 2.30-9.69 <0.001(PEA rhythm)

Gender (Male) 1.71 0.86-3.38 0.126

Age (years) 0.99 0.97-1.01 0.151

*The model calibration was satisfactory as shown by Hosmer and Lemeshow goodness-of-fit test with p=0.674. ED=emergency department.

PEA=pulseless electrical activity. CPR=cardiopulmonary resuscitation.

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 prognosticfactor for STA in our study, which was quite a surprise.

Most of the bystanders CPR in our study were carried

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 beadvocated.




Our study showed that initial PEA rhythm, non-

cardiac 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 changein 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 non-

shockable OHCA, our reported ROSC and STA were

slightly better than the rates reported in the previous local

studies in Hong Kong. During 1998-2004, the overallROSC rate of non-traumatic OHCA was 7.6% as shown

in a study by Chung & Wong.16 During 2001-2003, STA

rate for asystole and PEA were 9.8% and 9.1% respectively

reported by Lau et al10 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 localrates before 2005. 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 inambulance records regarding pre-hospital data were

found in many cases.

Another limitation of our study was absence of pre-

hospital 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 non-shockable OHCA in our centre based on AHA 2005

Guidelines are 16.7% and 0.86% respectively. For non-

shockable, 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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