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Title The characteristics of patients with previous residence in mainland China admitted to the intensive care unit in Hong Kong with community-acquired pneumonia Author(s) Ho, Chun-ming; 何俊明 Citation Issued Date 2012 URL http://hdl.handle.net/10722/173739 Rights Creative Commons: Attribution 3.0 Hong Kong License

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TitleThe characteristics of patients with previous residence inmainland China admitted to the intensive care unit in Hong Kongwith community-acquired pneumonia

Author(s) Ho, Chun-ming; 何俊明

Citation

Issued Date 2012

URL http://hdl.handle.net/10722/173739

Rights Creative Commons: Attribution 3.0 Hong Kong License

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The characteristics of patients with previous residence in Mainland China admitted to

the intensive care unit in Hong Kong with community-acquired pneumonia

By

Ho Chun Ming, Chris

MBChB

This work is submitted to

The Department of Microbiology, The University of Hong Kong

In partial fulfillment of the requirements for

The Postgraduate Diploma in Infectious Diseases (PDipID) 2010-2012

Date: 30th May 2012

Supervisor: Dr. Samson SY Wong

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Declaration

I, Ho Chun Ming Chris, declare that this dissertation represents my own work and that

it has not been submitted to this or other institution in application for a degree,

diploma or any other qualifications

I, Ho Chun Ming Chris, also declare that I have read and understand the guideline on

“What is plagiarism?” published by The University of Hong Kong and that all parts of

this work complies with the guideline

Candidate: Ho Chun Ming Chris

Signature: __________________________

Date: __________________________

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Acknowledgement

I would like to thank my supervisor, Dr. Samson SY Wong (Assistant Professor,

Department of Microbiology, The University of Hong Kong) for his kind support and

guidance in this research project. I would also like to express my gratitude to Dr.

Wong Kwan Keung (Consultant, Department of Intensive Care, North District

Hospital), who gave me valuable advice in this research project.

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Contents

Chapter Page

Abstract

1 Introduction

1.1 Characteristics of Hong Kong people having

taken up residence in Mainland China

1-2

1.2 Importance of sepsis 2-3

1.3 Importance of community acquired pneumonia in

intensive care unit

3-4

2 Study objectives 5

3 Methods

3.1 Study design 6

3.2 Data collection 6-7

3.3 Inclusion and exclusion criteria 7-8

3.4 Assessment

3.4.1 Demographic Data 8

3.4.2 Clinical History 8-9

3.4.3 Disease Assessment 9

3.4.4 Outcomes 9

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3.4.5 Patterns of Infection 10

3.5 Statistical Analysis 10

4 Results

4.1 Characteristics of Patients with Sepsis from

Mainland China

11-14

4.2 Diseases Severity 15

4.3 Outcomes 15-16

4.4 Patterns of Infection 17-18

4.5 Predictors of Mortality in Patients 19

5 Discussion 20-28

6 Conclusion 29

7 Reference List 30-33

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The characteristics of patients with previous residence in

Mainland China admitted to the intensive care unit in Hong

Kong with community-acquired pneumonia

Abstract

Objectives: To review the characteristics, outcomes, patterns of infection, and

predictors of mortality in critically ill patients with community acquired pneumonia

from the Mainland China requiring intensive care in Hong Kong

Design: Retrospective cohort study

Setting: A regional hospital in Hong Kong

Patients: Critically ill patients who lived in the Mainland and were admitted to the

Intensive Care Unit (ICU) of North District Hospital (NDH) from September 2008 to

August 2010

Intervention: None

Measurements and Results: Fifty one patients (median age, 50 years) were analyzed.

It accounts for 4.1% of our annual ICU admission. The median APACHE II, SOFA,

and CURB-65 scores are 24.5, 10.5, and 6 respectively. Most of these patients

required mechanical ventilator support (n=42, 84%) in our unit. Pathogenic organisms

can be identified in the majority of these patients (n=33, 66%). The most common

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organism was Streptococcus pneumoniae. Confusion, blood urea level greater than 7

mmol/L, and higher APACHE II / CURB-65 scores are considered as poor prognostic

factors.

Conclusions: Community acquired pneumonia is a common cause of intensive care

admission among patients living in the Mainland with a significant mortality. Better

understanding of their characteristics is important.

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The characteristics of patients with previous residence in

Mainland China admitted to the intensive care unit in Hong

Kong with community-acquired pneumonia

1 Introduction

1.1 Characteristics of Hong Kong people having taken up residence in

Mainland China

The ties between Hong Kong and Mainland China have become closer after the

handover of Hong Kong in 1997 and the improvement of China’s socioeconomic

status and transportation system. There has been an increasing tendency for Hong

Kong people to reside in, take up jobs and acquire residential properties in the

Mainland. According to a survey conducted in May 2008 by the Planning department

of the Hong Kong Special Administrative Region (HKSAR) Government and the

Statistics Bureau of the Shenzhen Municipal Government [1], 61865 Hong Kong

people have taken up residence in Shenzhen for 3 months or more during the 6-month

period before enumeration. It accounts for 0.086% of Hong Kong population (6.99

million). 44262 persons (71.5%) did not intend to return to Hong Kong for residence

in the next five years. A total of 23156 (37.4%) Hong Kong people who took

residence in Shenzhen had used health care services in Hong Kong over the past six

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months. As there is continuous growth of economy in the Mainland and increasing

sophistication of the cross-boundary transport network, the Hong Kong Government

believed that the phenomenon of Hong Kong people residing in the Mainland will

continue.

1.2 Importance of sepsis

Sepsis is a complex interaction between the infecting microorganism, the host

immunity and inflammatory responses [2]. This is a great challenge to intensive care

unit (ICU) because it is a major cause of admission with a significant mortality rate.

In the United States, more than half of the patients (51.1%) with severe sepsis

required intensive care [3]. At the same time, the incidence of sepsis in the United

States increased from 0.83 cases per 1000 population in 1979 to 2.4 cases per

population in 2000 [4]. Although there are numerous close monitoring and new

antibiotics, the ICU mortality rate in patients with sepsis was still high (35%) as

reported in Pakin et al. study [5]. It is also found that the incidence of sepsis is

increasing among elderly patients [6]. Furthermore, caring critically ill patients with

sepsis requires huge resources. For example, in England, although only 27% of all

ICU admission was accounted by patients with severe sepsis, disproportionately and

nearly 45% of all ICU bed days were used [5]. Owing to greater life expectancy and

the aging of baby boomers in Hong Kong, the proportion of those aged 65 and over is

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projected to rise from 12% in 2006 to 26% in 2036 [7]. Some of these people might

end up being admitted to ICU in Hong Kong because of infection. Some of these

patients have shown mild systemic inflammatory responses. However, some can

progress to severe sepsis and even septic shock. A previous study showed that early

recognition and treatment of severe sepsis and septic shock can provide significant

benefit with respect to outcome [8]. However, those Hong Kong people living in the

Mainland often need more time for transportation to hospitals in Hong Kong. In

addition, these patients may have different pathogens after taking up residence in the

Mainland for a period of time. They may also receive different treatment modality in

the Mainland before admission. As a result, we postulate that the clinical outcomes of

these patients may be different and a deep understanding of the characteristics of these

patients is important.

1.3 Importance of community acquired pneumonia in intensive care unit

Pneumonia is the third leading cause of death in Hong Kong, which accounts for

more than 4000 deaths per year [9]. In Canada, the overall admission rate of

community acquired pneumonia (CAP) in adults is about 27 to 30 cases per 1000

persons per year [10]. According to a study by Liapikou A et al.[11], about 11 % of

patients with CAP were admitted to the ICU. The estimated cost for the treatment of

CAP in the United States is US$8.4 billion per year [12].From the Infectious Diseases

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Society of America (IDSA) / American Thoracic Society (ATS) consensus guidelines

on the management of CAP in adults, direct admission to ICU is required for patients

with septic shock requiring vasopressors or with acute respiratory failure requiring

intubation and mechanical ventilator support [13]. CAP is associated with significant

morbidity and mortality, particularly in elderly patients. The 30 day mortality rate is

about 23% [14]. From the local study conducted by Man et al., the overall mortality

and ICU admission rates were 8.6% and 4.0%, respectively [15]. Given the aging

population in Hong Kong, the impact of CAP in our ICU is clearly increasing.

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2 Study objectives

The primary objectives of the study were to identify the characteristics of the

septic patients with community acquired pneumonia living in the Mainland who

required our intensive care, and to assess their outcomes. The secondary objectives

were to assess the predictors for mortality and identify the distribution of causative

organisms.

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3 Methods

3.1 Study design

This was a retrospective study of critically ill patients with sepsis admitted to the

intensive care unit (ICU) of North District Hospital (NDH) in Hong Kong. The study

period was from 1st September 2008 to 31st August 2010. It was a 13-bed mixed

medical and surgical ICU. There are about 600 admissions per year. The research

protocol was approved by the Clinical Research Ethics Committee of the New

Territories East Cluster of the Hong Kong Hospital Authority.

3.2 Data collection

By using the admission books of our intensive care unit, all patients admitted

within the aforementioned period were looked at. The patient data from case notes

and computer records were screened carefully to ensure that these patients have taking

up residence in Mainland China. All these eligible patients were screened for infection

at ICU admission. Infection was defined on the basis of clinical history, clinical

symptoms, physical examination and laboratory findings suggesting the presence of

infection that justified the use of antimicrobial agents. Sepsis and sepsis-related

conditions were diagnosed according to the criteria proposed by the American College

of Chest Physicians / Society of Critical Care Medicine (ACCP / SCCM) consensus

[16]. Systemic inflammatory response syndrome (SIRS) was defined by the presence

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of abnormalities in at least 2 criteria among white cell count, body temperature, heart

rate, and respiratory rate. Sepsis was defined as systemic inflammatory response to

infection. Severe sepsis was associated with organ dysfunction, hypoperfusion

abnormality or sepsis induced hypotension in the absence of any obvious explanation

other than sepsis. Septic shock was defined as sepsis induced hypotension persisting

despite adequate fluid resuscitation along with the presence of hypoperfusion

abnormalities or organ dysfunction. Community acquired pneumonia (CAP) was

defined as an acute infection of lower respiratory tract that was associated with

symptoms of acute infection and the presence of acute infiltrate on a chest radiograph

in a patient who was not hospitalized for more than 14 days before the onset of

symptoms [17]. All eligible patients’ records, including the case notes and laboratory

findings, were studied in detail. In addition, by using the Clinical Management

System (CMS), the Clinical Data Analysis and Reporting System (CDARS), and the

Acute Physiology and Chronic Health Evaluation (APACHE) databases [18], all

useful information was assessed.

3.3 Inclusion and exclusion criteria

Patients were recruited if they were aged 18 or more and had a diagnosis of

sepsis upon ICU admission. If a patient was admitted more than once, only the data

from the first admission were analyzed. Patients were excluded if they had not taken

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residence in Mainland China. Those patients living in the Mainland China without

sepsis and those living in Hong Kong were not studied. Patients were also not

included if they had been transferred to other hospitals or if they had stayed in our

general ward for more than 48 hours.

3.4 Assessment

3.4.1 Demographic Data

Socio-demographic data including the patient’s age, sex, and smoking status

were recorded.

3.4.2 Clinical History

For each patient, the co-morbidities which included the presence of chronic

obstructive pulmonary disease (COPD), chronic respiratory insufficiency with or

without pulmonary hypertension, chronic kidney disease with or without dialysis,

diabetes, heart failure, liver cirrhosis, immunosuppression, and human

immunodeficiency virus (HIV) infection were recorded. On ICU admission, the data

about the intervention from the Mainland, including the history of hospitalization, the

use of antibiotics, and the use of mechanical ventilator and vasopressor during

transfer were considered. Besides, information about the intervention (mechanical

ventilator support and renal replacement therapy) in our ICU was noted. The source of

admission (medical, surgical, orthopedics, emergency departments, others) was also

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studied.

3.4.3 Disease Assessment

The severity of sepsis on ICU admission was categorized according to the ACCP

/ SCCM consensus into 3 groups: sepsis, severe sepsis and septic shock [16]. The

APACHE II score [18] and the Sepsis-related Organ Failure (SOFA) score [19] were

assessed. In addition, all eligible patients were classified according to their causes for

ICU support into cardiovascular, gastrointestinal, respiratory, neurological,

haematological, endocrine, renal, trauma, and others. All patients had a chest

radiograph in the emergency department and in the ICU. Images were assessed by

experienced intensivists and physicians. Additional data collected for all patients

included laboratory results (complete blood count, arterial blood gas, glucose, liver

and renal function) and microbiological results (sputum, endotracheal aspirate, and

bronchoalveolar lavage).

3.4.4 Outcomes

Main outcome measures were ICU length of stay, hospital length of stay, ICU

mortality, death within 28 days and hospital mortality. Predictors for the mortality

were assessed from the collected data.

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3.4.5 Patterns of Infection

The causative organisms were identified into gram positive (methicillin-sensitive

Staphylococcus aureus MSSA, methicillin-resistant Staphylococcus aureus MRSA,

Streptococcus pneumoniae, Enterococcus, others), gram negative (Escherichia Coli E.

Coli, Enterobacter, Proteus, Acinetobacter, Pseudomonas, Haemophilus influenzae,

Klebsiella, Moraxella catarrhalis, others), atypical (Legionella, Mycobacteria

tuberculosis, Pneumocystis), fungi and anaerobes. If the pathogens could not be

identified, the patients were labeled as only clinical diagnosis.

3.5 Statistical analyses

Statistical analysis was performed by using the Statistical Package for the Social

Sciences (SPSS, Windows version 17.0, Chicago, US). Results were expressed as

number and percentage, and median (interquartile range) where appropriate.

Comparisons of the characteristics of surviving and non-surviving septic patients were

performed using the chi-square test for the categorical variables. Continuous variables

were assessed by the 2 sample t-test. Univariate logistic regression analysis was

applied for assessing the predictors of mortality in patients with sepsis. A p value of

less than 0.05 was considered statistically significant. A multivariate logistic

regression was also applied.

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4 Results

4.1 Characteristics of Patients with Sepsis from Mainland China

During the two-year study period, a total of 1257 patients were screened. A total

of 1086 patients (86.4%) living in Hong Kong were admitted to our ICU. On the other

hand, 171 patients were admitted to our ICU with history of residence in the Mainland.

78 patients (6.2%) were admitted for other causes; such as myocardial infarction and

cerebrovascular accidents. 93 patients (7.4%) were admitted for infection. 51 (4.1%)

patients were admitted for CAP. 1 patient was excluded because of transfer to another

hospital. The remaining 42 patients were admitted for other infections. Figure 1

showed the flow diagram of enrolled patients.

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Figure 1. Flow Diagram of Enrolled Patients

 

Total ICU Admissions (n=1257)

Live in Hong Kong (n=1086)

Live in Mainland (n=171)

Non-Infected Patient (n=78)

Infected Patients (n=93)

Excluded (n=1)

Septic Shock (n=29)

Severe Sepsis (n=17)

Sepsis (n=4)

Other Infection (n=42)

Community Acquired Pneumonia (n=51)

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The median (interquartile range) age of patients with CAP was 66.5 (54.75-75)

years old. Pneumonia was more common in male admission (n=42, 84%) than in

female admission (n=8, 16%). More than half of these patients (n=30, 60%) were

chronic smokers. 24 (48%) and 26 (52%) patients were identified from the 1st and 2nd

year of study period respectively. The majority of these patients were admitted from

medical department (n=29, 58%) and emergency room (n=17, 34%). Nearly one

fourth of these patients (n=11, 22%) were admitted during the winter period. Nearly

half (n=22, 44%) of these patients had at least one co-morbidity. Diabetes (n=15, 30%)

and chronic respiratory insufficiency (n=11, 22%) were commonly found among these

patients. 4 (8%) patients had chronic kidney disease with or without renal replacement

before admission. HIV infection was known in 1 patient (2%). 6 (12%) patients

required mechanical ventilator support from the Mainland. In addition, 7 (14%)

patients required vasopressor support during the transfer. During the stay in our ICU,

the majority of patients (n=42, 84%) had mechanical ventilator support. Renal

replacement therapy support was provided for 12 patients (24%). Nearly one third of

these patients (n=16, 32%) were confused on ICU admission. 12 patients (24%) were

admitted with blood urea level greater than 7 mmol/L. Most of them (n=45, 90%)

were tachypnoeic with respiratory rate greater than 30 breaths per minute. The

characteristics of the 50 patients diagnosed with community acquired pneumonia were

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shown in Table 1.

Table 1: Characteristics of Patients with Sepsis.

Total No. of Patients 50 Age, Median (IQR), Years

66.5 (54.75-75)

Male (%) 42 (84) Smoker (%) 30 (60) Transfer from (%) Medical Ward 29 (58) Emergency Room 17 (34) Surgical Ward 3 (6) Orthopedic Ward 1 (2)

Admission During the Winter Period (%) 11 (22) No. of co-morbidities (%) None 28 (56) One or More 22 (44) Co-morbidities (%) Diabetes 15 (30) COPD / Chronic RespiratoryInsufficiency 11 (22) Chronic Kidney Disease 4 (8) Heart Failure 1 (2) Immunosuppresion 1 (2) Liver Cirrhosis 1 (2) HIV Infection 1 (2) Given Antibiotics in Mainland (%) 6 (12) Requiring Mechanical Ventilator Support During Transfer (%) 6 (12) Requiring Vasopressor Support During Transfer (%) 7 (14) Severity of Sepsis (%) Sepsis 4 (8) Severe Sepsis 17 (34) Septic Shock 29 (58) APACHE II Score (IQR) 24.5 (20-32) SOFA Score (IQR) 10.5 (7-14.5) Organ Dysfunction Systems Requiring ICU Support on Admission (%) Respiratory 45 (90) Cardiovascular 23 (46) Renal 5 (10) Neurological 2 (4) Metabolic 2 (4) Hematological 1 (2) Mechanical Ventilator Support in ICU Stay (%) 42 (84) Renal Replacement Therapy Support in ICU Stay (%) 12 (24) Confusion 16 (32) Urea >/= 7 mmol/L 12 (24) Respiratory Rate > / = 30 breath per minute 45 (90) Diastolic Blood Pressure < / = 60 mmHg 33 (65) Age > / = 65 27 (54) CURB Score (IQR) 3 (2-3)

Note: IQR interquartile range, COPD Chronic Obstructive Pulmonary Disease, HIV human Immunodeficiency Virus,

APACHE II Acute Physiology And Chronic Health Evaluation II score, SOFA Sequential Organ Failure Assessment score, ICU

Intensive Care Unit

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4.2 Disease Severity

These patients were categorized according to the aforementioned severity on

ICU admission. There were 4 (8%) patients with sepsis, 17 (34%) with severe sepsis,

and 29 (58%) with septic shock. The median (interquartile range) APACHE II and

SOFA scores recorded within 24 hours were 24.5 (20-32) and 10.5 (7-14.25),

respectively. The median (interquatile range) CURB-65 score was 3 (2-3). The most

common organ dysfunctions systems requiring ICU support on admission were

respiratory (90%) and cardiovascular (46%). Renal (10%) system was less common.

4.3 Outcomes

The overall hospital mortality rate was 48% (n=24). Patients with septic shock

had the highest mortality rate, which was 55.2% (n=16). The hospital mortality for

severe sepsis and sepsis were 41.2% (n=7) and 25% (n=1) respectively. The overall

28 day mortality rate was 38% (n=19). The overall ICU mortality rate was 26%

(n=13). The ICU mortality rate in patients with severe sepsis was 17.6% (n=3) and

31% (n=9) in those with septic shock. The median (interquatile range) duration of

ICU stay for screened patients was 6.5 days (3-13.5). The median (interquatile range)

hospital stay was 22 days (7.75-35.75). The outcomes of patients with previous

residence in Mainland China admitted to the intensive care unit in Hong Kong with

community-acquired pneumonia were listed in Table 2.

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Table 2: Outcome of Patients with Sepsis

All Sepsis Severe Sepsis Septic Shock

Died in ICU, (%) 13 (26) 1 (25) 3 (17.6) 9 (31)

Died at 28 Day, (%) 19 (38) 1 (25) 6 (35.3) 12 (41.4)

Died in Hospital, (%) 24 (48) 1 (25) 7 (41.2) 16 (55.2)

Duration of ICU Stay, Days, 6.5 (3-13.5) 5.5 (2.75-21.75) 7 (4.5-13.5) 6 (3-15.5)

Median LOS Hosp, Days, (IQR) 22(7.75-35.75) 18.5 (6.75-25.75) 22 (15.5-41.5) 22 (4.5-43)

Note: ICU Intensive Care Unit, IQR Interquartile range, LOS Length of Stay

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4.4 Patterns of Infection

The majority of patients (n=33, 66%) had clinical infection with identification of

pathogens. The remaining 17 (34%) patients had clinical infection without

identification of pathogens. Most of the organisms were found in the respiratory

specimen. 2 (4%) patients had positive blood cultures. Gram positive bacteria,

including Staphylococcus aureus and Streptococcus pneumoniae, were isolated from

30.6% of specimens. Gram negative bacteria were isolated from 52.8% of specimens.

Atypical pathogens, including Legionella pneumoniae, Mycobacteria tuberculosis and

Pneumocystitis carinii, were isolated from 16.6% of specimens. Among all specimens,

the most common organism was Streptococcus pneumoniae (19.4%). The less

commonly found bacteria were Haemophilius influenzae (13.8%) and Mycobacteria

tuberculosis (11.1%). Table 3 showed the distribution of pathogens.

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Table 3: Positive Microbiological Cultures where Pathogens Identified

Organisms Number Percentage (%)

Gram-Positive Bacteria

MSSA 4 11.1

Streptococcus Pneumonia 7 19.4

Enterococcus 0 0

Others 0 0

MRSA 0 0

Gram-Negative Bacteria

E. Coli 1 2.8

Klebsiella 3 8.3

Pseudomonas 1 2.8

Enterobacter 2 5.6

ESBL E. Coli 1 2.8

Haemophilius Influenza 5 13.8

ESBL Klebsiella 2 5.6

Acinetobacter 2 5.6

Moraxella Catarrhalis 2 5.6

Atypical Organisms

Mycobacterium Tuberculosis 4 11.1

Legionella 1 2.8

Pneumocystis 1 2.8

Note: MSSA Methicillin-Sensitive Staphylococcus Aureus, MRSA Methicillin-Resistant Staphylococcus Aureus, E. Coli

Escherichia Coli, ESBL Extended-Spectrum Beta-Lactamase

Percentages are calculated on the number of microbiologically documented infections

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4.5 Predictors of Mortality in Patients

From univariate logistic regression analysis, some factors were found as poor

prognostic factors. Confusion (OR 9.061; 95% CI, 2.691-30.503; p < 0.005) and the

blood urea level greater than 7 mmol/L (OR 8.571; 95% CI, 2.415-13.042; p < 0.005)

are associated with poor prognosis.

Some factors are marginally significant as predictors of mortality. These include

the use of vasopressor in China during transfer (OR 8.333; 95% CI, 1.313-52.891; p =

0.059) and mechanical ventilator support in our ICU (OR 8.474; 95% CI, 1.358-52.87;

p = 0.055).

Our analyses also confirmed that the APACHE II (p < 0.005) and CURB-65 (p <

0.005) scores were independent predictors for hospital death[20-22]. On the other

hand, the SOFA score (p = 0.056) was marginally significant risk factor of hospital

death.

Although more male patients were admitted when compared with female patients,

gender (47.6% vs 50%, p = 0.902) was not poor prognostic factor for mortality.

All the preceding variables from the univariate analysis were modeled in the

multivariate analysis. Factors associated with increased mortality in our patients

included APACHE II and CURB-65 scores.

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5 Discussion

The overall incidence rate of CAP varies from 1.62 cases to 6.11 cases per 1000

persons per year in different studies. The incidence rate increases by age and is higher

in males than in females. It was also more commonly found in winter season. The rate

of hospital admission was 61.4% [10,23]. In our study, among 171 patients with

previous residence in Mainland, 93 of them were admitted to our ICU for infections.

More than half of these patients (n=51, 54.8%) are due to community acquired

pneumonia. Hospital acquired infections (n=18, 19.3%) and intra-abdominal

infections (n=14, 15.1%) are also common. There are multiple reasons for the high

proportion of patients admitted for infections. Firstly, few Mainland patients were

admitted for reasons other than sepsis, such as scheduled post operative ICU care.

Secondly, nosocomial infections are commonly found in these patients. These

infections can occur in patients during the hospital stay in the Mainland. Nosocomial

infections usually prolong hospital stay and consequently make patients transfer back

to ICU in Hong Kong. Their choice of transfer involves financial consideration,

family ties in Hong Kong and a lack of confidence in the Mainland medical services.

Many studies concluded that the incidence of CAP requiring ICU care is

increasing annually [10,24]. In our study, the number of patients was also found to be

increasing annually (n=23 vs n=27). The reasons for increasing incidence included the

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increasing number of Hong Kong people residing in Shenzhen, aging of people and

increasing number of immunocompromised patients. However, the accuracy of our

result may be limited by our short period of study.

Age is always an important factor in determining the risk of sepsis and mortality

rate. A previous study carried out in the United States showed that the elderly have

both an increased incidence of pneumonia and an increased mortality, compared with

the younger population [25]. The mortality of CAP was 4.5% in those aged 18 to 44

years. However, the mortality rate increased to 12.5% in those over age 65 [26].

Higher mortality was related to co-morbid illness and impaired immunologic response

to infection [27].Our results showed that the median age of patients was 66.5 years

old. However, the trend of increasing mortality among the elderly was not obvious in

our study. The reasons included earlier death of elderly patients before transfer, and

limitation of intensive care for the elderly either imposed by the patient or the

physician. With an aging population and greater life expectancy, it is likely that there

will be an increasing incidence of CAP with a previous residence in the Mainland.

A previous study showed that increased risk of CAP was associated with

smoking, previous respiratory infection and chronic bronchitis [28].In patients with

chronic illnesses such as COPD, diabetes, and alcoholism, Klebsiella pneumoniae has

a significant mortality [29].In our study, although there were more smokers than

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non-smokers, smoking was not associated with increased mortality.

According to a worldwide observational study [30], renal failure is commonly

found in patients with CAP who needed ICU treatment. It was also associated with

greater risk for death. In our study, nearly one fourth of patients (n=12, 24%) received

renal replacement therapy support. We found that their renal failure might be a result

of sepsis. Although there was no significant difference in the mortality of patients, use

of renal replacement therapy was associated with higher chance of death.

The SOFA score characterized the degree of dysfunction or failure by organ

system [19].The median SOFA core in our study was 10.5.Similarly, APACHE II

scoring system is widely used and accepted in predicting ICU outcomes [31]. The

median APACHE II score in our study was 24.5. In addition, the median CURB-65

score in our study was 3. A previous study showed that both APACHE II and

CURB-65 scores perform similarly in predicting 28 day and in hospital mortality of

CAP patients [32].Our study confirmed that higher values of these organ dysfunction

scores (APACHE II, p < 0.005; CURB-65, p < 0.005) remained as a strong

independent risk factor of mortality in critically ill patients. Therefore, these scores

should be used for stratification of patients with CAP from the Mainland. Furthermore,

CURB-65 is simpler, and thus, may provide more efficient assessment in these

patients.

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Although there was numerous close monitoring, new antibiotics and international

guidelines for the management of CAP, the mortality was still high

[17].Approximately 10% to 36% of patients with CAP who need hospitalization

require ICU treatment [33].The reported mortality of CAP varied from less than 5%

among outpatients to about 12% among all hospitalized CAP patients, and even over

30% among those admitted to the ICU.[10,24]. In our study, a positive correlation

between mortality and sepsis severity was shown. The ICU mortality rate of our

studied patients was 26%, which was similar to previous study[24]. Besides, our

median length of ICU stay was 6.5 days, which was also similar to the previous study

[34].The difference between ICU mortality rate (26%) and hospital mortality rate

(48%) was obvious. 30% of discharged patients from ICU died before discharge from

hospital. These differences could be explained by discharge from ICU for palliative

care or premature discharge to general ward. As a result, patients with previous

residence in the Mainland admitted for CAP may have greater benefit if longer ICU

stay could be provided.

Positive microbiological detection rate in CAP ranges between 2.1% and 75%.

The reasons for these differences include the use of diagnostic tests and the

widespread use of antibiotics in private practice [35-37].In our study, the rate of

documented infection was 66% (n=33) among our patients, a figure comparable as

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reported in other studies [38].This result may be explained by early and adequate

sampling of cultures before the use of antibiotics.

In Hong Kong, the aetiologic diagnosis of CAP was made in 41% cases [39]. In

Japan, 61% of pathogens were found in patients with CAP. The most commonly

identified pathogens included Streptococcus pneumoniae (23%), Haemophilus

influenza (7%), and Mycoplasma pneumonia (5%) [40].However, the identification of

pathogens is different among patients receiving treatment in outpatient, general ward

and ICU. In European ICUs (outside of the United Kingdom), the identification of

Legionella was lower. On the other hand, the identification of gram negative bacilli

was higher (9%) although Streptococcus pneumoniae was still most commonly

found[17].In the United States, for CAP patients with septic shock, the most

commonly identified pathogens were Streptococcus pneumoniae (19%),

Staphylococcus aureus (18%), Haemophilus influenzae (14%), Klebsiella pneumoniae

(11%), and Pseudomonas aeruginosa (7%) [41].In Hong Kong, Streptococcus

pneumoniae remains the most common pathogen in CAP [42].Similarly, our study

showed that Streptococcus pneumoniae is the most commonly found organism.

Reduced susceptibility of Streptococcus pneumoniae to penicillin and resistance to

fluoroquinolone have been increasingly seen in our community. The prevalence of

resistance was higher in elderly patients and patients with COPD [43,44]. Surprisingly,

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all of them had penicillin susceptible strains. The result may be explained by small

sample size.

Falguera M [45] reported that the overall rates of bacteremia were between 12%

and 16% in their cohort study. However, in our study, only 2 patients (4%) had

positive blood cultures. Because our study was retrospective, one possible reason for

lower percentage of positive blood cultures could be related to the use of antibiotics in

the Mainland even without hospitalization. Streptococcus pneumoniae remained the

most common causative pathogens which can be found in the blood culture [46].In

our cases, both patients had positive blood cultures for Streptococcus pneumoniae.

The tuberculosis may masquerade as CAP in about 12% of patients in Hong

Kong [39]. Ryu et al. [47] reported that patients with respiratory failure caused by

pulmonary tuberculosis necessitating mechanical ventilation had a high mortality rate

(59%) and poor prognosis. In our study, Mycobacteria tuberculosis was also an

important cause of CAP. They all required mechanical ventilator support owing to

respiratory failure. 3 patients (75%) were dead. Therefore, pulmonary tuberculosis

should also be considered in the diagnosis, and respiratory specimens should be

examined routinely for acid fast bacilli in those patients living in the Mainland.

In Germany, Von Baum H [48] reported that Legionella pneumonia was

diagnosed in about 3.8% of patients. In Hong Kong, there were 19 cases of

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Legionnaires’ disease from 1994 to 2002 [49]. All of these patients had symptoms of

pneumonia. More than half of them had positive urine antigen test (50%-75%). 58%

of cases required intensive care during hospitalization. In addition, the number is

increasing in these few years. There were 38 reportable cases from 2005 to 2007. In

our study, the only patient with Legionella pneumonia had history of going wet sauna

in Shenzhen. Thus, a high index of suspicion is important for all patients.

Staphylococcus aureus pneumonia (19%), following Streptococcus pneumonia

(48%), is commonly seen in elderly patients and in patients after influenza infection

[50]. Patients with Community Acquired Methicillin Resistant Staphylococcus Aureus

(CA-MRSA) infection usually present with skin and soft tissue infections. Outbreak

of CA-MRSA pneumonia was reported in overseas [51].In our study, all patients with

Staphylococcus aureus pneumonia were methicillin sensitive.

On the other hand, the rate of extended-spectrum beta-lactamases (ESBL)

producing strains among E. coli and Klebsiella pneumoniae was 42.8% in our study.

In the Mainland, the rate of ESBL producing E. coli in ICU ranged between 28.6%

and 45.7% [52,53]. There are several reasons contributing to the high incidence of

ESBL producing organisms among these Mainland patients who required our ICU

care. Firstly, an increasing and unnecessary exposure to antibiotics in the Mainland,

especially third generation cephalosporin, is an important cause. In the Mainland,

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more than 100 domestic manufactures produced cefotaxime and ceftriaxone at a very

cheap price, causing a widespread use [53].Although there are new prescription

guidelines were issued by the Chinese Ministry of Health in 2004 to restrict the use of

antibiotics, the guidelines are not being followed effectively, according to the head of

China’s National Antibiotics Resistance Investigation Network [54].Secondly,

vulnerability to infection from immunocompromised status is another cause.

Furthermore, high prevalence of carriage of ESBL producing organisms in the

Mainland community can increase the incidence of resistant infection. Close contact

with poor hygiene practice in household settings might contribute to ESBL

dissemination in the Mainland community. A recently published study by Ho et al. [55]

showed that history of prolonged residence in the Mainland was significantly

associated with carriage of ESBL producing organisms. Thus, the problem of

emerging resistance bacteria raised our concerns in treating patients who live in the

Mainland. Our findings also have implications for the choice of empirical therapy in

enterobacteriaceae infection.

There are several limitations to our study. Despite many Mainland patients being

admitted into our intensive care unit, this study was on a single-centre basis, and thus

the results may not be generalized to other centres in Hong Kong. Besides, no data on

long term follow up was available beyond hospital discharge. We could not assess

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whether the patients had a reduction of life expectancy or not. Furthermore, only

patients treated in ICU was focused in our study. The characteristics of patients with

CAP treated in general ward were not assessed. Finally, use of antibiotics was not

measured in our study, and thus the effectiveness of antibiotics could not be assessed.

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6 Conclusion

In conclusion, despite the aforementioned limitations, our findings emphasize the

importance of early care for those critically ill patients with a previous residence in

Mainland China requiring intensive care for community acquired pneumonia. Also,

we observe that APACHE II and CURB-65 scores are good severity assessment tools

to stratify patients from the Mainland. Furthermore, an increase in the number of

patients residing the Mainland is expected in the near future. In view of this, better

understandings of the characteristics of these patients are required, and continued

research efforts are mandatory in order to optimize patient-centered outcomes.

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