Emergency. 2017; 5 (1): e13

OR I G I N A L RE S E A RC H

Deep Vein Thrombosis among Intensive Care Unit Pa-
tients; an Epidemiologic Study
MirMohammad Miri1, Reza Goharani1, Mohammad Sistanizad1,2∗

1. Department of Critical Care, Imam Hossein Medical and Educational Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

2. Department of Clinical Pharmacy, Faculty of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Received: March 2016; Accepted: Jun 2016; Published online: 9 January 2017

Abstract: Introduction: Deep vein thrombosis (DVT) is a major cause of morbidity and mortality in intensive care unit
(ICU) patients despite use of prophylactic anticoagulant therapy. The aim of the present study was to deter-
mine the incidence of DVT among medical and surgical ICU patients. Methods: In this cross sectional study,
patients older than 18 years who were hospitalized in the ICU of Imam Hossein educational Hospital, Tehran,
Iran, for ≥ 2 days, during August 2008 to July 2011 were evaluated regarding DVT incidence. Demographic data,
comorbidities, acute physiology and chronic health evaluation (APACHE) II scores, ICU length of stay, type of
DVT prophylaxis, and patient outcomes were analyzed using SPSS 19. Results: Out of the 1387 reviewed patient
files, 500 (36.04%) patients had been classified as potential DVT cases. DVT occurred in 3.5% of them with the
mean age of 60 ± 18 years (62.5% male) and mortality rate of 27.1%. Significant independent risk factors of DVT
incidence were age (p = 0.02) and length of ICU stay (p = 0.01). Conclusion: The results of this study showed the
3.5% incidence of DVT in ICU admitted patients. Longer ICU stay and older age were independent risk factors
of DVT development.

Keywords: APACHE; ultrasonography, Doppler; venous thrombosis; intensive care units

© Copyright (2017) Shahid Beheshti University of Medical Sciences

Cite this article as: Haji Aghajani M, Haddadi M, Saadat S. Deep Vein Thrombosis among Intensive Care Unit Patients; an Epidemiologic

Study. Emergency. 2017; 5 (1): e13.

1. Introduction

Venous thromboembolism (VTE) is the third most com-

mon cardiovascular disorder after myocardial infarction and

stroke (1). The rate of morbidity and mortality associated

with thromboembolic events is high, with 28-day fatality

rates reported to be 9% for deep vein thrombosis (DVT) and

15% for pulmonary embolism (PE) (2). The causes of DVT

may be acquired, inherited or a combination of both (3). The

diagnosis and treatment of DVT are challenging and expen-

sive (3). DVT can complicate the course of a disease, but

may also be encountered in the absence of precipitating fac-

tors. While long-term morbidity due to post-thrombotic syn-

drome is common, and can be substantial, the major com-

plication is embolization of the thrombus to the lung (4). Ex-

∗Corresponding Author: Mohammad Sistanizad; Department of Critical
Care, Imam Hossein Hospital, Shahid Madani Avenue, Imam Hossein Square,
Tehran, Iran. Tel: +98-9122784895; Fax: +98-2188200087; Email: sis-
tanizadm@sbmu.ac.ir

tensive epidemiological studies of patients with thromboem-

bolism have identified several factors that enhance the risk

of DVT development. These include surgery, age, gender,

heart failure, history of previous thromboembolism, direct

trauma to the leg, use of oral contraceptives, and limb weak-

ness (3, 5). The majority of intensive care unit (ICU) pa-

tients have one or more risk factors for DVT (3). These pa-

tients are further predisposed to DVT during their ICU stay

due to prolonged immobilization, sepsis, and vascular injury

from indwelling central venous catheters or other invasive

interventions (6). The incidence of reported DVT is likely to

vary across populations, based on baseline characteristics of

patients, post-ICU admission events and patient condition,

clinical suspicion for VTE, the scheduling and methods of

VTE screening, and prophylactic interventions. A retrospec-

tive study on ICU patients undergoing color-flow Doppler

sonography for DVT screening has shown an estimated inci-

dence of 33% (5). Cross-sectional studies of medical and sur-

gical ICU patients have shown that approximately 10% have

proximal DVT on admission to the ICU (7, 8). One study re-

ports a VTE rate of 9 per 10,000 hospital admissions in an Ira-

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M. Miri et al. 2

nian population (9). Based on the above mentioned, the aim

of the present study was to determine the incidence of DVT

among medical and surgical ICU patients.

2. Methods

2.1. Study design and setting

In this retrospective cross sectional study, patients older than

18 years who were hospitalized in ICU of Imam Hossein ed-

ucational Hospital, Tehran, Iran, for ≥ 2 days were evalu-
ated. The study was conducted in accordance with the prin-

ciples of the 18th world medical assembly (Helsinki, 1964)

and all subsequent amendments. The study received ethi-

cal approval from Shahid Beheshti University of Medical Sci-

ences.

2.2. Participants

All consecutive patients admitted to the ICU for the first time,

between August 2008 and July 2011, were considered for in-

clusion in the study. Patients were excluded if they either

had a documented DVT/PE before or within 48 hours of ICU

admission or died or had missing or incomplete data dur-

ing that time period. In this 21 bed ICU, a large variety of

medical, surgical, orthopedics, neurosurgical, trauma, car-

diac surgery and obstetrics and gynecology patients are man-

aged. The ICU care is directed and run by trained intensivists

in a semi-closed fashion with an average patient length of

stay of 8 days.

2.3. Data collection

We collected data from patients electronic medical records

and a regional ICU database. For each patient with clinically

and Doppler proven DVT, key demographic and clinical char-

acteristics including age, sex, diagnosis on admission, Acute

Physiology and Chronic Health Evaluation II (APACHE II)

score, VTE prophylaxis regimen, duration of mechanical ven-

tilation, length of ICU stay and patient’s outcome (discharge

or death) were collected. To provide a uniform and unbi-

ased assessment of Doppler proven DVT, one research asso-

ciate, who was a vascular surgeon, performed the Doppler

examination for all patients potentially having DVT and was

blinded to the patients’ history and clinical status. All clinical

decisions were made at the discretion of the ICU team. Po-

tentially having DVT was defined as International ClassiFica-

tion of Diseases, 9th Revision, Clinical ModiFication (ICD-9-

CM) codes (453.40, 453.41, 453.42, 453.80, and 453.90).

2.4. Statistical Analysis

All statistical analyses were performed using SPSS version 19.

Continuous data were expressed as mean and standard de-

viation for normally distributed data or median and inter-

quartile range for non-normally distributed data. Categori-

cal data were summarized as counts and percentages. Con-

tinuous data were contrasted between groups using the t-test

or rank test as appropriate. Categorical data were contrasted

using the chi-squared test. Multiple logistic regressions were

used to identify independent risk factors associated with the

presence of DVT. A p value less than 0.05 was considered sta-

tistically significant.

3. Results:

Out of the 1387 reviewed patient files during the study pe-

riod, 500 (36.04%) patients had been diagnosed as poten-

tially having DVT and underwent venous color Doppler ul-

trasonography. Table 1 shows the baseline characteristics of

patients. Based on the results of ultrasonography, 48 (3.5%)

cases had DVT (62.5 % male). Their mean age was 60 ± 18
years and they had the mean APACHE II score of 16.3±5.1 and
ICU mortality rate of 27.1%. Table 2 summarized character-

istics of these patients. None of the patients had bleeding or

treatment-related complications during the study. Univari-

ate analysis showed significant correlation of age (p = 0.02)

and length of ICU stay with incidence of DVT (p = 0.01) (Table

2). Based on multivariate analysis, only a longer ICU stay sig-

nificantly associated with DVT incidence (OR: 1.07 per each

day of ICU stay; 95% CI: 1.03-1.22; p value, 0.01).

4. Discussion:

The results of the present study revealed 3.5 % incidence

of DVT in ICU admitted patients of Imam Hossein Hospi-

tal. DVT is difficult to diagnose because of the poor sensitiv-

ity and specificity of clinical symptoms and signs (10). DVT

usually originates in the calf veins where the risk of subse-

quent complications is low. The classic symptoms and signs

are due to venous obstruction and an inflammatory response

in the affected area. However, the majority of DVT cases re-

main clinically silent (11). The diagnostic gold standard tools

for DVT and PE were venography and pulmonary angiogra-

phy, both of which are invasive and costly. Doppler sonog-

raphy examination has emerged as the noninvasive imaging

method of choice for evaluation of DVT. It has the added abil-

ity of being able to visualize other pathologies mimicking ve-

nous obstruction (3). The incidence of DVT in this survey is

lower than that reported in Chinese (19%) and Caucasian (28-

32%) medical ICU patients not receiving prophylaxis (12-14).

Many factors could contribute to this relatively low incidence

in comparison to other countries (15). There is an association

between age and incidence of DVT (16). The Iranian pop-

ulation, like other Middle Eastern countries, is very young;

while about 43% of the Western population are 40 years and

above, only 18% of Iranians are in this age range (17). How-

ever, with increasing age of the Iranian population, DVT will

probably become a growing public health problem. On the

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3 Emergency. 2017; 5 (1): e13

Table 1: Baseline characteristics of studied patients

Parameters N (%) APACHE II DVT n (%) Incidence Rate*
Age (year)
≤40 492(35.47) 13.7 ± 4.7 10 (2.03) 1.64
46 - 65 391(28.19) 14.4 ± 5 16(4.09) 3.07
≥66 504(36.34) 18.9 ± 4.2 22(4.37) 3.04
Sex
Male 807(58.18) 17 ± 5.4 30(3.72) 2.84
Female 580(41.82) 15.2 ± 4.5 18(3.10) 2.26
ICU stay (day)
âL’d’7 722(52.05) 15.6 ± 4.7 8(1.11) 2.45
8-28 500(36.05) 16.4 ± 5.9 24(4.80) 3.33
âL’ě29 165(11.90) 16.5 ± 4.2 16(9.70) 1.99
Year
2008 263(18.96) 13.1 ± 6.5 7(2.66) 1.92
2009 476(34.32) 16.6 ± 4.5 21(4.41) 3.08
2010 514(37.06) 16.1 ± 5.4 14(2.72) 2.15
2011 134(9.66) 19.5 ± 3 6(4.48) 3.83
* Rate per 1000 person days; APACHE II: Acute Physiology and Chronic Health Evaluation II; DVT: deep vein thrombosis;
ICU: intensive care unit; data were presented as mean Âś standard deviation or number and percentage.

Table 2: Characteristics of cases potentially having deep vein thrombosis (DVT) among intensive care unit (ICU) admitted patients

Variable
Color Doppler ultrasound for DVT P Value

Negative (n=452) Positive (n=48)
Age (year) 51 ± 19 60 ± 18 0.02
Gender (male) 259 (57.3%) 30 (62.5%) 0.6
APACHE II 14.2 ± 5.4 16.1 ± 4.8 0.2
ICU stay (Day) 21 ± 31 30 ± 30 0.01
Diagnoses
Acute Hemorrhagic Stroke 82 (18.1%) 10 (20.8%) 0.7
Multiple Trauma 124 (27.5 %) 12 (25%) 0.8
Respiratory Distress 49 (10.8%) 6 (12.5%) 0.7
Acute Abdomen 45 (9.9%) 5 (10.4%) 0.8
Acute Ischemic Stroke 48 (10.6 %) 5 (10.4%) 0.9
Cancer 23 (5.1%) 3 (6.2%) 0.7
Sepsis 36 (8%) 3 (6.3%) 0.7
Loss of consciousness 24 (5.3%) 1 (2.1%) 0.6
Others 21(4.7%) 3 (6.2%) 0.7
Type of DVT Prophylaxis
LMWH 137 (30.3%) 19 (39.6%) 0.5
Heparin 191 (42.2%) 12 (25%) 0.05
IPC and GCS 124 (27.5%) 17 (35.4%) 0.5
ICU Mortality 88 (19.5%) 13 (27.1%) 0.5
APACHE II: Acute Physiology and Chronic Health Evaluation II; LMWH: low molecular weight heparin;
IPC: Intermittent Pneumatic Compression; GCS: graduated compression stockings; DVT: deep vein thrombosis,
ICU: intensive care unit; data were presented as mean ± standard deviation or number and percentage.

other hand, it is likely that increased physician awareness

of DVT risk factors and increased utilization of noninvasive

imaging have led to a higher diagnosis rate (18). DVT inci-

dence increases rapidly with age in an apparently linear form

suggesting a constant incidence and cumulative prevalence,

especially in those older than 65 years (1). Old age is one of

the risk factors in patients with DVT (16). The mean age of

patients was almost 60 years, which was within the age range

of people prone to venous thromboembolism (over 40 years

of age) (1). In addition, consistent with previous studies,

which have shown DVT to be more common among men (9),

approximately 62.5% of our DVT patients were male. How-

ever, length of ICU stay was the most significant factor as-

sociated with the presence of DVT. The interpretation is that

in many patients, DVT developed after they were admitted

to the ICU and the risk of DVT increased with a longer ICU

stay. The mean APACHE II score was 16.3 ± 5.1 and ICU
mortality rate was 27.1% (13 in the 48 patients with DVT).

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M. Miri et al. 4

The in-hospital mortality rate, observed in this study, ap-

pears similar to those reported from other studies in major

academic health centers (2, 19). It is not clear whether this

increase in fatality should be attributed to the accompanying

risk factors, or to the severity of DVT (proximal), most likely

both play an important role (20). We suggest that prophy-

laxis be administered to those with three or more risk factors.

The mortality rate of DVT has a strong association with other

risk factors such as, cardiovascular disease, cancer, states fol-

lowing surgery or trauma (2, 21). Evidence-based consen-

sus guidelines for VTE prophylaxis have been available since

a long time ago (22). The American College of chest physi-

cians (ACCP) guidelines recommend prophylaxis for patients

at moderate-to-high risk of VTE, using mechanical prophy-

laxis and/or pharmacological prophylaxis (19, 23). Despite

the recommendations of international guidelines, physicians

often do not prescribe prophylaxis therapy in high-risk situ-

ations (24). Means to improve DVT prophylaxis should in-

clude increasing physicians awareness through training and

the implementation of procedures to assess DVT risk during

hospitalization, along with the application of evidence-based

guidelines for DVT prophylaxis and treatment in both med-

ical and surgical patients (23). There are no local guidelines

for DVT prevention in Iran. Considering that DVT is a serious

clinical condition that may lead to patient death, we recom-

mend the assessment of DVT risk (using a risk model assess-

ment form, locally adapted) for all hospitalized patients on

admission and during hospitalization.

5. Limitations:

The main limitation of our study is its retrospective and sin-

gle center design. Prospective multicenter studies are recom-

mended.

6. Conclusion:

The results of this study showed the 3.5% incidence of DVT

in ICU admitted patients of Imam Hossein Hospital, Tehran,

Iran. Longer ICU stay and older age were independent risk

factors of DVT development.

7. Appendix

7.1. Acknowledgements

None.

7.2. Authors contribution

All authors passed four criteria for authorship contribution

based on recommendations of the International Committee

of Medical Journal Editors.

7.3. Conflict of interest

None.

7.4. Funding

This research has been supported by a grant by Sanofi Aventis

Company.

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	Introduction
	Methods
	Results:
	Discussion:
	Limitations:
	Conclusion:
	Appendix
	References