Risk factor analysis for early development of calf muscular vein thrombosis after thoracic surgery:a prospective observational study

doi:10.21203/rs.3.rs-3421665/v1

Background: Venous thromboembolism is a common complication after thoracic surgery. The early development of calf muscular vein thrombosis (CMVT) after thoracic surgery is not well understood. The purpose of our study was to find the incidence and risk factors of early CMVT after thoracic surgery.

Methods: We performed a prospective observational study in patients who received thoracic surgery from December 2021 to January 2023. The patients were assigned to either the CMVT or non-CMVT group based on their early postoperative lower extremity venous Doppler ultrasound results. The clinical characteristics of CMVT patients and non-CMVT patients would be compared and analyzed.Multivariate logistic regression analysis was conducted to identify independent risk factors associated with CMVT development. The area under the receiver operating characteristic curve was also calculated.

Results: A total of 745 patients were included in the final analysis, with 185 (24.8%) and 560 (75.2%) patients in the CMVT and non-CMVT groups, respectively. In the CMVT group, 7 (3.8%) and 87 (47.1%) patients had concurrent proximal deep vein thrombosis and bilateral lower extremity thrombosis, respectively.Multivariate logistic regression analysis showed that age (OR = 1.092, 95% CI = 1.064–1.120, P = 0.000), Caprini score (moderate and high risks) (OR = 2.029, 95% CI = 1.276–3.227, P= 0.003), non-anticoagulation (OR = 1.859, 95% CI = 1.147–3.013, P = 0.012), operative duration >135 minutes (OR = 1.697, 95% CI = 1.135–2.538, P= 0.010), and postoperative day 1 D-dimer level (OR = 1.342, 95% CI = 1.232–1.462, P = 0.000) were independent risk factors for early postoperative CMVT. The receiver operating characteristic curve analysis showed that the areas under the curve for age and postoperative day 1 D-dimer were 0.715 (cut off value of 58.5) and 0.781 (cut off value of 1.445), respectively.

Conclusions: The incidence of early CMVT after thoracic surgery was 24.8%. Nearly half of the CMVT patients had bilateral involvement. The risk of early CMVT was reduced after perioperative anticoagulation prophylaxis. In addition, older age, moderate and high Caprini risk score, operative time >135 minutes, and high postoperative day 1 D-dimer level were independent risk factors for the early development of CMVT after thoracic surgery.

Calf muscular vein thrombosis

Thoracic surgery

Early postoperative period

Perioperative anticoagulation

Risk factors

Calf muscular vein thrombosis (CMVT) usually occurs in the distal calf, with limited distribution. It is a form of peripheral deep vein thrombosis (DVT). Clinical presentations of CMVT are usually atypical, and could easily be misdiagnosed in clinical practice [1]. Compared with other veins in the lower extremity, the veins in the calf muscles are more likely to develop thrombosis due to their extensive branches, small diameters, thin walls, few venous valves, and slow blood flow [2]. A previous study reported that in certain populations up to 91% of patients with DVT could have CMVT [3]. Although CMVT gradually disappears in most cases, there is a proportion of cases where CMVT progresses to DVT [4] or even pulmonary embolism (PE) [5, 6]. Venous thromboembolism events (VTE), including PE and DVT, are a major cause of morbidity after cancer surgery and can also be a cause of surgery-related mortality [7]. Thoracic surgical patients such as those with lung and esophageal cancer are at a greater risk of postoperative VTE and related mortality compared with other cancer surgery [8]. The postoperative VTE mortality rate among lung and esophageal cancer patients can reach 20% and 14%, respectively [9], and guidelines recommend the use of low-molecular-weight heparin to prevent VTE after cancer surgery [10]. However, previous research has grouped CMVT with other forms of DVT [11], and there have been very few studies dedicated to investigating CMVT after thoracic surgery. Therefore, we performed the present prospective observational study on CMVT patients, with the aim to determine the incidence and the risk factors associated with early development of CMVT after thoracic surgery. Specially, we investigated whether perioperative anticoagulation prophylaxis could decrease the occurrence of early postoperative CMVT.

Study design and participants

This was a prospective observational study in patients who received thoracic surgery at the Department of Thoracic Surgery of the Binzhou Medical University Hospital from December 2021 to January 2023. Patients who underwent thoracic surgery for thoracic diseases were included in the study. The thoracic diseases included lung cancer, benign lung diseases, esophageal and gastric cardia cancer, and mediastinal and other thoracic diseases. The exclusion criteria were as follows: 1) previous history of venous thrombosis or lower extremity thrombosis revealed during the preoperative examinations; 2) thoracic trauma surgery and emergency surgery; 3) surgery not performed in the lateral decubital position; 4) history of great saphenous vein surgery; 5) extensive pleural cavity adhesions; 6) Doppler ultrasound examination not performed; and 7) Using antithrombotic drugs before admission (low molecular weight heparin and others).This study was approved by the Ethics Committee of the Binzhou Medical University Hospital(No.2023LW-55).Written consent was obtained from all patients before enrollment.

Study protocol

Baseline information, including age, gender, height, weight, hypertension, diabetes, coronary artery disease, cerebrovascular disease, and primary thoracic disorder (benign versus malignant), was recorded. The modified Caprini score was used to assess the thrombosis risk, with 0–4, 5–8, and ≥ 9 suggesting low, moderate, and high risks, respectively (Table 1) [12]. Doppler ultrasound was performed to rule out preoperative venous thrombosis in the lower extremities. Venous thrombosis was diagnosed when the vein was not fully compressible and had no blood flow. All of the patients received thoracotomy or thoracoscopic surgery under general anesthesia and intratracheal intubation.

The preoperative fasting period, type of thoracic surgery (thoracotomy or thoracoscopic operation), side of operation, frequency of intraoperative muscle relaxant administration, operative duration, and serum D-dimer level (preoperative and postoperative day 1, normal level ≤ 0.5 µg/mL) were documented. The operative duration was defined as the length of the operation from the initiation of skin incision to the incision closure. The thoracotomy included patients who received thoracoscopic surgery initially, which was converted to thoracotomy later.

The perioperative anticoagulation prophylaxis was based on the Chinese expert consensus [13]. Because of the different treatment teams in the department, there were three groups as follows: 1) patients received preoperative and postoperative anticoagulation prophylaxis with subcutaneous injection of enoxaparin 4,000 units 12 hours before and 12 hours after the surgery; 2) patients received postoperative anticoagulation prophylaxis with subcutaneous injection of enoxaparin 4,000 units 12 hours after the surgery; and 3) patients did not receive any perioperative anticoagulation prophylaxis.

Postoperative measurements and group assignments

Within 24 hours after the thoracic surgery, Doppler ultrasound was performed to evaluate CMVT based on the diagnostic criteria described above. In patients with chest pain, dyspnea, or low oxygen saturation, contrast-enhanced computed tomography scan was performed to rule out the possibility of pulmonary embolism. In patients with confirmed postoperative CMVT, vascular interventional surgeons were consulted to determine the anticoagulation treatment regimen. Patients were divided into a CMVT and a non-CMVT group, based on the early postoperative lower extremity venous Doppler ultrasound results.

Statistical analysis

The statistical analyses were conducted in SPSS 22.0 (SPSS, IBM, New York, United States). Continuous data were presented as mean ± standard deviation (Mean ± SD). The differences between two groups were analyzed by independent-samples t test or Mann–Whitney U test. Categorical data were described by the numbers with percentages, and intergroup comparisons were performed by chi-square test or Fisher exact test. Univariate and multivariate logistic regression analyses were conducted to evaluate the independent risk factors associated with CMVT. Odds ratios (OR) and 95% confidence intervals (CI) were reported. The area under the curve (AUC) of the independent risk factors was calculated from the receiver operating characteristic (ROC) curve, and the cutoff values were determined by Youden’s index. Youden’s index was calculated as (Sensitivity＋1－Specificity). AUC of 0.5–0.7, 0.7–0.9, and > 0.9 was considered low, medium, and high accuracy, respectively. A P value < 0.05 was considered statistically significantly different.

Clinical characteristics of the study participants

A total of 862 patients underwent thoracic surgery during the study period. Of them, 27, 22, 19, 5, 12 and 8 patients had preoperative venous thrombosis, trauma and emergency surgery, non-lateral position during surgery, history of great saphenous vein surgery, using antithrombotic drugs before admission and extensive pleural cavity adhesions, respectively. In addition, 18 and 6 patients did not receive preoperative and postoperative Doppler ultrasound examinations, respectively. Finally, 745 patients were included in the present study (Fig. 1), with lung cancer, benign lung diseases, esophageal and gastric cardia cancer, and mediastinal and other chest diseases in 517, 108, 60, and 60 patients, respectively. The CMVT group had 185 (24.8%) patients, and the non-CMVT group had 560 (75.2%) patients.

The clinical characteristics of these two groups are shown in Table 2. There were no statistically significant differences between the two groups in terms of gender, body mass index, diabetes, preoperative fasting period, surgery side, and primary disorders (P > 0.05). In contrast, there were significant differences between the groups in terms of age, hypertension, cardiovascular disease, Caprini score, anticoagulation prophylaxis, preoperative D-dimer level, type of thoracic surgery, operative duration, frequency of intraoperative muscle relaxant administration, and postoperative day 1 D-dimer level (P < 0.05).

Incidence of CMVT after thoracic surgery

Of the 745 study participants, 185 (24.8%) developed postoperative CMVT. None of the patients with CMVT had clinical symptoms of thrombosis. Of the patients with CMVT, seven (3.8%) had concurrent proximal DVT (two in the left peroneal vein, two in the left posterior tibial vein, one in the right peroneal vein, one in the right posterior tibial vein, and one in the right femoral vein). There was no isolated proximal DVT or symptomatic pulmonary embolism. Of the 517 patients with lung cancer, 117 (22.6%) patients had CMVT, whereas only 20 (18.5%) patients with benign lung diseases had CMVT. In 60 patients with esophageal and gastric cardia cancer, 32 (53.3%) had CMVT.

In these 185 patients with CMVT, the thrombus was located on both sides in 87 (47.1%) patients, left side in 60 (32.4%) patients, and right side in 38 (20.5%) patients. The length of the thrombus on the left side was 4.32 ± 2.22 cm, with the diameter of 0.58 ± 0.2 cm, while the length of the thrombus on the right side was 4.15 ± 2.33 cm, with the diameter of 0.57 ± 0.19 cm. There were no statistically significant differences in the length and diameter of the thrombus between the left and right sides (P > 0.05, Table 3).

Analysis of risk factors for postoperative early CMVT

In univariate logistic regression analysis, the continuous variable preoperative D-dimer level was analyzed after conversion to a categorical variable based on its normal reference. The operative duration was analyzed after conversion to a categorical variable based on its median value. The age and the postoperative day 1 D-dimer level were analyzed as the continuous variables. The results showed that age, hypertension, cardiovascular disease, moderate and high Caprini risk score, no anticoagulation prophylaxis, preoperative D-dimer > 0.5 µg/mL, open heart surgery, operative duration > 135 min, intraoperative muscle relaxant administration > 2 times, and postoperative day 1 D-dimer level were risk factors for the early development of CMVT after thoracic surgery.

Multivariate logistic regression analysis showed that age, moderate and high Caprini risk score, no anticoagulation prophylaxis, operative duration > 135 minutes, and postoperative day 1 D-dimer level were the independent risk factors for the early development of CMVT after thoracic surgery (Table 4). Among 199 patients without the perioperative anticoagulation prophylaxis, 74 (37.2%) patients had CMVT. Out of 260 patients with the postoperative anticoagulation prophylaxis, 54 (20.8%) patients developed CMVT. Among 286 patients with the preoperative and postoperative anticoagulation prophylaxis, 54 (19.9%) patients had CMVT. Multivariate analysis showed that, compared with the patients with the preoperative and postoperative anticoagulation prophylaxis, the patients without anticoagulation prophylaxis had an increased risk for early postoperative CMVT (OR = 1.859, 95% CI = 1.147–3.013, P = 0.012). Compared with the patients with the preoperative and postoperative anticoagulation prophylaxis, the patients with the postoperative anticoagulation prophylaxis had a similar risk of early postoperative CMVT (OR = 0.913, 95% CI = 0.558–1.493, P = 0.717).

ROC curve analysis of age and postoperative day 1 D-dimer level

The ROC curve analysis showed that the AUC for age was 0.715, with a cutoff value of 58.5, sensitivity of 0.708, and specificity of 0.613. The AUC for the postoperative day 1 D-dimer level was 0.781, with a cutoff value of 1.445, sensitivity of 0.708, and specificity of 0.75. When we used the age of 58 years as the cutoff point, there were 397 and 348 patients aged ≤ 58 years and > 58 years, respectively, and among them, 54 (13.6%) and 131 (37.6%) patients had postoperative CMVT, respectively. When we used the postoperative day 1 D-dimer level of 1.45 as the cutoff point, there were 476 and 269 patients with D-dimer level ≤ 1.45 μg/mL and > 1.45 μg/mL, respectively; among them, 55 (11.5%) and 130 (48.3%) had postoperative CMVT, respectively (Table 5, Fig. 2).

In the present study, the incidence of early CMVT after thoracic surgery was 24.8%. The incidence in patients with thoracic malignancy, lung cancer, esophageal and gastric cardia cancer, and benign lung diseases were 26.2%, 22.6%, 53.3%, and 18.5%, respectively.

The CMVT has been shown to be more prevalent in certain groups such as patients on long airplane flights and those undergoing orthopedic surgery[14, 15] and a previous study showed that the incidence of CMVT in hospitalized patients was 9.4%[5].However,there have not been systematically studied in thoracic surgery. A retrospective study showed that the incidence of CMVT after lung cancer surgery was 63.3% among the cases of DVT[16],and another prospective study in China showed that the incidence of VTE after after thoracic surgeries of 11.5%, of which 80.0% were DVT and 20.0% were both DVT and PE[17].In patients after pneumonectomy due to bronchiectasis, the incidence of VTE was 8.5%. Among the cases of VTE, 50% had CMVT, which was diagnosed between the postoperative day 1 and 9 [18].VTE in the above studies included DVT and pulmonary embolism, and none of these studies evaluated CMVT. In contrast, our study focused on CMVT. In addition, we chose to study patients during the early postoperative period (within 24 hours after surgery).Calf muscular veins are often regarded as the initial location for lower limb thrombosis [19].In patients presenting with clinical manifestations suspicious for DVT, muscular calf veins have been shown to be the most common location for thrombosis and the incidence of CMVT was 23–41% among all patients with the suspicion for DVT[14]. Therefore, our study suggested a high incidence of early CMVT after thoracic surgery, which deserves clinical attention.

In our study, there were no statistically significant differences in the length or diameter of the thrombus between the left and right sides. Concerning the location of CMVT, our study showed that bilateral CMVT was predominant, followed by left sided and right sided CMVT. Heller et al. [20] reported that in 157 patients with DVT, calf DVT was bilateral in two cases (2.7%), left sided in 51.4% of the patients, and right sided in 45.9% of the patients. The predominance of left sided DVT is in agreement with previous findings from other studies [21, 22]. The bilateral thrombus formation is probably related to the underlying mutual compression between the two lower legs because thoracic surgery is performed in the lateral decubital position, which may play a role in unprovoked and provoked CMVTs.

Similar to several previously reported studies [12, 23, 24], our study showed that age, operative duration > 135 minutes, and Caprini score were the risk factors for early CMVT after thoracic surgery. An increased age, prolonged operative duration, and high Caprini scores were all risk factors for the development of VTE after thoracic surgery. Caprini score is widely used in many surgical specialties to identify high-risk patients with VTE [25]. In recent years, the modified Caprini score has been used to assess the risk of VTE after resection of malignant tumor of chest [26]. In this study, 87.4% of the patients underwent thoracoscopy. Although there was no statistical significance for the type of surgery in multivariate analysis between the two groups, the thoracotomy group tended to have a higher incidence of CMVT. In addition, our study showed the association between the frequency of intraoperative muscle relaxants > 2 times and the development of CMVT in patients during the early postoperative period. It is well-known that venous stasis is a risk factor for DVT and PE. The main driver force for the venous blood flow back to the heart through one-way venous valves comes from the contractions of the calf muscles in the lower extremities [27]. It has been shown that the reduced calf muscle pump function is a risk factor for the development of VTE [28]. Frequent intraoperative muscle relaxant administrations might affect the calf muscle pump function, increasing the risk of CMVT.

In the present study, the postoperative day 1 D-dimer level was a risk factor for early postoperative CMVT, with an AUC of 0.781, cutoff value of 1.445, sensitivity of 0.708, and specificity of 0.75. D-dimer is not only the minimal fibrin degradation product but also a specific degradation product of the fibrous matrix in the venous thrombi. It is abnormally elevated in the presence of blood hypercoagulation status or secondary hyperfibrinolysis and is a sensitive indicator of thrombosis [29, 30]. However, D-dimer level could be affected by many diseases, such as trauma, infection, and tumor [31, 32]. Our study showed that 15.4% of patients had preoperative D-dimer above the normal range. Among them, 80% of patients had malignancies. On the postoperative day 1, up to 77.5% of patients had D-dimer level above the normal range. Therefore, testing D-dimer levels at multiple time points after surgery, combined with the considerations of thrombosis-related risk factors, can lead to a better assessment for the development of VTE [33].

Patients with CMVT, even without leg edema and/or pain, could have concurrent PE and a significant incidence of VTE progression[34].Anticoagulation therapy should be considered for inpatients with CMVT[5].A previous study showed that the CMVT was associated with a clinically significant rate of VTE which is dramatically reduced with therapeutic anticoagulation[35].In the present study, the incidence of early postoperative CMVT in the patients without anticoagulation prophylaxis (37.2%) was higher than that in the patients with the postoperative anticoagulation prophylaxis (20.8%) and the patients with both preoperative and postoperative anticoagulation prophylaxis (19.9%). Further analysis showed that the patients without anticoagulation prophylaxis had an increased risk of early postoperative CMVT compared with the patients with both preoperative and postoperative anticoagulation prophylaxis (OR = 1.859, 95% CI = 1.147–3.013, P = 0.012). The patients with the postoperative anticoagulation prophylaxis had a similar risk of early postoperative CMVT compared with the patients with both preoperative and postoperative anticoagulation prophylaxis (OR = 0.913, 95% CI = 0.558–1.493, P = 0.717). This suggested that perioperative anticoagulation prophylaxis might reduce the development of early postoperative CMVT. Therefore, an individualized perioperative anticoagulation regimen consistent with the VTE prevention guidelines should be adopted to reduce the incidence of VTE while maintaining patient safety [36].

Limitations

Our study had some limitations. First, this was a single-center study with the bias on the patient sampling and disease type. Second, we did not evaluate the amount of blood loss during the surgery and did not assess the safety of perioperative anticoagulation prophylaxis, although the perioperative anticoagulation protocol was developed with reference to the Chinese expert consensus on the perioperative VTE prophylaxis in patients with thoracic malignancies. Finally, we did not perform long-term follow-up studies in our patients to assess the CMVT prognosis. Therefore, a multicenter study with a long-term follow-up needs to be carried out in the future.

In conclusion, the incidence of early CMVT after thoracic surgery was high, which requires clinical attention. The incidence of early CVMT could be reduced after perioperative anticoagulation prophylaxis. Older age, moderate and high Caprini risk score, no anticoagulation prophylaxis, operative duration > 135 minutes, and high postoperative day 1 D-dimer level were the independent risk factors for early development of CMVT after the thoracic surgery. Our study could help thoracic surgeons to pay attention to postoperative CMVT and perform prompt diagnostic tests and managements.

VET

venous thromboembolism events

CMVT

calf muscular vein thrombosis

DVT

deep vein thrombosis

PE

pulmonary embolism

BMI

body mass index

SD

standard deviation

OR

odds rations

95%CI

95% confidence intervals

AUC

area under the curve

ROC

receiver operating characteristic

n

number

NA

not applicable.

Ethics approval and consent to participate

This study was approved by the Ethics Committee of Binzhou Medical University Hospital(No.2023LW-55).All of the patients included in the study completed written informed consents.This study was performed in accordance with the ethical standards of Declaration of Helsinki (1964) and its later comparable ethical standards.

Consent for publication

Not applicable.

Availability of data and materials

The data that support the findings of this study are available from the corresponding author on reasonable request. Emails could be sent to the address below to obtain the shared data: [email protected].

Competing interests

The authors declare that they have no competing interests.

Funding

No funding was obtained for this study.

Authors’ contributions

XHT and ZQG built the conception and designed the study. XHT,MJ and STY provided statistical analysis and interpretation. LS,JT,LJW and RS re-analyzed the data.XHT,MJ,ZQG and STY jointly drafted the whole manuscript, the table and figure in the manuscript. Corresponding author ZQG is responsible for the final approval of the version to be published.All authors have read and approved the final manuscript.

Acknowledgements

The authors thank all the staff and participants of this study for their important contributions and Binzhou Medical University Hospital for support this project.

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Table 1 Modified Caprini risk factors and VTE scores

Caprini risk factors	Weighted scores	Non-CMVT (n)	CMVT (n)
Age 40-59 years	1	317	68
Abnormal pulmonary function	1	309	109
Aute myocardial infarction (＜1month)	1	0	0
BMI≧30kg/m²	1	22	8
Congestive heart failure (< 1 month)	1	0	0
History of inflammatory bowel disease	1	2	0
History of prior major surgery (< 1 month)	1	0	0
Complications of pregnancy	1	0	0
Oral contraceptive use	1	0	0
Sepsis (< 1 month)	1	0	0
Serious acute lung disease (< 1 month)	1	0	0
Swollen legs(current)	1	0	0
Varicose vein	1	0	0
Age 60-74 years	2	180	105
Central venous access	2	0	0
Confined to bed (> 72 h)	2	0	0
Major open surgery (≧45 min)	2	43	36
Present cancer	2	432	153
Prior cancer (except nonmelanoma skin)	2	57	10
Age≧75 years	3	7	11
History of VTE	3	0	0
Family history VTE	3	0	0
Chemotherapy	3	4	2
Acute spinal cord injury (< 1 month)	5	0	0
Major surgery(≧6h)	5	4	2

Table 2 Clinical characteristics of study participants

Characteristics

Non-CMVT group(n=560)

CMVT

group(n=185)

Z /c² value

P value

n

Age,years

mean±SD

Range

55.33±11.46

16-64

63.44±8.44

34-78

-8.78

0.000

Gender

Male

Female

255

305

85

100

0.009

0.923

BMI,kg/m²

mean±SD

Range

24.19±3.34

13.78-38.10

24.42±3.10

17.58-33.31

-0.835

0.404

Hypertension

No

Yes

4

56

7

38

2.21

0.33

Diabetes

No

Yes

503

57

165

20

0.60

0.782

Cardio-cerebrovascular disease

No

Yes

508

52

157

28

4.964

0.029

Preoperative D-dimer level

mean±SD

Range

0.32±0.39

0.01-4.36

0.43±0.65

0.06-7.45

-3.89

0.000

Caprini score

Low

Moderate

High

382

173

5

102

78

5

12.297

0.002

Anticoagulation prophylaxis

No

Postoperative

Pre and postoperative

125

206

229

74

54

57

22.252

0.000

Preoperative fasting period

≤12h

＞12h

325

235

103

82

0.317

0.607

Surgical side

Left

Right

259

301

84

101

0.040

0.865

Type of surgery

Thoracotomy

Thoracoscopy

50

510

44

141

27.833

0.000

Primary disorders

Benign

Malignant

128

432

32

153

2.549

0.122

Operative duration

mean±SD

Range

131.05±65.18

17-445

164.59±68.28

36-427

-6.15

0.000

Frequency of intraoperative muscle relaxant administration

0-2

＞2

407

153

104

81

17.493

0.000

Postoperative day 1 D-dimer level

mean±SD

Range

1.42±1.89

0.13-18.73

4.25±4.36

0.25-25.03

-11.47

0.000

Table 3 Characteristics of postoperative early CMVT

Thrombus site	n(%)	Thrombus length(cm)	Thrombus diameter(cm)	Z value	P value
Left mean±SD Range	60(32.4)	4.32±2.22 1.1-11.8	0.58±0.2 0.1-1.2	-0.787	0.431
Right mean±SD Range	38(20.5)	4.15±2.33 0.6-12.5	0.57±0.19 0.1-1.1	-0.122	0.903
Bilateral	87(47.1)	NA	NA	NA	NA

Table 4 Univariate and multivariate logistic regression analysis on the risk factors associated with early postoperative CMVT

Factor	CMVT incidence(%)	Univariable	Multivariable
Factor	CMVT incidence(%)	OR(95% CI) P value	OR(95% CI) P value
Age,years	NA	1.087(1.065-1.109) 0.000	1.092(1.064-1.120) 0.000
Gender(male/female)	25/24.7	0.984(0.705-1.373) 0.923	NA
BMI,kg/m²(≦25/>25)	24.5/25.4	1.054(0.749-1.483) 0.763	NA
Hypertension(no/yes)	22.3/31.6	1.610(1.126-2.300) 0.009	NA
Diabetes(no/yes)	24.7/26	1.070(0.624-1.833) 0.807	NA
Cardio-cerebrovascular disease(no/yes)	23.6/35	1.742(1.064-2.853) 0.027	NA
Preoperative D-dimer level, μg/mL(≦0.5/>0.5)	22.5/37.4	2.052(1.347-3.128) 0.001	NA
Caprini score (low/moderate and high)	21.1/31.8	1.746(1.243-2.453) 0.001	2.029(1.276-3.227) 0.003
Anticoagulation prophylaxis Pre and postoperative Postoperative No	19.9/20.8/37.2	1(Reference) 1.053(0.694-1.598) 0.808 2.378(1.581-3.578) 0.000	1(Reference) 0.913(0.558-1.493) 0.717 1.859(1.147-3.013) 0.012
Preoperative fasting period,h(≦12/>12)	24.1/25.9	1.101(0.787-1.539) 0.574	NA
Surgical side(left/right)	24.5/25.1	1.035(0.741-1.444) 0.842	NA
Type of surgery (thoracotomy/thoracoscopy)	46.8/21.7	3.183(2.038-4.972) 0.000	NA
Primary disorders(benign/malignant)	20/26.2	1.417(0.922-2.176) 0.112	NA
Operative duration,min(≦135/>135)	16.4/33.6	2.588(1.827-3.665) 0.000	1.697(1.135-2.538) 0.010
Frequency of intraoperative muscle relaxant administration(≦2/>2)	20.4/34.6	2.072(1.468-2.925) 0.000	NA
Postoperative day 1 D-dimer level,μg/mL	NA	1.435(1.325-1.554) 0.000	1.342(1.232-1.462) 0.000

Table 5 ROC curve analysis of age and postoperative day 1 D-dimer level

Risk factors	AUC	P value	95%CI	Youden’s index	Cut-off value	Sensitivity	Specificity	CMVT incidence(%)
Age (years)	0.715	0.000	0.674-0.756	0.321	58.5	0.708	0.613	13.6/37.6
D-dimer(μg/mL)	0.781	0.000	0.742-0.820	0.458	1.445	0.708	0.75	11.5/48.3

No competing interests reported.

Risk factor analysis for early development of calf muscular vein thrombosis after thoracic surgery:a prospective observational study

Status:

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Abstract

Figures

Background

Materials and Methods

Results

Discussion

Limitations

Conclusions

Abbreviations

Declarations

References

Tables

Additional Declarations

Status:

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