Home Archive Vol.39, No.1, 2013 Original Papers Study of the risk factors and prevention of venous thromboembolism in surgery

Study of the risk factors and prevention of venous thromboembolism in surgery

 M.Ş. GHELASE(1), A. BORUGĂ(2), S. RÂMBOIU(2),

A. ROTARU(2), D. MĂRGĂRITESCU(2), D. CÂRŢU(2), F. GHELASE(2)

 

(1)Department of Public Health and Management, UMF Craiova, (2) Surgical Specialities I, UMF Craiova

ABSTRACT Venous thrombosis is still a major cause for high morbidity and mortality because of its clinical manifestation – deep venous thrombosis (DVT); establishing an early diagnostic is important because thrombosis can rapidly extend to a potentially lethal complication – pulmonary embolism or it can lead to invalidating consequences. Between 2002 and 2006 10653 patients were surgically treated, among them 3875 (45.5%) presented risk factors which could lead to deep venous thrombosis. Patients were grouped according to the involved risk factors in three severity classes: major risk in 1860 cases (47.87%), medium risk in 1300 cases (33.16%) and with low risk 715 (18.56%). Regardless the severity of the risk factors, patients were included in the preventive treatment protocol for deep venous thrombosis, started 1-2 hours before the surgical intervention. Although there are advantages and good results of using low-molecular-weight-heparins (LMWH), we recorded hemorrhagic complications in 79 cases (2.04%), mainly in those with major risk. Surgical reintervention was necessary in 2 cases while treatment reconsideration, conservative measures, reassessment of risk factors and hematological explorations eliminated these adverse effects. Despite the preventive treatment for the venous thrombosis confirmed by Doppler ultrasound scan, we recorded 36 cases of deep venous thrombosis, 12 cases of pulmonary microembolism who received anticoagulation therapy and 3 patients who died from massive pulmonary embolism.

KEYWORDS venous thrombosis, pulmonary embolism, heparin


Introduction

Known as venous thromboembolism or thromboembolic disease, although it has a single etiology, its components, venous thrombosis and pulmonary embolism are studied separately. Therefore, evolutionary risk is twofold: an early one which is vital and sometimes reveals pulmonary embolism and a late one that is functional – posttrombotic syndrome.

Etiopathogenesis begins at the lower limbs and /or pelvic veins. Recognition of extrinsic and/or intrinsic predisposing factors in the occurence  of DVT allows preventive treatment. There are also trigger and determinant factors.

Surgery pays a serious tribute to postoperative thromboembolic events, although most laparoscopic or classical interventions are quoted as therapeutic successes. DVT and pulmonary embolism (PE) after surgical interventions have a significant risk of morbidity and mortality. Hence the need for preoperative assessment of thromboembolic risk factors and for a modern perioperative prophylaxis, making an early diagnosis and applying an effective treatment when a DVT occurs.

Due to the high incidence of venous thromboembolism of various medical and surgical etiologies, it remains a current public health problem internationally. Scientific progress made on pathogenesis, early diagnosis and particularly in preventive treatment based on low-molecular-weight heparins (LMWH) has led to a significant reduction in morbidity and mortality from venous thromboembolism in surgery.

Our paper is a prospective study which aims to do a preoperative evaluation of thrombotic risk factors in a group of patients who underwent surgical perioperative prophylaxis with LMWH associated with other general measures of prevention. Then a postoperative clinical and paraclinical monitoring has been done in order to detect any possible side therapeutic effect, to discover early symptomatology of DVT, to confirm the diagnosis by Doppler ultrasound scan and finally to apply the appropriate therapy for thrombosis and prevention of pulmonary embolism.

Materials and methods

Besides the infection prophylaxis practiced in all cases, prevention of venous thromboembolic complications is a current surgical concern that begins with the detection of one or more risk factors that require rigorous application of thromboprophylaxis measures.

The risk factors involved in the pathogenesis of venous thrombosis (VT) were known since 1845 as the Virchow triad represented by vein wall damage, blood hypercoagulability and venous stasis. Recently these risk factors were classified as extrinsic and intrinsic risk (1, 9).

Between 2002-2006, 10653 patients were admitted into the Surgery Department  One of Craiova Regional Hospital of which 8500 patients were operated: classic approach 7350 and laparoscopic method 1150. In 3875 of them (45.5%) risk factors that imposed heparin thromboprophylaxis were identified.

Depending on the number of risk factors involved, patients were grouped into classes of severity according to Oakes criteria (10). Into the major and increased risk class (risk ratio> 10) were included 1860 (47.87%) patients, average risk class (risk ratio between 2 and 9) includes 1300 (33.16%) patients and the low risk class (risk ratio <2) 715 (18.56%) patients. All risk patients, preoperatively selected, regardless of their severity were included in the established protocol of heparin thromboprophylaxis using LMWH administered 1-2 hours preoperatively subcutaneously, dose rate being imposed by the risk class and type of product available at that time in pharmacy. Next dose of heparin was administered 12 hours after the first one and it continued for 5 to 7 days, in the recommended dosage and according to the patient risk class. In cases of prolonged immobilization and hospitalization, duration of heparinotherapy was longer.

Criteria for inclusion in the study group were: age over 20; in patients over 40 the risk of VTE increases; patients with large and medium-sized operations, complex, benign and especially malignant disease with associated medical pathology, vascular trauma and patients with minor risk.

Exclusion criteria were: age under 20, unoperated patients except those with a history of VTE; those with lower risk; clotting disorders, recent acute hemorrhage, except those targeted by the surgical hemostasis; malignant hypertension, severe liver disease, acute or chronic renal failure with bleeding disorders, severe acute pancreatitis, allergy to heparin, AMI under 3 months, pregnancy or lactation, general or spinal anesthesia.

The following parameters have been used:

- distribution of patients according to age and sex,

- presence and evaluation of extrinsic factors of VTE and inclusion into a risk class,

- monitoring the progress and postoperative response to heparin thromboprophylaxis,

- necessary laboratory investigations plus venous Doppler ultrasound scan for clinical suspicion of DVT,

- side effects of anticoagulant therapy,

- effectiveness of thromboprophylaxis by assessing the incidence of DVT,

- number of deaths from pulmonary embolism.

Results

We feel that some comments on our data are necessary. Gender as a risk factor showed a higher incidence in females (69.33%) than in men (30.66%) and by area of ​​residence, 67% of patients were from urban areas compared to 34% of rural areas. These differences can be explained by the existence of more thromboembolic risk factors in women such as lower limb venous insufficiency, obesity, gynecological interventions, hormone replacement therapy and oral contraceptives  which were identified in our study too.

 

Table 1. General Risk Factors

Risk factors

Monitored patients

%

Obesity

2053

53

Diabetes

1162

30

Age over 40

2518

65

Smoking

1550

40

Neoplastic disease

865

22,32

Varicose disease

135

3,48

Systemic Infections

250

6,45

Chronic Card. Insufficiency

321

8,3

Prolonged Immobilization

271

7

Hormone therapy

300

7,74

COPD

116

3

Thromboembolic history

116

3

Oral Contraceptives

30

0,77

Pregnancy

10

0,25

Splenic diseases

35

0,90

 

General characteristics as age and weight shape the image of a 60 year-old patient with obesity, associated with a multitude of other factors such as diabetes, hypertension and malignancies that increase the potential risk of VTE. Such patients require thromboprophylaxis with LMWH (Nandroparin, Enoxaparin, Dalteparin).

Obesity identified in 53% of patients included in our study correlates with other risk factors such as sedentary lifestyle, difficult postoperative mobilization, insufficient electrolyte and fluid balance and frequent septic complications. In this type of obese patients there are also difficulties with identification of early signs of DVT.

Advanced age and smoking are also important risk factors; malignancies have a thromboembolic risk of six times higher than the general population, VTE being the most common complication. (6,7)

Risk factors depend on surgical procedure too. Laparoscopic procedure (29.67%) has additional specific risk factors related to the chosen technique of surgery. Induced pneumo-peritoneum leads to changes on lower limbs venous return with respect to CO2 insufflation pressure and to duration patient has been kept into Flower position, producing  increased platelet aggregation and hypercoagulability.

Depending on severity class, the most predominant were patients with major risk (47.87%).

Perioperative prophylaxis of VTE is currently required to be initiated preoperatively in patients included in risk groups because the incidence of disease in operated patients without heparin thromboprophylaxis  is between 10 - 40%. Approximately 25% of proximal thrombi located into the deep veins of the legs can cause pulmonary embolism which in turn is responsible for about 10% of hospital deaths. (9)

 

Table 2. Risk factors – surgical procedure

Risc factors

Monitored

patients

%

 

Laparoscopic surgery (gallbladder,

appendix, hiatal hernia)

1150

29,67

 
 
 

Eventrations cure – herniorrhaphies

810

20,90

 

Gastrectomies, colectomies, rectum amputations, bilio-digestive derivatives, duodenopancreatectomy

565

14,58

 

Various laparotomies

470

12,12

 

Total and subtotal hysterectomies

275

7,01

 

Modified radical mastectomies

150

3,87

 

Vascular operations

350

9,03

 

Perineal operations

50

1,29

 

TOTAL

3820

98,58

 

 

Preventive measures in general surgery are done to eliminate or minimize the pathogenic factors of Virchow triad: venous congestion control, prophylactic anticoagulation, dextran, antiplatelet agents.

Unless there are contraindications for anticoagulation use, heparin therapy is the method of choice for DVT prophylaxis in most patients. The incidence of DVT in patients on anticoagulation drugs is 66% lower than in those not receiving this medication.(2)

 

Table 3.  Risk factors – surgical disease

Risk factors

Cases

%

Neoplastic disease – digestive

565

14,58

Neoplastic disease – genital

275

7,09

Abdominal wall defects (primary and postoperative)

810

20,90

Mammary tumors

150

3,87

Polytrauma

220

5,67

Vascular trauma (iatrogenic accidents)

45

1,16

Gallbladder lithiasis

750

19,35

Peritonitis

250

6,45

Perineum

50

1,29

Peripheral vasculopathies

350

9,03

TOTAL

3465

89,41

 

 We emphasize the need for clinical and biological monitoring of anticoagulant therapy with LMWH.

 

Table 4.Hemorrhagic manifestations after LMWH

Type

Monitored

patients

Treatment

Cases

 
 

Spontaneous abdominal parietal hematoma

16

Conservative

16

 

Surgical wound hematoma

45

Conservative

35

 

Evacuation

10

 

Hemoperitoneum

 on drainage tube

5

Blood – plasma

Reintervention

2

 

Conservative medical

3

 

Axillary hematoma

3

Evacuation

3

 

Upper gastrointestinal bleeding

6

Endoscopic haemostasis

2

 

Medical

4

 

Macroscopic

haematuria

4

Conservative

4

 

TOTAL

79(2,04%)

 

 

 

 

Although it is considered to cause fewer complications than unfractionated heparin because it inhibits at a lesser extent platelet function and does not cause increased permeability in the microcirculation, on the study group we recorded 79 (2.04%) different types of bleeding events such as spontaneous or wound parietoabdominal hematoma, hemoperitoneum identified on drainage tube, axillary hematoma, upper GI bleeding, macroscopic hematuria. Reintervention and blood transfusion were required in only two cases of hemoperitoneum, the remaining cases being resolved by conservative treatment.

 

Fig 1. Laparoscopic cholecystectomy. Parietal Hematoma after thromboprophylaxis with LMWH.

 

Fig 2. Acute lithiasic cholecystitis. Parietal ecchymosis. Thromboprophylaxis with LMWH.

 

VTE prophylaxis proved in our experience, as in other studies (3,4) to be safe and virtually no major bleeding or allergic complications were recorded when therapeutic doses have been known and properly given.

Regarding the effectiveness of perioperative thromboprophylaxis with LMWH, the incidence of lower limbs DVT confirmed by Doppler ultrasonography and its embolic consequences was 36 (0.92%) cases including 3 deaths. Taking into account the fact that in the absence of heparinotherapy  incidence of DVT is between 15 - 40% and our findings are similar with data provided by most publications,  we can say that the use of LMWH is effective in combating this postoperative event.

 

Fig 3. Doppler ultrasound scan– iliofemoral thrombosis

Fig 4.  Doppler ultrasound scan– iliofemoral thrombosis

 

Although thromboprophylaxis with LMWH does not  give a complete protection against VTE, it remains the only method to reduce its incidence as well as massive pulmonary thromboembolism and VTE related mortality and morbidity.

 

Table 5. Pulmonary thromboembolism accidents during thromboprophylaxis with LMWH

Event type

Cases

%

DVT

36

0,92

Pulmonary microembolism

12

0,30

Lethal massive pulmonary embolism

3

0,07

TOTAL

36

0,92

Discussion

 In venous thromboembolism, the thrombus appears first in the context of predisposing risk factors, inflammatory process being absent in the vein wall - flebotrombotic phase. At this point thrombus is floating in the vessel lumen and may embolize to the pulmonary arterial system. Its presence into the deep venous vessel induces an inflammatory phenomena of the wall which define the phase of thrombophlebitis where the risk of embolization is reduced to zero. (16)

DVT of the lower limbs together with its possible serious consequences represent events  which often increase morbidity and mortality of surgical interventions, especially in the field of general surgery, traumatology, orthopedics, gynecology and urology.

In a study done by Suzuki et al. (14) it has been found that the incidence of pulmonary embolism in patients operated for malignant lesions was 22%, compared to only 0.32% for benign conditions.

In association with cancer, many other factors involved in promoting hypercoagulable state may predispose the patient to the occurrence of thromboembolic events. These factors include older age, obesity, acute respiratory failure, congestive heart failure, acute infections, smoking, use of oral contraceptives and a series of events related to surgical intervention: increased duration of operation, perioperative bleeding, dissection of the retroperitoneal lymph nodes, perioperative transfusions, tissue dissection and prolonged postoperative immobilization (12, 15). 40% of pulmonary embolism is found in patients with body mass index over 25 (8).

In this context it is considered that there are sufficient reasons to recommend routine prophylaxis of thromboembolic complications in patients who are to undergo surgery when at least one risk factor is present.

Regarding cost-effectiveness ratio in patients with low thromboembolic risk, external pneumatic compression seems more economical, however for those with increased thromboembolic risk, the most effective way of prevention is to use a combination of external pneumatic compression and LMWH(5, 13)

Conclusions

Thromboembolic events in surgery are important sources of postoperative morbidity and mortality.

In this context, each patient who undergoes a surgical intervention should be assessed for any risk factors that may trigger a thromboembolic event. General nursing care and prophylaxis strategy with LMWH are decided according to these factors.

Despite preventive measures, protection against possible thromboembolic complications is not complete.

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Correspondence Address: M. Ghelase, Department of Public Health and Management, University of Medicine and Pharmacy of Craiova, Str. Petru Rares No 2, 200456, Craiova, Romania

 

 


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