**4.2.1 Mechanical prophylaxis**  Mechanical modalities include graduated compression stockings, intermittent pneumatic compression devices (IPC) and venous foot pump. Perioperative use of the above devices and early mobilization of patients reduce the risk of VTE by increasing venous outflow and

preventing venous stasis. Remarkable advantage of mechanical prophylaxis is lack of interference in the coagulation path, which renders it safe for patients in high risk for bleeding. Limitations of the use of mechanical devices are skin irritation and poor compliance.

#### **4.2.2 Pharmacological prophylaxis**

Unfractionated heparin (UFH) and low molecular weight heparins (LMWH) are effective in the prophylaxis of VTE in surgical patients. An initial dose of 5000 units UFH is

Venous Thromboembolism in Bariatric Surgery 71

Clinical prediction rules were established in order to overcome the above limitations and provide effective risk stratification of VTE. Wells Score and Revised Geneva Score assess the

The role of arterial blood gas (ABG) in the diagnosis of VTE is rather limited. Respiratory alkalosis and hypoxemia constitute common but non-specific findings and although their presence should raise suspicion, cannot be used solely for the confirmation of the diagnosis. D-dimers blood test detects a fibrin degradation product and has a high negative predictive value. In bariatric patients has limited value only to exclude VTE, as recent surgery,

Several diagnostic imaging studies can be performed in bariatric population, although

Electrocardiogram (ECG) in acute pulmonary embolism can reveal sinus tachycardia, ST segment depression and signs of right ventricular strain (more commonly incomplete right bundle branch block). Echocardiogram may detect right ventricular dysfunction. The high prevalence of cardiovascular diseases (coronary heart disease, left ventricular hypertrophy, atrial fibrillation, arrhythmias) in obese patients renders ECG and echocardiogram

Chest radiograph in acute pulmonary embolism may appear normal, while rarely, infiltrates, pleural effusion, atelectasis may be present. Consequently, chest radiograph is more useful in the exclusion of other pathological entities (pneumonia, pneumothorax) that

In the detection of DVT, Duplex Doppler Ultrasound remains the standard noninvasive examination for the visualization of thrombus, although when performed in obese patients

Chest Spiral CT has recently replaced pulmonary angiography and is now considered as the gold standard in the diagnosis of PE. However, special equipment must be available for

Pathological entities that present with the same clinical features and sings as venous thromboembolism and should be part of the differential diagnosis are: pneumonia, pleural effusion, pneumothorax, congestive heart failure, and cardiac ischemia, exacerbation of

Furthermore, differential diagnosis of PE after bariatric surgery should include anastomotic leakage, which may also present with tachycardia, fever, chest pain and respiratory insuffiency. An upper gastrointestinal study or surgical intervesion may be necessary in

European Society of Cardiology guidelines and American Heart Association statement provide evidence-based therapeutic strategies of VTE. Hemodynamic and respiratory

clinical probability of VTE based on patient's risk factors and clinical findings.

inflammation and trauma can induce false positive readings.

may present with the same clinical picture with pulmonary embolism.

morbidly obese patient, given the weight limitation of the conventional ones.

chronic obstructive pulmonary disease, asthma and pulmonary edema.

**4.3.2 Laboratory findings** 

**4.3.3 Imaging studies** 

diagnostic tools of limited value.

may have reduced accuracy.

**5. Differential diagnosis** 

order to exclude such a complication.

**6. Treatment of venous thromboembolism** 

limitations occur.

administrated subcutaneous preoperatively and repeated doses every 8 or 12 hours are required. On the contrary, LMWH shows improved pharmacological characteristics, as it requires a single dose per day, has lower degree of plasma protein binding, longer half-life and an enhanced bioavailability. Contraindications in anticoagulation agents are allergy, heparin-induced thrombocytopenia, coagulation disorders, active bleeding or patient at high risk of bleeding.

There is no consensus in literature considering the optimal regimen, dosage, and duration or application mode for VTE preventions in bariatric surgery patients. Furthermore, there is a paucity of data confirming the scaling of dosage according to body weight and renal function. Several authors support low rate of VTE when weight-adapted dosages are administrated, while others suggest that there is no significant difference. American College of Chest Physicians recommend the administration of LMWH, UFH 3 times daily, fontaparinux or the combination of one of these pharmacologic method with optimally used IPC (Grade 1C). Although according to recommendations administrated doses should be higher than those for nonobese patients (Grade 2C), adjusting doses according to BMI remain debatable. Current statement of American Society for Metabolic and Bariatric Surgery suggests the use of both mechanical and pharmacological prophylaxis in bariatric patients, without providing further adaptation guidance. Data on compliance of bariatric surgeons with the above guidelines are inconsistent, however treating high-risk bariatric patients seems to have a positive effect in adherence. Wu et al reported that 95% of bariatric surgeon comply with guidelines, while ENDORSE trial proved that only 58,5% of all surgical patients in risk for VTE receive prophylaxis.

#### **4.2.3 The role of inferior vena cava filters**

The prophylactic use of inferior vena cava filters (IVCF) remains controversial. Although recent studies report lower incidence of DVT and PE, other suggest that IVCF may reduce the rate of PE, but increase the incidence of DVT. Risk and complications deriving from the implantation of such a device should not be underestimated. Inferior Vena Cava, filter breakage, caval perforation, insertion site hematoma and infection have been reported. Based on the above, American Society of Hematology stated that the evidence to support the efficacy of IVCF in bariatric surgery is insufficient (Grade 2C recommendation against their use).

#### **4.3 Diagnosis of venous thromboembolism**

#### **4.3.1 Clinical findings**

Presenting symptoms of VTE are rather non-specific (dyspnea, chest pain, tachypnea), rendering the clinical diagnosis difficult. The key to early detection of VTE in bariatric patients is the high degree of vigilance for clinical features of DVT or PE. Physical examination may reveal increased respiratory rate, rales, wheeze, pleural friction rub, cyanosis, tachycardia, loud second heart sound, sings of DVT (oedema, redness, Homan's sign- pain on passive dorsiflexion of the ankle) and temperature above 38,5oC. Syncope and severe hypotension when present should be considered as signs of hemodynamic compromise.

In obese patients typical clinical findings of DVT or PE can be underestimated, as some of them (edema of lower extremity, tachycardia, dyspnea, tachypnea) pre-exist, due to obesity related co-morbidities, such as cardiac or respiratory failure, varicose veins, obesity related hypoventilation syndrome.

Clinical prediction rules were established in order to overcome the above limitations and provide effective risk stratification of VTE. Wells Score and Revised Geneva Score assess the clinical probability of VTE based on patient's risk factors and clinical findings.

#### **4.3.2 Laboratory findings**

70 Pulmonary Embolism

administrated subcutaneous preoperatively and repeated doses every 8 or 12 hours are required. On the contrary, LMWH shows improved pharmacological characteristics, as it requires a single dose per day, has lower degree of plasma protein binding, longer half-life and an enhanced bioavailability. Contraindications in anticoagulation agents are allergy, heparin-induced thrombocytopenia, coagulation disorders, active bleeding or patient at

There is no consensus in literature considering the optimal regimen, dosage, and duration or application mode for VTE preventions in bariatric surgery patients. Furthermore, there is a paucity of data confirming the scaling of dosage according to body weight and renal function. Several authors support low rate of VTE when weight-adapted dosages are administrated, while others suggest that there is no significant difference. American College of Chest Physicians recommend the administration of LMWH, UFH 3 times daily, fontaparinux or the combination of one of these pharmacologic method with optimally used IPC (Grade 1C). Although according to recommendations administrated doses should be higher than those for nonobese patients (Grade 2C), adjusting doses according to BMI remain debatable. Current statement of American Society for Metabolic and Bariatric Surgery suggests the use of both mechanical and pharmacological prophylaxis in bariatric patients, without providing further adaptation guidance. Data on compliance of bariatric surgeons with the above guidelines are inconsistent, however treating high-risk bariatric patients seems to have a positive effect in adherence. Wu et al reported that 95% of bariatric surgeon comply with guidelines, while ENDORSE trial proved that only 58,5% of all

The prophylactic use of inferior vena cava filters (IVCF) remains controversial. Although recent studies report lower incidence of DVT and PE, other suggest that IVCF may reduce the rate of PE, but increase the incidence of DVT. Risk and complications deriving from the implantation of such a device should not be underestimated. Inferior Vena Cava, filter breakage, caval perforation, insertion site hematoma and infection have been reported. Based on the above, American Society of Hematology stated that the evidence to support the efficacy of IVCF in bariatric surgery is insufficient (Grade 2C recommendation against their use).

Presenting symptoms of VTE are rather non-specific (dyspnea, chest pain, tachypnea), rendering the clinical diagnosis difficult. The key to early detection of VTE in bariatric patients is the high degree of vigilance for clinical features of DVT or PE. Physical examination may reveal increased respiratory rate, rales, wheeze, pleural friction rub, cyanosis, tachycardia, loud second heart sound, sings of DVT (oedema, redness, Homan's sign- pain on passive dorsiflexion of the ankle) and temperature above 38,5oC. Syncope and severe hypotension when present should be considered as signs of hemodynamic

In obese patients typical clinical findings of DVT or PE can be underestimated, as some of them (edema of lower extremity, tachycardia, dyspnea, tachypnea) pre-exist, due to obesity related co-morbidities, such as cardiac or respiratory failure, varicose veins, obesity related

high risk of bleeding.

surgical patients in risk for VTE receive prophylaxis.

**4.2.3 The role of inferior vena cava filters** 

**4.3 Diagnosis of venous thromboembolism** 

**4.3.1 Clinical findings** 

hypoventilation syndrome.

compromise.

The role of arterial blood gas (ABG) in the diagnosis of VTE is rather limited. Respiratory alkalosis and hypoxemia constitute common but non-specific findings and although their presence should raise suspicion, cannot be used solely for the confirmation of the diagnosis. D-dimers blood test detects a fibrin degradation product and has a high negative predictive value. In bariatric patients has limited value only to exclude VTE, as recent surgery, inflammation and trauma can induce false positive readings.

#### **4.3.3 Imaging studies**

Several diagnostic imaging studies can be performed in bariatric population, although limitations occur.

Electrocardiogram (ECG) in acute pulmonary embolism can reveal sinus tachycardia, ST segment depression and signs of right ventricular strain (more commonly incomplete right bundle branch block). Echocardiogram may detect right ventricular dysfunction. The high prevalence of cardiovascular diseases (coronary heart disease, left ventricular hypertrophy, atrial fibrillation, arrhythmias) in obese patients renders ECG and echocardiogram diagnostic tools of limited value.

Chest radiograph in acute pulmonary embolism may appear normal, while rarely, infiltrates, pleural effusion, atelectasis may be present. Consequently, chest radiograph is more useful in the exclusion of other pathological entities (pneumonia, pneumothorax) that may present with the same clinical picture with pulmonary embolism.

In the detection of DVT, Duplex Doppler Ultrasound remains the standard noninvasive examination for the visualization of thrombus, although when performed in obese patients may have reduced accuracy.

Chest Spiral CT has recently replaced pulmonary angiography and is now considered as the gold standard in the diagnosis of PE. However, special equipment must be available for morbidly obese patient, given the weight limitation of the conventional ones.
