See also: quick guide to prophylaxis of thrombosis - modified Caprini assessment (password protected)

General Considerations

• Venous Thromboembolism (VTE) poses a significant burden to the healthcare population due to morbidity, mortality, and economic impact.
• VTE composes deep venous thrombosis (DVT) and pulmonary embolism (PE). (Meyer et al. 2018)
• VTE has been estimated to be as high as 40% post-operatively in the general surgery population and up to 60% in the orthopedic surgery population. (Flevas et al 2018)
• A systematic review by Moubayed et al. in 2017 reported that the incidence of VTE in the Otolaryngology population was 0.4%, but this analysis included outpatients and inpatients. Thus, the number is likely much higher if focused solely on inpatients. (Moubayed 2017)
• VTE causes over 150,000 deaths per year in the United States. The mortality rate is almost 10% in the first hour after patients suffer a PE. (Nagamalesh et al. 2017)
• To our knowledge (5-14-2020), although there are publications with recommendation, there are no official established guidelines in the field of Otolaryngology - Head and Neck Surgery to address thromboprophylaxis. In general, treatment patterns have been adapted from other medical specialty guidelines.
  • Specific guidelines in Otolaryngology have been a challenge due to the wide variety of procedures performed by Otolaryngologists.
• American College of Chest Physicians developed a set of guidelines in 2012 (CHEST guidelines) for prevention of VTE. (Kearon et al. 2016)

Risk Factors 

• Cancer is a hypercoagulable state and is thought to increase the risk of VTE due to inflammation, tumor-associated factors, and chemotherapeutic agents used to treat cancer. (Meyer et al. 2018) A study by Ahmad et al. showed that VTE can occur up to 18.3% of the time after major head and neck surgery for cancer. (Ahmad et al. 2016)
• Multiple inherited risk factors have been identified to cause VTE, including Factor V Leiden and deficiencies of antithrombin, protein C, and protein S. (Moran et al. 2020)
• The risk of VTE can increase as the result of a major trauma. A prospective study by Geerts et al. showed that DVT developed in 54% of patients after a major head injury. (Geerts et al. 1994)
• A multitude of other risk factors exist, and the clinician needs to carefully take these factors into account on an individualized basis. 

Diagnostic Evaluation of VTE and PE

• Management may be improved by stratifying patients into low, medium, and high risk categories based on multiple clinical and physiological components.
  • It has been recommended that the intensity with which the diagnosis is pursued should be based on pre-test probability of VTE or PE.
  • The clinical assessment for PE based on symptomatology and physical exam general is thought to be unreliable due to the variety of non-specific symptoms.
  • The Homan's sign, which is pain elicited behind the knee with dorsiflexion of the foot, is a classical test for VTE. Unfortunately, it is neither sensitive nor specific for diagnosis of a deep venous thrombosis. (Ambesh et al. 2017)
• If a patient has dyspnea, tachypnea, or chest pain, these symptoms may warrant objective diagnostic information. In an analysis of 500 patients with suspected PE, sudden onset dyspnea was the most common symptoms and tachycardia was the most common sign. (Miniati et al. 1999)

Pulmonary Embolism Rule-out Criteria (PERC)

Kline et al proposed this set of criteria was used to evaluate low risk patients. If the patient is considered very low risk (less than 15% chance) and all of the questions below are negative, no further interventions are warranted. (Kline et al. 2004)

1. Is the patient older than 49 years old?
2. Is the patient tachycardic (heart rate over 100 beats per minute)?
3. Is pulse oximetry less than 95% without supplemental oxygen?
4. Does the patient have hemoptysis?
5. Is the patient taking estrogen?
6. Does the patient have a personal history of deep venous thrombosis?
7. Trauma or surgery in the past month?
8. Is there unilateral leg swelling?

Objective Data:

• Multiple publications report that laboratory tests in isolation are not diagnostic for PE (Miniati et al. 1999, Task Force on Pulmonary Embolism 2000). Some results may help direct evaluation and include
  • ABG demonstrating hypoxemia without clear etiology.
  • D-dimer is a sensitive marker for PE but has low specificity. It can be elevated in many other conditions, including malignancy, pregnancy, and recent surgery. A low D-dimer (<500 ng/mL) can be used to rule out a PE in patients with a low probability of a PE.
  • If patients have a high risk of PE or the D-dimer is elevated in a patient that was initially thought to be low risk, further work-up is warranted.
• The imaging modality of choice is a CT pulmonary angiography. Multiple studies report the sensitivity and specificity of a CT pulmonary angiography ranges from 83-100% and 89-96%, respectively. (Dogan et al. 2015)
  • If patients have a mild to moderate reaction to contrast media, Stein et al. recommended that they be pre-treated with corticosteroids. With a serious reaction to contrast media, an alertnative diagnostic test such as pulmonary scintigraphy may need to be considered. (Stein 2006)
  • When CT pulmonary angiography cannot be completed, a ventilation perfusion scan may be considered if it is an option at this specific institution. However, this is not the gold standard and will not be further discussed in this article. 

VTE and PE Prevention and Recommendations

• There is no universal agreement on the best model to predict DVTs and PEs. However, the most widely utilized one currently is the Caprini thrombosis risk assessment model (Caprini 2005), which utilizes 40 preoperative characteristics.
• Caprini risk assessment is obtained from these criteria (see: https://www.mdcalc.com/caprini-score-venous-thromboembolism-2005).
• One of the greatest limitations for the Caprini model in Otolaryngology is the classification of surgery being less than or greater than 45 minutes. Given the wide variety of operating times, complexity, and potential auto-transplant of tissue and immobilization in head and neck surgery, multiple limitations exist for this section.
• Cramer et al. developed recommendations based on the Caprini risk calculator for Otolaryngologists. (Cramer et al.; Otolaryngol Head Neck Surg. 2018)
  • Risk factors (points):
    • 1: Age 41-60, minor surgery, BMI >25, abnormal pulmonary function, serious lung disease, sepsis within the past month, acute myocardial infarction, congestive heart failure, medical patient at bed rest, swollen legs, varicose veins, oral contraceptives or hormone replacement, pregnancy or postpartum, history of unexplained or recurrent spontaneous abortion
    • 2: Age 61-74, major surgery >45 minutes, malignancy, confined to bed over 73 hours, central venous access, immobilizing plaster cast
    • 3: Age ≥75, personal or family history of VTE, Factor V Leiden, Prothrombin 20210A mutation, lupus anticoagulant, anticardiolipin antibodies, elevated serum homocysteine, heparin-induced thrombocytopenia, other thrombophilias
    • 5: Fracture (hip, pelvis, or leg), acute spinal cord injury within the past month, elective arthroplasty
  • ​Recommendations (Add points from risk factors listed above):
    • Very low: General Surgery (0), Otolaryngology (0 or 2) --> No recommendation
    • Low: General Surgery (1 or 2), Otolaryngology (3 or 4) --> Mechanical prophylaxis
    • Moderate: General Surgery (3 or 4), Otolaryngology (5 or 6) --> Mechanical prophylaxis
    • High: General Surgery (>5), Otolaryngology (>7) --> Chemoprophylaxis & Mechanical prophylaxis

Choice of Treatment

• Treatment can be divided into mechanical and chemical prophylaxis along with encouraging early ambulation if possible. 
• At our institution, unless tissue is to be harvested from a donor leg, we routinely use mechanical compression sleeves for procedures under general anesthesia with or without chemical prophylaxis.
• If pharmacologic treatment is chosen, either low-dose unfractionated heparin or low-molecular weight heparin (LMWH) are commonly utilized as the treatment regimen.
• If Lovenox (enoxaparin, LMWH) is chosen, Kahn et al recommend dosing is routinely divided based on BMI: (Kahn et al.; Chest 2012)
  • BMI <40 kg/m², dosing is typically 30 mg subcutaneously
  • BMI >40 kg/m, dosing is typically 40 mg subcutaneously
  • These are references and can change based on factors such as renal function, etc. Consultation with pharmacist is encouraged.
• Alternatively, low-dose unfractionated heparin is used depending on availability of lovenox or potential complications. Dosing for low-dose unfractionaated heparin is routinely 5,000 units every 8-12 hours. (Lyman 2013, McLeod 2001)
• It has been recommended by Warkentin et al. that platelets and creatinine be monitored at the time of- and after-initiation of a heparin containing product. These evaluations monitor for heparin-induced thrombocytopenia and may warrant adjustment of dosing based on renal function. (Warkentin et al. 2008)
• If chemical prophylaxis is utilized for prevention of VTE perioperatively, it is widely accepted that treatment is initiated prior to incision in the operating room.
  • Additional prophylaxis treatment post-operatively may be considered and is based on many factors including the type of surgery performed, bleeding risk, and many others.
• To our knowledge, no studies have directly compared chemical agent of choice for Otolaryngology patients. 
• Current management (as of 5-14-2020):
  • For patients undergoing head and neck oncologic ablative and free tissue transfer procedures, we usually continue VTE prophylaxis until stable for discharge.
  • For patients undergoing cerebellopontine angle tumor resection, we initiate VTE prophylaxis 48 hours post-operatively on a case by case basis until stable for discharge. 

References

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https://www.mdcalc.com/caprini-score-venous-thromboembolism-2005

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