Venous thromboembolism prevention resident survival guide

# Overview
Venous thromboembolism (VTE) is a disease associated with morbidity and mortality; therefore, thromboprophylaxis is indicated among specific categories of patients at elevated risk for VTE.  VTE prophylaxis can be either pharmacological through the administration of medications such as low molecular weight heparin (LMWH) or fondaparinux among others, or mechanical through intermittent pneumatic compression or elastic stockings.  The decision to administer VTE prophylaxis, the duration, and the choice of prophylaxis depend on the reason for hospitalization such as medical illness, non orthopedic surgery, or orthopedic surgery, as well as on the estimated risks of subsequent VTE and bleeding.

# VTE Prevention in Non Surgical Patients

## Hospitalized Acutely Ill Medical Patients
Shown below is an algorithm depicting the indications and choices of VTE prophylaxis among acutely ill patients.  If VTE prophylaxis is recommended, it should be administered for the period of immobilization or hospital stay.  Do not extend the duration of the prophylaxis after the period of immobilization or hospital stay.  If pharmacological anticoagulation is needed, the choice of the drug should be guided by the patient preference, readiness for compliance and the practicality of the administration of frequent doses.
Abbreviations: BID: bis in die (twice daily); LDUH: Low dose unfractionated heparin; LMWH: Low molecular weight heparin; TID: ter in die (three times daily); VTE: Venous thromboembolism

## Assessment of the Risk of VTE
The subsequent risk of VTE can be estimated by risk scores, such as PADUA risk score and IMPROVE risk score.

### Padua Prediction Score for VTE
Shown below is a table depicting Padua predictive score for VTE among hospitalized medical patients.
The interpretation of the score is as follows:
- Score 4: High risk for VTE
- Score< 4: Low risk for VTE

### IMPROVE Predictive Score for VTE

### IMPROVE Associative Score for VTE
IMPROVE associative risk score assesses the risk of VTE among hospitalized medical patients. While the IMPROVE predictive score includes 4 independent risk factors for VTE which are present at admission, IMPROVE associative score includes 7 variables present either at admission or during hospitalization; however the timing of the presence of some of the factors compared to the onset of VTE is not available.

## IMPROVE Bleeding Risk Score
Shown below is a table depicting the IMPROVE risk score for bleeding among hospitalized medical patients.  The scores can be interpreted as such:
- Score 7: Elevated risk of bleeding
- Score <7: Not elevated risk of bleeding

## Hospitalized Critically Ill Patients
Shown below is an algorithm depicting the choices for VTE prophylaxis among critically ill patients.  Note that there is not a risk score to estimate the risk subsequent occurrence of VTE among critically ill patients.  In addition, routine compression ultrasound screening for DVT is not recommended among critically ill patients.  Do not extend the duration of the VTE prophylaxis after the period of immobilization or hospital stay.
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VTE: Venous thromboembolism

## Cancer in Outpatient
Shown below is an algorithm depicting VTE prophylaxis among cancer patients.  Note that, cancer patients with indwelling central venous catheters do not require VTE prophylaxis with neither low molecular weight heparin, low dose unfractionated heparin or vitamin K antagonists.
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VTE: Venous thromboembolism

## Chronically Immobilized Patients
No VTE prophylaxis is recommended among subjects who are chronically immobilized either at home or at a nursing home.

## Long Travel
Shown below is an algorithm for the indications of preventive measure for VTE among subjects undergoing a long travel.

## Asymptomatic Thrombophilia
VTE prophylaxis is not recommended among subjects with asymptomatic thrombophilia.

# VTE Prevention in Non Orthopedic Patients

## General and Abdominal-Pelvic Surgeries
Shown below is an algorithm depicting the indications and choices of VTE prophylaxis among patients undergoing general and abdominal-pelvic surgeries.  Note that inferior vena cava filter is not recommended.  In addition, surveillance compression ultrasound should not be done to screen for VTE.
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; UH: unfractionated heparin; VTE: venous thromboembolism

## Cardiac Surgery
Shown below is an algorithm depicting the indications and choices of VTE prophylaxis among patients undergoing cardiac surgery.
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VTE: venous thromboembolism

## Thoracic Surgery
Shown below is an algorithm depicting the indications and choices of VTE prophylaxis among patients undergoing thoracic surgery.
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VTE: venous thromboembolism

## Craniotomy
There is no validated risk score for the occurrence of subsequent VTE or for bleeding, particularly intracranial hemorrhage among patients undergoing craniotomy.  Since the risk for intracranial hemorrhage is the highest within the first 12 to 24 hours following craniotomy, pharmacological therapy should be delayed until the risk of bleeding subsides.

## Spinal Surgery

## Trauma
Shown below is an algorithm depicting the indications and choices of VTE prophylaxis among patients with major trauma.  Major trauma include traumatic brain or spine injury.  Note that inferior vena cava filter is not recommended.  In addition, surveillance compression ultrasound should not be done to screen for VTE.
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VTE: venous thromboembolism

# VTE Prevention in Orthopedic Patients

## Major Orthopedic Surgery
Shown below is an algorithm depicting VTE prophylaxis in patients undergoing major orthopedic surgeries which include total hip arthroplasty, total knee arthroplasty and hip fracture surgery.  Among patients who are not at elevated risk of bleeding, LMWH is the first line choice for VTE therapy.  Among patients who refuse LMWH injection or intermittent pneumatic compression device, apixaban or dabigatran can be administered. Do not consider inferior vena cava filter as VTE prophylaxis or screening with a compression ultrasound for VTE.
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VKA: Vitamin K antagonist; VTE: venous thromboembolism

### Assessment of Bleeding in Major Orthopedic Surgeries
There is no score to estimate the risk of bleeding in major orthopedic surgeries.  However, some factors have been identified to increase the risk of bleeding in this category of patients.  These factors include:
- Prior major bleeding
- Severe kidney failure
- Concomitant administration of an antiplatelet
- Bleeding during the current surgery which was difficult to control
- Extensive surgical dissection
- Revision surgery

## Isolated Lower-Leg Injuries
VTE prophylaxis is not recommended among patients who have isolated lower leg injuries distal to the knee.

## Knee Arthroscopy
VTE prophylaxis is not recommended among patients who undergo knee arthroscopy and who have no previous VTE episodes.