Identification of occult deep vein thrombosis before the placement of sequential compression devices.

Sir,

Trauma patients with multisystem injuries and a high injury severity score (ISS) have an increased risk of thromboembolic events. Safe and effective thromboprophylaxis is highly desirable to prevent deep vein thrombosis (DVT). Unfractionated heparin, low-molecular-weight heparin (LMWH), sequential compression devices (SCDs), and vena cava filters are used as prophylaxis in trauma patients.[1] We encountered a case wherein occult DVT was already present and SCD was applied as part of the protocol. Routine use of compression ultrasound (USG) to assess for lower extremity thrombus is justified to prevent such incidents as in our patient.

A 40- year-old male with moderate head injury, central cord syndrome and faciomaxillary injury was being managed conservatively in the ward for two weeks. He was admitted to the trauma intensive care unit (ICU) in view of tachypnoea and decreasing saturation. He had sequential organ failure assessment (SOFA) score of 11, pulse rate 130 per min, invasive blood pressure 80/60 mm Hg and SpO2 of 82%. He was not receiving LMWH for DVT prophylaxis and was given thromboprophylaxis only by mechanical compression device in view of head injury. On admission to the ICU as there was no evidence of DVT on clinical examination as a part of protocol, the staff nurse applied SCD on both the limbs. Routine USG colour Doppler of the lower limbs [Figure 1] was done which revealed left partial thrombus in the left common femoral vein extending into the profunda femoris and popliteal vein; right complete thrombus extending to the right common femoral vein, superficial femoral and popliteal vein. Computed tomography (CT) pulmonary angiography was done which revealed that right pulmonary artery had a filling defect at the junction of ascending and descending trunk and left descending trunk showed a large filling defect extending into segmental branches.

Figure 1

Ultrasound of left lower limb showing partial thrombus in the left common femoral vein

SCDs are safe alternatives to LMWH when anticoagulation with LMWH is contraindicated, as in patients with head injury. SCDs are well tolerated as a method of DVT prophylaxis, with no bleeding complications. SCDs target stasis and the fibrinolytic pathway which exacerbates the complications associated with DVT in trauma patients.[2]

Routine use of compression USG to assess for lower extremity thrombus is easily justifiable after the occurrence of such mishaps as in our patient. Despite even prophylactic methods with low-dose heparin (LDH) or SCD the incidence of DVT remains up to 21%[3] as demonstrated by Burns et al., with biweekly ultrasound scans. Bedside USG has achieved the contemporary role as a diagnostic tool for the assessment of DVT. All the patients should be screened for the presence of lower-extremity DVT before graded SCDs are placed on the legs as there is a risk of embolization of DVT from the legs on which SCDs have been placed.

Various studies have demonstrated that 10–100% of DVTs diagnosed by USG were not found on clinical examination or were asymptomatic.[45] There is an upcoming role of USG as a diagnostic modality for DVT. The American College of Chest Physicians (ACCP) Evidence-based clinical practice guidelines (2012) favour the combined use of pretest clinical probability assessment, D-dimer and USG to aid the diagnosis of DVT.[6] But ACCP (2012) guidelines do not recommend periodic surveillance with venous compression USG for major trauma patients (Grade 2C which is not a strong level of evidence).[7] However, ACCP guidelines (2008) do recommend USG screening in patients who are at high risk for venous thromboembolism (e.g., in the presence of a spinal cord injury, lower extremity or pelvic fracture, or major head injury), and who have received suboptimal thromboprophylaxis or no thromboprophylaxis (Grade 1C) as was our case.[1] Besides, the latest study by Azaretal has also recommended Duplex USG DVT screening of all critically ill trauma patients.[5]

We recommend screening of patients by compression ultrasound routinely to identify significant occult DVT (unrecognized thrombus capable of producing pulmonary embolism) before the placement of SCDs since clinical examination is not reliable. Search for more effective methods of thromboprophylaxis in patients in whom pharmacological thromboprophylaxis is contraindicated should continue as the current methods offer limited efficacy against DVT.