Deep vein thrombosis is a venous reflux disorder caused by abnormal clotting of blood in deep veins, which can occur in all parts of the veins of the body, mostly in the lower extremities; thrombus dislodgement can cause pulmonary artery embolism, and the two together are called venous thromboembolism.
I. Overview and epidemiological characteristics
1.Clinical manifestation of DVT.
DVT is mainly manifested as sudden swelling, pain and increased soft tissue tension of the affected limb; it is aggravated after activity and can be reduced by elevating the affected limb, and there is often pressure pain at the site of venous thrombosis. if DVT is not diagnosed and treated in time after the onset, it may lead to gradual aggravation of the symptoms and signs of the affected limb, which may induce shock or even lead to venous gangrene in serious cases.
Once dislodged, the venous thrombus may enter and block the pulmonary artery with the blood flow, causing the clinical manifestations of PE. DVT in the proximal part of lower extremity (rouge vein or proximal part) is the main source of PE thromboembolism.
2, the majority of VTE is no obvious clinical symptoms, Knudson et al. reported that 76% of the DVT of polytrauma patients do not have typical clinical symptoms, Swann and Black reported that 85% of the DVT of trauma patients are without typical clinical symptoms, so more than 2/3 of VTE patients are missed.
II. Risk factors
The three elements of venous thrombosis are venous injury, venous blood stasis and blood hypercoagulation, and these three risk factors are often present in trauma patients.
First, trauma, especially fractures, can directly or indirectly cause rupture or irritation of the venous vessel wall; second, braking, bed rest, paralysis, and hemorrhagic shock can easily lead to venous stasis; and finally, blood hypercoagulation begins almost immediately after injury and lasts throughout the perioperative period.
Anderson and Spencer pooled extensive literature data and classified each risk factor for the development of VTE into 3 classes according to OR: strong risk factors (OR>10) include: fracture (hip or thigh), hip and knee arthroplasty, major general surgery, major trauma, and spinal cord injury; moderate risk factors (OR: 2-9) include: arthroscopic knee surgery, central venous catheterization, chemotherapy, congestive heart failure or respiratory failure, hormone replacement therapy, malignancy; weak risk factors (OR<2) include: bed rest for longer than 3 d, prolonged sitting (train or airplane, etc.), advanced age, laparoscopic surgery (cholecystectomy, etc.), obesity, pregnant women, varicose veins.
III. Risk assessment scale
The clinician’s risk of VTE is not reliable based on experience alone, and the trauma population is highly variable. Therefore, it is necessary to artificially classify patients into different risk strata, i.e. pretestprobability, simply by medical history, degree of trauma and clinical signs.
The most widely used clinical scale is the Wells scale, but this scale is based on outpatients and does not fully cover risk factors specific to trauma patients, so the Wells scale is not applicable to in-hospital trauma patients.
In 1997, Greenfield et al. proposed a venous thrombosis risk score for trauma patients that included four factors: medical history, degree of trauma, medically induced injury, and age.
A prospective study of 2281 trauma patients showed that the RAPT score is a good assessment of the risk of VTE in trauma patients, with RAPT ≤5 being low risk and DVT incidence of 3.6%, 5-14 being intermediate risk and DVT incidence of 16.1%, and >14 being high risk and DVT incidence of 40.7%.
Four, auxiliary examination
1, D-dimer detection: D-dimer is a specific molecular marker of thrombin activation and secondary fibrinolysis, i.e. cross-linked fibrin degradation products. D-dimer is significantly elevated in patients with acute VTE, but a variety of non-thrombotic factors can also lead to elevated D-dimer, such as infection, malignancy, surgery and trauma, so its specificity for the diagnosis of VTE is not strong.
The sensitivity of D-dimer for the diagnosis of DVT is 82%-94%, and the specificity is 44%-72%; the sensitivity for the diagnosis of PE is 86%-97%, and the specificity is 41%-70%. negative D-dimer can exclude the possibility of VTE, and the positive value for the confirmation of VTE is not high, so it is recommended to confirm the diagnosis after further imaging examination.
2.Venous ultrasound: the sensitivity and accuracy of venous ultrasound are high, and it is the first choice of imaging means for DVT diagnosis. It is divided into proximal ultrasound and distal ultrasound of lower extremity, whole lower extremity ultrasound, iliac vein ultrasound and large abdominal vein ultrasound according to different examination sites, and the most commonly used in clinical practice is proximal ultrasound and whole lower extremity ultrasound.
Although there are some false negative results of ultrasound compared to venography, its sensitivity and specificity are high (97% sensitivity and 94% specificity). Because venous ultrasound is noninvasive, simple, repeatable, free of complications, and inexpensive, it is recommended as the imaging test of choice for the diagnosis of DVT.
3.Venography: Venography used to be the “gold standard” for the diagnosis of DVT, through the injection of iodine-containing contrast agent into the dorsal foot vein, the filling defect of the vascular lumen (intraluminalfillingdefect) is observed, and the site, scope, formation time and collateral circulation of the thrombus are determined.
However, phlebography is an invasive test, costly, difficult to spread in primary hospitals, and contraindicated in patients with renal insufficiency and contrast allergy. Because of these disadvantages, intravenous angiography is rarely used in clinical practice. However, for some patients who are difficult to confirm the diagnosis or exclude DVT, intravenous imaging can still be chosen.
4.CT venous imaging (computertomographyangiography, CTA): Generally, the spiral CT scan after the injection of contrast agent through the elbow vein can clearly show the morphology of target vessels. CTA can examine both pulmonary artery and large abdominal vein thrombosis, and can be used to diagnose both DVT and PE.
The meta-analysis showed that the sensitivity of CTA was 95.2% and the specificity was 95.9%. CTA is recommended as an optional imaging test to confirm the diagnosis of DVT or PE.
5.MRI venous imaging: MRI venous imaging can accurately show iliac, femoral and carotid veins without contrast, but it is not satisfactory for calf veins. The results of meta-analysis show that the sensitivity of MRI venous imaging is 91.5% and the specificity is 94.8%.
V. DVT screening procedure
Thrombotic risk assessment and screening are recommended for all trauma orthopedic patients.
1. RAPT assessment is recommended for all trauma patients during hospitalization: patients are divided into low VTE risk group (RAPT ≤ 5 points) and intermediate and high risk VTE risk group (RAPT > 5 points) according to the score.
2.Rapid D-dimer testing is recommended for all patients in the emergency: the cut-off value for D-dimer negativity varies among hospitals according to the testing method, equipment and reagents, and it is generally considered that D-dimer <500 μg/L by ELISA is negative, while the elderly should use age × 10 μg/L as the negative criterion.
3, D-dimer negative patients according to the results of the RAPT score to determine the next screening program.
(i) If the patient is at low risk, no further thrombosis-related testing is recommended for such patients.
(ii) If the patient is at intermediate or high risk, dynamic observation of D-dimer changes every 2 d or review of proximal or total lower extremity venous ultrasound after 1 week is recommended.
③If the dynamic observation of D-dimer elevation is positive, then proceed to step 4.
4.Patients with positive D-dimer are recommended to have proximal or whole lower extremity venous ultrasound
①If the lower extremity venous ultrasound indicates proximal venous thrombosis, direct treatment is recommended without venography to confirm the diagnosis; if the lower extremity is independent distal venous thrombosis, repeat ultrasound is recommended to exclude the proximal range of thrombosis instead of immediate treatment (patients with independent distal DVT should be treated immediately if repeat ultrasound and treatment for false positive results are not convenient, patients with low risk or severe symptoms and risk of proximal thrombosis). (patients at risk of proximal thrombus extension should be treated immediately).
If the patient has negative lower extremity venous ultrasound, it is recommended to dynamically observe the change of D-dimer or recheck the lower extremity venous ultrasound after 1 week; if the D-dimer rapidly decreases to negative, it is recommended to decide the next screening step according to the RAPT score (same as step 3); if the result of rechecking D-dimer is still positive, it is recommended to further screen for DVT in sites other than lower extremity veins.
5. Screening methods for venous thrombosis in sites other than lower extremity veins: abdominal large vein + iliac vein ultrasound, abdominal vein CTA, MRI venous imaging or upper extremity vein ultrasound are available; if the patient is confirmed to have DVT in sites other than lower extremity veins by imaging, treatment according to relevant guidelines or clinical pathway is recommended; if no evidence of DVT is still found, dynamic monitoring of D-dimer or reexamination of lower extremity veins after 1 week is recommended. Ultrasound.
VI. DVT treatment
(I) Treatment of preoperative confirmed DVT
In orthopedic trauma patients with preoperative diagnosis of DVT (fresh proximal thrombosis), if emergency or time-limited surgery is needed, it is recommended that surgery be performed after placement of an inferior vena cava filter and anticoagulation be given if there is no contraindication to anticoagulation; if emergency or time-limited surgery is not needed, anticoagulation be given for 4-6 weeks after surgery for those without contraindication to anticoagulation, and for those with contraindication to anticoagulation, it is recommended that an inferior vena cava filter be placed and re-evaluated after 1 week: if contraindication to anticoagulation no longer exists, then anticoagulation be given for 4-6 weeks. If anticoagulation is no longer contraindicated, surgery will be given after 4-6 weeks of anticoagulation therapy. If anticoagulation is still contraindicated, surgery after placement of inferior vena cava filter will be judged in the context of whether emergency or deadline surgery is needed at this time.
(B) Treatment of postoperative confirmed DVT
If a traumatic orthopedic patient is diagnosed with DVT after surgery, he/she will be treated according to the Chinese DVT treatment guidelines (2nd edition), including.
1.Anticoagulation: For postoperative DVT in traumatic orthopedic patients, anticoagulation treatment for 3 months.
2.Inferior vena cava filter: For most DVT patients, routine application of inferior vena cava filter is not recommended; for those who have contraindication to anticoagulation, or have complications, or PE occurs despite adequate anticoagulation, placement of inferior vena cava filter is recommended.
3.Thrombolysis: For acute stage central or mixed DVT, catheter-contact thrombolysis is preferred under the premise of good systemic condition, expected survival ≥ 1 year, and less risk of bleeding. If the conditions of catheter thrombolysis are not available, systemic thrombolysis is feasible.
4.Surgical thrombosis: When the iliofemoral vein and its main side branches are blocked by thrombus, the venous return is severely obstructed, and the clinical manifestation is femoral cyanosis, the thrombus should be removed surgically immediately. For patients with central type or mixed type DVT within 7d of the onset of the disease, with good systemic condition and no important organ dysfunction, surgical thrombus retrieval is also possible.