HOW WOULD YOU SUSPECT DEEP VEIN THROMBOSIS ( DVT ) IN A PATIENT HAVING SPINAL CORD INJURY ?
B ) OUTLINE MANAGEMENT OF DVT ?
A 2 INTRODUCTION
1 Deep venous thrombosis and subsequent PE remain significant causes of morbidity and mortality in spinal cord injured patients.
2 The incidence of DVT in patients with acute SCI was reported to be greater than 50% in early prospective studies with the incidence of fatal PE estimated as high as 5%.
3 The prevalence of DVT in acute SCI has been found to range from 14% to 100 % and from 9% to 90%
4 The clinical diagnosis of DVT and PE are often unrealiable and diagnostic testing is necessary to confirm the diagnosis.
5 Diagnostic testing varies from center to center, but 3 tests for DVT have become important - venous ultrasound, venography, and the D-dimer assay
6 for PE 2 commonly used tests are the ventilation/perfusion scan and the spiral CT scan.
7 Venography is considered the definitive test for DVT but is an invasive study.
VV IMP 8 Venous ultrasound is cheap and noninvasive, can be done as a screen or serially to monitor the patient. Sensitivity is only 73% for distal clots, but 95% for the more dangerous proximal clots.
9 The D-dimer assay is a rapid, noninvasive, and inexpensive test and measures a fibrin degradation product, D-dimers, as fibrin is in the main component of thrombosis formation.
A ) D-dimer test is highly sensitive, but lacks specificity because D-dimers are found in other disease states, reducing the specificity of the test.
10 A positive diagnosis of DVT can only be made if venogram is positive or if venous ultrasound is positive of 2 or more sites of proximal vein.
11 Nuclear ventilation/perfusion scans are often used to diagnose a PE and the likelihood of a positive diagnosis increases with the size, shape, and number of deflects on perfusion scanning with a normal ventilation scan.
12 A spiral CT scan is a quick CT scan of the entire thorax in 1 breath-hold and is most accurate when the PE is large.
13 The high risk of DVT in acute SCI patients is a consequence of the simultaneous presence of all 3 components of Virchow’s triad: hypercoagulability, stasis, and intimal (venous inner wall) injury, with stasis being the greatest concern.
14 VT most commonly begins with a calf DVT.
15 Although only 20% of DVTs extend into the proximal veins,these result in over 80% of symptomatic DVTs.
16 Distal calf DVTs which do not extend proximally rarely are a sources of PEs, so that they are much less worrisome.
17 VV IMP Proximal (ie, at the level of knee or above) DVTs continue to be the primary source of concern.
18 PE is reported in 8% to 14% of patients with an acute SCI, with the majority being asymptomatic or unrecognized.
19 Symptomatic PEs tend to be relatively large, with reported mortality rates of up to 5%.
ETIOPATHOPHYSIOLOGY
1 Patients with spinal cord injury (SCI) have a higher risk of thromboembolic disease related to the Virchow triad (ie, venous stasis, hypercoagulability, intimal injury).
2 Stasis from paralyzed muscles and hypercoagulability remain the 2 major factors contributing to the development of thrombosis in this patient population.
3 Other common risk factors for venous thromboembolism (VTE) include the following :
A ) Immobilization – The muscles in the legs act as pumps to maintain venous return from the lower extremities; inactivity of these muscles leads to venous stasis
B ) Advanced age
C ) Congestive heart failure – Cardiac output is reduced, as is venous return from the legs
D ) Previous VTE
E ) Surgical procedure of lower extremity/pelvis
F ) Cancer/malignancy - VTE prophylaxis is not utilized fully in patients undergoing oncologic surgery a cohort study shows , appropriate prophylaxis is given more often to patients treated by high-volume surgeons at high-volume hospitals.
G ) Oral contraceptive use/pregnancy
H ) Trauma (eg, multiple trauma, spinal cord injury, burns, lower extremity fractures) – Direct mechanical injury to the lower extremities may lead to blood clot formation
I ) Delayed initiation of thromboprophylaxis
CLINICAL EVALUATION
A ) Typically, the hallmark of deep vein thrombosis (DVT) is a rapid onset of unilateral leg swelling; however, swelling of the lower extremities may be bilateral.
B ) Edema may be the only presenting symptom.
C ) Leg pain is nonspecific and includes a vast differential diagnosis. This is generally not a useful diagnostic symptom in patients with insensate lower extremities following spinal cord injury.
D ) Unfortunately, overall, the diagnostic properties of the clinical examination are poor.
E ) Clinical findings are absent in 50% of patients with confirmed DVT.
F ) However, although it is virtually impossible to distinguish DVT from other processes, the following findings should raise clinical suspicion -
1 VV IMP Leg swelling that is principally unilateral but may be bilateral, with a circumferential increase of the affected leg by at least 3 cm
2 Tenderness on compression of the calf muscles or over the course of the deep veins in the thigh
3 Increased temperature over the calf or thigh
4 Pain during forced dorsiflexion of the foot (Homan sign), although this is a nonspecific and insensitive test
5 Low-grade fever that cannot be explained after investigation of other possible sources
6 Superficial thrombophlebitis felt as a palpable cord and/or superficial venous distention at the knee, groin, or anterior abdominal wall
7 The clinical signs and symptoms of pulmonary embolism (PE) may be the primary manifestation in patients with confirmed DVT.
A ) Symptoms may include pleuritic chest pain, dyspnea, hemoptysis, and feelings of impending doom. Further physical signs of PE may include the following:
Tachycardia
Tachypnea
Hypoxia
Change in mental status
Pleural friction rub, pleural effusion
Fever
Cyanosis
Rales
DIFFERENTIALS
Other conditions in the differential diagnosis include the following -
1 Achilles Tendon Injuries and Tendonitis
2 Bursitis
3 Cellulitis
4 Heterotopic Ossification
5 Lymphedema
6 Superficial Thrombophlebitis
DIAGNOSTIC TESTS
A ) D dimer assays -
1 are a useful adjunct to non invasive testing for suggested deep vein thrombosis
2 are formed when crosslinked fibrin contained in the thrombus is proteolysed by plasmin
3 are are highly sensitive, and have a high negative predictive value.
4 D-dimer assays rule out DVT if the results are negative, but the assays are less helpful if the results are positive, especially in trauma patients vv imp .
B ) Impedance plethysmography (IPG) is a noninvasive test that generates no images, relying instead on unfamiliar technology.
1 This test is less sensitive than other tests for detecting DVT of the calf muscle, has less sensitivity and specificity than Doppler ultrasonography, and is less sensitive to incomplete obstruction of a vein by DVT.
2 In addition, extrinsic compression may give a positive result.
C ) Radiologic Studies
The following imaging studies may be used in the diagnosis of thromboembolic disease: radiocontrast venography, Doppler ultrasonography, I-125 fibrinogen scintigraphy, and ventilation/perfusion scanning.
1 Radiocontrast venography
Radiocontrast venography is the criterion standard for the diagnosis of deep vein thrombosis (DVT). This is a costly, invasive procedure that may have adverse effects, including pain. There is potential for contrast-mediated thrombosis and dye allergy.
2 Doppler ultrasonography
Doppler ultrasonography has become the preferred test in the diagnosis of DVT.
A ) It is a noninvasive and sensitive (98-100%) method for the diagnosis of proximal DVT.
B ) Doppler ultrasonography allows direct imaging of major veins and assessment of flow velocity in these veins.
C ) Its diagnostic accuracy compares favorably with that of venography, but it is dependent on operator expertise.
3 I-125 fibrinogen scintigraphy
Iodine-125 (125 I) fibrinogen scanning has the greatest sensitivity for calf vein DVT.
However, this imaging modality is rarely used in the clinical setting. Disadvantages include cost, a 24-hour delay from injection to reading, failure to detect established thrombi, and the danger of viral transmission.
V/Q scanning
Ventilation/perfusion lung scanning is indicated as part of the diagnostic evaluation of pulmonary embolism (PE).
A definitive diagnosis occurs if the results are normal or if there is a high probability, especially if clinical suspicion is confirmed by results.
Low or intermediate probability scan results require further evaluation (with, for example, lower extremity Doppler ultrasonography or pulmonary angiography).
B ) MANAGEMENT / TREATMENT
A ) TREATMENT / MANAGEMENT ACCORDING TO EVIDENCE - APPLICATION OF EVIDENCE BASED MEDICINE
1 There is level 4 (limited) evidence that the use of sequential pneumatic compression devices or gradient elastic stockings reduces the risk of venous thromboemboli post-SCI.
2 There is level 1 evidence (based on 1 small RCT) that rotating treatment tables reduces the incidence of venous thrombi in acute SCI patients.
3 There is level 4 evidence that comprehensive prophylactic treatment combining external pneumatic compression, gradient pressure stockings and low-dose heparin reduces venous thrombosis risk post-SCI.
4 There is level 3 evidence that inferior vena cava filters reduce the risk of PE in high-risk SCI patients.
5 There is level 4 evidence that enoxaparin, administered subcutaneously, is safe, cost-effective and less labor-intensive than intravenous heparin for acute DVTs post-SCI.
6 There is level 2 evidence (based on 1 low-quality RCT and 1 non-RCT) that 5000 IU of unfractionated heparin given subcutaneously every 12 hours is no more effective than placebo as prophylaxis against venous thrombosis post-SCI.
7 There is level 1 evidence (based on 1 RCT) that an adjusted (higher) dose of subcutaneous heparin is more effective as prophylaxis against venous thromboembolism than the administration of 5000 IU subcutaneous heparin every 12 hours; however, the adjusted dose appears to be associated with a higher incidence of bleeding complications.
8 There is level 1 evidence (based on 2 RCTs) that LMWH, in particular enoxaparin, is more effective than standard subcutaneous heparin at reducing venous thromboembolic events
9 There is level 4 evidence that 40mg daily enoxaparin, used prophylactically, is no more effective than 30mg daily at reducing the incidence of deep venous thrombosis; the 2 doses also appear similar with respect to bleeding complications.
10 There is level 1 evidence (based on 1 RCT) that enoxaparin is no more effective than dalteparin at reducing the risk of DVT; and, again, there is no difference in the rate of bleeding complications.
GUIDELINES
Guidelines based on best evidence for DVT prophylaxis in SCI include the use of sequential compression devices for 2 weeks and anticoagulants for 8 to 12 weeks after injury.
IDEAL TIME
DVT prophylaxis should be instituted within 72 h post-injury.
B ) RATIONALE / METHODS FOR THROMBOPROPHYLAXIS IN SPINAL CORD INJURY
1 MECHANICAL -
A ) Pneumatic compression devices ( also called sequential compression devices ) - increases lower extremity venous return , thereby reducing venous stasis - has to be used continuosly
B ) Graduated compression stockings
Improves lower extremity venous return and helps to control edema but should be used continuously for the effectiveness and should be thoroughly examined
C ) Other mechanical methods
Involves intermittent compression of the feet to increase venous blood flow in the proximal leg veins
DISADVANTAGES
1 poor compliance
2 skin breakdown in pxs with sensory loss
3 greater complexity and cost
2 ANTICOAGULANT -
Should be started within 72 hrs of injury
Prophylactic low dose unfractionated heparin is associated with 40 fold greater risk of thrombocytopenia
So , adjusted dose heparin is more effective
LDUH - 5000 U every 8 hrs
ENOXAPARIN - 30 mg every 12 hrs
3 ORAL VIT K ANTAGONISTS ( WARFARIN )
Should not be used in early phase
4 DIRECT ORAL ANTICOAGULANTS
are not recommended for acute phase but is required in post acute phase
5 COMBINED - PCD WITH OR WITHOUT ANTICOAGULANTS SHALL BE USED AS SOON AS POSSIBLE UNTIL OTHERWISE CONTRAINDICATED
DURATION
ANTICOAGULANT Prophylaxis should be continued at least 8 weeks after injury in pxs with limited mobility
6 INFERIOR VENA CAVA FILTERS
not be used as a primary in thromboprophylaxis in SCI
7 COMPRESSION HOSE
A ) elastic stockings distribute pressure uniformly over the extremity, improve lower extremity venous return, help to control edema, require that the integrity of underlying skin be examined daily, and are ineffective alone.
B ) Use compression hose with all patients for the first 2 weeks following spinal cord injury.