In too deep: Understanding deep vein thrombosis

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1 LPN1109_DVT.qxd:urvi 29/09/09 4:56 PM Page 10 In too deep: Understanding deep vein thrombosis Two million people will experience some form of deep vein thrombosis, or DVT, this year, so it s easy to see why DVT is such an important topic. Here are the tools you need to understand DVT from how it happens and who s at risk to what you can do to help these patients. By James Stockman, RN, BSN Student Texas Wesleyan University Graduate Program of Nurse Anesthesia Fort Worth, Tex. DEEP VEIN THROMBOSIS (DVT) is a clot that forms most commonly within the deep veins of the legs, but it can also occur in the pelvis or arms. DVT has been increasingly in the spotlight for the last 15 years due to three factors: the rising cost of healthcare, an increase in preventive medicine, and our aging population. In this article, I ll fill you in on DVT, including what you need to know about taking care of a patient who already has it and how to prevent at-risk patients from developing it. But first, let s review the pathophysiology of DVT. You re so vein The veins of the body consist of the superficial veins that run near the surface of the skin, and the deep veins, such as the great saphenous and popliteal veins, 10

2 LPN1109_DVT.qxd:urvi 29/09/09 4:56 PM Page 12 that are located underneath the muscles and run parallel to the arteries. Smaller veins connect the superficial and deep veins and help move blood from the skin to the deep veins. Blood is then moved back to the heart with the aid of valves in the superficial and deep veins that allow unidirectional flow. Various factors influence blood flow through the legs: Valves in the veins prevent backflow, while walking and muscle movement in the legs aid stationary, as in standing or sitting for long periods, there s the potential for a thrombus to form. Let s now take a look at blood flow to better understand thrombus formation. Don t slow the flow! Anything that alters the strength of the blood vessel wall can slow blood flow and cause DVT. Think of the vascular system as an intertwining water hose. Normally, water flows every time you sit down, curl your legs, or cross your arms, you reduce blood flow, which can cause small clots to form. Normally, the body immediately breaks down these clots. However, when stasis of blood (venous stasis), vessel wall injury, and hypercoagulability the three factors known as Virchow s triad are present, an abnormal thrombus will most likely form. How does the thrombus form? Let s take a look at that next. [ ] The most serious complication of DVT is pulmonary embolism (PE), in which the dislodged thrombus obstructs the pulmonary artery bed. blood flow back to the heart. Since blood flow is already slowed as it s squeezed from the connecting veins into the deep veins, there s a high risk of clot (thrombus) formation if any further slowing of the flow occurs. Any time blood slows or is Picturing venous thrombosis through the hose without any difficulty but if you kink the hose, you reduce the flow of water. Over time, dirt and other impurities build up within the hose and add to the reduced flow. The same principle applies to the vascular system. So Tunica intima Tunica media Tunica adventitia Thrombus Valve Endothelium Internal elastic membrane Smooth muscle External elastic membrane A thrombus among us Mechanical or physiologic damage to the vessel wall leads to platelet activation. Examples of mechanical damage include high velocity trauma in which bones are broken and surgery, especially orthopedic or abdominal surgery. Examples of physiologic damage include hypertension, in which the vessel wall weakens over time, and phlebitis, in which a vein is inflamed. The platelets adhere to one another and clump together, forming a thrombus (see Picturing venous thrombosis). After a thrombus forms, it flows in the body and is either dissolved over time or grows and becomes large enough to occlude a vessel. If the thrombus occludes a vessel, it s known as an embolus. After an embolus forms, the blood behind the blockage slows and the veins expand to accommodate an increase in volume. This leads to a general pooling of blood that slows the blood further and causes more clots to form. Ultimately, the drainage of the lymphatic system slows, leading to edema of the affected extremity. So who s at risk for developing DVT? That s up next. Risks, risks everywhere... Patients who are most at risk for DVT are those undergoing major 12

3 LPN1109_DVT.qxd:urvi 29/09/09 4:56 PM Page 13 surgery, especially orthopedic surgery. Other at-risk patients include those who smoke or have lung disease, diabetes, blood disorders, and peripheral vascular disease. But remember, any hospitalized patient is at risk for DVT, especially those who ll be immobile for an extended period of time or are of advancing age. If your patient has any one of the three factors in Virchow s triad, there s the potential for DVT. See Which surgical patients are at risk for DVT? for more information. It s a sign How do you know if your patient has DVT? And if he does, is he at risk for more complications? Let s now review signs and symptoms to be alert for and then we ll take a look at potential complications. DVT may be difficult to recognize immediately because many patients don t exhibit signs and symptoms or their symptoms are nonspecific. Signs and symptoms include: edema or swelling of the affected extremity redness pain or tenderness an increase in the temperature of the affected extremity compared with the rest of the body cyanosis and mottling of the skin due to stagnant blood flow. Although Homans sign (pain with dorsiflexion of the foot) has historically been used to assess DVT, it s not a reliable or valid sign; in fact, the literature suggests that up to 50% of patients with DVT don t have a positive Homans sign. It can get complicated The most serious complication of DVT is pulmonary embolism (PE), in which the dislodged thrombus obstructs the pulmonary artery bed. PE can be life-threatening and may require mechanical ventilation. If Which surgical patients are at risk for DVT? Risk level Patient population Highest High Moderate Low Patients undergoing hip or knee surgery Patients with multiple risk factors undergoing surgery Patients with major trauma Patients over age 60 undergoing surgery Patients age 40 to 60 with additional risk factors undergoing surgery Patients with additional risk factors undergoing minor surgery Patients age 40 to 60 with no additional risk factors undergoing surgery Patients younger than age 40 with no additional risk factors undergoing minor surgery your patient complains of any of these signs and symptoms, notify the healthcare provider immediately: severe dyspnea tachypnea chest pain cough hemoptysis (coughing up blood). Another complication occurring in 40% to 60% of patients with DVT is postthrombotic syndrome. Caused by a combination of factors, such as back flow of blood related to faulty valves and blockage that remains in the vessel, signs and symptoms of this syndrome include pain, increased swelling, skin ulcers, and hyperpigmentation. How long postthrombotic syndrome persists depends on the patient s ability to form collateral circulation around any remaining embolus. Treatment for this condition is palliative, including anticoagulation therapy and elevating the affected extremity to help decrease swelling and pain. Assessment = early detection Let s say you re worried that your overweight patient with diabetes who doesn t want to get out of his bed to ambulate is developing DVT. What do you do? Careful assessment will help detect early signs of a venous disorder of the legs. Assess for: limb pain a feeling of heaviness functional impairment ankle engorgement edema differences in leg circumferences bilaterally from thigh to ankle an increase in the surface temperature of the leg, particularly the calf or ankle areas of tenderness or superficial thrombosis. One of the most reliable physical indications of DVT is unilateral edema of the extremity. Measure the extremity and compare your findings with baseline measurements to detect an increase in circumference. Changes should be reported and documented. Diagnosis: DVT Because DVT is often difficult to detect clinically, diagnostic studies may be indicated. If the healthcare provider suspects DVT, he may order a venous ultrasound of the patient s legs, magnetic resonance imaging (MRI), a venogram, or a D-dimer test. November/December l LPN

4 LPN1109_DVT.qxd:urvi 29/09/09 4:56 PM Page 14 Let s take a closer look at these tests. Duplex venous ultrasonography, which may be performed at the bedside, is one of the simplest diagnostic tests for DVT. Ultrasound imagery can reveal a thrombus in a deep vein; the Doppler ultrasound measures the blood flow velocity in veins and can detect flow abnormalities. Although a duplex study is noninvasive and relatively simple to perform, its accuracy depends on the technician s skill. If the ultrasound is negative for DVT and the healthcare team still suspects that the patient has DVT, a venogram may be indicated to make a definitive diagnosis. MRI is another noninvasive study that can be used to detect DVT in the proximal deep veins. Whether to use this test or a venogram depends on the patient s clinical findings; MRI is more useful than venography in patients with suspected DVT of the inferior vena cava or pelvic veins. Although it s being replaced by ultrasound, the venogram is still considered by many healthcare When anticoagulant therapy is a no-no Anticoagulant therapy is contraindicated if your patient has: bleeding from the gastrointestinal, genitourinary, respiratory, or reproductive systems hemorrhagic blood dyscrasias an aneurysm severe trauma alcoholism recent or impending surgery of the eye, spinal cord, or brain severe liver or kidney disease recent cerebrovascular hemorrhage an infection an open ulcerative wound an occupation that involves a significant risk for injury recently delivered a baby. providers to be the gold standard for diagnosing DVT. During this invasive test, the patient is placed on a fluoroscopic table that s usually tilted 45 degrees, and a contrast medium is injected into a superficial foot vein. A clinician observes the flow of contrast medium by fluoroscopy and takes X-rays; if the contrast medium doesn t fill the veins normally, acute DVT is confirmed. Complications of venography include hypersensitivity reactions to the contrast medium, acute renal failure because of the volume of contrast medium used, and extravasation of the contrast medium (especially in patients with a history of arterial insufficiency because of tissue necrosis and ulceration). The risk of acute renal failure is higher in older patients and in patients with diabetes, hyperuricemia, or multiple myeloma. D-dimer test is a blood test to measure fibrin degradation fragments generated by fibrinolysis. An elevated D-dimer level indicates a thrombotic process but isn t specific to DVT. This test is useful as an adjunct to noninvasive testing. If the patient has a low clinical probability of DVT and a negative D-dimer test, DVT can be ruled out without an ultrasound. It turns out your suspicions were correct your patient has DVT. What s the next step? Let s look at treatment options next. Anticoagulation is A-OK The treatment goals for DVT are to prevent the thrombus from growing and fragmenting, which increases the risk of PE; to prevent recurring thrombi; and to let the body s own fibrinolytic system work. Anticoagulant therapy, with unfractionated heparin, low-molecular-weight heparin (LMWH), or oral anticoagulants such as warfarin (Coumadin), is the first-line treatment. Thrombolytic therapy or the factor XA inhibitor fondaparinux (Arixtra) may also be used. Depending on the patient s risk factors, anticoagulant therapy may last from 6 months to 1 year if he has idiopathic DVT or indefinitely if he continues to have recurring thrombi. Let s take a closer look. Unfractionated heparin is administered by I.V. infusion for 5 to 7 days to prevent the growth of a thrombus and the development of new thrombi. An electronic infusion device is used to prevent the inadvertent infusion of large volumes, which can cause hemorrhage. Unfractionated heparin can also be given subcutaneously to prevent the development of DVT. The dosage of unfractionated heparin depends on the patient s activated partial thromboplastin time, international normalized ratio (INR), and platelet count. Heparin is at an effective (therapeutic) level when the patient s partial thromboplastin time is 1.5 times normal. Patients receiving unfractionated heparin for a long period of time (several days to weeks) are at risk for a sudden decrease in platelet count (30%) known as heparin-induced thrombocytopenia (HIT). If HIT develops, heparin must be discontinued. Associated with fewer bleeding complications and a lower risk of HIT than unfractionated heparin, LMWH, such as enoxaparin (Lovenox), may be used instead to prevent thrombus growth and new thrombi formation. Given in one or two subcutaneous injections per day, doses are adjusted according to the patient s weight and are based on the specific product and facility protocol. LMWH is more expensive than unfractionated heparin, but it can be used safely in pregnant women and patients who take it may be more mobile. 14

5 LPN1109_DVT.qxd:urvi 29/09/09 4:56 PM Page 15 An oral anticoagulant, such as warfarin (a vitamin K antagonist), is typically administered with heparin therapy. Once the therapeutic level is reached, heparin can be discontinued. If the patient requires long-term therapy, warfarin is frequently used. The dosage of warfarin depends on the patient s prothrombin time and INR; the therapeutic level is reached when the patient s prothrombin time is 1.5 to 2 times normal or the INR is 2 to 3. Thrombolytic therapy dissolves thrombi in 50% of patients. A thrombolytic, such as activase (Alteplase) or reteplase (Retavase), is given within the first 3 days after acute thrombosis. Thrombolytics cause less long-term damage to the venous valves and reduce the incidence of postthrombotic syndrome; however, they have a higher risk of bleeding than heparin. If bleeding can t be stopped, thrombolytic therapy must be discontinued. Unlike LMWH, which acts on thrombin and factor Xa, fondaparinux only inhibits factor Xa. Because it doesn t affect platelets, fondaparinux doesn t cause HIT. Fondaparinux is given subcutaneously at a fixed dose once a day and is excreted unchanged by the kidneys; therefore, it must be used with caution in patients with renal insufficiency and it s contraindicated in patients with renal failure. Surgery may be necessary if anticoagulant or thrombolytic therapy is contraindicated, the patient is at high risk for PE, or his venous drainage is so compromised that permanent damage is likely (see When anticoagulant therapy is a nono). Thrombectomy, or removal of the thrombus, is the procedure of choice under these circumstances. During this procedure, a catheter is used to deliver a thrombolytic directly into the clot to dissolve it. A vena cava filter may also be placed through the catheter into the groin, just below the junction of the inferior vena cava and the lowest renal veins, to trap large emboli and prevent PE. About the size of a quarter, this filter made of wire mesh catches any clots that break off the DVT and head for the lungs via the inferior vena cava. A vena cava filter for short-term use has recently been introduced, designed to be removed once the increased risk of PE subsides. So what can you do to help your patient who s receiving anticoagulant therapy? Let s delve into the care of a patient with DVT next. Take care When caring for a patient with DVT, you must: Monitor for potential complications, such as bleeding or HIT. Spontaneous bleeding anywhere in your patient s body is the most common complication of anticoagulant therapy. Bleeding from the kidneys, bruises, nosebleeds, and bleeding gums are early signs of excessive heparin dosage. To immediately reverse the effects of heparin, the healthcare provider may order I.V. protamine sulfate. Protamine sulfate is most effective in reversing the effects of unfractionated heparin, but it may also be used in patients receiving LMWH. If your patient receiving warfarin experiences bleeding, the healthcare provider may order oral or low-dose I.V. vitamin K or an infusion of fresh frozen plasma or prothrombin concentrate. HIT is another complication you must watch out for. Early signs and symptoms of HIT include a decreasing platelet count, the need for increasing doses of heparin to maintain the therapeutic level, and hemorrhagic complications (skin necrosis at the [ ] Teach your patient the signs and symptoms of PE, such as shortness of breath, chest pain, blue nail beds, and tachypnea. injection site or sites distal to the thrombus, skin discoloration, hematomas, purpura, and blistering). If your patient develops HIT, the healthcare provider may order a direct thrombin inhibitor, such as I.V. lepirudin (Refludan) or argatroban. Monitor for drug interactions. If your patient is taking an oral anticoagulant, you must monitor his medication schedule because many medications and supplements accelerate or inhibit the effects of warfarin. Provide pain relief. Depending on the extent and location of the thrombus, your patient may be on bed rest for 5 to 7 days. To promote circulation and increase comfort, periodically elevate his feet and lower legs above his heart. Help him perform active and passive leg exercises, particularly with the calf muscles, to increase venous flow. Apply warm, moist packs to the affected leg, as ordered, to reduce the discomfort of the thrombus. An analgesic may also be ordered to control pain. Encourage early ambulation. Once he s ambulatory, instruct your patient to avoid sitting for more than 2 hours at a time. He should walk at least 10 minutes every 1 to November/December l LPN

6 LPN1109_DVT.qxd:urvi 29/09/09 4:56 PM Page 16 2 hours if possible to help prevent venous stasis. Perform discharge teaching. Educate your patient about the signs and symptoms of DVT to report, such as new swelling or increased swelling of the affected limb, skin breakdown, pain, and weak or absent pulses. Also teach him the signs and symptoms of PE, such as shortness of breath, chest pain, blue nail beds, and tachypnea. Instruct him to go to the ED immediately if he experiences any of these symptoms. Inform your patient about the risk of bleeding associated with anticoagulant therapy and the signs and symptoms to be alert for, such as changes in mental status, a racing pulse, and extremely pale skin (see Patient teaching for anticoagulants). If your patient is going home on warfarin, tell him to avoid foods high in vitamin K, such as avocados, broccoli, brussels sprouts, cabbage, green onions, liver, and green leafy vegetables. And make sure he understands that he ll need regular blood draws to monitor his prothrombin time and INR. If he s going home on unfractionated heparin, he ll need his partial prothrombin time monitored on a Patient teaching for anticoagulants monthly basis as well. If your patient is going home on LMWH or fondaparinux, teach him the proper technique for subcutaneous injections into the abdomen (2 inches from the umbilicus) and make sure he knows to rotate the injection sites. Have him demonstrate the technique back to you. Let him know it s common to experience some bruising around the injection sites but to contact his healthcare provider if the bruises begin to spread. Finally, assist your patient with setting up follow-up appointments, which may include a computed axial tomography scan of his chest to check for PE and magnetic resonance venography or a venous Doppler scan to monitor the status of the thrombus. But how about steps you can take to prevent your at-risk patients from developing DVT? Let s take a minute to review prevention strategies. Teach your patient who has been prescribed an anticoagulant the following: Take the anticoagulant at the same time each day, usually between 8 a.m. and 9 a.m. Because other medications affect the action of anticoagulants, don t take vitamins, cold medicines, antibiotics, aspirin, mineral oil, or anti-inflammatory drugs without consulting your healthcare provider. Avoid alcohol because it may change your body s response to the anticoagulant. Avoid food fads, crash diets, or marked changes in eating habits. Avoid injury that can cause bleeding. If you experience faintness, dizziness, increased weakness, severe headaches or abdominal pain, reddish or brown urine, red or black stool, any unusual bleeding, nosebleeds, bruises that enlarge, or rash, contact your healthcare provider immediately. Contact your healthcare provider before having dental work or elective surgery and inform the dentist or surgeon that you re taking an anticoagulant. For women, contact your healthcare provider if you suspect you re pregnant. Wear or carry identification indicating the anticoagulant you re taking. Keep all appointments for blood tests. Your role in prevention Elastic compression stockings, which exert sustained, evenly distributed pressure over the calves to help increase blood flow in the deep veins, are usually ordered for patients with venous insufficiency to prevent DVT. They may be kneehigh, thigh-high, or like pantyhose. The healthcare provider may order short-stretch elastic wraps instead, which are applied from the toes to the knee in an overlapping spiral pattern using a one- or two-layer system. Intermittent pneumatic compression devices may also be used with elastic compression stockings to prevent DVT. These devices consist of plastic knee- or thigh-high leg sleeves attached to air hoses and an electric controller. The leg sleeves fill with air to apply pressure to the ankle, calf, and thigh. If your patient is receiving compression therapy, inspect his skin for signs of irritation and his calves for tenderness whenever you remove the stockings or wraps. Report any skin changes or tenderness to the healthcare provider immediately. The moral of the story: Prevention DVT is a serious, but preventable, condition. With diligent care, your patient with DVT will not only recover, but avoid recurrence as well. And with an eye on prevention, your at-risk patients will be less likely to develop DVT. LPN Selected references Day MW. Recognizing and managing deep vein thrombosis. Nursing. 2003;33(5): Pathophysiology Made Incredibly Visual! Philadelphia, PA: Lippincott Williams & Wilkins, 2008: Smeltzer SC, Bare BG, Hinkle JL, Cheever KH. Brunner and Suddarth s Textbook of Medical-Surgical Nursing.11th ed. Philadelphia, PA: Lippincott Williams & Wilkins;2007: Surgical Care Made Incredibly Visual! Philadelphia, PA: Lippincott Williams & Wilkins; 2007:185. Stockman J. In too deep: understanding deep vein thrombosis. Nursing Made Incredibly Easy! 2008; 6(2): Turka J. Is this on the level? Nursing Made Incredibly Easy! 2006;4(4):7-9. Wound Care Made Incredibly Visual! Philadelphia, PA: Lippincott Williams & Wilkins;2008:107. Zajac PM. Going with the flow: warfarin. Nursing Made Incredibly Easy! 2004;2(4):