Complications of General Surgery
0039--6109/91 $0.00
+ .20
Deep Venous Thrombosis and Pulmonary Embolism Alfred V. Persson, MD, * Robert J. Davis, BA, t and J. Leonel Villavicencio, MD:j:
All surgical patients are at risk for the development of deep venous thrombosis and its major complication, pulmonary embolism. Several factors, when present, increase the chance of the development of postoperative deep venous thrombosis. They include a history of deep venous thrombosis, prese!lce of a malignant process (especially metastatic disease), increasing age, cigarette smoking, obesity, prolonged bed rest, and general anesthesia. Several attempts have been made to classifY and quantitate these risk factors. 6, 17 All of these methods have an underlying theme: the risk of the development of deep venous thrombosis postoperatively increases with the number of risk factors present. Several effective methods of prophylaxis are available. Because multiple risk factors are involved in the pathogenesis of deep venous thrombosis, no single prophylactic method will be effective in all patients in all situations. 29, 30 The approach must be flexible and individualized to accommodate the patient's surgical situation and the particular risk factors.
PROPHYLAXIS OF DEEP VENOUS THROMBOSIS IN SURGICAL PATIENTS Graduated Compression Stockings Use of compression stockings from the distal leg to the proximal leg increases the blood flow in the proximal femoral vein. 27 This effect is thought to reduce the potential for stasis and the incidence of deep venous *Head, Section of Peripheral Vascular Surgery, Lahey Clinic Medical Center, Burlington, Massachusetts; Clinical Instructor in Surgery, Harvard Medical School; and Associate Clinical Professor of Surgery, Boston University School of Medicine, Boston, Massachusetts tResearch Assistant, Section of Peripheral Vascular Surgery, Lahey Clinic Medical Center, Burlington, Massachusetts :j:Professor of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland; and Director, Venous and Lymphatic Surgical Clinic, Walter Reed Army Medical Center, Washington, DC The opinions or assertions contained therein are the private ones of the authors and are not to be construed as official or as reflecting the views of the Army or Department of Defense.
Surgical Clinics of North America-Vol. 71, No.6, December 1991
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thrombosis. 25 Typically, stockings are put on before surgery and are worn after surgery until the patient is fully ambulatory. Both thigh-high and knee-high stockings are used. No appreciable difference exists in the effectiveness of above-the-knee as opposed to below-the-knee stockings to reduce the incidence of postoperative deep venous thrombosis. 35 Stockings, although somewhat cumbersome, are inexpensive, convenient, and free of bleeding complications. However, when used alone, compression stockings only modestly reduce the incidence of postoperative deep venous thrombosis in the general surgical patient. One article 7 suggested a reduction in the incidence of postoperative deep venous thrombosis of only 11% when either calf- or full-length stockings were the only means of prophylaxis. The major disadvantage of compression stockings and one that is often overlooked is that, when used alone, they do not adequately protect the high-risk patient, and therefore graduated compression stockings are considered only an adjuvant prophylactic measure. Intermittent Pneumatic Compression Devices Under normal circumstances, a considerable portion of venous blood in the leg is propelled proximally by contraction of the muscles of the calf. When a patient is under general anesthesia or spinal anesthesia or is confined to bed, the natural venous pump is lost. Intermittent pneumatic compression devices serve as an external mechanical substitute for the natural calf venous pump. Typically, an inflatable sleeve is placed around the lower leg and intermittently inflated to a predetermined pressure for a predetermined time (Fig. 1). Use of these devices increases the venous blood flow in the proximal femoral vein. The goal of intermittent compression devices is to minimize stasis, thereby reducing the risk of the development of deep venous thrombosis.1 5 This increase in the flow of blood in the common femoral vein is equal in devices that compress only the lower leg compared with devices that compress both the lower and the upper leg. A recent paper27 comparing the effect of external compression devices and graduated compression stockings reported that the effect of the two devices is not additive and that use of stockings does not further augment blood flow in the common femoral vein. At the Lahey Clinic, intermittent external pneumatic compression devices are routinely used in the lower leg position only. Use of the device is initiated preoperatively and continued postoperatively until the patient is fully ambulatory. In our experience, noncompliance by the patient has been minimized by making the medical support staff and the patient aware of the importance of the therapy. A discussion of the prevention of deep venous thrombosis is part of the nursing services' preoperative teaching given to surgical patients. Members of the peripheral vascular laboratory are responsible for providing the devices. External intermittent pneumatic compression devices are a worthwhile prophylactic alternative when anticoagulant therapy is contraindicated. The devices are simple to use and relatively inexpensive.
DEEP VENOUS THROMBOSIS AND PULMONARY EMBOLISM
1197
Figure 1. Intermittent pneumatic compression device with compression sleeve covering lower leg.
Heparin The most widely used and studied prophylactic agent is heparin. The major pharmacologic effect of heparin is as an antithrombin III agonist, enhancing the effect of naturally occurring antithrombin III. The antithrombin III-heparin complex binds to thrombin, neutralizing its activity in the clotting cascade and decreasing the amount available to form clot. Circulating heparin is also thought to neutralize factors IX, X, and XI. An initial dose of heparin of 5000 units is typically given subcutaneously 1 or 2 hours before operation and is continued after operation every 12 hours until the patient is fully ambulatory. Although bleeding has been reported l3,37 as a complication, it is rarely of importance. Many reports7,8, 19, 20, 28, 36 during the last two decades have described the beneficial prophylactic effect of heparin (Table 1). Subcutaneously administered lowdose heparin has been shown30, 36 to reduce the incidence of postoperative deep venous thrombosis by approximately 50% in general surgical patients. Prophylactic low-dose heparin is commonly used in prevention of deep venous thrombosis. We employ both heparin and intermittent pneumatic compression devices in general surgical patients. The intermittent compression device is the more common of the two methods. In a randomized study of 76 patients, we found no difference between the two modalities in reducing the incidence of postoperative deep venous thrombosis. No postoperative deep venous thrombosis was reported in either group. The incidence of deep venous thrombosis in the nonrandomized nontreated group during the same period of time was 4%. Initiation of some form of
1198
ALFRED V. PERSSON ET AL.
Table 1. Thromboprophylactic Effect of Low-Dose Heparin in General Surgery* SOURCE
Ansay et al (1977) Bergqvist and Hallbook (1980) Gallus et al (1973) Gallus et al (1976) International Multicentre Trial
NO. OF PATIENTS
INCIDENCE OF THROMBOSIS
(%)
Control
Heparin
50 97
63 27
26 13
0039--6109/91 $0.00
+ .20
Deep Venous Thrombosis and Pulmonary Embolism Alfred V. Persson, MD, * Robert J. Davis, BA, t and J. Leonel Villavicencio, MD:j:
All surgical patients are at risk for the development of deep venous thrombosis and its major complication, pulmonary embolism. Several factors, when present, increase the chance of the development of postoperative deep venous thrombosis. They include a history of deep venous thrombosis, prese!lce of a malignant process (especially metastatic disease), increasing age, cigarette smoking, obesity, prolonged bed rest, and general anesthesia. Several attempts have been made to classifY and quantitate these risk factors. 6, 17 All of these methods have an underlying theme: the risk of the development of deep venous thrombosis postoperatively increases with the number of risk factors present. Several effective methods of prophylaxis are available. Because multiple risk factors are involved in the pathogenesis of deep venous thrombosis, no single prophylactic method will be effective in all patients in all situations. 29, 30 The approach must be flexible and individualized to accommodate the patient's surgical situation and the particular risk factors.
PROPHYLAXIS OF DEEP VENOUS THROMBOSIS IN SURGICAL PATIENTS Graduated Compression Stockings Use of compression stockings from the distal leg to the proximal leg increases the blood flow in the proximal femoral vein. 27 This effect is thought to reduce the potential for stasis and the incidence of deep venous *Head, Section of Peripheral Vascular Surgery, Lahey Clinic Medical Center, Burlington, Massachusetts; Clinical Instructor in Surgery, Harvard Medical School; and Associate Clinical Professor of Surgery, Boston University School of Medicine, Boston, Massachusetts tResearch Assistant, Section of Peripheral Vascular Surgery, Lahey Clinic Medical Center, Burlington, Massachusetts :j:Professor of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland; and Director, Venous and Lymphatic Surgical Clinic, Walter Reed Army Medical Center, Washington, DC The opinions or assertions contained therein are the private ones of the authors and are not to be construed as official or as reflecting the views of the Army or Department of Defense.
Surgical Clinics of North America-Vol. 71, No.6, December 1991
1195
1196
ALFRED
V.
PERSSON ET AL.
thrombosis. 25 Typically, stockings are put on before surgery and are worn after surgery until the patient is fully ambulatory. Both thigh-high and knee-high stockings are used. No appreciable difference exists in the effectiveness of above-the-knee as opposed to below-the-knee stockings to reduce the incidence of postoperative deep venous thrombosis. 35 Stockings, although somewhat cumbersome, are inexpensive, convenient, and free of bleeding complications. However, when used alone, compression stockings only modestly reduce the incidence of postoperative deep venous thrombosis in the general surgical patient. One article 7 suggested a reduction in the incidence of postoperative deep venous thrombosis of only 11% when either calf- or full-length stockings were the only means of prophylaxis. The major disadvantage of compression stockings and one that is often overlooked is that, when used alone, they do not adequately protect the high-risk patient, and therefore graduated compression stockings are considered only an adjuvant prophylactic measure. Intermittent Pneumatic Compression Devices Under normal circumstances, a considerable portion of venous blood in the leg is propelled proximally by contraction of the muscles of the calf. When a patient is under general anesthesia or spinal anesthesia or is confined to bed, the natural venous pump is lost. Intermittent pneumatic compression devices serve as an external mechanical substitute for the natural calf venous pump. Typically, an inflatable sleeve is placed around the lower leg and intermittently inflated to a predetermined pressure for a predetermined time (Fig. 1). Use of these devices increases the venous blood flow in the proximal femoral vein. The goal of intermittent compression devices is to minimize stasis, thereby reducing the risk of the development of deep venous thrombosis.1 5 This increase in the flow of blood in the common femoral vein is equal in devices that compress only the lower leg compared with devices that compress both the lower and the upper leg. A recent paper27 comparing the effect of external compression devices and graduated compression stockings reported that the effect of the two devices is not additive and that use of stockings does not further augment blood flow in the common femoral vein. At the Lahey Clinic, intermittent external pneumatic compression devices are routinely used in the lower leg position only. Use of the device is initiated preoperatively and continued postoperatively until the patient is fully ambulatory. In our experience, noncompliance by the patient has been minimized by making the medical support staff and the patient aware of the importance of the therapy. A discussion of the prevention of deep venous thrombosis is part of the nursing services' preoperative teaching given to surgical patients. Members of the peripheral vascular laboratory are responsible for providing the devices. External intermittent pneumatic compression devices are a worthwhile prophylactic alternative when anticoagulant therapy is contraindicated. The devices are simple to use and relatively inexpensive.
DEEP VENOUS THROMBOSIS AND PULMONARY EMBOLISM
1197
Figure 1. Intermittent pneumatic compression device with compression sleeve covering lower leg.
Heparin The most widely used and studied prophylactic agent is heparin. The major pharmacologic effect of heparin is as an antithrombin III agonist, enhancing the effect of naturally occurring antithrombin III. The antithrombin III-heparin complex binds to thrombin, neutralizing its activity in the clotting cascade and decreasing the amount available to form clot. Circulating heparin is also thought to neutralize factors IX, X, and XI. An initial dose of heparin of 5000 units is typically given subcutaneously 1 or 2 hours before operation and is continued after operation every 12 hours until the patient is fully ambulatory. Although bleeding has been reported l3,37 as a complication, it is rarely of importance. Many reports7,8, 19, 20, 28, 36 during the last two decades have described the beneficial prophylactic effect of heparin (Table 1). Subcutaneously administered lowdose heparin has been shown30, 36 to reduce the incidence of postoperative deep venous thrombosis by approximately 50% in general surgical patients. Prophylactic low-dose heparin is commonly used in prevention of deep venous thrombosis. We employ both heparin and intermittent pneumatic compression devices in general surgical patients. The intermittent compression device is the more common of the two methods. In a randomized study of 76 patients, we found no difference between the two modalities in reducing the incidence of postoperative deep venous thrombosis. No postoperative deep venous thrombosis was reported in either group. The incidence of deep venous thrombosis in the nonrandomized nontreated group during the same period of time was 4%. Initiation of some form of
1198
ALFRED V. PERSSON ET AL.
Table 1. Thromboprophylactic Effect of Low-Dose Heparin in General Surgery* SOURCE
Ansay et al (1977) Bergqvist and Hallbook (1980) Gallus et al (1973) Gallus et al (1976) International Multicentre Trial
NO. OF PATIENTS
INCIDENCE OF THROMBOSIS
(%)
Control
Heparin
50 97
63 27
26 13
