External pneumatic compression does not increase urokinase plasminogen activator after abdominal surgery

External pneumatic compression (EPC) devices prevent lower extremity deep venous thrombosis (DVT) by reducing stasis. There is a widely held belief that they also enhance endogenous fibrinolysis; however, recent studies of tissue plasminogen activator (the primary activator of fibrinolysis) and plasminogen activator inhibitor-1 (the primary inhibitor of fibrinolysis) failed to confirm this. The hypothesis of this study was that EPC devices increase the level of urokinase plasminogen activator (uPA), a second activator of fibrinolysis. This was a prospective trial in which 44 subjects who underwent major abdominal surgery were randomized to receive unfractionated heparin injections, thigh-length sequential EPC devices, or both for DVT prophylaxis. Prophylaxis was begun immediately before surgical incision and continued until postoperative day 5 or discharge. Venous blood samples were collected from an antecubital vein for measurement of systemic uPA levels and from the common femoral vein for measurement of regional uPA levels. Samples were collected the day before surgery, after induction of anesthesia but before surgical incision, and on postoperative days 1, 3, and 5. uPA levels (ng/mL) were measured with an enzyme-linked immunoassay. Baseline uPA levels (0.41 to 0.56 ng/mL; P >.05, analysis of variance with repeated measures) were similar among the three groups. uPA levels did not change after surgery in systemic or regional blood samples in any group. There were no significant differences in systemic or regional uPA levels in the groups treated with EPC devices relative to those treated with heparin at any time point (P >.05, analysis of variance with repeated measures). Enhancement of fibrinolysis with EPC devices remains unproven; the findings reported here suggest that effective DVT prophylaxis can only be assured when the devices are used in a manner that reduces venous stasis.     

Intermittent pneumatic calf compression for prevention of deep venous thrombosis in general abdominal surgery

A prospective randomized trial is described in 119 patients undergoing major abdominal general surgical procedures. Half of the patients were treated prophylactically with intermittent pneumatic calf compression, begun after the induction of anesthesia and continued until the patient was walking; the other half acted as controls. Deep venous thrombosis was detected by iodine-125 fibrinogen scanning and confirmed by venography, and did not differ significantly in the control and treated groups. One fatal pulmonary embolism occurred in each group. The presence of malignancy of the gastrointestinal tract did not influence the results. The findings suggest that pneumatic compression delayed the development of deep venous thrombosis postoperatively and that perhaps it should be continued until discharge from hospital.     

Effect of pneumatic compression on fibrinolysis after total hip arthroplasty

The purpose of this prospective randomized clinical study was to investigate the enhanced systemic fibrinolysis mechanism of venous thrombosis prevention by pneumatic compression after total hip arthroplasty. Fifty patients were randomized into one of two groups (one with pneumatic compression [n=25] and one without [n=25]). Blood was drawn from a radial arterial line immediately preoperatively (baseline), at skin closure, and 8 hours and 22 hours after the baseline sample. Serum determinations of antigen of tissue plasminogen activator and plasminogen activator inhibitor-1 were done using enzyme-linked immunosorbent assays. These data do not support the enhancement of systemic fibrinolysis mechanism for lowering thromboembolic risk after total hip arthroplasty by pneumatic compression devices. The results of this study showed no differences that were statistically significant between the two groups. The greatest difference was observed 8 hours after surgery for the plasminogen activator inhibitor-1 marker, (28.12 with compression versus 22.07 ng/mL without); however, this result was not statistically significant. The beneficial effect of mechanical compression is more likely achieved through increased flow, local fibrinolytic effects, or both.     

The effect of external pneumatic compression on regional fibrinolysis in a prospective randomized trial

INTRODUCTION: External pneumatic compression devices (EPC) prevent deep venous thrombosis (DVT) by reducing lower extremity venous stasis. Early studies suggested they also enhance fibrinolytic activity; however, in a recent study, EPC had no effect on systemic fibrinolysis in patients undergoing abdominal surgery. The hypothesis of this study was that EPCs enhance regional fibrinolysis in these subjects. METHODS: Forty-five patients (44 male, one female; mean age, 67 years) undergoing major abdominal surgery (35 bowel procedures, 10 aortic reconstructions) were prospectively randomized to one of three groups for DVT prophylaxis: subcutaneous heparin injections (HEP), thigh-length sequential EPC devices (EPC), or both (HEP+EPC). Prophylaxis was begun immediately before surgical incision and continued until postoperative day 5 or patient discharge. Venous blood samples were collected from the common femoral vein for measurement of regional fibrinolysis after induction of anesthesia but before initiation of prophylaxis, and on postoperative days 1, 3, and 5. A baseline sample was collected the day before surgery. Fibrinolysis was quantified with measurement of the activities of tissue plasminogen activator (tPA; the activator of fibrinolysis) and its inhibitor plasminogen activator inhibitor-1 (PAI-1) with amidolytic technique. RESULTS: tPA activity in all groups was normal at baseline; baseline PAI-1 activity was elevated. Within each prophylaxis group, no significant changes occurred in either tPA or PAI-1 activities after induction of anesthesia or after surgery compared with before surgery (P >.05, analysis of variance with repeated measures). No changes occurred between postoperative samples and after anesthesia within each group. No significant enhancement of fibrinolysis, manifested as either increased tPA activity or decreased PAI-1 activity, occurred in either EPC group compared with the HEP group at any time point (P >.05, analysis of variance with repeated measures). No differences were noted when surgery was performed for malignant disease versus nonmalignant disease. CONCLUSION: In this study, enhanced regional fibrinolysis in the lower extremities could not be detected with the use of EPCs, as measured with tPA and PAI-1 activity in common femoral venous blood samples. EPC devices do not appear to prevent DVT with fibrinolytic enhancement; effective and safe prophylaxis is provided only when the devices are used in a manner that reduces lower extremity venous stasis.     

The fibrinolytic effects of intermittent pneumatic compression: mechanism of enhanced fibrinolysis.

BACKGROUND AND OBJECTIVES: Intermittent pneumatic compression (IPC) is an effective form of deep vein thrombosis prophylaxis for general surgery patients. The antithrombotic effect of IPC is thought to be the result of increased venous velocity and stimulation of endogenous fibrinolysis. However, the mechanism of enhanced fibrinolytic activity and the relative effects on normal and postthrombotic veins have not been defined. The purposes of this study are 1) to quantify changes in fibrinolytic activity with IPC; 2) to study the mechanism of fibrinolytic enhancement with IPC; and 3) to evaluate whether postthrombotic patients have the same capacity for fibrinolytic enhancement with IPC as do normal subjects. METHODS: Twelve volunteers (6 normal and 6 postthrombotic) had 5 IPC devices applied for 120 minutes in random fashion, 1 per week x 5 weeks. The devices included single-chamber, sequential, foot, calf, and long-leg compression. Subjects had an indwelling antecubital venous cannula placed for blood drawn at baseline, 60, 120, and 180 minutes after IPC devices were applied. Global fibrinolytic activity (euglobulin fraction, fibrin plate assay), tissue plasminogen activator (tPA) antigen (Ag) and activity (Act), plasminogen activator inhibitor-1 (PAI-1) Ag and Act, alpha-2-antiplasmin-plasmin complexes, and von Willebrand factor (vWF) antigen were assayed. RESULTS: A striking elevation in fibrinolytic activity was noted at 180 minutes with all devices in normal subjects and postthrombotic patients (p = 0.01-0.0001); however, baseline and stimulated fibrinolytic activity was attenuated in postthrombotic patients (<0.03). The tPA-Act increased only in normal subjects (3.8 +/- 1.9%) (p = 0.057), despite a decrease in plasma tPA-Ag, which was observed in both normal subjects (-12.4 +/- 3.8%) (p = 0.009) and patients (-17.2 +/- 3.1%) (p = 0.001). PAI-1-Ag decreased in both normal subjects (-13.4 +/- 3.8%) (p = 0.007) and patients (-12.0 +/- 3.1%) (p = 0.013) with a marked reduction in PAI-1-Act in both normal subjects (p = 0.003) and patients (p = 0.004). There were no changes in vWF, and alpha-2-antiplasmin-plasmin complexes increased only in postthrombotic patients (p = 0.021). CONCLUSIONS: Stimulation of endogenous fibrinolytic activity occurs after IPC, both in normal subjects and postthrombotic patients; however, baseline and overall fibrinolytic response in postthrombotic patients is reduced. The mechanism of increased fibrinolytic activity is likely because of a reduction in PAI-1, with a resulting increase of tPA activity.     

Intermittent pneumatic foot compression can activate blood fibrinolysis without changes in blood coagulability and platelet activation

BACKGROUND: Intermittent pneumatic foot compression (IPC) is a useful technique for prophylaxis of peri-operative venous thromboembolism. The aim of this study was to determine the effect of IPC on blood coagulation/fibrinolysis and platelet function using a blood viscometer (Sonoclot) and a platelet aggregation monitor (WBA analyzer(TM)), respectively. Using the same blood samples, serum levels of tissue-type plasminogen activator (t-PA), thrombomodulin (TM) and activated protein C (APC) were also measured. METHODS: The soles and legs of each subject (n = 8) were compressed for 3 s (130 mmHg) at a 0.3-Hz interval using an IPC device. Parameters were measured 2 min before and at the end of 60-min compression. RESULTS: Parameters of the Sonoclot time-to-peak were shortened and clot retraction rate was increased significantly by IPC, whereas the other parameters did not change. These results indicate that IPC can activate blood fibrinolysis but not coagulability. A parameter of the WBA analyzer PATI (platelet aggregatory threshold index) did not change, indicating that IPC cannot activate platelet function per se. The concentration of t-PA decreased slightly but significantly. A decrease in the concentration of t-PA can lead to activation of fibrinolysis. Other humoral parameters did not change, indicating that IPC has no effect on endothelial function. Although neither blood coagulability nor platelet function were affected by IPC, fibrinolytic activity increased slightly, probably by activation of t-PA function. CONCLUSION: IPC is useful for prophylaxis for thromboembolism by activation of blood fibrinolysis as well as inhibition of blood stasis.     

External pneumatic calf compression reduces deep venous thrombosis in patients with ruptured intracranial aneurysms

We evaluated the ability of intermittent external pneumatic calf compression to prevent deep venous thrombosis after subarachnoid hemorrhage from ruptured intracranial aneurysms. Fifty-six subarachnoid hemorrhage patients not given external pneumatic calf compression were compared with 90 patients who had calf compression after their subarachnoid hemorrhages. Both groups of patients were on strict bedrest for 7 to 21 days after aneurysm rupture, and both received epsilon-aminocaproic acid, 30 to 36 g/day intravenously, until operation. The risk factors in the two groups were similar, and the nursing and medical care did not seem to differ. Of patients without external pneumatic compression, 18% had venographically proven deep venous thrombi, which contrasts with 6% of patients receiving calf compression. This was a significant difference (P less than 0.05; chi 2). These retrospective data suggest that external pneumatic calf compression helps to prevent deep venous thrombosis in patients with subarachnoid hemorrhage when delayed operation, bedrest, and antifibrinolytic agents are used.     

The pneumatic compression test and modified pneumatic compression test in the diagnosis of carpal tunnel syndrome

There are no precise criteria for the diagnosis of carpal tunnel syndrome (CTS): the history is useful but the value of the various provocative tests is questionable. The purpose of this study was to examine the diagnostic value of a new provocative test, the 'modified pneumatic compression test' in CTS. The study group consisted of 37 patients with 50 symptomatic CTS hands. A control group of 50 healthy volunteers was recruited. The diagnosis was based on a combination of the history, the clinical findings on examination and electrophysiological criteria. Sensitivity for the pneumatic compression and the modified pneumatic compression tests were 68% and 84%, respectively. Specificities for these tests were 97% and 95%, respectively. The modified pneumatic compression test demonstrated high sensitivity and specificity for CTS. This test facilitated the diagnosis and was easy to use. It may reduce referrals for neurophysiology testing, and so reduce costs.     

Effects of a protease inhibitor, ulinastatin, on coagulation and fibrinolysis in abdominal surgery

Purpose Ulinastatin is well known to inhibit the activity of polymorphonuclear leukocyte elastase (PMNE). The PMNE concentration correlates with the activities of coagulation and fibrinolysis. The purpose of the present study was to investigate the effects of ulinastatin, a protease inhibitor, on coagulation and fibrinolysis in abdominal surgery. Methods Thirty patients, aged 40 to 70 years, with American Society of Anesthesiologists (ASA) physical status I or II, scheduled for major abdominal surgery, were enrolled. Anesthesia was induced with midazolam and thiopental, and was maintained with sevoflurane, nitrous oxide in oxygen, and an epidural block. An infusion of ulinastatin, 6000 units·kg⁻¹ in 30 min, was started 1 h after the start of surgery in the ulinastatin group (15 patients). In the control group (15 patients), no protease inhibitors were infused. White blood cell count; platelet count; prothrombin time; activated partial thromboplastin time; and plasma concentrations of PMNE, antithrombin (AT), fibrin/fibrinogen degradation product (FDP), fibrinogen, plasminogen, plasmin-_α2 plasmin inhibitor complex (PIC), and thrombin-antithrombin complex (TAT) were measured before, at the end of, and 12 h after surgery. Results TAT, PIC, and FDP after surgery were significantly lower in the ulinastatin group than in the control group. AT was decreased in the control group but not in the ulinastatin group, with significant differences between the two groups. Conclusion Ulinastatin could inhibit coagulation and fibrinolysis in abdominal surgery.     

Intermittent pneumatic compression in immobile patients

The purpose of this study is to stress the value of using intermittent pneumatic compression (IPC) in immobile patients. The use of IPC helps prevent limb oedema and the associated skin changes frequently seen on the legs of the immobile patient. Oedema formation is caused by an increase of fluid extravasation, while skin changes including leg ulcers are mainly because of a deficiency of the venous and lymphatic pumps. Conventional compression stockings and bandages impede leg swelling but are less efficient in supporting the deficient veno-lymphatic pump when patients are unable to move. In this situation, actively compressing the limb using IPC is a very meaningful and effective treatment option. Because of a lack of literature on the specific indication of IPC in immobile patients, experimental studies and randomised controlled trials in similar situations are reviewed. IPC is a very effective although underused treatment modality, especially in immobile, wheelchair-bound patients. By inflation and deflation of the air-filled garments, IPC produces cycles of pressure waves on the leg, thus mimicking the working and resting pressures applied by compression bandages. IPC not only reduces leg swelling but also augments the veno-lymphatic pump, which is essential for the restoration of the damaged microcirculation of the skin.     

压力梯度长袜和间歇充气装置预防恶性肿瘤患者术后下肢深静脉血栓形成的效果

目的 观察单纯应用压力梯度长袜（CS）或与间歇充气装置（IPC）联合使用预防恶性肿瘤患者术后下肢深静脉血栓（DVT）形成的效果及可能的机制。方法 胸科、泌尿外科、肝胆外科恶性肿瘤根治手术患者240例，随机分为4组：对照组、单纯CS组、CS＋IPC全程组、CS＋IPC术后组，每组60例。术后3～8d内行双下肢深静脉超声检查，记录DVT例数及血栓发生部位（大腿或小腿）。随机选择对照组和CS＋IPC全程组各15例患者，分别于术前、切皮后2h及术后24h各采集外周静脉血2ml，测定D-二聚体（D-D）、纤溶酶原激活物抗原（tPA-Ag）、纤溶酶原激活物抑制物（PAI）、血管性血友病因子（vWF）、凝血酶原时间（PT）和活化部分凝血活酶时间（APTT）。结果 术后3-8d对照组、CS＋IPC全程组、CS＋IPC术后组和单纯CS组DVT发生率分别为49．3％、15．0％、23．3％和30．0％（P〈0．05）。所有发生DVT患者中，除CS组发现1例近端DVT外，其余均为远端DVT。发生DVT患者年龄、卧床时间、危险因素个数等与未发生血栓患者相比差异有统计学意义（P〈0．05）。凝血，纤溶指标：与对照组比较，切皮后2h，CS＋IPC全程组vWF升高，D-D、tPA-Ag降低（P〈0．05），术后24h对照组和cs＋IPC全程组间D—D、vWF、tPA-Ag及PAI差异无统计学意义。结论 CS＋IPC全程或术后使用均能降低高危患者术后DVT的发生，其中CS＋IPC全程使用预防效果最好，可能与IPC增加纤溶活性有关。     

Perspectives in sequential pneumatic compression of the lower extremities (SCD) for laparoscopic surgery

During most cases of laparoscopic surgery, a pneumoperitoneum of 12-14 mm Hg CO2 is established. Although not always detected in healthy patients, a pneumoperitoneum will cause clinically relevant pathophysiological changes. Among other side effects, a pneumoperitoneum will alter the venous blood return from the lower extremities and depress cardiac function. Results from experimental and clinical studies concerning the influence of a pneumoperitoneum on venous blood return and cardiac function are reviewed and a simple model of cardiac function impairment during laparoscopic surgery with a pneumoperitoneum is presented. Sequential pneumatic compression of the lower extremities is effective in reducing venous stasis during and after conventional surgery. Several clinical trials determined the hemodynamic effect of intraoperative SCD (sequential compression device) during laparoscopic surgery. In the following text the results of these studies are summarized and possible implications for the clinical use of SCD in laparoscopic surgery are discussed. Although potential benefits of SCD-therapy have been shown only in studies of low methodological quality, intraoperative SCD-therapy is recommended during prolonged laparoscopic surgery.     

Evaluation of intermittent pneumatic compression devices

Venous blood flow rate in the lower extremity after applying different pneumatic compression devices was evaluated. Five healthy individuals, aged 21-35, were recruited for this study. The ability of six different pneumatic compression devices to increase femoral venous blood flow velocity was analyzed and compared to that of active and passive foot dorsiflexion. Baseline venous blood flow velocity was measured using an ATL Duplex Doppler before leg compression. Venous blood flow velocity was then monitored before, during, and after each compression cycle. Average peak venous velocity increased >200% on dorsiflexion of the ankle. Among the investigated devices, the increase in venous velocity varied significantly. Design of compression chambers enabling compression on the lateral and medial aspects of the calf produced an increase in venous velocity closest to active foot dorsiflexion. Foot compression devices produced the smallest increase in venous velocity. The relative effectiveness of pneumatic compression devices, particularly with respect to increasing venous blood flow in the lower extremity, may correlate well with how closely the device simulates the physiologic contraction of the calf muscles. Clinical trials are needed to further compare the effectiveness of these devices, as other less readily measured factors play a role in thromboprophylaxis.