A comparison of preoperative and intraoperative vein mapping sizes for arteriovenous fistula creation.

BACKGROUND: Duplex ultrasound (DUS) mapping of the veins and arteries of the upper extremity is a well-established practice in arteriovenous fistula creation for long-term hemodialysis access. Previous publications have shown that vein diameters varying from 2 to 3 mm are predictive of success. Regional anesthesia is known to result in vasodilation and thus to increase the diameter of upper extremity veins. This study compares the sizes of veins measured by preoperative DUS mapping with those obtained after regional anesthesia to determine whether intraoperative DUS results in increased vein diameters and thus changes in the operative plan. A second goal was to determine whether such changes resulted in functional access. METHODS: This was a prospective observational study conducted between July 2013 and December 2014. Consecutive patients were preoperatively mapped and then intraoperatively mapped after administration of a regional anesthetic. Comparison of vein mapping sizes and comparison of preoperative plan and operative procedure based on the preoperative and intraoperative DUS mapping, respectively, were analyzed with a repeated-measures linear model. Significance testing was two sided, with a significance level of 5%. RESULTS: Sixty-five patients with end-stage renal disease underwent placement of arteriovenous access with preoperative and intraoperative DUS mapping after regional anesthesia. Comorbidities were representative of the vascular population. After regional anesthesia, intraoperative mid forearm and distal forearm cephalic veins were significantly larger than their respective preoperative measurements. Average increase in diameter of the mid forearm cephalic vein and distal forearm was 0.96 mm (P < .001) and 0.50 mm (P = .04), respectively. There was a significant difference in the number and configuration of arteriovenous accesses (P < .0001). There was more than a twofold significant increase in radial artery-based access procedures concomitant with a significant reduction of brachial-based access procedures and a reduction in graft access procedures. Overall functional access rate was 63%, and patency rates were comparable to those reported in the literature. CONCLUSIONS: The routine use of intraoperative DUS mapping after regional anesthesia is recommended to determine the optimal access site for chronic hemodialysis access. Identifying additional access options not seen with physical examination and preoperative DUS mapping will provide end-stage renal disease patients with more fistula options and hence a longer access life span for a lifelong disease.

Governmental regulations and radiation exposure.

BACKGROUND: The use of radiation for medical purposes falls under the purview of the Food and Drug Administration (FDA) and individual states. Enhanced regulations are in place to promote the right exam for the right reason at the right time for every patient exposed to medical x-rays. METHODS: The February 2010 FDA initiative to reduce unnecessary radiation exposure from fluoroscopy, CT, and nuclear medicine studies is reviewed along with regulations currently in place. RESULTS: Facilities granting privileges to physicians performing fluoroscopic procedures need to ensure appropriate education so they can assess individual patient risk and benefit on a case-by-case basis. These are guidelines with individual states controlling requirements. CONCLUSION: Regulation of education, training, and credentialing for physician operators of fluoroscopic equipment is currently controlled by individual states and is not uniform. There are strong indications that the FDA and or the Joint Commission will become increasingly involved to increase documentation of patient exposure and safety.

Factors affecting radiation injury.

INTRODUCTION: During the past several decades, the number of diagnostic tests and procedures that require the administration of radiation has increased dramatically. Understanding which factors affect radiation injury and how to mitigate these to protect patients has become critical for physicians to understand. Informed consent for these procedures has to include a discussion of the risks of radiation. METHODS: Factors that affect radiation injury, as well as ways to mitigate these, are discussed. Informed consent is also reviewed. RESULTS: Technical factors of the radiation delivery and patient factors both influence the dose of radiation received. Minimizing exposure is critical, and close examination of the patient is warranted to diagnose radiation injury. True informed consent includes a frank discussion of the radiation risks as well as the benefits of the procedure. CONCLUSION: Minimizing patient radiation exposure and accurately diagnosing radiation injury are key skills with which any physician ordering or performing tests or procedures requiring the use of radiation needs to be familiar. Informed consent includes a discussion of the risks as well as the benefits of the proposed radiation exposure.

Rupture of a nonaneurysmal aorta secondary to Staphylococcus aortitis.

Infectious aortitis has become increasingly uncommon and, when diagnosed, typically occurs in an immunocompromised elderly male with a history of Staphylococcus or Salmonella infection and underlying atheromatous cardiovascular disease. The authors report a case of a 74-year-old man with aortitis complicated by rupture secondary to Staphylococcus aureus infection. The patient presented with worsening abdominal pain and fever after being discharged from the emergency room 2 weeks before with back pain and leukocytosis diagnosed as urinary tract infection and bronchitis. Computed tomography (CT) imaging of the retroperitoneum on the first visit appeared normal. Repeat CT scan on the subsequent visit revealed a contained rupture of a nonaneurysmal aorta at the level of the diaphragm. The patient was taken to the operating room emergently for repair. An infected periaortic hematoma and a 1 cm perforation in the posterior aorta were found. The aorta was excised and the area debrided. Revascularization was performed using a 22 mm extruded polytetrafluoroethylene (ePTFE) interposition graft placed in situ. This case demonstrates that a high index of suspicion is required in diagnosing infectious aortitis and that the diagnosis may be delayed in many cases. Additionally, it may not be uncommon for the infected aorta to rupture without prior aneurysm formation.

A changing pattern of infection after major vascular reconstructions.

Wound and graft infection can occur in more than 40% of patients undergoing vascular reconstructions for peripheral arterial disease (PAD). A recent increase in the frequency and severity of infections, as well as a change in the microorganisms recovered, led us to undertake a retrospective case-controlled study of wound/graft infections at this institution. The medical records of all patients undergoing vascular reconstruction for PAD during the previous 36 months were reviewed. Patient demographics, graft location and conduit, infection location, causative microorganisms, and factors potentially associated with development of infection were recorded. Infections were classified according to a modification of the CDC criteria into superficial incisional, deep incisional, or involving the graft (body only, anastomosis without disruption, or anastomosis with disruption). Univariate and multivariate regression analyses were used to identify factors associated with the development of infection. Four hundred ten (84 aortic, 41 extraanatomic, and 285 infrainguinal) revascularization procedures were performed in 217 men and 193 women with a mean age of 62 years (range 43-88). The infection rate for the entire group was 11.0% (45/410). Eighty percent (36/45) occurred after infrainguinal reconstructions and 64% (29/45) of the infections involved the groin incision. Direct involvement of the graft occurred in 67% (30/45), and 27% (12/45) presented with anastomotic disruption. Of the infrainguinal infections, in situ and prosthetic reconstructions were associated with a significantly higher rate of infection than reversed vein grafts tunneled anatomically (p <0.001, chi-square analysis). Patients with nonautogenous grafts (24 expanded polytetrafluoroethylene and 2 bovine) presented with more advanced infections involving the graft (20/26 procedures) and were more likely to present with anastomotic disruption (11/26). Staphylococcus aureus was isolated in the majority of infections (64%) and in all cases involving graft disruption. Multivariate regression analysis identified the following factors associated with development of infection: previous hospitalization (p = 0.03), a younger age (p = 0.047), and the presence of a groin incision (p = 0.04). Twenty-five percent of graft infections resulted in major amputation, and 11% of patients with graft infection died as a result. The incidence, morbidity, and mortality of infections in vascular reconstructions for PAD are increasing dramatically, particularly in infrainguinal reconstructions involving groin incisions. Perioperative antibiotic selection should be modified to include coverage for all Staphylococcal subspecies and hospitalization before surgical procedures should be avoided.

Robot-assisted laparoscopic aortic reconstruction for occlusive disease-a case report.

Aortobifemoral bypass is the standard method for revascularization of aortoiliac occlusive disease but is associated with significant morbidity and mortality. Laparoscopic aortic reconstruction eliminates the large incision but is limited by the cumbersome nature of laparoscopic instrumentation. A robotic system (da Vinci Computer-Enhanced Robotic Surgical System, Intuitive Surgical, Mountain View, CA) has been developed that allows the surgeon to suture in the same manner as in open procedures. The authors report the first case of an aortic reconstruction for occlusive disease performed using the da Vinci system. A 53-year-old woman presented with gangrene of the left great toe. Angiography revealed distal aortic occlusive disease and occlusion of the common iliac arteries bilaterally. Dissection of the aorta was performed by a transabdominal-retroperitoneal approach modified from Dion (J Vasc Surg 26:128-132, 1997). With use of laparoscopic techniques, the abdominal contents were retracted to the patient's right side while the kidney and ureter remained in the retroperitoneum. The aorta was isolated from the bifurcation proximally to the left renal vein. The patient was anticoagulated, and the aorta was clamped below the left renal artery and proximal to the bifurcation. The da Vinci robotic system was placed on the patient's right side, and an extruded polytetrafluoroethylene (ePTFE) graft was passed into the retroperitoneum. While seated at a computer console viewing the operative field on a screen, the surgeon used robotic instruments to fashion an arteriotomy and complete an end-to-side aortic anastomosis using ePTFE suture. The left groin was opened and the aortic graft passed down to the groin. The reconstruction was completed by performing a left-to-right femoro-femoral bypass in standard, open fashion. The procedure was completed in 8 hours with an aortic clamp time of 65 minutes and a 500 cc blood loss. The patient was extubated in the operating room, ate a regular diet on postoperative day 2, and was discharged on postoperative day 4 without complications. Return to normal activities occurred 2.5 weeks postoperatively. The da Vinci robotic system facilitated creation of the aortic anastomosis and shortened aortic clamp time over that achieved with laparoscopic techniques. Robot-assisted laparoscopic aortofemoral bypass should decrease the morbidity and mortality of aortic reconstruction, while providing a durable solution to aortoiliac occlusive disease.

Association between physical activity and endogenous fibrinolysis in peripheral arterial disease: a cross-sectional study.

The purpose of this study was to determine whether daily physical activity was independently related to endogenous fibrinolysis in subjects with peripheral arterial disease (PAD). One hundred and six subjects with peripheral arterial disease (PAD) and intermittent claudication were characterized on the activity level of tissue plasminogen activator (tPA, the activator of fibrinolysis), the activity level of plasminogen activator inhibitor (PAI-1, the inhibitor of fibrinolysis), daily physical activity, ambulatory function, and demographic information. Subjects were separated into low (n = 36), moderate (n = 34), and high (n = 36) physical activity tertiles based on a 48-hour monitoring period with use of an accelerometer. The tPA activity of the low physical activity group (1.30 +/- 0.16 IU/mL) was 21% and 19% lower (p<0.05) than that of the moderate (1.65 +/- 0.18 IU/mL) and the high (1.61 +/- 0.15 IU/mL) physical activity groups, respectively. The PAI-1 activity of the low physical activity group (21.41 +/- 1.14 AU/mL) was 15% and 23% higher than that of the moderate (18.61 +/- 1.34 AU/mL) and the high (17.47 +/- 1.14 AU/mL) physical activity groups, respectively. Group differences in tPA activity and PAI-1 activity persisted after our controlling for group differences in measured and self-reported ambulatory measures. Daily physical activity is related to a more favorable endogenous fibrinolytic profile in PAD subjects with intermittent claudication. Subjects who expend fewer than 175 kcal/day in physical activities (approximately 35 minutes) are particularly susceptible to having a prothrombotic state. Subjects should be encouraged to participate in at least 35 minutes of physical activity each day to enhance fibrinolysis.

Comparison of bolus injection and constant infusion methods for measuring muscle protein fractional synthesis rate in humans.

BACKGROUND: The use of stable isotope tracer techniques to measure muscle protein fractional synthesis rate (FSR) has been well established and widely used. The most common method that has been utilized so far is a primed constant infusion (CI) method, which requires 3-4 h of tracer infusion. However, recently our group has developed a bolus injection (BI) method, which requires an injection of bolus of tracer and can be completed within 1 h. In this study, we compared calf (gastrocnemius) muscle protein FSR measured using these two different methods--CI and BI. METHOD: FSRs were measured in eight people (5 men and 3 women; age: 62.3±6.9 years (mean±SD); body weight: 75.4±21.5 kg) at basal, postabsorptive state using L-[ring-2H5]-phenylalanine. In the CI protocol, a primed continuous infusion was given for 4 h, and muscle biopsies were taken at 120 and 240 min; in the BI, a bolus injection of the tracer was given at 0 min and biopsies were taken at 5 and 60 min. Tracer enrichments in blood and muscle tissue were determined by gas chromatography-mass spectrometry. Data are expressed as mean±SE; t-test, linear regression and Levene Median equal variance test analyses were performed. RESULTS: CI FSR was 0.066±0.006%/h, whereas BI FSR was 0.058±0.008%/h, p=NS. The linear regression analysis showed a significant relationship between BI and CI, p=0.038. The intra-class correlation coefficient was 0.83. The standard deviation of the differences in the measurements was 0.015%/h. The Levene Median equal variance test demonstrated no difference in variance between the CI and BI measurements (p=0.722). CONCLUSION: No difference could be detected in calf muscle protein FSR measured by CI and BI methods; the BI method can be used for the measurement of muscle protein FSR in humans.

Analysis of venous thromboembolic events after saphenous ablation.

BACKGROUND: Venous thromboembolic events after saphenous vein ablation procedures for varicose veins have been reported. Current knowledge of these events is based on single-institution studies or studies with small numbers of patients. METHODS: The National Surgical Quality Improvement Program (NSQIP) database (2005-2009) was used to identify 3874 patients who underwent radiofrequency ablation (RFA) or endovenous laser ablation (EVLA) of the saphenous veins with or without stab phlebectomy. Outcome variables included documented postoperative deep vein thrombosis (DVT) or pulmonary embolism (PE). Bivariate and multivariate logistic regression analyses were performed to identify factors associated with venous thromboembolic events after ablation procedures. RESULTS: Procedures for lower extremity varicose veins included RFA in 2897 patients (74.8%) and EVLA in 977 (25.2%). Patients who underwent RFA were more likely to be older, obese, diabetic, hypertensive, and to have undergone procedures involving more than one vein (24% vs 4%; P < .0001). Patients who underwent EVLA were more likely to have received general anesthesia (56.9% vs 40.8%; P < .0001) and to have undergone concomitant stab phlebectomy (44.9% vs 31.7%; P < .0001). The incidences of DVT (1.74% vs 1.52%; P = .63) and pulmonary embolus (0.07% vs 0%; P >.99) were similar between EVLA and RFA. No significant predictors of DVT in the postoperative period were identified on bivariate or multivariate analyses. In the subgroup of 2514 patients who underwent ablation procedures without stab phlebectomy, those undergoing EVLA showed a trend toward a higher incidence of DVT (2.6% vs 1.4%; P = .057). After adjusting for patient demographics, DVT was 2.4 times more likely to develop in patients presenting with lower extremity ulcers than in those without ulcers (odds ratio, 2.4; 95% confidence interval, 1.01-6.11; P = .04). Although not statistically significant, the multivariate model found that when only ablation procedures were performed, EVLA was associated with an 83% increase in odds of DVT compared with RFA (odds ratio, 1.83; 95% confidence interval, 0.95-3.52; P = .06). CONCLUSIONS: The incidence of venous thromboembolic events after saphenous ablation is low. However, given that patients with lower extremity ulcers experienced an increased risk of DVT, care should be taken to ensure that the ablation catheter is positioned an appropriate distance from the saphenofemoral or sapheno-popliteal junction and that periprocedural preventative measures, such as anticoagulation prophylaxis, early ambulation, and lower extremity compression, are emphasized. The finding of a trend toward increased venous thromboembolic events in patients undergoing EVLA warrants further investigation in a large patient population.

Amino acids stimulate leg muscle protein synthesis in peripheral arterial disease.

OBJECTIVE: Older patients with peripheral arterial disease (PAD) and intermittent claudication have impaired walking ability resulting from reduced lower extremity blood flow. Evidence suggests that leg muscle abnormalities may also contribute to walking intolerance in claudicants. In healthy elderly people, leg muscle protein synthesis can be augmented by nutritional supplementation with amino acids; preliminary data suggest that this increases muscle mass, walking ability, and functional status. In this study, we investigated whether amino acid supplementation would improve leg muscle protein synthesis in elderly PAD subjects, given that reduced leg blood flow might restrict the availability of amino acids to muscle. METHODS: Two groups participated in the study: a group of 11 claudicants (mean age, 62 years; mean ankle-brachial index, 0.62; 46% male) and a group of 9 age- and sex-matched healthy controls (mean ankle-brachial index, 1.1). Both groups underwent measurement of leg blood flow by using strain gauge plethysmography, as well as measurement of baseline and amino acid-stimulated protein synthesis in leg muscle. Protein synthesis was quantified from calf muscle biopsy samples by measurement of the fractional synthetic rate (FSR) of protein, by using the incorporation of the stable isotope l-[ring-(2)H(5)]-phenylalanine into muscle protein. Total protein was extracted from muscle samples, and gas chromatography/mass spectroscopy methodology was used to measure incorporation rates. After measurement of basal FSR, all subjects were given an oral drink of 15 g of essential amino acids, and the measurements of FSR were repeated. Data are expressed as mean +/- SD; statistical analysis of differences between the two groups (with and without amino acid supplementation) was performed by using analysis of variance with repeated measures. RESULTS: Calf blood flow was reduced in the PAD subjects compared with controls (1.44 +/- 0.53 mL/min per 100 mg of tissue vs 2.40 +/- 0.57 mL/min per 100 mg of tissue; P = .005; t test). FSR in the basal state was equivalent between the two groups (healthy, 0.060% +/- 0.025% per hour; PAD, 0.061% +/- 0.029% per hour; P = .97). Equivalent increases (P < .05) occurred in both groups in response to oral amino acid supplementation (healthy, 0.087% +/- 0.012% per hour; PAD, 0.104% +/- 0.041% per hour; P > .05; analysis of variance). CONCLUSIONS: Despite reduced leg blood flow, elderly PAD patients synthesize calf muscle protein in the basal state in a fashion similar to that in healthy elderly people. More importantly, administration of exogenous amino acids produces a significant increase in protein synthesis in these patients that is also equivalent to that in healthy elderly people. Our goal is to use these results as the basis for an intervention study to determine whether long-term oral amino acids, by augmenting calf muscle protein synthesis, increase calf muscle mass, walking ability, and functional status in elderly claudicants.

Natural history of physical function in older men with intermittent claudication.

PURPOSE: This study was undertaken to determine the natural history of physical function in older men limited by intermittent claudication. METHODS: Forty-three men limited by intermittent claudication (mean age, 69 +/- 7 years) were recruited and followed up for 18 months. At baseline the patients reported a history of intermittent claudication for 6.1 +/- 6.1 years, and were able to walk for 1.9 +/- 1.6 blocks before experiencing claudication pain. Measurements during the 18-month study included ankle-brachial index (ABI), calf blood flow, 6-minute walk performance, monitored and self-reported physical activity, self-reported stability while walking, and summary performance score of physical function determined from a 4-m walk test, a chair stand test, and a tandem stand test. RESULTS: Pain-free walking distance during the 6-minute walk test decreased by 22% (P <.05) from baseline (185 +/- 96 m) to follow-up (144 +/- 93 m), and the total 6-minute walk distance decreased by 9% (P <.05), from 368 +/- 106 m to 334 +/- 90 m. Furthermore, monitored physical activity decreased by 31% (P <.05), from 159 +/- 151 kcal/d to 110 +/- 137 kcal/d; self-reported physical activity declined by 27% (P <.05), from 1.5 +/- 1.0 units to 1.1 +/- 0.8 units; tandem stance time declined by 14% (P <.05), from 9.46 +/- 1.83 seconds to 8.12 +/- 2.10 seconds; summary performance score of physical function decreased by 12% (P <.05), from 6.8 +/- 2.4 units to 6.0 +/- 2.4 units; and the percentage of patients reporting ambulatory unsteadiness and stumbling increased from 28% to 43% (P <.05). Calf blood flow measured at rest declined by 18% (P <.05), from 3.72 +/- 1.81 (mL/100 mL(-1)/min(-1)) to 3.04 +/- 1.43 mL/100 mL(-1)/min(-1), whereas ABI did not change (P >.05). CONCLUSION: Older men limited by intermittent claudication experienced decline in ambulatory function, physical activity, physical function, stability, and calf blood flow over 18 months of follow-up, despite no change in ABI.

Response to exercise rehabilitation in smoking and nonsmoking patients with intermittent claudication.

BACKGROUND: The purpose was to compare the changes in claudication pain, ambulatory function, daily physical activity, peripheral circulation, and health-related quality of life following a program of exercise rehabilitation in smoking and nonsmoking patients with peripheral arterial disease (PAD) limited by intermittent claudication. Methods and results Thirty-nine smokers (63 +/- 4 pack-year smoking history; mean +/- SE) and 46 nonsmokers (former smokers who had a 51 +/- 7 pack-year smoking history who quit 14 +/- 2 years prior to investigation) completed the study. The 6-month exercise rehabilitation program consisted of intermittent treadmill walking to near maximal claudication pain 3 days per week, with progressive increases in walking duration and intensity during the program. Measurements were obtained on each patient before and after rehabilitation. Following exercise rehabilitation the smokers and nonsmokers had similar improvements in these measures, as initial claudication distance increased by 119% in the smokers (P <.001) and by 97% in the nonsmokers (P <.001), and absolute claudication distance increased by 82% (P <.001) and 59% (P <.001) in the smokers and nonsmokers, respectively. Furthermore, exercise rehabilitation improved (P <.05) ambulatory function, daily physical activity, peripheral circulation, and health-related quality of life in the smokers and nonsmokers. CONCLUSION: Exercise rehabilitation is an effective therapy to improve functional independence in both smoking and nonsmoking patients with PAD limited by intermittent claudication. Therefore, smokers with intermittent claudication are prime candidates for exercise rehabilitation because their relatively low baseline physical function does not impair their ability to regain lost functional independence to levels similar to nonsmoking patients with PAD.

Exercise training enhances endogenous fibrinolysis in peripheral arterial disease.

PURPOSE: Acute clinical events resulting from atherosclerosis (myocardial infarction, stroke) are associated with impaired endogenous fibrinolysis, the system by which the body lyses inappropriately formed thrombus. Endurance exercise training improves fibrinolysis in normal subjects and those with coronary artery disease. The hypothesis of this study was that exercise training would improve fibrinolysis in subjects with peripheral arterial disease (PAD). METHODS AND RESULTS: Twenty-one men with intermittent claudication (IC-EX) underwent treadmill exercise training for 6 months. Twenty age-matched male subjects with IC were followed for the same period (IC-NONEX). Fibrinolytic activity was measured prior to entry into exercise or "usual care," and at the completion of the study period. Fibrinolysis was quantified by measurement of the activity levels of tissue plasminogen activator (tPA, the activator of fibrinolysis) and its inhibitor plasminogen activator inhibitor-1 (PAI-1), using an amidolytic method. Fibrinolysis, quantified as increased PAI-1 activity, was reduced in both claudicant groups relative to healthy controls at baseline. After 6 months of exercise, subjects in the IC-EX group experienced significant improvements in fibrinolytic activity, manifested as a 23% decrease in PAI-1 activity and a 28% increase in tPA activity. No changes occurred in the IC-NONEX group. In the IC-EX group, subjects with the highest initial PAI-1 values experienced the greatest decreases in PAI-1 activity and thus the greatest benefit from exercise. CONCLUSIONS: Patients with PAD have impaired fibrinolytic activity, manifested primarily as increases in the inhibitor of fibrinolysis, PAI-1. Six months of exercise training reduced these impairments, and may serve as an intervention to reduce cardiovascular mortality and morbidity in these patients.

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.

Morphologic characteristics of varicose veins: possible role of metalloproteinases.

BACKGROUND: Although varicose veins are a common cause of morbidity, etiologic factors predisposing to dilatation, elongation, and tortuosity of the saphenous vein and its tributaries are poorly understood. We compared histologic features of normal and varicose saphenous veins and investigated the role of enzyme or inhibitor imbalance in development of varicosities. METHODS: Eight normal and 10 varicose (C(2,3)E(P,S)A(S)P(R,O)) vein segments were used for this analysis. Matrix metalloproteinase (MMP) expression and activity were analyzed with Western blotting and zymography. Venous architecture and protein localization were determined with histology and immunohistochemistry. RESULTS: Western blot analysis demonstrated the presence of MMP- 1, MMP-2, MMP-9, and MMP-12, as well as small quantities of tissue inhibitor of metalloproteinases (TIMP)-1 and TIMP-2 in protein isolates from normal and varicose veins. Both vein types demonstrated MMP-2, MMP-9, and MMP-12 activity by gelatin zymography, although varicose vein expressed less MMP-9 activity than normal vein did. Compared with normal veins, changes in varicose veins were not uniformly distributed along the circumference; areas of intimal thickening were often interspersed with focal areas of dilatation. Fragmentation of elastic lamellae and loss of circular and longitudinal muscle fibers were evident in the varicosities. Focal aggregates of macrophages were detected within the media and adventitia of both normal and varicose veins. MMP-1 and MMP-9 were expressed in both types of vein segments; however, their immunohistochemical localization was distinctly different. In normal vein, endothelial cells, occasional smooth muscle cells (SMC), and adventitial microvessels expressed MMP-1, whereas its expression was localized to fibroblasts, SMC, and endothelial cells throughout involved portions of varicose veins. MMP-9 was localized to endothelial cells, medial SMC, and adventitial microvessels in both normal and varicose veins, although varicose veins demonstrated increased medial smooth muscle cell staining. MMP-12 was found in SMC and fibroblasts in both normal and varicose veins. Neither TIMP-1 nor TIMP-2 were detected with immunohistochemistry in any specimens examined. CONCLUSIONS: There are distinct differences in the structural architecture and localization of MMP expression in normal and varicose veins. Although the changes observed are not sufficiently definitive to enable a causal relationship, they do suggest a possible mechanism for the alterations in matrix composition observed between normal and varicose veins.

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.

Deep venous thrombosis prophylaxis in trauma: improved compliance with a novel miniaturized pneumatic compression device.

OBJECTIVE: Intermittent pneumatic compression (IPC) devices prevent lower-extremity deep venous thrombosis (LEDVT) when used properly, but compliance remains an issue. Devices are frequently discontinued when patients are out of bed, and they are rarely used in emergency departments. Trauma patients are at high risk for LEDVT; however, IPCs are underused in this population because of compliance limitations. The hypothesis of this study was that a new miniaturized, portable, battery-powered pneumatic compression device improves compliance in trauma patients over that provided by a standard device. METHODS: This was a prospective trial in which trauma patients (mean age, 46 years; revised trauma score, 11.7) were randomized to DVT prophylaxis with a standard calf-length sequential IPC device (SCD group) or a miniaturized sequential device (continuous enhanced-circulation therapy [CECT] group). The CECT device can be battery-operated for up to 6 hours and worn during ambulation. Timers attached to the devices, which recorded the time each device was applied to the legs and functioning, were used to quantify compliance. For each subject in each location during hospitalization, compliance rates were determined by dividing the number of minutes the device was functioning by the total minutes in that location. Compliance rates for all subjects were averaged in each location: emergency department, operating room, intensive care unit, and nursing ward. RESULTS: Total compliance rate in the CECT group was significantly higher than in the SCD group (77.7% vs. 58.9%, P =.004). Compliance in the emergency department and nursing ward were also significantly greater with the CECT device (P =.002 and P =.008 respectively). CONCLUSIONS: Previous studies have demonstrated that reduced compliance with IPC devices results in a higher incidence of LEDVT. Given its ability to improve compliance, the CECT may provide superior DVT prevention compared with that provided by standard devices.