Enoxaparin treatment in high-risk trauma patients limits the utility of surveillance venous duplex scanning.

OBJECTIVE: The value of surveillance venous duplex scanning for detecting unsuspected deep venous thrombosis (DVT) in trauma patients who are receiving enoxaparin prophylaxis is open to question. This study was undertaken to determine whether enoxaparin reduced the clinical utility of surveillance scanning and whether management of these patients was altered by findings of the scans. METHODS: The medical records of trauma patients who met defined criteria for high DVT risk, admitted during 30 consecutive months, were reviewed. These patients received enoxaparin 30 mg every 12 hours for the duration of their admissions. Per protocol, surveillance lower extremity venous duplex scans were performed within 72 hours of enoxaparin administration and then weekly until patients were discharged from the hospital. The records were reviewed for thromboembolic events (DVT or pulmonary embolism [PE]), patient location and ambulatory status, therapeutic interventions (systemic anticoagulation, vena cava filter), and complications of enoxaparin therapy. RESULTS: A total 241 patients underwent 513 venous duplex examinations (1-13 per patient). Eight patients had DVT on the initial scan; seven of these patients were asymptomatic. Five were treated with anticoagulation and/or vena cava filter placement. Of the 233 patients with initially negative duplex scan results, five patients (2%) developed clinically unsuspected lower extremity DVT while hospitalized. All of these five patients were in an intensive care unit. Three of the five patients had no change in treatment. Two of the five underwent anticoagulation, and one vena cava filter was placed. PE occurred in two hospitalized patients, one of whom was ambulatory, with negative duplex scan results. After hospital discharge, six other patients had symptomatic DVT or PE despite in-hospital scans with negative results. Complications associated with enoxaparin included hemorrhage (2) and thrombocytopenia (8). CONCLUSIONS: After initial negative scan results, repeat surveillance duplex scanning during hospitalization detected a low incidence (2%) of DVT in high-risk patients. Furthermore, the detection of unsuspected DVT altered the clinical management of less than 1% of the patients tested. Thus, after a venous duplex scan with negative results and initiation of enoxaparin prophylaxis, subsequent surveillance duplex examinations are not warranted in asymptomatic trauma patients.

Surgical management of thrombotic acute intestinal ischemia.

OBJECTIVE: To evaluate the University of Kentucky experience in treating acute intestinal ischemia to elucidate factors that contribute to survival. SUMMARY BACKGROUND DATA: Acute intestinal ischemia is reported to have a poor prognosis, with survival rates ranging from 0% to 40%. This is based on several reports, most of which were published more than a decade ago. Remarkably, there is a paucity of recent studies that report on current outcome for acute mesenteric ischemia. METHODS: A comparative retrospective analysis was performed on patients who were diagnosed with acute intestinal ischemia between May 1993 and July 2000. Patients were divided into two cohorts: nonthrombotic and thrombotic causes. The latter cohort was subdivided into three etiologic subsets: arterial embolism, arterial thrombosis, and venous thrombosis. Patient demographics, clinical characteristics, risk factors, surgical procedures, and survival were analyzed. Survival was compared with a collated historical series. RESULTS: Acute intestinal ischemia was diagnosed in 170 patients. The etiologies were nonthrombotic (102/170, 60%), thrombotic (58/170, 34%), or indeterminate (10/170, 6%). In the thrombotic cohort, arterial embolism accounted for 38% (22/58) of the cases, arterial thrombosis for 36% (21/58), and venous thrombosis for 26% (15/58). Patients with venous thrombosis were younger. Venous thrombosis was observed more often in men; arterial thrombosis was more frequent in women. The survival rate was 87% in the venous thrombosis group versus 41% and 38% for arterial embolism and thrombosis, respectively. Compared with the collated historical series, the survival rate was 52% versus 25%. CONCLUSIONS: These results indicate that the prognosis for patients with acute intestinal ischemia is substantially better than previously reported.

Telemedicine in vascular surgery: does it work?

Telemedicine (TM) using closed-circuit television systems allows specialists to evaluate patients at remote sites. Because an integral part of the vascular examination involves palpation of peripheral pulses the applicability of TM for the evaluation of vascular surgery patients is open to question. This study was carried out to test the hypothesis that TM is as effective as direct patient examination for the development of a care plan in vascular patients. Sixty-four vascular evaluations were done in 32 patients. The patients presented with a variety of vascular problems and were seen in regularly scheduled rural outreach vascular clinics. Two faculty vascular surgeons evaluated each patient; one was on site and the second, using TM, remained at the medical center. Each surgeon was blinded to the other's findings. The TM physician was aided by a nonphysician assistant, who obtained blood pressures, utilized a continuous-wave Doppler probe, positioned the patient, and operated the TM equipment. The results of each surgeon's evaluations were compared. Patient and physician satisfaction with the TM evaluation was appraised by questionnaires. Eight patients were seen for initial evaluations; 24 patients were seen for follow-up visits. Patients were seen with a variety of diagnoses, including aneurysm (seven), cerebrovascular disease (five), lower extremity occlusive disease (13), multiple vascular problems (three), and other disease (four). The average duration for the TM and on-site evaluations were 20.6+/-1.4 and 19.0+/-1.3 minutes, respectively (P = not significant). Physician concordance, as determined by treatment recommendations, was the same in 29 (91%) patients. Physician confidence in the ability to obtain an accurate history via TM was rated as excellent in 97 per cent; confidence in the TM physical examination was rated as excellent in 70 per cent. All patients rated the TM evaluation as the "same as" or "better than" the on-site examination, and all indicated a preference for being seen locally using TM as opposed to traveling to a regional medical center. We conclude that the TM evaluation of vascular patients is accurate and is as effective as on-site evaluations for a variety of vascular problems. Important adjuncts to enhance the success of a TM evaluation are physician experience with the technology and the presence of a knowledgeable on-site assistant. This technology can be easily adapted to other clinical situations.

The response of adult human saphenous vein endothelial cells to combined pressurized pulsatile flow and cyclic strain, in vitro.

Adult human saphenous vein endothelial cells (HVEC) were cultured in a compliant tubular device and evaluated by Northern hybridization for the effects of combined pressurized pulsatile flow and cyclic strain on the expression of mRNAs for endothelin-1 (ET-1), endothelial cell nitric oxide synthase (ecNOS), tissue plasminogen activator (tPA), and plasminogen activator inhibitor type 1 (PAI-1). The hemodynamic environment was designed to mimic shear stress conditions at the distal anastomosis of a saphenous vein graft, a common site of intimal proliferation. Steady-state mRNA levels in experimental tubes were expressed relative to that in controls. No changes were observed in ET-1 mRNA after 1 and 24 hr, but a 50% decrease in experimental cultures was observed after 48 hr in the vascular simulating device. Similar results were obtained for ecNOS mRNA, although a subgroup (4 of 11) showed a significant decrease (>50%) by 24 hr. For tPA mRNA, no change was observed after 1 hr, but a significant decrease (>60%) was measured after 24 hr and no message was detectable after 48 hr. Steady-state levels for PAI-1 mRNA remained unchanged through 48 hr of treatment. These results show that pressure, pulsatile flow, and cyclic strain, when applied in concert, differentially alter vasoactive and fibrinolytic functions in HVEC. Moreover, the dramatic decrease in steady-state levels of tPA mRNA is consistent with a shift toward an increased thrombotic state.

Popliteal artery thrombosis associated with trampoline injuries and anterior knee dislocations in children.

Recent reports have emphasized the benign nature of trampoline-associated injuries. However, this study describes the limb-threatening problem of popliteal artery thrombosis occurring in association with anterior knee dislocation and trampoline injuries. Three children (ages 11, 13, and 17) were referred to the emergency room within the past 12 months with anterior dislocations of the knee, which occurred while jumping on trampolines. All patients had reduction of their dislocations at outside facilities and were referred within 6 to 12 hours after their injuries, with pulse, motor, and sensory deficits. All patients were taken directly to the operating room, where arteriography confirmed thrombosis of the popliteal artery below the knee. One patient had transection of the artery, whereas two patients had stretch injuries with intimal separation. Each patient required interposition grafting with reversed saphenous vein and underwent concomitant four-compartment fasciotomy. All patients had persistent sensory and motor deficits postoperatively, which were presumed to be a combination of ischemic injury and neuropraxia. All patients have functioning grafts with an average follow-up of 1 year (range, 9-15 months). One patient required a second interposition graft to treat an area of intimal hyperplasia, which developed at the proximal anastomosis, at 6 months postoperatively. Eighty per cent of trampoline injuries are associated with minor injuries with minimal long-term complications. However, dislocations of the knee may be associated with significant arterial injury and amputation rates of up to 30 per cent in many blunt trauma series. Based on our experience, physicians should recognize the possibility of significant arterial injuries occurring in children with anterior knee dislocations while jumping on trampolines.

Process improvements reduce utilization of resources for aortic aneurysm repair.

In conjunction with the VA reorganization to promote greater efficiency of health care provision, ambulatory surgery (AS) programs have been created. These programs institute outpatient preoperative assessment and operative management. This study examines the impact of these process changes on resources utilized by patients requiring repair of abdominal aortic aneurysms (AAAs). The medical records of 15 consecutively treated patients undergoing elective, infrarenal AAA repair before (1992-1993) and after (1995-1996) AS implementation were reviewed. Resource utilization was assessed by evaluating preoperative tests performed (inpatient or outpatient), ICU days, and inpatient length of stay (LOS). Postoperative morbidity and mortality were noted. Patient age, AAA size, and prevalence of diabetes mellitus, hypertension, cardiac disease, COPD, and tobacco use were similar between the two groups. Abdominal ultrasound, CT scanning, and angiography were significantly more frequently performed on an outpatient basis after implementation of the AS program. The median preoperative LOS was reduced in the AS group (1 vs 6 days, P = 0.001, Student t test), resulting in a lower inpatient LOS (11 vs 16, P < 0.01, Student t test). All patients survived and the incidence of complications was similar between the groups. Hospital resource utilization was significantly decreased, largely by shifting preoperative assessment to the outpatient setting. This study illustrates that benefits of an ambulatory surgery program can be extended beyond facilitating outpatient operations and should result in decreased length of hospitalization for other major surgical procedures, such as abdominal aortic aneurysm repair.

Ward evaluations: should they be abandoned?

Even in the era of the objective structured clinical examination (OSCE), the predominant method of resident evaluation is the faculty ward evaluation (WE), despite many concerns about its reliability. The aim of this study was to determine the value of the WE as a measurement of clinical competence in terms of both reliability and validity. In a one-year period, surgery faculty members evaluated 72 residents. An average of 7 faculty members evaluated each resident. The evaluation form contained 10 specific performance ratings and an overall evaluation. Inter-rater reliability of the overall performance ratings was calculated by using the intraclass correlation. Validity of the WE was evaluated in four ways. Inter-rater reliability of the overall performance rating was 0.82; the reliability of a single overall rating was 0.39. (1) A discriminant function analysis indicated that residents at advanced levels of training received more positive evaluations than residents at less advanced levels (P < 0.0001). (2) The overall rating was significantly correlated (r = 0.55, P < 0.0001) with the overall score of a concurrent OSCE. (3) A factor analysis showed high correlations among the items, indicating a lack of discrimination between the skills. (4) Overall ratings were insensitive to performance deficiencies. Only 1.3% of the ratings were unsatisfactory or marginal. The WE was sufficiently reliable to estimate the faculty's view of each resident. The fact that the ratings tended to differentiate residents by level of training and that ratings significantly correlated with the OSCE provides strong evidence of their validity. However, factor analysis indicated that the faculty members were making one global, undifferentiated judgment and that these ratings did not identify deficient performance skills. We conclude that ward evaluations have a place in the assessment of residents.

Characteristics of vascular wall cells subjected to dynamic cyclic strain and fluid shear conditions in vitro.

We recently developed an in vitro silicone rubber tubular apparatus, the vascular simulating device (VSD), which simulates pressure, flow, and strain characteristics of peripheral arteries (Benbrahim et al., 1994, J. Vasc. Surg. 20, 184-194). In this report, we tested the ability of silicone rubber surfaces to support the growth and differentiation of endothelial cells (EC) and smooth muscle cells (SMC) and studied the effects of arterial levels of pressure, flow, and strain on these properties. Human umbilical and saphenous vein EC and bovine aortic EC and SMC were cultured on coated and uncoated silicone rubber in flat and tubular configurations (6 mm inner diameter) and on tissue culture plastic (TCP). Attachment, growth, and differentiation were compared on these surfaces. In addition, the effects of arterial pressure, flow, and strain conditions on adhesion and subsequent growth and differentiation were studied in the tubular configuration. Attachment and growth of vascular wall cells on fibronectin-coated silicone rubber was similar to that obtained on TCP. Application of arterial levels of pressure, flow, and strain did not alter adhesion of the cells to the tubes. Subsequent passage of these cells demonstrated that attachment, growth, and differentiation (uptake of LDL and expression of factor VIII-related antigen by EC and expression of muscle-specific actin by SMC) were similar in cells derived from experimental and control tubes which were not subjected to arterial conditions. Finally, mRNA expression of specific "housekeeping" genes was similar in cells isolated from experimental and control tubes. We conclude that the VSD supports the culture of viable and differentiated EC and SMC. These experiments demonstrate that it is possible to evaluate the effects of arterial strain and fluid shear on vascular wall cells in vitro, in a configuration similar to the blood vessel wall.

Aortoscopy: a guidance system for endoluminal aortic surgery.

PURPOSE: The aim of this project was to evaluate the feasibility of aortoscopy for guidance of endoluminal aortic procedures and to determine whether aortoscopy has advantages over fluoroscopy in a pig model. METHODS: To establish feasibility aortoscopic guidance was used for making endoluminal aortic measurements, cannulating small arteries for arteriograpy, and placing intraaortic stents and grafts in 11 pigs. To compare aortoscopy and fluoroscopy measurements were made and stents were placed by a surgeon using only aortoscopic guidance in 10 pigs and by an interventional radiologist using only fluoroscopic guidance in 10 pigs. Postmortem dissections were performed to determine measurement and device placement accuracy. RESULTS: In the feasibility study aortoscopic measurements differed from postmortem measurements by a mean distance (+/- SD) of 1.2 +/- 0.2 mm. Stents and grafts were placed a mean of 2.3 +/- 1.9 mm distal to the most inferior renal artery with no stent covering an orifice. All attempts at cannulating spinal arteries greater than 2 mm in diameter were successful. In the comparison of aortoscopic and fluoroscopic guidance, fluoroscopic measurements differed from postmortem measurements by 2.6 +/- 2.4 mm (p = 0.223). Stents placed with aortoscopic guidance were 1.1 +/- 1.3 mm distal to the most inferior renal artery, whereas stents placed with fluoroscopic guidance were 3.4 +/- 2.5 mm distal to the most inferior renal artery (p = 0.019). CONCLUSIONS: These results demonstrate that aortoscopy is a useful guidance system for endoluminal aortic procedures and may have advantages over fluoroscopy alone.

Comparison of angioscopy and angiography for monitoring infrainguinal bypass vein grafts: results of a prospective randomized trial.

PURPOSE: This study was designed to determine whether, in primary infrainguinal bypass grafts in which only saphenous vein is used as the graft conduit, routine monitoring with intraoperative angioscopy can improve early graft patency as compared with standard monitoring with intraoperative completion angiography; and to delineate the advantages and disadvantages of these two modalities and their respective roles for the routine monitoring of the infrainguinal bypass graft. METHODS: A total of 293 patients undergoing primary saphenous vein infrainguinal bypass grafting were prospectively randomized and monitored with either completion angioscopy or completion angiography. Clinical parameters, indications for operation, graft anatomy, and configuration were evenly matched in both groups. Forty-three bypasses were excluded from the study after randomization, including 12 veins randomized to angiogram, deemed inferior, and prepared with angioscopy. RESULTS: In the 250 bypass grafts (angioscopy 128, angiography 122) there were 39 interventions (conduit, 29; anastomosis, 8; distal artery, 2), 32 with angioscopy and 7 with angiography (p < 0.0001). Twelve (4.8%) of the 250 grafts failed in less than 30 days, four (3.1%) of 128 in the angioscopy group and eight (6.6%) of 122 in the angiography group (p = 0.11 by one-sided hypothesis test). CONCLUSION: Although no statistical improvement in the proportions of failures in primary saphenous vein bypass grafts routinely monitored with completion angioscopy rather than the standard completion angiogram was demonstrated, the study delineates a trend that favors completion angioscopy for routine vein graft monitoring and demonstrates the advantages of angioscopy in preparing the optimal vein conduit.

Peripheral vascular bypass in juvenile-onset diabetes mellitus: are aggressive revascularization attempts justified?

This study was performed to evaluate the results of peripheral vascular reconstruction for arterial occlusive disease in patients with juvenile-onset diabetes mellitus. The results of 67 bypass procedures performed on 60 patients with juvenile-onset diabetes mellitus between Jan. 1, 1984 and Dec. 31, 1989, were reviewed. These patients had a mean age of 44.4 years (range, 29 to 59 years), with an average age of onset of diabetes mellitus of 9.8 years (range, 1 to 19 years). These procedures comprised 5.5% (67 to 1214) of the bypasses performed on diabetic patients during the same time period at a single institution. Fifty-four of 67 (91%) procedures were performed for limb salvage. Fifty-four (81%) procedures were primary infrainguinal bypasses with saphenous vein (femoropopliteal 19, femorodistal or popliteal-distal 35). Six procedures (9%) were revision procedures, four (6%) were in-flow procedures, and three (4%) were infrainguinal procedures with polytetrafluoroethylene. Thirty-day morbidity and mortality rates were 31% and 0%, respectively. Actuarial patency and limb salvage rates of the primary vein graft group were 66.0% (+/- 10.7) and 83.4% (+/- 8.0%), respectively, at 24 months. Cumulative survival of the entire group at 2 years was 84.1%. Although follow-up in this study is relatively short (24 months), the results suggest that the outcome of vascular reconstruction in patients with juvenile-onset diabetes mellitus is acceptable when compared with procedures performed in adult-onset diabetic and nondiabetic populations. The presence of juvenile-onset diabetes mellitus should not diminish the vascular surgeon's expectations of a successful outcome when considering lower extremity revascularization in these patients.

Safety of saline irrigation for angioscopy: results of a prospective randomized trial.

This study evaluates the hemodynamic effects and safety of saline irrigation necessary to obtain high-quality completion angioscopic studies, as compared with standard completion arteriography during infrainguinal bypass grafting. One-hundred ten patients undergoing primary infrainguinal bypass grafting, were prospectively randomized to either arteriography (N = 50) or angioscopy (N = 60) for a completion study to monitor the bypass procedure. All patients were hemodynamically monitored with pulmonary artery catheters and arterial lines. The arteriography group received an average of 27 ml (range 8-60 ml) of contrast per completion study, with a total administered intraoperative fluid volume of 2095 ml (range 650-4000 ml). The angioscopy group received an average bolus of 321 ml (range 90-650 ml) of irrigation fluid per completion angioscopy study, with a total administered intraoperative fluid volume of 2140 ml (range 850-5000 ml). Transient increases in pulmonary artery systolic and diastolic pressures and central venous pressures were measured during angioscopy. Although these changes reached statistical significance, the changes were of minimal clinical relevance, 1.9 (= 4.5), 1.6 (= 3.0) and 1.4 (= 2.3) mmHg respectively, and returned to baseline levels within 30 minutes. Intraoperative intervention with vasodilators and diuretics, the perioperative cardiac morbidity, and less than 30 day mortality, was not different between the two groups. Pressures generated within 24 bypass grafts were within physiologic arterial range for most of the study. With careful angioscopic technique applied and high quality care extended to the patient, irrigation with saline solution is simple, effective and safe.

Angioscopically directed valvulotomy: a new valvulotome and technique.

Despite a large experience with "blind" retrograde valvulotomy in in situ vein bypass grafting, the incidence of residual competent valves remains high, and valvulotome-induced injury is common. In this study we describe a new valvulotome and technique of angioscopically directed valvulotomy and review the video tape recordings of 85 completion angioscopies of in situ femorodistal bypasses. Fifty-three vein grafts were prepared with the blind retrograde valvulotomy technique and 32 vein grafts with the new valvulotome and angioscopy. The use of the new valvulotome and technique is compared with that of the standard blind retrograde valvulotomy technique, and the normal endoluminal anatomy and incidence of primary disease in saphenous vein grafts was noted. The incidence of valvulotome-induced injury was 5/32 (15.6%) and 45/53 (85%) in vein grafts prepared with angioscopically directed valvulotomy and blind retrograde valvulotomy, respectively. Residual competent valves were found in 10/53 (18.9%) in blind retrograde valvulotomy and 0/25 of angioscopically directed valvulotomy vein grafts (p = 0.0114). In 22/53 vein grafts unsuspected primary disease was detected. Angioscopically directed valvulotomy with the new valvulotome and technique is feasible, reliable, and safe. It avoids residual competent valves, minimizes valvulotome-induced injury, and allows the detection and correction of unappreciated primary vein graft abnormalities. The new valvulotome and technique is a first step in the complete endoluminal preparation of the in situ vein graft.

Nucleotide sequence of the influenza virus A/USSR/90/77 neuraminidase gene.

The complete nucleotide sequence of the N1 neuraminidase gene of influenza virus A/USSR/90/77 was determined. Comparison of its predicted amino acid sequence with other N1 and N2 neuraminidases indicates that the N1 neuraminidases share most of the antigenic determinants mapped on the N2 neuraminidase but display at least one additional potentially antigenic region probably as a result of intersubtypic differences in glycosylation.