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Biomedical subjects

W E Lloyd

Publications and source records attributed to W E Lloyd.

At least 37 records · Page 2Linked to original sources
PubMed1997

A critical approach for longitudinal clinical trial of stretch PTFE aortic grafts.

Adaptation of new clinical products should be based upon thorough scientific evaluation of properties and performance in vitro and in vivo. Developmental animal research experimentation is classically carried out by the manufacturer with eventual government approval. However, objective data needs to be recorded during clinical trials including handling characteristics, bleeding, tensile strength, kinking, seamline break, dilatation, anastomotic deterioration, patency, and incorporation. Since April 1991, 1010 stretch polytetrafluoroethylene (PTFE) aortic grafts have been implanted at our institution and data were recorded prospectively. Six hundred and seven were for elective abdominal aortic aneurysms, 46 for symptomatic abdominal aortic aneurysms, 58 for ruptured abdominal aortic aneurysms, 17 for elective thoracoabdominal aneurysms, 3 for ruptured thoracoabdominal aneurysms and the remainder were for various aortoiliac pathology. Average age of the patients was 69 (range: 10-95), 66% were males, 25% were diabetics. Overall operative mortality was 5.8% (2.9% in elective cases and 26.6% in emergent cases). There were 23 occlusions; 21 were revised and 2 were replaced with axillofemoral bypasses. Estimated blood loss was 784 cc in elective cases and 1918 cc in emergent cases. Grafts were followed by duplex ultrasound or CT scan every 3 months during the first year and every 6 months thereafter. There were no graft dilatations or false aneurysms in this series. There was one graft infection and no perigraft seromas or anastomotic deteriorations during this follow up. Follow up was complete in 94% of these patients. In conclusion, stretch PTFE graft has acceptable handling characteristics, no excessive bleeding at the suture line and had no anastomotic or graft dilatation. This graft material was suitable for thoracic, visceral, renal and abdominal aortic reconstructions.

Adolescent↗
PubMed1996

Fate of the excluded abdominal aortic aneurysm sac: long-term follow-up of 831 patients.

PURPOSE: Nonresective treatment of the infrarenal abdominal aortic aneurysm by proximal and distal ligation of the aneurysm sac (exclusion) combined with aortic bypass has been previously reported. A 10-year experience with 831 patients undergoing this procedure was reviewed. METHODS: From 1984 to 1994, 831 (761 elective, 70 urgent) of 1103 patients being treated for abdominal aortic aneurysm underwent repair with the retroperitoneal exclusion technique. Perioperative morbidity and mortality, estimated blood loss, transfusion requirements, natural history of the excluded aneurysm sac, and long-term survival were all assessed. RESULTS: The operative mortality rate for patients undergoing exclusion and bypass was 3.4%. The incidence of nonfatal perioperative complications was 5.2%. Colon ischemia requiring resection occurred in 2 (0.2%) of the 831 patients. Estimated blood loss was 638 +/- 557 cc (50 to 330 cc). On follow-up 17 (2%) patients were found to have patent aneurysm sacs as detected by duplex examination. Fourteen patients required surgical intervention. No cases of graft infection or aortoenteric fistula have been noted. CONCLUSION: Retroperitoneal exclusion and bypass is a viable alternative to traditional open endoaneurysmorraphy in surgery for abdominal aortic aneurysm. Most excluded aneurysm sacs have thrombosis without any long- or short-term complications; however, in a small number of patients delayed rupture of patent aneurysm occurs, thus emphasizing the need for diligent follow-up and appropriate intervention.

Adult↗
PubMed1996

Results of 1000 consecutive elective abdominal aortic aneurysm repairs.

In order to identify major risks for death and complications from elective repair of abdominal aortic aneurysm, the authors analyzed their experience with the last 1000 such repairs over a 15-year period. Of the patients, 772 were men and 228 were women; average age was 70 (range 37-92) years. Some 20% of the patients had severe chronic obstructive pulmonary disease and 33% had baseline creatinine level > 115 mumol/l. Fifteen patients were dialysis-dependent and 24% (242/1000) had significant cardiac disease. Operation used a retroperitoneal approach in 834 patients and a transperitoneal approach in 166. The perioperative mortality rate was 2.4%, but this did not change either chronologically or with technique: some 50% of the deaths were due to cardiac causes. Renal and pulmonary impairment did not affect mortality or complication; 64% of non-fatal complications were distributed in the renal (17%), pulmonary (19%) and cardiac groups (28%). The authors' experience showed that patients with cardiac disease remain at significant risk for post-abdominal aortic aneurysm repair complications in spite of selective preoperative cardiac evaluation. Renal and pulmonary risk factors did not cause additional mortality or morbidity. They suggest that elective abdominal aortic aneurysm repair can be performed with low mortality and morbidity, even in increasing numbers of high-risk patients.

Adult↗
PubMed1996

Bilateral carotid endarterectomy during the same hospital admission.

The efficacy of carotid endarterectomy for the prevention of strokes has been well demonstrated in recent multicenter randomized trials. However, patients presenting with bilateral significant disease pose a difficult problem to the vascular surgeon. Currently, bilateral carotid endarterectomies are staged at varying intervals between operations, with surgeon and patient weighing the risks of waiting for surgery versus the risks of having both procedures done within a shortened interval. There are few data and no consensus on the optimal time interval between these operations. In order to evaluate the timing of carotid endarterectomies in patients with severe bilateral disease, the authors reviewed their experience with patients who had bilateral procedures performed during one hospitalization. Over the past 5 years, they have performed 204 such carotid endarterectomies in 102 patients. Cervical block anesthesia was used in 99% (201/204) of these procedures. All patients either had symptomatic disease, > 60% stenosis or severe ulcerative plaque as defined by duplex scan and/or preoperative angiography. Symptomatic stenoses were the operative indications in 39% (80/204) of the patients; the remaining 61% (124/204) were symptom-free. The majority of patients (80%; 164/204) had their second procedure performed within 2 days of their first operation. There was no operative mortality and only one permanent neurologic defect in this group for a combined stroke mortality rate of 1%. Three patients (1.5%) had transient neurologic deficits postoperatively which completely resolved by discharge. These data show that bilateral carotid endarterectomies can be performed safely and effectively during one hospital admission with a short interprocedural interval and without an increase in mortality or morbidity.

Aged↗
PubMed1996

Access to the right renal artery from the left retroperitoneal approach.

One of the perceived limitations of the left retroperitoneal approach to the aorta is inadequate access to the right renal artery. Many consider the need for a concomitant right renal artery revascularization a contraindication to performing an aortic reconstruction through the left retroperitoneum. Exposure of the right renal artery can be difficult due to the posterior course of the artery behind the vena cava. However, when the aorta is transected, the right renal artery can be easily approached with anterior and cephalad displacement of the aortic root. Over the past 3 years, 52 patients have had right or bilateral renal artery revascularization via the left retroperitoneal approach; of these procedures, 37 were performed with concomitant aortic procedures. In total, 34 patients had bilateral and 18 had unilateral revascularizations. Five patients had a transaortic endarterectomy performed, and 36 were bypassed with 6-mm expanded polytetrafluoroethylene side limbs from the aortic graft. Indications for revascularization were: 39 for suprarenal aortic bypass, seven for renal salvage and six for primary renovascular hypertension. All reconstructions have remained patent and all have been followed by serial duplex and renal flow scans (follow-up for 1-42 months). The operative mortality rate was 5.8% (3/52). There were no major cardiorespiratory complications in this group. Adequate exposure to the proximal right renal artery can be obtained through the left retroperitoneal approach to the aorta, and successful revascularization of one of both renal arteries can be technically performed with acceptable mortality and morbidity.

Adolescent↗
PubMed1996

Advances in the surgical repair of ruptured abdominal aortic aneurysms.

Over the past two decades, the mortality rate for elective repair of infrarenal abdominal aortic aneurysms has improved to an acceptable level (< 5%). However, surgical results of ruptured abdominal aortic aneurysms have remained fairly constant with about 50% in hospital mortality rates. Growing experience with the use of the left retroperitoneal exposure for elective aortic surgery allowed the authors to extend the use of this technique to the repair of ruptured abdominal aortic aneurysm. The extended left retroperitoneal approach using a posterolateral exposure through the 10th intercostal space allowed the surgeon expeditiously and reliably to obtain supraceliac aortic control by dividing the left crus of the diaphragm in all patients. In total, 104 aortic replacements were performed for ruptured abdominal aortic aneurysm during the past 7 years. Of these patients, 87 were men and 17 women; mean(range) age was 72(52-95) years. Hemodynamic instability (as defined by a systolic blood pressure of < 90 mmHg) was present before surgery in 41% (43/104) of patients. The operative mortality rate was 27.9% (29/104). Preoperative hemodynamic instability, time of operative delay and aortic cross-clamp time did not correlate with operative mortality. The median duration of intensive care unit stay was 4 (range 1-60) days and hospital stay 11 (range 6-175) days. The results of this series identified that a change in the operative technique for the repair of ruptured abdominal aortic aneurysm beneficially affected patient survival. The authors suggest that expeditious supraceliac control without thoracotomy is an excellent alternative and offers an advantage in the surgical management of ruptured abdominal aortic aneurysm.

Aged↗
PubMed1996

Expeditious management of ischemic invasive foot infections.

Management of infected ischemic diabetic limbs requires antibiotic therapy, abscess drainage, and revascularization. However, revascularization is often delayed for several days or weeks as the infection is controlled. In an effort to decrease hospital stay and costs and to increase limb salvage, a series of 974 extremities with distal occlusive disease were managed with autogenous distal bypass. Some 136 of these limbs (125 diabetic) had severe invasive infections. These patients received intravenous antibiotics in all cases and abscess drainage if necessary. Vascular reconstruction was carried out as soon as possible, within 48 h of admission. An in situ bypass was used preferentially (107 cases). Patients were maintained on intravenous antibiotics in the perioperative period. Partial foot amputations, when necessary, were performed in 111 cases, usually 3-5 days after vascular reconstruction. There were no graft infections or major wound infections. There were two cases of skin edge necrosis requiring reoperation due to flap mobilization and consequent ischemia. Urgent revascularization with an autogenous conduit may be carried out in patients with invasive foot infections expeditiously, with high rates of limb salvage. Graft and wound infections are not common in this setting. Costly prolonged pre-bypass hospitalization in these cases is unnecessary.

Amputation, Surgical↗
PubMed1995

Choice of peroneal or dorsalis pedis artery bypass for limb salvage.

BACKGROUND: Arterial bypasses performed for limb salvage have increasingly used peroneal and pedal arteries as outflow. However, few reports have been published that compare the patency of limb salvage of these alternative outflow tracts. In this report, we have examined our experience with peroneal and dorsalis pedis (DP) artery bypasses for limb salvage. METHODS AND MATERIALS: Of more than 3,000 infrainguinal reconstructions performed for limb salvage, 732 were completed to the peroneal artery. During the same period, 238 bypasses were performed to the DP artery. Patient demographics were similar in both groups. The in situ technique was used in 68% of the peroneal bypasses and in 66% of the DP bypasses, respectively. Translocated veins were used in 28% of bypasses, and spliced veins were used in 32%. RESULTS: Secondary patency rates for the DP bypass at 1 and 5 years were 89% and 67%, respectively, as compared with 89% and 78% for the peroneal artery bypass. Limb salvage rates for the DP bypass were 94% at 1 year and 86% at 5 years, as compared with 96% and 93% at 1 and 5 years, respectively, for the peroneal artery bypass. No statistical difference was found. Four (1.7%) hemodynamic failures occurred in the DP group and 10 (1.4%) in the peroneal group. Wound complications were seen in 9 (3%) patients in the DP group and in 11 (1.5%) in the peroneal group. CONCLUSION: This experience indicates that both peroneal and DP bypasses have acceptable patency and limb salvage rates. Selection of one of these two outflow tracts, where a choice exists, may depend on the conduit limitation and adjacent tissue infection; however, both outflow tracts are durable and hemodynamically effective for limb salvage.

Ankle↗
PubMed1995

Arterial reconstruction for limb salvage: is the terminal peroneal artery a disadvantaged outflow tract?

BACKGROUND: Arterial reconstructions performed for limb salvage have increasingly used distal perimalleolar and pedal arteries as outflow tracts. However, a paucity of reports comparing the patency and limb salvage rates of these outflow tracts has been published. In this report we examine our experience with distal peroneal artery reconstructions for limb salvage. METHODS: During the past 14 years 159 bypasses were performed to the distal peroneal artery (within 5 cm of the malleolus), 157 of which were performed by the medial approach and two by the lateral approach. RESULTS: Sixty-three percent of the patients were male, 65% were diabetics, and 43% were smokers; the average age was 72.6 years. Sixty-five percent of the bypasses were performed with the in situ technique. Thirty-one percent of the bypasses were performed with translocated or spliced vein technique, and seven (4%) were performed with prosthetic technique. Secondary patency rates for distal peroneal artery bypass grafts at 1 and 5 years were 86% and 75%. The limb salvage rate for distal peroneal artery bypasses was 87% at 5 years. Four hemodynamic failures occurred in this group. Wound complications requiring revision were seen in one patient with a distal peroneal bypass (0.6%). These results do not differ from our results with other perimalleolar vessels. CONCLUSIONS: Arterial reconstruction to the distal peroneal artery has acceptable patency and limb salvage rates. These bypasses are as effective and durable as other perimalleolar bypasses.

Adult↗
PubMed1994

Can the deep femoral artery be used reliably as an inflow source for infrainguinal reconstruction? Long-term results in 563 procedures.

PURPOSE: Historically, most infrainguinal bypasses originated from the common femoral artery. In spite of sporadic reports of the use of the deep femoral artery as an inflow source, its durability has not been critically reviewed. METHODS: From 1977 to 1994, 2829 infrainguinal reconstructions have been performed. Of these, 563 (20%) procedures have been performed with the deep femoral artery used as the inflow source. The indication for operation was limb salvage in 91.5% of cases. Four hundred eleven procedures were performed with use of the saphenous vein in situ, 48 were performed with partial in situ vein, and 75 were performed with excised (translocated) vein (29 other). When the deep femoral artery was relatively disease free, it was accessed through a lateral or standard inguinal approach. Reasons given for the use of the deep femoral artery were inadequate vein length, concomitant inflow procedures, prior groin dissections, and occluded superficial femoral artery. RESULTS: The 1- and 5-year secondary patency rates for all bypasses with the deep femoral artery were 90.4% and 76.9%, respectively, as compared with 88% and 73.3% for common femoral artery-based bypasses. Sixty-five patients (11.5%) had concomitant inflow procedures. All patients were monitored with serial noninvasive examinations, and data were collected from the vascular registry. Only eight patients (1.6%) required further inflow reconstructions for salvage of bypasses. CONCLUSIONS: The hemodynamically unobstructed deep femoral artery is a reliable and durable inflow source for patients requiring infrainguinal bypasses. Its patency rates are comparable to those of the common femoral artery-based reconstructions in our experience.

Femoral Artery↗
PubMed1993

Aortic replacement for abdominal aortic aneurysm in elderly patients.

Improvements in the operative mortality and morbidity rates in elective aortic replacement, which are largely a result of refinements in surgical technique and perioperative management, have allowed a more aggressive approach in the treatment of abdominal aortic aneurysm (AAA) in elderly patients. To evaluate this approach, we reviewed the records of 116 patients 80 years of age and older (range: 80 to 93 years) who consecutively underwent aortic replacement for AAA. Seventy-seven patients underwent elective aortic replacement with 8 complications and a 3% operative mortality rate (2 of 77). Emergent aortic replacement was performed in 39 patients (14 with symptomatic nonruptured AAA and 25 with ruptured AAA) with 12 complications. In this nonselective subset, there were eight deaths, for an operative mortality rate of 20% (symptomatic 14%, ruptured 24%). In comparison, 780 patients less than 80 years of age underwent aortic replacement during the same time period. Within this group, 622 patients who were treated on an elective basis had a similar operative mortality (2%) as did patients 80 years of age and older. On the basis of these results, we believe that elective aortic replacement in elderly patients is justified and can be achieved with low operative mortality and morbidity rates. We suggest that the chronologic age of the patient should not deter aortic replacement.

Aged↗
PubMed1993

Is the iliac artery a suitable inflow conduit for iliofemoral occlusive disease: an analysis of 514 aortoiliac reconstructions.

PURPOSE: The aorta is the conventional inflow source for reconstructions in patients with aortoiliofemoral occlusive disease. In patients with unilateral iliac or femoral disease, femoral-to-femoral bypasses have been used but with less favorable patency rates. The purpose of this study is to evaluate the performance of the unobstructed iliac artery as an inflow source for ipsilateral, contralateral, or bilateral reconstructions in iliofemoral occlusive disease. METHODS: Over the past 6 years 322 reconstructions have been performed with the iliac artery as the donor vessel. Patients were evaluated for proximal hemodynamically significant lesions by augmented pullout pressures during aortography. Patients who had balloon angioplasty were excluded. RESULTS: Results were compared with 192 patients who underwent conventional aortodistal bypass operation for occlusive disease during the same period. Both groups were similar in risk factors, age, sex, and indications for operation. For the iliac group the operative mortality rate was 1.6%, and the 30-day patency rate was 97%, similar to those in the aortic group (3.6% and 95%, respectively). Cumulative patency rates at 5 years by life-table analysis were 82% for iliac artery inflow and 77% for aortic inflow reconstructions. CONCLUSIONS: Our experience suggests that an unobstructed iliac artery is a reasonable inflow source for reconstructions in iliofemoral occlusive disease. The long-term patency rate is comparable to aortodistal bypasses and superior to other extraanatomic bypasses.

Aorta, Abdominal↗
PubMed1989

The in situ bypass above the knee.

The anatomical location of the saphenous vein in the distal thigh allows for construction of an in situ bypass to the above-knee popliteal artery. The authors have performed over 1400 in situ bypasses in the past 10 years. Forty-three of these have been to the above-knee popliteal artery. Thirty-three bypasses were performed for limb threatening ischemia, seven for disabling claudication and three for microemboli. Mean patient age was 67 years, 51% were males, 44% had diabetes mellitus, and 93% smoked. Grafts were followed from one to 108 months. The cumulative patency rate at two years was 90% and at four years 77%. Patency rates compare favorably to those of femoral-to-above-knee popliteal bypasses constructed using reversed saphenous vein or polytetrafluoroethylene. The authors found that the in situ femoral-to-above-knee popliteal bypass is a technically easy procedure requiring short operative times and has a low morbidity rate. In those select patients in whom a femoral-to-above-knee bypass is the procedure of choice the in situ bypass should be considered.

Adult↗
PubMed1989

Evaluation of vitamin K3 feed additive for prevention of sweet clover disease.

Sweet clover poisoning in cattle is caused by an anticoagulant (dicumarol) that is formed in moldy sweet clover hay. Previous experiments with vitamin K3 and vitamin K1 in therapy trials indicated that vitamin K1 was effective in reducing prothrombin times but vitamin K3 was not. As a possible alternative in the use of toxic sweet clover hays, vitamin K3 was evaluated to see if it would prevent hemorrhagic crises when fed to cattle consuming toxic sweet clover hay. Vitamin K3 levels of 0, 0.45, 4.5, 11, and 45 mg/kg body weight/day were fed to 173-235-kg steers consuming toxic (40-50 ppm dicumarol) sweet clover. The 45-mg K3/kg/day supplement was not palatable and had to be discontinued. The 0.45, 4.5, and 11-mg K3/kg/day supplements did not significantly reduce the prothrombin times as compared to the 0-mg K3/kg/day group.

Animals↗
PubMed1988

Origin of deep vein thrombi in an ambulatory population.

Eighty symptomatic ambulatory outpatients with acute deep vein thrombosis were evaluated with ascending contrast venography and ultrasonic imaging to determine the origin and distribution of thrombosis and to analyze clinical risk factors. Isolated calf vein thrombosis was present in 42.5 percent of the limbs, combined calf and proximal deep vein thrombosis in 47.5 percent, and isolated proximal thrombosis in 10 percent of the limbs. Discontinuity of thrombus was present in 55 percent, whereas 45 percent exhibited a continuous column of thrombus. The results of this study indicate that in the ambulatory outpatient population, acute deep vein thrombosis begins segmentally in the calf and proximal vessels and frequently coalesces into a continuous column of thrombus over several days. We believe that all cases of acute deep vein thrombosis should be treated and patients with evidence of previous acute deep vein thrombosis should be closely monitored for possible recurrences.

Adult↗
PubMed1988

Venous thrombosis: the clinical problem.

Although the exact cause of DVT is not known, venous thrombosis and its sequelae remain important clinical problems. Pulmonary embolism is a significant cause of morbidity and mortality in the hospitalized population, and the postthrombotic syndrome affects a large portion of the general population. While specific screening tests are not readily available to detect those patients who are likely to develop DVT, certain clinical risk factors have been identified that predispose to thrombosis. These groups include patients undergoing a wide variety of surgical procedures, patients with cardiac disease or cancer, pregnant or postpartum women, and individuals with previous history of DVT. The diagnosis of thrombosis is based on clinical findings and must be confirmed with appropriate laboratory tests. While contrast venography remains the gold standard, noninvasive tests have become increasingly more accurate. The recent use of real-time B-mode ultrasonic imaging and duplex sonography for the diagnoses of DVT has been shown to be efficacious. The postthrombotic syndrome with its associated chronic pain and ulcerations remains a significant clinical problem. The general diagnosis of this condition is readily made on clinical grounds in the advanced state. However, exact knowledge of the location and cause of the venous pathology can only be obtained using objective diagnostic tests. Older noninvasive and invasive tests may diagnose the presence of venous obstruction, valvular incompetence, and also may document venous hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1987

Pharmacokinetics of xylazine in ponies: influence of yohimbine.

Twenty healthy ponies were given i.v. 1.1 mg/kg of xylazine from 2 manufacturers and the pharmacokinetic parameters calculated from the disposition curves. The disposition curves for the 2 commercial preparations were not different. Yohimbine, an antagonist of the pharmacologic effects produced by xylazine, did not alter the disposition of xylazine in the plasma. A single i.v. bolus of xylazine was completely described in 17 of 20 animals by the biexponential equation: Cp = 1.30e(-0.3955t) + 0.58e(-0.033t) where Cp represents the concentration of xylazine in the plasma at time t (min). The t1/2 beta was 75 +/- 13 min and whole body clearance was 18.9 +/- 1.5 (ml/min.kg).

Animals↗