Artificial pancreas using living beta cells:. effects on glucose homeostasis in diabetic rats.

An artificial pancreas consisting of beta cells cultured on synthetic semipermeable hollow fibers was tested in rats with alloxan-induced diabetes. When implanted ex vivo as arteriovenous shunts in the circulatory system these devices lowered concentrations of plasma glucose from 533 to between 110 and 130 milligrams per 100 milliliters, increased concentrations of plasma insulin, and restored intravenous glucose tolerance tests essentially to normal.

Hepatic regeneration in the absence of portal viscera.

In an effort to investigate the influence of portal factors on hepatic regeneration in the rat and to clarify glucagon's apparent regulatory role, a rat preparation was developed which was totally devoid of portal viscera and thus deficient in all possible hepatotrophic substances of portal origin. It was found that, following partial hepatectomy, such an eviscerate rat was able to undergo hepatic deoxyribonucleic acid (DNA) synthesis, but the peak DNA synthetic response was significantly delayed by such portal deprivation. As demonstrated by a group of rats with intact portal viscera, but with a portacaval shunt, reduction of blood supply to the hepatic remnant by diversion of portal flow accounted for only a portion of the delay. The remainder of the delay encountered in the eviscerate group was attributed to the deprivation of specific portal substances. Since glucagon supplementation administered to the deficient eviscerate animal restored peak DNA synthesis to the time of its appropriate shunted control, this hepatotrophic substance is a major portal factor modifying the response to partial hepatectomy. Evidence is cited which suggests that glucagon's influence on DNA synthesis is mediated through the formation of cyclic adenosine monophosphate (AMP) and subsequent histone phosphorylation.

The fate of bypass grafts to an isolated popliteal artery segment.

From 1967 to 1982, 55 patients underwent 64 femoropopliteal bypass grafts into an isolated popliteal artery segment. Seventy-six percent of these patients had threatened limb loss from advanced atherosclerosis, and 24% had disabling claudication. Forty-five percent of the patients were diabetic. The 30-day operative mortality rate was 1.6%, and the 30-day postoperative amputation rate was 3.2%. Graft potencies were analyzed by the life table method. The 2-year graft patency rate was 70.6%, and the 5-year patency was 60.7%. The 2- and 5-year limb salvage rates were each 83%. With evidence for decreased graft function, four grafts (6%) were successfully revised before failure occurred. Among 10 polytetrafluoroethylene grafts followed up to a maximum of 48 months, there was one early postoperative occlusion, one long-term occlusion, and one early amputation. With respect to patency and limb salvage, the results of isolated popliteal artery segment grafts fall between the 5-year patency and limb salvage rates for autogenous vein grafts to popliteal arteries with at least one tibial vessel runoff (78% patency and 89% limb salvage) and the rates for femoral-tibial/peroneal grafts (5-year patency 56%, limb salvage 69%). An isolated segment is an appropriate recipient vessel for a reconstruction for limb salvage, and reasonably good results can be anticipated.

The iliac-origin arterial graft: a useful alternative for iliac occlusive disease.

The results of ilioiliac and iliofemoral bypass grafts were compared with those for aortic-origin grafts in 205 patients and 332 legs operated upon for aortoiliac occlusive disease since 1972. Poor-risk patients who had a patent distal aorta and at least one functionally patent proximal iliac artery were considered for reconstruction with the iliac artery used for the proximal anastomosis. The procedure, performed through a retroperitoneal approach, has several technical advantages and is especially satisfactory for patients who would otherwise have an axillofemoral graft. The data indicate that these iliac-origin reconstructions compare favorably in patency with aortic-origin reconstructions or with other "extra-anatomic" arterial reconstructions, enabling extremely low morbidity and mortality rates even in high-risk patients.

Effect of aspirin and dipyridamole on the patency of lower extremity bypass grafts.

Recent clinical studies indicate that the use of aspirin and dipyridamole improves graft patency rates in patients with infrainguinal polytetrafluoroethylene (PTFE) grafts and aortocoronary vein grafts. We undertook a prospective, double-blind, randomized study to determine whether these drugs administered postoperatively to patients with PTFE or autologous vein infrainguinal bypasses would improve graft patency during the first 24 months after operation. Patients received either aspirin 325 mg and dipyridamole 75 mg or identical placebo tablets three times a day, taken orally. Patency rates were compared by computing standard life tables and comparing cumulative patency rates. One hundred patients with 102 grafts were studied. The cumulative patency rate at 24 months was not significantly different for the treatment (57%) versus control (67%) groups or for any subgroup. We conclude that aspirin and dipyridamole administered postoperatively in the doses used in this study do not improve the overall patency rates of vein or PTFE infrainguinal bypass grafts.

Carotid endarterectomy: an alternative approach.

Ninety-six consecutive carotid endarterectomies were carried out with each patient under regional anesthesia and with the routine use of an indwelling arterial shunt. When combined on a routine basis, the theoretical advantages derived from each technique become additive such that maximal cerebral protection afforded by the shunt is continuously monitored by an awake patient. The validity of this approach in a teaching setting is evidenced by a low (1%) mortality and morbidity and by an exceptional degree of patient compliance.

Thromboembolism from occult subclavian arterial stenosis during chemotherapy for breast carcinoma.

Cancer chemotherapy has been associated with hypercoagulability, causing thromboembolic complications. Three unusual and strikingly similar cases of upper-extremity arterial thromboembolism were encountered in women undergoing chemotherapy following surgical treatment for breast carcinoma. In all cases, previously asymptomatic stenosis of the subclavian artery due to extrinsic cause was suspected as the source of distal thromboembolism. These cases illustrate the interplay between transient hypercoagulability and underlying arterial disease in the pathogenesis of arterial thromboembolism.

Branched nonreversed saphenous vein graft for complex renal artery stenosis.

Use of recently developed instrumentation for venous valvotomy allows rapid construction of a branched, nonreversed saphenous vein graft. This technique was applied in a patient with renovascular hypertension and branch renal artery occlusive disease.

Femorotibial and femoroperoneal bypass vein grafts. A 15-year experience.

Results with 111 femoral-infrapopliteal vein grafts in 105 patients were subjected to life-table analysis. The overall five-year cumulative graft patency rate of 46% was associated with a 60% limb salvage rate. In cases in which the infrapopliteal graft represented the initial operative procedure, the five-year limb salvage and patency rates (69% and 56%, respectively) were significantly higher (P less than .05) than those achieved with secondary grafts (38% and 22%, respectively). Most limbs (79%) with failed intrapopliteal grafts, without further attempts at reconstruction, required major amputation within six months. The site of the distal anastomosis (anterior tibial, posterior tibial, or peroneal arteries) proved not to be a significant factor in determining long-term limb salvage or graft patency rates. Furthermore, the differences between five-year salvage and patency rates in diabetics (45% and 32%, respectively) and nondiabetics (65% and 53%, respectively) approached but did not reach statistical significance. It is believed these observations support the established but controversial role of infrapopliteal bypass in advanced peripheral occlusive diseases.

Recognition and management of impending vein-graft failure. Importance for long-term patency.

A previous report from this group indicated a very poor long-term patency rate (19%) for occluded femoro-distal vein grafts that require initial thrombectomy prior to patch angioplasty for documented stenosis. Patients with vein grafts were therefore followed up by Doppler pressure determinations of the ankle/brachial index (ABI) postoperatively at three weeks, six weeks, and every four months thereafter for two years in an effort to identify vein-graft failure prior to actual thrombosis. During the past six years we performed 322 vein grafts of which 29 grafts were identified by diminished Doppler ABI and were found to have stenotic segments on subsequent arteriography. Twenty-two of these patients (group 1) underwent reconstruction with patch angioplasty resulting in a five-year cumulative patency rate of 82%. The remaining seven patients (group 2) underwent percutaneous transluminal angioplasty of their stenotic segments yielding a significantly lower five-year patency rate of 43%. These two groups were compared with a third group fo 25 patients with thrombosed grafts mandating initial thrombectomy prior to patch angioplasty. The thrombectomized group 3 patients demonstrated a significantly lower five-year cumulative patency rate of 28%. These data suggest that patients with femoro-distal bypass vein grafts be followed up at frequent intervals early in their postoperative course with determinations of Doppler ABI measurements. Any significant reduction in Doppler ABI compared with the highest postoperative Doppler determination should be aggressively evaluated with digital-subtraction or routine angiography in an effort to locate a stenotic lesion prior to graft thrombosis. Patients found to have such a graft stenosis are then ultimately treated with patch angioplasty in anticipation of satisfactory long-term patency rates.

Thrombolysis in the treatment of peripheral arterial vascular occlusions.

The efficacy of thrombolytic agents in the management of peripheral arterial disease remains unclear. We reviewed our experience with 64 consecutive episodes of limb-threatening graft or native vessel occlusions. The overall success rate was 59%, with a major complication/mortality rate of 28%. Thrombolytic therapy in patients with occluded vascular grafts required identification of a causative lesion and subsequent adjunctive management with percutaneous transluminal angioplasty or surgery for sustained patency (64%). In contrast, approximately 70% of native vessel occlusions maintained patency whether a causative lesion was identified and corrected or not. Patients who failed thrombolytic therapy had a worse prognosis overall, with 38% undergoing primary amputation, although patients with reconstructable occlusions still had a 64% salvage rate at six months. The review demonstrated that thrombolytic therapy continues to be a useful adjunct in treating the patient with peripheral vascular occlusion, although a significant risk of major complications persists. Patients with graft occlusions successfully treated with thrombolysis require correction of any precipitating lesions for long-term limb salvage, while careful management of patients failing thrombolysis can still achieve significant limb salvage in selected cases.

Coexistent carotid and coronary artery disease. Surgical management.

We performed simultaneous coronary artery bypass grafting (CABG) and carotid endarterectomy (CE) in 42 patients (average age, 61 years). Twenty-nine patients had preoperative transient ischemic attacks. Carotid arteriography showed stenosis (greater than 70%) in 38 subjects and extensive ulcerated lesions in two, and two emergency patients were not studied. Carotid artery dissection and sternotomy were simultaneously performed and the patients were cannulated for cardiopulmonary bypass (CPB). We undertook CE (22 left and 24 right) using EEG monitoring prior to CPB in all but one patient. The average carotid occlusion time was 25 minutes without a shunt in 23 patients and 5.5 minutes with a shunt in 19 patients. After CE, CABG was performed with an average aortic clamp time of 39 minutes and an average CPB time of 87 minutes. The operative mortality was 5% (2/42). There were no strokes or perioperative myocardial infarctions. Neurologic morbidity consisted of postoperative headache in one patient, transient upper-extremity weakness in two patients, and transient facial weakness in one patient. The average length of postoperative hospitalization was ten days. Currently, patients with symptomatic coronary artery disease and concomitant carotid bruits with positive noninvasive testing and arteriography should have simultaneous repair of these lesions.

The place of abdominal aortography in abdominal aortic aneurysm resection.

We analyzed 110 patients who underwent abdominal aortography as a routine preliminary to abdominal aortic aneurysm resection. In 11 of the 15 patients for whom the procedures were useful in planning the operative tactics, the aortograms would have been performed anyway on clinical indications. In two patients, the changes in surgical maneuvers would not have been made through anatomic inspection at the time of the operations, but the lesions were asymptomatic. Biplane views and views of the femoropopliteal systems were rarely influential. Morbidity from the angiography was minimal and mortality was zero, but about seven aortograms were performed for each one that effected a change in procedure. We concluded that abdominal aortography as a preliminary to aneurysmectomy could be reasonably limited to patients in whom it was indicated by clinical features, including important hypertension, impaired renal function, diminished or absent femoral pulses, suspected mesenteric ischemia, suspected suprarenal extension of the aneurysm, or suspected (from the chest roentgenograms) thoracic aneurysm.

Femoropopliteal reconstruction for claudication. The risk to life and limb.

The current study was undertaken to examine the results of femoropopliteal bypass grafting with intermittent claudication as the indication. Of 1173 infrainguinal reconstructions carried out on our service during the past decade, 249 (21%) consecutive femoropopliteal grafts were performed for disabling claudication in 191 patients. The primary five-year cumulative patency rates were 78% for autogenous vein and 52% for polytetrafluoroethylene grafts. There were two (0.8%) 30-day operative deaths and a subsequent five-year amputation rate of 2.4% for both groups. Femoropopliteal reconstruction for claudication may therefore be carried out with acceptably low operative mortality and a subsequent amputation rate comparable with that anticipated from the natural history of the disease. While the five-year patency rate is significantly higher utilizing autogenous vein grafts, symptomatic relief may be expected with prosthetic grafts in approximately half the patients without incurring a higher risk of limb loss.

Combined carotid and coronary revascularization: the preferred approach to the severe vasculopath.

The timing of carotid endarterectomy (CEA) and coronary revascularization (CABG) for concomitant disease is controversial. Results of combined CEA/CABG in 127 patients (age range, 46 to 82 years; mean age, 65 years; 61% male) from 1978 to 1991 were reviewed. Ninety-five patients (75%) were in New York Heart Association functional class III or IV, 48 (38%) had left main coronary artery disease, and 32 (28%) had depressed ejection fraction ( < 0.50). Forty (32%) had asymptomatic bruits, 61 (48%) transient ischemic attacks, and 26 (20%) prior strokes. Seventy-five (59%) had bilateral carotid stenosis, including 20 (16%) with contralateral occlusions. Perioperative mortality was 7 of 127 (5.5%), and all deaths were cardiac related. Myocardial infarctions occurred in 6 of 127 patients (4.7%) and were nonfatal in 3 (2.3%). Permanent strokes occurred in 7 of 127 (5.5%) and were ipsilateral in 5 (3.9%). Perioperative stroke did not occur in the asymptomatic group, but the risk was higher in those with prior stroke (19%) or with contralateral carotid occlusion (15%). The stroke risk for our patients with carotid disease having CABG without CEA is not known, but the literature reports rates as high as 14%. For our patients without known concomitant disease, the risk of permanent stroke was 1.0% (31/3012) for isolated CABG and 1.5% (7/482) for isolated CEA. The late results after CEA/CABG revealed a 5-year survival of 70% +/- 5%, which correlated with ejection fraction ( > or = 0.50, 81% +/- 5%; < 0.50, 45% +/- 11%; p < 0.003). Freedom from late permanent ipsilateral stroke was 97% +/- 2% at 8 years. Freedom from stroke at 5 years was lower among patients with a previous stroke (71% +/- 10%) compared with transiently symptomatic (90% +/- 4%) and asymptomatic (96% +/- 4%) patients (p < 0.03). Combined CEA/CABG is a useful option in this high-risk group of patients with extensive atherosclerosis; avoids a subsequent hospitalization, anesthetic, and delay period; and provides long-term protection from ipsilateral stroke.

The impact of gender on the results of arterial bypass with in situ greater saphenous vein.

BACKGROUND: This 10-year review of in situ saphenous vein bypass surgery was undertaken to assess the impact of gender on infrainguinal arterial reconstruction. PATIENTS AND METHODS: From March 1983 to March 1993, the results of 244 in situ saphenous vein bypasses performed in women were compared with 338 performed in men. Women were older than men (70.9 versus 66.8 years; P < 0.001) and had a higher incidence of hypertension but a lower incidence of coronary artery disease, smoking history, and chronic obstructive pulmonary disease. The primary indication for surgery was limb salvage for both genders (women 70.1%, men 68%; P = not significant [NS]). Men had bypasses to more-distal outflow vessels with 52.5% to the tibial level compared with 42.2% of women (P < 0.003). RESULTS: Women had lower perioperative mortality rates than men (0.8% versus 3.3%; P < 0.025) and a similar incidence of major complications (6.6% versus 7.7%; P = NS), but a higher incidence of significant wound complications (13.5% versus 3.3%; P < 0.001). Life-table evaluation at 10 years after surgery showed no significant differences between women and men in primary graft patency rate (67.8% versus 58.2%; P = NS), secondary patency rate (73.5% versus 77.2%; P = NS ), limb salvage rate (87.9% versus 92%; P = NS) or patient survival rate (35.5% versus 24.4%; P = NS). For bypasses to the tibial arteries, graft patency rates were slightly inferior for women (69.8% versus 81.1%, 5-year secondary patency rate; P < 0.008). Similarly, in bypasses performed for limb salvage, women had lower 5-year primary patency rates than men (60.3% versus 70.3%; P < 0.002). Secondary patency rates in this limb salvage group however, did not differ (75.5% versus 82.8%; P = NS). CONCLUSIONS: Despite small gender differences in the results of in situ bypass grafts for limb salvage and those carried to the tibial level, women had the same overall patency, limb salvage, and survival rates as men after infrainguinal bypass surgery. Treatment of infrainguinal occlusive disease should not vary based on inaccurate perceptions concerning differences in surgical results for men and women.

Optimal methods for autogenous bypass to the anterior tibial artery.

BACKGROUND: Autogenous bypass to the anterior tibial artery (AT) has been increasingly used for infrageniculate revascularization. The conduit may be routed through the interosseous membrane, a pretibial tunnel, or through a lateral thigh and calf tunnel. This study reviewed results of AT bypass to determine the optimal routing method. METHODS: One hundred thirty consecutive vein grafts to the AT were analyzed retrospectively to compare the experience with the interosseous (group I; n = 50), pretibial (group II; n = 51), and lateral (group III; n = 29) routing alternatives. RESULTS: Indications were claudication in 16 (12.3%) and critical ischemia in 114 (87.8%) procedures with no differences among routing subgroups. Ectopic nonreversed and composite conduits were more common in group III. Major operative morbidity occurred after 7 procedures (5.4%) with no differences in early graft failure (7.7% overall) among the three routing subgroups. Wound infections were more common among group I patients, but without predilection to the interosseous tunnel. During a mean follow-up of 24.9 months (0 to 111.2) overall 5-year secondary patency was 70% with no difference among routing technique. CONCLUSION: Optimal routing choice depends on the location of suitable AT, the length of adequate vein conduit, and the surgeon's preference rather than on factors inherent to the method used.

Management of ruptured or symptomatic abdominal aortic aneurysms.

During the past 15 years, the operative mortality for elective repair of abdominal aortic aneurysms has declined; this favorable trend has very likely resulted from simplified operative technique and improved perioperative management. Unfortunately, however, there has been no comparable decline in the mortality associated with repair of ruptured abdominal aortic aneurysms. The management of these patients remains a challenge to even the most skilled and experienced vascular surgeon.

Mesenteric revascularization during aneurysmectomy.

The most important association between aortic aneurysm surgery and the mesenteric circulation is the potential for inadvertent compromise to the mesenteric trunks and their end organs. Preservation of visceral blood flow is a critical objective in each case, using methods that have been developed as techniques for suprarenal abdominal and thoracoabdominal aneurysmectomy have evolved. Beyond simply preserving what existed, revascularization by endarterectomy or bypass has a role in selected cases to improve the natural history of advanced mesenteric occlusive disease, although the rationale for such prophylactic surgery must remain relatively weak until more is learned about disease progression in the visceral arteries. Finally, a small number of patients with mesenteric ischemic symptoms at the time of aneurysmectomy clearly benefit from combined surgery.

Reoperative approaches for failed infrainguinal vein grafts.

The management of patients with thrombosed vein grafts remains a formidable challenge for all vascular surgeons. Management strategies will vary based on a variety of criteria including the patients' overall condition and symptoms, the interval and etiology of graft failure, and the pathological anatomy and availability of autogenous vein. A combination of resourcefulness and adherence to established vascular surgical principles and techniques will facilitate revascularization in the great majority of patients with failed grafts.