Biomedical subjects

B B Chang

Publications and source records attributed to B B Chang.

At least 91 records · Page 5Linked to original sources

PubMed1992

Is long vein bypass from groin to ankle a durable procedure? An analysis of a ten-year experience.

Long vein bypass from the femoral artery to the level of the ankle may be performed with good initial success despite extreme bypass length and limited outflow tracts. However, the long-term performance of these bypasses remains to be defined. During the last 10 years we have performed single greater saphenous vein in situ bypass to the ankle level in 270 patients. There were 187 male and 83 female patients, and 61% of the patients were diabetic. The operative mortality rate was 3.7%. Cumulative bypass patency was 79% at 3 years and 73% at 5 years. In a similar manner, limb salvage was 93% at 3 years and 89% at 5 years. The patency rate was similar for various inflow arteries (common femoral, 88 cases; proximal superficial femoral, 135 cases; and deep femoral, 41 cases) and outflow tracts (dorsal pedal, 72 cases; anterior tibial, 59 cases; posterior tibial, 72 cases, and peroneal, 67 cases). Short bypasses, composite bypasses, free-vein grafts, and bypasses proximal to 10 cm above the ankle were excluded from this analysis. These data show that a long bypass to the ankle level for limb salvage is a durable procedure. The basic concept of bypassing all occlusive disease to the distal open artery in patients undergoing limb salvage should be an acceptable dictum. Excellent long-term patency and limb salvage rates are achievable by following this principle.

Adult↗

PubMed1991

Local anesthesia for surgery on the foot: efficacy in the ischemic or diabetic extremity.

The efficacy, risks, and benefits of the use of local anesthesia for surgery on the foot were assessed in 75 patients who underwent 127 procedures with lower calf, ankle, metatarsal-ray, and digital blocks. There were 23 procedures on digits alone, 97 forefoot operations (transmetatarsal amputations, wound debridements, closures, osteotomies, joint resections), six ankle or hind-foot amputations, and one open ankle disarticulation. There were no complications directly related to the use of local anesthesia; specifically, no extension of preexisting infection or ischemia due to injection in the foot. There were three deaths (30-day mortality 4%). The procedures were uniformly well tolerated, even in patients with ongoing myocardial ischemia or severe metabolic disorders. Local anesthesia is a safe and effective method to perform local debridement or amputation of the foot in an ischemic or diabetic extremity.

Aged↗

PubMed1991

Acute arterial insufficiency of the male genitalia.

Three patients developed severe ischemia of the penis or scrotum from acute arterial occlusion. In one case, nonhealing ulceration of the glans developed after atheroembolism to the dorsal penile artery. One patient had penile ischemia after ligation of pelvic and femoral collateral circulation during repair of an aorto-bilateral-iliac artery aneurysm. A third patient had ischemia of the penis and scrotum from thromboembolism to the iliac arteries during repair of an aortoenteric fistula. Only seven patients have been described with acute arterial occlusion and severe ischemia of the male genitalia. A rare phenomenon because of rich collateral circulation, acute ischemia of the genitalia nevertheless must be recognized as a sign of severe vascular disease and a consequence of major arterial ligation or occlusion in the pelvis and groins.

Acute Disease↗

PubMed1991

Treatment of abdominal aortic aneurysm by exclusion and bypass: an analysis of outcome.

Abdominal aortic aneurysm is conventionally treated by aneurysmorrhaphy with inlying graft. Alternatively, division of the aorta, with suture closure of the distal aorta and outflow vessels (exclusion of the aneurysm), and end-to-end proximal to distal bypass may be performed. However, the long-term fate of this operation has not been determined. Specifically, concern exists that the excluded blood filled aneurysm may not thrombose or may be the source of late sepsis. During an 8-year period we have treated 280 abdominal aortic aneurysms (urgent and elective) by exclusion of the abdominal aortic aneurysm sac and bypass via the posterolateral retroperitoneal approach. Mean age was 70 years (range, 44 to 88), with 217 men and 63 women. Preoperative CT scanning and aortography were performed to assess arterial anatomy. Seventy tube grafts and 260 bifurcation grafts were used. Thirty-day mortality rate was 4%. Estimated blood loss was 731 +/- 52 ml; mean transfusion requirements were 456 +/- 82 ml. The minor complication rate was 6%, and it is of great interest that there were no cases of ischemic colitis requiring colectomy. Aneurysm sacs thrombosed except in two anticoagulated patients who required further treatment. No late infections occurred. Five-year bypass patency rate was 98%. These data demonstrate that this method of treatment effectively minimized operative dissection and blood loss and therefore is a viable alternative for the management of abdominal aortic aneurysms.

Aged↗

PubMed1990

Impact of the presence of orthopedic hardware on technical performance of major amputations.

Metallic prostheses used for joint reconstruction or open reduction of fractures were discovered pre- or intraoperatively during the performance of six above-knee amputations. The prosthesis was found fortuitously before surgery in two cases on the basis of a surgical scar or radiograph of the leg. In four patients, discovery occurred intraoperatively, with adverse impact on the procedure in two cases: more proximal amputation level to allow hip nail removal was necessary in one case, and difficult transection of the prosthesis stem was encountered in one case. Orthopedic prostheses will be found with an increasing incidence in the population undergoing major amputation. As preparation for amputation, a careful review of the patient's history, a search for scars over the leg and hip, and survey radiographs of the leg must be obtained to prevent a surgical mishap caused by accidental discovery of a prosthesis.

Amputation, Surgical↗

PubMed1990

The role of extraanatomic exclusion bypass in the treatment of disseminated atheroembolism syndrome.

We treated six patients with disseminated atheroembolism complicated by severe and unremitting pain from bilateral foot lesions. All patients had multiple and severe medical risk factors. One patient had a recent myocardial infarction, six patients had renal failure, and three were undergoing hemodialysis. Definitive aortic reconstruction was therefore precluded. After failing a course of medical therapy, each patient was treated with axillobifemoral bypass with exclusion-ligation of the external iliac arteries. Healing of foot wounds occurred in 11 of 12 limbs at risk, with one below-knee amputation required for progressive forefoot necrosis. In 12 patients with severe cardiopulmonary disease and limited life expectancy, exclusion-ligation bypass is an effective and safe palliative procedure for severe disseminated atheroembolism.

Aged↗

PubMed1990

Antibiotic therapy for arterial infection: lessons from the successful treatment of a mycotic femoral artery aneurysm without surgical reconstruction.

A mycotic femoral artery aneurysm developed in a diabetic man with bacteremia from a Staphylococcus aureus urinary tract infection. Because of severe concomitant congestive heart failure and hypothyroidism, surgical reconstruction of the femoral artery was deferred while the patient received an intensive course of intravenous nafcillin. This led to stabilization of the size of the femoral aneurysm for two years, during which time it remained asymptomatic. Three such cases of nonsurgical treatment of a mycotic aneurysm have been documented. Surgical ligation, drainage, and bypass remain the mainstay therapies for mycotic aneurysms, but these cases demonstrate the possibility of sterilizing a primary arterial infection under the highly selected circumstances of an exquisitely sensitive organism, absence of periarterial abscess and readily observable anatomic location. Most importantly, these cases provide assurance that a six-week course of parenteral antibiotics is a reasonable adjunctive treatment for residual endovascular infection.

Aged↗

PubMed1990

Can the retroperitoneal approach be used for ruptured abdominal aortic aneurysms?

The retroperitoneal approach for elective treatment of abdominal aortic aneurysms is an accepted alternative to midline transperitoneal approaches and may provide less physiologic insult and a smoother postoperative course. In recent years we have preferentially used the extended retroperitoneal approach for ruptured abdominal aortic aneurysms to derive similar physiologic benefits for these patients. Over a 6-year period (1983 to 1989) 76 cases of ruptured abdominal aortic aneurysms were treated by emergency aortic replacement. After exclusion of 13 patients whose aneurysmal ruptures were unusual, such as aortoenteric fistula, aortocaval fistula, chronic contained rupture, or visceral involvement, 63 patients were retrospectively studied. Thirty-eight patients were treated via a standard transperitoneal celiotomy and 25 via a left retroperitoneal incision. No significant differences were found between the two groups in regard to cardiac or pulmonary function or duration of preoperative hypotension. Operative mortality was lower in the retroperitoneal group (three of 25, 12%) as compared to the transperitoneal group (13 of 38, 34.2%). Furthermore, the retroperitoneal group required less ventilatory support and tolerated enteral feedings quickly. Length of stay in the hospital was also significantly reduced in the retroperitoneal group. These data indicate that many ruptured abdominal aortic aneurysms can be successfully treated through the left retroperitoneal approach. In this nonrandomized clinical series increased survival rates and shorter periods of postoperative recovery were noted in the patients operated with the retroperitoneal approach.

Aorta, Abdominal↗

PubMed1990

Immediate preoperative phlebotomy with autologous blood donation for aortic replacement.

The preferential use of autologous blood provided by phlebotomy can reduce the need for homologous blood transfusion in patients undergoing extensive elective operations. This blood is usually provided either by intraoperative isovolemic hemodilution or phlebotomy one to two weeks preoperatively. To minimize the intraoperative time delay or preoperative period between phlebotomy and operation required in these patients, we performed preoperative isovolemic hemodilution in 69 patients one to two days prior to elective aortic replacement for infrarenal aneurysmal disease. Patients underwent phlebotomy a mean of 0.57 +/- 0.01 liter of whole blood; volume was replaced with lactated Ringer's solution. Hematocrit levels decreased from a mean value of 42.9 +/- 0.4 per cent to 33.7 +/- 0.3 per cent. Mean intraoperative blood loss was 1.2 +/- 0.05 liters. Hemodynamic parameters (blood pressure, cardiac output, pulmonary capillary wedge pressure, central venous pressure, oxygen delivery and systemic vascular resistance) remained stable throughout the perioperative and intraoperative time periods. In addition, we evaluated the technical modification of exclusion aneurysmorrhaphy (n = 50) versus open aneurysmorraphy (n = 19) on reduction of intraoperative homologous blood transfusion in these patients. Seventy-two per cent (36 of 50) of patients whose aneurysms were excluded received no homologous blood intraoperatively. Blood loss was decreased in the excluded versus open aneurysmorraphy group, 920 +/- 90 milliliters versus 2,030 +/- 250 milliliters, as were homologous blood transfusion requirements, 175 +/- 35 milliliters versus 570 +/- 119 milliliters. Two patients died (2.9 per cent mortality rate), and there was no increase in morbidity. Surgical treatment of large aortic aneurysms is frequently performed on an urgent basis; thus, provision of autologous blood for this operation in a short period of time may be beneficial. Isovolemic hemodilution performed during the immediate preoperative period can reduce homologous blood requirements and be safely performed without adverse effects on mortality, morbidity and myocardial performance. Exclusion aneurysmorrhaphy may further reduce dependence on homologous blood.

Aorta, Abdominal↗

PubMed1990

Results of infrainguinal bypass for limb salvage in patients with end-stage renal disease.

Limb salvage in patients with end-stage renal disease (ESRD) is complicated by the diffuse, obstructive, calcific arteriopathy that makes anastomotic technique especially critical. Furthermore, decreased resistance to infection and impaired wound healing produced by host-factor deficiencies such as diabetes mellitus, hypoalbuminemia, uremia, and immunosuppression produce additional obstacles to successful limb salvage. This report summarizes our experience with distal arterial bypass procedures in these patients. A total of 32 bypass procedures were performed for limb salvage in 24 patients (17 diabetic) during a period of 5 years. The operative mortality rate was 6%. During the same period, 635 infrainguinal bypass procedures were performed by the in situ technique in patients without ESRD. Primary bypass patency was comparable in both groups at 24 months (92% vs 90%). In the group with ESRD, overall limb salvage was 83% at 2 years. Life-table analysis of bypass patency and limb salvage was thought not to be appropriate in the population with ESRD beyond 2 years because of the increased mortality rate (38%; 9/24) during this interval. It is important that limb salvage was achieved in diabetic patients with ESRD in the presence of extensive foot gangrene or ischemic ulceration. Revascularization should be considered strongly for limb salvage in all patients in this difficult population.

Adult↗

PubMed1990

An animal model for instructing and the study of in situ arterial bypass.

A canine model that used the cephalic vein to bypass from the brachial to the ulnar artery was designed for use in instructing and evaluating surgical technique needed for constructing an in situ arterial bypass. This model was used for instructing vascular residents in the in situ vein bypass technique. The use of this model enabled the resident to become more adept with the instruments for valve incision and construction of small vessel anastomosis. The improvement in the resident's operative technique was reflected by a decrease in the number of technical complications (missed valves, missed arteriovenous fistulas, poorly constructed anastomoses) and improved patency rate.

Animals↗

PubMed1990

Hemodynamic characteristics of failing infrainguinal in situ vein bypass.

The successful follow-up of distal arterial reconstructions for the identification of the failing bypass in the postoperative period hinges on a knowledge of the natural history of flow characteristics in these reconstructions. Over a 4-year period resting and hyperemic bypass flow, fistula flow, conduit diameter, and distal peak systolic velocity of 350 in situ bypasses were measured serially. B-mode ultrasound imaging of the entire bypass was performed to identify specific stenoses. Measurements were performed 5 to 9 days after operation, every 2 months for the first year, and every 6 months thereafter. Distal bypass flow less than 25 ml/min, a ratio of hyperemic/resting distal bypass flow less than 2.5, and vein size less than or equal to 3.0 mm inner diameter all correlated with bypass stenosis (greater than 50%) or occlusion (p less than 0.01). Contrary to previous studies, a distal peak systolic velocity of less than 45 cm/sec did not correlate with bypass stenosis or occlusion. A low distal peak systolic velocity did correlate with bypass stenosis or occlusion in bypasses larger than or equal to 3.5 mm inner diameter (p less than 0.03). However, no combination of these factors was able to accurately predict preocclusive stenosis or occlusion. Distal bypass flow was highest initially but reached a plateau 6 to 12 months after operation. Fistula flow, although very high initially, showed marked decrement with time.

Aged↗

PubMed1990

Remote distal arteriovenous fistula to improve infrapopliteal bypass patency.

The results of the use of prosthetic materials for femorocrural bypass surgery have been less than optimal. The creation of a distal anastomotic arteriovenous fistula to augment blood flow and velocity through the graft is well known. However, it may create turbulence at the anastomosis and steal blood flow away from the distal artery. A canine model was developed to evaluate the effect of fistula size on graft/arterial hemodynamics. In 16 patients we have constructed a distal arteriovenous fistula, which is remote from the distal anastomosis, and we studied the effect of such fistulas on bypass patency and distal arterial hemodynamics. Patients selected for this procedure had multiple previously failed reconstructions and limb-threatening ischemia and did not have usable autogenous vein. Femorotibial bypass graft reconstructions were performed with polytetrafluoroethylene followed by the creation of a side-to-side arteriovenous fistula 5 to 15 cm below the distal anastomosis in the same artery and accompanying veins. We have achieved a 1-year patency of 67% with a 75% limb salvage rate. We also serially measured blood flow and velocity within the bypass, the arteriovenous fistula, and the distal outflow vessel using duplex scanning after surgery. Mean estimated blood flow through the bypass during the immediate postoperative period was 264 ml/min, the arteriovenous fistula was 157 ml/min, and the distal artery was 19 ml/min. Unlike an arteriovenous fistula created at the distal anastomosis, a remote distal arteriovenous fistula not only increases graft blood flow but also augments native arterial blood flow between the distal anastomosis and fistula and thus may improve distal limb perfusion.

Animals↗

PubMed1989

Role of B-mode venous mapping in infrainguinal in situ vein-arterial bypasses.

Two hundred and eighty patients underwent B-mode mapping (B-map) of their saphenous vein over a period of 3 years (1984-1987) before lower limb revascularization. B-map deemed that 229 veins were suitable for bypass, 26 were questionable and 25 were unsuitable. A successful bypass was achieved in 97.8 per cent of the suitable group (all in situ), 85 per cent of the questionable group (in situ and composite vein), and 80 per cent of the unsuitable group (composite vein). At a minimum follow-up period of 1 year the overall patency rate was 95.0 per cent with a revision rate of 15.8 per cent. There was no correlation between revision rate and vein complexity or calf vein diameter. Calf vein diameter greater than 2.5 mm was correlated with a successful bypass (P less than 0.001). It is concluded that B-map is the investigation of choice for saphenous vein assessment before infrainguinal bypass surgery.

Aged↗

PubMed1989

Optimum specimen positioning in the electron microscope using a double-tilt stage.

Optimal imaging of complex structures requires proper alignment relative to the optic axis of the electron microscope. This is especially important for high-voltage and intermediate-voltage microscopes, which form an in-focus image throughout the entire thickness of the object. As a result, structures at different specimen heights form overlapping and confused images that severely curtail the usefulness of these instruments. The work described here provides a generalized, flexible method for optimizing specimen orientation and eliminating or limiting image overlap by means of a commonly used double-tilt stage. Analysis of the motion about the two axes provides accurate tilting for any azimuthal direction whether or not it corresponds to a mechanical axis of the stage. An object can be positioned to minimize image overlap, to record stereopairs for any parallax axis, and to record three-dimensional data sets by the conical collection geometry. Images of muscle paracrystals are shown after tilting about an axis perpendicular to a symmetry direction. The tilted image displays higher-order symmetry, which is altered by changes of one degree. Precision double-tilting for optimizing stereopairs is shown for a desmosome recorded using different parallax axes and pretilts. A tomographic conical data-collection scheme is demonstrated by imaging a microtubule axoneme for a specific cone half-angle and arbitrary azimuthal angles.

Microscopy, Electron↗

PubMed1989

The right retroperitoneal approach for abdominal aortic surgery.

Retroperitoneal exposure of the abdominal aorta is usually performed through a left flank incision. An alternative approach to the abdominal aorta is described utilizing a right flank incision. Indications for the use of the right retroperitoneal approach during surgery for aortic aneurysms include right renal artery stenosis, right iliac artery aneurysm, need for simultaneous cholecystectomy, multiple or recent intraabdominal procedures, and sigmoid colostomy. A series of 17 patients is presented to illustrate the utility of this approach. There was one operative death in an emergent patient; the cause of death was not related to the method of aortic exposure. The remaining patients recovered quickly. The anatomic advantages and limitations of this exposure are discussed. We believe that retroperitoneal aortic exposure is superior to midline transperitoneal exposure. Aortic exposure utilizing a right retroperitoneal approach is a useful option in the surgical armamentarium.

Aorta, Abdominal↗

PubMed1989

Flow/velocity characteristics of arterial bypass stenoses.

In the carotid system with relatively constant blood flow, peak systolic velocity within a stenosis (PSVST) can characterize the degree of hemodynamic stenosis. We have studied flow/velocity characteristics in an in vitro model of stenosis within conduits of varying diameters in an attempt to quantify the degree of stenosis from flow/velocity profiles in peripheral vein bypasses. A Harvard pulsatile flow pump (70 BPM) pumped human blood (HCT, 35-45%) through thin-walled polytetrafluoroethylene (3-6 mm in i.d.) into a variable peripheral resistance maintaining a constant mean blood pressure of 80 mm Hg over a flow range of 0-500 ml/min. A Diasonics DRF400 duplex scanner with a 10-MHz imager and 4.5-MHz Doppler probe was used to image and Doppler the conduits and measure flow through them. Validation of Doppler flow measurements (DF) was performed comparing them with flow measured (MF) by timed collection. PSVST within and pressure drop across a 50% stenosis was measured for each of the conduit's sizes over a range of 0-500 ml/min MF. The results show a good correlation between DF and MF (r = 0.99, P less than 0.001) for the whole range of internal diameters. In each 50% stenosed conduit, PSVST correlated well with MF (r = 0.95, P less than 0.001). Curves were constructed of MF vs PSVST for each 50% stenosed conduit. We conclude that measurement of volumetric flow, conduit diameter, and peak systolic velocity within a vein bypass can objectively predict bypass stenoses of 50% or greater.

Arterial Occlusive Diseases↗

PubMed1989

Comparative analysis of retroperitoneal and transperitoneal aortic replacement for aneurysm.

Transabdominal aortic replacement is the most widely accepted surgical approach in the treatment of infrarenal abdominal aortic aneurysms (AAA) with an enviable mortality rate of 2 to 5 per cent. This approach, however, is attended by significant intraoperative loss of fluid and subsequent translocation as well as impaired postoperative pulmonary function and ileus. Although the retroperitoneal exposure of the aorta was used for the first repair of an AAA by Dubost and has been championed more recently by others, it has not been widely accepted. Experience suggests, however, that the exposure is as good and that postoperative morbidity is significantly less than that with the transperitoneal approach. In the past five years, we have surgically treated 299 AAA, 106 by the transabdominal route and 193 by the extended retroperitoneal approach. In 133 of the 193 patients upon whom the retroperitoneal approach was used, the aneurysm was left intact after division of the infrarenal aorta for an end to end proximal anastomosis of an aortoaortic to iliac to femoral bypass. There has been a significant reduction in the intraoperative replacement of fluid and blood, in postoperative respiratory support, in length of time in the intensive care unit and in occurrence of postoperative ileus when compared with the transabdominal endoaneurysmorrhaphy approach. Furthermore, the exposure, particularly upon the obese patient, is superior. Findings from this experience using the retroperitoneal approach for repair of AAA indicate that it results in less over-all physiologic disturbance of the patient.

Aged↗