Biomedical subjects

B B Chang

Publications and source records attributed to B B Chang.

106 records · Page 6Linked to original sources

PubMed1988

Selective use of retroperitoneal aortic exposure in the emergency treatment of ruptured and symptomatic abdominal aortic aneurysms.

Emergency surgery is the only effective treatment of ruptured abdominal aortic aneurysms, even though morbidity and mortality rates remain high. We have studied the feasibility of left retroperitoneal aortic exposure in these cases in an effort to reduce postoperative complications. Over a 33 month period, 29 patients underwent emergency surgery for either a ruptured or symptomatic infrarenal abdominal aortic aneurysm. Of 13 patients with ruptured aneurysms, 4 underwent repair through a midline transperitoneal approach (3 deaths) whereas the remaining 9 were repaired through the retroperitoneal exposure (1 death). Supraceliac aortic clamping through the same incision prior to aneurysm exposure maintained hemodynamic integrity. The remaining 16 patients with symptomatic aneurysms were all treated through the retroperitoneal exposure (3 deaths). In the retroperitoneal groups, the cause of death was cardiac in two patients, hypertensive stroke in one, and necrotizing pancreatitis in one. Morbidity consisted of prolonged intubation, respiratory distress syndrome, and thrombophlebitis in one patient each and acute tubular necrosis in two patients. We believe that the left retroperitoneal approach is a useful option in the emergent treatment of abdominal aortic aneurysms.

Aged↗

PubMed1988

Durability of the tibial artery bypass in diabetic patients.

Infrapopliteal bypass in diabetic patients has been associated with lower rates of patency and limb salvage than in nondiabetic patients. We prospectively compared the patency and limb salvage rates of in situ tibial artery bypass in diabetic and nondiabetic patients. Of 681 in situ bypasses performed for limb salvage over a 7 year period, 387 (57 percent) were carried out in diabetic patients and 294 (43 percent), in nondiabetic patients. Indications for operation most commonly included gangrene or ulceration (74 percent of the diabetic group and 49 percent of the nondiabetic group). Otherwise, the two patient groups were similar. Cumulative patency rates at 1 and 5 years were similar (91 and 74 percent for diabetic patients and 90 and 76 percent for nondiabetic patients, respectively). Limb salvage rates were also not significantly different (96 and 86 percent at 1 and 5 years, respectively, for diabetic patients and 99 and 94 percent, respectively for nondiabetic patients). Despite the unfavorable pattern of atherosclerosis in diabetic patients, the results of tibial arterial reconstructions showed patency and limb salvage rates similar to those seen in nondiabetic patients.

Amputation, Surgical↗

PubMed1988

Resurrection of the in situ saphenous vein bypass. 1000 cases later.

Distal bypasses for the terminal stages of atherosclerotic occlusive disease manifest by chronic limb-threatening ischemia are among the most challenging arterial reconstructive procedures of surgeons today. The length and low flow rates of distal bypasses often exceed the functional limits of synthetic and even free vein grafts. However, the saphenous vein, when used in situ, provides a unique, viable, physiologically active, and hence antithrombogenic endothelial flow surface that is ideally suited for such bypasses. This paper presents the experience of the Albany Medical Center Hospital with the first 1000 in situ bypasses performed by the valve incision method over a 12-year period. Limb-threatening ischemia was the most common indication for surgery (91%). An in situ bypass was attempted in over 95% of unselected limbs and were completed in situ and in toto in 94%. 66% of the bypasses were carried out to the infrapopliteal level, and in more than 50% of the limbs, the distal vein diameter was less than 3.5 mm. The 30-day patency rate was 95%, and the cumulative patency rates, by life table analysis at 1, 2, 3, 4, and 5 years, were 90%, 86%, 84%, 80%, and 76%, respectively. The vein diameter, specific outflow vessel, level of distal anastomosis (length of bypass), inguinal inflow source used, and instrumental evolution had no significant effect on immediate or long-term bypass performance.

Arterial Occlusive Diseases↗

PubMed1987

The influence of anesthetic choice on carotid endarterectomy outcome.

This study compared the technique of general and regional cervical block anesthesia for carotid endarterectomy. Three hundred sixty-eight patients undergoing 399 carotid endarterectomies were administered one of these alternative anesthetics as selected preoperatively by each patient and his or her physician. In 242 cases general anesthesia was used. The other 157 cases were done under regional cervical block anesthesia. Perioperative mortality was 1.0%. Nonfatal strokes occurred in 1.25%. There were significantly more strokes in the general anesthesia group. Perioperative blood pressure was unstable for a significantly longer period of time after general anesthesia (mean, 24.6 hours) as compared with regional cervical block anesthesia (mean, 2.1 hours). Furthermore, vasoactive drugs were required for significantly longer periods of time in the general anesthesia group.

Adult↗

PubMed1986

Transcutaneous flow measurements in in-situ bypasses: an assessment of duplex scanning.

Measurement of laminar flow using an ultrasound scanner was shown to have a high degree of correlation with quantified timed flows (r = 0.98, p less than or equal to .001). Sixty-one in-situ bypasses had flow assessed both proximally and distally. Mean fistula flow (proximal-distal flows) for time periods 1-8 weeks, 3 to 8, and 9+ months were 108, 85, and 16mls respectively. Distal bypass flow remained constant despite a significant decrease in fistula flow between the later time periods (p less than or equal to .001) (unpaired t-test). There was no evidence from the study that proximal flow through fistulas of varying resistances adversely affected the distal bypass flow.

Arteriovenous Fistula↗

PubMed1986

Perioperative hypertension in patients undergoing carotid endarterectomy: shorter duration under regional block anesthesia.

Two alternative anesthetic techniques for use during carotid endarterectomy were studied in a series of 424 procedures. A total of 248 were performed in patients under general anesthesia and 176 patients received regional block anesthesia. Perioperative instability of blood pressure was noted in 108 patients. Hypertension was noted in 17.7% of those under general anesthesia vs 20.5% of those under regional block anesthesia. Intravenous vasodilator agents were used for 19.62 hr (+/- 4.33) in the general anesthesia group vs 1.4 hr (+/- 0.44) in the regional block anesthesia group (p less than .02). Perioperative hypertension correlated best with uncontrolled preoperative hypertension. Under regional block anesthesia the incidence of shunting was 4.5%. The 1 month operative mortality for the entire carotid series was 1.2% (5/424). There were three stroke-related deaths. In addition, two nonfatal major strokes and two minor strokes occurred in patients who received general anesthesia vs one nonfatal major stroke in a patient who received regional block anesthesia.

Aged↗

PubMed1986

The anatomy of the greater saphenous venous system.

To define surgical anatomy, a prospective study of the greater saphenous venous system in 385 instances in 331 patients was carried out with the use of prebypass phlebography (either pre- or intraoperative). The phlebographic interpretations were confirmed during the operative procedures and from the completion angiogram. These details were recorded and analyzed by a specific computer program. These data consisted of a number of superficial branches, perforators, the identification of valve leaflets, sinuses, and the size and position of the main venous trunk both in the thigh and in the calf. The study showed that a single trunk was present in the thigh in 65% of patients and in the calf in 45%. The remainder were variants of double systems. In two thirds of patients who had complete double systems, the larger system was used for in situ bypass but the rest required the use of parts of both systems. Phlebography was accurate in the depiction of the anatomic variations (93%), double systems, cross connections, and perforator branches (87%). However, the number of competent valves could not be accurately determined (accuracy, 68%). The diameter of the vein was frequently underestimated (in 80% by 1.1 +/- 0.4 mm) and hence could not be used as an index of vein adequacy. After phlebography, four patients had transient rises in serum creatinine levels and one had an iatrogenic thrombosis of a distal segment. This study suggests that the precise anatomy of the greater saphenous venous system should be determined preoperatively by phlebography since this information is valuable for proper surgical planning before vein is used as a graft or for in situ bypass in the lower extremity.

Adult↗

PubMed1981

Design and operation of a differentially pumped environmental chamber for the HVEM.

A differentially pumped environmental chamber, or DIFPEC, has been developed for the AEI EM7 1.2 MV HVEM. The chamber is suitable for imaging and diffraction studies and is capable of operation at pressures approaching one atmosphere. Any mixture of gases can be used including water vapor supplied from an internal reservoir. Correct operation is demonstrated by measurements of temperature, pressure, and water consumption. High resolution (0.2 nm) diffraction patterns were recorded from unfixed, unstained, fully hydrated catalase crystals. This is good functional test of DIFPEC operation and specimen preparation because catalase disorders irreversibly of exposed to less than 95% relative humidity. High- and low-angle diffraction patterns were recorded from unfixed, unstained, fully hydrated rat hemoglobin crystals. All patterns were recorded using 10-4 C/cm2. Whole cell mounts prepared in different ways were imaged and show that 5.3 kPa of nitrogen gas has no detrimental effect on image contrast or resolution. The column vacuum and differentially pumped volume pressure were measured for a number of pumping configuration, as well as for several gases and pressures in the specimen volume. The pressure in the high vacuum portion of the objective lens gap is conductance-limited when the DIFPEC is in place.

Animals↗

PubMedDate not supplied

Decreased morbidity associated with retroperitoneal exclusion treatment for abdominal aortic aneurysm.

A prospective randomized study has been carried out to compare the retroperitoneal (RP) and the transperitoneal (TP) approaches to infrarenal abdominal aortic aneurysms (AAA). From November 1988 to July 1989, 27 patients were randomized to one or the other group. Twelve patients underwent TP resection of their AAA; 11 of these were performed using the open aneurysmorrhaphy technique. The RP approach was used in 15 patients, 12 of whom had the exclusion technique performed. Enteral feeding was resumed on the second postoperative day in the RP group compared to the fourth postoperative day in the TP group; the difference was statistically significant (p less than 0.02). Statistically significant differences were also present in the estimated blood loss (516 cc in the RP group versus 1127 cc in the TP group) in the blood transfusion requirement (p less than 0.05). This prospective randomized study comparing TP and RP approaches to AAA showed that the RPE approach had less blood loss, less transfusion requirement, and earlier resumption of enteral feeding than the TP approach. We feel the RPE technique is safe and efficient in the treatment of infrarenal abdominal aortic aneurysm.

Aged↗

PubMedDate not supplied

Carotid bifurcationplasty: an alternative to patching.

Patching of carotid endarterectomies has been advocated as a means of both facilitating secure closure and minimizing recurrent stenosis. Most vascular surgeons occasionally, if not always, patch selected carotid arteries. However, patching requires the surgeon to utilize either prosthetic material (Dacron or PTFE), which is relatively thrombogenic, or autogenous vein, which requires a second operative field and available saphenous vein at the ankle. Bifurcationplasty, otherwise known as bifurcation advancement, has been used as an alternative to patching at our institution over the past four years. This technique, which involves the use of the opened, endarterectomized external carotid artery as an autogenous in-continuity patch for the internal carotid artery, obviates the need for prosthetic materials and saphenous vein alike. This procedure has been performed 30 times over a 4-year period (1987-91). During this time, 280 carotid endarterectomies were performed. A vein patch or Dacron was used in four cases early in this series. Bifurcationplasty was also the procedure of choice for repeat carotid endarterectomy, and was performed in five cases of recurrent stenosis after direct closure. In a follow-up period averaging 22 months (range 1-48), there were no instances of symptomatic restenosis. We feel that bifurcationplasty is an easily performed autogenous alternative to conventional patch closure of the carotid artery.

Carotid Arteries↗

PubMedDate not supplied

Left retroperitoneal exposure for distal mesenteric artery repair.

Distal disease in the mesenteric arteries has usually been repaired transabdominally since it is believed that only the proximal centimeter of each vessel is accessible through the retroperitoneum. We treated five patients with chronic visceral ischemia and lesions extending beyond the orifice using a retroperitoneal approach. Exposure was obtained with a left flank incision through the tenth interspace. The left crus of the diaphragm was divided in order to control the supraceliac aorta. The mesenteric vessels were identified and dissected until their entrance into the peritoneum. There were no difficulties in exposing the superior mesenteric artery (SMA) as it coursed under the pancreas and over the duodenum for an approximate length of 5 to 10 cm. The uncinate process of the pancreas was not a limiting factor for exposure of the SMA in this region and further distal exposure could be obtained by incising the peritoneum. The trifurcation of the celiac artery and the splenic artery were accessible through this exposure; however, only the first centimeter of the hepatic and gastric branches could be reached. Revascularization was performed with endarterectomy (2 patients) and bypass (3 patients). Bowel viability was assessed at the conclusion of the procedure by incising the peritoneum. There were no complications from this exposure and no patient required reoperation for ischemic bowel. We conclude that the left retroperitoneal approach is not only acceptable for orifice lesions but is also applicable for distal disease.

Blood Vessel Prosthesis↗

PubMedDate not supplied

In situ bypass hemodynamics. The effect of residual A-V fistulae.

The effect of arteriovenous fistulae on in situ saphenous vein bypass hemodynamics and patency rates has been of great concern to some. It is our practice to ligate only those fistulae which conduct enough dye upon completion angiography to visualize the deep femoral venous system. We have prospectively studied 216 such bypasses using duplex ultrasound scanning to assess overall hemodynamic function over periods from 1 to 156 months postoperatively. Volumetric blood flow was measured in proximal and distal portions of the bypass choosing a region of uniform diameter with laminar flow. Mean fistula flow was derived by subtracting distal bypass flow from proximal bypass flow. Distal flow decreased significantly (p less than 0.01 paired t-test) from 68 +/- 4.6 ml/min (mean +/- SEM) at 2 months postoperatively to 51 +/- 4.8 ml/min at 12 months postoperatively. There was an overall decrease in fistula flow from 256 +/- 26.9 ml/min at 2 months to 86 +/- 22.6 ml/min at 12 months. In 14 of the 216 bypasses (6.5%), arteriovenous fistulae were ligated during the first postoperative year. This was necessitated by persistent increased fistula flow with or without edema and indication from PVR or segmental pressure of decreased resting flow or pressure. Following fistula ligation, fistula flow decreased and distal bypass flow improved. Within this select group of patients with reduced flow capacity, i.e., a proximal stenosis or small vein size, high fistula flow is poorly tolerated with a significant redistribution of flow resulting in reduced distal perfusion. However, for the majority of patients (95%), fistula flow does not deleteriously affect distal bypass flow.

Arteriovenous Shunt, Surgical↗

PubMedDate not supplied

Comparison between selective distal splenorenal shunt and small diameter H-graft portosystemic shunt.

Although most commonly performed portal decompressive procedures control bleeding effectively, postoperative morbidity and mortality remains a serious problem in these patients. Both distal splenorenal shunts (DSRS) and small-diameter portacaval H-grafts (PCHG) are reported to produce decreased rates of postoperative encephalopathy. We prospectively evaluated 69 patients in whom 27 PCHG and 45 DSRS were performed over a seven-year interval. There were no significant preoperative differences between these groups. Operative mortality was 12.9% overall. DSRS was associated with decreased intraoperative blood transfusions and operative time. Postoperatively, DSRS was associated with significantly less encephalopathy, other postoperative complications, and ascites. Recurrent variceal bleeding was seen in three patients treated with PCHG and two patients with DSRS. We conclude that both DSRS and PCHG are effective in preventing recurrent variceal bleeding, but DSRS remains our procedure of choice because of its decreased rates of postoperative complications.

Blood Vessel Prosthesis↗

PubMedDate not supplied

Intra-operative and post-operative flow in the in-situ saphenous vein bypass.

We have attempted to further define the hemodynamic properties of the arterialized in-situ saphenous vein. The natural taper of the vein and the presence of arteriovenous fistulas are two unique factors associated with this conduit. Utilizing intra-operative electromagnetic flowmeter (EF) measurements and post-operative duplex ultrasound scanning (DUS), we have studied the natural history of these conduits from the time of their arterialization. The EF mean arterial blood flow in 71 in-situ bypasses was 100.8 cc/ml, range 25-200. No significant correlation was found between these measurements and angiographic runoff, vein diameter, pre- or post-operative Ankle/Brachial Index (ABI) and site of distal anastomosis. Three immediate failures requiring revisions were not predicted by EF flow measurements. Using the unique combination of Doppler ultrasound measurement and real time imaging, afforded by the DUS, fistula flow was determined. These studies showed that terminal bypass segment blood flow is not significantly affected by cutaneous fistula interruption. We found that duplex ultrasound scanning is a useful tool ideally suited to the study of the arterialized saphenous vein in-situ. One of its main advantages is the ability to accurately localize the site and hemodynamic significance of any arteriovenous fistulas.

Angiography↗

PubMedDate not supplied

Evaluation of fiberoptic dermofluorometry as a means of clinically assessing tissue perfusion.

Fiberoptic dermofluorometry (FDF) transcutaneously measures fluorescence, following an intravenous injection of sodium fluorescein (NaFl), which is transmitted along a fiberoptic bundle to a photomultiplier tube and converted into dermofluorescence units (DFU). In five normal subjects studied, the plasma concentration of NaFl peaked at 5-15 minutes before decaying with first order kinetics and corresponding dermofluorescence (DF) rose to a peak between 10-20 minutes before decaying. Peak DF in the head and neck was significantly higher (P less than .001) compared to other skin sites which were similar. Application to patients (n = 16) undergoing successful lower limb revascularization showed a significant (P less than 0.01) improvement in perfusion at the foot level only. The reproducibility of FDF was poor when studied on the control limbs. We conclude that FDF does not, at present, constitute a valid measure of skin perfusion.

Adult↗

PubMedDate not supplied

Extraperitoneal aortic bypass with exclusion of the intact infra-renal aortic aneurysm: the in-situ management of aortic aneurysms. A preliminary report.

Transabdominal aortic aneurysmorraphy with graft replacement is the generally accepted and most widely applied surgical approach in the treatment of infra-renal abdominal aortic aneurysm with a mortality rate of 2-5%. The alternative, retroperitoneal exposure of the aorta, although utilized for the first reported repair of an AAA by Dubost and championed by Rob, Stipa and Shaw, Helsby and Moosa and more recently by Williams et al., offers superior exposure and decreased post-operative morbidity. Despite these advantages, it is not commonly used by most vascular surgeons for the surgical management of aortic aneurysms. We have treated 35 patients using an extended retroperitoneal approach in which the aneurysm was treated by division of the infra-renal aorta, an end-to-end proximal anastomosis with an aortic bypass, and over-sewing of the aneurysm. In this group of patients, we found less post-operative physiological disturbances and a reduced requirement for blood transfusion. These data suggest that this method of retroperitoneal exclusion and bypass is generally applicable and is of particular value in the obese and/or the higher risk, medically disadvantaged patient.

Aged↗