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Biomedical subjects

A K Chin

Publications and source records attributed to A K Chin.

17 recordsLinked to original sources
PubMed1998

Endoscopic femoral-popliteal/distal bypass grafting: a preliminary report.

BACKGROUND: Patients requiring limb bypass or coronary artery bypass procedures frequently develop vein harvest-associated complications. Minimally invasive surgical techniques that can be employed during dissection of the greater saphenous vein could potentially reduce the significant incisional morbidity concomitant with this procedure. STUDY DESIGN: An endoscopic saphenous vein balloon dissector was developed and previously tested in the animal model. It was applied to a series of 16 leg bypass patients to dissect totally endoscopically the greater saphenous vein for either translocated or in situ procedures. The clinical course of these 16 patients was compared with the most recent 16 consecutive standard open saphenous vein bypass patients of similar age, disease, and risk factors. RESULTS: No venous conduit injuries occurred with the endoscopic dissection technique, and only one minor wound seroma resulted in the harvest tunnel, requiring simple aspiration. The length of stay averaged 3.8 days, but the trend was downward to 1.8 days for the last 8 consecutive endoscopically dissected patients. In comparison, there were five major wound complications in the 16 open saphenous vein bypass patients with an average length of stay of 6.2 days. CONCLUSIONS: Total endoscopic saphenous vein dissection for either translocated or in situ leg bypass patients can be performed atraumatically for both the patient and the venous conduit. Wound/incisional complications are decreased, and length of stay appears to be reduced. Minimally invasive, endoscopic saphenous vein harvest may be beneficial for both leg bypass patients and coronary artery bypass patients.

Aged↗
PubMed1995

Experimental laparoscopic aortobifemoral bypass.

The goal of the present study is to develop a technique for laparoscopic aortobifemoral bypass. Piglets weighing between 60 and 78 kg were anesthetized with halothane. The lateral retroperitoneal approach was preferred to the more familiar anterior transperitoneal approach and was successfully completed in 19 piglets. The piglets were placed in the right lateral decubitus position. The first port (2 cm) was inserted halfway between the tip of the 12th rib and the iliac crest. Four other trocars were placed in the retroperitoneum after balloon inflation had allowed creation of a space which permitted visualization of the aorta from the left renal artery down to the aorto-iliac junction. After evacuation of the retropneumoperitoneum, the cavity was maintained using an abdominal lift device and a retractor. Using this approach, we performed four aorto-bifemoral bypasses (end-to-end aortic anastomosis) after conventional intravenous heparinization (100 IU/kg) in less than 4 h. Blood loss did not exceed 250 ml and the hematocrit remained stable. Postmortem evaluation of the grafts revealed they were positioned as in a conventional bypass, their limbs having followed in the created retroperitoneal tunnels along the path of the native arteries. No mortality occurred before sacrifice of the animals. We believe that this first performed series of totally retroperitoneal laparoscopic aortobifemoral bypasses in the porcine model is useful in preparation for human application due to the anatomical similarities in the periaortic region.

Anastomosis, Surgical↗
PubMed1994

Novel technique and instrumentation for laparoscopic application of hemostatic clips.

A novel device for applying hemostatic clips in laparoscopic surgery incorporates a distal hook into a multiple-firing titanium clip applier. The hook may be used for blunt dissection of tissue, and to displace and control ducts and vessels during clip application. A single instrument may be used to achieve hemostasis in areas that are difficult to reach, and past pointing problems encountered with straight on clip appliers are alleviated. Comparative testing of the holding force of the curved clips used with this device versus the straight clips used in conventional multiple-clip appliers demonstrated a higher mean pull-off force of 0.473 lbs versus 0.33 lbs. Clinical application of the device in laparoscopic procedures including cholecystectomy, vaginal hysterectomy, Nissen fundoplication, vagotomy, varicocelectomy, and lymphadenectomy show the utility of the hook clip applier.

Animals↗
PubMed1994

Gasless laparoscopy using a planar lifting technique.

In clinical use, the mechanical lifting technique has demonstrated the ability to displace the abdominal wall and create a useful cavity for visualization and surgical manipulation. By forming a planar ceiling, as opposed to the domed ceiling of conventional pneumoperitoneum, the abdominal organs are brought into closer proximity of the surgeon. Instrument length may be shortened, imparting greater surgical control. Without the necessity for gas sealing, entry portals are simplified. Conventional instruments (right angle clamps) may be introduced through the fan retractor insertion sites or by way of separate stab incisions. The planar lifting technique has the potential for simplifying laparoscopy and restoring instrument control to the operating surgeon.

Abdominal Muscles↗
PubMed1993

Mechanical peritoneal retraction as a replacement for carbon dioxide pneumoperitoneum.

A fan retractor and a mechanical lifting arm were developed to achieve planar displacement of the anterior abdominal wall for gasless laparoscopic procedures. The technique permits the use of conventional open surgical instruments as well as laparoscopic tools through minilaparotomy incisions. It also potentially addresses the technical constraints imposed by pneumoperitoneum, and physiologic concerns regarding carbon dioxide insufflation. Gynecologic, general surgical, and trauma procedures were performed in 104 patients, with successful completion of 86.5%. Continued application is necessary to delineate the full range of benefits of laparoscopy without insufflation.

Equipment Design↗
PubMed1989

Combined thrombectomy and dilation for the treatment of acute lower extremity arterial thrombosis.

Our experience with combined balloon catheter thrombectomy and balloon dilation for the treatment of acute thrombosis is reported. Eighteen patients underwent the combined procedures between 1981 and 1988. Primary thrombectomy and balloon dilation were performed in 14 patients, and additional reconstruction was performed in three patients. The superficial femoral artery was the site of thrombectomy and dilation in 13 patients, and the external iliac artery was the site in the remaining five patients. Successful dilation was accomplished in all patients, with stenotic sites reduced below 30% by angiography, and ankle/brachial indexes increased by 0.15 or more. No operative deaths or complications occurred. Follow-up of superficial femoral artery dilations showed a 90% patency rate continued out to 4 years and a 40% patency rate at 5 years. Combined thrombectomy and interventional catheter therapy may aid in the care of this difficult to treat vascular patient group.

Acute Disease↗
PubMed1988

An improved technique for the internal mammary artery coronary bypass graft procedure.

An improved technique for internal mammary artery graft preparation is described. Following cautery dissection of the internal mammary artery (IMA) pedicle, the pedicle investing fascia is incised to the adventitial level along a single plane. This incision allows the tissue around the internal mammary artery to fall away and severs the muscular constrictions that often surround the internal mammary artery. Balloon calibration is performed to identify remaining constrictions and to relieve internal mammary artery spasm. A shear force limiting gauge insures that the exerted balloon force remains below the level demonstrated to cause intimal damage during electron microscopic studies. This technique allows full internal mammary artery distention without the devascularizing effects of full skeletonization. Distention of the distal internal mammary artery provides an enlarged hood to facilitate suture placement. Elongation of the internal mammary artery during balloon calibration aids in the performance of sequential grafts. This technique has been applied to 793 patients over the past five years. Postcalibration flow rates increased 3- to 18-fold over precalibration flow rates. Two early occlusions occurred during this series, one due to endothelial strippage prior to the development and use of the shear force limiting gauge. Follow-up showed 93.3% of patients to be asymptomatic. This combination of fascial incision and balloon calibration appears to offer safe technical and functional improvements to the performance of the internal mammary artery graft.

California↗
PubMed1988

The effect of valvulotomy on the flow rate through the saphenous vein graft: clinical implications.

Potential differences in flow rates between reversed and in situ saphenous vein bypass grafts were evaluated. One hundred ten greater saphenous vein segments containing isolated valves were examined with fiber-optic angioscopy during pulsatile and nonpulsatile flow. Valve competency was determined, and the degree of luminal obstruction caused by the valve during reversed flow was calculated with caliper measurements of the video image. Flow measurements were obtained before and after valvulotomy, in reversed and nonreversed vein orientations. Increased flow rates occurred during pulsatile irrigation only, after valvulotomy in vein segments with diameters less than 2.5 mm (p less than 0.001, Bonferroni t test). In these small-diameter vein segments, the flow rate in reversed valve-intact vein was 94.4 +/- 28.9 ml/min (mean +/- 1 standard deviation), the flow rate in reversed valve-disrupted vein was 136.4 +/- 36.5 ml/min, and the flow rate in nonreversed valve-disrupted vein was 137.8 +/- 31.3 ml/min. In 22 vein segments, luminal obstruction caused by the intact valve was measured angioscopically. A small valve orifice was found to be related to a large increase in flow rate after valvulotomy (p less than 0.02, least-squares regression). In addition, veins with diameters less than 2.5 mm have significantly smaller valve orifices compared with veins with diameters greater than 2.5 mm. These results present important clinical implications as the number of distal extremity reconstructions increases.

Blood Flow Velocity↗
PubMed1988

Balloon embolectomy catheter shear force gauge.

The shear force gauge is a device that will allow surgeons to develop a sense for the amount of shear force exerted on the arterial endothelium during balloon embolectomy. As a teaching device, hopefully it will decrease the number of shear force related complications connected to the use of the balloon embolectomy catheter.

Arteries↗
PubMed1987

Management of arterial emboli. Gleanings from 20 years of experience.

Arterial embolism is usually caused by cardiac disease, and atherosclerotic coronary vascular disease is the primary precursor. Other cardiac states, as well as several uncommon causes, are part of the etiologic spectrum. The earliest signs are pain, paresthesias, pallor, and pulselessness. Severe ischemia is indicated by paralysis, a late feature. Arterial embolism and acute thrombosis can be difficult to distinguish, and deep venous thrombosis may also be suspected in the differential diagnosis. To restore arterial flow, anticoagulation treatment with heparin (Lipo-Hepin, Liquaemin) is given and surgical embolectomy is performed. Heparin infusion is continued until the patient is ambulatory, and then warfarin sodium (Coumadin, Panwarfin) is given over the long term. Fibrinolysis has also been used to treat acute arterial occlusion. Complications of embolism must be carefully guarded against, and additional procedures are sometimes necessary.

Arterial Occlusive Diseases↗
PubMed1985

Shear force in angioplasty: its relation to catheter design and function.

The inability to successfully position angioplasty catheters and the occurrence of complications during angioplasty procedures can, in part, be related to the shear forces generated during catheter introduction. Shear forces are the axial contact forces that the catheter system exerts on the inner arterial surfaces during advancement. The shear forces exerted by three different catheter designs (coaxial dilator, coaxial balloon, and linear extrusion) were measured in normal and atherosclerotic arteries; in modeled stenoses of variable severity, length, and compliance; and in modeled vessel angulations. The results with modeled vessels show that the linear extrusion catheter reduces the level of shear forces, particularly in narrow, long, noncompliant stenoses and in tortuous vessels. The stenotic artery results also show that the linear extrusion catheter minimizes these forces in tight lesions. The relative differences in forces are explained by the mechanism of action for each catheter. The reported occurrences of technical difficulties, complications, and long-term patency rates are then interpreted on the basis of the relative differences in measured shear forces. The results of this study combined with preliminary clinical data indicate that linear extrusion should facilitate placement and reduce associated complications.

Angioplasty, Balloon↗
PubMed1984

Transluminal angioplasty: a mechanical-pathophysiological correlation of its physical mechanisms.

We quantitatively determined the relative contribution of various factors leading to arterial lumen enlargement during transluminal angioplasty. Mechanical tests were conducted on both normal and atherosclerotic artery necropsy specimens. In our range of dilating pressures (0-3.4 atm or 0-50 lb/in2), content extrusion of fluid from the plaque accounted for 6-12% of the overall lumen area increase, while compaction of the plaque accounted for only 1-1.5%. The majority of the increase, 86.8-93%, was due to plaque and arterial wall disruption. The mechanism of disruption began with shearing of the plaque from the underlying artery at relatively low dilating pressures and continued with longitudinal tearing and stretching of the arterial wall at higher pressures. Diseased arteries dilated significantly more than nondiseased arteries at dilating pressures greater than or equal to 1.36 atm or 20 lb/in2 (P less than .05). In the range of stenoses that were tested (10-50%), the mean dilating pressure required to increase the lumen cross-sectional area by 50% was approximately 1.5 atm or 22 lb/in2.

Angioplasty, Balloon↗
PubMed1984

A physical measurement of the mechanisms of transluminal angioplasty.

We report a quantitative determination of the relative contribution of various factors leading to arterial lumen enlargement during transluminal angioplasty. Mechanical tests were conducted on both normal and atherosclerotic artery necropsy specimens. In the range of dilating pressures tested (0 to 3.4 atm or 0 to 50 lb/in2), content extrusion of fluid from the plaque accounted for 6% to 12% of the overall lumen area increase, while compaction of the plaque accounted for only 1% to 1.5%. Most of the increase (86.8% to 93%) was due to plaque and arterial wall disruption. The mechanism of disruption involved shearing of the plaque from the underlying artery at relatively low dilating pressures, followed by longitudinal tearing in the arterial wall at higher pressures. Diseased arteries were observed to dilate significantly more than nondiseased arteries at dilating pressures greater than or equal to 1.36 atm or 20 lb/in2 (P less than 0.05). In the range of stenoses tested (10% to 50% based on diameter reduction), the mean dilating pressure required to increase the lumen cross-sectional area by 50% was approximately 1.5 atm or 22 lb/in2. Based on these studies, we conclude that balloon dilatation results arise mainly from plaque and arterial wall disruption.

Angioplasty, Balloon↗
PubMedDate not supplied

Long-term results of intraoperative balloon dilatation.

A review was conducted of 61 patients who underwent intraoperative balloon dilatation over the past five years. Of the 62 dilatations in this patient group, 80% were performed in conjunction with a reconstructive procedure, and 20% were performed as a primary procedure. Dilatations were performed with the linear extrusion balloon catheter. A 94% rate of followup was achieved, with a mean followup of 16.3 months (range 1-60 months). Life table analysis reveals a 95% initial success rate decreasing to an 81% patency rate by the end of the fifth year for iliac dilatations, a 97% initial and 58% five-year patency rate for superficial femoral dilatations, and an 86% initial and 37% five-year patency rate for popliteal dilatations. 21.3% of the patients died during the followup period. No deaths occurred as a result of intraoperative angioplasty. One arterial rupture occurred, requiring a bypass graft at the same surgery. We conclude that intraoperative balloon dilatation in an adjunctive setting may offer clinical benefits to vascular patients while requiring little additional operative time.

Actuarial Analysis↗