Biomedical subjects

S M Shimi

Publications and source records attributed to S M Shimi.

At least 19 recordsLinked to original sources

PubMed2006

Free radical production in the esophago-gastro-duodenal mucosa in response to acid and bile.

Several studies have demonstrated the role of free radicals in causing esophagus-gastro-duodenal mucosal injury. The present study has been designed to investigate: whether acid, bile salts and a combination of bile + acid could determine the production of O2-derived free radicals by oesophageal, gastric and duodenal mucosa; which agent is capable of producing more free radicals and if O2-derived free radicals production depends on the duration of contact with acid, bile salts and their combination. Wistar rats' gastro-intestinal mucosa were perfused with bile, acid and a combination of bile + acid at pH4 and pH2 for 1 hour and 2 hours. Free radical production (FRP) was assessed by chemoluminescence. After 1 hour, the increase in FRP in comparison with control reached statistical significance (P < 0.05) at all tested pH levels in the duodenum, at pH1, 2 and 3 in the esophagus, and at pH1 in the stomach. Comparing different segments, both the esophagus and duodenum behaved similarly, producing more free radicals than the stomach at all pH values. However, this difference reached statistical significance at pH1 and 2 only. In comparison to control, FRP was increased by bile (pH7) infusion after 1 and 2 hours. There was increased FRP in all segments after the infusion of bile at pH2 and 4 in comparison to control. Infusion of bile at pH2 stimulates more FRP than infusion of bile at pH4 in all segments. This increased FRP reaches statistical significance in the esophagus after 2 hours of infusion, in the stomach after 1 and 2 hours of infusion, but in the duodenum it does not reach statistical significance. Acid, bile and bile + acid at pH2 and 4 can cause free radical production in esophageal, gastric and duodenal mucosa. Their role in producing free radicals is different according to the segment and the chemical composition of the solution.

Animals↗

PubMed2005

Skin wound closure with a novel shape-memory alloy fixator.

BACKGROUND: Previously, we have described novel, thermally deployable tissue fixators based on the shape-memory properties of nickel titanium. The present study reports on the in vivo wound closure with these fixators as a preliminary to evaluating their use for bowel anastomoses. METHODS: Twenty adult Sprague-Dawley rats had 2.0-cm dorsal skin incisions approximated either with shape-memory alloy (SMA) fixators or conventional skin staples on a random basis. Electrical resistance heating was used to transform and deploy the SMA fixators into the wound. The rats were killed on day 14 or day 28 and wound specimens were harvested for force distraction studies and histologic examination. RESULTS: There was no incidence of wound dehiscence. 14- and 28-day wounds from both groups showed no significant difference in breaking force or energy. Histology revealed appropriate stages of wound healing for both SMA-closed and control wounds. CONCLUSIONS: The results confirm the efficacy and safety of tissue-edge approximation with SMA fixators.

Alloys↗

PubMed2000

Self-expanding metallic stents in the management of advanced esophageal cancer: a review.

Palliation of advanced esophageal cancer continues to be a challenge to clinicians. Self expanding metal stents have been used in the esophagus for palliation of advanced esophageal cancer since 1983. They are relatively easy to insert by practicing endoscopists and have low rates of early complications. Delayed complications necessitating reintervention can arise in as many as a third of patients. The majority of stents are placed under sedation using endoscopy and fluoroscopy. Once deployed, they expand in the esophagus causing pressure necrosis on the wall of the esophagus. Several stents are available on the market with newer designs continuing to emerge. Choice of stent seems random among clinicians. Stents have been used for the management of esophageal obstruction including cervical esophageal obstruction and obstruction at the esophagogastric junction, tracheopulmonary fistulae, and mediastinal esophageal compression. Complications include chest pain, deployment and expansion problems, stent migration, tumor overgrowth and ingrowth, gastroesophageal reflux, and stent-related hemorrhage. Despite their high cost, stenting produce better palliation and some cost savings in comparison to conventional methods of palliation. Combination therapy using stenting followed by chemo/radio therapy may increase quality survival.

Equipment Design↗

PubMed1998

Randomised study of influence of two-dimensional versus three-dimensional imaging on performance of laparoscopic cholecystectomy.

BACKGROUND: Several three-dimensional video-endoscopic systems have been introduced to enhance depth perception during minimum-access surgery. However, there is no conclusive evidence of benefit, and these systems are more expensive than conventional two-dimensional systems. We undertook a prospective randomised comparison of two-dimensional and three-dimensional imaging in elective laparoscopic cholecystectomy for symptomatic gallstone disease. METHODS: The operations were done by four specialist registrars as part of their higher surgical training. 60 operations were randomised for execution by either two-dimensional or three-dimensional imaging display (30 by each method). The degree of difficulty of the operation was graded by a consultant surgeon on a standard grading system. The primary endpoints were execution time and the errors made during the procedure. The secondary endpoints were subjective assessment of the image quality and adverse effects on the surgeon. FINDINGS: There was no difference between the two-dimensional and three-dimensional display groups in median execution time (3160 [IQR 2735-4335 vs 3100 [2379-3710] s; p = 0.2) or error rate (six vs six). Surgeons reported adverse symptoms immediately after the operations with both systems. The scores for visual strain, headache, and facial discomfort were higher with the three-dimensional system. INTERPRETATION: With the current technology, three-dimensional systems based on sequential imaging show no advantage over two-dimensional systems in the conduct of laparoscopic cholecystectomy.

Adult↗

PubMed1998

Thermal characteristics of a hepatic cryolesion formed in vitro by a 3-mm implantable cryoprobe.

The objective of the investigation was to characterize the hepatic cryolesion formed with an implantable needle (3 x 100 mm) cryoprobe. This was used to produce cryolesions in isolated porcine liver tissue equilibrated to 37 degrees C in a water bath. The shape, size, and temperature zones within the cryolesion and the effect of single versus repeated freeze-thaw cycles on cryolesion size were studied. The final shape of the cryolesion at 15-20 min freezing was cylindrical and its distal hemispherical end extended 8 mm beyond the tip of the cryoprobe. The rate of increase in maximum diameter was logarithmic and decreased from 4.7 mm/min during the first 5 min to 0.4 mm/min during the fourth 5-min period of freezing. By contrast, the rate of increase in volume was linear and ranged from 9.6 to 7.9 ml/min during the corresponding periods. The volume of the hepatic cryolesion after 20 min of continuous freezing was significantly greater than that of the cryolesion formed with 20 min of cumulative freezing interrupted by a 5-min spontaneous thaw. The ultimate temperatures reached and the cooling rates varied in different zones within the cryolesion depending on distances away from and alongside the cryoprobe. Diameter measurements taken in isolation do not reflect the actual growth rate of the cryolesion. Volume measurements define more accurately the amount of tissue frozen and left in situ. Prolonged freezing beyond 20 min did not increase the diameter of the cryolesion. A single continuous freeze produces a larger cryolesion than two freeze-thaw cycles of the same freezing duration.

Animals↗

PubMed1998

Cytotoxicity of electro-surgical smoke produced in an anoxic environment.

BACKGROUND: The effect on cell viability of smoke produced during high-frequency electro-surgery has not been previously reported. The aim of this study was to produce smoke in vitro, in a closed environment similar to that encountered in minimal access surgery, and to test its cytotoxic effects on cultured cells. METHODS: Pig liver was cut repeatedly with an electro-surgical hook knife, and the smoke generated was collected and equilibrated with cell culture medium. MCF-7 human breast carcinoma cells were exposed briefly to various dilutions of this medium and tested for clonogenicity. RESULTS: Electro-surgical smoke produced in a helium environment reduced the clonogenicity of the MCF-7 human breast carcinoma cells in a dose-dependent manner, falling to 30% when the cells were exposed to undiluted medium for 15 minutes. CONCLUSIONS: We conclude that electro-surgical smoke is cytotoxic. The sublethal effects at lower dilutions are currently being investigated.

Anaerobiosis↗

PubMed1998

Does laparoscopic cardiomyotomy require an antireflux procedure?

BACKGROUND AND STUDY AIMS: There is controversy concerning the need for an antireflux procedure in patients undergoing open or endoscopic cardiomyotomy for achalasia. The addition of an antireflux wrap (partial or total), while preventing reflux, may result in persistence or incomplete relief of dysphagia in patients with total oesophageal aperistalsis. The technique of laparoscopic cardiomyotomy used in Dundee preserves the lateral and posterior attachments of the gastro-oesophageal junction, and was designed to minimize the risk of gastro-oesophageal reflux. PATIENTS AND METHODS: A consecutive series of patients with achalasia (n = 19) were treated by laparoscopic cardiomyotomy using the Dundee technique, which limits the mobilization to the anterior wall of the abdominal and thoracic oesophagus. The patients were followed up prospectively to assess the long-term relief of dysphagia and the postoperative incidence of reflux symptoms, with or without oesophagitis. RESULTS: The follow-up symptoms and assessment of the patients (15-53 months, median 27 months) showed total relief (n = 12) or substantial relief (n = 5) of dysphagia in 89%. On assessment at a median follow-up of 27 months, the number of patients experiencing heartburn after this operation increased from four of 15 to five of 15, and one patient (6.6%) developed endoscopically proved oesophagitis, with a positive oesophageal pH monitoring test. CONCLUSIONS: The routine addition of an antireflux operation is not justified in patients undergoing laparoscopic cardiomyotomy, provided that the lateral and posterior attachment of the oesophagus are kept intact.

Adult↗

PubMed1998

Task performance in endoscopic surgery is influenced by location of the image display.

OBJECTIVE: To investigate the influence of image display location on endoscopic task performance in endoscopic surgery. SUMMARY BACKGROUND DATA: The image display system is the only visual interface between the surgeon or interventionist and the operative field. Several factors influence the correct perceptual processing and endoscopic manipulation from images. One of these is location of the image display with respect to the surgeon and to the operative site. The present study was conducted to investigate whether endoscopic task performance improves under two conditions: when the surgeon-to-monitor visual axis is aligned with the forearm-instrument motor axis and when the image display is close to the operator's manipulation workspace. METHODS: An endoscopic task (tying an intracorporeal surgeon's knot) was performed under standardized conditions except for varying monitor locations. These altered the direction of view--in front of, to the left, and to the right of the operator's head and hands. In each of these view directions, the monitor was placed at the surgeon's eye level and lower down, at the level of the operator's hands. The outcome measures were the execution time, knot quality score and performance quality score. RESULTS: Task performance was better with frontal view direction: execution time was shorter (p < 0.0001) and the performance score was higher (p < 0.005) than with side viewing, with no significant difference between right and left viewing directions. With frontal view direction, hand-level "gaze-down" viewing resulted in a shorter execution time (p < 0.01) and a higher performance score (p < 0.01) than eye-level viewing. CONCLUSIONS: Task performance improves when the image display is placed in front of the operator, at a level below the head and close to the hands.

Clinical Competence↗

PubMed1997

Laparoscopic common bile duct exploration after failed endoscopic stone extraction.

BACKGROUND AND STUDY AIMS: Despite the documented success rate and safety of laparoscopic ductal stone extraction, the majority of patients are treated with preoperative endoscopic stone extraction followed by laparoscopic cholecystectomy. When this fails, conventional open cholecystectomy and common bile duct exploration are performed. We report here a series of patients who were treated laparoscopically after failed attempts at endoscopic stone extraction. PATIENTS AND METHODS: Nineteen patients (12 women and seven men, aged 41-96 years) were treated laparoscopically. Four had undergone previous cholecystectomy. ERCP had been attempted in all patients, was unsuccessful in three patients, and had been interpreted as normal in two. Endoscopic stone extraction had been attempted in 14 patients. The mean follow-up period was 23 months, range 1-54 months. RESULTS: Ductal calculi were confirmed in 18 patients with successful and complete laparoscopic ductal clearance in 15 (83%), two of whom underwent an additional laparoscopic choledochoduodenostomy due to a large stone load and a grossly dilated common bile duct. Conversion to open surgery was required in three cases (17%). Ductal clearance at a single operation was achieved in all 18 patients. There were no postoperative deaths, but two patients developed postoperative complications (11% morbidity), one requiring laparotomy. The median postoperative hospital stay was five days, range 4-41 days. Recurrence of calculi was encountered in one patient. CONCLUSIONS: Laparoscopic ductal stone clearance after failed endoscopic stone extraction is successful in the majority of patients, and should be attempted prior to recourse to open surgery, provided the necessary laparoscopic biliary expertise is available.

Adult↗

PubMed1995

Ultrasonographic characterization of hepatic cryolesions. An ex vivo study.

OBJECTIVE: To determine the physical basis for the ultrasonographic characteristics of the hepatic ice ball produced by cryotherapy and the size correlation between the actual hepatic ice ball and the ultrasonographic cryolesion. DESIGN: Experimental ex vivo study involving controlled freezing with liquid nitrogen recirculating probes of fresh porcine livers immersed in various solutions at ambient temperatures (20.2 degrees C to 22.6 degrees C), together with measurements of the impedance of frozen and unfrozen liver. RESULTS: First, the hyperechoic rim is caused by reflection of 34% of ultrasound waves at the interface between unfrozen and frozen liver as a consequence of an increased acoustic impedance of frozen liver that was calculated to be approximately 3.8 times that of unfrozen liver tissue. The increased acoustic impedance is due to the decrease in elasticity of hepatic tissue as it freezes. Second, the posterior acoustic shadowing is partly due to the attenuation of the incident ultrasound waves by reflection at the interface between unfrozen and frozen liver. It is also dependent on the crystalloid-protein content of hepatic parenchyma, which ensures a homogeneous lesion by preventing "shattering" within the cryolesion. This is in sharp contrast to the ultrasonographic appearance of an ice ball formed in ionized water, in which the hyperechoic rim overlies an area of posterior acoustic enhancement. Third, the correlation of the size between the ultrasonographic cyrolesion and the measured hepatic ice ball approached unity (r = .99), and the two measurements were identical for cryolesions less than 50 mm in diameter. CONCLUSION: Ultrasound is an accurate method for depicting the actual diameter of frozen solid hepatic tissue in cryotherapy for liver tumors, but the present technology does not provide accurate assessments of the volume of frozen tissue.

Animals↗

PubMed1995

Comparative evaluation of contact ultrasonography and transcystic cholangiography during laparoscopic cholecystectomy: a prospective study.

BACKGROUND: The role of intraoperative cholangiography (IOC) during laparoscopic cholecystectomy (LC) is controversial. While many advocate its routine use, others argue for a selective approach. Recent reports showed laparoscopic contact ultrasonography (LCU) as a viable alternative to IOC. However, no prospective data were available to compare the accuracy, efficacy, and safety of the two diagnostic procedures. OBJECTIVE: To evaluate the benefits and disadvantages of LCU and IOC during LC. METHODS: Seventy-eight patients who underwent LC at Pisa (Italy) and Dundee (Scotland) university hospitals were entered in a prospective data registry. Details of operative technique and results of LCU and IOC were analyzed by reviewing videotape recordings of each procedure. RESULTS: Laparoscopic cholecystectomy was achieved in 73 patients, with five requiring conversion to the open procedure. The success rate of IOC was 90% (64/71). Performance of IOC demanded more than twice the time needed for LCU. Eleven percent (8/71) of cholangiograms were abnormal, with a false-positive rate of 1% (1/71). Laparoscopic contact ultrasonography detected all four instances of unsuspected ductal stones but none of the three cases of anomalous biliary anatomy. Clinically relevant incidental findings were picked up by LCU in six patients. CONCLUSIONS: Laparoscopic contact ultrasonography proved to be extremely accurate in the detection of ductal stones but less reliable in the disclosure of anomalous biliary anatomy. The essential role of IOC in providing a clear spatial display of the biliary tract was confirmed. Since the two procedures are complementary, their combined use is advisable in difficult LC to avoid retained common bile duct stones and prevent iatrogenic complications.

Adenoma↗

PubMed1995

Atraumatic retractor for endoscopic surgery.

A novel retractor has been designed to achieve atraumatic retraction of the liver and displacement of hollow viscera during endoscopic surgery. The functional section of the instrument, when locked, forms a silicon-covered uniplanar hook which can be deployed for horizontal lift of solid organs such as the liver or be used to engage bowel for displacement from the operative field. Following laboratory testing, the instrument has been evaluated clinically and its ease of deployment and atraumatic nature have been confirmed. It has been found to be particularly effective for elevation of the thick fatty left lobe of the liver during antireflux surgery.

Endoscopes↗

PubMed1995

Dissection techniques in laparoscopic surgery: a review.

Efficient and safe dissection in laparoscopic surgery consists of the elements of exposure, tissue stabilization and tissue division. Exposure includes bulk exposure of organs and fine exposure of tissues during dissection. In endoscopic surgery this necessarily requires meticulous haemostasis. Tissue stabilization by atraumatic means displays the tissues with appropriate lines of tension to facilitate tissue division. This can be accomplished by a variety of energy types. Besides conventional dissection techniques, technologically advanced dissection systems employing different energy types have been incorporated in laparoscopic surgery. Mechanical energy sources such as ultrasound waves and the kinetic energy of a pressurized water-jet achieve precise dissection without haemostasis. However, thermal energy sources such as high-frequency electrosurgery and lasers achieve haemostatic dissection. Thermal methods generate destructive heat in the body which leads to coagulation or separation of tissues. Surgeons have to be aware of the principles of these dissection techniques, their tissue interactions, their advantages and limitations.

Dissection↗

PubMed1995

Access with flexible cannulae.

Flexible access cannulae maintain a readily accessible tract for the efficient introduction and withdrawal of both straight and curved endoscopic instruments from skin to the parietes. Their main advantage is their capacity to deform, allowing the passage of curved instruments. Several designs of flexible access cannulae are currently available. The most practical design makes use of tightly coiled springs as tubes with or without silicone coating. A modification of this design uses wire woven into a tubular form and coated with silicone. Gas seal valves for these cannulae are currently primitive. The capacity of flexible access cannulae for deformation along the longitudinal and transverse axes could potentially be exploited for retrieval of small organs. Clinically, flexible cannulae have been used whenever curved instruments were needed. Coaxial curved and bayonet instruments have been used extensively in both thoracoscopic and laparoscopic operations. These instruments will allow an additional degree of freedom, that of the pre-formed curve of the instrument. In clinical terms this will facilitate the dissection, retraction and encirclement of tubular structures. In addition, the creation of intra-corporeal surgical knots is more efficient using curved needle holders.

Catheterization↗

PubMed1994

Laparoscopic prosthesis fixation rectopexy for complete rectal prolapse.

Five women aged 64-81 years with complete rectal prolapse and incontinence were treated by laparoscopic mobilization of the rectum and posterior fixation to the presacral fascia using Marlex mesh. Mobilization was carried out with standard straight laparoscopic instruments in the first two patients (operating times 3.5 and 4.5 h) and with coaxial curved instruments and ultrasonic dissection in the succeeding three (operating times 2.5, 2.0 and 2.5 h). Restoration to full continence (grade 1) was observed in two patients and to grade 2 in a further two. No recurrence of the prolapse occurred during follow-up of 4-27 months.

Aged↗

PubMed1994

Comparative study of the holding strength of slipknots using absorbable and nonabsorbable ligature materials.

The holding and tensile characteristics of five extracorporeal slipknots in relation to absorbable and nonabsorbable ligature materials have been evaluated in a standardized in vitro test rig. The knots studied: Tayside, Roeder, Melzer (modified Roeder), Cross square, and Blood knots were tied with the following materials: silk, polyamide, Dacron, polydioxanone (PDS), and lactomer (Polysorb). Following construction and slippage (run down) to a fixed-diameter loop around a cylinder, the knots were locked (tightened) using a standardized force after which they were removed from the test rig and subjected to holding strength (force required to induce reverse slippage) and other tensile characteristics (stress, strain, elasticity) by a tensiometer. Analysis of the data has demonstrated the following: (1) The safest slip knots (resist slippage) are the Tayside, Melzer, and Roeder knots tied with lactomer and Dacron. (2) The holding strengths of the Cross square and Blood knots are weak with all ligature materials tested. (3) Polydioxanone is a safe ligature material for the Melzer and Tayside but not the Roeder knot. (4) Extracorporeal slipknots tied with silk and polyamide are less secure than the equivalent knots tied with Dacron, lactomer, and polydioxanone.

Insect Proteins↗

PubMed1994

Diagnostic yield and management benefit of laparoscopy: a prospective audit.

A prospective audit of the diagnostic yield and management benefit of laparoscopy was undertaken in 220 consecutive patients. The procedure was performed electively in 180 patients and as an emergency in 40. The indications for laparoscopy in the elective group were suspected hepatic disease, staging of intra-abdominal malignancy, diagnostic problems, and chronic abdominal pain. Emergency laparoscopy was performed in patients admitted with acute abdominal pain. Diagnostic benefit varied with the indication for the procedure: liver disease 71%, tumour staging 87%, uncertain diagnosis 74%, acute abdominal pain 100%, and chronic abdominal pain 41%. Clinical management was significantly influenced by laparoscopy in 15 of 21 (71%) patients with liver disease, 10 of 30 (33%) with intra-abdominal malignancy, 5 of 19 (26%) with uncertain diagnosis, 32 of 40 (80%) with acute abdominal pain, and 15 of 110 (23%) patients with chronic abdominal pain. A wrong assessment of the nature or stage of the disease was made by laparoscopy in 3 of 220 (1.0%). There was no morbidity or mortality attributed to laparoscopy in the study.

Abdomen, Acute↗

PubMed1994

Bilateral endoscopic splanchnicectomy through a posterior thoracoscopic approach.

The technique of bilateral total splanchnicectomy performed through a posterior thoracoscopic approach is described. The advantages of this route include excellent visual exposure of the neural anatomy of the sympathetic and avoidance of single lung anaesthesia. The procedure was performed for the relief of intractable pain in patients with advanced pancreatic cancer (n = 3) and patients suffering from chronic pancreatitis (n = 5). Persistent relief of pain until death was obtained in the patients with pancreatic cancer (2, 4, 6 months). In patients with chronic pancreatitis, the benefit to date has varied with the severity of the disease. In two patients with severe advanced disease and previous percutaneous blocks, the relief of pain lasted only 3 and 5 weeks and both patients required resection for renewed intractable pain. In three patients with minimal change disease, relief of pain has been good in the short term (maximum follow-up of 8 months). Bilateral thoracoscopic total splanchnicectomy merits further evaluation in patients with pancreatic pain. No complications including hypotension have been encountered.

Denervation↗