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G W Stevenson

Publications and source records attributed to G W Stevenson.

At least 19 recordsLinked to original sources
PubMed1992

Antagonism of drug discrimination learning within the conditioned taste aversion procedure.

Animals injected with morphine prior to the presentation of a saccharin-LiCl pairing and the morphine vehicle prior to saccharin alone rapidly acquired the drug discrimination, avoiding saccharin following the administration of morphine and consuming saccharin following its vehicle after only four conditioning trials. Once stimulus control was established, the opiate antagonist naloxone (1 mg/kg) was administered prior to morphine in a test of its ability to antagonize the morphine stimulus. Pretreatment times ranged from 10 to 180 min. Naloxone antagonized the stimulus properties of morphine for all subjects, although there were individual differences in the onset, duration (time course) and degree of antagonism. Together with the rapid acquisition typically reported in this design, the fact that antagonism was demonstrated in the present study suggests that the conditioned taste aversion procedure may be useful in the general assessment of drug discriminations.

Animals↗
PubMed1992

Sonographic changes during hepatic interstitial laser photocoagulation. An investigation of three optical fiber tips.

RATIONALE AND OBJECTIVES: Interstitial laser photocoagulation (ILP) destroys tumors thermally, using laser energy delivered from implanted optical fibers. The objectives of the study are to identify a fiber tip/delivered energy combination which produces lesions of useful size, visible on ultrasound (US) during ILP, and to compare ILP lesions and their US images. METHODS: Hepatic ILP was performed at laparotomy in six pigs, using three different fiber tips (cylindrical diffusing, spherical diffusing, plane-cut). US images were obtained during ILP, immediately after ("early" images), and before the animals were killed (2-2.5 hours, "late" images). Actual lesions were assessed histopathologically. RESULTS: Few US changes were seen around cylindrical diffusing and spherical diffusing tips until tip destruction. Plane-cut tips, at 1.5 to 2.0 W, produced prominent US images of the 1- to 2-cm thermal lesions. Early images tended to overestimate necrosis. Late images approximated necrosis. CONCLUSION: For US-controlled ILP, plane-cut tips are better than currently available cylindrical diffusing or spherical diffusing tips. Lesion image growth periods might enable control of lesion size. Further studies are needed to determine the consistency of the described relationship between lesion images and actual lesions.

Animals↗
PubMed1992

Relation of pyloric motility to pyloric opening and closure in healthy subjects.

The relation between pyloric motor activity, opening, and closure was examined in eight healthy men. Manometry was performed with an assembly combining 13 side holes and a sleeve sensor positioned astride the pylorus. Simultaneous with manometry, pyloric opening and closure and antroduodenal contractions were observed fluoroscopically with the antrum filled with barium. During intraduodenal normal saline infusion, coordinated antral pressure waves swept over the pylorus and ejected barium into the duodenum. No localised pyloric motor pattern was observed under these conditions. In contrast, the intraduodenal triglyceride infusion was associated with the absence of antral pressure waves and virtual absence of antral wall movement. At the pylorus, there was a zone of luminal occlusion less than 1 cm long that persisted for the period of observation. This zone of luminal occlusion corresponded precisely with manometric recordings of a narrow zone of pyloric phasic and tonic activity. During the duodenal triglyceride infusion, the pylorus was closed for 98.5% of the measurement period when basal pyloric pressure was 4 mm Hg or more, and during this motor pattern, barium did not traverse the pylorus. Localised pyloric contractions cause sustained pyloric closure, whether these contractions are phasic or tonic. These contractions occur independently of antral or duodenal contractions and may interrupt gastric emptying.

Adult↗
PubMed1992

Contrast medium gel for marking vaginal position during defecography.

A tampon soaked with contrast medium, which had been inserted into the vagina as part of standard defecography procedure, obscured signs of anterior rectocele and rectal intussusception in a 34-year-old woman. A contrast medium gel for marking vaginal position was formulated, and postsurgical examination with use of the gel revealed improved rectal function and no intussusception. The gel provided excellent contrast without obscuring important diagnostic information.

Adult↗
PubMed1992

The gastrocolic trunk and its tributaries: CT evaluation.

Dilatation or occlusion of the gastrocolic trunk (GT) may be a clue to a portal venous or pancreatic pathologic condition. To evaluate the normal and abnormal appearances of the GT and its tributaries at computed tomography (CT), the CT scans, angiograms, and surgical-pathologic records of 21 patients with cancer of the pancreas and 15 patients with chronic pancreatitis were reviewed retrospectively. The CT examinations of 30 patients with metastatic disease of the liver and no known pancreatic disease were studied for comparison. A normal GT (2.6-4.7-mm diameter) was identifiable in 48% of the control group in CT scans obtained with 10-mm-thick sections and in 90% of CT scans obtained with 5-mm-thick sections. The GT was dilated in five patients with isolated splenic vein occlusion and in five patients with occlusion or stenosis of the portal-superior mesenteric vein confluence (P-SMVC) above the level of the GT entry into the superior mesenteric vein. The GT was obliterated in eight patients and was associated with P-SMVC occlusion. Findings at surgery confirmed tumor extension into the root of the transverse mesocolon in three patients with cancer of the pancreas. Abnormal findings at CT, however, do not enable differentiation between benign and malignant pancreatic diseases.

Chronic Disease↗
PubMed1991

Single-visit screening and treatment of first-degree relatives. Colon cancer pilot study.

A pilot study has been carried out to evaluate three aspects of screening of first-degree relatives of patients with colon cancer in four Hamilton hospitals; yield of adenomas, feasibility of a one-visit approach to screening and treatment, and compliance. Protocol included flexible sigmoidoscopy after full bowel preparation, followed immediately by either therapeutic colonoscopy or diagnostic barium enema, depending on the flexible sigmoidoscopy findings. We found adenomas in 19 percent of 88 first-degree relatives, with a mean age of 52, compared with an expectation of 8 percent. The protocol was found to be acceptable to the relatives and workable for the various groups of physicians in three of four hospitals, despite many initial logistic difficulties. Numerous problems were encountered with compliance of referring physicians, index patients, relatives, and investigating physicians.

Adenoma↗
PubMed1991

Anaesthetic management of Miller's syndrome.

Miller's syndrome is a rare congenital disorder with facial features similar to that of Treacher-Collins syndrome. This report details the anaesthetic management of an infant during multiple surgical procedures, beginning with pylormyotomy at one month of age. Airway management was difficult because of severe micrognathia and was accomplished using an awake intubation with a conventional straight blade modified for continuous administration of oxygen ("oxyscope"). Due to recurrent upper airway obstruction and the anticipated need for multiple surgical procedures in the first years of life, a tracheostomy was placed. Because of the multiple airway, orthopaedic, and nutritional difficulties, it is important that a prospective, multidisciplinary approach be used in these patients' care. Consideration should be given to early tracheostomy for airway maintenance.

Anesthesia, Inhalation↗
PubMed1991

Barium meal or endoscopy? A prospective randomized study of patient preference and physician decision making.

This study examines the preference of 64 out-patients for either a barium meal or an upper gastrointestinal endoscopy. The sequence of the examinations was randomized to avoid order bias. An initial preference for a barium meal of almost two-to-one, with 53% having no preference, was changed after the investigations to a preference for endoscopy of two-to-one with 5% having no preference. The use of mild sedation and the skill of the endoscopist had a major impact on the patients' opinion of the endoscopic procedure, and on their choice of examination for any repeat study. There was little agreement between clinical diagnosis and the result of investigation, but clinicians tended to accept the reported result of the investigation, especially if the result was abnormal. Despite a change in diagnosis in 34 of 49 patients there was little change in management as a result of the investigations, supporting the view that young patients with dyspepsia may be managed with symptomatic treatment initially, and without investigation. This study lends further support to the view that endoscopy should be the investigation of choice in patients with persistent dyspepsia, especially those whose age or infirmity may make barium examination suboptimal.

Barium Sulfate↗
PubMed1991

Halothane potentiates the antitumor activity of gamma-interferon and mimics calmodulin-blocking agents.

This study reports effects of halothane on tumor cells in vitro. Cells from the human colon cancer cell line HT-29 were exposed to various concentrations of halothane for 8-72 h. The effect of this exposure on this colon cancer cell line, with and without coincubation with the biologic response modifier gamma-interferon (IFN-gamma), was studied. Using the tumor target cell survival (TTCS) assay, concentrations of halothane from 0.5 to 2% markedly augmented the antitumor activities of IFN-gamma against HT-29. The tumor cell cytostatic effects of IFN-gamma in the 0.75-6-unit/ml range were increased nearly 400% by concentrations of halothane as low as 1%. These results were confirmed in a separate cytolytic assay (Indium-111 release assay), which revealed that halothane concentrations in the 2-4% range markedly increased the cytolytic capacity of IFN-gamma at doses of IFN-gamma between 75 and 1,250 units/ml. The cytolytic activity of IFN-gamma was increased nearly 300% by doses of halothane as low as 1%. A nearly identical pattern of augmentation of IFN-gamma-induced antitumor activity was observed when the known calmodulin inhibitor trifluoperazine (TFP) was coincubated with IFN-gamma. At concentrations of 4-10 microM, the antitumor activity of IFN-gamma was increased nearly 400%. These observations suggest that the pattern of halothane potentiation of the antitumor activity of IFN-gamma is similar to that exhibited by known calmodulin inhibitors.

Antineoplastic Agents↗
PubMed1990

Anesthetic considerations in the pediatric cancer patient.

Cancer is second only to trauma as the leading cause of death in children 1-15 years of age. Pediatric cancer patients have unique physiologic, pharmacologic, and psychologic considerations that present a unique challenge to plan anesthesiologist. A thorough understanding of pediatric tumors, along with chemotherapeutics and their complications, is necessary to plan anesthetic management properly. Special attention is directed to the psychologic needs and preparation of both the patient and parents. Close cooperation and coordination among the pediatric oncologist, surgeon, and anesthesiologist are necessary for safe and expeditious operative care.

Adolescent↗
PubMed1990

Laxatives prior to small bowel follow-through: are they necessary for a rapid and good-quality examination?

Fifty-six patients undergoing small bowel follow-through examination were randomly allocated to two groups to assess the effect of preparation with laxative on the speed and quality of the examination. We found that laxative had no effect on either speed of the examination or quality of visualization of small bowel. However, the latter was dependent on the degree of supervision and technique of the examining radiologist.

Barium Sulfate↗
PubMed1990

Perforating duodenal diverticulitis.

Two cases of perforating duodenal diverticulitis are reported, one with enterolith formation, and the other with sonographic evidence of retroperitoneal emphysema. The possible complications of duodenal diverticula, as well as the difficulties encountered in preoperative diagnosis, are discussed.

Aged↗
PubMed1990

Transoesophageal pacing for perioperative control of neonatal paroxysmal supraventricular tachycardia.

The perioperative management of a 16-day-old infant with recurrent supraventricular tachycardia (SVT) is discussed. Vagal manoeuvres and medication were not adequate in controlling the SVT. Since the patient was scheduled for extensive surgery in the prone position, it was decided to use transoesophageal pacing as the method of choice for conversion of SVT. Transoesophageal pacing succeeded several times in overriding the SVT and restoring normal heart rate and haemodynamic variables. The advantages and disadvantages of various methods of treating SVT in the newborn are discussed.

Cardiac Pacing, Artificial↗