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Biomedical subjects

G R Mason

Publications and source records attributed to G R Mason.

At least 19 recordsLinked to original sources
PubMed1991

Perspectives a century later on the "Ansa en Y" of César Roux.

During the last 100 years, since César Roux began utilizing his "Ansa-en-Y" procedure for gastric outlet obstruction, the procedure at first fell into disuse but was later adapted for other applications. This article discusses the background of the procedure and compares the original indications with the author's current experience. Current applications in this series were for chronic pancreatitis (26 patients), alkaline gastritis (22 patients), biliary duct obstruction (7 patients), pancreatic pseudocyst (3 patients), and gastric substitution (3 patients).

Anastomosis, Roux-en-Y↗
PubMed1991

Experimental cholelitholysis with the pulsed tunable dye laser.

This study evaluates the pulsed tunable dye laser with wavelength 504 nm, frequency 10 Hz, and pulse width 1.2 microseconds for cholelitholysis. Power of 10-40 kW was directed through a 250-microns quartz fiber optic to ablate 55 gallstones (removed from 14 patients). The fiber was positioned in direct contact with the stones under saline. Power delivery was begun at 10 kW and increased in 10-kW increments until litholysis began. The range of power and energy necessary to fragment the gallstones was evaluated on four common bile ducts (fresh autopsy specimens). Following fragmentation, all stones were analyzed. There were 35 cholesterol stones (3 calcified) and 20 bilirubin stones (4 calcified). Size ranged from 0.012 to 7.56 cm3 (mean 0.96 +/- 1.41 cm3). Energy necessary for fragmentation ranged from 0.4 to 11.2 J (exposure time 1.0-28 s). Power necessary for fragmentation was 20 kW for 2/55 stones and 40 kW for 53/55 stones. At 40 kW (40 mJ/pulse), common bile duct perforation occurred within 1.1 +/- 0.1 s (0.44 +/- 0.04 J). The pulsed tunable dye laser can fragment gallstones of all compositions. The threshold for fragmentation is 40 kW, but common bile duct perforation occurs at this power. We conclude that laser radiation sufficient to fragment gallstones can injure the common bile duct.

Cholelithiasis↗
PubMed1990

Initial trial of argon ion laser endarterectomy for peripheral vascular disease.

In the initial of open laser endarterectomy, 16 patients underwent 18 reconstructions for claudication (13 patients), rest pain (3 patients), and gangrene (2 patients). The mean (+/- SD) preoperative ankle arm index was 0.53 +/- 0.18. The laser endarterectomies were aorto-bi-iliac (1 patient), iliac (1 patient), superficial femoral (7 patients), profunda femoral (7 patients), and popliteal-posterior tibial (2 patients). All operations included surgical exposure, vascular control, administration of heparin, and an arteriotomy. Atheromas were dissected from arteries with argon ion laser radiation (power, 1.0 W). End points were welded with laser light. Arteries were closed primarily. The laser endarterectomies were 6 to 60 cm long and required 168 J to 2447.5 J. All patients had symptomatic relief, with a postoperative ankle arm index of 0.97 +/- 0.10. There were no arterial perforations from laser radiation. Surgical complications included early thrombosis requiring thrombectomy (3 patients) and hematoma requiring evacuation (1 patient). The laser endarterectomies have an 88% patency at 1 year. Open endarterectomy can be performed with laser radiation. A larger clinical trial is necessary to define the indications for laser endarterectomy in peripheral vascular disease.

Adult↗
PubMed1990

Application of nuclear medicine techniques to the study of ARDS.

Radionuclide techniques used for the diagnosis and study of ARDS include the routine clinical procedures of perfusion lung scanning, gallium and white-cell imaging, as well as PET, indicator dilution methods for measuring extravascular lung water, and means of measuring protein accumulation, protein flux, and solute transfer. The techniques that reflect the rate of protein leak from the microvasculature and sensitive measures of rapidly reversible alveolar injury appear most promising. While clinical usefulness remains to be documented, these methods may ultimately assist with the diagnosis of ARDS and with the evaluation of prognosis and therapy.

Humans↗
PubMed1990

Effect of mechanical ventilation and barotrauma on pulmonary clearance of 99mtechnetium diethylenetriamine pentaacetate in lambs.

We studied the effect of positive pressure mechanical ventilation on the pulmonary clearance (k) of 99mtechnetium diethylenetriamine pentaacetate (99mTc-DTPA) in lambs. Twelve lambs were anesthetized and ventilated with air at 25 breaths/min and with end expiratory airway pressure at 2 cm H2O for a minimum period of 8 h. Four lambs received normal pressure ventilation with peak airway pressure at 17 +/- 3 cm H2O and eight received high pressure ventilation with peak airway pressure at 41 +/- 2 cm H2O. Three 99mTc-DTPA clearance studies were done in each lamb; at the start and after 4 and 8 h of mechanical ventilation. All clearance measurements were made at normal peak airway pressure 16 +/- 3 cm H2O. Baseline clearance rate, k, (n = 12) was 1.2 +/- 0.5% (SD). During normal pressure ventilation, k increased from 1.0 +/- 0.5 to 2.2 +/- 0.8% after 4 h and to 2.7 +/- 0.8% after 8 h. During high pressure ventilation, k increased from 1.4 +/- 0.4 to 3.6 +/- 1.3% after 4 h and to 4.8 +/- 1.2% after 8 h. To see if 8 h of mechanical ventilation was associated with other evidence of lung epithelial injury, we determined the movement of I125 labeled albumin from the interstitium into the airspace, lung water content, lung histology, and lung lavage constituents in the lambs at the end of the study. All variables were similar between ventilated and four unventilated lambs, except the percentage of alveolar macrophages recovered by lavage, which was more in the ventilated lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Initial clinical evaluation of carotid artery laser endarterectomy.

Clinical study of carotid artery laser endarterectomy began April 15, 1988. This report describes the first 10 cases that were performed in nine patients (five men and four women, mean age 70 years). Indications were asymptomatic stenosis (5), transient ischemic attacks (4), and stroke in evolution (1). There were two emergency cases and eight elective cases (including one reoperative case). Surgical exposure, systemic heparinization, vascular control, and a longitudinal arteriotomy were used. The cleavage plane between atheromas and media was developed with argon ion laser radiation (488 and 514.5 nm) directed through a 300 microns quartz fiber at power 1.0 W. Laser radiation was used to cut the atheromas out of the arteries and weld the end points. Residual atheromatous debris were vaporized with individual laser exposures. Arteriotomies were closed with sutures, and blood flow was restored. The endarterectomies were 3.9 +/- 1.1 cm long and required 330 +/- 97 joules. Mean clamp time was 22.5 +/- 7.9 minutes. Shunts were used in two cases. There were no arterial perforations or injuries as a result of laser light. Complications were hematoma (1), respiratory arrest (1), and transient neurologic deficit (1). Carotid endarterectomy is technically feasible with argon ion laser radiation. In the present series, postoperative observations, averaging 12 months and ranging from 5 to 19 months, have shown satisfactory results. No angiographic follow-up examinations were carried out.

Aged↗
PubMed1989

Hepatic resection technique.

The author describes a technique of hepatic resection that is particularly beneficial for segmental and nonanatomic procedures. The technique is reportedly safe and accurate due to the use of the Nd:YAG laser and the ultrasonic dissector.

Humans↗
PubMed1989

New evidence for active sodium transport from fluid-filled rat lungs.

The hypothesis that fluid reabsorption from the air spaces is mediated at least in part by active transport of Na+ was investigated in six sets of experiments conducted in isolated fluid-filled rat lungs. Fluid reabsorption was monitored by following the changes in the air space concentration of labeled albumin. We found that incorporation of bicarbonate rather than a nonvolatile buffer (N-2-hydroxy-ethylpiperazine-N'-2-ethanesulfonic acid) in the air space solution more than doubled the rate of fluid reabsorption. Addition of 10(-4) M amiloride to the air space solution reduced the rate of fluid reabsorption over a 2-h experiment from 1.2 +/- 0.1 to 0.7 +/- 0.1 ml and decreased reabsorption of both labeled and unlabeled Na+ from the air spaces. To show that Na+ could be reabsorbed from the air spaces even if the concentrations of Na+ in the perfusate increased above those in the air space, mannitol (150 mM) was added to the perfusate and air space solutions and the concentrations of Na+ and Cl- were reduced to 90 and 60 mM, respectively. Mannitol diffuses across the pulmonary epithelium very slowly, and it osmotically restrained the movement of water out of the air spaces. Na+ concentrations in the perfusate increased by 10 +/- 2 mM, but concentrations in the air space remained unchanged. Despite an increasingly unfavorable concentration gradient for Na+, 0.2 mmol Na+ and 0.6 ml water were reabsorbed from the air spaces in 2 h. Ouabain (10(-4) M) did not appear to slow fluid reabsorption in the presence of mannitol, but it reduced K+ secretion into the air spaces and increased K+ appearance in the perfusate in a manner consistent with inhibition of Na+-K+-adenosinetriphosphatase at the basolateral surface of the epithelial cells. Fluid reabsorption was not altered when the lungs were exposed to a hypotonic solution (185 mM), but secretion of K+ into the air spaces was accelerated and K+ was lost from the perfusate. These experiments are consistent with active Na+ transport from the air spaces.

Amiloride↗
PubMed1989

Prognostic implications of bronchoalveolar lavage neutrophilia in patients with Pneumocystis carinii pneumonia and AIDS.

The clinical records and bronchoalveolar lavage (BAL) cell differential counts were analyzed in 96 patients at risk for Pneumocystis carinii pneumonia (PCP) from human immunodeficiency virus (HIV) infection to determine if this information may be prognostically useful and to identify possible mechanisms of BAL neutrophilia. In 60 patients with PCP, 15 fatalities or episodes of respiratory failure occurred, and 14 of these patients had greater than 5% BAL neutrophils. Only one of 33 patients with PCP and less than 5% BAL neutrophils died. In contrast, there was no correlation between survival and BAL neutrophil percentages in 33 patients who did not have PCP. Three patients with HIV infection without lung disease had normal BAL cell differentials. Intra-alveolar and interstitial leukocytes found in 17 transbronchial lung biopsies in patients with PCP indicate that the alveolar and interstitial compartments of the lung may be the source of BAL neutrophils. Pathologic evidence of increased severity of diffuse alveolar damage to explain BAL neutrophilia was not found. As BAL neutrophil percentages in PCP had both positive and negative predictive value, this information may be useful to stratify therapeutic trials or to identify the patient with PCP who is at high risk of a complicated or fatal outcome.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Pulmonary epithelial sieving of small solutes in rat lungs.

Transport and consumption of glucose from the air spaces of isolated, fluid-filled lungs can result in significantly lower glucose concentrations in the air spaces than in the perfusate compartment (11). This concentration difference could promote the osmotic movement of water from the air spaces to the perfusate, but the rate of fluid extraction from the air spaces would then be limited by the rates of electrolyte transport through the epithelium. In the present study, measurements were made of solute and water losses from the air spaces of fluid-filled rat lungs and the transport of these solutes and water into the vasculature after addition of hypertonic glucose or sucrose to the perfusate. Increases in the concentrations of Na+, Cl-, K+, and labeled mannitol in the air space were initially comparable to those of albumin labeled with Evans blue. Similarly, decreases in electrolyte concentrations in the perfusate were comparable to those of labeled albumin, indicating that very little solute accompanied the movement of water out of the lungs. Nor was evidence found that exposure of the vasculature to hypertonic glucose resulted in an increase in the rate at which fluid was reabsorbed from the air spaces over a 1-h interval, aside from an initial, abrupt loss of solute-free water from the lungs. These observations suggest that perfusion of fluid-filled lungs with hypertonic solutions of small solutes results in the extraction of water from the air spaces and pulmonary parenchyma across membranes that resist the movement of electrolytes and other lipophobic solutes.

Animals↗
PubMed1987

Fluid reabsorption and glucose consumption in edematous rat lungs.

Solute and water uptake were studied in isolated perfused rat lungs with airspaces filled with the perfusion fluid. The albumin in this solution was labelled with Evans blue (T-1824), and uptake of fluid from the airspaces was documented by an increase in T-1824 concentration in airway fluid of 6.5 +/- 1.6% (n = 5, SEM) at 1 hour and 12.2 +/- 0.9% (n = 10) at 2 hours. The only detectable osmotic force that could have contributed to a loss of fluid from the alveolar fluid was a decrease in airspace glucose concentrations, which fell much more rapidly (from 150 mg/dl to 58.7 +/- 7.1 mg/dl, n = 10, after 2 hours) than plasma glucose (from 150 mg/dl to 128.9 +/- 3.7 mg/dl). Addition of 5 X 10(-5) M terbutaline to the perfusate and airspace solutions nearly doubled fluid reabsorption at 1 hour, an effect that was inhibited by propranolol and did not appear to be related to glucose consumption. Exposure to terbutaline for 2 hours increased epithelial permeability to 3H-mannitol and 22Na+. These observations suggest that active sodium transport and epithelial metabolism or transport of glucose in airway fluid may each play a role in the reabsorption of edema fluid.

Absorption↗
PubMed1987

Reabsorption of solutes and water from fluid-filled rabbit lungs.

Uncertainty persists concerning the mechanisms responsible for fluid clearance from the lungs after the air spaces become flooded in severe pulmonary edema. In this study, solute and water fluxes were investigated in an isolated, fluid-filled, perfused rabbit lung preparation. These lungs were perfused with physiologic 1.0 or 5.0 g/dl albumin solutions, and the air spaces were flushed and filled with the same solutions. Samples were obtained at intervals from the perfusate, and at the end of 1 or 2 h, fluid was pumped from the trachea into collection tubes. Concentrations of albumin (labeled with Evans blue) in the air space increased by 2.4 +/- 0.7% (SEM) at 1 h and by 7.0 +/- 0.8% at 2 h. Approximately half of the increase at 2 h could be attributed to dehydration (as judged by increases in perfusate and air-space Na+ concentration). Because previous studies have indicated that the movement of labeled protein between these compartments is very slow in this preparation, it can be concluded that fluid is being reabsorbed from the air spaces. However, reabsorption appears to be slower in rabbits than in rats and it is not stimulated by terbutaline, an effect observed in other species. Under control conditions, potassium concentrations in the air-space fluid fell from 4.01 +/- 0.05 (SEM) mEq/L to 3.37 +/- 0.14 mEq/L at 1 h. Concentrations of K+ in the perfusate rose during this interval from 3.95 +/- 0.05 mEq/L to 4.39 +/- 0.08 mEq/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1987

Accelerated solute clearance in Pneumocystis carinii pneumonia.

A radioaerosol clearance test was used to detect lung injury in 12 patients with acquired immune deficiency syndrome (AIDS) and Pneumocystis carinii pneumonia documented by bronchoscopy. The clearance of 99mTc-DTPA was elevated over most regions of interest in all of these patients. In each of 7 subjects who responded to trimethoprim-sulfamethoxazole therapy, clearance returned toward normal. Average clearances were either normal or very slightly above the 95% expected upper limit of normal in each of 6 patients with either AIDS or AIDS-related complex without clinical evidence of Pneumocystis infection. The radioaerosol diffusion test may prove useful for determining whether patients who are predisposed to this infection require bronchoscopy and may provide information concerning their response to therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Drug-resistant tuberculosis in a southern California hospital. Trends from 1969 to 1984.

Resistance to one or more antituberculosis drugs was found in 98 of 281 (35%) patients hospitalized at Harbor-UCLA with culture-positive tuberculosis between 1980 and 1984. Resistance to antituberculosis drugs occurred in 23% of patients who had not been previously treated, whereas previously treated patients had a 59% rate of resistance. The overall rates of drug resistance had not significantly changed from prior studies at this hospital. Drug resistance was also found in patients with extrapulmonary disease, but tended to be less frequent than in patients with pulmonary disease. An analysis of risk factors for drug resistance rates revealed no significant differences between Hispanics, blacks, Caucasians, and Asians. Age was not found to be a significant factor to predict resistance rates. Resistance rates were higher if cavitary disease was present on radiographs. Furthermore, cavitary disease seems to be additive to prior antituberculosis treatment as a risk factor for drug resistance. Patients who had both of these risk factors present had 71% incidence of drug resistance rates.

Adolescent↗
PubMed1987

Comparison of continuous-wave lasers for endarterectomy of experimental atheromas.

The standard surgical lasers, argon ion, neodymium-yttrium aluminum garnet, and carbon dioxide, are often operated as continuous wave lasers with specific uses. Clinical trials of laser therapy for arteriosclerotic cardiovascular disease are underway with all three lasers. Therefore, we compared these three lasers under controlled experimental conditions. A thoracoabdominal exploration was performed in 17 arteriosclerotic rabbits. The aorta was isolated, heparin administered, and multiple endarterectomies were performed in each rabbit with each of the lasers. A line of laser craters was created at the proximal and distal ends of an atheroma. Continuous-wave laser radiation was used to connect the craters and thereby form proximal and distal end points. The plaques were dissected free from the aorta with laser light and the end points were fused by laser. The aortas were removed for light microscopy and the animals were killed. The endarterectomy surfaces and end points were serially sectioned and graded according to light microscopic findings (1 = worst, 4 = best). Argon ion laser endarterectomy (N = 16) required 106 +/- 10 J/cm2. The surface score was 3.5 and end point score 3.4. Neodymium-yttrium aluminum garnet laser endarterectomy (N = 13) required 1,289 +/- 115 J/cm2 with a surface score of 2.4 (p less than 0.001 from argon ion) and an end point score of 1.3 (p less than 0.001 from argon ion). Carbon dioxide laser endarterectomy (N = 9) required 30 +/- 5J/cm2 with a surface score of 2.0 (p less than 0.001 from argon ion) and and end point score of 1.6 (p less than 0.001 from argon ion). Perforation occurred in one of 16 argon ion studies (technical error, not laser), in 11 of 13 neodymium-yttrium aluminum garnet studies, and in six of nine carbon dioxide studies. This study demonstrates that of the currently available clinical continuous-wave lasers, the argon ion laser is superior for endarterectomy of experimental atheromas.

Animals↗
PubMed1986

Diagnosis of traumatic cardiac contusion.

Cardiac contusion following blunt chest trauma remains a diagnostic problem because of a lack of sensitive diagnostic tests. This study evaluated thallous chloride Tl 201 single-photon-emission computed tomography in a series of 48 patients following blunt chest trauma. Of the 48 patients, 23 had normal scans. None of these patients proved to have serious arrhythmias during three days of continuous monitoring. Of 25 patients with abnormal or ambiguous studies, five (20%) developed serious arrhythmias requiring therapy. Single-photon-emission computed tomography scanning thus was sensitive in indicating that group of patients at risk of serious arrhythmias, and may therefore prove to be a useful screening test to determine the need for hospitalization and arrhythmia monitoring following blunt chest trauma.

Accidents, Traffic↗