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Biomedical subjects

R A Mason

Publications and source records attributed to R A Mason.

At least 19 recordsLinked to original sources
PubMed1995

Effect of extracorporeal shock-wave lithotripsy on gallbladder emptying in patients with solitary and multiple gallbladder stones.

In a prospective study, we investigated the effect of extracorporeal shock-wave lithotripsy (ESWL) on gallbladder contractility and on fasting and residual gallbladder volume in patients with solitary and multiple gallbladder stones with stone densities < 100 Hounsfield units (HU) and adequate gallbladder function. Twenty-five patients (seven males and 18 females, mean age 48.5 +/- 11.7 years) treated with ESWL were assigned to either group I, consisting of 13 patients with solitary stones < 20 mm diameter, or group II, including patients with two to three stones and maximum stone diameter of 30 mm. ESWL was performed with the MPL 9000 lithotripter. Gallbladder ejection fraction was determined using the method of Dodds after a 12-hr fast and following application of a standard stimulative meal. Gallbladder volume was measured by ultrasound over 90 min at 10-min intervals before ESWL, then at 1, 30, 120, and 210 days after ESWL. At 24 hr after ESWL, residual gallbladder volume increased in group I from 7.4 ml to 13.9 ml (P = 0.0567) and in group II from 6.5 ml to 20.2 ml (P = 0.0076). Thereafter, residual volumes returned to pre-ESWL levels. In group II, post-ESWL fasting volumes were significantly increased over initial values at all time intervals. Correspondingly, only at 24 hr after ESWL, ejection fractions decreased from 73.1% to 64.9% in group I and from 76.5% to 62.7% in group II. No statistically significant differences in gallbladder contractility between the two groups were observed at any point of the follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The role of perspective in the accessibility of goals during reading.

An implicit assumption of several causal reasoning models is that readers adopt the goals of a narrative's protagonist during text comprehension. In apparent violation of this assumption, readers participating in Experiment 1 of the present study drew inferences relevant to a protagonist's goal even when that goal was already satisfied from the perspective of the protagonist. In Experiments 2 and 3, participants were explicitly asked to view the text situation from the point of view of the protagonist. In this case, the goals of the reader and the protagonist should be the same. In these experiments, participants focused on the goals of the protagonist only when those goals had not been satisfied from the perspective of the protagonist. These results are discussed in terms of reader- and character-based perspectives and in terms of text characteristics that cue perspective taking.

Adult↗
PubMed1994

Does adequate patient selection reduce the risk of gallstone recurrence after successful extracorporeal shockwave lithotripsy?

To determine the risk of gallbladder stone recurrence in these patients, 58 of the first consecutive 61 patients with solitary stones achieving complete stone clearance after ESWL and adjuvant bile acid therapy were included in a prospective study. All patients were observed for at least 12 months following discontinuation of oral bile acids. Twenty-one patients fulfilled our postulated ideal criteria (solitary radiolucent stones between 10-20 mm initial diameter, initial stone density < 50 HU, gallbladder ejection fraction > 70%). The remaining patients (n = 37) fulfilled the criteria of the Munich study group. In patients fulfilling our ideal criteria, stone recurrence was not observed in any patient, while in those fulfilling solely the criteria of the Munich group, five instances of stone recurrence were observed (13.5% [n = 37], p < 0.1). Initial stone count is only one factor influencing the probability of gallstone recurrence following ESWL and discontinuation of oral bile acids. Our data suggest that factors such as low initial stone density at gallbladder CT and good gallbladder function not only accelerate initial stone clearance but also reduce the risk of stone recurrence after ESWL once oral bile acids have been discontinued.

Adult↗
PubMed1992

Serum erythropoietin quantitation in pregnancy using an enzyme-linked immunoassay.

During normal pregnancy there is a decrease in the hematocrit due to a disproportionate increase in the blood volume compared with the red cell mass. Using a new enzyme-linked immunoassay (Amgen Diagnostics), serum erythropoietin was quantified in normal nonanemic pregnancies throughout gestation and in third trimester anemic patients. We found that the mean hematocrit in normal pregnancy reached a nadir late in the second trimester and the serum erythropoietin plateaued at a 50% increase. Those pregnancies complicated by anemia defined by a hematocrit less than 30 vol% demonstrated a statistically significant increase in serum erythropoietin above those not anemic.

Adolescent↗
PubMed1992

Wound complications of the retroperitoneal approach to the aorta and iliac vessels.

Repeated complaints of postoperative wound pain prompted this review of 113 consecutive vascular operations involving a retroperitoneal approach to the aorta or iliac vessels or both. Flank muscle-splitting incisions (n = 53) had been used to approach the terminal aorta or iliac arteries. Two types of muscle-dividing incisions had also been used: incisions through the eleventh intercostal space (n = 41) to approach the infrarenal aorta; and incisions through the eighth, ninth, or tenth intercostal space with division of the diaphragm (n = 19) to approach the suprarenal aorta. Data on incisional pain, lumbosacral neuritic pain, incisional hernia, and deforming abdominal bulge were culled from the records of follow-up examinations conducted on all patients during periods ranging from 2 to 48 months. Both types of muscle-dividing incisions used to expose the aorta were associated with a 23% (14/60) incidence of abdominal bulge, a 7% (4/60) incidence of incisional hernia, and, more important, a 37% (22/60) incidence of prolonged disabling pain. Thus, although retroperitoneal exposure may be the preferred or the safest approach to certain aortic lesions, its routine use via muscle-dividing incisions is not recommended when the proposed operation can be carried out equally well by the conventional midline transperitoneal approach.

Aorta, Abdominal↗
PubMed1992

Pregnancy complicated by hereditary spherocytosis.

Hereditary spherocytosis is a spectrum of inherited erythrocyte membrane defects that result in hemolysis and varying degrees of anemia. Among 50 pregnancies in 23 women with spherocytosis, maternal complications were infrequent except for anemia, and perinatal outcomes were generally good. In six women, blood volume expansion estimated by 51chromium-tagged erythrocytes was similar to that for normal pregnant women. Mean red cell survival measured during seven pregnancies in six women ranged at 30-90 days, consistent with the heterogeneity of this disorder.

Female↗
PubMed1991

Complications of percutaneous intra-aortic balloon pump use in patients with peripheral vascular disease.

Percutaneous intra-aortic balloon pump use may carry an increased risk for patients with peripheral vascular disease. To determine the incidence and types of associated complications, the medical records of 144 patients who underwent a total of 153 percutaneous intra-aortic balloon pump insertions were reviewed. Patients were divided into two groups. Group 1 was composed of 20 patients with a history of peripheral vascular disease. Group 2 was composed of 124 patients without such history; they underwent a total of 133 insertions. Nineteen major complications (12%) occurred, 12 in group 1 (60% of 20 insertions) and seven in group 2 (5% of 133 insertions). Major complications were further classified by their nature: embolic, occlusive, and technical. All three types of complications occurred more frequently in group 1. Embolic complications occurred more frequently in patients with aneurysms and proved the most lethal, with two of six deaths in group 1 resulting from this complication.

Aneurysm↗
PubMed1991

On reducing the frequency of severe abruptio placentae.

At Parkland Memorial Hospital the frequency of abruptio placentae so severe as to kill the fetus has decreased from 1 in 420 deliveries during 1956 through 1969 to 1 in 830 during 1974 through 1989. Major factors in this reduction were elimination of very high parity and a marked increase in the percentage of Latin American women, in whom the risk was 1 in 1473 deliveries compared with 1 in 595 for black women and 1 in 876 for white women. Abdominal trauma was encountered rarely, as was fetoplacental-to-maternal hemorrhage sufficient to impair fetal perfusion seriously. Abnormal development of Müllerian ducts and uterine myomas were encountered rarely. Neither red blood cell macrocytosis characteristic of folate deficiency nor iron deficiency could be implicated in the genesis of severe abruptio placentae. Abruptio placentae recurred in 12% of subsequent pregnancies and proved fatal to the fetus in 7%, unchanged from our earlier experience.

Abruptio Placentae↗
PubMed1991

Computerised axial tomography of the trachea. A useful investigation when a retrosternal goitre causes symptomatic tracheal compression.

Case histories are reported of three patients who had large retrosternal goitres which were responsible for significant abnormalities of the airway. Computerised axial tomography demonstrated the exact anatomy. The site of tracheal compression was shown and accurate measurements of the diameter of the trachea at its narrowest point were made. This information was useful when the management of the patient was planned.

Aged↗
PubMed1991

Indirect measurement of systolic blood pressure in the rabbit.

Long-term studies of rabbit blood pressure require a reliable method for repeated blood pressure measurements. Ideally, this method would be simple, noninvasive, and accurate over the range of anticipated blood pressures. To facilitate our own studies of rabbit carotid artery graft patency, we have developed a technique for the indirect measurement of systolic blood pressure in the rabbit that utilizes a photoplethysmograph sensor placed distal to an inflatable air bladder positioned over the central ear artery. We have compared measurements obtained with this method to direct measurements of aortic pressure and found a linear correlation.

Animals↗
PubMed1990

Chronic renal disease and pregnancy outcome.

During the 18-year period from 1971 through 1988, 37 women whose pregnancies were complicated by moderate or severe renal insufficiency were managed at Parkland Memorial Hospital. Common maternal complications included anemia, chronic hypertension, and preeclampsia. Perinatal complications included midpregnancy losses and low birth weight from preterm delivery, fetal growth retardation, or both. Despite the high incidence of maternal morbidity, 85% of pregnancies in the 26 women with moderate renal insufficiency resulted in a live-born infant; there was one stillbirth and no neonatal deaths. Of the 11 women with severe disease, seven were delivered of live-born infants after greater than or equal to 26 weeks' gestation. Although six of these 37 women had worsening renal function during pregnancy, it seems unlikely that pregnancy per se caused this. More importantly, in four of these six women and in four others who had stable function throughout pregnancy, end-stage renal disease developed within a mean of 4 years after delivery. In 14 women blood volume was determined during pregnancy, and whereas those with moderate disease had normal volume expansion, women with severe disease had significantly attenuated expansion. Finally, serial creatinine clearances did not increase during pregnancy in half the women with moderate insufficiency and none with severe dysfunction.

Anemia↗
PubMed1990

Transaortic endarterectomy of renal visceral artery lesions in association with infrarenal aortic surgery.

The complexity of infrarenal aortic reconstruction increases when bypass grafts to revascularize associated renal and visceral arteries are needed. Lesions in these vessels, however, are usually limited to their aortic orifices and therefore are amenable to retroperitoneal transaortic endarterectomy. A combined infrarenal aortic reconstruction and transaortic endarterectomy of the renal/visceral vessels was used in 18 (16%) of 120 patients undergoing elective infrarenal aortic reconstruction over a 2-year-period. Transaortic endarterectomy was performed primarily for renal preservation in 11 patients with bilateral, high-grade renal artery stenoses and abnormal renal function (serum creatinine greater than or equal to 1.9 mg/dl). In seven patients transaortic endarterectomy was performed as a secondary procedure during the course of complex reconstruction of aneurysmal or occlusive aortic disease. Mean serum creatinine, which was elevated preoperatively in 14 (78%) patients (3.3 mg/dl), decreased significantly after the operation (2.0 mg/dl, p less than 0.01). A single death occurred in the 18 patients undergoing transaortic endarterectomy. Renal function preservation can be achieved by renal revascularization in patients with bilateral renal artery stenoses and decreased renal function. The retroperitoneal approach to aortic reconstruction and the use of transaortic endarterectomy allows correction of most renal/visceral vessel involvement in complex aortic revascularization procedures.

Aorta, Abdominal↗
PubMed1990

Fiberoptic examination of the inferior vena cava during circulatory arrest for complete removal of renal cell carcinoma thrombus.

Renal cell carcinoma is known to invade the inferior vena cava and may extend its entire length. Profound hypothermic circulatory arrest has been demonstrated to be a very effective technique to facilitate removal of tumor thrombus from the cava while limiting the amount of blood loss. We describe an innovative method of ensuring complete removal of tumor thrombus from the retrohepatic cava with a fiberoptic bronchoscope introduced through the right atrium during profound hypothermic circulatory arrest. Fiberoptic examination of the cava and hepatic vein orifices under these circumstances will prevent incomplete removal of tumor.

Bronchoscopes↗
PubMed1990

The value of computed tomography in the management of symptomatic abdominal aortic aneurysms.

The use of computed tomographic (CT) scanning in the diagnosis of ruptured abdominal aortic aneurysm is controversial because the delay created by the procedure, it has been argued, may increase overall mortality. However, if emergency surgery can be avoided in the medically compromised patient, surgical results may improve. To assess the value of CT scanning, we studied the 1983 to 1988 records of 65 hemodynamically stable patients with abdominal aortic aneurysms, who underwent diagnostic CT scanning for acute abdominal or back pain. Twenty-one patients had a history of severe cardiac, renal, or pulmonary disease. The average duration of the examination was 63 minutes; no episodes of hypotension occurred. Subsequently, 17 of 18 patients with ruptured aneurysms had emergency surgery, with 31% morbidity and 29% mortality. Of 44 patients found to have nonruptured aneurysms, 13 had other causes for their pain, nine were not considered surgical candidates, and 24 had elective aneurysmectomies, with 8% morbidity and 0% mortality. In three patients CT scanning excluded the diagnosis of aneurysm. Additional information provided by CT scanning enhanced the safety of the perioperative management of four patients with rupture and 14 without. In conclusion, the delay imposed by obtaining a preoperative CT scan in patients with possible ruptured aneurysm did not adversely affect patient outcome, and the information obtained from it aided significantly in both preoperative and intraoperative management.

Aorta, Abdominal↗
PubMed1990

Pregnancy complicated by hemoglobin CC and C-beta-thalassemia disease.

The outcomes of 72 pregnancies in 20 women with either hemoglobin CC or C-beta-thalassemia are described. Except for mild to moderate hemolytic anemia, maternal complications caused by the hemoglobinopathy were infrequent and perinatal outcomes were generally good. In eight women, blood volume expansion determined by 51chromium-tagged erythrocytes was similar to that for normally pregnant women. Mean red-cell survival was determined 11 times in eight women, and the red-cell half-life of 22 days was significantly shorter than that of 35 days for normally pregnant women.

Black People↗
PubMed1989

The early and late responses of the arterial wall to graft placement.

The relationship between the early smooth muscle cell proliferative response (SMC-PR) to injury and the later development of myointimal hyperplasia (MIH) complicating arterial bypass grafts remains unclear. In the present study, the early SMC-PR and the later MIH induced by a 2-mm-diameter PTFE graft placed in a rabbit carotid were compared with the response induced by an autogenous artery (AA) graft in the contralateral carotid. The early SMC-PR was measured in the proximal and distal arterial segments 5 days after graft placement by in vivo labeling with [3H]thymidine to determine the DNA specific activity (DNA-SA). The later anastomotic MIH was measured 16 and 32 weeks postgrafting by calculating the intimal/medial ratio. There was a marked and similar increase in the early SMC-PR noted with both the AA and the polytetrafluoroethylene (PTFE) grafts. The distal segments demonstrated a significantly higher DNA-SA when compared to the proximal in both AA- and PTFE-grafted arteries. There was a moderate degree of anastomotic MIH noted in chronic grafts; however, a regression in intimal thickening was observed over time in the AA-grafted arteries, while the distal anastomosis of the PTFE-grafted vessels demonstrated a continuous progression of the MIH process. The early SMC-PR may abate in arteries grafted with autogenous grafts, but there is a persistent proliferative response at the distal anastomosis associated with synthetic grafts.

Animals↗