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Biomedical subjects

R B Shafer

Publications and source records attributed to R B Shafer.

At least 55 records · Page 3Linked to original sources
PubMed1982

Effect of endotoxin fever on plasma clearance of thyroxine and tri-iodothyronine: concise communication.

Endotoxin-induced fever in rabbits causes a rapid decrease in serum T3, a reciprocal rise of 3,3',5'-tri-iodothyronine (rT3), and a less marked reduction in T4 with a rebound at 24 hr. To answer the question whether the alteration in hormone levels was the result of a decrease in T3 or T4 production and release or of an increase in T3 and T4 metabolism, we measured the disappearance of [125I]T4 and [125I]T3 during endotoxin-induced fever and externally applied heat. Results showed no significant difference in disappearance of [125I]T4 or [125I]T3. This suggests that the rapid change in T3 levels associated with endotoxin fever is due to an inhibition of thyroid production and peripheral conversion, and not to increased metabolism of hormones.

Animals↗
PubMed1982

Thyroid function screening in new psychiatric admissions.

Thyroid function screening may be of value in psychiatric patients. The present study was undertaken to determine the incidence of thyroid abnormalities in psychiatric patients during short-term admissions. Results of thyroid function tests disclosed an elevated free thyroxine index (FT4I) and free triiodothyronine index (FT3I) in 19% of 386 psychiatric patients during short-term admissions to Minneapolis Veterans Administration Medical Center. Elevated test results were particularly common in paranoid schizophrenics (38%) and in patients with amphetamine abuse (32%). On retesting, at two to three weeks after hospitalization, the FT4I and FT3I had returned to normal in 13 of 16 and 17 of 17 patients, respectively. Undiagnosed hypothyroidism was found in four patients with a diagnosis of manic-depressive psychosis on hospital admission. Serial sampling needs to be undertaken to assess the most appropriate time for thyroid function testing after short-term psychiatric admission.

Amphetamines↗
PubMed1981

Free thyroxine levels in critically ill patients. A comparison of currently available assays.

Two indices of free thyroxine (T4) and four methods of free T4 measurement were compared in 85 patients with acute illness, hospitalized in intensive care units. All of the methods of free T4 measurement in critical illness were nonspecific, and two of the methods failed to suggest hypothyroidism in two patients with primary hypothyroidism and another associated critical illness. Since the ideal screening test should be both sensitive and specific, all tests for free T4 used in this study should be interpreted with caution in severely ill patients.

Acute Disease↗
PubMed1981

Hypothyroxinemia in critically ill patients as a predictor of high mortality.

Thyroid function was measured in 86 patients hospitalized in an intensive care unit. Two patients were found to have primary hypothyroidism and were excluded from the study. Hypothyroxinemia with normal thyroid-stimulating hormone (TSH) levels was found in 22% of the patients and was associated with a high mortality (thyroxine [T4] levels less than 3.0 micrograms/dL, 84% mortality; T4 levels of 30 to 5.0 micrograms/dL, 50% mortality; and T4 levels greater than 5.0 micrograms/dL, 15% mortality). There was a high correlation between low T4 levels and mortality.

Adult↗
PubMed1981

Hepatic bioavailability of serum thyroid hormones in nonthyroidal illness.

Serum was obtained from 11 patients with nonthyroidal illness (NTI) and from 9 control subjects. Patients with NTI demonstrated decreased total T4 and T3 levels; increased rT3, T3 resin uptake, and percent free (dialyzable) T4 levels; and normal TSH and free T4 concentrations in vitro. In addition, the effects of control and patient sera on the first pass extraction of labeled T4 and T3 by rat liver was measured with a tissue sampling-single injection technique. The percent of total serum T4 and T3 that was transported into liver on one pass was 17 +/- 2% and 77 +/- 5%, respectively, in the case of NTI, and these values were no different from control estimates. The concentrations of total serum T4 and T3 available for transport into liver in vivo were 0.69 +/- 0.13 micrograms/100 ml and 21 +/- 2 ng/100 ml, respectively, in NTI, and these values were 46% and 18% of control values, respectively. Therefore, in contrast to in vitro estimates of free T4, in vivo measurements indicate the amount of circulating T4 or T3 that is available for transport into liver cells in NTI is reduced in proportion to the decrease in total plasma hormone.

Acute Disease↗
PubMed1981

The role of Tc-99m phosphate complexes and gallium-67 in the diagnosis and management of maxillofacial disease: concise communication.

Osteomyelitis of maxillofacial bones is difficult to differentiate from the results of trauma or malignancy, yet successful management is dependent upon early diagnosis and appropriate therapy. To determined if gallium-67 could differentiate infection from trauma or malignancy, 61 Tc-99m phosphate scans and 52 gallium-67 scans were made in 42 patients with maxillofacial disease. In all patients, definitive diagnosis was determined by surgery and/or clinical followup. Bone scans were positive in 37 patients. Gallium-67 scans were positive in 16 patients. Subsequent surgery and/or clinical followup demonstrated active osteomyelitis in 15 patients. From the data we conclude that: (a) the addition of Ga-67 scanning to the bone scans in evaluation of maxillofacial disease contributes significantly to differentiating trauma from osteomyelitis; (b) radiographic changes do not accurately reflect bone activity or differentiate osteomyelitis from trauma or malignancy; and (c) reduction in accumulation of gallium-67 in followup scans is a useful indicator for the termination of therapy in osteomyelitis.

Adult↗
PubMed1980

Effect of hemodialysis on gallium-67-citrate scanning.

Gallium-67-citrate scanning is often used in the diagnosis of inflammatory processes in hemodialysis patients. The question arises whether the dialysis process will adversely affect the quality of the gallium scan. To answer this question, nine dialysis patients were studied, eight on hollow-fiber dialysis units and one on ultrafiltration, in an attempt to quantitate the loss of gallium through dialysis. Blood sampling during dialysis failed to demonstrate changes in gallium concentration attributable to removal by dialysis. Sampling of dialysate demonstrated levels of activity significantly greater than background; however, quantitation was not reliable. Ultrafiltration with total collection of extracted fluids yielded 0.5% of injected dose removed from the blood. Whole-body scans at 24 hours postinjection showed good quality and total counts unaltered by dialysis. The time of injection prior to dialysis also showed no effect on the quality of the final image.

Citrates↗
PubMed1980

Angiotensin infusion effects on left ventricular function. Assessment in normal subjects and in patients with coronary disease.

Radionuclide multigating of the cardiac cycle was employed to assess effects of angiotensin infusion on left ventricular function. In six normal subjects, angiotensin infusion decreased heart rate (HR) from 72 +/- SEM 2 to 57 +/- 2 beats/min (P less than 0.001); while systolic blood pressure (BP) increased from 119 +/- 2 to 178 +/- 1 mm Hg (P less than 0.001), and ejection fraction (EF) declined from 58 +/- 1 to 47 +/- 2 percent (P less than 0.05). In contrast, in 11 normal subjects, supine exercise increased HR and systolic BP by 55 and 49 percent, whereas EF increased from 64 +/- 1 to 71 +/- 1 (P less than 0.001). In ten patients with CAD, angiotensin infusion produced no change in HR, increased systolic BP by 34 percent, and decreased EF by 11 percent. Angiotensin infusion induced left ventricular depression in normal subjects and in patients with CAD. It cannot substitute for exercise in intervention radionuclide ventriculography.

Adult↗
PubMed1980

Comparison of gated radionuclide scans and chest radiographs. Assessment of left ventricular impairment in patients with coronary disease.

Diagnostic efficacy of gated cardiac blood pool imaging was studied in 41 consecutive patients with LV ejection fractions (LVEF) less than or equal to 0.50. Eighty percent of patients were receiving therapy for LV failure at the time of the study. All patients had documented coronary-artery disease (CAD). Chest x-ray films were interpreted blindly by a senior radiologist. Cardiothoracic ratio of less than or equal to 0.50 was recorded as normal. Radionuclide assessment of LV function contributes importantly to the diagnostic and screening value of chest x-ray films. Patients with coronary disease and clinical evidence of heart failure should have radioisotopic studies even if chest x-ray film findings are normal. In patients with coronary artery disease and enlarged LV on chest films, radionuclide study of left ventricular performance aids in defining LV impairment, and in the prognostication of subsequent clinical course.

Adult↗
PubMed1980

Assessment of cardiac reserve in patients with hyperthyroidism.

Radionuclide multigated cardiac imaging was performed to assess functional cardiac reserve in patients with hyperthyroidism. In 11 normal individuals, submaximl supine exercise increased heart rate (HR) by 60 percent, systolic blood pressure (BP) by 54 percent, and the left ventricular ejection fraction (LVEF) by 13 percent. All of these increments were statistically significant (p < 0.001). Eight patients with hyperthyroidism were studied. Their mean +/- standard error of the mean (SEM) serum thyroxine level was 17.7 +/- 0.5 micrograms percent. There was a negative correlation between serum thyroxine levels and LVEF, both at rest and during exercise, in the patients with hyperthyroidism. Our data suggest that hyperthyroidism is associated with impaired functional cardiac reserve.

Adult↗
PubMed1980

Amphetamine-induced hyperthyroxinemia.

Four patients had high serum thyroxine (T4) concentrations during periods of heavy amphetamine abuse. After amphetamine was withdrawn, serum T4 returned to normal. Administration of amphetamine to monkeys induced a rise in serum T4; in this model the high T4 level appeared to be caused by increased serum thyrotropin. The mechanism of this effect is unclear but is presumably mediated via the hypothalamus. Awareness of transient hyperthyroxinemia due to amphetamine may allow the physician to avoid confusion with true thyrotoxicosis.

Adult↗
PubMed1980

Effects of fever and hyperthermia on thyroid function.

Thyroid hormones in man are affected by acute and chronic febrile states. To define these acute changes, we used a previously described rabbit model. Serum levels of T3, rT3, and T4 were measured at 0, 2, 4, 6, and 24 hr following injection of 1 microgram E. coli endotoxin, and during heat-induced hyperthermia. All rabbits receiving endotoxin developed fever with peaks at one hour (delta T = 1.1 degrees C) and three hours (delta T = 1.4 degrees C); they then defervesced to base levels at 6 hr. Similar temperature elevations occurred with heat-induced hyperthermia. Results show that endotoxin-induced fever produces changes similar to those reported during infections to man, and more rapidly than previously recognized. These include a prompt decrease in T3, reciprocal rise in rT3, and an initially reduced T4 that rebounds above basal levels. These findings may represent suppressed TSH release, alteration of peripheral monodeiodination of T4 from T3 to rT3, or enchanced clearance of T3. Heat-induced hyperthermia, except for slight decrease in T4 at 6 and 24 hr, had little effect on thyroid hormones.

Animals↗
PubMed1979

Assessment of left ventricular function in aortic insufficiency using echocardiography, gated scintigraphy and contrast angiography.

Echocardiography, gated scintigraphy and contrast angiography were used to measure left ventricular ejection fractions in 20 patients with varying degrees of aortic insufficiency. There was good correlation between the radionuclide and the angiographic ejection fractions. Echocardiographic ejection fraction correlated less well with the angiographic ejection fraction. The radionuclide left ventricular ejection fraction may prove valuable in the noninvasive serial evaluation of left ventricular function in patients with chronic aortic insufficiency.

Adult↗
PubMed1979

Abnormal images of right heart disorders.

Increasing attention is being given to radioisotopic studies of the right heart. Measurement of right ventricular ejection fraction has become more common. We present examples of cardiac images which were obtained during the scintigraphic assessment of right sided cardiac disorders. Images of the first pass, of the gated cardiac study, and of the nongated cardiac blood pools offer complementary information to the overall radionuclide evaluation of right heart disease.

Blood Pressure↗
PubMed1979

Radionuclide left ventricular dV/dt for the assessment of cardiac function in patients with coronary disease.

To investigate potential uses of left-ventricular (LV) systolic ejection rate (LV dV/dt) in the evaluation of LV function, we examined the effect of exercise, angiotensin, and leg raising on LV ejection fraction and LV dV/dt in patients with coronary-artery disease. The following observations were made: a) LV ejection fraction and dV/dt changed proportionately, but in opposite directions, during supine exercise; b) LV ejection fraction and dV/dt decreased to a similar extent during angiotensin infusions; and c) LV ejection fraction and dV/dt were unchanged by leg raising. The changes in peak and mean LV dV/dt were similar. Regardless of the physiologic state, peak LV dV/dt occurred during the first third of systole. These data imply that in this population there were no specific advantages of LV dV/dt over LV ejection fraction in the evaluation of LV performance.

Angiotensin II↗