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Biomedical subjects

J D Laird

Publications and source records attributed to J D Laird.

17 recordsLinked to original sources
PubMed1992

Dynamic hepatic scintigraphy in the screening of psoriatic patients for methotrexate-induced hepatotoxicity.

We report the use of dynamic hepatic scintigraphy in the assessment of the hepatic status of psoriatic patients before and during methotrexate therapy. Eighty-seven paired dynamic scans and percutaneous liver biopsies were performed in 63 patients. The liver biopsies were graded according to Warin et al. with fibrosis of grade 2 or worse being a strong indication for withdrawal of methotrexate. The sensitivity of dynamic hepatic scintigraphy in detecting fibrosis of grade 2 or worse was 83.3% and the specificity was 81.5%. The predictive value of a normal scan for fibrosis of grade 0-1 was high (98.5%) although the predictive value of an abnormal scan for fibrosis of grade 2 or worse was low (25%). Dynamic hepatic scintigraphy may therefore offer a means to reduce the number of liver biopsies necessary in patients receiving methotrexate for psoriasis.

Adult↗
PubMed1989

Thallium-technetium isotope subtraction scanning in primary hyperparathyroidism.

Between January 1983 and March 1986, 75 consecutive patients underwent cervical exploration for primary hyperparathyroidism. Each patient had a thallium-technetium subtraction isotope scan of the neck performed preoperatively. Of 71 patients with technically satisfactory scans, 68 came to 'first-time' neck exploration while three underwent reoperation for persistent hypercalcaemia. At primary cervical operation 53 of the 68 patients each had a solitary adenoma as the cause of their hyperparathyroidism. In 28 (53%) of these individuals the scintigram accurately predicted the site of the parathyroid tumour ('helpful' scans). The technique was 'unhelpful' in 17 patients (32%) with false-positive scans and in eight patients (15%) with false-negative scans. There was a highly significant difference between the median weight of adenomas removed from patients with helpful scans (1.05 g) and that of adenomas retrieved from individuals with unhelpful scans (0.47 g), (P less than 0.001). Since 1 January 1985 we have adopted a policy of 'scan-directed' unilateral neck exploration for patients with hyperparathyroidism on the basis of solitary adenoma and in whom the isotope scan was positive. The mean operating time for these patients (n = 18, mean operating time 1.24 h) was significantly shorter than that for patients with unhelpful scans (n = 14, mean operating time 1.55 h, P less than 0.01) who were submitted to standard bilateral cervical operation. Subtraction scanning was helpful, in terms of localization of enlarged parathyroid glands, in only three of eight patients with multigland hyperplasia. The investigation was of positive help in locating the adenoma in two of three individuals submitted to cervical re-exploration for persistent hyperparathyroidism.

Adenoma↗
PubMed1988

99Tcm-MDP bone scanning of injuries of the carpal scaphoid.

Clinical injuries of the carpal scaphoid are frequently seen at accident and emergency departments. Some exhibit delayed radiographic visualization of a fracture. The radioisotope bone scan is a sensitive test and increased uptake is observed in healing fractures. Twenty-three patients with an initial diagnosis of clinical fractures of the scaphoid were studied clinically, radiologically and independently by 99Tcm-MDP isotope scans. Three-quarters of the patients required only 1 month's management. Their corresponding bone scans were normal or not suggestive of a fracture. The remaining 25 per cent, who clinically required a more prolonged treatment (greater than or equal to 5 weeks' immobilization), were noted independently to have positive scans whether a fracture was observed or not. It is concluded that there is a stronger correlation between clinical examination and a bone scan than with a standard radiographic examination. It is proposed that patients still tender at 3 weeks should have a carpal isotope bone scan to identify if there is an important wrist injury and appropriate treatment commenced.

Adolescent↗
PubMed1988

Quantification of arteriolar density and embolization by microspheres in rat myocardium.

We developed a technique for in vitro determination of arteriolar densities. Hearts, obtained from anesthetized rats and perfused by the Langendorff method, were fully dilated with adenosine and were arrested with an elevated potassium concentration. After a stabilization period, the hearts were perfused with a buffered fixative for some minutes to obtain a nonvital vasculature. After fixation, perfusion was switched back to control for some minutes. The hearts were then perfused with a medium containing a low concentration of microspheres: either pollen grains [Urtica dioica (15.4 microns), Betula (23.5 microns), or Phleum pratense (36.5 microns)] or polystyrene microspheres (15 microns). The perfusion was switched back to the standard medium after flow had been reduced to between 83 and 57% of control flow. Microscopic observations of microsections revealed that the percentages of arterioles embolized by one microsphere were 64% for the 15.4-microns, 74% for the 15-microns, 78% for the 23.5-microns, and 72% for the 36.5-microns microspheres. The percentages of arterioles embolized with two microspheres were 20, 15, 15, and 16%, respectively. The arteriolar densities were calculated from the total fractional reduction in coronary flow, the amount of microspheres injected, the wet heart weight, and the degree of occupancy, which corrects for the multiple embolization of the arterioles. The arteriolar densities in the rat hearts were 162.4 +/- 54.9 mg-1 (N = 6) for polystyrene microspheres of 15 microns, 161.5 +/- 81.1 mg-1 (N = 15) for 15.4-microns microspheres, 31.6 +/- 7.8 mg-1 (N = 9) for 23.5-microns microspheres, and 13.0 +/- 2.4 mg-1 (N = 8) for 36.5-microns microspheres.

Animals↗
PubMed1987

What is the significance of the abnormal oesophageal scintigram?

In a review of 52 oesophageal scintigrams carried out in 46 patients with a variety of oesophageal problems, there was no correlation between the results of this test and the findings in other tests of oesophageal function, or between the scintigram results and the patients' symptoms, with the possible exception of regurgitation. We conclude that the test is of little value.

Adolescent↗
PubMed1986

Indium-111 autologous leukocyte imaging in pancreatitis.

Thirty-nine patients with acute pancreatitis have been assessed using a prognostic factor grading system, abdominal ultrasound, and autologous leukocyte imaging. Both prognostic factor grading and leukocyte imaging can accurately assess the severity of the disease early in its course. All patients with a negative indium-labeled leukocyte image recovered without sequelae, whereas five of the 12 patients with a positive image developed complications, including two deaths. Abdominal ultrasound is of no value in assessing severity, but is a useful method of detecting those patients with gallstone-associated disease. In patients with suspected abscess formation following acute pancreatitis, indium leukocyte imaging does not differentiate between fat necrosis and abscess formation. In this situation, computerized tomography should be carried out before laparotomy is undertaken.

Abscess↗
PubMed1978

Transient oxygen uptake during myocardial reactive hyperemia in the dog.

Oxygen uptake during myocardial hyperemia (MRH) following occlusions of 2.5-30 s was studied in nine anesthetized open-chest dogs by continuous measurement of left anterior coronary blood flow and anterior coronary vein oxygen saturation with electromagnetic flowmeter and fiber-optic catheters, respectively. The ratio of excess oxygen uptake to debt multiplied by 100% was defined as the oxygen repayment ratio (RR) and varied between -50% and +150% (mean 78%). Application of a steady-state Fick formula, as used by previous investigators, results in a profound overestimate of the RR (70-400%, mean 295%). RR is severely distorted by the venous catheter system, and after consideration of these effects we would conclude that the "true" RR in MRH is even lower than we found. Comparing our results with steady-state exercise autoregulation leads us to the following conclusions: 1) chemical kinetic limitations in oxygen release by red blood cells are excluded, 2) a simple direct PO2 regulation of flow is unlikely, but 3) our results are not inconsistent with a more complex integral oxygen regulation or with the metabolic hypothesis.

Animals↗
PubMed1977

Effectiveness of intraaortic balloon pumping without cardiac surgery for patients with severe heart failure secondary to a recent myocardial infarction.

Twenty-five patients with class III or class IV left ventricular failure (Myocardial Infarction Research Unit criteria) after a recent myocardial infarction were treated with intraaortic balloon pumping between December 1, 1972 and December 1, 1976. Three patients had no improvement and died during pumping. Two patients with improvement died during at attempt at weaning from circulatory assistance. Of 20 patients successfully weaned, 6 died within 3 months, 5 of these within 10 days after the weaning procedure. Of 14 patients who survived for more than 3 months, 13 were alive on February 15, 1977. Twelve of these 13 were in functional class II and 6 had resumed professional activities. Intraaortic balloon pumping proved an effective method for treating severe left ventricular failure after an acute myocardial infarction. Even withour surgery, 14 of 25 patients survived 3 or more months after an acute infarction complicated by serious pump failure.

Adult↗
PubMed1977

The course of passive elasticity of myocardial tissue following experimental infarction in rabbits and its relation to mechanical dysfunction.

Given the substantial reserve of normal myocardium, its inability to sustain life in the presence of 30-50% necrosis of the left ventricle (LV) seems a paradox. It is known that dyskinesia of the infarcted area probably plays a dominant role in initiating failure after an infarction. To study this problem, a well defined experimental infarction was produced by cryogenic means in 58 rabbits, and the animals were allowed to recover. Groups of rabbits were killed 4 hours and 1,2,5, or 10 days following infarction. As quickly as possible (within 4 minutes) a sample specimen from the infarcted area was removed from the LV and subjected to a force-elongation test while being bathed in Ringer solution at 37 degrees C equilibrated with 95% O2-5% CO2. The data were interpreted assuming an exponential stress-strain law with constants K and C. Mean values of K of 10.6 +/- 0.94 (SEM) were found for the noninfarcted control group, whereas, rather surprisingly, no significant trend in K over 10 days was found in the infarcted group. Mean values of K +/- SEM for the postinfarction groups were as follows: 4 hours, 9.51 +/- 0.63; 1 day 10.54 +/- 1.13; 2 days, 13.15 +/- 2.28; 5 days, 11.59 +/- 1.36; and over 10 days, 12.93 +/-1.02. The functional implications were estimated with a simple model of the shortening required of the viable muscle during the isovolumic phase. It was found that contractile reserve fell rapidly with increasing infarct size, reaching zero for a 60% infarct when K = 10. With K greater than 100, there was no appreciable reduction in reserve. With a constant infarct size, variation in reserve with the afterload-preload ration was found to be logarithmic.

Animals↗
PubMed1976

Resolution problems in echocardiology: a source of interpretation errors.

Resolution is the ability of the echocardiographic system to distinguish closely lying structures. This is usually defined in two directions: laterally (lateral resolution) and in depth (axial resolution). With use of short ultrasonic pulses, axial resolution is not a major problem. By far the more important problem is the limited lateral resolution that results from the finite beam width of current ultrasonic devices. This results in the display of echoes that originate from off-axis structures. How these off-axis or "spurious echoes" affect the display is a function of the way the echographic information is handled. In conventional M-mode tracings, spurious echoes are displayed at a site where there is no directly corresponding anatomic structure, whereas with two-dimensional imaging, these echoes may result in important distortions of structures. The underlying principles are illustrated by a clinical experiment wherein the ball of a Starr-Edwards mitral valve prosthesis serves as a target of known shape and dimensions. These data are used to elucidate some of the problems and potential errors encountered in the interpretation of clinical M-mode recordings of the aorta, mitral valve and the left ventricular endocardium as well as their cross-sectional analysis. They also explain the present limitations of quantification of left ventricular performance from cross-sectional images.

Aorta↗
PubMed1976

Asymptotic slope of log pressure vs log volume as an approximate index of the diastolic elastic properties of the myocardium in man.

The goal of this study was to develop, on a rational basis, an index of the intrinsic diastolic elastic properties of the left ventricle. A relatively simple analytic model employing a thin-walled spherical geometry coupled with an approximate formulation of a two-dimensional constitutive relation, was used to examine the primary determinants of the pressure-volume relationship of the intact heart. The results permit comparison with other indices of compliance or wall stiffness. The slope of the dP/dV vs P curve was found to be sensitive to the non-linear elastic constant K, but is also sensitive to variations in cardiac muscle volume. VdP/dV was found to be sensitive to pressure. m = d(log P)/d(log V) = (V/P)(dP/dV) is proposed as an index sensitive to K and relatively insensitive to both pressure and initial cardiac geometry. The index is compared with published studies. Using the data of Fester and Samet, mean values of the asymptotic log-log P-V slope, m, evaluated at end-diastole for normal, idiopathic hypertrophy, mild, moderate and severe coronary artery disease were 3.95 +/- 0.60 (SEM), 5.05 +/- 1.60, 5.24 +/- 0.96, 8.35 +/- 2.06, and 15.13 +/- 3.0, respectively. At values of LVEDP less than 7 mm Hg the concept of simple distension is questioned. The advantages and limitations of this approximate index are discussed. This index seems to afford a practical measure of the elastic properties of the wall over a rather wide range of pressure, volume, wall mass and wall thickness.

Cardiac Output↗
PubMedDate not supplied

Scan-directed unilateral cervical exploration for parathyroid adenoma: a legitimate approach?

Thallium-Technetium isotope subtraction scanning was used routinely as a preoperative localization investigation in 90 patients with primary hyperparathyroidism who were submitted to "first-time" cervical exploration from 1985 to 1988. When the scintigram demonstrated a single focus of activity suggesting the site of a solitary parathyroid adenoma, a scan-directed exploration was carried out. If the tumor was found at the location suggested by the scan, it was then removed and the ipsilateral normal parathyroid was biopsied. The contralateral side of the neck was not explored in these patients. A total of 48 patients underwent unilateral cervical exploration while the remaining 42 individuals had a standard bilateral neck operation performed. The difference in operating times for patients who had a solitary adenoma and who underwent unilateral and bilateral neck exploration, respectively, was statistically highly significant (71 minutes versus 97 minutes, p less than 0.001). At mean follow-up of 16.8 months, no patient who had a unilateral neck exploration performed for solitary parathyroid adenoma demonstrated persistent or recurrent hypercalcemia.

Adenoma↗