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Biomedical subjects

N Milne

Publications and source records attributed to N Milne.

35 records · Page 2Linked to original sources
PubMed1990

Exercise-induced changes in left ventricular function after phlebotomy in patients with polycythemic COPD.

The exercise capacity of polycythemic COPD patients has been shown to improve after phlebotomy, possibly because of reduction of ventricular afterload by decreased blood viscosity, resulting in increased cardiac output. Ten patients with polycythemic COPD and mean hematocrit 62% were studied at rest and during exercise before and after reduction of mean hematocrit to 50% by repeated phlebotomy. Pulmonary function was evaluated by physiologic exercise testing on a bicycle ergometer. Cardiac function was evaluated by rest and exercise RNVG. Significant increase in exercise tolerance and maximal oxygen uptake at peak exercise, with significant reduction in mean systemic BP, were demonstrated. Ejection fractions did not change, but dV/dt for ejection from the left ventricle at peak exercise improved significantly. Mean SV counts, ESV counts, and EDV counts were measured and the fractional increase with exercise compared for prephlebotomy and postphlebotomy, assuming that resting volumes would not change. ESV counts and EDV counts were both proportionately, though not significantly, reduced postphlebotomy. The data tend to support the hypothesis that the afterload on the left ventricle is reduced, with resulting improved myocardial contractility and left ventricular function. Improved peripheral oxygen uptake may also be a factor.

Cardiac Output↗
PubMed1990

Exercise performance of polycythemic chronic obstructive pulmonary disease patients. Effect of phlebotomies.

The purpose of this study was to determine the effects of phlebotomy on the exercise tolerance and right and left ventricular ejection fraction of polycythemic patients with chronic obstructive pulmonary disease. Ten patients with COPD (mean FEV1 = 1.32 +/- 0.55 L) and polycythemia (mean Hct = 62 +/- 3 percent) were studied before and after their hematocrits had been reduced to approximately 50 percent. Post-phlebotomy the maximal oxygen consumption increased from 1.09 +/- 0.34 L/min to 1.26 +/- 0.43 L/min (p less than 0.05) and the maximum workload increased from 56.5 +/- 32.6 watts to 74.5 +/- 23.4 watts (p less than 0.05). The increase in the exercise tolerance appeared to be primarily due to an increased cardiac output at Emax. There was no relationship between the increases in the upright exercise capacity and changes in the supine ejection fractions of the right or left ventricular either at rest or during exercise.

Aged↗
PubMed1990

Sexing of human hip bones.

Eight measurements of the hipbone were taken from 62 human skeletons of unknown sex. The subjective judgements of eight experienced anatomists were used to obtain subsets of male, female and unknown sex specimens. Principal components analysis was employed as a group-finding procedure; this confirmed the subjective determinations. Discriminant function analysis, using the subjectively determined 'known' specimens, was conducted. This yielded scores which sexed the unknown subset in agreement with the groups found by principal component analysis. Further discriminant functions were calculated to exclude two hip bone measures which were shown to be poor indicators of sex. The specimens with discriminant function scores closest to the cut-off point were seen, in the graph of the first two principal components, to lie in a cluster intermediate between the main gender groups and, upon re-examination, these were found to be rather ambiguous specimens with small overall measures and a narrow sciatic notch and pubis. The results of this study indicate that mid-pubic width is a more useful sexing character than pubic length.

Acetabulum↗
PubMed1988

Quantitation and fractionation of nutrient hepatic blood flow in normal persons, in persons with portal hypertensive cirrhosis, and after small-diameter portacaval H grafts.

Patients maintaining portal perfusion following small-diameter portacaval H grafts have better survival and lower portasystemic encephalopathy rates than those with reversed flow. To determine why this is so, we measured nutrient hepatic blood flow with the use of 99m-Tc-diisopropyl-IDA (DISIDA) clearance pharmacokinetics fractionated into its hepatic arterial and portal venous components. Patients with cirrhosis and portal hypertension had significantly lower nutrient hepatic blood flow than normal persons; this was due almost entirely to reduced portal flow. In patients with prograde portal flow after small-diameter H grafts nutrient hepatic blood flows were nominally reduced from levels seen in patients with portal hypertensive cirrhosis. Postoperative patients with reversed portal flow had significantly less nutrient hepatic blood than those with prograde flow. There was no evidence of significant hepatic arterial compensation for lost portal flow. Of four hemodynamic variables--portal flow direction, portal flow, arterial flow, and nutrient hepatic blood flow--only nutrient hepatic blood flow showed an independent correlation with clinical outcome. Portal perfusion is a critical factor in maintenance of adequate nutrient hepatic blood flow, primarily because hepatic arterial flow does not compensate chronically for lost portal perfusion.

Hemodynamics↗
PubMed1987

Computer analysis of portal hemodynamics after small-diameter portacaval H-grafts: the theoretical basis for partial shunting.

We have previously reported on the clinical results of partial shunting using small-diameter portacaval H-grafts. In this study, we defined the theoretical basis for partial shunting using the Wheatstone bridge model of the splanchnic circulation. The model was modified to include a variable resistance for a portacaval shunt and was programmed as a computer simulation. We calculated portal flow as a function of shunt resistance to determine the resistance necessary to maintain prograde portal flow in patients with portal hypertension. The resistance of 8- and 10-mm portacaval H-grafts, as positioned clinically, was determined using a laboratory apparatus. The experimentally derived values for resistance were inserted into the graph of portal flow predicted by the computer program. Portacaval H-grafts 8 mm in diameter should produce prograde portal flow, 10-mm H-grafts should be borderline, and shunts larger than 10 mm should routinely result in reversed flow. These predictions were confirmed by clinical observations in 29 patients undergoing portacaval H-grafts.

Computer Simulation↗
PubMed1987

Myocardial infarct imaging in patients with technetium-99m 2,3-dimercaptosuccinic acid. Superiority of technetium-99m pyrophosphate.

Technetium-99m 2,3-dimercaptosuccinic acid (Tc-99m DMSA) has been used successfully for imaging acute myocardial infarction in a canine model. The application in humans, however, has not been previously reported. In order to determine the feasibility of using this agent in clinical studies and to compare the agent to technetium-99m pyrophosphate (Tc-99m PPi), ten patients with proven myocardial infarction were studied. While imaging of transmural infarctions in humans was achieved using Tc-99m DMSA, scores for the Tc-99m DMSA images (1.8 +/- 0.96) were not as high as for Tc-99m PPi (2.5 +/- 0.45) (P less than 0.05). Discordance among four independent interpreters was greater for images obtained with Tc-99m DMSA. The superiority of Tc-99m PPi was evident whether images were obtained early (within 24 hours) or late (within five days). Although DMSA images were not obscured by rib uptake, they were less sensitive (63%) than Tc-99m PPi (97%). A potential advantage of Tc-99m DMSA in imaging acute myocardial infarction is that radiotracer concentration in the infarct occurs primarily in the early postinfarction period. The longer postinfarction that Tc-99m DMSA imaging was attempted, the lower the concentration of radiotracer. Thus, Tc-99m DMSA would not be expected to have the same persistence pattern as Tc-99m PPi into the remote postinfarction period. The persistent positivity of Tc-99m PPi has made it difficult to diagnose reinfarction.

Aged↗
PubMed1987

Metoclopramide-induced normalization of impaired gastric emptying in spinal cord injury.

In a partial, two-way crossover study of gastric emptying (GE) in spinal cord injury (SCI), fasted, healthy, unmedicated male volunteers were given a 99mTc-labeled liquid meal on two occasions. Metoclopramide (10 mg) was administered intravenously to each subject before the second evaluation of GE. We used single and multiexponential models with linear and nonlinear least-squares regression techniques to study the time-course of the disappearance of 99mTc from the stomach. The GE pattern in all subjects was most accurately characterized by nonlinear analysis (NONLIN) and consisted of two components, an initial adynamic phase and a phase of rapid emptying. The GE t1/2 of a liquid meal decreased from 106.6 +/- 58.3 min (mean +/- SD) in all SCI subjects (quadriplegic plus paraplegic) prior to treatment to 21.6 +/- 8.2 min after the intravenous administration of metoclopramide (p less than 0.006). Significant correlations between GE t1/2 and injury duration (yr) or level of spinal injury were observed. Impaired gastric emptying in SCI can be pharmacologically modified by metoclopramide to resemble a normal gastric emptying profile. Metoclopramide-altered gastric emptying in SCI may be expected to result in changes in the therapeutic efficacy of orally administered drugs when drug absorption is dependent on gastric motility or emptying efficiency.

Analysis of Variance↗
PubMed1986

Serial measurement of portal hemodynamics after partial portal decompression.

In a serial analysis of splanchnic hemodynamics, we compared partial with total portal decompression in 16 alcoholic cirrhotic patients who underwent portacaval shunts for variceal hemorrhage. Partial decompression was achieved with 8 or 10 mm polytetrafluorethylene portacaval H grafts and aggressive collateral ligation. Total decompression was achieved with larger diameter H grafts (12 or 14 mm). Early and follow-up (mean interval, 18 months) postoperative studies of portal hemodynamics included: direct measurement of shunt gradients, scintigraphic quantitation of portal and mesenteric flow distribution to the liver, and a portal and splenic collateral scoring system developed from standardized splenic venography. Partial portal decompression reduced portal pressure by 43% +/- 8% compared with 81% +/- 5% after total decompression (p less than 0.01). Scintigraphy demonstrated that partial decompression provided a greater fraction of portal flow to the liver than did total decompression (57% +/- 9% versus 2% +/- 1% intrahepatic radioactivity) and mesenteric flow distribution (14.5% +/- 5.4% versus 1.2% +/- 0.7%). Only one patient with partial decompression had a significant loss of portal perfusion during the interval studies. Significantly more residual collaterals were visualized in patients with partial decompression than in those with total decompression, and interval studies showed no significant changes from early studies. We conclude that partial decompression maintains higher portal pressures, more residual collaterals, and a greater fraction of portal and mesenteric flow to the liver than does total decompression. A modest but uniform reduction of portal pressure minimizes stimulus for new collateral formation and further shunting of portal flow.

Collateral Circulation↗
PubMed1984

Effects of digoxin on exercise capacity and right ventricular function during exercise in chronic airflow obstruction.

We evaluated 12 patients with stable chronic airflow obstruction (CAO) and no clinical evidence of left ventricular disease to determine the effects of oral digoxin on exercise capacity (VO2 max) and on right ventricular pump function during exercise. In this randomized, double blind, placebo controlled, cross-over study, patients performed exercise tests and underwent measurement of ejection fractions after two weeks of therapy with oral digoxin (0.25 mg/day) and after two weeks of placebo. Incremental upright exercise testing to a symptom-limited maximum was performed on a cycle ergometer. Right and left ventricular ejection fractions (RVEF, LVEF) were obtained in the supine position at rest and at approximately 75 percent of the maximum workload by gated equilibrium radionuclide angiography. All patients had abnormal right ventricular function, manifested either by a low resting RVEF (less than 45 percent) or a subnormal response to exercise (less than 5 percent increase). The small increases in RVEF with digoxin (mean +/- SE) at rest (44 +/- 5 vs 41 +/- 4 percent) and during exercise (46 +/- 4 vs 44 +/- 3 percent) did not achieve statistical significance. With digoxin, small increases in exercise duration (10.0 +/- 1.5 vs 9.0 +/- 1.4 min), maximum workload achieved (48 +/- 6 vs 42 +/- 5 W), VO2 max (0.85 +/- 0.06 vs 0.81 +/- 0.06 L/min), and oxygen-pulse (O2-P) (6.6 +/- 0.5 vs 6.3 +/- 0.4 ml/beat) occurred. Only the increase in O2-P was significant (p less than 0.05). From this study we conclude that digoxin does not significantly improve exercise capacity in severe chronic airflow obstruction with impaired right ventricular function, nor does it improve RVEF either at rest or during supine submaximal exercise.

Digoxin↗
PubMed1982

Stress myocardial imaging in patients with mitral valve prolapse: evidence of a perfusion abnormality.

Twenty-four patients with mitral valve prolapse underwent cardiac catheterization, exercise testing, and exercise 201thallium scintigraphy. Of 10 patients with coronary artery disease, six had abnormal scintigrams. Two of these six had exercise-induced reversible defects, two had defects that persisted during redistribution, and two had both reversible and persistent defects. Of 14 patients with normal coronary arteries, five had negative scintigrams. Of the remaining nine patients, two had exercise-induced defects, and seven (50%) had defects involving the inferior or posterior wall that persisted during redistribution. Possible mechanisms for this latter finding are discussed. In contrast to previous reports, exercise 201thallium scintigraphy was not entirely successful in identifying patients with coronary artery disease in our patients with mitral valve prolapse.

Adult↗
PubMed1981

Imaging of experimental myocardial infarction with technetium-99m 2,3-dimercaptosuccinic acid.

We have studied the use of Tc-99m-labeled 2,3-dimercaptosuccinic acid (Tc-99m DMSA) to scintigraph acute myocardial infarction after coronary occlusion in dogs. Optimal images were obtained 5 hr after injection of radiotracer, with consistent delineation 48 hr after occlusion. Delivery of tracer was dependent on blood flow. Uptake of tracer correlated to extent of infarction as determined by the myocardial depletion of creatine kinase. Myocardial Tc-99m DMSA was protein-bound.

Animals↗
PubMed1978

Brain scan diagnosis of central nervous system involvement in systemic lupus erythematosus.

Twenty-five patients with 29 episodes of active systemic lupus erythematosus with central nervous system involvement were studied according to a uniform protocol. Brain scans were found to be abnormal in all patients studied, and electroencephalograms were abnormal in 20/25 patients. Serial brain scanning was found to be useful in the diagnosis of exacerbations and the monitoring of corticosteroid dosage.

Adult↗
PubMed1975

Dural fluid collections in infants and children. A successful nuclear medical approach.

The authors describe their experience in 94 cases of dural fluid collections. The correct diagnosis was made in 94%, which is attributed to (a) including radionuclide angiography and both an immediate and a two- to four-hour delayed scan for every patient undergoing brain studies, (b) a high index of suspicion, and (c) simultaneous interpretation of the scan and the skull film. The false-positive rate was 10%, as shown by cerebral angiography.

Brain Diseases↗
PubMedDate not supplied

Geometric morphometric study of population variation in indigenous southern African crania.

Much of our understanding of population variation in southern Africa is derived from traditional morphometric research. In the search for new perspectives, this paper reports on new geometric morphometric data examining cranial variation in 12 modern human populations from southern Africa. In total, 298 male Bantu-speaking individuals were studied. In addition, a small Khoisan (Khoikhoi and San) series was also examined. The purpose of this study was to investigate Khoisan-Bantu morphological similarities and differences, and to examine variation within both the Bantu-speaking and Khoisan populations. The three-dimensional coordinates of 96 landmarks were analyzed, using the shape-analysis software morphologika. Interpopulation variation was examined by calculating Procrustes distances between groups; a cluster analysis was then used to summarize phenetic relationships. A principal components analysis explored the relationships between populations; shape differences were visualized and explored using three-dimensional rendered models, and further interpreted using thin-plate splines. Morphological differences are present within and between the crania of Bantu-speaking and Khoisan individuals. The Khoisan demonstrate features (e.g., a pentagonoid vault, more rounded forehead contour, and a small and less prognathic face) that clearly distinguish them from Bantu-speaking populations. Although southern African Bantu-speaking populations are clearly closely related, they show population-specific features (e.g., the crania of more southerly populations (Xhosa, Southern Sotho, and Zulu) are characteristically more brachycephalic and less prognathic). This study suggests that differential admixture with adjacent Khoisan peoples has contributed to diversity within southern African Bantu-speaking populations.

Africa, Southern↗