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PubMed1984

Measurement of skin and total blood flow to the rabbit lower limb by washout of freely diffusible radioactive tracers introduced intra-arterially.

Good agreement was obtained when measuring total (capillary) blood flow in 9 rabbit thighs using two different techniques. The 133Xenon washout technique yielded a mean value of 8.0 cm3 X min-1 X 100 g tissue-1 whilst the microsphere technique gave a mean value of 7.8 cm3 X min-1 X 100 g tissue-1. There was a significant correlation (r = 0.83, p less than 0.006). In a further 14 rabbit thighs an attempt was made to measure skin blood flow by washout of 85Kr and to compare it with the microsphere technique. 133Xe promises to be a useful tracer for measuring lower limb flow when introduced intra-arterially. Because 85Kr tends to underestimate skin blood flow, and because of problems of diffusion of the tracer between compartments, which are discussed, this tracer is not satisfactory as a technique for measuring skin blood flow.

Animals↗
PubMedDate not supplied

Frequency of pulmonary embolism in patients admitted with chest pain and suspicion of acute myocardial infarction but in whom this diagnosis is ruled out.

The purpose of this study was to determine the frequency of pulmonary embolism in patients admitted with acute chest pain but without myocardial infarction (non-AMI patients). We examined 175 consecutive non-AMI patients without unstable angina pectoris within the first 48 h of admission. The patients were first examined by perfusion pulmonary scintigraphy. If the scintigraphy was abnormal, it was combined with a 81mKr ventilation scintigraphy. Perfusion scintigraphy was abnormal in 21 patients, and the subsequent combined perfusion/ventilation scintigraphy was used to identify 5 patients (2.5%) who had a high probability for pulmonary embolism, which was not clinically suspected at the time of admission. Three of these 5 patients had a decreased arterial oxygen tension upon admission, and 3 had abnormalities in their electrocardiogram. Pulmonary embolism only occurred in 2.5% of the non-AMI patients. The prognosis of untreated patients, however, it markedly worse as compared with treated patients. We, therefore, suggest that pulmonary scintigraphy be performed in non-AMI patients who have uncharacteristic electrocardiographic changes and/or a low arterial partial oxygen tension when no other abnormality has been found within 24 h of admission.

Adult↗
PubMed1976

Endometrial blood flow in rats.

The endometrial blood flow was measured in rats by injections of 85Kr saline into aorta and measurements of the clearance of the radioactivity by a Geiger-Müller probe situated in the uterine lumen. Estrus and diestrus were determined by vaginal smears. The endometrial blood flow was found to be 0.88 +/- 0.08 (mean +/- SEM) ml/g tissue/min in estus and 1.60 +/- 0.15 mg/g/min in diestrus. The experiment indicates that the endometrial blood flow and the total uterine blood flow change in opposite directions during the estrous cycle.

Animals↗
PubMed1988

Right-ventricular contractility in chronic obstructive pulmonary disease: a combined radionuclide and hemodynamic study.

The effect of pulmonary artery hypertension on right-ventricular performance in patients with chronic obstructive pulmonary disease (COPD) is unclear. Decreased values of right-ventricular ejection fraction (RVEF) have been reported, but most patients with stable COPD are not in cardiac failure and have normal or even increased cardiac outputs. We therefore hypothesized that RVEF may be afterload dependent, and thus a poor parameter of cardiac function, and that right-ventricular contractility may be normal even in COPD patients with pulmonary hypertension. We therefore studied 24 COPD patients using a combined hemodynamic and radionuclide approach. RVEF and thermodilution stroke volume index were measured simultaneously at rest in all 24 patients and also during bicycle ergometry in 9 patients. We then calculated end-diastolic and end-systolic volume indices and derived right-ventricular systolic pressure-volume relations in all and the slopes (E) of the pressure-volume line in 9 patients. RVEF was normal in COPD patients without pulmonary hypertension, but was reduced in those with pulmonary hypertension. A strong inverse linear relation between RVEF and mean pulmonary artery pressure (r = -0.73; p less than 0.001) and pulmonary vascular resistance (r = -0.69; p less than 0.001) could be demonstrated, indicating RVEF to be highly afterload dependent. Right-ventricular end-diastolic volume index was significantly higher in patients with pulmonary hypertension, indicating increased preload as the major mechanism to maintain adequate stroke volume in the face of an increased afterload. Right-ventricular end-systolic pressure-volume relations, a good parameter to define right-ventricular contractility independent of systolic loading conditions, were not different between COPD patients with or without pulmonary hypertension, nor did the slopes of the pressure-volume lines in the 9 patients studied during exercise show any difference. From these data we conclude that (a) RVEF is a poor indicator of overall right-ventricular function; (b) right-ventricular contractility is well preserved in stable COPD patients; (c) the major mechanism of maintaining stroke volume in the face of increased right-ventricular afterload seems to be preload augmentation.

Blood Pressure↗
PubMed1978

Unilateral kidney blood flow measurement using the 81Rb/81mKr ratio.

A new method has been developed for the continuous quantification of kidney blood flow, utilizing the unique physical and biological properties of the radioactive tracer couple: rubidium-81/krypton-81m. After intravenous injection, 81Rb concentrates primarily in the kidneys, where it continuously generates the radioactive inert gas 81mKr. This ultrashort-lived isotope is continuously washed out from the tissue at a rate proportional to the blood flow. The radiation emitted from within the kidney is externally detected and analyzed to yield the 81Rb/81mKr ratio. 21 animal experiments have confirmed that this ratio is at any time an accurate measure of the kidney perfusion. The 81Rb/81mKr ratio method has proved to provide a non-invasive way to selectively quantify the blood flow in each kidney, to monitor perfusion changes and to image the distribution of blood flow in a functional scintigram.

Animals↗