Effects of intra-atrial injection of colored microspheres on systemic hemodynamics and regional blood flow in rats

Abstract

The hemodynamic effects of various numbers of colored nonradioactive microspheres (CMS) and those of accumulation of CMS caused by multiple sequential injection were evaluated in 51 Sprague-Dawley male rats. CMS (15 microns) were injected into the left atrium. Regional blood flow and cardiac output were evaluated using the reference blood sample technique. Ficoll-70 was given after each blood sample withdrawal as a fluid replacement. A bolus injection of < or = 1,000,000 CMS caused no significant hemodynamic disturbances. Amounts of 500,000 CMS can be repeatedly injected up to four times (cumulative dose of 2,000,000 CMS) without producing any adverse hemodynamic effects. The values of cardiac output obtained with the CMS technique were correlated well (r = 0.971, P < 0.0001) with those obtained with electromagnetic flow probes. An excellent reproducibility of organ blood flow was observed after four sequential injections of 500,000 CMS. This study establishes the limits of CMS that can be injected into the rat without inducing hemodynamic changes and also suggests that the CMS technique can be employed to evaluate cardiac output and regional blood flow precisely and repeatedly.

The use of coloured dye‐extraction microspheres to measure blood flow in rabbit skeletal muscle: a validation study with special emphasis on repeated measurements

“…Ideally, microspheres should be injected into the left atrium for two-chamber mixing of the spheres (Heymann et al 1977;Kobayashi, Kobayashi, Kouno, Horinaka & Shigeru, 1994). In the present study very good mixing was achieved with atrial injection of the spheres.…”

“…Since the heart may be affected by a sudden decrease in temperature we prewarmed all injected solutions. In addition, the volume of spheres was kept to a minimum and injected over a period of 30 s to 1 min to limit the possible eflects of stretch of the ventricular wall and changes in haematocrit (Kobayashi et al 1994). To minimize loss of blood volume, we shortened the withdrawal time to 30 s after completion of the injection instead of 1 min; this reduction could be accommodated, because the complete circulation time in a rabbit is approximately 10.5 s (Green, 1979).…”

Hemodynamic and tissue blood flow responses to long-term pneumoperitoneum and hypercapnia in the pig

“…Cardiac output and blood flow changes in peritoneum and gastrointestinal organs during 10-mmHg helium (He) and carbon dioxide (CO 2 ) pneumoperitoneum factors (e.g., the angle of the probe and the ability to repeat measurements at the same site of the tissue under study). Blood flow measurements using both colored and radiolabeled microspheres have been extensively validated and shown to yield reliable and similar results in various tissues [4,8,12]. Moreover, this approach provides the opportunity to measure blood flow in a large part of the peritoneum.…”

Validation of transit-time flowmetry for chronic measurements of regional blood flow in resting and exercising rats

“…The transit-time technology for measuring dynamic changes of regional blood flow has several advantages over other methods such as electromagnetic, microsphere and Doppler system flowmetry: 1) small probe size permitting easy implantation; 2) continuous measurement of absolute blood flow representing an enormous advantage over phasic (microspheres, dye dilution) (3,22,23) or relative measurements (3,4,8-10); 3) probes are nonconstrictive and therefore do not interfere with the pulse pressure or percentage of diastolic flow as electromagnetic devices do (7,14); 4) the probes are suitable for long-term studies (17) since the quality of the received signal improves with reactive infiltrating tissue growth around the probe/ vessel, providing the necessary acoustic conduction (3,15), and 5) the flowmeter zero offset function permits frequent calibration in conscious freely moving rats. The perivascular transit-time probe has been successfully used for continuous assessment of flow in coronary (17), mesenteric (13,(15)(16)(17), renal (13,14,17,24), carotid (13), gastric (11,12), hindlimb (13,17,25,26) and pulmonary arteries (7) and also for measurement of cardiac output (3,8,13,15,24).…”