Cerebral blood flow determinations by radioactive microspheres in the subhuman primate: influence of unilateral internal carotid ligation, hypercapnic acidosis, and hypocapnic alkalosis

Cerebral blood flow (CBF) was measured by electromagnetic and radioactive microsphere (RMS) techniques in the anubis baboon. Regional cerebral blood flows were calculated by distribution of intracardiac injections of RMS, labeled with one of three radionuclides: ⁵¹Cr, ⁸⁵Sr, or ¹⁴¹Ce. In group I (six animals normocapnia), CBF's as estimated by electromagnetic measurement of internal carotid blood flow, were 65 ± 10 and 74 ± 4 (S.E.M.) ml, per minute per 100 Gm, for the right (RH) and left (LH) cerebral hemispheres, respectively; whereas CBF's as estimated by the RMS technique were 65 ± 5 and 70 ± 4 ml per minute per 100 Gm., respectively, and these values were not significantly (p>0.05) different. CBF, as determined by RMS techniques in Group 1, was not altered by unilateral internal carotid arterial ligation. In Group 2 (seven animals), atrial PCO₂ was varied randomly from a low range ( 18 ± 2 mm. Hg, L), to a middle range (PCO₂, 36 ± 2, M), and to a high range (PCO₂ 64 ± 2,H), and CBF was measured by the RMS technique. During L, M, and H, CBF's were 44 ± 10, 75 ± 15, and 159 ± 27 ml, per minute per 100 Gm, respectively, for RH, whereas CBF's were 44 ± 10.75 ± 15, and 160 ± 26 ml. per minute per 100 Gm., respectively for LH. During H, RH and LH were significantly (p<0.05) greater than during L and M. Changes in regional CBF were uniform throughout the brain. These data demonstrate the correlation between CBF, as estimated by electromagnetic and RMS techniques, as well as confirm the adequacy of collateral cerebral circulation during unilateral carotid arterial ligation in the baboon. The usefulness of the RMS technique for hemispheric and regional CBF measurements is presented also.