Biomedical subjects

L O Lerman

Publications and source records attributed to L O Lerman.

42 records · Page 3Linked to original sources

PubMed1995

Pressure dependency of canine intrarenal blood flow within the range of autoregulation.

The mechanism of pressure-induced natriuresis remains controversial. To assess whether intracortical or medullary renal blood flows (RBF) change with changes in renal perfusion pressure (RPP), global and regional RBFs were measured using the dynamic spatial reconstructor, a fast computed tomography scanner, in eight anesthetized dogs (group B) within the range of RBF autoregulation (RPP of 153.5 and 114.4 mmHg). Similar measurements were obtained in seven control dogs (group A) in which RPP was not manipulated. In group B, only inner medullary perfusion decreased (from 0.84 to 0.51 ml/min per cm3 of tissue, P = 0.03) with reduction of RPP, whereas global renal, intracortical, and outer medullary perfusions remained unaltered. In group A there was no change in global or regional renal perfusion. The change in inner medullary perfusion in group B (-34.7%) was significantly different (P = 0.021) from that in group A (+27.4%). Global, cortical, and total medullary RBFs (ml/min) and volumes did not change in either group. These results suggest that with changes in RPP, the only detectable change in intrarenal perfusion occurs in the inner medulla.

Animals↗

PubMed1994

Quantification of global and regional renal blood flow with electron beam computed tomography.

Alterations in renal blood flow distribution may occur in a variety of pathophysiologic situations; however, quantification of global and regional renal blood flows has been limited because of the lack of reliable, noninvasive techniques. To determine the feasibility of flow measurements with electron-beam computed tomography (EBCT), six anesthetized dogs were scanned by EBCT during basal conditions, after renal vasodilation, and at recovery. Flow (mL/min/cm3 tissue) was calculated from EBCT-derived time-density curves using three different algorithms and compared with simultaneously obtained electromagnetic flow (EMF) probe measurements after indexing to EBCT-derived renal volume. EBCT-determined flow correlated well with EMF measurements regardless of the algorithm used. An algorithm using the area under the time-density curve was concluded to be the most suitable for calculation of renal blood flow; it correlated with EMF as EBCT flow = 44.5 + 1.05 EMF (r = 0.885, SEE = 31.2 mL/min, P < .0001). Consistent overestimation of flow by EBCT resulted probably from retention of contrast media in the renal parenchyma. EMF showed an increase of 20 +/- 10% in renal blood flow after vasodilation. EBCT-derived global, cortical, and medullary flows increased by 33.8 +/- 10.3%, 24.8 +/- 17.8%, and 99.0 +/- 73.8%, respectively. In conclusion, EBCT was found feasible for credible quantitation of renal blood flow in the physiologic range studied.

Algorithms↗

PubMed1994

Measurement of renal perfusion and blood flow with fast computed tomography.

Fast computed tomography (CT) is one of the few methods available to measure cortical and medullary renal blood flow (RBF) directly. Because these measurements are complicated by passage of the contrast medium into extravascular compartments, we used the residual opacity following the vascular blush as an index to account for extravascular iohexol. Kidneys of anesthetized dogs were examined in situ by fast CT following intra-aortic injections of iohexol. Perfusion was analyzed during a control period and three subsequent periods in which RBF was reduced by 10%, 30%, and 50%. Cortical microvascular distribution volume changed from 19.7 +/- 2.8% to 19.8 +/- 1.7%, 15.3 +/- 1.2%, and 9.9 +/- 1.7%, respectively, without significant alterations in cortical mean transit time. Microvascular distribution volume was divided by mean transit time to determine tissue perfusion. Cortical perfusion changed from 3.8 +/- 0.7 to 3.9 +/- 0.6, 3.1 +/- 0.5, and 2.2 +/- 0.5 mL.min-1.mL tissue-1. Total cortical blood flow (cortical perfusion multiplied by cortical volume) decreased from 164 +/- 32 to 159 +/- 31, 117 +/- 20, and 86 +/- 22 mL/min, respectively. Medullary microvascular distribution volume, mean transit time, perfusion, and total blood flow remained unchanged. Fast CT-determined total RBFs (cortex plus medulla) were similar to simultaneous electromagnetic flow measurements. These results indicate that renal regional perfusion is more dependent on the microvascular distribution volume than mean transit time and that variations in renal tissue perfusion with reduction of RBF are more apparent in the cortex than in the medulla.

Analysis of Variance↗

PubMed1991

The effect of a low-osmolar radiographic contrast medium on in vivo and postmortem renal size.

High osmolar radiographic contrast media (CM) are known to cause an increase in renal size. To examine the effect of low-osmolar CM on renal size, 14 anesthetized dogs received 12 intravenous bolus injections of 0.5 mL/kg iohexol (541 mOsm/L). The postmortem renal, cortical, and medullary volumes were determined by fluid displacement. Renal volumes of 18 control dogs were determined similarly. The mean (+/- SEM) postmortem renal volumes were 66.1 +/- 2.2 mL for the CM group and 52.3 +/- 3.3 mL for the control group (P = 0.003), whereas the cortical and medullary volumes were similar. Six dogs were also scanned by fast computerized tomography before and after iohexol administration. The in vivo whole renal and medullary volumes enlarged from 67.4 +/- 3.0 to 77.1 +/- 2.8 mL (P = 0.006), and from 28.5 +/- 2.0 to 35.1 +/- 1.1 mL (P = 0.026), respectively, while the cortical volume remained unaltered. These results suggest that even low osmolar CM may significantly increase renal volume, probably by causing tubular expansion.

Animals↗

PubMed1990

Quantitation of the in vivo kidney volume with cine computed tomography.

The authors examined the utility of cine computerized tomography (CT) for noninvasive determination of whole kidney, cortical, and medullary volumes. The right kidneys of 14 anesthetized dogs were scanned after an intravenous bolus injection of iohexol, and their volumes determined after boundary identification. After the scans, the kidneys were excised at postmortem examination and their volumes determined by fluid displacement. The mean (+/- standard error of the mean [SEM]) postmortem and in vivo renal volumes were 66.1 +/- 2.2 cc and 78.2 +/- 2.4 cc, respectively (r = 0.86; P less than 0.001). The difference was consistent with the blood, filtrate, and urine contents of the in vivo kidney. The in vivo cortical and medullary volumes correlated poorly with their postmortem volumes because of difficulties in boundary definition. These results demonstrate the feasibility for fast and reliable in vivo whole kidney volume quantitation by cine CT.

Animals↗

PubMedDate not supplied

Measurement of in vivo myocardial microcirculatory function with electron beam CT.

PURPOSE: The purpose of this work was to examine the capability of electron beam CT (EBCT) to characterize responses of recruitable (capillaries and small arterioles) compared with nonrecruitable (small to large arterioles) myocardial microvessels to vasoactive substances. METHOD: Myocardial perfusion (F) and total intramyocardial blood volume (BV) of the anterior cardiac wall were quantitated in 36 pigs, using EBCT and intravenous contrast agent injections, before and after intracoronary administration of either NG-monomethyl-L-arginine (L-NMMA), nitroglycerin, adenosine, or saline. Plotting the relationship of BV and F provided values for the recruitable and nonrecruitable microvascular transit times and BV allotment. RESULTS: Nitroglycerin increased nonrecruitable BV by 84.5+/-7.4%, whereas adenosine increased both recruitable and nonrecruitable microvascular BV (47.1+/-18.9 and 66.0+/-10.9%, respectively). L-NMMA led to a 25.1% decrease only in the recruitable BV. In the control group, no changes were observed. CONCLUSION: Characteristic responses of different-size myocardial microvessels may be inferred with EBCT, which provides a unique opportunity to portray intramyocardial microcirculatory function noninvasively.

Animals↗