Continuous measurements of renal perfusion in pigs by means of intravascular Doppler

renal perfusion may result from a reduction of mean Background. Changes in renal blood flow are considered to arterial blood pressure (MABP) or decreased cardiac outplay a significant role in the induction and maintenance of put or may be due to renal vasoconstriction. The combinakidney failure, but are difficult to monitor with currently availtion of moderately reduced perfusion pressure and inable techniques. The objective was to validate renal flow measurements with Doppler guidewires and to apply this technique creased renal vascular resistance (RVR) is believed to to assess dose and time dependency of the renal vascular effects promote renal failure in patients with sepsis [2] or hepatoof norepinephrine (NE). renal syndrome [3]. The adverse effects of several “nephMethods. In 10 anesthetized pigs, flow velocity in renal arter- rotoxic” agents, including contrast media, on kidney ies (FVart) and veins (FVvein) and volumetric renal blood function are also considered to be partially due to a flow (VBF) were measured before and after intravenous bolus application of incremental doses of NE (2 to 200 mg). temporary reduction in RBF [1]. Some studies have indiResults. FVart curves exactly reflected the changes in VBF. cated that a reduction in RBF persists during the course Beat-to-beat analysis revealed a strong linear correlation over of ARF [4, 5], while others have reported that RBF is a mean VBF range of less than 0.05 to 0.35 L/min (median not an important determinant of the glomerular filtration correlation coefficient with FVart, r 5 0.998), and significant rate (GFR) depression during the maintenance phase of but less close relationships were also found between VBF and FVvein. Ten seconds after the administration of 200 mg NE, postischemic ARF [6, 7]. Therefore, in different clinical FVart dropped from 71 to 6 cm/sec and was 90% reversible situations, monitoring of renal perfusion may be releafter 48 seconds. Similarly, the renal vascular resistance tempo- vant, not only to characterize further the association rarily rose from 988 to 13711 mm Hg · min/L. In contrast, between changes in renal hemodynamics and GFR, but NE-induced increases in systemic vascular resistance were on average a maximum of 1.5-fold but persisted for more than 60 also to identify and prevent ischemic insults to the seconds. kidney. Conclusions. Doppler flow measurements in the renal artery Currently available methods for the measurement of provide an excellent surrogate of volumetric blood flow, which RBF in humans have been useful to detect RBF abnormay be useful for continuous monitoring of renal hemodynammalities in various settings, but are characterized by sevics. The renal vasculature is more sensitive when compared with the systemic vasculature, but also appears to evoke more eral methodological problems that limit their accuracy efficient counter-regulatory mechanisms in response to NE. and applicability. The urinary clearance of p-aminohippurate (PAH) [8] cannot be applied to oligo-anuric subjects, and in postischemic renal failure, PAH extraction A reduction in renal blood flow (RBF) commonly is severely impaired so that the PAH clearance markedly occurs in association with renal dysfunction and can cause underestimates renal plasma flow [6]. Dye dilution techkidney failure. In acute renal failure (ARF), renal hypo- niques require the simultaneous catheterization of the renal artery and vein and allow only bolus measurements [9]. For isotope techniques, the need for external count