Variations in superficial renal cortical blood flow and tissue oxygenation: an experimental porcine model

Abstract

Renal cortical microcirculation and its relation to inulin clearance, central haemodynamics and pulmonary gas exchange were studied in eight pigs under continuous intravenous chlormethiazole-pancuronium anaesthesia. The animals were studied during six consecutive 30-min periods. Four of the animals were also studied 19 h after the first period. In the superficial renal cortex, regional blood flow (Qsrc) was measured by laser Doppler flowmetry (LDF) and tissue oxygenation (PtO2) by surface microelectrode technique. Central haemodynamics and pulmonary gas exchange values were distributed within normal ranges. The importance of stable central haemodynamics in order to perform accurate microcirculatory measurements in the renal cortex was documented. A significant relation between Qsrc and pulmonary capillary wedge pressure (PCWP) was found (P less than 0.0001) despite the fact that PCWP was distributed within a range of only 0.7 kPa (all values were well within the normal range for pigs). No other relationships were found between central haemodynamics or pulmonary gas exchange variables and renal microcirculatory parameters. Concerning renal microcirculation and inulin clearance, at least 2-3 h may be required for stabilization after surgery. The average temporal variability between measurements performed every 30 min in each animal was 6 +/- 7% (s.d.) in the LDF values and 21 +/- 21% in the PtO2 values (mean PtO2). No correlations were found between Qsrc or PtO2 and inulin clearance. Since the haemodynamic parameters, pulmonary gas exchange variables and haematocrit were distributed within narrow ranges, we regard the temporal microcirculatory variability obtained here as normal in this experimental situation, and consider the porcine model well suited for further studies concerning renal microcirculation.

Tissue oxygen and hemodynamics in renal medulla, cortex, and corticomedullary junction during hemorrhage-reperfusion

“…Paired intrarenal flow and tPO 2 measurements have been previously reported, but only in the rat renal medulla (18) and from the kidney surface in the pig (25). However, these were not used to extrapolate changes in regional oxygen consumption and have never been performed from within all three anatomic regions of the kidney simultaneously.…”

Renal vascular response to left atrial injection. An experimental study in the pig

“…Despite the fact that the first injection of microspheres (label A) was very slow, in an attempt to avoid eliciting any response a reduction in RBF was recorded in five of the seven animals. No reaction was identified by LDF in any of the animals, but it should be emphasized that the LDF measurements were performed in two small tissue volumes and that other parts of the superficial cortex might very well have been involved (10). The following injections (5 ml of saline, 1 ml of plasma containing microspheres label B and 5 ml of saline) were given at a "normal" rate of injection when using the microsphere technique (5,6) and at least one of the recordings (Qsrc or RBF) indicated a response in all animals.…”

Appraisal of the porcine kidney autotransplantation model

“…Where human kidneys are anatomically and functionally mature at gestational age, porcine kidneys are mature at 2 to 3 months (20-30 kg) of age. 11,12 Thus, to translate porcine organ function to the human, adult setting, the age of the pig should at least be above 3 months. Furthermore, at 7 to 8 months of age (100-120 kg), pigs reach puberty during which androgens can infl uence IR injury by inhibiting non-androgen receptor-mediated processes.…”

“…Age and sex related endocrine factors should be considered in experimental designs while young piglets (20-30 kg) are developmentally equal to human infants regarding functional characteristics and anatomy of the kidney. 12 Therefore, we pose an optimal age with female pigs for the autotransplantation model of 5 months (50 kg), representing comparable kidney function to adult humans.…”