Postischaemic renal cortical microcirculation and tissue oxygenation in the pig

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Abstract
Porcine and human renal physiology are similar in important aspects. Renal cortical microcirculation and its relation to inulin clearance (CIn) was therefore studied before and after renal ischaemia in 28 pigs under continuous intravenous chlormethiazole-pancuronium anaesthesia. The anaesthesia used provided essential stability in central haemodynamics. The animals were studied for 90 min of reperfusion following 0, 30 or 60 min of renal ischaemia. Twelve of the animals (four were subjected to each duration of ischemia) were also studied 18 h after start of reperfusion. Regional blood flow in the superficial renal cortex was measured by laser Doppler flowmetry (LDF), and tissue oxygenation (PtO2) by surface microelectrode technique. These techniques allow continuous or repeated measurements. During the first 90 min of reperfusion, superficial renal cortical blood flow measured by LDF (Qsrc) underwent considerable temporal variation which followed a certain pattern. Thus, when the renal arterial blood flow was restored after ischaemia, we observed an instant peak in Qsrc followed by a decreasing flow until a minimum value (Qmin) was reached between 3 and 9 min after start of reperfusion (tQmin). Thereafter, Qsrc increased until a maximal value (Qmax) was reached between 11 and 64 min after start of reperfusion (tQmax). The parameters tQmin and tQmax were related to inulin clearance 18 h after start of reperfusion (P less than 0.05 and P less than 0.01, respectively). Thus, it might be possible soon after start of reperfusion--to evaluate the severity of ischaemic damage. This could be useful in the evaluation of different prophylactic strategies, since the full extent of the ischaemic damage, as assessed by clearance determinations, cannot be established until hours later.(ABSTRACT TRUNCATED AT 250 WORDS)