Effects of diltiazem on postischaemic renal cortical microcirculation in the pig

Diltiazem - a calcium entry blocker - was tested in a porcine model under continuous chlormethiazole-pancuronium anaesthesia as protection against renal failure following 60 min of renal ischaemia. Fourteen pigs were randomly allocated to one experimental (diltiazem and ischaemia) and one control group (only ischaemia) (n = 7 in each). Diltiazem was administered as a continuous intravenous infusion started before the ischaemic insult. In two additional animals diltiazem was given but ischaemia was not induced. The postischaemic renal cortical microcirculation was simultaneously investigated in four different regions in the left kidney during the first 4 h of reperfusion. Laser Doppler flowmetry (LDF) was performed in two different regions and measurement of tissue oxygenation was done in two other regions. In the two animals treated with diltiazem without ischaemia, only minor variations in central haemodynamic and renal microcirculatory parameters were evident. In the control group (ischaemia), superficial renal cortical blood flow (Q decreased from 49 ± 11 (s.d.) arbitrary units at baseline to 24 ± 4 arb. units 4 h after start of reperfusion (P<0.05). Simultaneously, mean Pto2 decreased from 4.5 ± 1.2 kPa to 2.4 ± 1.5 kPa (P<0.05) and the percentage of the measured Pto2 values that were <0.6 kPa (Pto2) increased from 1 ± 2% to 19 ± 25% (P<0.05). In the experimental group Q decreased from 49 ± 8 arb. units at baseline to 27 ± 10 arh. units 4 h after start of reperfusion (P<0.05). Simultaneously, mean Pto2 decreased from 4.6 ± 1.3 kPa to 3.2 ± 2.0 kPa (P<0.05) and L-Pto2 increased from 0 to 18 ± 23% (P<0.05). No significant differences in the renal microcirculatory parameters were found between control and experimental groups at baseline or 4 h after start of reperfusion. The postischaemic reduction (P<0.05) in inulin clearance during the investigated period was also unaffected by diltiazem. Thus, we conclude that intravenous pretreatment with diltiazem, which was used in this experimental porcine model, has no beneficial influence on either superficial renal cortical microcirculation or on recovery of inulin clearance after ischaemia.