Levosimendan Administration in Limb Ischemia: Multicomponent Signaling Serving Kidney Protection

AIMS AND OBJECTIVES: Acute renal failure is a severe complication of lower extremity major arterial reconstructions, which could even be fatal. Levosimendan is a dual-acting positive inotropic and vasodilatory agent, which is suspected to have protective effects against cardiac ischemia. However, there is no data available on lower limb or remote organ ischemic injuries therefore the aim of the study was to investigate the effect of levosimendan on lower limb ischemia-reperfusion injury and the corollary renal dysfunction. METHODS: Male Wistar rats underwent 180 min bilateral lower limb ischemia followed by 4 or 24 hours of reperfusion. Intravenous Levosimendan was administered continuously (0.2mug/bwkg/min) throughout the whole course of ischemia and the first 3h of reperfusion. Results were compared with sham-operated and ischemia-reperfusion groups. Hemodynamic monitoring was performed by invasive arterial blood pressure measurement. Kidney and lower limb muscle microcirculation was registered by a laser Doppler flowmeter. After 4h and 24h of reperfusion, serum, urine and histological samples were collected. RESULTS: Systemic hemodynamic parameters and microcirculation of kidney and the lower limb significantly improved in the Levosimendan treated group. Muscle viability was significantly preserved 4 and 24 hours after reperfusion. At the same time, renal functional laboratory tests and kidney histology demonstrated significantly less expressive kidney injury in Levosimendan groups. TNF-alpha levels were significantly less elevated in the Levosimendan group 4 hours after reperfusion. CONCLUSION: The results claim a protective role for Levosimendan administration during major vascular surgeries to prevent renal complications

Kidney cortex microcirculation measured with laser Doppler flowmeter.

<p>Measured flux is expressed as a percentage of the baseline flux before the aortic clamping. Flux remained at the baseline level after clamping of the infrarenal aorta in all three animal groups. After revascularization of the limbs, a constant impairment of the kidney cortex microcirculatory flux was observed in the ischemia-reperfusion (IR) group (marked with a broken line), while flux was preserved in the Levosimendan (unbroken line) and the Sham (dotted line) groups. Values are expressed as means ± SD, ‡: p<0.001 vs. Sham, §: p<0.001 vs. IR.</p

Laboratory measurements and calculated parameters for kidney function.

<p>Laboratory measurements and calculated parameters for kidney function.</p

TNF-α concentration.

<p>TNF-α concentrations were significantly higher in the IR (ischemia-reperfusion) group compared to the Sham-operated group after 4 hours of reperfusion. TNF-α levels were significantly less elevated by Levosimendan treatment after 4 hours of reperfusion. 24 hours after reperfusion there were no significant differences among the three experimental groups. Values are expressed as means ± SD, ‡: p<0.001 vs. Sham, §: p<0.001 vs. IR.</p

Heart rate.

<p>Heart rate increased significantly from the baseline during ischemia remained elevated during reperfusion in the IR (ischemia-reperfusion) group (broken line). Levosimendan administration resulted in significantly less elevated HR compared to the IR group during both ischemia and reperfusion (unbroken line). Sham operated group is marked with a dotted line. Values are expressed as means ± SD, †: p<0.01 vs. Sham, ‡: p<0.001 vs. Sham, $: p<0.05 vs. IR, §: p<0.01 vs. IR.</p

Muscle viability.

<p>4 hours after revascularization a marked decrease in viability was detected in the IR (ischemia-reperfusion) group, without any sign of regeneration process 24 hours after reperfusion. Levosimendan administration resulted in significantly preserved viability compared to the IR group at both measured time points (4 and 24 hours). Values are expressed as means ± SD, ‡: p<0.001 vs. Sham, §: p<0.001 vs. IR.</p

Mean arterial pressure.

<p>Blood pressure elevated significantly after aortic clamping and remained elevated throughout the ischemic period in the IR (ischemia-reperfusion) group (broken line). Levosimendan treatment withheld this elevation during ischemia (unbroken line). At the onset of reperfusion a significant drop occurred, but after that, mean arterial pressure increased and then remained elevated in both IR and Levosimendan groups without significant difference between the groups. Sham operated group is marked with a dotted line. Values are expressed as means ± SD, †: p<0.01 vs. Sham, ‡: p<0.001 vs. Sham, §: p<0.001 vs. IR.</p

Muscle microcirculation measured with laser Doppler flowmeter.

<p>Measured flux is expressed as a percentage of the baseline flux before the aortic clamping. Flux dropped at the onset of aortic occlusion in both the ischemia-reperfusion (IR, marked with a broken line) and Levosimendan (unbroken line) groups. After release of the aortic occlusion, microcirculation increased to about 100% of baseline flux in the Levoismendan group, while in IR group flux reached only 80% of the baseline measurements. Sham operated group is marked with a dotted line. Values are expressed as means ± SD, ‡: p<0.001 vs. Sham, $: p<0.01 vs. IR, §: p<0.001 vs. IR.</p

Study design and groups.

<p>Male Wistar rats underwent 180 min bilateral lower limb ischemia followed by 4 or 24 hours of reperfusion. Intravenous Levosimendan was administered continuously (0.2μg/bwkg/min) throughout the whole course of ischemia and the first 3h of reperfusion, while IR and Sham groups received only vehicle (Saline infusion).</p