Ischemia with intermittent reperfusion reduces functional and morphologic damage following renal ischemia in the rat

Attempts to minimize ischemic injury by interrupting a given ischemic period might be compromised if repeated bouts of reperfusion injury occurred. To determine whether intermittent ischemia improved or worsened functional and morphologic outcome of renal ischemia, halothane-anesthetized rats underwent a right nephrectomy and placement of a snare about the left renal vascular pedicle at 37 degrees C. Eleven animals underwent 45 minutes of continuous renal ischemia (C-ISC), whereas 10 animals received 45 minutes of vessel occlusion interrupted (I-ISC) at 15 and 30 minutes by snare release and 5 minutes of reperfusion. A group of three sham rats underwent the above procedure but did not have the snare tightened. Blood samples were drawn preoperatively and 24, 48, and 72 hours postoperatively for creatinine analysis. At 72 hours the animals were sacrificed and their kidneys morphologically evaluated. The C-ISC group had a significantly higher mean postoperative plasma creatinine (p < 0.01) as well as significantly higher plasma creatinine levels at 24 (p < 0.005) and 48 hours (p < 0.05) than did the I-ISC group. The C-ISC group also demonstrated significantly greater histologic damage than the I-ISC group (p < 0.002) when assessed by a pathologist blinded to the intervention. Sham rats did not demonstrate functional or morphologic damage. These data demonstrate a significantly improved outcome when 45 minutes of renal ischemia is interrupted by periods of reperfusion. We are led to conclude that in this setting reperfusion injury did not overwhelm the salutary effects of interrupting the 45-minute ischemic event.