What happened if various kinds of postconditioning working on the preconditioned ischemic skin flaps

Ischemic pre-conditioning and post-conditioning are useful manipulations to reduce the undesirable effects of ischemia-reperfusion skin flap each. But the impact of post-conditioning on the pre-conditioning skin flap is not manifested. Here we investigated the influence of ischemic post-conditioning in a preconditioned axial pattern skin flap model.

We used the skin flap in 40 rabbits and divided them into 5 groups randomly. At first we induced the ischemic pre-conditioning of the flap which was applied by 2 periods of 15 minutes of ischemia/15 minutes of reperfusion cycle. Next post-conditioning was performed by 6 cycles of 10 seconds of repeated ischemia/reperfusion periods at different times of just after the reperfusion,5 minutes after the reperfusion,10 minutes after the reperfusion. The animals were allocated into 5 groups: group 1 (Ischemia Group); group 2: (Pre-conditioning Group); group 3: (Pre-conditioning+ Post-conditioning Group); group 4 (Pre-conditioning+ Post-conditioning 5 minutes later Group); group 5 (Pre-conditioning+ Post-conditioning 10 minutes later). The neutrophil count was assessed with histologic analysis before the dissection of the skin flap. Flap viability was assessed 1 week after the operation, and surviving flap area was recorded as a percentage of the whole flap area. LSD test was used for statistical analysis among different groups to evaluate the effects of ischemic pre-conditioning against ischemia.

Among the varying groups, the neutrophil count varied: Group 1 was 50.12 ± 5.91; Group 2, 30.00 ± 2.00, and Group 3, 18.87 ± 3; Group 4, 22.50 ± 1.92; Group 5, 30.12 ± 1.88.The mean ± SD surviving areas of the flaps for groups 1, 2, 3, 4 and 5 were 31.76 ± 4.59, 51.26 ± 3.24,82.18 ± 5.28,66.85 ± 3.87 and 51.13 ± 2.90 respectively. Spearman correlation analysis shows an increase relation between neutrophil count and flap survival rate in the different groups (P <0.05).

Ischemic post-conditioning has protective effect on ischemic preconditioned skin flaps, but the post-conditioning should be performed within 5 minutes after the end of ischemia.