Analysis of the protective effect of hydrogen sulfide over time in ischemic rat skin flaps

Hydrogen sulfide (H₂S) is a widely studied gasotransmitter, and its protective effect against ischemia-reperfusion damage has been explored in several studies. Therefore, a requirement exists for a comprehensive study about H₂S effects on ischemia-reperfusion damage in flap surgery. The aim of this study is to examine the effect of hydrogen sulfide by creating ischemia-reperfusion injury in the vascular-stemmed island flap prepared from the rat groin area.

"Wistar albino" rats weighing between 250 and 300 grams were divided into 4 groups (group 1, group 2, group 3, group 4). Each group was divided into 2 subgroups: subgroup A (control) and subgroup B (H₂S). In each group, skin flaps were elevated as an island flap with a superficial epigastric artery pedicle, 6 × 4cm from the groin area. In subgroup B (H₂S), liquid hydrogen sulfide was injected through the tail vein 20minutes before ischemia at a final concentration of 10μM. Femoral artery and vein blood flows were stopped with separate microclips and left in ischemia, according to the planned ischemia hours of the flaps: group 1 as 1 hour, group 2 as 2hours, group 3 as 3hours, and group 4 as 6hours. Later, microclips were removed, and blood flow restored again. After 12hours of reperfusion, the rats were sacrificed by cervical dislocation, and tissue samples were taken. From the samples taken, neutrophil count in ischemic tissue, MDA (malondialdehyde) measurement, and damage in the tissue were evaluated by electron microscopy.

On electron microscopy inspection at all hours (1, 2, 3, and 6), hydrogen sulfide was found to provide protection against ischemia, reperfusion damage, and apoptosis at the cellular level. There was a statistically significant (P=0.035) decrease in the tissue neutrophil count at the 1st, 2nd, and 3rd hours. In the tissue MDA measurement, a statistically significant (P=0.026) decrease in hydrogen sulfide was detected at the first hour. There was no statistically significant difference in the 6th hour tissue neutrophil count and 2nd, 3rd, and 6th hour tissue MDA measurement.

Electron microscopy results in this study showed that hydrogen sulfide had antiapoptotic effects on reperfusion damage in skin flaps at all hours. However, the neutrophil counts showed it had cytoprotective and anti-inflammatory properties during the 1st, 2nd, and 3rd hours following ischemia, but not during the 6th hour. Tissue MDA levels indicate that H₂S mitigates significant I/R injury during the 1st hour but not in the subsequent 2nd, 3rd, and 6th hours. These results led to the hypothesis that, in order to offer a strong enough protective effect against I/R damage, H₂S should be administered repeatedly or at varying concentrations. After more research on how H₂S affects skin flaps, we believe that it can be used in plastic surgery practices.