Background:
Enteric tissue, commonly used in free tissue transfer (FTT) reconstruction of the hypopharynx and esophagus, is exquisitely sensitive to the oxidative stress and inflammatory response that occur during periods of even brief ischemia and subsequent reperfusion. The resultant ischemia-reperfusion injury (IRI) is a major contributor to post-operative morbidity and potentially catastrophic flap loss. In this study, we evaluated whether treatment with hydrogen sulfide (H₂S), a gasotransmitter now recognized to be a mediator of cellular metabolism, could prevent intestinal IRI in vivo.
Methods:
Thirty-six male Sprague-Dawley rats received intravenous aqueous NaHS sufficient to raise blood H₂S concentrations to 0, 1μM, 10μM, or 100μM. Twenty minutes later, a segment of jejunum was isolated and the mesenteric artery was temporarily occluded with a microsurgical clip for 1, 2, or 3 hours, at which time the clip was removed and the segment was reperfused for 3 hours. The ischemic-reperfused segment and a non-ischemic control segment were harvested, photographed, processed, and stained with hematoxylin and eosin (Figure 1). Villous height was measured to quantify architectural integrity (Figure 2). The data were analyzed using a two-way ANOVA and Tukey-Kramer post hoc tests (family error rate of α=0.05), and the results were expressed as mean percentage of control ± SE. The level for statistical significance was set at p<0.05. Cohen’s d was reported to show the size of the treatment effect. By convention, d > 0.8 corresponds to a large effect size.
Results:
All tested H₂S concentrations conferred statistically significant protection against IRI induced villous breakdown; the 10μM H₂S treatment conferred the greatest protection at all time points (62.94%±29.79%), p<0.001. Furthermore, the villous heights (expressed as a percentage of non-ischemic control height) for the 10μM H₂S at 1 hour (84.31%±12.63%) and 2 hours (80.16%±13.20%) of ischemia showed no statistically significant difference from those of the non-ischemic control. The 10μM H₂S treated group showed a statistically significantly greater villous height than did the 0 H₂S group after 1 and 2 hours of ischemia (d=3.60 and d=6.33, respectively). There was no evidence of either cellular injury or villous breakdown in the non-ischemic controls treated with H₂S.
Conclusion:
These data indicate that H₂S confers significant protection against IRI in enteric tissue. Our results demonstrate that when delivered prior to an anticipated ischemic insult (e.g. FTT) a dose of NaHS sufficient to raise blood H₂S concentration to 10μM provides optimal protection against IRI for up to 2 hours of ischemia, without evidence of toxicity. Thus, H₂S may hold tremendous potential as a simple and powerful treatment for the prevention of IRI in the setting of reconstructive surgery.