The effects of dexmedetomidine on human internal mammary artery and saphenous vein grafts under hypothermia and normothermia

OBJECTIVES: The purpose of this study was to determine the effects of hypothermia and normothermia on the isolated human saphenous vein (SV) and internal mammary artery (IMA) responses to dexmedetomidine. METHODS: The response of human IMA and SV strips with (E+) and without (E-) endothelium subjected to cumulative concentrations of (10(-9), 0(-6) M) dexmedetomidine were recorded at 37 degrees C and at 28 degrees C. OnE-way ANOVA was used for analysis. A p < 0.05 was considered significant. RESULTS: At 37 degrees C dexmedetomidine resulted in similar signifi cant concentration-dependent contractions in both E+ and E-SV strips (p < 0.05). At 37 degrees C dexmedetomidine resulted in signifi cant concentration-dependent contractions in E+ IMA strips, these contractions were significantly lower at all concentrations of dexmedetomidine in E-compared to E+ IMA strips (p < 0.05). When results between similar groups of SV and IMA strips were compared, the contractions were significantly higher in the IMA strips in E+ and E-at 37 degrees C and also E-28 degrees C groups compared to SV (p < 0.05). CONCLUSION: In conclusion, dexmedetomidine causes in vitro vasoconstriction in human IMA and SV grafts. These contractions are greater in IMA compared to SV grafts. Endothelium-derived pathways are possibly involved in the contractile responses of IMA. Moderate hypothermia augments vasoconstriction in SV grafts