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

Abstract

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. 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 °C and at 28 °C. OnE-way ANOVA was used for analysis. A p < 0.05 was considered significant. At 37˚C dexmedetomidine resulted in similar significant concentration-dependent contractions in both E+ and E- SV strips (p < 0.05). At 37 °C dexmedetomidine resulted in significant 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 °C and also E- 28 °C groups compared to SV (p < 0.05). 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 (Fig. 3, Ref. 27).