Lipid-emulsion propofol (LP) has cardioprotective effects against ischemia-reperfusion injury, but it has lipid-related side effects. Microemulsion propofol (MP) is a lipid-free propofol emulsified with 10% purified poloxamer 188 (PP188). PP188 is a nonionic surfactant and has cardioprotective effects. However, some reports have suggested that reduced cardioprotective effects were observed when the cardioprotective agents were used in combination even though each cardioprotective agent has cardioprotective effects. The aims of this study were to examine and compare the cardioprotective effects of MP and LP.

50 isolated rat hearts were perfused with modified Kreb's solution. They were divided into 4 groups and underwent 30 minutes of ischemia and 60 minutes of reperfusion. Control group: ischemia-reperfusion was performed without treatment. LP, MP and PP groups: LP, MP and PP188 were infused during the pre-ischemic and reperfusion period, respectively. Hemodynamic parameters and coronary effluent flow rate (CEFR) were measured. Infarct size was determined using triphenyl-tetrazolium staining.

In the MP group, systolic pressure was maintained near baseline, the systolic pressure was higher than that in the other groups and HR was lower than that in the other groups during reperfusion. Diastolic pressure was transiently increased in the PP group after treatment and at 5 minutes after reperfusion compared with that in the control group and in the the LP group. There were no differences in dP/dt_max and CEFR between groups. Infarct size in the LP, MP and PP groups was smaller than that in the control group, but there were no significant differences between these three groups.

MP has cardioprotective effects similar to those of LP. MP can be used for cardiac anesthesia in cases with ischemia-reperfusion injury to avoid the lipid-related side effects of LP.