The Effect of Xenon on Isoflurane Protection Against Experimental Myocardial Infarction

Objectives

To investigate if the protective effects of xenon and isoflurane against myocardial ischemia-reperfusion damage would be additive.

Design

A prospective, randomized laboratory investigation.

Setting

An animal laboratory of a university hospital.

Participants

Thirty-six pigs (female German landrace).

Interventions

In an open-chest preparation with thiopental anesthesia, the left anterior descending artery was occluded to produce ischemia for 60 minutes. One hour previously, ischemic preconditioning, isoflurane (0.55 minimum alveolar concentration [MAC]) alone, or isoflurane together with xenon (0.55 MAC each) were started in the respective groups. A fourth (control) group received no protective intervention. Myocardial ischemia was followed by 2 hours of reperfusion.

Measurements and Main Results

Hearts were excised and stained (Evans Blue/TTC) to measure infarct size as related to the area at risk. Myocardial infarct size was reduced (means ± standard deviation) from 64% ± 9% of the area at risk in the control group to 19% ± 12% with ischemic preconditioning to 46% ± 12% with isoflurane and to 39% ± 13% with isoflurane and xenon. All intervention groups were significantly different from the control (p < 0.05), and both anesthetic groups were significantly different from ischemic preconditioning (p < 0.05).

Conclusion

Combined isoflurane/xenon anesthesia reduced infarct size but not more than isoflurane alone. Ischemic preconditioning was more effective than the anesthetics.

Key Words: myocardial preconditioning, inhalation anesthesia, xenon, isoflurane