Intracoronary hyperosmotic mannitol during reperfusion does not affect infarct size in ischemic, reperfused porcine hearts.

We investigated the effect of reperfusion with hyperosmotic mannitol on the infarct size in porcine hearts. The distal half of the left anterior descending coronary artery was occluded in each of 21 anesthetized pigs for 75 min and was reperfused for 2 h. During reperfusion mannitol (1075 mosmol/kg) was intracoronarily infused at a dose of 0.5 ml/min in 6 pigs ("low" mannitol group), at a dose of 1.5 ml/min in another 6 pigs ("high" mannitol group), and at a dose of 5 ml/min in 3 pigs for the first 8 min of reperfusion ("very high" mannitol group). 6 pigs served as controls. Although mannitol infusion increased plasma osmolality in the ischemic, reperfused myocardium in all experiments, the infarct size expressed as the ratio of the infarcted tissue over the area at risk of necrosis was not significantly influenced. Infarct size amounted to 72 +/- 25% in the control group, to 75 +/- 14% in the "low" mannitol group, to 78 +/- 18% in the "high" mannitol group, and to 93 +/- 8% in the "very high" mannitol group. These results clearly indicate that reperfusion with hyperosmotic mannitol after 75 min of ischemia does not exert any beneficial effect on the infarct size.