Preservation of myocardial function with mannitol reperfusate.

Area of Science:

• Cardiology
• Biochemistry
• Pharmacology

Background:

• Myocardial preservation during ischemia-reperfusion is critical.
• Mannitol is known to protect the myocardium, but its mechanism is debated.
• Potential mechanisms include hyperosmolarity and free radical scavenging.

Purpose of the Study:

• To investigate the protective mechanism of mannitol during myocardial reperfusion.
• To differentiate between hyperosmolar and free radical scavenging effects of mannitol.

Main Methods:

• Isolated, perfused rabbit hearts subjected to 45 minutes of global normothermic ischemia.
• Three reperfusion groups: isosmolar solution, mannitol solution (20 mOsm/L), and hypertonic saline solution (20 mOsm/L).
• Assessment of left ventricular developed pressure, dP/dt, diastolic compliance, myocardial edema, oxygen consumption, and lactate production.

Main Results:

• Mannitol reperfusion significantly improved left ventricular developed pressure, dP/dt, and diastolic compliance compared to control and hypertonic saline groups (p < .05).
• No significant differences were observed in myocardial edema, oxygen consumption, or lactate production among the groups.
• These findings suggest mannitol's protective effect is not due to hyperosmolarity.

Conclusions:

• Mannitol provides significant myocardial protection during reperfusion, independent of its hyperosmolar properties.
• Free radical scavenging is the most plausible mechanism for mannitol's cardioprotective effects.
• Further biochemical and cellular studies are needed to confirm the free radical scavenging mechanism.