Coronary Sinus Isoflurane Concentration in Cardiac Surgery

Area of Science:

• Anesthesiology
• Cardiovascular Surgery
• Pharmacokinetics

Background:

• Volatile anesthetics like isoflurane may reduce myocardial events in cardiac surgery.
• Achieving adequate myocardial tissue concentrations of isoflurane is crucial for myocardial protection.
• Direct measurement of myocardial isoflurane concentration is challenging.

Purpose of the Study:

• To measure isoflurane concentration in coronary sinus (CS) blood during cardiopulmonary bypass (CPB).
• To assess if CS blood isoflurane concentrations equilibrate with arterial blood.
• To determine the relationship between CS blood isoflurane and oxygenator exhaust levels.

Main Methods:

• Prospective, observational study at a single university hospital.
• 23 patients undergoing cardiac surgery with CPB and isoflurane anesthesia.
• Analysis of isoflurane in CS and radial artery blood via gas chromatography and mass spectrometry.

Main Results:

• Mean arterial isoflurane: 87.7 ± 50.1 μg/mL; Mean CS isoflurane: 73.0 ± 42.9 μg/mL.
• Significant difference (14.7 μg/mL) between arterial and CS isoflurane concentrations.
• Positive correlation between oxygenator exhaust and both CS (r=0.68) and arterial (r=0.72) isoflurane levels.

Conclusions:

• First study to measure isoflurane concentration in CS blood.
• CS isoflurane can be estimated from oxygenator exhaust, but with limitations.
• CS isoflurane concentration may not accurately represent myocardial levels during CPB.