Research Trends

This study assessed the mechanisms of respiratory centre excitation after administration of acetazolamide (AZ) as a carbonic anhydrase inhibitor (CAI) to rabbits. Male Japanese white rabbits were divided into group AZ5 (n=14, AZ 5 mg/kg) and group AZ20 (n=10, AZ 20 mg/kg). Each rabbit was anesthetized using ketamine and urethane under spontaneous respiration. Followed by inserting central venous and arterial catheters, a small catheter was inserted through an endotracheal tube for measuring end-tidal PCO₂ (PetCO₂), and a sigmoid tonometry catheter was inserted into the stomach through the oesophagus for measuring PCO₂ in tissue. A percutaneous tissue CO₂ sensor was embedded under the abdominal skin. Systolic arterial pressure (SAP), heart rate (HR), respiratory rate (RR), rectal temperature (RT), PetCO₂, tissue CO₂ pressure by gastric tonometry (PgtCO₂), and CO₂ pressure through percutaneous tissue (PptCO₂), in arterial blood (PaCO₂), and in mixed venous blood (P

CO₂) were measured for 180 min after AZ administration. In both groups, PetCO₂ decreased significantly and RR, PgtCO₂ and PptCO₂ increased significantly in a dose-dependent manner after AZ administration. No other values showed significant changes. These results suggest that the respiratory centre might be stimulated by retained CO₂ following CAI administration, with subsequent reduction of PetCO₂ and significantly decreases in PaCO₂ and P

CO₂. Therefore, attention should be paid to both increasing RR and retained CO₂. PCO₂ (PetCO₂, PaCO₂, P

CO₂, PgtCO₂ and PptCO₂) might thus warrant observation in severely ill patients while CAI is administered.