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NEUROSURGICAL ANESTHESIA

The Effect of Calcium Channel Blockers on Cerebral Oxygenation During Tracheal Extubation

Department of Anesthesiology and Critical Care Medicine, Hokkaido University School of Medicine, Sapporo, Japan

Address correspondence and reprint requests to Yuji Morimoto, MD, PhD, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduated School of Medicine, Sapporo, 060-8638, Japan. Address e-mail to morim2{at}med.hokudai.ac.jp

Calcium channel blockers are effective in stabilizing systemic hemodynamics during tracheal extubation. However, they may increase cerebral blood flow (CBF) during tracheal extubation because of cerebral vasodilation, even if systemic arterial blood pressure decreases. In this study, we observed changes in cerebral oxygenation during tracheal extubation by using near-infrared spectroscopy and evaluated the effect of nicardipine and diltiazem on the resultant changes. We studied 45 women undergoing elective gynecologic surgery. After surgery, the patients were randomly allocated to three groups (n = 15 each): saline (control) , 0.02 mg/kg nicardipine, and 0.2 mg/kg diltiazem. After 2 min, we started to aspirate secretions for 2 min and then, extubated the trachea. Changes in cerebral oxygenated hemoglobin (HbO₂) and deoxygenated hemoglobin were measured during the extubation procedure for 9 min after drug treatment. Systemic hemodynamics, including mean arterial blood pressure, heart rate, end-tidal CO₂, end-tidal sevoflurane concentration, and peripheral arterial oxygen saturation were also monitored. During extubation, HbO₂ increased significantly, presumably caused by the increase in CBF. Changes in deoxygenated hemoglobin were minimal. Compared with the control, nicardipine and diltiazem significantly inhibited the increase in mean arterial blood pressure. On the contrary, they significantly enhanced the increase in HbO₂. In conclusion, calcium channel blockers may increase CBF during extubation, even if these drugs stabilize systemic hemodynamics.

Implications: This study is a preliminary report evaluating the changes in cerebral oxygenation during the tracheal extubation. Cerebral oxygenated hemoglobin increased significantly, presumably caused by the increase in cerebral blood flow during extubation. In addition, these changes were enhanced by calcium channel blockers.

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