Dobutamine, a β1 Adrenoceptor Agonist, Increases Cerebral Oxygenation During Acute Anemia and Apneic Hypoxia.
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BACKGROUND
β1 blockers increase the risk of cerebral hypoxia during acute anemia and apneic hypoxia. We hypothesized that β1 stimulants conversely increase cerebral tolerance to anemia and hypoxia.
METHODS
After induction with isoflurane, twelve swine (mean ± SD: 25.2 ± 0.6 kg) received 200 µg kg-1 min-1 landiolol and 20 µg kg-1 min-1 dobutamine. Reversal of the order of drug administration was performed in six animals each. Before and during each drug infusion, apnea was induced until reaching <70% oxygen saturation (SpO2) after 5 min of 100% oxygen ventilation. Hemodynamic and blood gas variables were measured, and the cerebral and peripheral tissue oxygenation index (TOI) was recorded by near-infrared spectroscopy (apnea experiment). Following this, anemia (isovolemic hemodilution) was induced and apnea experiments were conducted in three stages, similarly to those before anemia.
RESULTS
Dobutamine increased cerebral TOI before apnea (fraction of inspired oxygen [FiO2]: 1.0), at 1 min after apnea, and at SpO2 < 70% by 7.9, 8.8, and 3.9%. Landiolol decreased TOI by 0.8, 2.6, and 4.4% from the respective values at baseline. During anemia, these changes decreased with dobutamine and increased with landiolol administration. Dobutamine (or landiolol) shifted the relationship between TOI and arterial hemoglobin oxygen saturation or arterial partial pressure of oxygen to the right (or left) and increased (or decreased) TOI at similar arterial blood oxygenation.
CONCLUSIONS
Dobutamine increases cerebral oxygenation during hypoxia and/or anemia and might be effective in improving neurological outcomes in ischemic cerebral injury.
