Effects of hemorrhage on the electroencephalograms in dogs anesthetized with ketamine, propofol and isoflurane

The effect of hemorrhage on the electroencephalogram(EEG) was investigated in fifteen mixed-breed dogs anesthetized with ketamine, propofol and isoflurane. Animals were randomly allocated to three groups (n = 5) by anesthetic agents; group 1 (ketamine 5 mg/kg, IV), group 2 (propofol 156 (μg/kg/min, IV) and group 3 (isoflurane 2.0% end-tidal concentration). Medetomidine (40 μg/kg, IM) was used in all dogs as a preanesthetic agent. Recording electrode for EEG was positioned at CZ. EEG, heart rate, systolic/diastolic blood pressure, pC0₂, p0₂, and blood pH were measured before anesthesia, after anesthesia and after every bleedings. Three bleedings were accomplished by drawing blood through the femoral artery catheter at a rate of 7 ml/kg (10% of total blood volume) for 10 minutes. In the course of hemorrhage, a systolic/diastolic pressure continuously decreased in all groups. The pC0₂, values and heart rates were increased in all groups. The p0₂, values were most significantly increased in group 1 compared with those in other groups. The pH values were not significantly changed. On statistical analysis of EEG, there was no significant changes in group 1 and 3. But in group 2, band 3, 4 and 7 were significantly altered after 2nd and 3rd bleeding. Power alterations of band 3, 4 and 7 were thought to be related with hemorrhage over 20% of total blood volume in group 2. In conclusion, the regulation of infusion rate would be considered when a dog, anesthetized with propofol, bleed over 20% of total blood volume.