EFFECTS OF HALOTHANE ANESTHESIA ON CEREBR AL BLOOD-FLOW VELOCITIES INCHILDREN

The effects of halothane on the cerebral circulation were studied in 2 3 children during general anaesthesia. Blood flow velocity in one midd le cerebral artery was recorded continuously by transcranial Doppler s onography. Furthermore arterial blood pressure, pulse rate, endtidal C O(2)partial pressure and endtidal halothane concentration were recorde d. Mean flow velocities/mean arterial blood pressures were 79 cm x s ( -1)/65 mmHg; 86 cm x s (-1)/61 mmHg; 78 cm x s (-1)/54 mmHg and; 67 cm x s(-1)/48 mmHg with 1; 1.5; 2 and 2.5 per cent endtidal halothane co ncentrations, respectively. Endtidal CO2-partial pressure and pulse ra te remained constant throughout the study. The higher cerebral blood f low velocities seen with 1.5 per cent halothane compared with 1 per ce nt can be explained by an increase in cerebral blood flow. The lower c erebral blood flow velocities and arterial blood pressure with 2.5 per cent halothane compared with 1.5 per cent indicate impaired cerebral autoregulation. However, cerebral blood flow appeared to be sufficient even with low arterial blood pressures.