| Abstract: | The effects of ketamine on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2) and intracranial pressure (ICP) were evaluated in ventilated or spontaneously breathing goats after peripheral administration of 5 mg . kg-1 and central administration of 0.1-2.0 mg. In mechanically ventilated normocarbic goats intravenous ketamine 5 mg . kg-1 had no effect on CBF, but did produce a significant reduction in CMRO2 (4.3 +/- 0.4 vs 3.7 +/- 0.3 ml O2 . min-1/100 g) five minutes after injection. However, in spontaneously breathing goats, ketamine caused a significant increase in CBF (77 +/- 7 vs 109 +/- 12 ml . min-1/100 g), a significant reduction in CMRO2 (4.3 +/- 0.3 vs 3.8 +/- 0.4) and an increase of PCO2 from 4.5 +/- 0.5 to 5.4 +/- 0.9 kPa (34 +/- 4 to 41 +/- 7 torr). Small doses of ketamine (0.1-2.0 mg) injected directly into the cerebral circulation failed to cause any significant change in CBF. Intracranial pressure showed a significant increase from 13 +/- 3 to 19 +/- 3 mm Hg in spontaneously breathing goats and no change in ventilated goats. These data suggest that ketamine is a mild depressant of cerebral metabolic rate and has no other cerebral vascular effects. |
