EFFECTS OF MEDETOMIDINE ADMINISTRATION ON INTRACRANIAL-PRESSURE AND CARDIOVASCULAR VARIABLES OF ISOFLURANE-ANESTHETIZED DOGS

Intracranial pressure and cardiovascular variables after nr administra tion of medetomidine (0.03 mg/kg of body weight) were evaluated in 6 h ealthy, mixed-breed dogs anesthetized with 1.3% end-tidal isoflurane c oncentration and mechanically ventilated to normocapnia (Pa-co2, 35 to 45 mm of Hg). Baseline values were determined for intracranial pressu re, heart rate, arterial blood pressure, cardiac output, mean pulmonar y artery pressure, pulmonary capillary wedge pressure, central venous pressure, end-tidal CO2 tension and isoflurane concentration, arterial pH and CO2 and O-2 tensions, and core body temperature. Cerebral perf usion pressure, cardiac index, systemic and pulmonary vascular resista nces, plasma HCO3- concentration, and base excess were calculated. Int racranial pressure was measured, using a calibrated, fiberoptic transd ucer placed within the brain parenchyma and secured to the calvarium b y means of a subarachnoid bolt. Cardiac output was determined by therm odilution. End-tidal CO2 tension and isoflurane concentration were det ermined, using an infrared gas analyzer. Administration of medetomidin e did not change intracranial pressure, but was associated with signif icant (P < 0.05) decreases in values for heart rate, cardiac index, en d-tidal CO2, and HCO3- and with significant increases in systolic, mea n, and diastolic pressure; pulmonary artery pressure; systemic vascula r resistance; central venous pressure; and pulmonary capillary wedge p ressure.