A YOUNG WOMAN SUSTAINS A SEVERE HEAD INJURYAS ARESULT OF A MOTOR VEHICLE CRASH IN THE EMERGENCY DEPARTMENT HER GCS IS 6.HER BLOOD PRESSURE IS 140/90MM HG AND HER HEART RATE IS 80 BEATS PER MINUTE .SHE IS INTUBATED AND MECHANICALLY VENTILATED. HER PUPILS ARE 3MM IN SIZE AND EQUALLY REACTIVE TO LIGHT. THERE IS NO OTHRER PRIMARY INJURY. THE MOST IMPORTANT PRINCIPLE TO FOLLOW IN THE EARLY MANAGEMENT OF HER HEAD INJURY IS TO