I'm a newer ICU nurse, but I asked the same question of one of our Intensivist docs. He stated that current research suggests that for any patient with risk of increased ICP should maintain a MAP above 70 or more depending on physician preference since it is shown that 65 is needed for sufficient profusion and the extra is needed to perfuse the brain tissue in order to counteract the added pressure from swelling/bleeding or whatever is raising the ICP. For other patients he stated that often it just falls to physician preference and for him he titrates vasoconstrictive meds based on a SBP when the patient's baseline pulse pressure is widened. This is because the relative low DBP's can greatly affect what MAP calculation and make it less accurate in relflecting perfusion.... This helped me, I hope it helps you too.