- Serious, unstable medical illnesses including hepatic, renal impairment, gastroenterologic (including gastro-esophageal reflux disease), respiratory (including obstructive sleep apnea, or history of difficulty with airway management during previous anesthetics), cardiovascular (including ischemic heart disease and uncontrolled hypertension), endocrinologic, neurologic (including history of severe head injury), immunologic, or hematologic disease;