You receive a call to a residence for a sick patient. Upon your arrival, you find the patient, a 53-year-old diabetic male, lying down on his front porch. His wife tells you that he had been mowing the lawn in the heat for the past 3 hours. The patient is confused and has hot, moist skin. His pulse is weak and thready, and his blood pressure is 90/50 mm Hg. In addition to administering 100% oxygen, you should: