Mr. S is a 73-year-old man, with a history of severe coronary artery disease, peripheral vascular disease, and stroke. He suffers from right hemiplegia and mild expressive aphasia. He is awake and alert, and presents for right below the knee amputation (BKA) for vascular insufficiency. His chart carries a DNR order. In the holding area prior to surgery, the anesthesiologist discusses the DNR order with Mr. S, who appears depressed. Mr. S states unequivocally, that he does not wish CPR in the OR, regardless of its cause or positive prognosis. He tells his anesthesiologist that he is willing to go "so far, and no more." The patient agrees to subarachnoid anesthesia (spinal block) and sedation. He is not intubated. After about 20 minutes, the patient complains of weakness in his arms, and difficulty breathing. Within 3 minutes, his blood pressure and heart rate fall, and he abruptly arrests.

Should the patient be intubated and CPR commenced?