- Patients with severe comorbidities, including but not limited to: (i) previous stroke with persistent cognitive, motor, etc deficits; (ii) recent (<6 months) myocardial infarction or current unstable angina; (iii) liver cirrhosis; (iv) severe chronic obstructive pulmonary disease (COPD)/respiratory disease. Patients must be suitable candidates for either spinal or general anesthesia.