 Intravenous access will be gained and non-invasive blood pressure measurements will be recorded every five minutes. Continuous electrocardiography and oxygen saturation monitoring will be maintained throughout the procedure and for at least 60 minutes afterwards. Light sedation will be provided, with the goal of maintaining verbal contact with the subject throughout the procedure. Where clinically appropriate, the study block may be preceded by an ultrasound-guided popliteal sciatic nerve block at the discretion of the attending anesthesiologist. 