Case studies in physiology: oxygenation during general anesthesia and thoracic surgery in a patient with Titusville low-oxygen affinity hemoglobin.

The purpose of this case study is to describe the physiologic characteristics of a patient with the low-oxygen affinity Titusville hemoglobin variant. A 46-year-old man with exertional dyspnea was diagnosed with a mediastinal lymphadenopathy of unknown origin and, to obtain definitive diagnosis by biopsy, underwent endobronchial ultrasound-guided transbronchial needle aspirate under sedation and video-assisted thoracoscopy under general anesthesia. High inspired fraction of oxygen (FIO2 ) was used to guarantee adequate oxygenation even during the one-lung ventilation needed for thoracoscopy. Following radial and pulmonary arterial catheterization, continuous mixed-venous oxygen saturation (SvO2 ), cardiac output, oxygen delivery (DO2 ), oxygen consumption (VO2 ) and oxygen extraction ratio (ERO2 ) were measured. Serial blood gas analyses were obtained at different FIO2 . Anesthesia and surgery were carried out safely. Data obtained during the clinical case were utilized 1) to construct an in vivo Titusville hemoglobin dissociation curve and 2) to describe oxygen delivery and consumption of a human with Titusville mutation. Titusville hemoglobin showed relatively high P50 (i.e., 30 vs. normal of 27), and very low cooperativity (Hill coefficient of 1.45 vs. normal 2.27), which was compensated in our patient by increases in cardiac output, rather than by augmenting oxygen extraction.