A patient in emergency depament showed hypoxia without cyanosis. What is the most likely cause?
High-Yield Explanation
The presence of cyanosis is influenced by several factors, including site of observation, pH, temperature, and concentrations of adult and fetal hemoglobins. Cyanosis appears when the absolute concentration of reduced hemoglobin in aerial blood is greater than 4-5 g/dL. Because this amount of reduced aerial hemoglobin is necessary to produce cyanosis, a low hemoglobin concentration requires an aerial saturation of 60% to produce approximately 4 g/dL of deoxyhemoglobin and cyanosis. Ref: Ganong's physiology 22nd edition, chapter 37, Fundamentals of Human Physiology by Lauralee Sherwood, Page 371; Pediatric Hospital Medicine: Textbook of Inpatient Management By Ronald M. Perkin, Dale A. Newton, M.D., James D. Swift, M.D., 2007, Page 80