This book discusses and explains the importance of biochemistry knowledge in understanding what happens to patients during anesthesia and/or to those being in intensive care. It covers a wide range of topics, such as Cerebral Edema, Shock, Blood-Brain Barrier, The Pulmonary surfactant, The Acid   Base equilibrium, Local anaesthetics, Perineural adjuvants, Normobaric Oxygen Therapy, Theories of Narcosis. Hyperventilation effects and consequences are also presented. For instance, by hyperventilating a patient with a PaCO2 significantly below 25 mmHg, we risk blocking pyruvic acid carboxylation and transforming it into oxalacetic acid, which in turn knocks out the Krebs cycle, possibly leading to a complication, i.e. to metabolic acidosis and not to compensation for respiratory alkalosis. It is also worth remembering that vitamins are actually molecules of pretty considerable potency and should not be simply intended as integrators.