Understanding blood gases/acid–base balance

Acid–base balance is regulated by intracellular & extracellular buffers and by the renal and respiratory systems. Normal pH is necessary for the optimal function of cellular enzymes and metabolism. Disorders of acid–base balance can interfere with these physiological mechanisms leading to acidosis or alkalosis and can be potentially life threatening. Blood gas analysis is a routine procedure performed in the neonatal unit and combined with non-invasive monitoring, aids in the assessment and management of ventilation and oxygenation and provides an insight into the metabolic status of the patient. The following discussion details the basic terminology and pathophysiology of acid–base balance and the main disorders. It aims to provide a logical and systematic approach to the understanding and interpretation of blood gases in the newborn period. The application of these concepts, together with relevant history and examination, will help the clinician assess the medical condition, make therapeutic decisions and evaluate the effectiveness of any intervention provided.