Electrolytes: The Salts of the Earth

What do you need to know as medical laboratory scientists when performing plasma electrolyte analysis? What new information should you consider regarding best laboratory practice in electrolyte analysis? This review article will answer some of these questions. Background In human physiology it is best to refer to electrolytes, the main component in bodily fluids, in the context of extracellular fluid (ECF) volume and total water (H 2 O) content in the body. Electrolytes are also best referenced collectively rather than individually because they are part of an integrated physiological mechanism of H 2 O and ionic balance. Thirst, renal function, and hormonal response help to maintain homeostasis of electrolytes. 1 These entities play a role in general functions of metabolic pathways, enzyme activation, acid-base balance, muscular-function regulation, and nervous-tissue contractions. Control of electrolyte levels is based on H 2 O and pH balance and is enacted by the renal glands through processes such as active transport in the proximal convoluted tubules, osmosis, and passive diffusion. At a cellular level, sodium (NA) and potassium (K) levels are maintained by the Na-K–adenosine triphosphatase (ATPase) pump. 1 The endocrine system influences the distal convoluted tubules via the renin-aldosterone system and the circulating levels of vasopressin and natriuretic peptides in bodily fluids.