A Contemporary Narrative Review of Sodium Homeostasis Mechanisms, Dysnatraemia, and the Clinical Relevance in Adult Critical Illness

Amongst critically ill patients managed in the intensive care unit (ICU) setting, disorders of sodium and water balance, or dysnatraemias, are commonly encountered either at time of admission or during ICU stay. There is extensive literature associating both extremities of incident dysnatraemia, hyponatraemia, and hypernatremia, with higher mortality and morbidity amongst a range of ICU disease populations. Therefore, a comprehensive understanding of sodium homeostasis mechanisms, effects of deranged sodium physiology, comprehensive diagnostic workup, and avoidance of suboptimal management are paramount to the critical care clinician. This narrative review incorporated a PubMed search to summarise contemporary literature perspectives of (a) sodium homeostasis mechanisms, (b) descriptions of dysnatraemia, (c) ICU-specific challenges to dysnatraemia diagnosis, (d) associated clinical outcomes in critically ill populations, and (e) ongoing paucity to deranged sodium physiology literature relevant to daily ICU practice. The purpose of this review is to both guide critical care clinicians towards performing a diagnostic approach to dysnatraemia with integrated physiology for a tailored treatment strategy as well as highlight ongoing research priorities in the realm of deranged sodium physiology.