ASSESSMENT OF HYPONATRAEMIA IN ACUTE MEDICAL PATIENTS.

Editor

Hyponatraemia is defined by a sodium level of less than 135mmol/L and is the commonest electrolyte abnormality, occurring in 15-20% of hospital patients [1]. It has also been identified as an independent predictor of mortality and is associated with severe complications such as cerebral oedema [2,3]. Despite this, the management of hyponatraemic patients has been poor [1,4].

The aim of our study was to evaluate the assessment of hyponatraemia in newly admitted hospital patients.

METHODS

Our study was a retrospective data collection analysis. Using data provided by the Biochemical laboratory at a South London hospital, we analysed patients that were admitted to their Acute Medical Unit with sodium levels below 133mmol/L (the trust’s definition), across July and August 2017. Patients were excluded if their hyponatraemia developed after their Post-take ward round or if it was in the context of a hyperglycaemia (>20mmol). We separated patients by severity of their hyponatraemia – mild 130-133, moderate 120-130 and severe <120 - then further analysed data within these groups. Our analysis focused on the period between the patient’s admission clerking notes and their posttake ward round notes – however we did look further in their notes to look at whether they had been admitted to ITU in that respective admission.

RESULTS

Our study revealed that 101 patients were admitted to AMU with hyponatraemia during the July-August 2017 period. 53/101 (52%) patients had their glucose checked. 2/53 were revealed to have a glucose level of above 20mmol/L and therefore had pseudohyponatraemia. We have excluded these two patients from further analysis. For the new patient group of 99 patients: 36 had mild hyponatraemia (130-133mmol/L), 51 had moderate hyponatraemia (120-130mmol/L) and 12 had severe hyponatraemia (<120mmol/L)

Reassuringly, all patients with severe hyponatraemia had this documented in their notes (12/12 100%), followed by the moderate category with 34/51 (67%), and the mild with 10/36 (28%). However, there was no such relationship between severity and volume assessment. Only 34% of patients had a volume assessment in the context of their low sodium (mild 28%, moderate 31%, and severe 67%).

Urinary sodium was poorly requested in the mild and moderate categories (0% and 7.8% respectively). Although, in severe hyponatraemia 75% of patients had a urinary sodium test requested. For good practice, it is recommended to check glucose levels AND request a urinary sodium in all patients presenting with hyponatraemia. This occurred in 7% of patients (including 2 excluded earlier). The majority of these patients (4/7) had severe hyponatraemia.

4/99 patients had their care escalated to the intensive care unit eventually at some point during their admission. However none of these patients were admitted with severe hyponatraemia.

CONCLUSION

Overall: 1. The recognition and investigation of hyponatraemia in acute patients is poor; although there is some improvement with increasing severity of hyponatraemia. 2. Investigations for hyponatraemia – blood glucose, urinary sodium and volume status assessment – aren’t performed in all patients. 3. The majority of hyponatraemic patients do not become critically ill requiring ITU admission.