Comparison between Urine Sodium and Clinical Evaluation to Assess Saline Responsiveness in Severe Hyponatremia - A...

Hyponatremia is a commonly encountered electrolyte disturbance seen in diverse clinical settings. The recently published European guidelines comprehensively summarize the present status of evaluation for hyponatremia. The guidelines emphasize the poor predictability of clinical criteria and instead suggest that the urine sodium (UNa) may be a better way to initially evaluate the cause of hyponatremia.

Aim of the study is to comparison between urine sodium and clinical evaluation to assess saline responsiveness in severe hyponatremia.

Prospective Cross sectional study carried out in Departments of Nephrology, Kerala Institute of Medical Sciences, Thiruvananthapuram, Kerala. Study Period between October 2014 to October 2016 (2 years), Patients diagnosed as Severe hyponatremia S.Sodium < 125mEq/L based on clinical and laboratory evaluations.

All clinically and lab confirmed cases of severe hyponatremia, Age >18 years. Outpatients, Inpatients admitted to medical wards and ICU, who give informed consent and serum sodium of less than 125mEq/L constitute the study population. These patients meeting the following criteria: blood glucose level less than 200mg/dl would be included.

Patients with overt hypervolemia due to cardiac, hepatic, and renal disease with gross edema were excluded.

Among 50 patients in the study 70% were found at age group > 60 yrs. 30% patients were < 60 years age group. Youngest patient was 14 yrs old and oldest patient was 83 yrs old. 21 (42%) were Females and Males were 29 (58%). Majority of the cases were symptomatic at time of presentation n=38 (76%). All were having hypotonic hyponatremia among them 14 patients (28%) were euvolemic, 3 patients (6%) were hypervolemic and 33 patients (66%) were hypovolemic. 31 patients (62%) had serum Sodium levels between 115-125mEq/L and 19 patients (38%) had serum Sodium levels between 100-114mEq/L. Among the 33 patients (66%) Hyponatremia due to volume depletion by clinical assessment by the Nephrologist and who were given saline 26 (78%) were saline responsive and 7 patients (22%) were saline non responsive. Among the 7 patients who are saline non responders 6 patients (85.7%) had UNa > 20 and 1 patient (14.3%) had UNa < 20, which is statistically not significant (p=0.840). Among the 44 patients who are saline responders 18 patients are saline responsive. Among the 44 patients 20 (76.9%) had UNa > 20 and 6 (23.1%) had UNa < 20, statistically not significant (p=0.604). Duration for normalizing sodium was noted during the study 17 cases, 1-3 days were needed, 22 cases needed 4-7 days.

Volume status of patients with hyponatremia can be assessed clinically with a high degree of reliability if the hyponatremia is severe. Thus we re-emphasize the importance of measuring volume status in patients with hyponatremia and classify patients on basis of volume status prior to triaging management. The measurement of UNa had a poor correlation with saline responsiveness and this shows that the laboratory measure is subject to errors due to prior treatments given to the patient and has to be interpreted with the prior clinical scenario in mind.