Relationship between hypernatremia and urine sodium in 133 patients with critical illness

Objective To discuss the relationship between hypernatremia and urine sodium, as well as the relationship between urine sodium and severity of disease and prognosis. Methods Information of 113 ICU patients (373 days) was collected. All cases were divided into 3 groups according to the normal range of blood sodium level (135 mmol/L- 145 mmol/L), as hypernatremia group (n =262) , normal blood sodium group (n =84) and hyponatremia group (n =27). All cases were divided into another 3 groups according to the normal range of 24 h urine sodium level (130 mmol-260 mmol), as low urine sodium group (n =158) , normal urine sodium group (n =146) and high urine sodium group (n =69). Blood sodium level, intake and output volume, 24 h urine sodium level, amount of sodium intake, creatinine and etc. were compared among the groups. Relationship between urine sodium and severity of disease, as well as relationship between urine sodium and prognosis were further analyzed. Results ①Average level of urine sodium in hypernatremia group was lower than that in normal blood sodium group [(156.8 ±109.1) mmol vs. (193.4 ±127.1) mmol, P <0.05]. ②Average creatinine level and average APACHEⅡ score in low urine sodium group were both higher than those in normal urine sodium group [(134.0 ±88.6) μmol/Lvs. (103.3 ±55.5) μmol/L, (26.5 ±10.4) vs. (19.7 ±6.9), and P <0.05]. ③The 28-day mortality in low urine sodium group is higher than that in normal urine sodium group (60.7% vs. 16.7%, P <0.01). Conclusions Decrease in urine sodium excretion is an important cause for hypernatremia, and it's related to the severity of disease and prognosis. Key words: Intensive care; Critical disease; Electrolyte disturbance; Hypernatremia; 24 h urine sodium; Creatinine; APACHEⅡ score; 28-day mortality