Israel Medical Association Journal

Background: Hyponatremia is common among hospitalized children, including those with community acquired pneumonia. The prevalence and severity of hyponatremia were reported to correlate with disease. However, data regarding the association between hyponatremia and causative infectious pathogens are limited and results are inconsistent.

Objectives: To investigate the associations between sodium levels, severity and causative pathogen in children with pneumonia.

Methods: A retrospective study of all children (< 18 years) hospitalized with pneumonia from 1 January 2018 to 31 December 2020. Admission sodium levels were compared to the presumed etiological pathogens, clinical parameters, and inflammatory markers.

Results: Among 751 (52% males) children, 10 (1%) had sodium levels < 130 mEq/L, 187 (25%) had mildly decreased levels 130–134 mEq/L, and the remaining 554 (74%) had normal levels 135–145 mEq/L. Sodium levels < 130 mEq/L were found in 7/236 (3%) of the patients with presumed bacterial pneumonia, in 0/20 of patients with presumed atypical-bacterial, and in only 3/495 (0.6%) of the patients with a presumed viral infection, P < 0.001. Sodium levels < 135 mEq/L conferred an odds ratio of 3.1 (95% confidence interval [95%CI] 2.1–4.3) and levels < 130 mEq/L an odds ratio of 6.8 (95%CI 1.8–33.0) for bacterial infection, P < 0.001 for both. Hyponatremia was also inversely associated with high white blood cell counts, absolute neutrophil cell counts, and C-reactive protein levels.

Conclusions: Hyponatremia was common among children hospitalized with pneumonia and was associated with elevated inflammatory markers and presumed bacterial pneumonia.

Letter 1: "Not type 2" by Moti Ravid 

Letter 2: "Hyponatremia, hyperkalemia, and acute kidney injury: clues for the diagnosis of uroperitoneum in patients with new-onset ascites" by Zvi Ackerman and Samuel N. Heyman, 

Letter 3: "Surgery in Mauthausen Concentration Camp" by George M. Weisz

Background: Intrathoracic cancer can cause hyponatremia, but it is uncertain whether mild hyponatremia in the outpatient setting should be regarded as an early sign of intrathoracic cancer.

Objectives: To evaluate the risk of undiagnosed intrathoracic cancer in patients with new persistent mild hyponatremia.

Methods: We conducted a retrospective cohort study using the electronic health record database of a large healthcare organization. The hyponatremia group included patients with sodium concentration of 130–134 mmol/L twice, after a previous normal value and without previous history of cancer or diseases related to hyponatremia. A control group with normal sodium concentration was matched by sex, age, and year of testing. We measured specific intrathoracic cancer incidence during 3 years of follow-up after sodium concentration test date. A logistic regression was used to adjust for further clinical information including smoking history, symptoms, and medications.

Results: The study comprised 1539 participants with mild hyponatremia and 7624 matched controls. New intrathoracic cancer diagnosis was more common in the hyponatremia group during a 3-year follow-up; 1.49% in the hyponatremia group and 0.39% in the control group, crude odds ratio (OR) 3.84, 95% confidence interval (95%CI) 2.22–6.63. After adjustment, hyponatremia remained a significant risk factor for the diagnosis of intrathoracic cancer; adjusted OR 3.61, 95%CI 2.08–6.28.

Conclusions: New mild persistent hyponatremia might be a significant predictive marker to a yet undiagnosed intrathoracic cancer.