Background: Some case reports showed unexplained hyponatremia in patients with cardiac tamponade. Reversible hyponatremia was observed in these patients who received pericardial drainage. The occurrence rate of hyponatremia in patients of cardiac tamponade is not clearly known. The objective of this study was to identify the relationship between hyponatremia, cardiac tamponade and their underlying diseases.
Methods: We reviewed the clinical data of patients with cardiac tamponade and receiving pericardial drainage between January 2000 and January 2012 in our hospital. Cardiac tamponade was diagnosed by clinical presentation: hypotension, pulsus paradoxus, and increased jugular vein pressure. We used paired T test to compare the sodium change before and after pericardial drainage. Pearson's chi-square test was used to analyze the relationship of hyponatremia with malignancy and cardiac chamber compression proved by echocardiography.
Results: For the 48 patients, the mean pre-drainage sodium level was 129.1 ± 7.1 mEq/L and the mean post-drainage sodium level was 130.4 ± 5.6 mEq/L (p = 0.06). Among the 48 patients, 31 (65 %) had hyponatremia. For the 31 hyponatremia patients, the mean pre-drainage sodium level was 124.8 ± 4.9 mEq/L and the mean post drainage sodium level was 127.5 ± 4.5 mEq/L (p = 0.003). Hyponatremia was significantly associated with malignancy (p = 0.038). There was no significant change of pre-drainage and post-drainage sodium level in patients without malignancy. The post-drainage sodium level in the malignant patients significantly increased from 125.5 ± 8.0 to 129.1 ± 5.5 mEq/L (p = 0.017). The presence of hyponatremia was strongly associated with the cardiac tamponade sign (p < 0.001). After pericardial drainage, the sodium level significantly increased in patients with chamber compression than in patients without compression.
Conclusion: Hyponatremia is associated with cardiac tamponade especially for malignant pericardial effusion and for patients with cardiac chambers compression signs. Hyponatremia can be improved after pericardial effusion drainage.