There are several reports in the literature of hyponatremia (sometimes severe) developing in patients undergoing coronary angiography or routine IV contrast CT studies. ^1-3 Although generally asymptomatic, severe hyponatremia with symptoms may also occur, particularly in those at risk of hyponatremia due to other factors.  

In a case series of 5 patients with advanced renal disease who underwent cardiac catheterization and developed post-procedure hyponatremia, the mean plasma sodium concentration decreased from 138.6 mEq/L to 122.6 mEq/L within 2-22 hours post-procedure; no patient had any neurological symptoms associated with hyponatremia. There was a strong correlation between dose of contrast administered and change in sodium level. ²

Severe symptomatic hyponatremia (confusion, stupor) was also reported in an elderly woman with blood creatinine of 0.9 mg/dL following coronary angiography (baseline plasma sodium 142 mmo/L vs. 115 mmol/L >16 hours post-procedure).  The authors suggested that a diagnosis of hyponatremia be considered in any patient who develops behavioral or neurologic manifestations after coronary angiography.³

Aside from coronary angiography, a prospective study among 103 adults (mean serum creatinine 0.79 mg/dl) undergoing contrast-enhanced CT found a drop in serum sodium from a mean concentration of 136 mmol/L to 132 mmol/L 24 hours after the procedure without any associated symptoms.¹

Potential mechanisms for the development of hyponatremia after IV contrast studies include hemodilution due to translocation of fluid from intracellular space caused by high osmolality of the contrast media.¹  

Bonus Pearl

Did you know that even the newer “low osmolar contrast” agents are more than 3 times the osmolality of blood?⁴

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References

1. Sankaran S, Saharia GK, Naik S, et al. Effect of iodinated contrast media on serum electrolyte concentrations in patients undergoing routine contrast computed tomography scan procedure. Int J Appl Basic Med Res 2019;9:217-220. https://www.ijabmr.org/article.asp?issn=2229-516X;year=2019;volume=9;issue=4;spage=217;epage=220;aulast=Sankaran
2. Sirken G, Raja R, Garces J, et al. Contrast-induced translocational hyponatremia and hyperkalemia in advanced kidney disease. Am J Kidney Dis 2004;43:e9.1-e9.5. https://www.sciencedirect.com/science/article/abs/pii/S0272638603013854?via%3Dihub
3. Jung ES, Kang WC, Jang YR, et al. Acute severe symptomatic hyponatremia following coronary angiography. Korean Circ J 2011;41:552-554. https://europepmc.org/article/pmc/pmc3193049
4. Bucher AM, De Cecco CN, Schoefpf UJ, et al. Is contrast medium osmolality a causal factor for contrast-induced nephropathy? BioMed Res International 2014; Volume 2014, article ID 931413. https://www.hindawi.com/journals/bmri/2014/931413/

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