Episode 16: Rapid Hyponatremia Correction


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Author: Dr. Suneet Sood
Editor: Dr. Suneet Sood
Narrators: Thong Yi Kun, Alan Koay


“Will my father be okay, Doctor?” Asks the young woman, pretty despite the worry. Her husband sits next to her, and, instinctively, she reaches for his hand.

“ Miss Chandra, I have to admit that the outlook looks somewhat grave,” “Professor Lee here is one of the leading neurologists in the state. says Dr. Chan, pointing towards me

“Oh.. He seemed to be getting better in the beginning, then…”

Dr. Chan is clearly uncomfortable. I feel a little sympathy for him.

I think of our conversations a few minutes ago.

Dr. Chan had called me in to see a 70-year-old man who had come in with disorientation following a history of diarrhoea. The man had been living alone, and his daughter had come by after a long absence. She found him disoriented, and rushed him to hospital when Dr. Chan had seen him.

Dr. Chan is a young man of about 30. He is sharp, but is just a little too confident for my liking. He had actually made a good clinical diagnosis. He said to me that he had thought of hyponatremia, and the lab reports had confirmed that the patient had sodium levels of only 118 millimoles per liter.  So he started an intravenous line with hypertonic saline.

“In fact, I had brought the hyponatremia back to normal by the evening! The patient’s orientation initially improved, then he started to worsen. The next day the patient developed quadriparesis. I checked his sodium levels, but they were within the normal range of 135-145 millimoles/L. I even tried to raise them, keeping the sodium close to 145, but the patient didn’t improve. Now I don’t know what’s going on.”

He hadn’t seen the look of horror on my face as he explained how quickly he corrected the sodium. Still, we all make mistakes.

I said, “This patient obviously had chronic hyponatremia, which is when hyponatremia lasts more than 48 hours. The hyponatremia was the cause of the symptoms, and your diagnosis was right, the patient needed sodium.”

Dr. Chan nodded vigorously, happy that I seemed to be with him, but I continued. “But, you see, we don’t replace sodium too quickly.”

Dr. Chan looked confused. “Too quickly?” he asked, not understanding.

“Yes, “I think we replaced his sodium levels too fast.”

“So, er, how long should we have taken?”

“Well, sodium levels should be raised by not more than 8 millimoles/24 hours. In this patient, the sodium was raised by over 20 mmol in less than a day.”

“How does this matter?”

“Sodium is responsible for most of the osmotic activity of the blood. Low sodium tends to produce brain edema, so the brain compensates by losing extracellular water, and by losing some intracellular sodium. If we replace all the sodium in the blood, the blood osmotic activity returns to normal, but the brain cells are unprepared. There is rapid demyelination in the brain, particularly in the region of the pons, but also in the cerebellum and other areas. Patients get dysphagia, dysarthria, quadriparesis, lethargy, even coma.”


“It’s called the Osmotic Demyelination Syndrome (ODS).”

“Will he recover?”

“The outlook is bad, but some degrees of recovery are possible.”

“What should I tell the patient’s relatives?”

“The truth,” I said.

“But they’ll sue me!”

“We’ll take the chance. Come, I’ll sit with you while you tell them. That way you’ll feel more confident,”



Hegazi MO, Nawara A (2016) Prevention and Treatment of the Osmotic Demyelination Syndrome: A Review. JSM Brain Sci 1(1): 1004.

Koul PA, Khan UH, Jan RA, Shah S, Qadri AB, Wani B, Ashraf M, Ahmad F, Bazaz SR. Osmotic demyelination syndrome following slow correction of hyponatremia: Possible role of hypokalemia. Indian J Crit Care Med. 2013 Jul-Aug; 17(4): 231–233.

Lin S-H, Jsu Y-J, Chiu J-S, Davids MR, Halperin ML. Osmotic demyelination syndrome: a potentially avoidable disaster. QJM: An International Journal of Medicine, Volume 96, Issue 12, 1 December 2003, Pages 935–947, https://doi.org/10.1093/qjmed/hcg159

Simon EE. Hyponatremia. Medscape, updated 6 Jan 2016, accessed 24 Mar 2018, accessible at https://emedicine.medscape.com/article/242166-overview

Episode 15: Blood transfusions
Episode 17: Right sided neck lump

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