Recognizing Acute Dilutional Hyponatremia Dangers

Excessive water intake poses significant risks of acute dilutional hyponatremia, warranting greater awareness of its dangers.

July 2023
Recognizing Acute Dilutional Hyponatremia Dangers

Case presentation

A previously healthy 30-year-old man was airlifted to hospital due to acute confusion . After a planned day off from work, his wife found him standing naked in the bedroom in an agitated and disoriented state with unintelligible speech and called emergency services. During a telephone conversation 3 hours earlier, he had complained of nausea and a headache.

In the emergency department, the patient was inarticulate and appeared confused and combative. He was feverish. His pupils were equal and reactive and his neck was flexible. No signs of lateralization were observed. There was no eruption. He was sedated with propofol and midazolam.

An emergency CT scan of the skull revealed no abnormalities. He was a smoker but did not take recreational drugs. He was not taking any medication. Three days earlier, while he was chopping wood, a small tile had hit his forehead and left a small scar just above his left eye socket. A day before his admission, he had attended an appointment with the dentist.

Laboratory results revealed severe hypotonic hyponatremia (Na: 113 mEq/l); Blood glucose, kidney and liver functions were within the normal range, and inflammatory markers were not elevated. A urine toxicology screen was negative and alcohol levels were normal.

Urinary Na was <20 mEq/L and urinary osmolality was 29 mOsmol/kg. The patient remained sedated in intermediate care. He received 250 ml of 3% saline and empirical antibiotic coverage with ampicillin/sulbactam. Over the next 35 hours, he passed 9,450 mL of urine, equivalent to a net fluid deficit of 7,100 mL. In parallel, Na levels increased to 138 mEq/l.

Differential diagnosis

Initially, the diagnosis was acute hyponatremia associated with recent head trauma, causing inappropriate antidiuresis syndrome (ISA). However, the biochemical results were more consistent with a low-solute form of hyponatremia, but the history and negative alcohol levels did not suggest beer addiction.

Given the reported head trauma, a pituitary lesion causing secondary adrenal insufficiency was considered . In view of the acute onset of confusion and hyponatremia, a diagnosis of limbic encephalitis was also considered . A viral infection remained a remote possibility, specifically tick-borne encephalitis, which is endemic in this part of Austria. Although acute psychosis itself may be a cause of AIS, this was considered probable in the differential diagnoses.

Deeper investigations

Due to suspicion of viral or paraneoplastic encephalopathy, an MRI and lumbar puncture were performed, with normal results . There were no focal findings on the electroencephalogram. Adrenal and thyroid function tests were normal.

Evolution and outcome of the case

Twenty-two hours after admission, sedation was discontinued and the patient quickly woke up and regained coherence. He was moved to a regular ward the next day. He could now provide a detailed history: a diseased molar had been bothering him for several weeks, before the pain became unbearable, prompting an urgent appointment with the dentist on Monday morning when the tooth was duly extracted. Although the patient had been given painkillers, he found that drinking cold water relieved the pain best and, therefore, he began drinking large amounts of water.

The next morning, the wound was still sore. Over the next 5 hours, she drank about 10 liters of water.) On this day, her food intake consisted of only one bun. The last memory of him was the phone call from his wife at lunch time. Due to his sweaty work in a constantly hot environment, consuming a generous amount of fluids was second nature to him. On a normal work day, he typically drank 5 to 6 liters of water.

The final diagnosis was acute dilutional hyponatremia due to excessive water intake to relieve his toothache. The patient developed rhabdomyolysis (peak creatine kinase of 43,244 U/l); However, renal function remained normal throughout his hospital stay, and the patient was discharged after 1 week in his usual state of health. The trivial frontal wound had been a red herring .

Comments

Acute water intoxication is mainly seen in psychiatric patients, with primary polydipsia and anorexia nervosa representing the main examples. Water intoxication without psychiatric causes has also been reported following urine drug screening, colonoscopy preparation, in association with exercise or with drugs (particularly ecstasy). Cerebral edema is a feared consequence and symptoms can progress rapidly from confusion to seizures and coma; the feared result is brain herniation.

Acute symptomatic hyponatremia is best treated with a bolus of hypertonic Na chloride (3%). A rapid increase in Na levels (by approximately 4 mEq/L) is usually sufficient to relieve symptoms.

If hyponatremia develops within hours, the brain does not have time to fully adapt; Therefore, the risk of osmotic demyelination syndrome in this context is zero. The impressive aquaresis documented in our patient was the result of persistent and adequate suppression of antidiuretic hormone, resulting in excretion of dilute urine and rapid normalization of Na levels.

The ability of the kidneys to eliminate water is generally very important. The traditional teaching is that eunatremia persists even in the face of water intake close to 20 liters per day. However, renal water excretion also depends on the amount of solutes in the diet, mainly in the form of protein (metabolized to urea) and salt.

If a diet is essentially lacking in such solutes, the maximum urinary volume decreases significantly. Since the maximum hourly water excretion cannot exceed 1 liter, the rate of water intake is the second major mechanism for the development of dilutional hyponatremia. If liquid is ingested in a very short time, hyponatremia will invariably occur.

Water intoxication in the "dental context" is rare and appears to be best recognized in children and adolescents. The authors were only able to retrieve one adult case report involving a 25-year-old woman who developed symptomatic hyponatremia secondary to prolonged consumption of ice water during relief of dental pain. The development of ’dental hyponatremia’ in a robust man with no other health conditions seems unique and provides a warning that even water can be much more than a good thing.

​Key points

 • Urinary indices are key in the assessment of dysnatremia.

 • The initial diagnosis of hyponatremia depends on the level of antidiuretic hormone (urine osmolality provides a viable indicator).

 • Severe neurological manifestations of hyponatremia require urgent treatment with hypertonic saline.

 • Excessive fluid intake can overwhelm the kidney’s water elimination capabilities.

 • The dangers of excessive drinking deserve better recognition.