ICU · Renal and metabolic
Acute severe hypernatraemia: causes, correction rate, and diabetes insipidus
Also known as Hypernatraemia · High sodium · Diabetes insipidus · Free water deficit
Hypernatraemia is a water deficit relative to sodium (or sodium gain). Severe bands in the correction-rate cohorts start at 155 mmol/L. Causes: free-water loss (central and nephrogenic diabetes insipidus, gastrointestinal and insensible losses), inadequate intake in the unconscious or intubated patient, and iatrogenic sodium load (hypertonic saline, bicarbonate, sodium-rich maintenance fluid). Correction is prompt and controlled: Brennan advises a reduction under 12 mmol/L per day with close electrolyte monitoring, while Feigin (n=4265, Na 155 or more) found slow correction at or under 0.5 mmol/L/h carried higher 30-day mortality than faster correction (50.7% vs 31.8%) without neurologic complications. Central DI: desmopressin plus free water; nephrogenic DI: water, thiazide plus amiloride, stop lithium.
Checked against its sources on 3 Sept 2026
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Red flags
- Severe hypernatraemia in the correction-rate cohorts is sodium 155 mmol/L or more — confusion, seizures, coma
- Correct promptly and in a controlled way — Brennan under 12 mmol/L per day with close monitoring; Feigin: over-slow correction (at or under 0.5 mmol/L/h) raised 30-day mortality
- Calculate the water deficit and replace ongoing plus insensible losses — formulas are projections, not a contract
- Diabetes insipidus: central → desmopressin plus free water; nephrogenic → water plus thiazide and amiloride, stop lithium
Meet the patient
A 58-year-old with new type 1 diabetes was intubated for severe DKA. At presentation, glucose 48 mmol/L and sodium 128 mmol/L — before acting on that sodium, correct it for the glucose, because hyperglycaemia dilutes the measured sodium by about 2.4 mmol/L for every 5.5 mmol/L rise. After 8 hours of insulin and 0.9% saline, the glucose is 18 but the sodium has climbed to 154 mmol/L, and he is passing 600 mL/h of urine with a urine osmolality of 280 mOsm/kg. Two cubicles down, a 36-year-old is day 7 after a traumatic brain injury with a sodium of 168, urine output 400 mL/h, and urine osmolality of 190 mOsm/kg on no diuretics.[10][4]
The two questions that decide the next hour are the same on every hypernatraemic patient: what is the volume status? (drives the fluid choice), and what is the urine doing? (concentrated or inappropriately dilute — that picks the cause). Hold those two and the rest of the topic slots into place.[1]
References21ShowHide
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- [2]Lindner G et al. Hypernatremia in critically ill patients. J Crit Care, 2013.PMID 22762930
- [3]Adrogué HJ et al. Aiding fluid prescription for the dysnatremias. Intensive Care Med, 1997.PMID 9083234
- [4]Christ-Crain M et al. Diabetes insipidus. Nat Rev Dis Primers, 2019.PMID 31395885
- [5]Chauhan K et al. Rate of Correction of Hypernatremia and Health Outcomes in Critically Ill Patients. Clin J Am Soc Nephrol, 2019.PMID 30948456
- [6]Cook AM et al. Guidelines for the Acute Treatment of Cerebral Edema in Neurocritical Care Patients. Neurocrit Care, 2020.PMID 32227294
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- [8]Brennan M, et al. Approach to the Management of Hypernatraemia in Older Hospitalised Patients. J Nutr Health Aging, 2021.PMID 34866143
- [9]Feigin E, et al. Rate of Correction and All-Cause Mortality in Patients With Severe Hypernatremia JAMA Netw Open, 2023.PMID 37768662
- [10]Hillier TA, et al. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med, 1999.PMID 10225241
- [11]Garrahy A, Thompson CJ Management of central diabetes insipidus. Best Pract Res Clin Endocrinol Metab, 2020.PMID 32169331
- [12]Kirchlechner V, et al. Treatment of nephrogenic diabetes insipidus with hydrochlorothiazide and amiloride. Arch Dis Child, 1999.PMID 10332005
- [13]Vaz de Castro PAS, et al. Nephrogenic diabetes insipidus: a comprehensive overview. J Pediatr Endocrinol Metab, 2022.PMID 35146976
- [14]Wells DL, et al. The relationship between serum sodium and intracranial pressure when using hypertonic saline to target mild hypernatremia in patients with head trauma. Crit Care, 2012.PMID 23068293
- [15]Kitabchi AE, et al. Hyperglycemic crises in adult patients with diabetes. Diabetes Care, 2009.PMID 19564476
- [16]Finken MJ, et al. Frequent occurrence of the triphasic response (diabetes insipidus/hyponatremia/diabetes insipidus) after surgery for craniopharyngioma in childhood. Horm Res Paediatr, 2011.PMID 21701131
- [17]Lopez DC, et al. Triphasic response after endoscopic craniopharyngioma resection and its dependency on infundibular preservation or sacrifice. J Neurosurg, 2023.PMID 36738460
- [18]Van Regenmortel N, et al. 154 compared to 54 mmol per liter of sodium in intravenous maintenance fluid therapy for adult patients undergoing major thoracic surgery (TOPMAST): a single-center randomized controlled double-blind trial. Intensive Care Med, 2019.PMID 31576437
- [19]Pedersen AN, et al. Desmopressin Dose Requirements in Adults with Congenital and Acquired Central Diabetes Insipidus. Horm Metab Res, 2024.PMID 37879354
- [20]Seay NW, Lehrich RW, Greenberg A Diagnosis and Management of Disorders of Body Tonicity-Hyponatremia and Hypernatremia: Core Curriculum 2020. Am J Kidney Dis, 2020.PMID 31606238
- [21]Yun G, Baek SH, Kim S Evaluation and management of hypernatremia in adults: clinical perspectives. Korean J Intern Med, 2023.PMID 36578134