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Prevalence and clinical setting of SIADH in neurosurgery: comparison between subarachnoid haemorrhage and head trauma


The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a very important disorder in neurosurgery, and it is one of the most common causes of hyponatriemia in acute brain injury. SIADH should be suspected in any patient with hyponatremia, hypo-osmolarity, urine osmolality above 100 mosmol/kg H2O, concentration of sodium in the urine usually above 40 mEq/l, and clinical euvolemia. This study was designed to assess the frequency of this syndrome in the post-neurosurgery ICU, the time of onset and the duration of symptoms.


In a 2-year period (2008 to 2009), 131 patients, hospitalized in a post-neurosurgery ICU for TBI or ESA were retrospectively studied. According to the previous definition, 63 patients had subarachnoid haemorrhage (SAH) from rupture of aneurysm and 68 patients had severe head trauma (HI). Diagnosis of SIADH was confirmed by pH, sodiemia, plasmatic and urinary osmolality, sodiuria of 24 hours and central venous pressure. The time to onset of hyponatremia during hospitalization in ICU was evaluated, and its duration despite adequate treatment (fluid restriction and eventually hypertonic saline).


Patients developed SIADH in 5.34%. Three patients had a subarachnoid hemorrhage and four patients were hospitalized for head trauma. The onset of this syndrome was within the first week in two patients with SAH and in only one with traumatic head injury. With regard to the duration of symptoms, SIADH lasted more than a week in the most of patients, with no differences between the two groups.


In patients with hyponatriemia, an adequate diagnosis of SIADH is very important in order to improve the outcome, especially in the ICU. In this study we found no differences in the SIADH setting between patients with subarachnoid haemorrhage and in patients with traumatic head injury. But, owing to the small number of patients with this syndrome enrolled, this trend has to be confirmed in further studies.

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Correspondence to FD Di Sacco.

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Di Sacco, F., Demi, A., Bernardeschi, G. et al. Prevalence and clinical setting of SIADH in neurosurgery: comparison between subarachnoid haemorrhage and head trauma. Crit Care 14, P356 (2010).

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  • Public Health
  • Sodium
  • Clinical Setting
  • Brain Injury
  • Emergency Medicine