Variability in Serum Sodium Concentration and Prognostic Significance in Severe Traumatic Brain Injury: A Multicenter Observational Study

Abstract

Background/Objective: Dysnatremia is common in severe traumatic brain injury (TBI) patients and may contribute to mortality. However, serum sodium variability has not been studied in TBI patients. We hypothesized that such variability would be independently associated with mortality.Methods: We collected 6-hourly serum sodium levels for the first 7 days of ICU admission from 240 severe TBI patients in 14 neurotrauma ICUs in Europe and Australia. We evaluated the association between daily serum sodium standard deviation (dNaSD), an index of variability, and 28-day mortality.Results: Patients were 46 ± 19 years of age with a median initial GCS of 6 [4 -8]. Overall hospital mortality was 28%. Hypernatremia and hyponatremia occurred in 64% and 24% of patients, respectively. Over the first 7 days in ICU, serum sodium standard deviation was 2.8 [2.0 -3.9] mmol/L. Maximum daily serum sodium standard deviation (dNaSD) occurred at a median of 2 [1-4] days after admission. There was a significant progressive decrease in dNaSD over the first 7 days (coefficient -0.15 95%CI [-0.18 --0.12], p<0.001). After adjusting for baseline TBI severity, diabetes insipidus, the use of osmotherapy, the occurrence of hypernatremia and hyponatremia and center, dNaSD was significantly independently associated with 28-day mortality (HR 1.27 95%CI (1.01-1.61), p=0.048).Conclusions: Our study demonstrates that daily serum sodium variability is an independent predictor of 28-day mortality in severe TBI patients. Further prospective investigations are 5 necessary to confirm the significance of sodium variability in larger cohorts of TBI patients and test whether attenuating such variability confers outcome benefits to such patients.

Clinical descriptors of disease trajectories in patients with traumatic brain injury in the intensive care unit (CENTER-TBI): a multicentre observational cohort study

“…That sodium variation is an important descriptor of early ICU stay could be a biological effect, but probably more reflects aggressive use of hypertonic saline boluses to treat increased intracranial pressure. Harrois and colleagues have identified an association between sodium variability and mortality, 29 and rapid changes in sodium levels may induce osmotic neuronal injury. We hypothesise that as an important descriptor of ICU trajectories in TBI patients, sodium variation is more highly related to treatment intensity than biological effects.…”

Trauma‐related electrolyte disturbances: From resuscitation to rhabdomyolysis

“…17 The other group of patients at high risk for sodium abnormalities are those with traumatic brain injuries (TBIs), which has an incidence of hyponatremia and hypernatremia of 15%-55% and 30%-64%, respectively. 18 The cause of dysnatremia in this population is multifactorial but includes both iatrogenic causes (osmotherapy, saline administration) and hormonal abnormalities particulary from disrupted hypothalamic-pituitatry pathways. 19,20 Complicating the care of these patients is that the two most common causes of hyponatremia in TBIs (cerebral salt wasting and the syndrome of inappropriate ADH secrection) can be difficult to accurately diagnose and requires different treatment strategies.…”

“…Elderly patients, in particular, have a prevelance of hyponatremia up to 26% 16 and there is evidence that hyponatremic elderly patients with fall‐related injuries have worse outcomes compared with those with normal sodium levels 17 . The other group of patients at high risk for sodium abnormalities are those with traumatic brain injuries (TBIs), which has an incidence of hyponatremia and hypernatremia of 15%–55% and 30%–64%, respectively 18 . The cause of dysnatremia in this population is multifactorial but includes both iatrogenic causes (osmotherapy, saline administration) and hormonal abnormalities particulary from disrupted hypothalamic‐pituitatry pathways 19,20 .…”