From the Guidelines
Hypernatremia in a head trauma patient on lithium with intraparenchymal hemorrhage and midline shift is most likely caused by a combination of factors including diabetes insipidus, lithium's effects on renal water handling, and potentially the use of hypertonic saline for cerebral edema management. The patient's traumatic brain injury can damage the hypothalamus or pituitary stalk, leading to central diabetes insipidus with excessive free water loss 1. Additionally, lithium can cause nephrogenic diabetes insipidus by reducing the kidney's response to antidiuretic hormone (ADH), further exacerbating water loss.
The use of hypertonic saline to manage cerebral edema associated with the hemorrhage and midline shift can directly increase serum sodium levels. However, according to the most recent guidelines, prolonged hypernatremia is not recommended for controlling intracranial pressure in severe traumatic brain injury patients 1. Osmotic diuresis from mannitol administration for intracranial pressure control could also contribute to hypernatremia.
Immediate management should include:
- Careful fluid balance assessment
- Potentially adjusting or discontinuing lithium if possible
- Administering hypotonic fluids or desmopressin as appropriate
- Continuously monitoring neurological status and serum sodium levels to prevent rapid corrections that could cause osmotic demyelination syndrome. It is crucial to correct hypernatremia at a rate of 10-15 mmol/l/24 h to avoid cerebral edema, seizures, and neurological injury 1.
From the Research
Causes of Hypernatremia in Head Trauma Patients
- Hypernatremia can be caused by various factors, including poor thirst, diabetes insipidus, iatrogenic sodium administration, and primary hyperaldosteronism 2
- In patients with severe brain injury, hypernatremia is independently associated with increased mortality and complications rates 2
- The use of hypertonic saline to target mild hypernatremia in patients with head trauma may not have a significant effect on intracranial pressure (ICP) 3
Relationship Between Serum Sodium and Intracranial Pressure
- There is no correlation between serum sodium and maximum ICP in patients with traumatic brain injury (TBI) 3
- The number of interventions for elevated ICP per day is lower in patients with a mean serum sodium of 145 to 155 mEq/l compared to those with a mean serum sodium of < 145 or > 155 mEq/l 3
Management of Hypernatremia in Head Trauma Patients
- Close monitoring of serum sodium and osmolarity is important in acute head-injured patients to prevent cerebral edema 4
- The strategy of vigilant avoidance of hyponatremia is currently a safer, potentially more efficacious paradigm for managing cerebral edema 5
- Serum sodium concentration must be tightly monitored in the intensive care unit to prevent complications associated with hypernatremia 2