Abstract
Hyponatremia is a frequent electrolyte imbalance in hospital inpatients. Acute onset hyponatremia is particularly common in patients who have undergone any type of brain insult, including traumatic brain injury, subarachnoid hemorrhage and brain tumors, and is a frequent complication of intracranial procedures. Acute hyponatremia is more clinically dangerous than chronic hyponatremia, as it creates an osmotic gradient between the brain and the plasma, which promotes the movement of water from the plasma into brain cells, causing cerebral edema and neurological compromise. Unless acute hyponatremia is corrected promptly and effectively, cerebral edema may manifest through impaired consciousness level, seizures, elevated intracranial pressure, and, potentially, death due to cerebral herniation. The pathophysiology of hyponatremia in neurotrauma is multifactorial, but most cases appear to be due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Classical treatment of SIADH with fluid restriction is frequently ineffective, and in some circumstances, such as following subarachnoid hemorrhage, contraindicated. However, the recently developed vasopressin receptor antagonist class of drugs provides a very useful tool in the management of neurosurgical SIADH. In this review, we summarize the existing literature on the clinical features, causes, and management of hyponatremia in the neurosurgical patient.
Highlights
Hyponatremia is the most frequent electrolyte imbalance encountered in hospital inpatients
Of patients admitted for Traumatic Brain Injury (TBI) [1,2,3] and over 50% of patients admitted for Subarachnoid Hemorrhage (SAH) [4,5,6] develop hyponatremia
Moderate to severe hyponatremia is known to increase inpatient mortality [8,9,10,11,12], and recent data suggest that even mild hyponatremia may confer an adverse prognosis in diverse patient groups, including those with pneumonia [13], those in intensive care [14] and those in the community [15,16]
Summary
Hyponatremia is the most frequent electrolyte imbalance encountered in hospital inpatients. It is especially frequent in patients suffering from neurosurgical insult or intervention. Over 2–4 days in most of these conditions, it is more likely to be associated with cerebral edema, and to produce symptoms of cerebral irritation. As acute hyponatremia is associated with reduced conscious level, the development of this complication may impair the ability of the neurosurgical patient to engage with physiotherapy and rehabilitation. There are data from a number of centers which highlight the prolongation of hospital stay associated with hyponatremia of multiple etiologies [4,17,18,19,20,21]. As hyponatremia occurs so frequently in neurosurgical patients, management is important. In this review we will explore the pathophysiology of hyponatremia in neurotrauma with particular reference to the role of vasopressin, and provide a brief summary of our recommended management strategies
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