Vasopressin serum levels and disorders of sodium and water balance in patients with severe brain injury

Atrial natriuretic factor: is it responsible for hyponatremia and natriuresis in neurosurgery?

Objective

To evaluate the presence of hyponatremia and natriuresis and their association with atrial natriuretic factor in neurosurgery patients.

Methods

The study included 30 patients who had been submitted to intracranial tumor resection and cerebral aneurism clipping. Both plasma and urinary sodium and plasma atrial natriuretic factor were measured during the preoperative and postoperative time periods.

Results

Hyponatremia was present in 63.33% of the patients, particularly on the first postoperative day. Natriuresis was present in 93.33% of the patients, particularly on the second postoperative day. Plasma atrial natriuretic factor was increased in 92.60% of the patients in at least one of the postoperative days; however, there was no statistically significant association between the atrial natriuretic factor and plasma sodium and between the atrial natriuretic factor and urinary sodium.

Conclusion

Hyponatremia and natriuresis were present in most patients after neurosurgery; however, the atrial natriuretic factor cannot be considered to be directly responsible for these alterations in neurosurgery patients. Other natriuretic factors are likely to be involved.

Arginine-vasopressin V1a receptor inhibition improves neurologic outcomes following an intracerebral hemorrhagic brain injury

Cerebral edema is a devastating consequence of brain injury leading to cerebral blood flow compromise and worsening parenchyma damage. In the present study, we investigated the effects of arginine-vasopressin (AVP) V(1a) receptor inhibition following an intracerebral hemorrhagic (ICH) brain injury in mice and closely assessed the role it played in cerebral edema formation, neurobehavioral functioning, and blood-brain-barrier (BBB) disruption. To support our investigation, SR49059, an AVP V(1a) receptor competitive antagonist, and NC1900, an arginine-vasopressin analogue, were used. Male CD1 mice (n=205) were randomly assigned to the following groups: naïve, sham, ICH, ICH with SR49059 at 0.5 mg/kg, ICH with SR49059 at 2mg/kg, ICH with NC1900 at 1 ng/kg, ICH with NC1900 at 10 ng/kg, and ICH with a combination of SR49059 at 2 mg/kg and NC1900 at 10 ng/kg. ICH was induced by using the collagenase injection model and treatment was given 1h after surgery. Post assessment was conducted at 6, 12, 24, and 72 h after surgery and included brain water content, neurobehavioral testing, Evans Blue assay, western blotting, and hemoglobin assay. The study found that inhibition of the AVP V(1a) receptor significantly reduced cerebral edema at 24 and 72 h post-ICH injury and improved neurobehavioral function while reducing BBB disruption at 72 h. Western blot analysis demonstrated increased protein expression of aquaporin 4 (AQP4) in vehicle, which was reduced with AVP V(1a) receptor inhibition. Our study suggests that blockage of the AVP V(1a) receptor, is a promising treatment target for improving ICH-induced brain injury. Further studies will be needed to confirm this relationship and determine future clinical direction.