DOI: 10.1097/ANA.0b013e318163c3d4
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PMID: 18362788
Issn Print: 0898-4921
Publication Date: 2008/04/01
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Excerpt
The use of hypertonic saline to reduce raised intracranial pressure (ICP) after head injury has been well described.1 The infusion of sodium chloride solutions, including hypertonic saline can cause a hyperchloremic metabolic acidosis due to reduction in the strong ion difference.2 We report the use of 8.4% sodium bicarbonate as an alternative to hypertonic saline, to treat intracranial hypertension in a patient with hyperchloremic acidosis.
The patient was a 31-year-old man with traumatic brain injury. He had no surgically remediable intracranial injury and was admitted to the intensive care unit for ventilation and control of his intracranial hypertension. In the first 48 hours, he required seven 100-mL boluses of 5% saline to control his ICP. Blood gases at 60 hours showed a hyperchloremic acidosis with a pH of 7.30, pCO2 of 4.8 kPa, sodium of 153 mmol/L, and chloride of 132 mmol/L. In view of this, we elected to use a 100-mL bolus of 8.4% sodium bicarbonate to treat his rising ICP. Over the next hour, his ICP fell from 23 to 9-cm H2O. His pH rose to 7.35 with his sodium increasing to 157, but CO2 and chloride unchanged and ventilation not altered. Five percent sodium chloride has a sodium concentration of 855 mmol/L and an osmolality of 1710 mosmol/L. Sodium bicarbonate (8.4%) has a sodium concentration of 1000 mmol/L and an osmolality of 2000 mosmol/L. The osmotic effects of the sodium bicarbonate should be similar to those of 5% saline. Sodium bicarbonate has been shown to reduce brain water content in neonatal dogs,3 but its effects on intracranial hypertension in humans have not been investigated. The use of sodium bicarbonate can cause a transient increase in paCO2 (0.47 kPa after 2.3 mmol/kg of sodium bicarbonate in 1 study4). The cerebral vasodilatation this could theoretically induce can easily be offset by an increase in ventilation, but we did not experience this problem. We suggest that 8.4% sodium bicarbonate can be used as an alternative to 5% saline to treat raised intracranial pressure in patients with concurrent hyperchloremic acidosis.
