Nuclear magnetic resonance as a measure of cerebral metabolism: effects of hypertonic saline resuscitation.

ABSTRACT

UNLABELLED Fears of central nervous system dysfunction from acute hypernatremia and hyperosmolarity with hypertonic saline resuscitation are often cited. We used high-energy phosphate nuclear magnetic resonance to investigate resuscitation effects on cerebral metabolism. Rats were instrumented for hemodynamic monitoring and fluid infusion and a phosphorus surface coil placed on their skulls. After shimming, baseline spectra were obtained. Animals were then bled for one hour to a mean arterial pressure (MAP) of 45 mm Hg, followed by resuscitation for one hour to a MAP of 75 mm Hg with lactated Ringer's (LR, n = 17) or 7.5% hypertonic saline (HS, n = 25). Spectra were obtained again and analyzed for the ratio of high-energy phosphocreatine (PCr) to low-energy inorganic phosphate (Pi). Intracellular hydrogen ion concentration [H+] was calculated from the PCr/Pi shift. [table see text] CONCLUSIONS: (1) Hypertonic saline results in a decreased intracellular pH compared with LR without associated changes in high-energy phosphate metabolism. (2) Decreases in pH may be the result of cell dehydration rather than metabolic dysfunction.