The effect of hypertonic saline solution on vasodilatation of superior sagittal sinus using magnetic resonance imaging in normovolenmic dogs

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Several animal studies have demonstrated the beneficial effects of hypertonic saline (HSS) on cerebral blood flow, intracranial pressure and brain water content. This study aimed to investigate, using magnetic resonance imaging, (1) whether a small volume of HSS is superior to dextran in vasodilatation of cerebral vessels and reduction of cerebrospinal fluids in dogs, and (2) whether a small volume of 7.2% hypertonic saline solution with 6% dextran 70 (HSD) is superior to mannitol in vasodilatation of encephalic vessels in the dogs.STUDY 1 : HSS induced significant expansion of the cross-section of superior sugittal sinus at the vertical section of pituitary and a decrease in cerebrospinal fluid area at the vertical section of epencephalic limbic more than dextran 40 did. However, the relative plasma volume in the dog received dextran 40 was significantly higher after t=30 min than the HSS group (p<0.001). Therefore, it is suggested that HSS might be superior to colloid solution in improving of cerebral circulation, whereas dextran 40 is superior to HSS in expanding systemic circulation in dogs.STUDY 2: The dogs were assigned to receive 5 mL/kg of isotonic saline solution (ISS) as control, 20% mannitol or HSD infusion at a flow rate of 20 mL/kg/hours via right cephalic vein. Venous blood samples were collected immediately before fluid infusion (pre) and every 15 minutes until 120 minutes after the initiation of fluid infusion. Immediately after collection of each blood sample, T1 and T2-weighted magnetic resonance imaging recordings were undergone. Immediately after HSD infusion, the area of the cross-section of superior sagittal sinus was significantly greater than that of beagles in the other groups (p<0.001), reaching the 2.09±0.25 times pre-value. Therefore, it is suggested that 5 mL/kg of HSD might be superior to isovolume of mannitol in reducing CSF in the dog.