Comparison of the effects of 7.2% hypertonic saline and 20% mannitol on electrolyte and acid-base variables in dogs with suspected intracranial hypertension

Abstract

Background: Hyperosmolar agents frequently are used to decrease intracranial pressure but their effects on electrolyte and acid-base variables have not been prospectively investigated. Objectives: Compare duration and magnitude of changes in electrolyte and acid-base variables after hyperosmolar treatment. Animals: Twenty-eight client-owned dogs with intracranial hypertension caused by various pathologies. Methods: Prospective, randomized, nonblinded, experimental cohort study. Fifteen dogs received a single dose (4 mL/kg) of 7.2% hypertonic saline (HTS), 13 dogs received 20% mannitol (MAN) 1 g/kg IV. Electrolyte and acid-base variables were measured before (T0), and 5 (T5), 60 (T60), and 120 (T120) minutes after administration. Variables were compared between treatments and among time points within treatment groups. Results: Mean plasma sodium and chloride concentrations were higher after HTS than MAN at T5 (158 vs 141 mEq/L; 126 vs 109 mEq/L) and significant differences were maintained at all time points. After HTS, plasma sodium and chloride concentrations remained increased from T0 at all time points. After MAN, plasma sodium and chloride concentrations decreased at T5, but these changes were not maintained at T60 and T120. Plasma potassium concentration was lower at T5 after HTS compared with T0 (3.6 vs 3.9 mEq/L) and compared to MAN (3.6 vs 4.1 mEq/L). At T60 and T120, plasma ionized calcium concentration was lower after HTS than MAN (1.2 vs 1.3 mmol/L). No significant differences were found in acid-base variables between treatments. Conclusions and Clinical Importance: At the administered dose, dogs receiving HTS showed sustained increases in plasma sodium and chloride concentrations, whereas dogs receiving MAN showed transient decreases. Future studies should assess the effects of multiple doses of hyperosmolar agents on electrolyte and acid-base variables.