Brain relaxation and electrolyte balance during resection of posterior fossa tumors under sitting position: Mannitol versus placebo

Background
Mannitol can be negative for outcome, which may explain why we lack scientific support for its use. The purpose of this study was to compare the brain relaxation and electrolyte balance in group of patients with posterior fossa tumor underwent surgery in sitting position with or without mannitol.
Methods
Eighty patients scheduled for resection of posterior fossa tumor from April 2009 till April 2012 were enrolled in this prospective, double-blind, randomized study. All cases received general anesthesia and attained sitting position during surgery. Patients were enrolled into two groups, group I received mannitol (20%) 1 gm/kg just before opening the dura. Group II received placebo at the same time. Hemodynamics, duration of surgery, Brain Relaxation Score (BRS) in which surgeons assessed the condition of the brain as 1 = perfectly relaxed, 2 = satisfactorily relaxed, 3 = firm (leveled) brain, 4 = bulging brain were recorded. Blood losses, urine output and serum sodium and potassium levels were assessed. Any operative complications were recorded.
Results
No difference in hemodynamics (HR and MBP) whereas CVP with mannitol was higher than with placebo ( < 0.01). No difference in brain relaxation score ( = 0.719) or operative complication between both groups. Mannitol was associated with higher urine output ( < 0.001), higher serum potassium and osmolarity ( < 0.001) and lower serum sodium ( < 0.001) than compared with placebo.
Conclusion
Surgery for posterior fossa in sitting position could be safely performed without the use of mannitol avoiding its adverse side effects with beneficial effects in terms of preserving hemodynamic, electrolytes balance, reasonable brain relaxation and fewer complications.