[[Lactated Ringer's]] solution (LR), a commonly used [[crystalloid]], is hypotonic at 273 mOsm/L. Low plasma [[osmolarity]] can cause [[cerebral edema]]. Therefore, hypotonic solutions, such as LR, are avoided, while [[normal saline]] (NS) has traditionally been used as the main fluid in patients with neurosurgery 
((Tommasino C, Picozzi V. Volume and electrolyte management. Best Pract Res Clin Anaesthesiol 2007; 21: 497-516.)).