A comparison of mannitol versus 3% hypertonic saline for brain relaxation during elective supratentorial craniotomy: Neurosurgical anesthesia

Introduction: Brain relaxation is essential in anesthesia for intracranial surgery; it has been considered a neuroprotective measure as it can reduce surgical compression, local hypoperfusion, cerebral ischemia, and blood loss. To ease surgical tumor removal, measures are taken to reduce brain swelling, often referred to as brain relaxation. In the present study, we aimed to compare the effects of 20% mannitol and 3% hypertonic saline (HS) on brain relaxation during supratentorial craniotomy. Fluid input, urine output, arterial blood gases and serum sodium concentration were also measured. Methods: We conducted a prospective, randomized, double blind controlled trial. Sixty patients, ages 18 to 50, belonging to American Society of Anesthesiologist (ASA) physical status (II-IV), posted for craniotomy were divided into two equal groups in a double-blinded selection by using computer-generated random numbers (Thirty patients in each group). The surgeon and anesthesiologist were unaware of the identity of the study agents. Each patient was administered 150 ml of either 20% mannitol (Group M) or 3% HTS over 20 minutes (min) (Group H) after skin incision. The neurosurgeon assessed the brain conditions on a four-point scale as "Perfectly relaxed," "Satisfactory relaxed," "Firm brain," or "Bulging brain," immediately after opening the dura mater. Results: Intraoperative brain relaxation was comparable between the two groups. Brain relaxation observed in Group M (perfectly relaxed/satisfactory relaxed/firm brain/bulging brain, n = 8/13/5/4) was similar to that observed in Group H (perfectly relaxed/satisfactory relaxed/firm brain/bulging brain, n = 7/13/8/2; P= 0.77). Urine output was significantly higher in the mannitol group (P <0.05). Administration of HTS was associated with a transient increase in serum sodium concentrations, which was statistically significant but returned to normal within 48 h (P < 0.05). There were no significant differences in fluid input and arterial blood pressure during surgery in between two groups. Conclusion: Our results suggested that hypertonic saline and mannitol both had a similar effect on brain relaxation during elective supratentorial craniotomy.