Hyperosmolar Therapy in Elderly Neurosurgical Patients: Comparison of the Effect of Mannitol (20%) and Hypertonic Saline (3%) on Advanced Cardiovascular Parameters using Transesophageal Echocardiography - A Preliminary Randomized Controlled Trial.

Osmotherapeutic agents increase the intravascular volume by withdrawing water from the brain followed by relative hypovolemia due to diuresis leading to significant changes in systemic hemodynamics which might have adverse consequences in the elderly. We studied the effect of mannitol (20%) and hypertonic saline (3%) on left ventricle outflow tract velocity-time integral (LVOT-VTI) and cardiac output in elderly patients undergoing supratentorial neurosurgical procedures using transesophageal echocardiography. We recruited twenty-eight patients aged above 65 years undergoing supratentorial craniotomy who received equiosmolar solutions of 5.35 ml/kg of 3% hypertonic saline (Group HS, n=14) or 5 ml/kg of 20% mannitol (Group M, n=14). LVOT-VTI was recorded at baseline, 15, 30, 45, 60 and 90 minutes post-infusion and cardiac output (CO) was derived. We also recorded heart rate, blood pressure, fluid balance, brain relaxation, vasopressor use, complications and neurological outcome. We found a significant decrease in LVOT-VTI at 45, and 60 mins in Group M as compared to Group HS [mean(SD), 16.76(1.81) v/s 20.78(1.87), P <0.001, 17.4(2.38) v/s 19.16(2), P = 0.044, respectively]. We also found a corresponding significant fall in CO [3863.16(845.87) v/s 4745.59 (1209.33) ml/min, P = 0.034] and systolic blood pressure (P = 0.039), at 45 mins in Group M. Urine output was higher in Group M (P <0.001). All other parameters were comparable. Hypertonic saline appears to be associated with better systemic hemodynamics (LVOT-VTI, CO) while providing equivalent brain relaxation as mannitol in elderly patients. A future larger study is required to confirm our preliminary findings.