Effect of intraoperative mannitol on optic nerve sheath diameter in patients undergoing total laparoscopic hysterectomy : A double blind randomised study

Total laparoscopic hysterectomy is a popular and rapidly growing surgical alternative technique in gynaecological surgeries as they offer significant advantages i.e. minimal invasion, reduced bleeding, reduced postoperative pain which translate into shorter hospital stay. These approaches present unique challenges to the anaesthesiologists in terms of Trendelenburg position along with pneumoperitoneum. These procedures result in increase in intracranial pressure (ICP) due to Trendelenburg positioning and pneumoperitoneum. A raised intra cranial pressure (ICP) can result in decreased cerebral perfusion pressure (CPP), which in turn can cause cerebral ischemia and delayed recovery.

A simple, non-invasive and reproducible bedside technique for assessment of intracranial pressure (ICP) is sonographically measured optic nerve sheath diameter (ONSD). Increase in optic nerve sheath diameter (ONSD) is surrogate for increase in intracranial pressure (ICP). Mannitol, a hyperosmolar agent, is widely used in anaesthesia practice as a diuretic. Mannitol exerts its diuretic effect by decreasing the reabsorption of water and sodium across the renal tubules. Mannitol has been used to counter the increase in intracranial pressure in a variety of clinical situations. It is also being used in laparoscopic surgeries in Trendelenburg position. However no formal study has been done on this. Therefore, further research is needed to substantiate its use in this clinical situation.

  We will enroll a minimum of 42 patients who will be scheduled to undergo total laparoscopic hysterectomy in Trendelenburg position. These patients will be divided in two groups (study and placebo group) and a randomized study will be conducted to study the effect of intraoperative mannitol on optic nerve sheath diameter in patients undergoing total laparoscopic hysterectomy. The primary objective of the study is to measure the effect of

intraoperative mannitol on optic nerve sheath diameter in patients undergoing total laparoscopic hysterectomy between the two study groups. The secondary objectives is to study the cognitive dysfunction between the two study groups. All the patients undergoing total laparoscopic hysterectomy will be screened, and those found eligible will be enrolled. Enrolled patients will be divides in two groups. Group M will receive IV infusion of 20% mannitol (0.5g/kg i.e. 2.5ml/kg) given over a duration of 30 minutes and group N will receive placebo (normal saline) by the same route. The primary objective of the study is to measure the intraoperative effect of mannitol on optic nerve sheath diameter in patients undergoing total laparoscopic hysterectomy between the two study groups. We hypothesize that the use of mannitol will prevent the increase of intracranial pressure during total laparoscopic hysterectomy.