Hyperosmolar Saline Irrigation Fluid in Arthroscopic Knee Surgery

An isotonic solution, such as saline (0.9%, 300mOsm/L) or lactated ringer's (273 mOsm/L), is commonly used and safely proven for joint irrigation during arthroscopy. Arthroscopic fluid is usually pressurized to enable visualization through dilation of the joint or bursa and prevent bleeding from the microvasculature. It has been recommended that this pressure be maintained at 49mmHg or less below the systolic blood pressure to preserve the clarity of view. The combination of large amounts of pressurized irrigation solution and lengthy arthroscopic procedures may cause substantial tissue fluid retention. Thus, extravasation of irrigation fluid into the periarticular tissues is inevitable and may create technical difficulties as well as patient morbidity and complications. Previous investigators have reported complications including tracheal obstruction, post-operative airway edema and compromise leading to prolonged intubation, excess weight gain, neurologic injuries, skin necrosis, and fluid overload associated with excessive fluid extravasation and tissue retention. Furthermore, it has been shown that fluid accumulated during the operation is slowly released back into the systemic circulation. Although there is not a rapid change in circulating volume, there may be implications for elderly patients and those with multiple comorbidities during prolonged arthroscopic surgery. Therefore the investigators seek to determine if a hyperosmolar solution, similar to what is used in head trauma patients, can reduce the degree of fluid extravasation in knee arthroscopy. The investigators also seek to determine if a hyperosmolar solution has any effect on post-operative knee pain compared to the standard isotonic solution. The third objective is to determine if a hyperosmolar solution has any effect on post-operative pain medicine consumption compared to the standard isotonic solution.