The Effect of Compression Stockings on Cerebral Desaturation Events in Obese Patients Undergoing Shoulder Arthroscopy in the Beach Chair Position

There have been numerous studies recently in the orthopaedic surgery and anesthesia literature related to both complications associated with arthroscopy in the BCP and ongoing efforts to improve patient safety. Advantages of this position when compared with the lateral decubitus position include easier anatomic orientation, lack of traction on the brachial plexus, ease of exam under anesthesia, and easier conversion to an open approach if needed. While extremely uncommon, complications such as ischemic brain and spinal cord injury as well as visual loss and ophthalmoplegia have been reported. A recent study reported that obesity increases the likelihood of having a CDE by as many as 12 times. CDEs were defined as intra-operative decreases in regional cerebral tissue oxygen saturation (rSO2) of 20% or greater from baseline as measured by near-infrared spectroscopy (NIRS). Since obesity is so common, it was decided to investigate a measure to potentially help decrease CDEs in this population.

The exact etiology of CDEs has not been definitively demonstrated and it is felt to be multifactorial. The sympathetic nervous system normally increases systemic vascular resistance and heart rate to maintain mean arterial blood pressure (MAP) when a person sits up or stands upright. This response is blunted by the vasodilatory effects of intravenous and inhaled anesthetics used in patients undergoing shoulder arthroscopy in the BCP. The result is decreased MAP and cerebral perfusion pressure that can contribute to hypoxic brain injury. The use of sequential compression devices placed on the legs of patients undergoing shoulder arthroscopy in the BCP has been shown to reduce the incidence of hypotension by increasing cardiac preload. This study excluded obese patients (BMI > 30) and did not directly monitor rSO2, but rather only monitored hemodynamic variables.

Compression stockings are often used in patients with venous insufficiency to help with pain and to control edema. The stockings compress the soft tissues and veins, and in conjunction with sequential compression devices (SCDs), may help to increase preload in an anesthetized patient in the BCP. To our knowledge, the effect of compression stockings on cerebral perfusion has not been studied. This study aims to determine if the use of compression stockings in obese patients undergoing shoulder arthroscopy in the BCP can decrease the incidence, frequency or magnitude of CDEs as measured by NIRS. We hypothesize that the use of compression stockings will result in decreased incidence and frequency of CDEs in our population.