Shoulder arthroscopy is one of the most commonly performed orthopaedic procedures and it is often done with the patient in the upright, or beach chair position (BCP). There have been multiple reported complications associated with the BCP, including cerebral ischemia, loss of vision, ophthalmoplegia, stroke, and even death. It has been reported that patients with a body mass index (BMI) of 34 or greater are as much as 12 times more likely to experience cerebral desaturation events (CDEs) compared to non-obese controls. CDEs in the upright position are hypothesized to be partially related to reduced cardiac preload due to venous pooling in the lower extremities which is exaggerated in obese patients. This prospective observational study aims to determine if the use of compression stockings in obese patients undergoing shoulder arthroscopy in the BCP can reduce the incidence, frequency, or magnitude of CDEs experienced by the patient

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.

Inclusion Criteria:

• Age 18 years or older
• BMI greater than or equal to 30 kg/m^2
• Capable of receiving an interscalene nerve block.

Exclusion Criteria:

• Age < 18
• History of carotid artery stenosis equal to or greater than 90%
• History of stroke
• History of transient ischemic attack
• History of syncope
• History of vision loss

There is no plan to make individual participant data available to other researchers

The baseline analysis population comprises the 23 prospective cases who met inclusion criteria and were not excluded by the principal investigator as well as 24 historical control participants.

Adverse event data were collected from December 2013 through May 2014 (6 months)

In the historical control group, there are no participants at-risk for adverse events or all-cause mortality because they were a retrospective sample that did not receive compression stockings.

There are no limitations or caveats to report