The relationship between subacromial space pressure, blood pressure, and visual clarity during arthroscopic subacromial decompression.

Twenty-two consecutive patients with subacromial impingement syndrome underwent arthroscopic subacromial decompression. Measurements of the subacromial space pressure and the blood pressure were recorded along with the clarity of the visual field. The clarity of the visual field was objectively determined based on the pressure at which bleeding was observed from trabecular bone or the soft tissue capillaries. A direct correlation was found between systolic blood pressure (SBP), subacromial space pressure (SASP), and the clarity of the visual field. On average, maintaining a pressure difference (SBP-SASP) of 49 mm Hg or less prevented bleeding and permitted good visualization. With a greater differential, significant bleeding occurred. Furthermore, the use of relative hypotensive anesthesia permits lower irrigation pressures and significantly reduces the risk of fluid extravasation into the subcutaneous tissues of the shoulder.