Intramuscular pressure and fluid absorption during arthroscopic acromioplasty

During arthroscopic acromioplasty a high level of irrigation fluid pressure is sometimes required to obtain an adequate visual field. To evaluate the influence of bursa pressure level on the blood circulation of the shoulder muscles, we measured the intramuscular pressure (IMP) in the supraspinatus and deltoid muscles with the microcapillary infusion technique during surgery. Eleven patients with impingement syndromes Neer I-III and rotator cuff tendinitis were examined at subacromial bursa pressures of 100 or 150 mm Hg. In another 11 patients the amount of irrigation fluid absorbed into the circulatory system was evaluated with the use of 2% ethanol NaCl irrigation fluid. At bursal pressures of 100 or 150 mm Hg, the absorbed volume was calculated from the expiratory breath ethanol concentration at the termination of surgery. The IMP in both the supraspinatus and the deltoid muscle varied considerably regardless of bursal pressure. In 50% of the recordings a considerable increase was seen in IMP pressure (> 15 mm Hg) when the arthroscope was redirected from the intra-articular position to the subacromial bursa. The mean IMP in both muscles was less than 60 mm Hg during the major portion of the bursoscopy regardless of the infusion pressure level. The fluid absorption was 100 mL (0 to 229 mL) in the 100 mm Hg group and 37 mL (0 to 180 mL) in the 150 mm Hg group. All values were well below the 1000 mL absorption limit regarding the risk of development of a hyperhydration syndrome. In arthroscopic acromioplasty a bursal pressure of 100 or 150 mm Hg will result in similar IMP levels, in most cases below the threshold for muscle blood circulation. The amount of fluid absorbed to the circulatory system will be harmless.