Effect of Intravenously Administered Tranexamic Acid on Intraoperative Visual Clarity, Perioperative Blood Loss and Early Postoperative Outcomes in Shoulder Arthroscopy Performed in the Beach Chair Position: A Randomized Controlled Trial

All surgical procedures will be performed at the University orthopaedic and trauma hospital Lovran, Croatia. Upon arrival at the hospital, the patient's body weight and height will be recorded. One day before the procedure, the patient will have blood taken from a vein and a complete blood count will be analyzed. Body weight and height were also recorded, and body mass index was calculated. Before the procedure, a physiotherapist measured the initial shoulder circumference in centimeters at three standardized measurement points: axilla-acromion (point A), axilla-deltoid (point B), and 10 cm above the olecranon (point C). The circumferences were documented on a standardized data collection form. Immediately before the procedure, patients will receive regional infiltrative (interscalene block) and general anesthesia with airway protection by endotracheal tube or laryngeal mask. Patients in the experimental group will receive 1 g of TXA in 100 ml of sterile saline IV 10 min before the start of the procedure, while patients in the control group will receive only sterile saline. The position of the patients will be beach chair with the head in the protective helmet and the arm in the front traction of 2,5 kg. All patients will be operated on by the same surgeon (NM) with the usual equipment: 4 mm 30° arthroscopic lens, arthroscopic pump basically set to 50 mmHg with the possibility of pulse increase of pressure by 20 mmHg for 2 min as needed, radiofrequency ablator and arthroscopic shaver system. Rotator cuff tendon repair will be performed using suture anchors as the primary procedure in all patients. If needed, additional procedures will be carried out, including glenohumeral (GH) stabilization by capsulolabral plication, labral repair, and long head of the biceps brachii (LHBB) tenodesis using the same implants. In cases of more severe damage or inflammation, LHBB tenotomy will be performed instead. Acromioclavicular (AC) joint repositioning and vertical stabilization will be performed using a suspensory fixation system with titanium buttons and synthetic tapes.

Other possible procedures include subacromial and subcoracoid bursectomy with soft tissue release, acromioplasty, tuberoplasty, AC joint resection, capsulotomy, synovectomy, microfracture (MFX), paralabral cyst evacuation, tendon drilling, removal of calcifications or implants, and tissue or implant sampling for histological and microbiological analysis. At the beginning of surgery and every 15 minutes thereafter, the surgeon will assess arthroscopic visibility using a Visual Analogue Scale (VAS-V) ranging from 0 (worst) to 10 (best), while being blinded to TXA allocation. Simultaneously, the endoscopic screen will be photographed with a 40 MP camera. Scores will be recorded, and images stored. Screen photos will be presented after surgery to three independent surgeons with experience in arthroscopy on visual clarity estimation (VAS range 0-10). Intraoperative data will include the number and extent of tendon lesions, presence of synovitis, operative time, mean arterial pressure (MAP), number of irrigation pressure boosts, and fluid inflow/outflow volumes. All procedures and implants will be documented. Any intraoperative complications (e.g., camera fogging, implant/instrument failure) will be noted. All administered crystalloids/colloids will be listed. Irrigation waste fluid will be collected and homogenized, and a 20 mL sample will be taken for analysis. Hemoglobin concentration will then be determined in the homogenized sample using spectrophotometry (Cripps method; University of Rijeka, Medical Faculty; Varian Cary 100 Bio, 190-900 nm, resolution ≤ 0.189 nm, wavelength accuracy ± 0.02-0.04 nm). On the first day after the surgery, the shoulder circumference will be measured at 3 typical sites and the level of pain will be noted (VAS range 0 no pain -10 the strongest pain). On the second day, the shoulder circumference measurement and estimation of the level of pain will be repeated. Also blood will be taken from a vein and complete blood count will be repeated. During the postoperative period, the amount and type of analgesic drugs administered and the length of hospitalization will be monitored.