The Aim of This Study is to Examine the Effect of Intravenously Administered Tranexamic Acid (TXA) on the Visual Clarity, Perioperative Hemorrhage, Duration and Early Postoperative Course of Shoulder Arthroscopy in Beach Chair Position.

Shoulder arthroscopy provides many benefits with a permanent increase in the possibilities and complexity of the application. A condition to perform it is intraoperative visual clarity dependent on hemorrhage control. The aim of this prospective, double blind, randomized, and controlled study is to examine the effect of intravenously administered tranexamic acid (TXA) on the visual clarity, perioperative hemorrhage, duration and early postoperative course of shoulder arthroscopy in beach chair position, which is not yet available in the literature. In the tested and control group, the investigators measure hemoglobin (Hb) in the waste irrigation fluid and the patient's blood before and after the procedure, visual clarity, duration of the procedure, postoperative shoulder swelling, pain level and analgesic drug consumption. The research uses scientific methods to determine if there is a reasonable basis for introducing TXA into routine clinical use.

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. 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 tranexamic acid 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 2-3 kg. All patients will be operated on by the same surgeon (NM) with the usual equipment: 4.5 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. Tendon reconstructions and shoulder stabilization will be performed in the usual way with suture anchors. During the procedure, the visual clarity on the endoscope screen (Visual analog scale VAS range: 0 worst visual clarity - 10 best visual clarity) will be evaluated by the surgeon every 15 minutes and the screen will be photographed at the same time. Screen photos will be presented after surgery to three independent surgeons with experience in arthroscopy on visual clarity estimation (VAS range 0-10). During the procedure, the number of times the pump pressure is increased will be counted. At the end of the surgery, the mean arterial pressure (MAP) will be noted, the exact amount of irrigation fluid consumed and the duration of the procedure from the first incision to the last skin suture will be calculated. A homogenized sample will be taken from the total volume of the waste solution in which the Hb concentration will be determined by a spectrophotometer using the Cripps method (University of Rijeka, Medical Faculty; spectrophotometer Varian Cary 100 Bio 190-900 nm, resolution ≤ 0.189 nm, wavelength accuracy of ± 0.02 nm to ± 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.

Eligibility Criteria:
Inclusion Criteria:

* rotator cuff tear
* instability of the glenohumeral joint
* instability of the acromioclavicular joint

Exclusion Criteria:

* allergy to tranexamic acid
* deep vein thrombosis
* congenital thrombophilia
* coagulopathy
* thromboembolic events last 12 months
* stroke or acute coronary syndrome last 3 months
* renal failure
* cirrhosis of the liver
* glaucoma or retinal vascular disorder
* chronic treatment with anticoagulant therapy
* uncontrolled hypertension