Arthroscopic shoulder surgery under general anesthesia with brachial plexus block: postoperative respiratory dysfunction of combined obstructive and restrictive pathology.

ABSTRACT

OBJECTIVE: Changes in respiratory parameters and pulmonary function tests were evaluated after shoulder arthroscopic surgery with brachial plexus block (BPB). The purpose of this study was to identify the mechanism of respiratory dysfunction after this type of surgery. METHODS: Patients undergoing arthroscopic rotator cuff repair under general anesthesia (GA) with BPB were enrolled in the arthroscopy group (n = 30) while those undergoing open reduction of a clavicle or humerus fracture under GA were enrolled in the control group (n = 30). Forced vital capacity (FVC) and forced expiratory volume 1 s (FEV(1)) were measured at the outpatient clinic stage (#1) before (#2) and 20 min after BPB (#3) and 1 h after extubation (#4). Respiratory variable measurements along with the cuff leak test were performed 5 min after surgical positioning (T1) and at the start of skin closure (T2). Respiratory discomfort was evaluated after extubation. The upper airway diameters and soft tissue depth of chest wall were also measured by ultrasonography at stages #3 and #4. RESULTS: Static compliance decreased significantly at T2 in the arthroscopy group (50 ± 11 at T1 vs. 44 ± 9 ml/cm H(2)O at T2, p =0.035) but not in the control group. The incidence of positive cuff leak tests at T2 was significantly higher in the arthroscopy group than in the control group (47% in the arthroscopy group vs. 17% in controls, p =0.010). While FEV(1) and FVC remained stable at stages #1 and #2, FVC and FEV(1) decreased at stages #3 and #4 only in the arthroscopy group (FVC in arthroscopy group, #2 3.26 ± 0.77 l; #3 2.55 ± 0.63 l, p =0.015 vs. #2; #4 2.66 ± 0.41 l, p =0.040 vs. #2). The subglottic diameter decreased at #4 in the arthroscopy group, while no changes occurred in the control group (0.70 ± 0.21 cm vs. 0.85 ± 0.23 cm in the arthroscopy and control groups, respectively, p =0.011). Depth of skin to pleura increased at both intercostal spaces 1-2 and 3-4 in the arthroscopy group. There were three cases of hypoxia (S(p)O(2) < 95%) with room air in the arthroscopy group while none occurred in the controls. CONCLUSION: Shoulder arthroscopic surgery under GA with BPB induced both restrictive and obstructive pathologies. It is important to maintain a high level of awareness for the potential negative respiratory effects of this surgery especially for subjects with pre-existing cardiopulmonary disease. The measurements in this study would be useful to monitor the risk of respiratory dysfunction in these patients.