RPM 125-1 Miolo.indd

O R IG IN A L A R T IC L E INTRODUCTION Adequate postoperative analgesia is considered to be a major key for reducing pul monary morbidity and improving the outcome. Thoracic epidural anesthesia (TEA) has been proposed as a reliable analgesic method following thoracic surgery. Most of these benefi ts, however, relate to the postoperative or to the so-called perioperative period. Some case reports have suggested that sympathetic block secon dary to thoracic or spinal anesthesia might cause impaired intraoperative ventilation by increasing airway resistance and bronchial reactivity. A similar controversy surrounds some aspects of respiratory mechanics in anesthetized humans. Although previous studies have demonstrated that systemic local anesthetic secondary to TEA does not alter airway resistance in humans, and even attenuates bronchial hyperreactivity, the effects of thoracic sympathetic block on respiratory mechanics, particularly on its compliance, have been poorly explained. Pressure-volume curves are a feasible method for studying respiratory system mechanics, and the use of a low-fl ow infl ation technique has been established as a reliable and quick method for obtaining these curves. The remaining doubts are whether the advantageous postoperative effects of TEA begin intraoperatively, and whether these benefi ts outweigh the undesirable intraoperative effects of thoracic sympathetic block. OBJECTIVE To evaluate the effects of intraoperative thoracic sympathetic block on the elastic, viscoelastic and resistive properties of the respiratory system and its components (chest wall and pulmonary parenchyma), through analysis of pressure-volume curves obtained under quasi-static conditions. METHODS