Surgical tracheostomy in ventilated intensive care patients transiently impairs arterial oxygenation

Abstract

Objective: To evaluate the immediate effect of surgical tracheostomy on post-operative oxygenation in mechanically ventilated critically ill patients, and to compare safety aspects and time consumption when performed in either the intensive care unit (ICU) or the operating room. Design: Prospective, open randomised study. Setting: General intensive care unit in a secondary care (central) hospital. Subjects: Eighteen critically ill patients on mechanical ventilation were randomised to undergo elective surgical tracheostomy either at the bedside in the intensive care unit (ICU group) or in the operating room (OR group). Intervention: Surgical tracheostomy performed by experienced general surgeons. Measurements: Arterial blood gases and recordings of ventilator settings (including FiO2) were obtained at regular intervals during the study period. Operating time and total procedure time were recorded. The arterial to alveolar oxygen tension ratio, PaO2/FiO2 ratio and alveolar to arterial oxygen tension difference were calculated. Main results: Preoperative clinical characteristics were similar in the two study groups. The first post-operative assessment revealed a reduction in mean arterial oxygen tension [OR group: 12.3 to 9.4 kPa (p=0.008); ICU group: 12.0 to 10.1 kPa (p=0.17)], arterial to alveolar oxygen tension ratio [OR group: 0.34 to 0.27 (p=0.008); ICU group: 0.35 to 0.30 (p=0.21)] and in PaO2/FiO2 ratio [OR: 27.2 to 21.0 kPa (p=0.008); ICU group: 28.5 to 23.7 kPa (p=0.17)], as well as an increase in the alveolar to arterial oxygen tension difference [OR group: 26.4 to 28.3 kPa (p=0.008); ICU group: 22.3 to 25.3 kPa (p=0.09)]. Despite the similar trend, statistical significance at the 0.05 level was only achieved in the OR group. The impairment subsided within 8 hours. Post-operatively, there were no significant differences between the two groups regarding oxygenation variables. Operating time was similar for both groups whereas total procedure time was significantly higher in the OR group (94 minutes versus 42 minutes, p<0.001). No clinically significant complications were encountered in either group. Conclusion: Surgical tracheostomy causes a transient oxygenation impairment in critically ill patients on mechanical ventilation as measured by these oxygenation variables. When performed by an experienced surgeon, tracheostomy can be done safely at the bedside in the ICU.