Blood gas changes in patients undergoing laryngeal microsurgery

Background The aim of this prospective, single-blind study was to assess the variations in the blood levels of PaO2, PaO2/FiO2, PaCO2, and acid–base balance of patients undergoing laryngeal microsurgery under general anesthesia using small-bore endotracheal tubes. Methods 25 male patients were intubated with endotracheal tubes of 5.5-mm-inner diameter and fifteen female patients were intubated with endotracheal tubes of 5-mm-inner diameter during surgery. PaO2/FiO2, PaO2, PaCO2, percentage saturation of O2 and HCO3, and pH levels were monitored before surgery and at 15-min intervals during laryngeal microsurgery. Respiratory functionʹs values (dead space, peak inspiratory pressure (PIP) and dynamic compliance) were recorded every 15 min throughout laryngeal microsurgery. Results No significant differences were observed between the pre- and intra-operative values of percentage saturation of O2, PaO2/FiO2 and HCO3 until 120th min. There was no significant difference in respiratory functionʹs values intraoperatively. Under anesthesia, PaO2 levels significantly increased when compared with preoperative values. Another significant increase was observed in PaCO2 levels after the 60th min. However, compared with preoperative values, pH levels significantly decreased under anesthesia at the 105th and 120th min. Conclusion Laryngeal microsurgery under general anesthesia can be performed using small-bore endotracheal tubes. This is not likely to have any adverse effects on a patientʹs blood gases and acid–base balance unless the operation lasts longer than 105 min.