Blood gas changes in patients undergoing laryngeal microsurgery

The aim of this prospective, single-blind study was to assess the variations in the blood levels of PaO(2), PaO(2)/FiO(2), PaCO(2), and acid-base balance of patients undergoing laryngeal microsurgery under general anesthesia using small-bore endotracheal tubes.

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. PaO(2)/FiO(2), PaO(2), PaCO(2), percentage saturation of O(2) and HCO(3), and pH levels were monitored before surgery and at 15-min intervals during laryngeal microsurgery. Respiratory function's values (dead space, peak inspiratory pressure (PIP) and dynamic compliance) were recorded every 15 min throughout laryngeal microsurgery.

No significant differences were observed between the pre- and intra-operative values of percentage saturation of O(2), PaO(2)/FiO(2) and HCO(3) until 120th min. There was no significant difference in respiratory function's values intraoperatively. Under anesthesia, PaO(2) levels significantly increased when compared with preoperative values. Another significant increase was observed in PaCO(2) levels after the 60th min. However, compared with preoperative values, pH levels significantly decreased under anesthesia at the 105th and 120th min.

Laryngeal microsurgery under general anesthesia can be performed using small-bore endotracheal tubes. This is not likely to have any adverse effects on a patient's blood gases and acid-base balance unless the operation lasts longer than 105 min.