Anaesthesia for laparoscopic nephrectomy: Does end-tidal carbon dioxide measurement correlate with arterial carbon dioxide measurement?

Background and Aims: Not many studies have explored the correlation between arterial carbon dioxide tension (PaCO2) and end-tidal carbon dioxide tension (ETCO2) in surgeries requiring pneumoperitoneum of more than 1 hour duration with the patient in non-supine position. The aim of our study was to evaluate the correlation of ETCO2 with PaCO2 in patients undergoing laparoscopic nephrectomy under general anaesthesia. Methods: A descriptive study was performed in thirty patients undergoing laparoscopic nephrectomy from September 2014 to August 2015. The haemodynamic parameters, minute ventilation, PaCO2 and ETCO2 measured at three predetermined points during the procedure were analysed. Correlation was checked using Pearson's Correlation Coefficient Test. P <0.05 was considered statistically significant. Results: Statistical analysis of the values showed a positive correlation between ETCO2 and PaCO2 (P < 0.05). Following carbon dioxide insufflation, both ETCO2 and PaCO2 increased by 5.4 and 6.63 mmHg, respectively, at the end of the 1st hour. The PaCO2-ETCO2 gradient was found to increase during the 1st hour following insufflation (4.07 ± 2.05 mmHg); it returned to the pre-insufflation values in another hour (2.93 ± 1.43 mmHg). Conclusion: Continuous ETCO2 monitoring is a reliable indicator of the trend in arterial CO2 fluctuations in the American Society of Anesthesiologists Grades 1 and 2 patients undergoing laparoscopic nephrectomy under general anaesthesia.