A study of partial pressure of arterial carbon dioxide and end-tidal carbon dioxide correlation in intraoperative and postoperative period in neurosurgical patients

Background and Aim: Monitoring carbon dioxide (CO2) is of utmost importance in neurosurgical patients. It is measured by partial pressure of arterial CO2 (PaCO2) and end-tidal CO2 (ETCO2). We aimed to study the correlation between PaCO2and ETCO2in neurosurgical patients in the intraoperative and postoperative period on mechanical ventilation in Postanesthesia Care Unit (PACU). Methodology: This was prospective observational study done at tertiary care teaching public hospital over a period of 1 year. We studied 30 patients undergoing elective craniotomy intraoperatively and in the postoperative period on mechanical ventilation for 24 h. Serial measurement of ETCO2and PaCO2at baseline, hourly intraoperatively and every 6 hourly in the PACU were studied. Data analysis was done using SPSS software version 20. Results: The mean PaCO2–ETCO2gradient intraoperatively over 4 h is 3.331 ± 2.856 and postoperatively over 24 h is 2.779 ± 2.932 and lies in 95% confidence interval. There was statistically significant correlation between PaCO2and ETCO2intraoperatively baseline, 1 h, 2 h, 3 h, and 4 h with Pearson's correlation coefficients of 0.799, 0.522, 0582, 0.439, and 0.547, respectively (P < 0.05). In PACU at baseline, 6 h, 12 h, 18 h, and 24 h Pearson's correlation coefficients were. 534, −0.032, 0.522, 0.242, 0.592, and 0.547, respectively, which are highly significant at three instances (P < 0.01). Conclusion: ETCO2correlates PaCO2with acceptable accuracy in neurosurgical patients in the intraoperative and postoperative period on mechanical ventilation in Intensive Care Unit. Thus, continuous and noninvasive ETCO2can be used as a reliable guide to estimate arterial PCO2during neurosurgical procedures and in PACU.