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 (CO(2)) is of utmost importance in neurosurgical patients. It is measured by partial pressure of arterial CO(2) (PaCO(2)) and end-tidal CO(2) (ETCO(2)). We aimed to study the correlation between PaCO(2) and ETCO(2) in 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 ETCO(2) and PaCO(2) at baseline, hourly intraoperatively and every 6 hourly in the PACU were studied. Data analysis was done using SPSS software version 20. RESULTS: The mean PaCO(2)–ETCO(2) gradient 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 PaCO(2) and ETCO(2) intraoperatively 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: ETCO(2) correlates PaCO(2) with acceptable accuracy in neurosurgical patients in the intraoperative and postoperative period on mechanical ventilation in Intensive Care Unit. Thus, continuous and noninvasive ETCO(2) can be used as a reliable guide to estimate arterial PCO(2) during neurosurgical procedures and in PACU.