Background
Maintaining normocapnia during mechanical ventilation in anesthetized children during laparoscopic surgeries is highly recommended. There is a debate regarding the use of capnography (ETCO2) as a trend monitor for evaluation of arterial carbon dioxide levels (PaCO2). We analyzed the relationship between ETCO2 and PaCO2 with time in elective pediatric laparoscopic surgeries.

Methods
This study was a prospective observational cohort analysis of 116 paired comparisons between PaCO2 and ETCO2 computed from 29 children (ASA I, 12–72 months). Arterial blood samples were withdrawn before, at 15 minutes and 30 minutes during pneumoperitoneum and 1 minute after deflation. ETCO2 value was recorded simultaneously, while arterial blood was withdrawn. PaCO2–ETCO2 relationship was evaluated by Pearson's correlation coefficients and Bland Altman Method of agreement.

Results
Out of the 116 comparisons analyzed, a PaCO2–ETCO2 difference beyond 0 to ≤ 5 mmHg was recorded in 71 comparisons (61.2%) with negative difference in 34 comparisons (29.3%). A positive significant correlation between PaCO2 and ETCO2 was recorded before (r = 0.617, p =  0.000) and at 15 minutes (r = 0.582, p =  0.001), with no significant correlation at 30 minutes (r = 0.142, p =  0.461), either after deflation (r = 0.108, p =  0.577). Bland-Altman plots showed agreement between ETCO2 and PaCO2 before inflation with mean PaCO2-ETCO2 difference 0.14 ± 5.6 mmHg (limits of 95% agreement -10.84–11.2, simple linear regression testing p-value 0.971), with no agreement at 15 minutes (0.51 ± 7.15, -13.5–14.5, p = 0.000), 30 minutes. (2.62 ± 7.83, -12.73–17.97, p = 0.000), or after deflation (1.81 ± 6.56, -10.93–14.55, p =  0.015).

Conclusion
Usage of capnography as a trend monitor in pediatric laparoscopic surgeries may not be a reliable surrogate for PaCO2 levels.