Absorption of carbon dioxide during laparoscopy in children measured using a novel mass spectrometric technique

Background. Carbon dioxide (CO₂) is absorbed during pneumoperitoneum and may cause adverse haemodynamic effects. The aim of this study was to measure the elimination of exogenous CO₂ during laparoscopy in children. Methods. Ten children [27.6 (56.5) months; mean (sd)] undergoing laparoscopic and nine [24.5 (17.3) months] undergoing open surgery were studied. Breath samples were collected at the line for end-tidal CO₂ and analysed for ¹³CO₂/ ¹²CO₂ ratio expressed as δPDB (difference from standard), by isotope-ratio mass spectrometry. The proportion of absorbed CO₂ was calculated comparing exhaled ¹³CO₂/¹²CO₂ before and during CO₂ pneumoperitoneum. Results. ¹³CO₂/¹²CO₂ in medical CO₂ was -32.7 (2.1) δPDB. ¹³ CO₂/¹²CO₂ in breath of patients undergoing open procedures was -24.3 (2.4) δPDB at the start of operation and did not change during the operation (P>0.2). ¹³CO₂/¹²CO₂ in breath of patients undergoing laparoscopy was -21.5 (5.4) δPDB at the start of insufflation, and decreased during pneumoperitoneum by 2.5 (1.6) δPDB, indicating absorption of exogenous CO₂. The percentage of expired CO₂ absorbed rose to 15.5 (7.7)% after 30 min of pneumoperitoneum and decreased rapidly after desufflation. Conclusion. After 10 min of laparoscopy 10-20% of expired CO₂ derives from the exogenous CO₂. CO₂ absorption can be measured using a simple mass spectrometric technique.