Carbon dioxide absorption is not linearly related to intraperitoneal carbon dioxide insufflation pressure in pigs.
BACKGROUND
Carbon dioxide absorption into the blood during laparoscopic surgery using intraperitoneal carbon dioxide insufflation may lead to respiratory acidosis, increased ventilation requirements, and possible serious cardiovascular compromise. The relationship between increased carbon dioxide excretion (VCO2) and intraperitoneal carbon dioxide insufflation pressure has not been well defined.


METHODS
In 12 anesthesized pigs instrumented for laparoscopic surgery, intraperitoneal carbon dioxide (n = 6) or helium (n = 6) insufflation pressure was increased in steps, and VCO2 (metabolic cart), dead space, and hemodynamics were measured during constant minute ventilation.


RESULTS
VCO2 increases rapidly as intraperitoneal insufflation pressure increases from 0 to 10 mmHg; but from 10 to 25 mmHg, VCO2 does not increase much further. PaCO2 increases continuously as intraperitoneal insufflation pressure increases from 0 to 25 mmHg. Hemodynamic parameters remained stable.


CONCLUSIONS
By considering Fick's law of diffusion, the initial increase in VCO2 is likely accounted for by increasing peritoneal surface area exposed during insufflation. The continued increase in PaCO2 without a corresponding increase in VCO2 is accounted for by increasing respiratory dead space.
Lister
D R
DR
Department of Anaesthesia, St. Paul's Hospital, University of British Columbia, Vancouver, Canada.
Rudston-Brown
B
B
Warriner
C B
CB
McEwen
J
J
Chan
M
M
Walley
K R
KR
D000042:Absorption; D000818:Animals; D001692:Biological Transport; D002245:Carbon Dioxide / Q000097:blood; D007327:Insufflation; D010535:Laparoscopy; D010100:Oxygen / Q000502:physiology; D010537:Peritoneum; D011312:Pressure; D013552:Swine
D002245:Carbon Dioxide; D010100:Oxygen