• F C Liu, C M Tsao, and P W Lui.
• Armed Forces Taoyuan General Hospital, Taoyuan, Taiwan.
• Acta Anaesthesiol. Sin. 2001 Jun 1; 39 (2): 71-6.

BackgroundThe volume of a bulky venous air emboli (VAE) can be estimated based on the calibration curve generated by injections of minute amount of air into the right atrium (RA) of dogs. We speculated that in patients similar VAE calibration curves could be generated using CO2 injections. As part of pre-clinical evaluation of the usefulness of CO2 injection, the present study was designed to determine whether injection of CO2 into the RA would cause less hemodynamic changes in dogs as compared with that of air or O2.MethodsTwenty-one anesthetized mongrel dogs were divided into 3 groups, i.e., groups air, CO2 and O2 (n = 7 each). Animals were injected a bolus of gas (air, CO2 or O2) in increasing volumes (from 0.25 to 4.0 mL/kg) into the RA via a central venous catheter at 10-min intervals. We measured the maximal changes in mean arterial pressure (MAP), pulmonary arterial pressure (PAP), central venous pressure (CVP), end-tidal CO2 (ETCO2), heart rate (HR), and mixed venous O2 saturation (SvO2).ResultsAfter venous injections, dogs receiving O2 or air showed greater decreases in MAP and ETCO2 as compared with those receiving CO2 (volume > 2.5 mL/kg; P < 0.05). The increases in PAP and CVP bore direct relation to O2 and air volume. In the CO2 group, the maximal changes in PAP and CVP were subtle as compared with the baseline (P < 0.05). There were no significant differences in HR and SvO2 among three groups.ConclusionsInjections of CO2 in increasing volumes into the RA of dogs caused less hemodynamic changes in comparison with that of air and O2.

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