Carbon dioxide gas embolism in the experimental animal

Accidental vascular placement of Veress needle or cannula during laparoscopic insufflation with carbon dioxide gas (CO2) may cause a fatal gas embolism. Deliberate CO2 injection into the vena cava of dogs did not define a safe flow rate or pressure to prevent mortality. We studied incremental increase in pressure at the same maximum rate of gas flow (corresponding to 2.5 L/mm in a 70-kg man, the maximum flow rate possible with a Veress needle) to define the pressure at which pigs did not reversibly tolerate intravenous CO2 insufflation. The right iliac vein was cannulated and CO2 was insufflated at the maximum flow rate but at three pressures, 15, 20, and 25 mm Hg. During each cycle CO2 was insufflated until the elapse of 30 seconds or a change in end tidal CO2 by 50%. Five of the six animals tolerated intravenous CO2 at 15 mm Hg pressure. In one animal, during insufflation at 15 mm Hg the flow rate was accidentally set at twice the standard level, which resulted in immediate and fatal CO2 embolism. During insufflation at 20 mm Hg four pigs died, the last one during insufflation at 25 mm Hg. Transient insufflation of CO2 at low pressure (15 mm Hg) is well tolerated because pressure in the venous system may limit gas flow. However, a decrease in end tidal CO2 should alert the anesthesiologist to stop insufflation immediately. This will allow recovery. When insufflating pressures are in the middle (20 mm Hg) or high range (25 mm Hg), CO2 embolism can be fatal despite its early recognition.