Embolism risk analysis--helium versus carbon dioxide.

BACKGROUND: Helium is used as an insufflation gas to avoid the negative properties of carbon dioxide (CO(2)), such as CO(2) accumulation, acidosis, and tachycardia, particularly in the case of insufficient respiratory function, seen also in infancy. Any laparoscopic procedure carries the risk of a gas embolism. MATERIALS AND METHODS: Seven anesthetized piglets (weighing 9.9-12.8 kg), randomized into three groups, served as models for pre-teenage children. Three piglets received a CO(2) embolism, followed by a helium embolism of 2 mL/kg, respectively. Helium was administered to three piglets, whereas both gases were repeatedly administered alternately to one piglet. The embolisms were administered for 30 seconds via a central venous line. Cardiac output was measured using the thermodilution method. The observation period for each embolism was 60 minutes in Groups 1 and 2 and 15 minutes in Group 3. RESULTS: All animals survived CO(2) embolisms. Four of the six piglets died after helium embolisms. Following helium embolisms there was a prompt initial decrease in the end-tidal CO(2) pressure and an initial increase in the pulmonary arterial pressure. A further decrease in arterial blood pressure was prevented by a compensatory increase in the heart rate and appeared just before death. After only 5 minutes cardiac output showed a 25% decline from the initial value. Helium embolisms led to a severe increase in the pulmonary dead space. CONCLUSIONS: Embolisms with the smallest amounts of helium administered via direct venous puncture have an immediate lethal impact. Extended perioperative monitoring and trocar placement under vision should be performed.