Hepatic interstitial laser photocoagulation: demonstration and possible clinical importance of intravascular gas.

PURPOSE: To investigate gas formation during hepatic interstitial laser photocoagulation (ILP). MATERIALS AND METHODS: In vitro, ILP was performed with a neodymium yttrium aluminum garnet laser on a piece of liver in a water bath. In vivo, nine pigs underwent 24 ultrasound (US)-monitored ILP procedures. Fiber tips were more than 1 cm from (n = 16) or adjacent to (n = 8) intrahepatic veins. The gas production seen on US images was graded on a scale of 0 to 4. Precordial Doppler US was performed in all cases. RESULTS: In vitro, smoke bubbles emanated from the vessels during ILP. In vivo, US showed intravascular gas production during nine of 15 exposures of at least 500 seconds duration. Gas production scores of 2 or more were recorded for nine exposures. Intracardiac gas was identified on eight precordial Doppler US recordings. All animals survived. CONCLUSION: Gas was detected in the heart during some ILP exposures. Patients with a probe-patent foramen ovale (24% prevalence) could be at risk for paradoxic air embolus during ILP.