Lasers in Surgery and Medicine zy 8:72-76 (1988) Gas Volume Quantitation During Argon Ion Laser Ablation of Atheromatous Aorta in Blood and 0.9% Saline Media With an Optically Shielded Catheter G. Stefan Davis, MD, Corinne Bott-Silverman, MD, Marlene Goormastic, MPH, Ross G. Gerrity, PhD, Carter Kittrell, BS, Michael Feld, PhD, and John I?. Kramer, MD zyxwv Department zyxwvutsrq of Cardiology, Cleveland Clinic Foundation, Cleveland (G.S. D., C. 6.-S., M.G., R. G.G., J. R. K.), and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge (C.K., M.F.) Using an optically shielded fiber optic laser catheter, the amount of gas produced when firing an argon ion laser into 0.9% saline solution or blood alone and into atheromatous aorta in either a blood or 0.9% saline medium was quantitated. Energies from zyxwv 0.25 to 4 joules (J) were used at powers of 2, 5, and 8 W. We found that total volume of gas produced is small not only at equilibrium (0.3 zyxw f 0.1 pllJ when firing in blood alone and also when ablating aorta in blood or saline media) but also at peak (2.5 zyxwvut f 0.2 pllJ firing in blood alone and 1.0 f 0.1 pl/J or 0.9 f 0.1 pI/J when ablating aorta in saline or blood, respectively). Because these volumes are small, a clinically significant event from a gas em- bolus is unlikely during intravascular laser ablation of atheromatous plaque in the energy and power range studied. No gas was quantitated when firing the argon ion laser into 0.9% saline solution alone. The peak gas volume when firing in blood alone was significantly greater than that produced in the other chamber environments. This is thought to be due to increased absorption of argon laser light by hemoglobin. The gas volumes produced by lasing aorta in 0.9% saline or blood were not statistically different. zyxwvu . Key INTRODUCTION words: laser angiosurgery, laser byproducts, laser gas production, argon ion laser, laser catheter The use of lasers for the treatment of occlu- sive atherosclerotic disease requires an under- standing of the interaction of laser light with vascular and intravascular components. When laser light ablates tissue in a blood vessel, partic- ulate and gaseous byproducts are generated within the vessel lumen, which may be carried down- stream. Gas production during laser irradiation of atherosclerotic plaque has been observed by sev- eral investigators [Abela et al, 1982; Choy et al, 1982; Van Gemert et al, 1985; Welch et al, 19851. Qualitative analysis of equilibrium gas byprod- ucts have been published [Kaminow et al, 1984; Isner et al, 19851, but quantitation and the dy- namic flux of gas volumes during laser firing have not been reported. zyxwvut 0 1988 Alan R. Liss, Inc. Strikwerda and colleagues [Strikwerda et al, 1988a,b] have shown that the volume of tissue removed by impinging laser light is a function of the fluence used. For example, when using the appropriate power, time, and spot size, a fluence of 5.1 J/mm2 will remove almost 0.1 0.01 mm3 of tissue, while a fluence of 10 J/mm2 will remove approximately 0.3 f 0.04 mm3. It also can be shown that gaseous debris, a byproduct of tissue removal, is a function of the fluence delivered to the tissue target. Accepted for publication November 12, 1987. Address reprint requests to John R. Kramer, MD, Depart- ment of Cardiology, Cleveland Clinic Foundation, Cleveland, OH 44106.