Absorption characteristics at 1.9 microns: effect on vascular welding.
A 1.9 microns laser was used to investigate the acute weld strengths for anastomoses of rat and rabbit aortas and femoral arteries. The wall thicknesses for these vessels approximately matched the optical absorption depth of 125 microns for 1.9 microns radiation in vascular tissues. A low power (150 mW) 1.9 microns laser was used. Laser power was delivered through silica fiber optics for manual control. The fiber tip was held approximately 1 mm from the target resulting in a laser spot size of 0.7 mm at the tissue. The linear delivery rate was approximately 0.3 mm/sec. Acute burst pressures of the welds showed a linear correlation with the reciprocal of the vessel radius. These results suggest that the product of the weld strength times the optical absorption depth is constant over the range of vessel sizes studied. A weld strength for a weld thickness equal to the optical absorption depth was determined to be 4 x 10(6) dynes/cm2, which is comparable to the strength of sutured anastomoses. These acute studies suggest that a laser wavelength with absorption depth in tissue matched to the vessel wall thickness should yield optimum welds. Therefore, a laser operating near 1.9 microns is suitable for small vessel welding.