Heat generation due to drilling during spinal surgery is potentially hazardous to nerves. Saline irrigation is often performed to prevent such local heating, but sometimes floods and obscures the operative field. We have developed a spray-irrigation system for attachment to high-speed drills, which sprays saline solution with an air-jet in the direction of the surface cut by the drill. We anticipated that this air jet would create a clearer operative view by displacing excess fluid, and would also provide an added cooling effect greater than that of irrigation with saline. This study was designed to evaluate these predicted effects of the spray-irrigation system compared to conventional irrigation. A thermography study was performed to confirm the cooling effect of the spray-irrigation system. A plaster board coated with adhesives was drilled at 100,000 rpm along a 10-cm line for a duration of 20 seconds. Thermograms were recorded every minute, without cooling, with irrigation, and with the spray-irrigation system. To examine the operative views, continuous drilling for a period of seconds was performed with conventional irrigation and with the spray-irrigation system. Local heating was inhibited by the spray-irrigation system to 14-30% of that with irrigation. A clear operative field was maintained during continuous drilling using the spray-irrigation system through the air-jet action of the system. The spray-irrigation system can simultaneously provide effective cooling and a clear operative field during surgical manipulations with high-speed drills.