In cats that are difficult to unblock, we use the soft portion of a 22-ga intravenous catheter and sterile saline solution in a 3-ml Luer lock syringe. The force that you can get with an intravenous catheter seems to be stronger than other options and is relatively atraumatic. If we are unable to unblock the cat using sterile saline solution, then we use a mixture of lubricant and saline solution that, with time and persistence, always works. By using these two methods, we haven't yet encountered a cat that we have been unable to eventually unblock relatively atraumatically.