hearing the squeak

In Wallace's Infinite Jest, US and Canadian state officials live in fear of a secret terrorist group of Quebec separatists.  Members of this terrorist group have lost both legs and hence move about in wheelchairs; they are known as the wheelchair assassins.  They may appear handicapped, but they are very good at what they do and are greatly feared.  They can strike at any time;  the only warning the victim has before the attack is to hear the squeak of wheelchair wheels. High ranking state officials live in fear of "hearing the squeak".  
Here I sit in Albuquerque awaiting liver transplant number four.  It can come at anytime, day or night without warning.  When my cell phone rings with a call from Florida it is time.  I fear the moment even as I hope it comes soon, for I know that without the transplant my time is short.  Still, I live in fear of "hearing the squeak".