Multiplexers are one of the most important elements in readout front-end ASICs for multi-element detectors in medical imaging. In the paper a fully asynchronous multiplexer with limited hierarchical de-randomization mechanism has been presented. The hierarchical mechanism prevents collisions in the system, which occur when two or more channels attempts to connect to the output stage. The proposed mechanism enables sequential reading out each of them eliminating that potential collision problem. The results presented in this paper are shown for the case of eight input channels, however the proposed technique can be easily extended to an arbitrary large number of channels. The circuit consumes 15 uW at the power supply of 0.7V, enabling data processing (detection + readout) with 20 MHz frequency resulting in 1pJ energy used to detect one channel. While in a stand-by mode the circuit dissipates 2 nW.