In plain words
Who and how is adhiyajña here in this body, Madhusudana? And at the time of death, how are You to be known by those of disciplined mind?
Word for word
How [and] who [is] adhiyajña here in this body, O slayer of Madhu? And how at the time of departure are [You] to be known by those of disciplined mind?
अधियज्ञः कथं कोऽत्र देहेऽस्मिन् मधुसूदनप्रयाणकाले च कथं ज्ञेयोऽसि नियतात्मभिः