Answer
The recoil velocity is $-1.47\times10^{-4}m/s$
Work Step by Step
The patient and platform has mass $M=85kg$ and initial velocity $V_0=0$. The blood has mass $m=0.05kg$, and its initial velocity can be considered to be $v_0=0$. After the heartbeat, $v_f=+0.25m/s$
Since total momentum is conserved, we can the find the recoil velocity of the patient and the platform $V_f$: $$MV_0+mv_0=MV_f+mv_f=0$$ $$85V_f+0.0125=0$$ $$V_f=-1.47\times10^{-4}m/s$$
