thermodynamics - Microscopic Definition of Heat and Work

If I am given a statistical system, then I can define state-variables like Energy, Entropy or other observables, and then I can (at least for equilibrium states) give the infinitesimal change of energy as:

$$d E = T dS + K dx$$

Here x means any observable and K means the depending force, for example if x is the volume $V$, then K is minus the pressure $-p$. What I read all the time is

$$d E = \delta Q + \delta W$$

Is there a general microscopic way to define what part of the above formula is $\delta W$ and what part is $\delta Q$ ?

For example, for reversible processes, $\delta Q = T dS$ and $\delta W = Kdx$. But what if I'm looking at an arbitrary process?