We have $f(2) = 2^2 + 2\sqrt{2} = 4 + 2\sqrt{2}$ and $f(8) = 8^2 + 2\sqrt{8} = 64 + 2\sqrt{8}$.
So, $2f(2) - f(8) = 2(4 + 2\sqrt{2}) - (64 + 2\sqrt{8}) = 8 + 4\sqrt{2} - 64 - 2\sqrt{8}$.
Simplifying, we get $8 + 4\sqrt{2} - 64 - 2\sqrt{8} = -56 + 4\sqrt{2} - 2\sqrt{8}$.
Since $\sqrt{8} = \sqrt{4 \cdot 2} = 2\sqrt{2}$, we have $-56 + 4\sqrt{2} - 2\sqrt{8} = -56 + 4\sqrt{2} - 4\sqrt{2} = \boxed{-56}$.
The answer is: -56
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Consider the function $f(x) = x^2 +2\sqrt{x}$.  Evaluate $2f(2) - f(8)$.

### Answer:
