It seems that you are offline so I am writing you the initial answer. You may ask follow up questions, if you have any.
The lumbar block, acts as a sympathetic block. This is known to act as following;
1) Facilitate the venous and lymphatic flow from the limbs to the main circulation.
2) Autonomic nervous system effect on the overall tissues of the lower limb including muscles, ligaments, tendons, skin, subcutaneous tissue etc to direct the intracellular fluids (water and salts in between the cells) to intravascular (in the blood vessels) fluid. That reduces the edema.
Please see the reference:
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
Thanks for using Just Answer.