Patent ID: 8157787

Claim:
A method for infusing and aspirating fluids into and out of a living being, comprising: (a) providing a pumping system comprising: (i) a means of infusing a liquid into said patient; (ii) a means of aspirating a fluid from said patient, each of said means comprising a positive displacement pump other than a peristaltic type pump, said positive displacement pump having an inlet and an outlet side; (iii) an aspiration pathway containing a fluid consisting essentially of liquid during use; (iv) a shut-off valve located on said inlet side of said aspirating means pump, said shut-off valve arranged to close off a pathway of said liquid when the pump is stopped; and (v) means for controlling said pumps; (b) connecting said infusion pathway and said aspiration pathway to said living being to create a fluid circuit; (c) first energizing said aspirating means; and (d) subsequently energizing said infusing means such that a flow rate of infusate is less than a flow rate of aspirate.