Venous capacitance and outflow in the postoperative patient.

Venous capacitance and outflow were measured in a series of 50 unselected patients undergoing a variety of general surgical procedures. Studies done prior to operation and the morning after demonstrated a fall in capacitance and outflow that was related to the degree of ambulation. Fully ambulatory patients demonstrated no changes. Males under the age of 40 were unchanged regardless of the type of operation or degree of ambulation. It is likely that the observed changes reflected a reduction in arterial flow but alterations in venous tone cannot be ruled out.