Effects of low molecular weight dextran on blood viscosity after craniotomy for intracranial aneurysms

A random, controlled study was performed to determine the effects of low molecular weight dextran on blood viscosity in patients undergoing surgical treatment of intracranial aneurysms. From a total of 13 patients, seven received low molecular weight dextran from the period immediately following the operation through the second postoperative day. The other six received standard postoperative fluid therapy and served as controls. Blood samples were taken on the day prior to surgical intervention and on the first, fourth and tenth postoperative days. Serial blood viscosity measurements were performed on whole blood, plasma and erythrocyte suspensions in plasma and Ringer-albumin solution at controlled hematocrits. These data were analyzed together with plasma protein concentrations, hematologic values and studies of erythrocyte deformability to determine the effect of dextran on postoperative viscosity in these patients. During the period of dextran administration, patients receiving this agent showed a significantly greater decrease in blood viscosity which was largest at low shear rates. This effect appeared to be related to both dilutional and disaggregation qualities of dextran. Tests of erythrocyte deformability showed no difference in either patient group and remained constant during the entire period of observation. As cerebral vasospasm can lead to ischemia and infarction, the ability of low molecular weight dextran to lower blood viscosity while expanding blood volume may offer significant clinical value in the postoperative care of patients with intracranial aneurysms by improving microcirculatory flow and oxygen delivery to tissues.