Impact of Intravascular Fluid Resuscitation on Whole Blood Viscosity During Endovascular Detachable Coiling Procedure for Unruptured Intracranial Aneurysm: A Prospective Randomized Controlled Trial

Abstract

Background: Whole blood viscosity (WBV) determines wall shear stress, representing dynamic force and contributing to aneurysmal remodeling. We hypothesized that administering balanced crystalloid (Group-C) or hydroxyethyl starch (HES) 130/0.4 (Group-HES) for IV fluid management would have a different impact on high-shear WBV during the endovascular detachable coiling (EDC).

Methods: Thirty EDC patients randomly got HES (Group-HES, n = 15) or crystalloid (Group-C, n = 15) as the main IV fluid resuscitation during the procedure. The WBV at a shear rate of 300 sec^-¹ of arterial blood samples (WBV₃₀₀), which depict WBV at a larger-sized artery, were determined and analyzed before and after the EDC procedure (Pre and Post). The changes in hematocrit (Hct) and arterial-to-inspired-fraction oxygen ratio (P/F-O₂ ratio) were determined as indices of the degrees of hemodilution and extravascular fluid shift, respectively.

Results: The median (25-75%) volume of infused crystalloid was 800 (700, 1,200) mL in Group-C and those of HES and crystalloid were 400 (150, 750) and of 500 (400, 600) mL in Group-HES, respectively. Pre-WBV₃₀₀ showed no significant inter-group difference. However, Post-WBV₃₀₀ in Group-HES was significantly lower than in Group-C (3.40 ± 0.33 vs. 3.95 ± 0.79 centipoise, P = 0.023). The Hct and P/F-O₂ ratios were comparable between the two groups.

Conclusion: Our study showed that HES infusion provided significantly lower WBV than crystalloid infusion during the EDC procedure. Further study is warranted to determine whether the lower WBV after HES infusion would enhance clinical outcomes.

Trial registration: ClinicalTrials.gov Identifier: NCT02700607.

Keywords: Blood Viscosity; Colloid; Crystalloid; Endovascular Procedure; Hemodilution; Intracranial Aneurysm.

Fig. 1. Schema for analyzing WBV at various SRs with the scanning capillary tube viscometer. The blood sample was introduced into a single-use U-shaped tube. When the computer-controlled 3-way valve in the tube was opened, gravity allowed blood at a higher position in the column to fall (A) and blood at a lower position to rise (B). The optical array of the viscometer detected the elevation and depression of the blood levels (arrows A and B), and the viscosity was automatically determined by the pressure drop and flow rate change, compensating for the effect of surface tension inside the tubes. The initial blood flow rate was determined by the height difference of blood columns in both arms of the U-shaped tube and the diameter of the horizontal part of the tube in the viscosity detector. Throughout a viscosity test, the flow rate inside the capillary tube varied from an initial maximum speed down to zero when the two fluid levels in the columns reached the same elevation. From a single automated scan of this sweeping and decelerating motion of the blood column, the viscometer captured WBV data at the varying SRs (1–1,000 sec⁻¹).

WBV = whole blood viscosity, SR = share rate.

Fig. 2. Consolidated Standards of Reporting Trials flow diagram.

Group-C = patients with balanced crystalloid infusion, Group-HES = patients with hydroxyethyl starch (130/0.4) infusion, EDC procedure = endovascular detachable coiling procedure, O₂ = oxygen.

Fig. 3. The changes in WBV₃₀₀ before and after the EDC procedure. Data are presented as mean ± standard error.

WBV₃₀₀ = whole blood viscosity at share rate of 300 sec⁻¹, EDC procedure = endovascular detachable coiling procedure, Group-C = patients with balanced crystalloid infusion, Group-HES = patients with hydroxyethyl starch (130/0.4) infusion, cP = centipoise, Pre = preoperative, Post = postoperative. ^*P = 0.023 compared to Group-C.

Fig. 4. The changes in WBV₅ before and after the EDC procedure. Data are presented as mean ± standard error.

WBV₅ = whole blood viscosity at share rate of 5 sec⁻¹, EDC procedure = endovascular detachable coiling procedure, Group-C = patients with balanced crystalloid infusion, Group-HES = patients with hydroxyethyl starch (130/0.4) infusion, cP = centipoise, Pre = preoperative, Post = postoperative. ^*P = 0.011 compared to Group-C.