Background \& Rationale
HES Properties: HES is a synthetic colloid used to maintain blood volume during surgery. While newer "third-generation" HES (130/0.4) is designed to be safer, it may still interfere with blood clotting.
Coagulation Concerns: HES can reduce levels of Factor VIII and von Willebrand factor (vWF) by 50-80%, potentially leading to "dilutional coagulopathy" where the blood cannot clot effectively.
Knowledge Gap: Current evidence is inconclusive regarding whether low-to-moderate doses of HES are truly safe during the removal of large, vascular brain tumors like giant meningiomas.
Study Methodology Study Population: Adult patients (\> 18 years) who underwent craniotomy for a giant meningioma (\> 5 cm) at Maharaj Nakorn Chiang Mai Hospital between January 1, 2016, and December 31, 2024.
Data Collection: Researchers will review electronic medical records to extract data on:
Patient demographics (age, sex, ASA physical status). Surgical details (operation time, estimated blood loss). Fluid management (volume of HES, crystalloids, and blood products given). Laboratory results (pre- and post-operative Serum Creatinine)
Ethical Considerations and Privacy: As a retrospective review of existing records, there is no direct patient contact. Data will be coded to maintain strict confidentiality.Benefits: The findings will help anesthesiologists optimize fluid therapy to improve patient safety and reduce surgical risks.
Statistical Analysis Plan
1. Grouping and ComparisonIn a cohort design, patients will be grouped based on their exposure to Hydroxyethyl Starch (HES) Voluven® or Volulyte® 130/0.4:
Exposed Group: Patients who received HES during surgery. Non-Exposed Group: Patients who did not receive HES (received only crystalloids or other fluids).
Dose-Response Analysis: Patients may also be categorized by the volume of HES received (e.g., \< 500 ml vs. 500-1,000 ml vs. \> 1,000 ml) to see if higher doses correlate with higher bleeding risk.
2. Primary and Secondary Outcomes
Primary Outcome: The cumulative incidence of re-bleeding and required re-craniotomy within 48 hours.
Secondary Outcome: The incidence of new-onset postoperative Acute Kidney Injury (AKI) within 7 days, defined by the KDIGO criteria (Serum Creatinine increase \> 0.3 mg/dl or \> 1.5x baseline).
3. Analytic StatisticsRisk Estimation: We will primarily report Relative Risk (RR) or Hazard Ratios (HR) to describe the risk of bleeding in the HES group compared to the non-HES group.
Confounder Adjustment: We will use Multivariable Logistic Regression or Cox Proportional Hazards Regression to adjust for potential confounders such as age, sex, ASA grade, tumor size, and total blood loss.
Handling Continuous Data: Factors like the volume of HES and estimated blood loss (EBL) will be analyzed using mean/standard deviation and compared using t-tests or Mann-Whitney U tests.
Sample Size Consideration for Cohort Study
For a cohort study, the sample size is determined by the expected incidence of re-bleeding in the unexposed group versus the exposed group.Based on our previous data, the incidence of re-operation is approximately 1.5% to 1.6%.With we planned 9-year data collection (2016-2024), we aim to include all eligible giant meningioma cases (\> 5 cm) to maximize the power of the study.
