Clinical Research Directory

Early vs. Late Tourniquet Release and Phlebotomy-Induced Hemolysis in the Emergency Department: TOURNI-ED

Sponsor: Marmara University Pendik Training and Research Hospital

Summary

BACKGROUND: Hemolysis is the most common preanalytical error in emergency department (ED) laboratories, affecting 12-26% of blood samples collected in the ED and leading to test cancellations, repeat venipuncture, delayed diagnoses, and increased healthcare costs. Venous stasis created by tourniquet application during phlebotomy is a recognized contributing factor to hemolysis. While clinical guidelines recommend releasing the tourniquet once blood flow is established, the optimal timing of tourniquet release in relation to tube filling sequence has not been systematically evaluated. OBJECTIVE: The primary objective of this trial is to determine whether early release of sphygmomanometer-applied venous stasis (released after the first tube fills) reduces hemolysis rates compared to late release (released after the last tube fills) during routine phlebotomy in ED patients triaged as green or yellow category. DESIGN: Single-center, parallel-group, superiority randomized controlled trial with 1:1 allocation ratio. The trial was prospectively registered prior to the enrollment of the first participant. PARTICIPANTS: Adult patients (≥18 years) presenting to the emergency department with triage category green (semi-urgent) or yellow (urgent), for whom blood collection is indicated as part of routine clinical care. At least two collection tubes had to be ordered, because the intervention is defined by the timing of cuff release relative to tube filling. Patients requiring blood collection from an intravenous catheter, those with known coagulation disorders, and those who decline to participate are excluded. INTERVENTIONS: Group A (Early Release): Sphygmomanometer inflated to 60 mmHg for venous stasis; tourniquet released as soon as blood flow into the first tube (sodium citrate, blue cap) is observed. All remaining tubes are collected after release. Group B (Late Release): Sphygmomanometer inflated to 60 mmHg; tourniquet maintained throughout all tube filling and released only after the last collection tube completes filling. Tube collection order follows the CLSI H03-A6 standard for both groups. PRIMARY OUTCOME: Hemolysis rate, defined as the proportion of serum separator tube (SST/yellow cap) samples with a Hemolysis Index (HI) ≥ 1+ (corresponding to free hemoglobin ≥50 mg/dL), is assessed by the clinical chemistry laboratory analyzer. The outcome assessor (laboratory technician) is blinded to group assignment. SECONDARY OUTCOMES: (1) Distribution of ordinal hemolysis index categories (-, 1+, 2+, 3+, 4+, 5+) in SST samples; (2) Proportion of hemolyzed samples requiring repeat blood collection; (3) Duration of venous stasis (seconds), from sphygmomanometer inflation to deflation of the cuff; (4) Complication rate (hematoma or ecchymosis, local swelling, oozing at the puncture site, vasovagal reaction, nerve injury, arterial puncture, or more than two venipuncture attempts). SAMPLE SIZE: Assuming hemolysis rates of 12% with late release and 6% with early release, a 2-sided alpha of 0.05, 80% power, and the normal approximation for two proportions with pooled variance, 356 participants per group were required. Allowing approximately 10% attrition, the enrollment target was 396 per group (792 total), and this was reached. RANDOMIZATION: A restricted allocation sequence of 792 assignments in a 1:1 ratio, without stratification, was generated with Research Randomizer (randomizer.org) before the start of enrollment. The sequence as implemented is not consistent with any single fixed block size, so no block size is claimed. The complete sequence was fixed before the first participant was enrolled, was embedded in the electronic data collection application, and was not accessible to the enrolling nurse; a participant's allocation was released only after eligibility had been confirmed and the participant had been enrolled. The realized allocation was 396 participants per group. STATISTICAL ANALYSIS: Primary analysis: intention-to-treat, comparing hemolysis rates with the Pearson chi-square test with Yates continuity correction; the composite complication outcome was compared with the Pearson chi-square test without continuity correction. Secondary analyses: Mann-Whitney U test for the ordinal hemolysis index distribution and for continuous outcomes; logistic regression for the adjusted odds ratio. A Bonferroni-adjusted alpha of 0.0125 was applied across the four confirmatory secondary endpoints; exploratory analyses used alpha of 0.05. Per-protocol analysis was performed as a sensitivity analysis. Missing primary outcome data were addressed with four prespecified scenarios (complete case, best case, worst case, and a tipping-point analysis); the complete-case analysis is reported as primary.

Official title: Early Versus Late Release of Sphygmomanometer-Applied Venous Stasis and Phlebotomy-Induced Hemolysis in the Emergency Department: A Parallel-Group Randomized Controlled Trial

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