Intraoperative changes in platelet function in relation to moderate haemorrhage

- We examined platelet function using Multiplate impedance aggregometry intra-operatively
- Platelet function alters over a short time period in response to surgical trauma and moderate blood loss
- Platelet function trends towards increased responsiveness in this setting
- Conduct of impedance aggregometry within the operating theatre environment is feasible

BackgroundHaemorrhage is associated with haemostatic dysfunction. Previous studies have focused on coagulation factors, but platelet function plays an equally important role. The time course of alterations in platelet function in relation to injurious stimuli is not known.AimTo evaluate short-term, intra-operative changes in platelet function, by whole blood impedance aggregometry in patients undergoing hip arthroplasty. The primary outcome was platelet aggregation in response to adenosine diphosphate (ADP) stimulation. We also evaluated other agonists, and the feasibility of conducting platelet aggregometry measurement in the operating theatre.MethodsPatients undergoing primary cemented hip arthroplasty had six peri-operative arterial blood samples analysed at pre-set stages of the operation, using the Multiplate® Impedance Aggregometer. Four agonists were used: ADP, TRAP, Collagen and Arachidonic Acid.ResultsThere was a statistically significant change (p < 0.05, ANOVA) in platelet response to ADP over the course of the operations. The trend demonstrated an initial decrease in responsiveness, followed by increased platelet responsiveness in the later stages. Other agonists (TRAP, COL, ASPItest) demonstrated a similar pattern of changes. Of 360 tests conducted, 12 (3.3%) had to be re-run due to poor intra-assay variability. Satisfactory values were obtained on the second attempt in all 12 samples.ConclusionPlatelet function, as measured by impedance aggregometry, changes in response to a surgical stimulus involving blood loss. The clinical significance of these changes, and the potential of manipulating them for therapeutic purposes, remains to be elucidated.