Evaluation of Latex Immunoturbidimetric Assay Thresholds and HIT in Cardiothoracic Surgery.

BACKGROUND: Heparin-induced thrombocytopenia (HIT) is a common differential diagnosis in cardiothoracic surgery. The latex immunoturbidimetric assay (LIA) is an enhanced immunoassay that has recently been introduced for the detection of total HIT immunoglobulin and retains a higher specificity of 95% compared to the enzyme-linked immunosorbent assay. OBJECTIVES: To investigate if a semiquantitative relationship exists between increasing LIA levels beyond the current positivity threshold and its correlation to positive serotonin release assay results in cardiothoracic surgery. METHODS: This was a multicenter, observational cohort of cardiothoracic surgery patients initiated on anticoagulation with heparin-based products. To conduct sensitivity and specificity analysis of LIA values, HIT positive was defined as a LIA value ≥1 unit/mL and HIT negative was defined as a LIA level <1 unit/mL. A receiver operating characteristic (ROC) analysis was utilized to evaluate the predictive performance of the LIA. RESULTS: At manufactures' cutoffs of ≥1.0 unit/mL, LIA sensitivity and specificity was 93.8% and 22%, respectively, yielding a false positive rate of 78%. At a higher cutoff of 4.5 units/mL, LIA sensitivity and specificity was 75% and 71%, respectively, yielding a false positive rate of 29% and an area under the ROC curve of 0.75 (P = .01; 95% confidence interval: 0.621-0.889). Bivalirudin was initiated in 84.6% of false positive LIA results. CONCLUSION: This study suggests that the diagnostic accuracy of the LIA can be optimized by increasing the LIA positivity threshold. Proposing a higher LIA cutoff, may mitigate unwarranted anticoagulation and bleeding outcomes.

Analysis of Bicarbonate-Based Purge Solution in Patients With Cardiogenic Shock Supported Via Impella Ventricular Assist Device.

BACKGROUND: The Impella device is a continuous axial flow pump which provides hemodynamic support by expelling blood into the aorta. The manufacturer recommends using dextrose-based heparin containing solutions as the default purge. As an alternative to anticoagulant solutions, a bicarbonate-based purge solution has been proposed with limited data substantiating adequate protection and durability. OBJECTIVE: To assess the impact of a bicarbonate-based purge solution on Impella pump thrombosis and bleeding outcomes. METHODS: Single-center, retrospective study of cardiogenic shock patients who received an Impella between December 2020 through September 2021. Patients were evaluated based on whether they received bicarbonate-based purge solutions or remained on heparin-based purge solutions. The primary outcome was the rate of Impella pump thrombosis, defined as multiple purge pressures greater than 800 mm Hg. Secondary outcomes included incidence of bleeding defined as a drop in Hgb of at least 2 g/dL along with use of blood products and supratherapeutic anticoagulation defined as an aPTT of greater than 70 seconds. RESULTS: Forty-three patients received bicarbonate-based purge solutions and 49 controls received heparin. The incidence of purge thrombosis by purge pressure threshold was similar between the two groups (16.3% vs 12.2%, P = 0.58). The rate of bleeding was lower with bicarbonate-based purge (27.9% vs 65.3%, P < 0.05) driven by a drop in Hgb of more than 2 g/dL. The rate of supratherapeutic anticoagulation was higher in the heparin arm (65.3% vs 27.9%, P < 0.05). CONCLUSION AND RELEVANCE: Nonanticoagulant purge alternatives offer the potential to reduce bleeding complications and laboratory monitoring burden while maintaining durability.