Sonorheometry Quantra QPlus Characteristics in Adult Cardiac Surgical Patients: An Observational Cohort Study

Validation of the Quantra QPlus sonorheometry cartridge (Hemosonics Corporation) in cardiac surgical patients is limited. The primary aim of our study was to quantify the accuracy of the Quantra QPlus cartridge in detecting derangements in traditional coagulation tests. Secondarily, we explored whether the relationship between platelet contribution to clot stiffness (PCS) and platelet count was modified by cardiopulmonary bypass (CPB) and hypofibrinogenemia.

We performed a retrospective observational study of 511 cardiac surgical patients at a single academic medical center during the first year of routine sonorheometry application during and after cardiac surgery (2024-2025). Receiver operating characteristics were applied to the following Quantra QPlus parameters, with paired reference laboratory assays sampled in a 15-minute interval: clot time heparinase (CTH), fibrinogen contribution to clot stiffness (FCS), and PCS. A multivariable linear regression model was used to determine whether the relationship between PCS and platelet count was modified by CPB or hypofibrinogenemia.

A CTH value of 153 seconds discriminated elevated international normalized ratio (INR) values post-CPB, with an area under the curve (AUC) from 0.78 to 0.84 depending on the INR cutoff. An FCS of 1.5 to 2.3 hPa discriminated hypofibrinogenemia post-CPB with an AUC from 0.88 to 0.97 depending on the fibrinogen cutoff. A PCS of 6.9 to 12.2 hPa detected thrombocytopenia post-CPB with an AUC from 0.90 to 0.97, depending on the platelet cutoff. In contrast, a PCS of 9.1 to 12.1 hPa detected the same degree of thrombocytopenia on-CPB with an AUC of 0.92 to 0.98. Platelet count was observed to be higher for a given PCS during CPB (β, 1.51) and in hypofibrinogenemic states (β, 3.13 and 4.04 for FCS 1.6-2.3 hPa and ≤1.5 hPa, respectively).

CTH, PCS, and FCS demonstrated high discriminative accuracy for abnormalities in corresponding laboratory assays. CPB and hypofibrinogenemia modified the relationship between PCS and platelet count, with a higher platelet count observed for a given PCS during CPB and when fibrinogen was low.