To quantify the incidence of Quantra QPlus clot time ratio (CTR) elevation (>1.4) in cardiac surgical patients with suspected postoperative coagulopathy and to investigate the correlation between CTR and intraoperative protamine to heparin ratios (PHRs) in cardiac surgical patients.

Retrospective cohort study.

Single academic medical center.

Five hundred two adult patients undergoing cardiac surgery with cardiopulmonary bypass.

None.

Significant postoperative bleeding (24-hour chest tube output > 1 L or need for postoperative packed red blood cell transfusion) was more common among the 175 patients who underwent postoperative sonorheometry than among the 327 patients who did not undergo sonorheometry (31% v 5%, p < 0.0001). Of the 174 patients who had postoperative CTR measured, 5 (2.9% [95% confidence interval, 1.2%-6.5%]; Wilson method) had CTR > 1.4. CTR demonstrated a significant negative correlation with loading PHR (R² = 0.2206, p < 0.0001) and cumulative PHR (R² = 0.2050, p < 0.0001).

Clinically significant residual heparinization was rare in the early postoperative period among cardiac surgical patients with suspected coagulopathy based on sonorheometry CTR. In addition, heparin rebound was observed in only 1 patient with a bolus PHR > 0.8 and in no patients with a cumulative PHR > 0.6.