Rotational Thromboelastometry Findings Are Associated with Symptomatic Venous Thromboembolic Complications after Hip Fracture Surgery

Abstract

Background: Venous thromboembolism is a common complication after hip fractures. However, there are no reliable laboratory assays to identify patients at risk for venous thromboembolic (VTE) events after major orthopaedic surgery.

Question/purposes: (1) Are rotational thromboelastometry (ROTEM) findings associated with the presence or development of symptomatic VTE after hip fracture surgery? (2) Were any other patient factors associated with the presence or development of symptomatic VTE after hip fracture surgery? (3) Which ROTEM parameters were the most accurate in terms of detecting the association of hypercoagulability with symptomatic VTE?

Methods: This retrospective study was conducted over a 13-month period. In all, 354 patients with femoral neck and peritrochanteric fractures who underwent hip hemiarthoplasty or cephallomedullary nailing were assessed for eligibility. Of those, 99% (349 of 354) were considered eligible for the study, 1% (3 of 354) of patients were excluded due to coagulation disorders, and another 1% (2 of 354) were excluded because they died before the postoperative ROTEM analysis. An additional 4% (13 of 354) of patients were lost before the minimum study follow-up of 3 months, leaving 95% (336 of 354) for analysis. A ROTEM analysis was performed in all patients at the time of their hospital admission, within hours of the injury, and on the second postoperative day. The patients were monitored for the development of symptoms indicative of VTE, and the gold standard tests for diagnosing VTE, such as CT pulmonary angiography or vascular ultrasound, were selectively performed only in symptomatic patients and not routinely in all patients. Therefore, this study evaluates the association of ROTEM with only clinically evident VTE events and not with all VTE events. ROTEM results did not affect the clinical surveillance of the study group and the decision for further work up. To determine whether ROTEM findings were associated with the presence or development of symptomatic VTE, ROTEM parameters were compared between patients with and without symptomatic VTE. To establish whether any other patient factors were associated with the presence or development of symptomatic VTE after hip fracture surgery, clinical parameters and conventional laboratory values were also compared between patients with and without symptomatic VTE. Finally, to determine which ROTEM parameters were the most accurate in terms of detecting the association of hypercoagulability with symptomatic VTE, the area under the curve (AUC) for certain cut off values of ROTEM parameters was calculated.

Results: We found several abnormal ROTEM values to be associated with the presence or development of symptomatic VTE. The preoperative maximum clot firmness was higher in patients with clinically evident VTE than in patients without these complications (median [interquartile range] 70 mm [68 to 71] versus 65 mm [61 to 68]; p < 0.001). The preoperative clot formation time was lower in patients with clinically evident VTE than those without clinically evident VTE (median 61 seconds [58 to 65] versus 70 seconds [67 to 74]; p < 0.001), and also the postoperative clot formation time was lower in patients with clinically evident VTE than those without these complications (median 52 seconds [49 to 59] versus 62 seconds [57 to 68]; p < 0.001). Increased BMI was also associated with clinically evident VTE (odds ratio 1.26 [95% confidence interval 1.07 to 1.53]; p < 0.001). We found no differences between patients with and without clinically evident VTE in terms of age, sex, smoking status, comorbidities, and preoperative use of anticoagulants. Lastly, preoperative clot formation time demonstrated the best performance for detecting the association of hypercoagulability with symptomatic VTE (AUC 0.89 [95% CI 0.81 to 0.97]), with 81% (95% CI 48% to 97%) sensitivity and 86% (95% CI 81% to 89%) specificity for clot formation time ≤ 65 seconds.

Conclusion: ROTEM's performance in this preliminary study was promising in terms of its association with symptomatic VTE. This study extended our earlier work by demonstrating that ROTEM has a high accuracy in detecting the level of hypercoagulability that is associated with symptomatic VTE. However, until its performance is validated in a study that applies a diagnostic gold standard (such as venography, duplex/Doppler, or chest CT) in all patients having ROTEM to confirm its performance, ROTEM should not be used as a regular part of clinical practice.

Level of evidence: Level IV, diagnostic study.

Fig. 1

Flowchart of the study population.

Fig. 2

The areas under the receiver operating characteristic curve of preoperative INTEM and EXTEM clot formation time (CFT) and postoperative INTEM maximum clot firmness (MCF) for the diagnosis of VTE complications.