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
