OBJECTIVE

To assess whether the preoperative level of deoxygenated hemoglobin (HHb) in the calf muscle during light-intensity exercise is useful for identifying patients at risk of developing deep vein thrombosis (DVT) after total knee or hip arthroplasty.

METHODS

Sixty-eight patients undergoing total knee or total hip arthroplasty were enrolled. The Caprini risk assessment model was used to stratify patients into Caprini 5 to 6, Caprini 7 to 8, and Caprini >8 groups. The preoperative diameter of each venous segment was measured, and the time-averaged velocity (TAV) and time-averaged flow (TAF) of the popliteal vein (POPV) were assessed. Moreover, the prevalence of venous reflux in the POPV was evaluated preoperatively. Near-infrared spectroscopy (NIRS) was used to measure the calf muscle HHb level. The calf venous blood filling index (FI-HHb) was calculated on standing, and then the calf venous ejection index (EI-HHb) was obtained after one tiptoe movement and the venous retention index (RI-HHb) after 10 tiptoe movements. All patients received low-dose unfractionated heparin preoperatively and fondaparinux for postoperative thromboprophylaxis. Patients with arterial insufficiency, those who had preoperative DVT, and those who developed bilateral DVT after surgery were excluded from the study.

RESULTS

Four patients were excluded on the basis of the exclusion criteria. Among the 64 patients evaluated, 14 (21.9%) were found to have DVT postoperatively. Among the risk factors for DVT, only the previous DVT was significantly predominant in patients who developed DVT (P = .001). The diameter of the popliteal vein was significantly smaller in patients who developed postoperative DVT than in those who did not (P = .001). Similarly, the diameter of the gastrocnemius vein was significantly larger in patients with postoperative DVT than in those without (P = .010). TAV and TAF were significantly increased in the popliteal vein in patients who developed postoperative DVT (P = .043, 0.046, respectively). Both groups showed a similar prevalence of reflux in the POPV (P = .841). The preoperative NIRS-derived RI was significantly increased in patients who developed DVT relative to those who did not (P = .004). The RI increased as the Caprini score progressed; however, there were no statistically significant differences between the three categories. Using ultrasound- and NIRS-derived parameters of significance as a unit of analysis, an optimal RI cut-off point of >2.3 showed the strongest ability to predict postoperative DVT, followed by a cut-off point >0.25 cm for the diameter of the gastrocnemius vein (GV).

CONCLUSIONS

NIRS-derived RI >2.3 may be a promising parameter for identifying patients at risk of developing postoperative DVT despite pharmacologic DVT prophylaxis. A GV diameter of >0.25 cm also seems to contribute to the development of postoperative DVT. These results might be helpful to physicians for deciding which patients require more intensive thromboprophylaxis.