Reference
Izumi, M., Ikeuchi, M., Aso, K., Sugimura, N., Kamimoto, Y., Mitani, T., … Tani, T. (2014). Less deep vein thrombosis due to transcutaneous fibular nerve stimulation in total knee arthroplasty: a randomized controlled trial. Knee Surgery, Sports Traumatology, Arthroscopy, 23(11), 3317-3323. doi:10.1007/s00167-014-3141-z
Introduction
Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), are potential life-threatening complications associated with orthopedic surgeries. In particular, joint replacement surgeries place patients at significant risk for VTE for numerous reasons. Joint replacement surgeries involve significant time under a tourniquet, resulting in a stasis of blood flow. Additionally, these surgeries result in damage to the endothelial lining and place the body in a state of hypercoagulability. Combining these factors places patients at inherently higher risks of developing VTE’s.
Recent evidence suggests that DVT’s don’t just develop postoperatively, but actually begin intraoperatively. This is due to most VTE’s being found within 1 day postoperatively, indicating that the clots most likely formed while surgery was taking place. This is especially evident when despite there being significant advances in post-operative prophylaxis, deaths from PE have remained stagnant. In fact, it appears that most fatal PE occur within the first 5 days postoperatively. Therefore, it appears that postoperative prophylaxis has serious pitfalls. With this recent evidence emerging, it is reasonable to believe that thromboprohylaxis should actually occur intraoperatively rather than postoperatively.
Given this important development, options for intraoperative prophylaxis remain scarce. Pneumatic limb compression has been hypothesized as a possible treatment option, however many surgeons hesitate to utilize this technique because placing a garment on the limb potentially leads to greater infection risk.
Transcutaneous electrical nerve stimulation (TENS) has shown the ability to improve blood flow in the lower extremity and thus offers a potential solution to the intraoperative prophylaxis conundrum. TENS increases blood flow by activing the calf muscle pump. TENS can easily be applied to the skin using sterile pads, takes up relatively little space in the operating room, and can help reduce venous stasis. Therefore, it makes practical sense to examine its effectiveness in the operating room in patients whom are at high risk for VTE (joint replacements).
Purpose:
The purpose of this study was to examine the effectiveness of TENS as an intraoperative tool to prevent VTE, in comparison to the current standard of care which includes postoperative VTE prophylaxis.
Subject Description:
Subjects were randomly allocated to two groups: TENS (n=45) and control (n=45). The average ages were 76 for TENS and 75 for control, with both groups having a higher percentage of female participants (73% TENS, 69% control). Both groups have significant levels of OA on radiograph with TENS at 96% and control 93%. Body mass index was 26.5 (kg/m2) for TENS and 26.6 (kg/m2) for control. None of the differences between groups were significant. Exclusion criteria for the study included a past history of VTE, preoperative detection of DVT, people on anticoagulants or antiplatelet therapy, or the presence of a pacemaker.
Procedures and Methods:
All subjects underwent a total knee arthroplasty (TKA) using standardized procedures (anesthesia etc.) All the surgeries were performed or supervised by the same surgeon with the same anesthesiologist. In the TENS group, sterile electrodes were placed over the common fibular nerve which can be found near the fibular head in the operated leg. The stimulator provided a square-wave pulse of 0.5 ms in duration, 100 V in intensity, at a rate of 10 Hz. These settings provided brief stimulation of the dorsiflexors, generating movement in the ankle. This was applied every 10 seconds every 10 minutes during surgery. The TENS was activated via a foot switch which provided minimal interruption to the surgery. Both groups received post-operative compression stockings and intermittent compression and were encouraged to perform ankle pumps (active ankle motion).
Blood samples were taken pre-surgery, immediate post-operative, and post-operative day 1. These blood samples were drawn to measure serum d-dimer and soluble fibrin monomer (SFMC) complex to detect hypercoagulability. Normal limits are 1.0 lg/ml for D-dimer and 7.0 lg/ml for SFMC. The SFMC provides early clot detection while d-dimer helps to reflect post clot formation.
Ultrasound (US) was used to evaluate the presence of a DVT. The US was performed over the calf and thigh up to the inguinal region. It was performed every 1-2 cm and a DVT was diagnosed if there was intraluminal thrombolytic echogencity and lack of venous compressibility. This process was repeated twice to ensure reproducibility. All patients underwent US evaluation post-op day 1. In patients whom d-dimer levels were above 3.0 lg/ml were also subjected to a preoperative US. When a DVT was found, the patients were followed up 1-2 weeks later. The examiner was blinded to the treatment protocol.
Results:
D-dimer and SFMC were lower immediately post operatively in the TENS group (p<0.05). Immediately post-op the TENS group d-dimer level increased from a baseline of 1.2 [0.9–1.6] and increased to 5.8 [4.6–10.1], while the control which measured 1.2 [0.8–2.3] and 9.3 [5.5–15.0]. Post-op day 1 measurements were not significantly different. SFMC levels at baseline and immediately post op measured 2.4 [1.4–3.6] and 3.7 [2.4–4.7]. While in the same time frame the control measured 1.7 [1.1–3.1] and 4.9 [3.8–8.1]. Like d-dimer, SFMC levels were only significant for immediate post op measurements and were non-significant at post op day 1.
Ultrasound revealed only 5 DVT’s in the TENS group, while the control had 11 (p<0.05). The majority of the DVT’s were found in the soleal vein, while only 1-2 DVT’s were found in the posterior tibial, peroneal, and popliteal veins.
Discussion:
In this paper the authors discovered a novel method to prevent intraoperative VTE formation. Interestingly, not only did the application of TENS help prevent venous stasis, but it also demonstrated improvements in hypercoagulability which was noted by reduced d-dimer and SFMC levels immediately post-op. Additionally, the rate of DVT’s was much lower in the TENS group when compared to control (11% vs. 31%). The application of TENS appears to address both the issues of venous stasis (from the limb being under a tourniquet) and the hypercoagulability of blood.
Furthermore, the addition of TENS intraoperatively has little downside. It does not provide a bleeding risk, like other treatments such as heparin. Increased bleeding also increases the risk for infection. It is easy to apply and does not restrict the surgeon. Essentially, it provides all benefit with little risk of complication.
Conclusion:
In conclusion, the data presented in this paper supports the use of TENS intraoperatively to reduce the incidence of VTE. TENS reduces the risk for VTE through two mechanisms: it prevents venous stasis and reduces hypercoagulability of blood. In light of these findings, it appears TENS offers a relatively low-risk high reward treatment to address intraoperative clot formation.
No comments yet.