Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Ambulatory Anesthesia
Deep venous thrombosis (DVT) is a matter of concern in clinical practice, since pulmonary embolism contributes to 10 - 25% of hospital deaths.  Morbidity after DVT is considered, the incidence of postphlebitic syndrome is as high as 51% after DVT associated with long bone fractures . Different methods have been used to protect against postoperative DVT during surgery by attacking one or more of the pathological triad of venous stasis, increased blood viscosity and vessel wall injury. This study demonstrates the effect of transcutaneous electric nerve stimulation(TENS) applied to the skin over the calf muscles, on venous blood flow as measured in popliteal vein.
METHODS: This study was performed on 20 consented volunteers of both sexes ASA I&II after IRB approval. TENS Medisana apparatus was used, after through cleaning of the skin on calf area with alcohol, 2 electrodes of the first channel were attached to the upper and lower ends of the skin of calf muscles. The 2 electrodes of second channel were attached to the sides of calf area in a line perpendicular to the electrodes of the first channel. Pulse width was adjusted approximately to 160 us, frequency and intensity were adjusted, in each volunteer to get the maximum tolerable vibration and tingling sensations. Blood flow in popliteal vein was measured before and 15 min after running electric current using duplex sonography. The same steps were applied to the other leg of each volunteer, so a total of 40 legs were studied. Paired t-test was used for statistical analysis with P < 0.05 being significant.
RESULTS: TENS increased the velocity of venous blood in the popliteal vein. Blood flow was significantly increased by about 5 folds (with P<0.001). The mean blood flow before and 15 min after TENS was 17.53 +/- 0.85 and 92.13 +/- 3.61.
DISCUSSION: DVT of the lower limbs is a common post-operative complication, and it is the most common cause of pulmonary embolism. Different methods have been used to protect against DVT. Mechanical methods such as elastic compression stockings or intermittent pneumatic compression are uncomfortable to the patients, the later method was reported to increase intra-operative bleeding in patients who underwent radical pelvic surgery.  The use of thromboprophylactic agents such as heparin carries the risk of bleeding and needs frequent blood tests and dose adjustments. TENS proved to be very effective in increasing the velocity of venous blood in the lower limbs, an important mechanism in protecting against DVT. The potential risks of the thromboprophylactic agents in certain situations makes the use of TENS a better alternative. In pregnancy, there is a six-fold increase in the risk of thromboembolism. Again in patients with stroke the risk of intracranial bleeding when these agents are used makes TENS a safer alternative.
CONCLUSION: TENS is a safe and effective method in increasing the velocity of venous blood in the lower limbs. It is simple to use, very safe comfortable to the patient and inexpensive. Compared to other methods, TENS has no side effects, no bleeding tendency and no need for any drugs or frequent blood tests. It is very suitable in patients where the use of heparin is contraindicated or in short surgical procedures with early ambulation.
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