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Delis KT. This letter is in response to comments in the abstract section of Journal of Vascular Surgery (2004;40:834) on our study originally published in the British Journal of Surgery (2004;91:429-34). Graft flow attenuation and surface thrombogenicity perioperatively, in a milieu of increased tissue thromboplastin release, platelet reactivity, and coagulation factors, are known to enhance significantly the likelihood of infrainguinal graft thrombosis. The potential of assisting graft flow is appealing, particularly in patients with run-off limitations and surgical imperfections amidst cardiac or hematologic impairments; yet, there is a conspicuous scarcity of such methods in practice. By causing peripheral resistance to decrease, prostaglandins generate a significant increase in graft flow. Iloprost, a synthetic analogue of prostacyclin, offers a short-lived[20-min] flow enhancement of 50% when infused into femorodistal grafts before perfusion. In contrast, intermittent pneumatic compression (IPC) enhances volume flow[median] in infrainguinal grafts by 76% when applied to the foot (IPCfoot) and ≤236% when applied to the foot and calf (IPCfoot+calf). Epidural anesthesia is also highly effective in enhancing graft flow; however, its use is restrictive to patient’s mobility and may prolong high dependency in-hospital care and convalescence. Effects of anesthesia on peripheral hemodynamics. Mean velocity (median and interquartile range) before, during, and ≤30 minutes of elective abdominal surgery in 10 patients receiving general anesthesia and 9 patients receiving general-and epidural anesthesia (ASA1-2). Statistics based on the Mann-Whitney test. Optimal IPC function presupposes priming of the limb veins, ensured by dependency. Yet, the theoretical potential of leg edema did not prevent IPC becoming an indispensable tool for preventing deep venous thromboembolism (DVT). Edema, or its persistence, reflects an imbalance between fluid outflow through the walls of the relatively high-pressure afferent limbs of the capillary loops and osmotic reabsorption into the low-pressure venous limbs. Courtesy of the venous emptying and pressure attenuation in the lower limb, IPC reverses the effects of gravity, preventing and or treating peripheral edema rather than causing it to occur. Quoted from the abstract commentary “it is unclear whether these devices will increase in postoperative discomfort in the operated extremity”. Yet, patients after arterial bypass grafting are given regular analgesia. Furthermore, IPC implementation for DVT prevention in orthopedic patients is well tolerated. Patients with intra-articular fractures of the calcaneum treated with IPCfoot had a significant improvement in movement, pain perception, and convalescence, compared with controls. In critically ischemic limbs, IPC is not only well tolerated but is also reported to offer symptomatic relief due to the resulting arterial flow enhancement Restricting “the practical significance of IPC” it is quoted that the “pedal devices may be contraindicated in patients with pedal gangrene and calf devices contraindicated in patients with distal calf wounds.” Yet, different pneumatic cuffs and modes offer IPC ample flexibility: IPCfoot+calf may be used in femoropopliteal grafts above the knee, IPCfoot in femorocrural grafts, IPC of the thigh in popliteal-pedal grafts and IPCcalf with narrow cuffs in femoropopliteal grafts below the knee or femoropedal grafts. Long skin bridges in saphenous procurement may further the applicability of IPC, which may be used for intervals equal to those for DVT prophylaxis. In our practice, amongst 100 patients offered infrainguinal bypass grafting in the past 6 months, IPC implementation would have been possible in >85% of patients. From this viewpoint the data of the study abstracted and commented upon by Dr Moneta, to whom I am grateful, warrant prospective evaluation to enable determination of IPC’s actual efficacy, if any, in preventing thrombosis in grafts at risk perioperatively. |
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