Sonographically Guided Thrombin Injection of Iatrogenic Femoral Pseudoaneurysms: Further Experience of a Single Institution

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1 Erik K. Paulson 1 Rendon C. Nelson 1 Charles E. Mayes 2 Douglas H. Sheafor 1 Michael H. Sketch, Jr. 2 Mark A. Kliewer 1 Received January 19, 2001; accepted after revision February 21, Presented at the annual meeting of the American Roentgen Ray Society, Washington, DC, May Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC Address correspondence to E. K. Paulson. 2 Department of Cardiology, Duke University Medical Center, Durham, NC. AJR 2001;177: X/01/ American Roentgen Ray Society Sonographically Guided Thrombin Injection of Iatrogenic Femoral Pseudoaneurysms: Further Experience of a Single Institution OBJECTIVE. In September 1998, we began to treat iatrogenic femoral pseudoaneurysms with direct thrombin injection under sonographic guidance. Our purpose was to determine the success and complication rate of this technique. SUBJECTS AND METHODS. We treated 114 consecutive patients who had iatrogenic femoral pseudoaneurysms using direct thrombin injection. A 22-gauge spinal needle was placed into the pseudoaneurysm lumen with sonographic guidance, and bovine or human thrombin (mean dose, 306 U; range, U) was injected under continuous color Doppler sonographic visualization. Distal pulses were monitored. Patient demographics, clinical variables, and pseudoaneurysm characteristics were collected. RESULTS. One hundred three (90%) of 114 patients had pseudoaneurysm thrombosis after the first procedure. Of the remaining 11 patients who required a second procedure 1 day later, thrombosis occurred in seven (64%) of 11. Thus, the overall success rate was 96% (110/ 114). Of the patients who required one injection, the mean thrombosis time was 12 sec (range, 3 90 sec). Three (3%) of 114 patients required conscious sedation. Of the patients with successful thrombosis, 24-hr follow-up sonograms showed no recurrent pseudoaneurysm. Four patients (4%) had potential complications: a blue toe 15 hr after the thrombin injection that resolved spontaneously, a groin abscess, leg ischemia that resolved spontaneously after 4 hr, and crampy buttock pain that resolved spontaneously. CONCLUSION. For the treatment of iatrogenic femoral pseudoaneurysms, thrombin injection under sonographic guidance is a quick and effective method of therapy. Failures and complications are infrequent. At our institution, sonographically guided thrombin injection has replaced compression repair. F emoral artery pseudoaneurysms are an uncommon but well-recognized complication after cardiac catheterization [1]. The incidence of pseudoaneurysm formation ranges from 2% to 8% after coronary angioplasty and stent placement and from 0.2% to 0.5% after diagnostic angiography [2]. The incidence of iatrogenic femoral pseudoaneurysms may be increasing because of the more frequent use of aggressive anticoagulant regimens and large-diameter vascular sheaths [3 7]. Traditionally, iatrogenic pseudoaneurysms have been treated with surgery to avoid the risk of rupture [4, 8]. However, since the description by Fellmeth et al. [9] in 1991, sonographically guided compression repair has become the first line of treatment for iatrogenic pseudoaneurysms in many institutions [10]. Although compression is relatively safe and effective, it has considerable limitations. Specifically, the duration of compression is lengthy, the procedures are painful and require conscious sedation, the success rate is only 75% (lower in patients undergoing anticoagulation), and compression is contraindicated in some patients [11]. Sonographically guided injection of thrombin has emerged as an alternative to sonographically guided compression repair. Studies have reported success rates of % [12 22]. The reported complication rate is approximately 2%. The procedure is usually expeditious and effective in pseudoaneurysms not amenable to compression, including those located above the inguinal ligament, those that are very tender, those in patients undergoing anticoagulation, and those in which flow cannot be arrested despite prolonged and strenuous effort [22]. However, as with any new technique, and particularly one so dramatically successful, it is prudent to proceed with caution. Reported expe- AJR:177, August

2 Paulson et al. rience to date is based on relatively small patient numbers. Series with large numbers of patients are needed to establish the indications, limitations, and true complications of this technique. The purpose of this paper is to review our further experience with the treatment of iatrogenic femoral pseudoaneurysms using the sonographically guided percutaneous injection of thrombin. Subjects and Methods In September 1998, we began to treat pseudoaneurysms resulting from femoral artery puncture with direct thrombin injection under sonographic guidance, based on the promising results of Kang et al. [13]. Since then 121 patients have been referred to our laboratory for treatment. In one of these referred patients, the pseudoaneurysm had spontaneously thrombosed in the interval between discovery and treatment. Of the remaining 120 patients, 107 were referred for thrombin injection as the initial and primary therapy for pseudoaneurysm, and 13 were referred for sonographically guided compression repair because the referring team was unfamiliar with or uncomfortable with the thrombin technique. In these 13 patients, compression repair was successful in four. Of the nine patients whose compression repair failed, seven underwent successful treatment with thrombin injection, one underwent surgical repair, and one had a pseudoaneurysm that eventually thrombosed spontaneously. Thus, to date thrombin injection has been used to treat 114 patients. Treatment of 26 of these patients was previously reported [22]. Before thrombin injection, sonography of the puncture site was performed using real-time equipment (XP scanner, Acuson, Mountainview, CA; HDI 3000 scanner, Advance Technology Laboratories, Bothell, WA; or Logiq 700 scanner, General Electric Medical Systems, Milwaukee, WI) with a variety of transducers ranging from 3.5 to 7 MHz. An experienced sonographer performed each examination. Criteria used to diagnose a pseudoaneurysm included swirling color flow in a mass separate from the underlying artery, color flow signal in a track leading from the artery to the mass consistent with a pseudoaneurysm neck, and a to-and-fro Doppler waveform in the pseudoaneurysm neck. The relationship between the lumen and the underlying neck and artery was delineated. The soft tissues surrounding the pseudoaneurysm were inspected for evidence of an arterial venous fistula or additional interconnecting pseudoaneurysm lobes. The artery and vein were confirmed to be patent. Written informed consent was obtained from each patient after discussing the procedure and alternative therapies. The thrombin technique was not specifically approved by our institutional review board because adoption of this procedure became the standard of care in our practice [12, 13]. Sonographically guided thrombin injection was performed using the technique described by Kang et al. [13]. Using a Logiq 700 sonography unit equipped with a MHz linear array or curved linear array transducer, we scanned the groin at the puncture site to reconfirm the anatomy of the pseudoaneurysm and major vessels. The overlying skin was prepared with povidone-iodine and covered with a sterile drape. Using an attachable biopsy guide, we carefully advanced a 22-gauge Fig. 1. Drawing illustrates percutaneous injection of thrombin directly into pseudoaneurysm lumen. Using attachable biopsy guide, 22- gauge spinal needle is advanced into lumen, carefully avoiding pseudoaneurysm neck and underlying artery. Once needle is in position, thrombin is slowly injected. Flow in lumen is monitored with color or power Doppler sonography. Formation of thrombus generally occurs within seconds. (Reprinted with permission from [22]) spinal needle into the lumen so as to avoid the pseudoaneurysm neck, femoral artery and vein, and branch vessels (Fig. 1). The needle shaft was preloaded with thrombin and attached to a 1-mL syringe also containing thrombin. In 101 patients, bovine thrombin (1000 U/mL, Johnson & Johnson, Middleton, WI) was used. Bovine thrombin is packaged as a sterile powder reconstituted with normal saline. In 13 patients, human thrombin (500 U/mL) (Tisseel VH; Baxter, Glendale, CA) was used. The human thrombin is part of a fibrin sealant kit that consists of human thrombin, calcium chloride solution, and a sealer protein concentrate containing bovine aprotinin. The freeze-dried human thrombin is reconstituted with the calcium chloride solution and injected in the same manner as the bovine thrombin. To facilitate visualization of the needle during insertion, it was often necessary to turn off the color Doppler component of the duplex image and use gray-scale imaging alone (Fig. 2). Once the needle was optimally positioned in the pseudoaneurysm lumen, color Doppler imaging was restored to monitor the patency of the lumen during thrombin injection. Over 3 5 sec, U of thrombin was injected. In many cases, the thrombin injection was evident as a color jet emanating from the needle tip. After the first dose, the flow in the lumen was monitored with color Doppler sonography to detect the formation of thrombosis. In cases in which partial thrombosis occurred after the initial injection, a second injection of U into the remaining lumen may have been needed with or without needle repositioning. Once the pseudoaneurysm was thrombosed, the needle was removed. The presence and quality of pulsations of the dorsalis pedis and the posterior tibialis arteries were documented before, during, and after the injection. The procedures were quick and were usually limited to a single skin puncture with a thin needle; conscious sedation was usually not required. After the injection of thrombin, patients were instructed to lie in bed (with the affected leg straight) for 6 hr, with frequent groin and foot pulse checks. The procedure was considered successful if complete thrombosis of the lumen occurred. In cases in which complete thrombosis occurred but residual flow was seen in the pseudoaneurysm neck, no attempt was made to inject thrombin directly into the pseudoaneurysm neck. In these cases, follow-up groin sonography was performed approximately 24 hr after the procedure to assess the interval thrombosis of the neck. For each procedure, we reviewed patient demographics, site of involvement, type of catheter (diagnostic or angioplasty/stent), sheath size, and the use of systemic heparin or warfarin at the time of the thrombin injection. Additionally, the size (largest single dimension) of the pseudoaneurysm, number of pseudoaneurysm lobes, neck length, and neck width were reviewed. Procedure details were reviewed, including type of thrombin used, thrombin dose, number of needle passes, number of injections, and the use of conscious sedation. Specifics of pseudoaneurysm thrombosis were also reviewed, including time to pseudoaneurysm thrombosis and 310 AJR:177, August 2001

3 Thrombin Injection of Femoral Pseudoaneurysms Fig year-old woman with pulsatile groin mass identified 2 days after coronary angioplasty. A, Transverse color Doppler sonogram at groin puncture site shows cm pseudoaneurysm. Pseudoaneurysm neck and femoral artery are not shown on this image. B, Using gray-scale sonographic technique, 22-gauge needle is passed into lumen. Note echogenic needle tip (arrow ). Particular care is taken to avoid underlying artery and pseudoaneurysm neck. C, Transverse color Doppler sonogram obtained 12 sec after injection of 650 U of thrombin shows complete thrombosis of lumen. Echogenic material (arrows) represents fresh thrombus. whether the thrombosis of the lumen and neck was complete or partial. In some cases in which the pseudoaneurysm was incompletely thrombosed, manual compression was applied to the areas of persistent flow to augment thrombosis. The duration of these periods of compression was reviewed. Follow-up sonography of the groin was performed after hr in 81 (71%) of 114 patients. Results From September 1998 through November 2000, 114 patients with iatrogenic femoral B pseudoaneurysms were treated with thrombin injection. A total of 125 thrombin injection procedures were performed (11 patients underwent two separate procedures). Demographic and procedure details are summarized in Table 1. Table 2 summarizes the technical aspects and results of the thrombin procedure. The mean dose of thrombin was 306 U but ranged from as little as 50 U to as much as 1600 U. In 29 procedures (23%), complete thrombosis was achieved with a dose of 100 U or less. Ninety-nine (79%) of the procedures required a single needle pass and a single injection. Twenty-six (21%) of the 125 procedures resulted in only partial thrombosis of the lumen after the first injection and required additional treatment. For these patients, it was usually necessary to simply reinject thrombin without needle manipulation. In some of these patients, it was necessary to advance or withdraw the needle a few millimeters into the patent portion of the lumen without removing the needle from the skin. A C AJR:177, August

4 Paulson et al. TABLE 1 Demographic Details of 114 Patients with Pseudoaneurysms Detail No. Range Mean age (yr) Sex (male:female) 43:71 Mean days after sheath removal Procedure Angioplasty or stent placement 72 (63) Diagnostic 36 (32) Other 6 (5) Mean sheath size (Fr) Femoral puncture site (right:left) 95:19 Mean lumen diameter (cm) Mean neck length (mm) Mean neck width (mm) Multilobular pseudoaneurysms 31 (27) Note. Numbers in parentheses are percentages. However, one patient required two separate skin punctures to appropriately position the needle in the lumen. The injection of thrombin precipitates thrombosis quickly. For the procedures in which a single injection was required, mean thrombosis time was only 12 sec. Although the groin site was tender to palpation in most Technical Aspects of 125 TABLE 2 Thrombin Injection Procedures Item No. Patients 114 Undergoing anticoagulation a 24 (19) Procedures 125 Bovine thrombin 109 Human thrombin 16 Thrombin dose (U) Mean 306 Range Injections One 99 (79) Two 19 (15) Three 6 (5) Four 1 (1) Thrombosis Time b (sec) Mean 12 Range 3 90 Conscious sedation 3 (3) Supplemental compression 12 (10) Duration of (min) 5.9 Note. Numbers in parentheses are percentages. a Patients who were undergoing systemic anticoagulant therapy at time of thrombin injection. b Based on patients who required only one injection of thrombin. patients, the passage of the 22-gauge spinal needle was well tolerated in all cases. Only three procedures required the use of conscious sedation. Most (97%) of our procedures were performed without conscious sedation or local anesthesia. For 12 procedures, sonographically guided compression was applied for a brief TABLE 3 Success Rate of Thrombin Injection in 114 Patients a Includes results of patients who underwent second procedure. period immediately after thrombin injection to complete thrombosis of the lumen (Fig. 3). In contrast to traditional sonographically guided compression repair for which compression may be needed for 60 min or longer, only a few minutes (mean, 5.9 min) of compression was required after thrombin injection. Presumably, the presence of fresh thrombus after thrombin injection potentiates complete thrombosis once the flow has been arrested with compression. Procedure success is shown in Table 3. Of the 114 patients who received thrombin, 103 (90%) had complete thrombosis of the lumen after the first procedure. The 11 patients who had persistent flow after the initial thrombin procedure were scheduled for a second attempt to be performed the next day. In these 11 patients, seven pseudoaneurysms were successfully thrombosed after the second thrombin procedure. Thus, including both first and second procedures, our overall success rate was 110 (96%) of 114. The four pseudoaneurysms that did not thrombose after the second thrombin procedure were considered thrombin failures. Of these four pseudoaneurysms, three underwent uneventful surgical repair. Two of these three patients had rents at the femoral artery puncture site: one tear Fig year-old woman with persistent pseudoaneurysm flow after injection of 300 U of thrombin. Power Doppler sonogram shows thin crescent of flow (arrow ) about peripheral aspect of partially thrombosed pseudoaneurysm (arrowheads). Sonographically guided compression was performed for 1 min and resulted in complete thrombosis. Second injection of thrombin was not performed. Follow-up color Doppler sonogram (not shown) showed complete pseudoaneurysm thrombosis. Procedure Success Failure % Successful First injection Second injection Overall outcome a AJR:177, August 2001

5 Thrombin Injection of Femoral Pseudoaneurysms A Fig year-old man with groin pseudoaneurysm after coronary angioplasty. A, Transverse color Doppler sonogram shows 3 3 cm pseudoaneurysm. Two white lines (arrows) represent anticipated path of needle (using attachable biopsy guide). B, Transverse color Doppler sonogram obtained immediately after injection of 600 U of thrombin shows that pseudoaneurysm thrombosed completely. However, persistent flow was identified in pseudoaneurysm neck (arrow ). This persistent flow was not treated with second injection of thrombin. C, Transverse color Doppler sonogram of groin obtained 1 day after thrombin injection shows thrombosis of pseudoaneurysm neck (arrow ). A B C B Fig year-old woman with pulsatile mass at right groin puncture site. A, Color Doppler sonogram shows right groin pseudoaneurysm that was subsequently successfully treated with 100 U of thrombin. Two white lines represent anticipated path of needle. B, Color Doppler sonogram obtained after patient returned to clinic 7 days later with pain, erythema, and tenderness at puncture site shows fluid collection (arrows) at site of treated pseudoaneurysm. Subsequent incision and drainage revealed purulent material containing Staphylococcus aureus. AJR:177, August

6 Paulson et al. 8 mm long and one 5 mm long. One of the four patients whose procedure failed had no further treatment or imaging studies. Seventy of the 103 patients with initial success had follow-up groin sonography performed hr later. No pseudoaneurysm recurrence was seen on follow-up sonograms. Of the 103 patients in whom the pseudoaneurysm lumen was completely thrombosed, persistent flow in the neck of the pseudoaneurysm occurred in 32 patients (Fig. 4). In 24 of these patients, the neck was found to be thrombosed on follow-up groin sonography performed 24 hr after the procedure. In the remaining eight patients, residual flow occurred in the neck, but the pseudoaneurysm did not recur. No additional treatment was performed on these patients. Twenty-four of the patients who underwent thrombin injection were receiving antithrombotic therapy at the time of the injection. Twenty-two were receiving heparin, and two were receiving warfarin. All 24 patients were successfully treated with a single thrombin injection. One patient required 1 min of supplemental compression after the thrombin injection. Four potential complications occurred. One patient who had an uneventful and successful thrombin injection returned to the clinic 7 days later with pain, tenderness, and erythema at the thrombin injection site. Groin sonograms showed a fluid collection at the site of the thrombosed pseudoaneurysm; the collection was treated with an incision and drainage of purulent material containing Staphylococcus aureus (Fig. 5). A second patient had a pseudoaneurysm that failed to thrombose after a single thrombin injection. The next morning this patient was noted to have a cold blue great toe with diminished capillary refill. The femoral, popliteal, dorsalis pedis, and posterior tibialis artery pulsations were intact and unchanged. The blue toe resolved spontaneously later that day. Although this patient s pseudoaneurysm required surgical repair, no specific diagnostic imaging or intervention was performed for the presumed embolus to the digital arteries of the great toe. A third patient who had a successful thrombin injection complained of crampy buttock and thigh pain immediately after the procedure. This pain lasted approximately 15 min and resolved spontaneously without further intervention. The cause of the pain was unclear but might have been arterial spasm. Peripheral pulses were intact and unchanged during this period of pain. A fourth patient had a cool leg and foot with delayed capillary refill immediately after a successful thrombin injection. In addition, there was a decrease in amplitude of the dorsalis pedis and posterior tibialis artery pulsation. The patient was otherwise asymptomatic. This patient was watched conservatively, and the cool leg resolved spontaneously over the next 4 hr. The amplitude of her peripheral pulses returned to baseline, and no specific intervention was required. No patient had an anaphylactic reaction to thrombin. During the hospitalization after the thrombin injection, no rash, hives, or wheezing to indicate an allergic reaction was reported. No patient had clinical evidence of a systemic coagulopathic or thrombotic complication after the injection of thrombin. However, we did not specifically test for the formation of antibodies to bovine products or coagulation factor V. Thirteen patients underwent injection of a human-derived thrombin preparation instead of the bovine product. Ten of these patients had a single successful thrombin injection. Three patients pseudoaneurysms failed to thrombose after the first injection. In two of these patients, the second injection was successful; in one, the second injection failed. This patient underwent surgical repair. The results of these 13 patients are included in the overall results described previously. Discussion The results of this consecutive series corroborate prior reports that indicate percutaneous injection of thrombin using sonographic guidance is an effective and safe therapy for the treatment of iatrogenic femoral pseudoaneurysms. Our overall success rate of 96% is similar to that in other reports, as detailed in Table 4 [17 21]. The advantages of thrombin injection for the treatment of iatrogenic femoral pseudoaneurysm are all the more impressive when compared with the limitations of sonographically guided compression repair, which at our institution has a success rate of 74% [22]. Compared with compression repair, thrombin is effective, efficient, and well tolerated [22]. The technique has been shown to be effective for TABLE 4 Note. Numbers in parentheses are percentages. pseudoaneurysms that cannot be compressed (for reasons such as size or location above the inguinal ligament) or that fail to thrombose with compression (because of systemic anticoagulation or other factors) [17 22]. In our experience, 10% of pseudoaneurysms failed to thrombose after the first thrombin injection. This initial failure rate is greater than in prior reports [17 21]. For those patients whose first attempt fails, we schedule a second thrombin attempt the next day. This approach assumes a clinically stable groin without evidence of rupture or expansion. In the subset of patients whose first attempt fails, the chance is better than 50% that the second procedure will result in pseudoaneurysm thrombosis. If the second procedure fails, we refer patients to a vascular surgeon for operative repair. The reasons for the failures are not certain, although we suspect the arterial tears in the patients whose thrombin injection fails are larger or more complicated than in the patients whose injections are successful [21]. Indeed, in two of the four patients whose second thrombin injection attempt failed, operative reports described arterial rents of 5 and 8 mm in length, rather than simple arteriotomy puncture wounds. It is feasible that pseudoaneurysms resulting from such arterial rents will be more resistant to repair. This technique is reserved for the stable iatrogenic femoral pseudoaneurysm. In our opinion, prompt surgical repair is mandated in pseudoaneurysms associated with active thigh bleeding from rupture, skin ischemia, nerve compression, threatened extremity, or infection. To date, our experience has been limited to iatrogenic femoral pseudoaneurysms. We have not tested the technique in pseudoaneurysms resulting from vascular surgery or orthopedic trauma, or visceral or mesenteric pseudoaneurysms. However, Kang et al. [19] reported that thrombin injection is successful for the repair of pseudoaneurysms at sites other than the femoral artery, including the Published Results of Thrombin Injection for Pseudoaneurysm Repair Study Year No. of Patients Overall Success Complications Kang et al. [19] (98) 1 (1) Tamim et al. [17] (100) 0 (0) Brophy et al. [20] (100) 0 (0) Lennox et al. [18] (100) 0 (0) La Perna et al. [21] (94) 1 (1) This study (96) 4 (4) Total (97) 6 (2) 314 AJR:177, August 2001

7 Thrombin Injection of Femoral Pseudoaneurysms brachial, radial, subclavian, posterior tibial, and distal superficial femoral arteries. Others have reported success in the treatment of nonfemoral pseudoaneurysms using percutaneous injection of fibrin adhesive (which contains thrombin) after balloon occlusion of the aneurysm neck [23]. Van den Berg et al. [24] used percutaneous injection of thrombin under CT guidance to treat an endoleak after the endovascular repair of an abdominal aortic aneurysm. The complication rate of our technique is low. The most serious complication is downstream artery embolization, but our data indicate that the rate of this event is low, approximately 2%. Presumably, once thrombin is injected, thrombus formation occurs quickly. In most cases, the enlarging semisolid thrombus becomes trapped in the pseudoaneurysm lumen, preventing the escape of pure thrombin. Nevertheless, we had two episodes after thrombin injection that could have been the result of downstream embolization, both of which resolved spontaneously. The possibility of this complication emphasizes the necessity of vascular radiology and surgical coverage when these procedures are performed. Although downstream embolization is uncommon, it may well be that some thrombin does in fact escape the pseudoaneurysm lumen and pass into the artery and systemic circulation. The small clots that may result seem to be asymptomatic in our experience, presumably lysed spontaneously by the lytic agents in circulating unclotted blood. To our knowledge, no prior report has postulated that an abscess developed as a complication of thrombin injection. Our case in which a groin abscess developed underscores the necessity of careful attention to sterile technique during these procedures. In our case, however, it is unclear whether bacteria were introduced into the thrombosed pseudoaneurysm during the thrombin injection or during the original femoral puncture or sheath placement. Our work corroborates previous investigations indicating that thrombin injection is effective in patients who are receiving antithrombotic therapy with heparin or warfarin [13, 18 22]. The effectiveness of this technique in the face of systemic anticoagulation is an additional advantage over compression, which is less effective in this setting [11]. Further, thrombin injection is effective in the setting of antiplatelet therapy with aspirin or ticlopidine hydrochloride [18, 20, 21]. Bovine thrombin is a foreign substance, and as such, may induce an allergic reaction after repeated exposures. Indeed, Pope and Johnston [25] describe a 50-year-old man who had anaphylaxis 2 min after an injection of bovine thrombin. Treatment required intubation, ventilation, epinephrine, IV fluids, corticosteroids, and 2 days of hospitalization. This particular patient was undergoing hemodialysis for renal failure and had repeated prior exposures to topical bovine thrombin to provide hemostasis at the dialysis puncture site, leading to sensitization. Pope and Johnston recommend that patients with a history of repeated exposure to bovine thrombin undergo a skin prick test with a thrombin solution before thrombin injection. In addition, patients who receive injections of bovine thrombin can develop antibodies to bovine proteins, including coagulation factor V, which may cross react with human coagulation factor V, leading to abnormalities in hemostasis [26, 27]. Given that bovine thrombin has been widely used as a topical agent and spray after cardiac and vascular surgery, some patients who present with a pseudoaneurysm as a complication of a cardiac catheterization may have developed antibodies to bovine proteins. Work by Tadokoro et al. [28] indicates that antithrombin IgE titers are elevated in patients with anaphylaxis after repeated topical applications of thrombin. Apparently the antibodies are directed toward contaminant bovine proteins rather than the thrombin itself. The United States Food and Drug Administration has approved a human-derived biologic product called fibrin sealant for use as a hemostatic agent [26]. The fibrin sealant kit consists of a suspension of fibrinogen and thrombin. Theoretically, use of the human product should decrease the possibility of an allergic reaction. Although our experience with the human product was limited to only 13 patients, the human product was similar in effectiveness to the bovine product. However, the fibrin sealant kit is considerably more expensive than the bovine product. Further studies will be required to assess the cost-effectiveness of the human product relative to the bovine product. In addition, some investigators have reported success by injecting autologous human thrombin into femoral pseudoaneurysms [29]. The autologous thrombin is derived from autologous patient blood under sterile conditions. In conclusion, for the treatment of iatrogenic femoral pseudoaneurysms, thrombin injection under sonographic guidance is a quick and effective method of therapy. Failures and complications are rare. In our institution, sonographically guided thrombin injection has replaced compression repair. References 1. Hessel SJ, Adams DF, Abrams HL. Complications of angiography. Radiology 1981;138: Lumsden AB, Miller JM, Kosinski AS, et al. A prospective evaluation of surgically treated groin complications following percutaneous cardiac procedures. 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