- Email: [email protected]
Comparison of hemodynamic changes associated with two different polytetraflouroethylene arteriovenous fistulae in hemodialysis patients
Comparison of Hemodynamic Changes Associated With Two Different Polytetraflouroethylene Arteriovenous Fistulae In Hemodialysis Patients H. Karakayali, M.C. Yagmurdur, N.U. Tutar, O. Basaran, and M. Haberal ABSTRACT The aim of this prospective study was to identify hemodynamic factors associated with two different types of polytetrafluroethylene (PTFE) AV grafts. The study was conducted on 46 hemodialysis patients over a 3-year period. The subjects were randomly assigned to one of two study groups: Group 1 patients (n ⫽ 24) underwent a brachiocephalic loop PTFE fistula; Group 2 patients (n ⫽ 22), a brachioaxillary PTFE fistula. Preoperatively, we recorded each individual’s subclavian catheter history, hemodialysis frequency, and serum levels of parathormone (PTH), calcium (Ca)–phosphorus (P) product, homocysteine, protein C, and protein S. Doppler ultrasonography was used to evaluate vascular hemodynamic changes in the proximal and distal portions of the AV fistula at 48 hours and 1 week postoperatively. Group 1 showed a significantly greater number of ipsilateral subclavian catheter interventions prior to AV graft surgery than Group 2 (14 versus 7, respectively; P ⫽ .05; chi-square). The mean peak systolic velocity in the brachial artery in Group 1 was significantly higher than that in Group 2 at 1-week postoperatively (P ⫽ .04, paired t-test). The mean radial artery diameter in Group 1 was greater than that of Group 2 at 1 week postoperatively (P ⫽ .05, Student t-test). At 48 hours postoperatively the observed change in cephalic vein diameter in Group 1 was significantly greater than the change in axillary vein diameter in Group 2 (P ⫽ .08, paired t-test). Preoperatively, the mean serum protein C and protein S levels in Group 1 were higher than those in Group 2 (P ⫽ .03 and P ⫽ .04, respectively; Mann-Whitney U test). The total numbers of dialysis sessions per week in each group were significantly different (P ⫽ .001, chi-square). Six Group 1 patients exhibited graft thrombosis at 48 hours after AV graft surgery. None of the patients in Group 2 exhibited thrombosis at 48 hours or 1 week postoperatively. The results indicate that patients with brachiocephalic PTFE AV grafts show more significant changes in the cephalic vein and brachial artery than patients with brachioaxillary PTFE AV grafts. The findings also suggest that more ipsilateral subclavian catheter interventions and a higher weekly frequency of hemodialysis prior to AV graft surgery are risk factors for early thrombosis of PTFE AV grafts.
V
ASCULAR ACCESS is essential for hemodialysis. Although continuous ambulatory peritoneal dialysis catheters are becoming more common, vascular access failure remains an important cause of morbidity and a major contributor to hemodialysis cost in end-stage renal disease patients on hemodialysis.1,2 In many patients, problems with arterial or venous anatomy make it necessary for an arteriovenous (AV) shunt to be created using synthetic polytetrafluoroethylene (PTFE) graft material; however, thrombosis of PTFE AV grafts is a major cause of shunt
failure.3 Hemodynamic changes are some of the many known contributors to early graft thrombosis, but their relation to different shunt types has not been investigated in From the Baskent University Faculty of Medicine, Departments of General Surgery (H.K., M.C.Y., O.B., M.H.) and Radiology (N.U.T.), Ankara, Turkey. Address reprint requests to Mehmet Haberal, MD, FACS, President, Baskent University Faculty of Medicine, 1 cad. No: 77 Bahçelievler, 06490 Ankara, Turkey. E-mail: [email protected]
© 2004 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/04/$–see front matter doi:10.1016/j.transproceed.2004.09.028
Transplantation Proceedings, 36, 2603–2606 (2004)
2603
2604
KARAKAYALI, YAGMURDUR, TUTAR ET AL Table 1. Doppler Ultrasonography Findings Group 1 (n ⫽ 26) versus Group 2 (n ⫽ 22)
Parameters
Doppler findings PSV values of BA, UA, RA (cm/sec) BA PSV before surgery UA PSV before surgery RA PSV before surgery BA PSV at postoperative 48 hour UA PSV at postoperative 48 hour RA PSV at postoperative 48 hour BA PSV at postoperative 1 week UA PSV at postoperative 1 week RA PSV at postoperative 1 week Diameters (mm) BA diameter before surgery UA diameter before surgery RA diameter before surgery BA diameter at postoperative 48 hour UA diameter at postoperative 48 hour RA diameter at postoperative 48 hour BA diameter at postoperative 1 week UA diameter at postoperative 1 week RA diameter at postoperative 1 week
44 ⫾ 4 vs 43 ⫾ 3 40 ⫾ 4 vs 43 ⫾ 2 44 ⫾ 4 vs 45 ⫾ 3 135 ⫾ 14 vs 129 ⫾ 16 26 ⫾ 4 vs 25 ⫾ 4 41 ⫾ 8 vs 46 ⫾ 7 126 ⫾ 37 vs 54 ⫾ 7‡ 30 ⫾ 5 vs 28 ⫾ 4 54 ⫾ 15 vs 30 ⫾ 8 6.2 ⫾ 0.7 vs 5.2 ⫾ 0.4 2.1 ⫾ 0.1 vs 2.2 ⫾ 0.6 2.5 ⫾ 0.1 vs 2.4 ⫾ 0.2 5.2 ⫾ 0.2 vs 5.1 ⫾ 0.1 2.4 ⫾ 0.2 vs 2.3 ⫾ 0.2 3.1 ⫾ 0.2 vs 3.4 ⫾ 0.2 23 ⫾ 12 vs 38 ⫾ 11 5.5 ⫾ 3.1 vs 5.5 ⫾ 2.1 2.4 ⫾ 0.2 vs 1.4 ⫾ 0.1†
Abbreviations: PSV: Peak systolic velocity (cm/sec); BA, brachial artery; UA, ulnar artery; RA, radial artery. ‡ Significantly different values P ⫽ .04 (paired t-test). † Significantly different values P ⫽ .04 (Student t-test).
depth.4,5 The aim of this preliminary prospective study was to identify hemodynamic factors associated with two different PTFE AV grafts, namely, brachiocephalic versus brachioaxillary types. PATIENTS AND METHOD The study was conducted on 46 hemodialysis patients over a 3-year period. Patients who underwent kidney transplantation were excluded. Subjects were randomly assigned to one of two study groups: Group 1 patients (n ⫽ 24) underwent a brachiocephalic loop PTFE graft, and Group 2 (n ⫽ 22) a brachioaxillary PTFE grafts. Preoperatively, we recorded each individual’s demographic characteristics, etiology of renal failure, subclavian catheter history, hemodialysis frequency, and serum levels of parathormone (PTH), calcium (Ca)–phosphorus (P) product, homocysteine, cholesterol, protein C, and protein S. The group means for each parameter were compared. A preoperative venographic examination was also performed in each case to exclude vascular anomalies that might affect the success of an AV graft. The length and diameter of the PTFE were measured intraoperatively. Doppler ultrasonography was used to evaluate hemodynamic changes in the vessels at the proximal and distal portions of the AV graft at 48 hours and 1 week postoperatively. Mann-Whitney U and paired sample tests were employed for statistical analysis, with P ⬍ .05 values accepted as significant.
RESULTS
Group 1 included 16 (75%) women and 8 (25%) men of mean age 45 ⫾ 12 years (range, 21 to 69 years). Group 2 included 15 (68%) men and 7 (32%) women of mean age 41 ⫾ 13 years (range, 23 to 75 years). In Group 1, 15 patients underwent hemodialysis three times weekly, 7
patients, twice weekly; and 4 patients, once a week (group total: 63 sessions per week). In Group 2, 17 patients underwent hemodialysis twice weekly, and 5, once a week (group total: 39 sessions per week). The total number of dialysis sessions per week in Group 1 was significantly greater in Group 2 (P ⫽ .001, chi-square). With respect to blood chemistry findings in Groups 1 and 2, the preoperative serum levels of PTH (291 versus 270 pg/mL, respectively), Ca–P product (9.1 to 4.2 versus 8.8 to 4.5 mg/dL, respectively), and homocysteine (14 versus 16 mol/L, respectively) were similar (P ⬎ .05 for all; Mann-Whitney U test). The respective preoperative results for mean serum protein C (125% versus 99%; P ⫽ .03), and protein S levels (119% versus 93%; P ⫽ .04) showed significantly higher levels in Group 1. The two groups had similar flow rates through the proximal and distal portions of the PTFE grafts at both 48 hours and 1 week postoperatively. At 48 hours postoperatively, the observed change in cephalic vein diameter in Group 1 was significantly greater than the change in axillary vein diameter in Group 2 (P ⫽ .08, paired t-test). At 1 week postoperatively, the mean peak systolic velocity in the brachial artery in Group 1 was significantly higher than that in Group 2 (126 versus 54 cm/sec, respectively; P ⫽ .04, paired t-test Table 1). At 1 week postoperatively, the mean radial artery diameter in Group 1 was greater than that in Group 2 (2.4 versus 1.0 cm, respectively; P ⫽ .04, Student t-test, Table 1). Group 1 had experienced a significantly greater number of ipsilateral subclavian catheter interventions prior to AV fistula surgery than Group 2 (17 versus 7,
HEMODYNAMIC CHANGES
respectively; P ⫽ .05; chi-square). Six (23%) Group 1 patients exhibited graft thrombosis at 48 hours after AV fistula surgery. None of the patients in Group 2 exhibited fistula thrombosis at 48 hours or 1 week postoperatively. No patient showed a clinical sign or complaint that could be attributed to the hemodynamic changes detected by Doppler ultrasonography. DISCUSSION
Transplantation is the definitive treatment for end-stage renal disease, but many countries face a serious shortage of cadaveric organs. Hemodialysis enables patients with chronic renal failure to survive years on waiting lists. Dialysis requires vascular access, but its long duration and other hemodialysis-related issues often lead to complications that cause access site failures, is part due to some patients undergoing thousands of punctures at the same access site.6 When there is a problem with a patient’s arterial or venous anatomy, it is often necessary to create an AV fistula using a PTFE graft.7,8 For a PTFE AV graft to function properly, there must be adequate venous outflow. In most cases of AV with PTFE, central venous obstruction in the upper extremity is a consequence of previous subclavian catheter interventions. This obstruction may cause dysfunction of a PTFE AV graft.9 –11 We believe that this explains the higher rate of early thrombosis that we observed in Group 1 (brachiocephalic loop graft) patients, since they had undergone more ipsilateral subclavian catheter interventions prior to AV surgery than Group 2 (brachioaxillary graft) patients. Although each of the study subjects underwent preoperative venography to exclude patients with vascular anomalies that might affect the success of an AV graft, the multiple subclavian interventions in Group 1 may have caused hemodynamic disturbances undetectable on venography, an important finding for clinical practice. Subclavian interventions may be inevitable in cases of emergent hemodialysis for patients without venous access for effective hemodialysis. Multiple subclavian interventions may negatively affect blood flow, which is essential for the patency of the AV graft. In most cases, this problem occurs as a chronic complication of subclavian dialysis catheters used for temporary hemodialysis access.4,12 Previous research has suggested that hypercholesterolemia and hyperhomocysteinemia may be responsible for early thrombosis of PTFE AV grafts.13,14 We found no significant differences between the study groups with respect to serum homocysteine or cholesterol levels; however, we did observe significantly higher serum levels of protein C and of protein S in Group 1 versus Group 2, suggesting that these markers may be stronger predictors of early PTFE AV graft thrombosis than homocysteine or cholesterol. Some reports have discussed possible relationships between AV graft thrombosis and serum Ca–P and PTH levels. This issue has not been studied in depth. However, the serum Ca–P levels and PTH values in Group 1 versus Group 2
2605
showed no significant difference, although the small number of patients in this preliminary study demand broader analysis in layer cohorts. We observed similar postoperative PTFE graft flow rates in the two groups at both 48 hours and 1 week. However, the higher mean peak systolic velocity in the brachial artery of Group 1 may represent a barrier effect of the PTFE graft due to the anastomosis. In addition, we suspect that the greater postoperative mean radial artery diameter in Group 1 at 1 week postsurgery represents vascular compensation due to stenosis of PTFE AV graft. Based on the greater incidence of early graft thrombosis in Group 1, we conclude that increased mean peak systolic velocity can be considered a predictor of PTFE AV graft thrombosis, findings that are consistent with a previous reports.12 We also noted a significantly greater postoperative increase in axillary vein diameter at 48 hours in Group 1 compared to Group 2. We believe this may also reflect the compensatory vascular reaction to graft stenosis. Our results suggest that both the changes in vein diameter/mean peak systolic velocity and higher thrombosis rate are related to higher serum protein C and S levels, a finding that has also been noted previously.13 In conclusion, our findings in this preliminary study suggest that patients with brachiocephalic PTFE AV grafts show more significant changes in the veins and arteries directly related to the fistula than patients with brachioaxillary PTFE AV grafts. The results also suggest that a greater number of ipsilateral subclavian catheter interventions and more weekly hemodialysis treatments prior to AV graft surgery are risk factors for early PTFE AV graft thrombosis. Also, brachioaxillary AV grafts with PTFE may be preferable for hemodialysis venous access among patients with a history of multiple subclavian catheter interventions. Additionally, in patients with higher serum protein C and S levels, AV grafts should not be delayed to avoid multiple subclavian interventions for hemodialysis. Also, if it is mandatory to use a PTFE graft for an AV graft the brachioaxillary procedure is preferable to a brachiocephalic one. REFERENCES 1. Marchi S, Falleti E, Giacomello R, et al: Risk factors for vascular disease and arterio-venous fistula dysfunction in hemodialysis patients. J Am Soc Nephrol 7:1169, 1996 2. Basaran O, Moray G, Yagmurdur MC, et al: Six years of surgical experience with continious ambulatory peritoneal dialysis at one center. Transplant Proc 34:2039, 2002 3. Braden JM, Burgess ED, Parsons HG, et al: Hyperhomocysteinemia, anticardiolipin antibody status, and risk for vascular access thrombosis in hemodialysis patients. Kidney Int 55:315, 1999 4. Schwab SJ: Assessing the adequacy of vascular access and it’s relationship to patient outcome. Am J Kidney Dis 24:316, 1994 5. Fan J, Schwab SJ: Vascular access: concepts for the 1990’s. J Am Soc Nephrol 3:1, 1992 6. Moray G, Karakayali H, Kaya S, et al: Experience with arteriovenous fistulae for hemodialysis. Transplant Proc 28:2341, 1996 7. Culp K, Flanigan M, Taylor L, et al: Vascular access thrombosis in new hemodialysis patients. Am J Kidney Dis 26:341, 1995
2606 8. Quinton W, Dillard D, Scribner BH: Treatment of chronic renal failure by prolonged peritoneal dialysis. N Engl J Med 274:248, 1966 9. Haberal M, Oner Z, Cakmakci M: Progress in Artificial Organs. Cleveland, OH: ISAO Press; 1986, p 1071 10. Coskun M, Boyvat F, Kurt A, et al: Percutanous balloon angioplasty for permenant hemodialysis with direct arteriovenous fistulae. Transplant Proc 30:816, 1998 11. Woods JD, Port FK, Orzol S, et al: Clinical and biochemical correlates of starting “daily” hemodialysis. Kidney Int 55:2467, 1999
KARAKAYALI, YAGMURDUR, TUTAR ET AL 12. Surrat R, Picus D, Hicks M, et al: The importance of preoperative evaluation of the subclavian vein in dialysis access planning. Am J Roentgenol AJR 156:623, 1991 13. Lai K, Yin JA, Yuen PMP, et al: Effect of hemodialysis on protein C, protein S and antithrombin III levels. Am J Kidney Dis 17:38, 1991 14. De Marchi S, Falleti E, Giocormello R, et al: Risk factors for vascular disease and arteriovenous fistula dysfunction in hemodialysis patients. J Am Soc Neph 7:1169, 1996
V
ASCULAR ACCESS is essential for hemodialysis. Although continuous ambulatory peritoneal dialysis catheters are becoming more common, vascular access failure remains an important cause of morbidity and a major contributor to hemodialysis cost in end-stage renal disease patients on hemodialysis.1,2 In many patients, problems with arterial or venous anatomy make it necessary for an arteriovenous (AV) shunt to be created using synthetic polytetrafluoroethylene (PTFE) graft material; however, thrombosis of PTFE AV grafts is a major cause of shunt
failure.3 Hemodynamic changes are some of the many known contributors to early graft thrombosis, but their relation to different shunt types has not been investigated in From the Baskent University Faculty of Medicine, Departments of General Surgery (H.K., M.C.Y., O.B., M.H.) and Radiology (N.U.T.), Ankara, Turkey. Address reprint requests to Mehmet Haberal, MD, FACS, President, Baskent University Faculty of Medicine, 1 cad. No: 77 Bahçelievler, 06490 Ankara, Turkey. E-mail: [email protected]
© 2004 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/04/$–see front matter doi:10.1016/j.transproceed.2004.09.028
Transplantation Proceedings, 36, 2603–2606 (2004)
2603
2604
KARAKAYALI, YAGMURDUR, TUTAR ET AL Table 1. Doppler Ultrasonography Findings Group 1 (n ⫽ 26) versus Group 2 (n ⫽ 22)
Parameters
Doppler findings PSV values of BA, UA, RA (cm/sec) BA PSV before surgery UA PSV before surgery RA PSV before surgery BA PSV at postoperative 48 hour UA PSV at postoperative 48 hour RA PSV at postoperative 48 hour BA PSV at postoperative 1 week UA PSV at postoperative 1 week RA PSV at postoperative 1 week Diameters (mm) BA diameter before surgery UA diameter before surgery RA diameter before surgery BA diameter at postoperative 48 hour UA diameter at postoperative 48 hour RA diameter at postoperative 48 hour BA diameter at postoperative 1 week UA diameter at postoperative 1 week RA diameter at postoperative 1 week
44 ⫾ 4 vs 43 ⫾ 3 40 ⫾ 4 vs 43 ⫾ 2 44 ⫾ 4 vs 45 ⫾ 3 135 ⫾ 14 vs 129 ⫾ 16 26 ⫾ 4 vs 25 ⫾ 4 41 ⫾ 8 vs 46 ⫾ 7 126 ⫾ 37 vs 54 ⫾ 7‡ 30 ⫾ 5 vs 28 ⫾ 4 54 ⫾ 15 vs 30 ⫾ 8 6.2 ⫾ 0.7 vs 5.2 ⫾ 0.4 2.1 ⫾ 0.1 vs 2.2 ⫾ 0.6 2.5 ⫾ 0.1 vs 2.4 ⫾ 0.2 5.2 ⫾ 0.2 vs 5.1 ⫾ 0.1 2.4 ⫾ 0.2 vs 2.3 ⫾ 0.2 3.1 ⫾ 0.2 vs 3.4 ⫾ 0.2 23 ⫾ 12 vs 38 ⫾ 11 5.5 ⫾ 3.1 vs 5.5 ⫾ 2.1 2.4 ⫾ 0.2 vs 1.4 ⫾ 0.1†
Abbreviations: PSV: Peak systolic velocity (cm/sec); BA, brachial artery; UA, ulnar artery; RA, radial artery. ‡ Significantly different values P ⫽ .04 (paired t-test). † Significantly different values P ⫽ .04 (Student t-test).
depth.4,5 The aim of this preliminary prospective study was to identify hemodynamic factors associated with two different PTFE AV grafts, namely, brachiocephalic versus brachioaxillary types. PATIENTS AND METHOD The study was conducted on 46 hemodialysis patients over a 3-year period. Patients who underwent kidney transplantation were excluded. Subjects were randomly assigned to one of two study groups: Group 1 patients (n ⫽ 24) underwent a brachiocephalic loop PTFE graft, and Group 2 (n ⫽ 22) a brachioaxillary PTFE grafts. Preoperatively, we recorded each individual’s demographic characteristics, etiology of renal failure, subclavian catheter history, hemodialysis frequency, and serum levels of parathormone (PTH), calcium (Ca)–phosphorus (P) product, homocysteine, cholesterol, protein C, and protein S. The group means for each parameter were compared. A preoperative venographic examination was also performed in each case to exclude vascular anomalies that might affect the success of an AV graft. The length and diameter of the PTFE were measured intraoperatively. Doppler ultrasonography was used to evaluate hemodynamic changes in the vessels at the proximal and distal portions of the AV graft at 48 hours and 1 week postoperatively. Mann-Whitney U and paired sample tests were employed for statistical analysis, with P ⬍ .05 values accepted as significant.
RESULTS
Group 1 included 16 (75%) women and 8 (25%) men of mean age 45 ⫾ 12 years (range, 21 to 69 years). Group 2 included 15 (68%) men and 7 (32%) women of mean age 41 ⫾ 13 years (range, 23 to 75 years). In Group 1, 15 patients underwent hemodialysis three times weekly, 7
patients, twice weekly; and 4 patients, once a week (group total: 63 sessions per week). In Group 2, 17 patients underwent hemodialysis twice weekly, and 5, once a week (group total: 39 sessions per week). The total number of dialysis sessions per week in Group 1 was significantly greater in Group 2 (P ⫽ .001, chi-square). With respect to blood chemistry findings in Groups 1 and 2, the preoperative serum levels of PTH (291 versus 270 pg/mL, respectively), Ca–P product (9.1 to 4.2 versus 8.8 to 4.5 mg/dL, respectively), and homocysteine (14 versus 16 mol/L, respectively) were similar (P ⬎ .05 for all; Mann-Whitney U test). The respective preoperative results for mean serum protein C (125% versus 99%; P ⫽ .03), and protein S levels (119% versus 93%; P ⫽ .04) showed significantly higher levels in Group 1. The two groups had similar flow rates through the proximal and distal portions of the PTFE grafts at both 48 hours and 1 week postoperatively. At 48 hours postoperatively, the observed change in cephalic vein diameter in Group 1 was significantly greater than the change in axillary vein diameter in Group 2 (P ⫽ .08, paired t-test). At 1 week postoperatively, the mean peak systolic velocity in the brachial artery in Group 1 was significantly higher than that in Group 2 (126 versus 54 cm/sec, respectively; P ⫽ .04, paired t-test Table 1). At 1 week postoperatively, the mean radial artery diameter in Group 1 was greater than that in Group 2 (2.4 versus 1.0 cm, respectively; P ⫽ .04, Student t-test, Table 1). Group 1 had experienced a significantly greater number of ipsilateral subclavian catheter interventions prior to AV fistula surgery than Group 2 (17 versus 7,
HEMODYNAMIC CHANGES
respectively; P ⫽ .05; chi-square). Six (23%) Group 1 patients exhibited graft thrombosis at 48 hours after AV fistula surgery. None of the patients in Group 2 exhibited fistula thrombosis at 48 hours or 1 week postoperatively. No patient showed a clinical sign or complaint that could be attributed to the hemodynamic changes detected by Doppler ultrasonography. DISCUSSION
Transplantation is the definitive treatment for end-stage renal disease, but many countries face a serious shortage of cadaveric organs. Hemodialysis enables patients with chronic renal failure to survive years on waiting lists. Dialysis requires vascular access, but its long duration and other hemodialysis-related issues often lead to complications that cause access site failures, is part due to some patients undergoing thousands of punctures at the same access site.6 When there is a problem with a patient’s arterial or venous anatomy, it is often necessary to create an AV fistula using a PTFE graft.7,8 For a PTFE AV graft to function properly, there must be adequate venous outflow. In most cases of AV with PTFE, central venous obstruction in the upper extremity is a consequence of previous subclavian catheter interventions. This obstruction may cause dysfunction of a PTFE AV graft.9 –11 We believe that this explains the higher rate of early thrombosis that we observed in Group 1 (brachiocephalic loop graft) patients, since they had undergone more ipsilateral subclavian catheter interventions prior to AV surgery than Group 2 (brachioaxillary graft) patients. Although each of the study subjects underwent preoperative venography to exclude patients with vascular anomalies that might affect the success of an AV graft, the multiple subclavian interventions in Group 1 may have caused hemodynamic disturbances undetectable on venography, an important finding for clinical practice. Subclavian interventions may be inevitable in cases of emergent hemodialysis for patients without venous access for effective hemodialysis. Multiple subclavian interventions may negatively affect blood flow, which is essential for the patency of the AV graft. In most cases, this problem occurs as a chronic complication of subclavian dialysis catheters used for temporary hemodialysis access.4,12 Previous research has suggested that hypercholesterolemia and hyperhomocysteinemia may be responsible for early thrombosis of PTFE AV grafts.13,14 We found no significant differences between the study groups with respect to serum homocysteine or cholesterol levels; however, we did observe significantly higher serum levels of protein C and of protein S in Group 1 versus Group 2, suggesting that these markers may be stronger predictors of early PTFE AV graft thrombosis than homocysteine or cholesterol. Some reports have discussed possible relationships between AV graft thrombosis and serum Ca–P and PTH levels. This issue has not been studied in depth. However, the serum Ca–P levels and PTH values in Group 1 versus Group 2
2605
showed no significant difference, although the small number of patients in this preliminary study demand broader analysis in layer cohorts. We observed similar postoperative PTFE graft flow rates in the two groups at both 48 hours and 1 week. However, the higher mean peak systolic velocity in the brachial artery of Group 1 may represent a barrier effect of the PTFE graft due to the anastomosis. In addition, we suspect that the greater postoperative mean radial artery diameter in Group 1 at 1 week postsurgery represents vascular compensation due to stenosis of PTFE AV graft. Based on the greater incidence of early graft thrombosis in Group 1, we conclude that increased mean peak systolic velocity can be considered a predictor of PTFE AV graft thrombosis, findings that are consistent with a previous reports.12 We also noted a significantly greater postoperative increase in axillary vein diameter at 48 hours in Group 1 compared to Group 2. We believe this may also reflect the compensatory vascular reaction to graft stenosis. Our results suggest that both the changes in vein diameter/mean peak systolic velocity and higher thrombosis rate are related to higher serum protein C and S levels, a finding that has also been noted previously.13 In conclusion, our findings in this preliminary study suggest that patients with brachiocephalic PTFE AV grafts show more significant changes in the veins and arteries directly related to the fistula than patients with brachioaxillary PTFE AV grafts. The results also suggest that a greater number of ipsilateral subclavian catheter interventions and more weekly hemodialysis treatments prior to AV graft surgery are risk factors for early PTFE AV graft thrombosis. Also, brachioaxillary AV grafts with PTFE may be preferable for hemodialysis venous access among patients with a history of multiple subclavian catheter interventions. Additionally, in patients with higher serum protein C and S levels, AV grafts should not be delayed to avoid multiple subclavian interventions for hemodialysis. Also, if it is mandatory to use a PTFE graft for an AV graft the brachioaxillary procedure is preferable to a brachiocephalic one. REFERENCES 1. Marchi S, Falleti E, Giacomello R, et al: Risk factors for vascular disease and arterio-venous fistula dysfunction in hemodialysis patients. J Am Soc Nephrol 7:1169, 1996 2. Basaran O, Moray G, Yagmurdur MC, et al: Six years of surgical experience with continious ambulatory peritoneal dialysis at one center. Transplant Proc 34:2039, 2002 3. Braden JM, Burgess ED, Parsons HG, et al: Hyperhomocysteinemia, anticardiolipin antibody status, and risk for vascular access thrombosis in hemodialysis patients. Kidney Int 55:315, 1999 4. Schwab SJ: Assessing the adequacy of vascular access and it’s relationship to patient outcome. Am J Kidney Dis 24:316, 1994 5. Fan J, Schwab SJ: Vascular access: concepts for the 1990’s. J Am Soc Nephrol 3:1, 1992 6. Moray G, Karakayali H, Kaya S, et al: Experience with arteriovenous fistulae for hemodialysis. Transplant Proc 28:2341, 1996 7. Culp K, Flanigan M, Taylor L, et al: Vascular access thrombosis in new hemodialysis patients. Am J Kidney Dis 26:341, 1995
2606 8. Quinton W, Dillard D, Scribner BH: Treatment of chronic renal failure by prolonged peritoneal dialysis. N Engl J Med 274:248, 1966 9. Haberal M, Oner Z, Cakmakci M: Progress in Artificial Organs. Cleveland, OH: ISAO Press; 1986, p 1071 10. Coskun M, Boyvat F, Kurt A, et al: Percutanous balloon angioplasty for permenant hemodialysis with direct arteriovenous fistulae. Transplant Proc 30:816, 1998 11. Woods JD, Port FK, Orzol S, et al: Clinical and biochemical correlates of starting “daily” hemodialysis. Kidney Int 55:2467, 1999
KARAKAYALI, YAGMURDUR, TUTAR ET AL 12. Surrat R, Picus D, Hicks M, et al: The importance of preoperative evaluation of the subclavian vein in dialysis access planning. Am J Roentgenol AJR 156:623, 1991 13. Lai K, Yin JA, Yuen PMP, et al: Effect of hemodialysis on protein C, protein S and antithrombin III levels. Am J Kidney Dis 17:38, 1991 14. De Marchi S, Falleti E, Giocormello R, et al: Risk factors for vascular disease and arteriovenous fistula dysfunction in hemodialysis patients. J Am Soc Neph 7:1169, 1996