Correspondence
Late Bacteremic Graft Infection To the Editor: The recent report by Go6au-Brissonniere and coworkers [1] addresses the difficult problem of late bacteremic graft infection. That the rarity of this problem prevents adequate clinical study is unfortunately true. Reliance on animal studies is the only alternative, but it is not quite clear which animal model most closely imitates the human in this regard. In a recent investigation [2,3], we compared the infectability of Dacron aortic grafts in dogs and pigs. In our experiment, a predictable rate of infection occurred in dogs subjected to 102 to l0 s IV Staphylococcus aureus (IDs0 = 1029), but only random infections occurred in pigs at these doses. When radiolabelled bacteria (106) w e r e given intravenously to both species, pigs cleared the dose significantly faster than dogs. However, pigs cleared bacteria primarily in the lungs compared to liver/spleen clearance in dogs. This suggested to us that the rate of bloodstream clearance of bacteria
may be the most important factor in producing bacteremic graft infections. Thus, while it is important to rely on animal models when dealing with graft infections, it is also incumbent upon investigators to continue to learn more about their animal models and their similarities to humans. I look forward to further study on the problem from Dr. Go6au-Brissonni6re and his colleagues. Michael A. Ricci, MD Department of Surgery University of Vermont I. GOEAU-BRISSONIERE O, LEPORT C, LEBRAULT C, et al. Antibiotic prophylaxis of the late bacteremic vascular graft infection in a dog model. Ann Vasc Surg 1990;4:528-532. 2. RICCI MA, MEHRAN RJ, PETSIKAS D, et al. I. Species differences in the infectability of vascular grafts. J Invest Surg (in press), 1991. 3. RICCI MA, MEHRAN R, CHRISTON NV, et al. II. Species differences in the clearance of Staphylococcus aureus bacteremia. J Invest Surg (in press), 1991.
Standardized Reporting of Patency Rates To the Editor: In his comments [1] on our article "Preferential Use of ePTFE for Above-Knee Femoropopliteal B ypass Grafts" [2] Dr. Schulman disagrees with our method of reporting cumulative patency rates for the grafts studied. We have chosen to report our findings in accordance with the recommended standards proposed by the Ad Hoc Committee on Reporting Standards, Society for Vascular Surgery/ North American Chapter, International Society for Cardiovascular Surgery. They define cumulative patency as "the proportion of grafts remaining patent at the start of each interval" [3]. While we appreciate Dr. Schulman's careful reading of our article, we are certain he would agree that standardization of reporting is essential in the comparison of data from different trials and reviews. To further permit such comparisons, and to
mmm
311
allow critical reviews such as Dr. Schulman's, we have chosen to present our data in tabular form as well. I hope this clarifies any questions regarding our statistical methods. Robert B. Patterson, MD Division of Vascular Surgery, Naval Hospital Portsmouth Portsmouth, Virginia 1. SCHULMAN ML. Patency rates for AK femoropopliteal bypass (letter). Ann Vasc Surg 1991 ;5:103. 2. PATTERSON RB, FOWL RJ, KEMPCZINSKI RF, et al. Preferential use of ePTFE for above-knee femoropopliteal bypass grafts. Ann Vasc Surg 1990;4:338-343. 3. RUTHERFORD RB, FLANIGAN DP, GUPTA SK, et al. Suggested standards for reports dealing with lower extremity ischemia. J Vasc Surg 1986;4:80-94.
Late Bacteremic Graft Infection To the Editor: The recent report by Go6au-Brissonniere and coworkers [1] addresses the difficult problem of late bacteremic graft infection. That the rarity of this problem prevents adequate clinical study is unfortunately true. Reliance on animal studies is the only alternative, but it is not quite clear which animal model most closely imitates the human in this regard. In a recent investigation [2,3], we compared the infectability of Dacron aortic grafts in dogs and pigs. In our experiment, a predictable rate of infection occurred in dogs subjected to 102 to l0 s IV Staphylococcus aureus (IDs0 = 1029), but only random infections occurred in pigs at these doses. When radiolabelled bacteria (106) w e r e given intravenously to both species, pigs cleared the dose significantly faster than dogs. However, pigs cleared bacteria primarily in the lungs compared to liver/spleen clearance in dogs. This suggested to us that the rate of bloodstream clearance of bacteria
may be the most important factor in producing bacteremic graft infections. Thus, while it is important to rely on animal models when dealing with graft infections, it is also incumbent upon investigators to continue to learn more about their animal models and their similarities to humans. I look forward to further study on the problem from Dr. Go6au-Brissonni6re and his colleagues. Michael A. Ricci, MD Department of Surgery University of Vermont I. GOEAU-BRISSONIERE O, LEPORT C, LEBRAULT C, et al. Antibiotic prophylaxis of the late bacteremic vascular graft infection in a dog model. Ann Vasc Surg 1990;4:528-532. 2. RICCI MA, MEHRAN RJ, PETSIKAS D, et al. I. Species differences in the infectability of vascular grafts. J Invest Surg (in press), 1991. 3. RICCI MA, MEHRAN R, CHRISTON NV, et al. II. Species differences in the clearance of Staphylococcus aureus bacteremia. J Invest Surg (in press), 1991.
Standardized Reporting of Patency Rates To the Editor: In his comments [1] on our article "Preferential Use of ePTFE for Above-Knee Femoropopliteal B ypass Grafts" [2] Dr. Schulman disagrees with our method of reporting cumulative patency rates for the grafts studied. We have chosen to report our findings in accordance with the recommended standards proposed by the Ad Hoc Committee on Reporting Standards, Society for Vascular Surgery/ North American Chapter, International Society for Cardiovascular Surgery. They define cumulative patency as "the proportion of grafts remaining patent at the start of each interval" [3]. While we appreciate Dr. Schulman's careful reading of our article, we are certain he would agree that standardization of reporting is essential in the comparison of data from different trials and reviews. To further permit such comparisons, and to
mmm
311
allow critical reviews such as Dr. Schulman's, we have chosen to present our data in tabular form as well. I hope this clarifies any questions regarding our statistical methods. Robert B. Patterson, MD Division of Vascular Surgery, Naval Hospital Portsmouth Portsmouth, Virginia 1. SCHULMAN ML. Patency rates for AK femoropopliteal bypass (letter). Ann Vasc Surg 1991 ;5:103. 2. PATTERSON RB, FOWL RJ, KEMPCZINSKI RF, et al. Preferential use of ePTFE for above-knee femoropopliteal bypass grafts. Ann Vasc Surg 1990;4:338-343. 3. RUTHERFORD RB, FLANIGAN DP, GUPTA SK, et al. Suggested standards for reports dealing with lower extremity ischemia. J Vasc Surg 1986;4:80-94.
