EXPERIMENTAL
MICRO-ARTERIAL
GRAFTS
TO SMALL ARTERIES
By B. McC. O’BRIEN,BSc., M.D., M.S., F.R.C.S., F.R.A.C.S., F.A.C.S., F. S. C. BROWNING, F.R.C.S. and P. ROSEN,F.R.A.C.S., F.R.A.C.O., D.O.(Melb.) Microsurgery Research Unit, St Vincent’s Hospital, Melbourne, Australia
CLINICALLY,the replacement of defects in small vessels, especially using venous grafts Sometimes from the volar aspect of the forearm, has become a common occurrence. dispensable small arteries can be used as a donor source. Experimental work by Yasargil (rg67), and later by Buncke and Murray (rg7r), showed microvascular grafts to be feasible. The latter authors reported a patency of I I out of 14 micro-arterial grafts in the femoral artery of rats, while Hunter and Donaghy (1973) reported a patency rate of 76 per cent in 25 arterial grafts in rabbits’ femoral arteries. In a series of experimental reversed arterial grafts carried out in our laboratory in 1970 in the femoral arteries of 28 rabbits, a patency rate of 67 per cent was obtained in 40 grafts. These grafts were explored at varying postoperative intervals (Table). The overall patency rate was assumed to be the same as for exploration at 7-10 days, although TABLE Micro-arterial grafts-Series Day explored
Number
I
Patency
o-7 O-21 22-35 36-84 118
16 4 IO 9 I
II
TOTAL
40
27
64 5 I
it has since been shown (Hayhurst and O’Brien, 1975) that anastomoses which are occluded early can become recanalised at a later date. Following further refinement of techniques and instruments, a series of 50 rabbit arterial grafts was undertaken, exploring the grafts in the 7-10 day period.
MATERIAL
AND
METHODS
Using the femoral artery as a suitable sized vessel, the grafts were performed by the following technique. The femoral artery, varying from I to 1.5 mm in diameter, was exposed and freely dissected over a distance of 3 cm, so that the graft anastomoses could be carried out under minimal tension at the suture line. A double adjustable clamp was applied to the vessels with the jaws about 1.5 cm apart. A I cm length of vessel was then removed Address for reprints: B. McC. O’Brien, Melbourne, Victoria 3065, Australia.
Director, 155
Microsurgery
Research
Unit, St Vincent’s
Hospital,
156
BRITISH JOURNAL OF PLASTIC SURGERY
using sharp scissors and the jaws were then approximated to take any tension off the segment to be regrafted. The graft was reversed to avoid any possibility of chance union of vasa vasorum. The vessel ends in the clamps and the graft were then carefully dilated with the forceps and irrigated with heparinised saline to remove any clots. The anastomosis was then carried out at proximal and distal ends of the graft, using IO/O Nylon on a BV2 needle. Using standard microvascular techniques, the proximal anastomosis was secured with several sutures before the distal anastomosis was commenced to equalise the tension on the vessel wall and avoid tearing; once the anterior aspect of the anastomoses had been performed the clamp was turned over and the posterior aspects of the graft ends completed. The vessel surface was then irrigated with normal saline to clear any remaining heparin. The distal clamp was released to allow sealing of the anastomoses before the proximal clamp was removed. On several occasions it was noted that spasm developed in the grafts while the vessel ends remained relaxed, but that this was easily reversed by the topical application of 1.2 per cent papaverine. A patency test beyond the distal anastomosis was carried out before closure of the skin wounds to demonstrate the primary patency. At 7 to IO days the grafts were explored and a patency test carried out to determine their adequacy. RESULTS In the original series of 45 grafts in 28 rabbits, 5 grafts were not included because of the death of the rabbits within 24 hours. Of the remaining 40 grafts, 27 were patent on exploration at postoperative intervals ranging from 1-118 days (Table). In the second series of 50 grafts involving 28 rabbits, 4 were not included in the series because of death of the rabbits within 24 hours, presumably due to anaesthetic causes. In the remainder, 42 were patent at exploration and 4 were occluded when explored between 7 and IO days. Of the 4 occluded anastomoses, 2 thrombosed at a damaged clamp site which had One was occluded for no apparent reason, while the fourth caused intimal disruption. was an anastomosis which had been repeated after release of the clamps because I suture had caught the back wall and occluded the lumen. DISCUSSION In the second series of arterial grafts, a high patency rate was obtained by careful technique and avoidance of tension in the graft. It was found that in some of the earlier grafts in this series the clamps were applied too firmly to counteract the tension on the divided ends to prevent them slipping out; this, in turn, led to some intimal damage with failure of graft patency in 2 cases. This was later avoided by wider dissection and mobilisation of the femoral vessel allowing the clamps to be approximated more readily and distributing the tension over a longer length of vessel. One graft failed because the clamp was reapplied after the anastomoses had been carried out. It would appear that any stasis of blood near the suture lines increases the risk of thrombus formation, and preferably any adjustment of suture lines should be carried out while the blood is flowing. It can be seen, from our figure of gr per cent patency, that arterial grafts are as reliable as venous grafts and could be considered for clinical use when appropriate donor sites are available. This work is supported by a grant from the National Health and Medical Research Council of Australia.
EXPERIMENTAL
MICRO-ARTERIAL
GRAFTS
TO
SMALL
ARTERIES
REFERENCES BUNCKE,H. J. and MURRAY, D. E. (1971). Autogenous arterial interposition of grafts of less than I mm in external diameter in rats. Transactions of the Sixth International Congress of Plastic and Reconstructive Surgery, p. 572. London: Buttetworth. HAYHURST?J. W. and O’BRIEN, B. McC. (1975). Experimental study of microvascular techmque, patency rates and related factors. British Journal of Phric Surgery, 28, 128. HUNTER, K. M. and DONAGHY,R. M. (1973). Arterial micro-autografts : An experimental study. Canadian Journal of Surgery, 16, 23. YASARGIL,M. G. (1967). Experimental small vessel surgery in the dog including patching and grafting of cerebral vessels and the formation of functional extracranial shunts. In “Microvascular Surgery” , eds. R. P. M. Donaghy and M. G. Yarsargil, p. 87. St Louis: C. V. Mosby Co.
MICRO-ARTERIAL
GRAFTS
TO SMALL ARTERIES
By B. McC. O’BRIEN,BSc., M.D., M.S., F.R.C.S., F.R.A.C.S., F.A.C.S., F. S. C. BROWNING, F.R.C.S. and P. ROSEN,F.R.A.C.S., F.R.A.C.O., D.O.(Melb.) Microsurgery Research Unit, St Vincent’s Hospital, Melbourne, Australia
CLINICALLY,the replacement of defects in small vessels, especially using venous grafts Sometimes from the volar aspect of the forearm, has become a common occurrence. dispensable small arteries can be used as a donor source. Experimental work by Yasargil (rg67), and later by Buncke and Murray (rg7r), showed microvascular grafts to be feasible. The latter authors reported a patency of I I out of 14 micro-arterial grafts in the femoral artery of rats, while Hunter and Donaghy (1973) reported a patency rate of 76 per cent in 25 arterial grafts in rabbits’ femoral arteries. In a series of experimental reversed arterial grafts carried out in our laboratory in 1970 in the femoral arteries of 28 rabbits, a patency rate of 67 per cent was obtained in 40 grafts. These grafts were explored at varying postoperative intervals (Table). The overall patency rate was assumed to be the same as for exploration at 7-10 days, although TABLE Micro-arterial grafts-Series Day explored
Number
I
Patency
o-7 O-21 22-35 36-84 118
16 4 IO 9 I
II
TOTAL
40
27
64 5 I
it has since been shown (Hayhurst and O’Brien, 1975) that anastomoses which are occluded early can become recanalised at a later date. Following further refinement of techniques and instruments, a series of 50 rabbit arterial grafts was undertaken, exploring the grafts in the 7-10 day period.
MATERIAL
AND
METHODS
Using the femoral artery as a suitable sized vessel, the grafts were performed by the following technique. The femoral artery, varying from I to 1.5 mm in diameter, was exposed and freely dissected over a distance of 3 cm, so that the graft anastomoses could be carried out under minimal tension at the suture line. A double adjustable clamp was applied to the vessels with the jaws about 1.5 cm apart. A I cm length of vessel was then removed Address for reprints: B. McC. O’Brien, Melbourne, Victoria 3065, Australia.
Director, 155
Microsurgery
Research
Unit, St Vincent’s
Hospital,
156
BRITISH JOURNAL OF PLASTIC SURGERY
using sharp scissors and the jaws were then approximated to take any tension off the segment to be regrafted. The graft was reversed to avoid any possibility of chance union of vasa vasorum. The vessel ends in the clamps and the graft were then carefully dilated with the forceps and irrigated with heparinised saline to remove any clots. The anastomosis was then carried out at proximal and distal ends of the graft, using IO/O Nylon on a BV2 needle. Using standard microvascular techniques, the proximal anastomosis was secured with several sutures before the distal anastomosis was commenced to equalise the tension on the vessel wall and avoid tearing; once the anterior aspect of the anastomoses had been performed the clamp was turned over and the posterior aspects of the graft ends completed. The vessel surface was then irrigated with normal saline to clear any remaining heparin. The distal clamp was released to allow sealing of the anastomoses before the proximal clamp was removed. On several occasions it was noted that spasm developed in the grafts while the vessel ends remained relaxed, but that this was easily reversed by the topical application of 1.2 per cent papaverine. A patency test beyond the distal anastomosis was carried out before closure of the skin wounds to demonstrate the primary patency. At 7 to IO days the grafts were explored and a patency test carried out to determine their adequacy. RESULTS In the original series of 45 grafts in 28 rabbits, 5 grafts were not included because of the death of the rabbits within 24 hours. Of the remaining 40 grafts, 27 were patent on exploration at postoperative intervals ranging from 1-118 days (Table). In the second series of 50 grafts involving 28 rabbits, 4 were not included in the series because of death of the rabbits within 24 hours, presumably due to anaesthetic causes. In the remainder, 42 were patent at exploration and 4 were occluded when explored between 7 and IO days. Of the 4 occluded anastomoses, 2 thrombosed at a damaged clamp site which had One was occluded for no apparent reason, while the fourth caused intimal disruption. was an anastomosis which had been repeated after release of the clamps because I suture had caught the back wall and occluded the lumen. DISCUSSION In the second series of arterial grafts, a high patency rate was obtained by careful technique and avoidance of tension in the graft. It was found that in some of the earlier grafts in this series the clamps were applied too firmly to counteract the tension on the divided ends to prevent them slipping out; this, in turn, led to some intimal damage with failure of graft patency in 2 cases. This was later avoided by wider dissection and mobilisation of the femoral vessel allowing the clamps to be approximated more readily and distributing the tension over a longer length of vessel. One graft failed because the clamp was reapplied after the anastomoses had been carried out. It would appear that any stasis of blood near the suture lines increases the risk of thrombus formation, and preferably any adjustment of suture lines should be carried out while the blood is flowing. It can be seen, from our figure of gr per cent patency, that arterial grafts are as reliable as venous grafts and could be considered for clinical use when appropriate donor sites are available. This work is supported by a grant from the National Health and Medical Research Council of Australia.
EXPERIMENTAL
MICRO-ARTERIAL
GRAFTS
TO
SMALL
ARTERIES
REFERENCES BUNCKE,H. J. and MURRAY, D. E. (1971). Autogenous arterial interposition of grafts of less than I mm in external diameter in rats. Transactions of the Sixth International Congress of Plastic and Reconstructive Surgery, p. 572. London: Buttetworth. HAYHURST?J. W. and O’BRIEN, B. McC. (1975). Experimental study of microvascular techmque, patency rates and related factors. British Journal of Phric Surgery, 28, 128. HUNTER, K. M. and DONAGHY,R. M. (1973). Arterial micro-autografts : An experimental study. Canadian Journal of Surgery, 16, 23. YASARGIL,M. G. (1967). Experimental small vessel surgery in the dog including patching and grafting of cerebral vessels and the formation of functional extracranial shunts. In “Microvascular Surgery” , eds. R. P. M. Donaghy and M. G. Yarsargil, p. 87. St Louis: C. V. Mosby Co.
