426 BRITISH JOURNAL OF PLASTIC SURGERY

Absorbable sutures in microvascular anastomosis

A. M. AWWAD and D. A. FRENCH

Canniesbum Hospital, Bearsden, Glasgow and Ethicon Laboratories, Edinburgh

Absorbable sutures have obvious theoretical advantages in vascular anastomosis. These include the absence of permanent foreign bodies, a greater integrity in the healed anastomosis and no impedi- ment to growth in the younger patient. In spite of the successful use of catgut in vascular anastomosis reported by Aberdeen in the 196Os, absorbable sutures have not been used in vascular repair until the recent advent of synthetic absorbable material.

In this study 10/O nylon on a 75 micron needle was compared with monofilament polyglycolide- poly-lactide (Vicryl (R)) of the same gauge in anastomoses of the femoral arteries. The anasto-

mosis was made with nylon on one side and Vicryl (R) on the other. The anastomoses were examined microscopically at periods of 3, 8, 28 and 56 days and by light and scanning electron microscopy. Three of the 20 Vicryl (R) and one of the nylon anastomoses were wholly or partially thrombosed at post-mortem.

The histological results showed nylon and Vicryl (R) to be similar in the early stages of repair, (3 and 8 days), but suggested that absorbability especially with a low level of tissue reaction, confers advantages at the longer periods (28 and 56 days). Good neo-intimal surfaces were observed at the longer times with both sutures.

Haemodynamic changes in free flaps

A. M. AWWAD, J. H. EVANS and M. H. C. WEBSTER

Canniesbum Hospital, Bearsden, Glasgow and the Bio-Engineering Department, Strathclyde University, Glasgow

The purpose of this presentation is to discuss the difference in blood flow dynamics between free flaps and normal tissue, that occurs immediately after elevating a free flap.

Haemodynamics in a free flap (Awwad, 1982) are different from normal tissue in the following aspects:

(i) There is a drop in the arterial pressure in the flap.

(ii) There is a decrease in the absolute blood flow into the flap.

(iii) Blood flow changes in the feeding artery of the flap.

These differences may be due to the fact that when a free flap is elevated, all connecting blood vessels to the body are divided, except one artery and one vein which maintain the blood supply to the flap. This pattern of blood supply is different

from normal tissue in that, normally, there are extensive connections and anastomoses between blood vessels which exist in the form of arcades and loops at all levels of the circulation (Saunders et al., 1957). McGregor and Morgan (1973) have shown, by doing radiopaque intra-arterial injec- tion studies, per-operatively, that many areas of the human skin are potentially supplied by more than one source.

Saunders et al. (1957) suggested that the pres- ence of these vascular anastomoses and connec- tions between blood vessels in the form of arcades and loops, is in order to maintain and distribute pressure inside the vascular bed. It seems likely that interference with these arcades when a free flap is elevated may result in reducing intra-arterial pressure in the flap and the absolute blood flow into the flap. However, steady recovery is expected to occur as a result of development of new vascular

BRITISH MICROSURGICAL SOCIETY MEETING 1983 421

connections between the flap and its bed, which would ultimately restore the normal pattern of vascular architecture of the flap.

Changes in the blood flow through the feeding artery of the flap depend on the pre-existing flow and on the size of the vessel. For example, in the case of a small artery such as the superficial epigastric artery, the flow in that artery after elevating a flap based on it may increase by 228% (McKee et al., 1982). By contrast, blood flow into the radial artery drops to around 20% of its original flow after the forearm flap is elevated.

These changes in haemodynamics suggest that restoring the normal physiological arrangement of blood vessels in free flaps by connecting more than one feeding artery and perhaps more than one vein,

may maintain an absolute blood flow into the flap nearer to the normal level.

References Awwad, A. M. (1982). Effect of temperature on bloodflow in

island and free skin flaps. MSc Thesis, Strathclyde Univer- sity, Glasgow.

McGregor, 1. A. and Morgan, G. (1973). Axial and random pattern flaps. British Journal of Plastic Surgery, 26, 202.

McKee, N. H.. Clarke, H. M., Nigra, C. A. L. and Manktelow, R. T. (1982). A study of blood flow and pressure in the vessels supplying a free flap. Plastic and Reconstructive Surgery, 69, 68.

Saunders, R. L. de C. H., Lawrence, J., Maciver, R. C. N. and Nemethy, N. (1957). The anatomical basis of the peripheral circulation in man. In, Peripheral Circulation in Health and Disease. Editors: A. D. S. Redish and F. F. Tangco. New York: Grune and Stratton.