1 - University of Melbourne

not exanguinated during the time that thegraft is becoming water-tight. Even todaythere is active discussion regarding therelative merits of these various types ofarterial replacement and the general opinionis that arterial homografts, venous autografts,and synthetic prostheses all have aplace in the management of vasculardisease.Paralleling the development in materialsused for arterial replacement, there havebeen developments in the techniques usedin inserting these various substances intothe body. The treatment of aneurysms ofthe major vessels is relatively standardisedand, in general, consists of excision of thediseased vessel and replacement with anarterial prosthesis. If, however, an attemptis made to remove a blocked vessel thereare other factors which must be considered.At first sight, simple excision and replacementwould seem the appropriate methodof treatment. However, the occluded segmentis often of considerable length andwhen blockage occurs in a major vessel theoccluded segment is by-passed by the enlargementof collateral vessels. In anoperation designed to excise this segment,the collateral vessels are inevitably damagedand thus the blood supply to the distaltissues is still further reduced. Under thesecircumstances, should the implanted graftfail, the most disastrous results may follow:the limb may die, making a major amputationinevitable. These problems havebeen overcome to a large extent by the useof the by-pass technique. In this technique,the surgeon imitates nature and inserts along, wide "collateral" vessel to bridge overthe block in the host artery. The hostartery is exposed above the block, and theby-pass graft sewn in; the graft is insertedblindly down beside the main vessel in sucha way that the collateral vessels are notkdamaged and is resewn to the host vessel°elow the graft.When dealing with blockages of the mainvessels such as the aorta and its majorbranches it has been shown that excision ofthe media and diseased intima, togetherwith the occluding thrombus, leaving justthe adventitia intact, results in a tube capableof carrying blood. This operation,known by the complicated name of Dis-Obliterative Endarterectomy, is suitable onlyfor large arteries.SPECULUM 1961Thus it can be seen that at present, thesurgery of the major vessels is well established.In clinical practice it is possible toanastomose vessels ranging in size from theaorta and pulmonary artery down to vesselsof the brachial and popliteal size. Whilstin the experimental animal it is technicallyfeasible to join vessels of smaller size thanthe brachial, such procedures are rarelyindicated in clinical practice where pathologicalchanges in the vessel wall makesatisfactory junction of such small vesselsimpossible. Having considered the plumbingtechniques available to the vascular surgeon,let us now turn to a brief discussionon the types of disease with which he becomesinvolved.DISEASE INVOLVING THELOWER LIMBSOne of the common areas to be involvedby vascular disease is the lower limbs andin this area the effects produced by thereduction in blood supply vary with the siteof the obstruction and the rate at which thatobstruction develops. In a vessel affectedby atheroma, the diameter of the vessel progressivelynarrows and this reduces itsability to transmit blood. This is essentiallya gradual process, but, at, any stage duringthe evolution of the atheromatous plaque,the blood flowing within the artery may cloton the surface of the plaque and producea sudden occlusion of the vessel. As theavailability of blood for the tissues suppliedby the diseased artery diminishes the patientmay fmd that, whilst the blood flow is sufficientto meet the demands of the tissue atrest, it is insufficient to supply enough bloodto the active muscles during exercise. Thus,during exercise, metabolites accumulatewithin the active muscle and pain is produced.In the early phases this pain maybe produced only after prolonged activity,but, if the disease progresses, pain occurswith less and less activity until ultimatelythe patient is able to walk no more than afew yards. The muscles are not the onlytissues to feel the effect of this reduction inblood supply; the skin becomes thin, thehairs fall out, the subcutaneous tissueatrophies, and the whole limb becomes cold—this symptom may be a major complainton the part of the patient. Pain mayPAGE TWENTY-SEVEN