New prosthetic venous collar anastomotic technique: combining the best of other procedures.
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Anastomosis, Surgical↗
Biomedical subjects
M R Tyrrell
Publications and source records attributed to M R Tyrrell.
Evaluation of fine catheter aspiration cytology of the peritoneum as an adjunct to decision making in the acute abdomen.
Fine catheter aspiration cytology of the peritoneal cavity was performed successfully in 61 patients admitted with acute abdominal pain. Aspirates were examined microscopically and the percentage of neutrophils in the specimen counted. In patients in whom the clinical need for operation was certain (n = 25) all patients required surgery and the peritoneal neutrophil count was greater than 50 per cent. In patients in whom the clinical need for operation was uncertain (n = 36) 19 patients required operation: the peritoneal neutrophil count was greater than 50 per cent in 18 and in one patient with ectopic pregnancy fresh blood was aspirated. Of the 17 patients not requiring operation the peritoneal neutrophil count was less than 10 per cent in 15 and greater than 50 per cent in two patients (both had acute pelvic inflammatory disease). This study confirms peritoneal cytology as a useful adjunct to decision making in those patients with acute abdominal pain in whom the decision to operate is in doubt.
Abdomen, Acute↗
Graft stenosis: justification for 1-year surveillance.
In all, 412 femorodistal grafts (femoropopliteal and femorocrural), performed between 1984 and 1988, have been prospectively studied at 6 weeks and 3, 6, 9 and 12 months after operation and at intervals of 6 months thereafter by duplex scanning and intravenous digital subtraction angiography. The overall incidence of stenoses was 16 per cent (femorocrural 20 per cent, femoropopliteal 15 per cent). All stenoses were detected in the first year after operation and none occurred after this. Twenty-four non-haemodynamically significant stenoses were not treated but were followed at intervals of 3 months. Forty-two haemodynamically significant stenoses were detected and secondary procedures were performed in 30 grafts at a mean of 8 months after surgery. Thirteen had percutaneous balloon dilatation and six (46 per cent) remain patent at a mean follow-up of 22 months. Two grafts which occluded within 30 days and three which restenosed at a mean of 8 months had tertiary procedures. Seventeen grafts were surgically revised, nine with patch grafts and eight with bypass grafts. Eleven of these remain patent at a mean follow-up of 30 months. One occluded immediately and three occluded late. Two grafts which restenosed at a mean of 19 months had successful tertiary procedures. In total, seven grafts had tertiary procedures (two had balloon dilatation and five had surgery) and six of these remain patent at a mean follow-up of 13.5 months. In conclusion, 37 procedures have been performed on 30 grafts, of which 23 (77 per cent) remain patent at a mean follow-up of 12 months. Approximately one-quarter of femorodistal grafts will develop graft-related stenoses and graft surveillance is worthwhile, but only for the first year after operation.
Angiography, Digital Subtraction↗
Experimental evidence to support the use of interposition vein collars/patches in distal PTFE anastomoses.
We have conducted three in vitro experiments (using cadaver internal mammary artery as a model for crural artery), which establish the advantage of the Miller collar and Taylor patch over direct PTFE-artery anastomoses: (1) A new method of simultaneously measuring longitudinal and circumferential elasticity in human saphenous vein (n = 16) has demonstrated the latter to be anisotropic (i.e.: greater longitudinal than transverse compliance, P less than 0.002). This suggests that benefit may be gained by aligning the saphenous vein's longitudinal axis with that of the arteriotomy--a feature of both vein interposition anastomoses. (2) We have compared maximal pulsatile and constant flow across each type of anastomosis (n = 10 of each) using a flow model incorporating standard pressure, viscosity, graft and outflow vessel length, and anastomotic angle. This experiment has demonstrated loss of anastomotic reliability only in direct PTFE-artery anastomoses (i.e. no correlation between flow and vessel diameter, r = 0.04). (3) Casts of the internal anatomy of the anastomoses (n = 10 of each) have demonstrated a greater degree of oval distortion of the toe of the outflow vessel of direct PTFE-artery anastomoses than either of the other techniques (P less than 0.01). This experimental evidence suggests that both of these vein interposition techniques optimise the mechanical properties of saphenous vein and protect small arteries from anastomotic distortion. These benefits do not occur with direct PTFE-artery anastomoses.
Anastomosis, Surgical↗
Questionnaire identification of surgical patients at risk of HIV infection.
The prevalence of human immunodeficiency virus (HIV) infection is increasing. Risks of hospital transmission, though small, will consequently also increase. Precautions taken during invasive procedures, particularly surgery, and in the handling of specimens from patients diminish this risk. As HIV antibody screening is not permissible, we have assessed the possible efficacy of a routine questionnaire to identify high-risk groups. Of 525 questionnaires given to routine surgical patients, 506 (96%) were completed. Twenty-eight (5.5%) indicated that they were in a high-risk group. High-risk patients were more likely to present with anorectal disease, to be male and to be young compared with patients from the remainder of the sample. The questionnaire was acceptable to 97% of patients although to a significantly smaller number (82%) of high-risk patients. Routine HIV antibody testing would be acceptable to 88% of low-risk patients but to only 60% of high-risk patients. Questionnaire assessment is an acceptable and perhaps more reliable method of assessing HIV risk status than the other currently available options. It has to be accepted that it will never result in complete identification but we recommend this method as one approach to the problem faced by the surgical team.
Adolescent↗
The practical consequences of research in arteriosclerosis.
Despite the impressive volume of work that has been undertaken, the successful medical therapy of arteriosclerosis continues to elude us--preventive measures and surgical treatment of its complications persist as the primary modalities of treatment. While research into the fundamental pathophysiology surrounding arteriosclerosis is not complete and our understanding is plagued by the current plethora of confusing and contradictory reports, the cellular mechanisms underlying this process are gradually being clarified. As yet, this basic research has had limited impact for vascular surgical patients, who have benefited more as a result of epidemiological studies. For instance, we are more diligent in looking for occult disease, less ready to operate on obvious lesions, and more persuasive in our attempts to alter the patient's lifestyle--particularly smoking habits.
Arteriosclerosis↗
Is arterial reconstruction to the ankle worthwhile in the absence of autologous vein?
Autologous vein from either the arm or the leg is the preferred conduit for femoro-crural grafting. Limb salvage rates using prosthetic grafts have been sufficiently disappointing for many surgeons to consider primary amputation in the absence of suitable vein. We have attempted to improve prosthetic graft patency by the creation of a compliant, wide diameter vein collar at the distal anastomosis. Thirty patients with critical ischaemia (i.e.: rest pain with distal tissue loss or doppler ankle pressure less than 40 mmHg2.3) have undergone grafting to a crural vessel in the lower third of the calf using 6 mm externally supported PTFE (IMPRA) with a vein collar (17% of all lower calf grafts, 9% of all femoro-distal procedures). Five of the grafts occluded in the peri-operative period, resulting in major amputations. Another 4 grafts occluded within 12 months of operation resulting in amputation. A further 7 grafts have occluded but not required amputation. Fourteen (47%) grafts remain patent at a mean follow-up of 13.9 months (range 1-49) with a mean graft patency of 10 months. The aim of salvage surgery is to maintain independence until death supervenes. In this series 6 (20%) patients have died during follow-up and the best possible result in the 30 patients would have been a total of 417 "amputation avoided" months. In fact 300 "amputation avoided" months were achieved. Moreover, 21 legs (70%) have avoided amputation during the patient's lifetime, or at the most recent follow-up. These results suggest that femorocrural grafting using PTFE with a vein collar is worthwhile and preferable to primary amputation in the elderly patient.
Aged↗
Distal femoropopliteal bypass using a composite graft of PTFE and non-reversed saphenous vein.
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Blood Vessel Prosthesis↗
PTFE, collars, and patches.
The results of PTFE grafts to crural vessels have been sufficiently poor for some surgeons to consider primary amputation for critical ischemia in the absence of suitable lengths of autologous vein from arm or leg. However, the results of two anastomotic techniques using a short segment of interposed vein, are encouraging. We have attained 1-year patency rates of 74% (n = 72) using PTFE with the Taylor patch technique (personal communication) and 47% (n = 27) using PTFE with Miller collar anastomoses to distal crural vessels. To investigate the hemodynamic benefit of these techniques, they have been tested (using a pulsatile flow model incorporating standard pressure, viscosity, graft and vessel length, and anastomotic angle) against a standard end-to-side PTFE anastomosis to cadaver internal mammary artery. There was no significant difference in flow between the anastomotic methods. Downstream resistance was dictated by the diameter of the recipient vessel providing a vein interposition technique was used (r greater than .80), but this relationship was lost if a direct PTFE-arterial anastomosis was performed (r = .06), suggesting additional anastomotic resistance in the latter. This constitutes experimental evidence to suggest that direct PTFE-arterial anastomosis risks hemodynamically important technical errors, which are avoidable by the use of either the Miller collar or Taylor patch.
Anastomosis, Surgical↗
Deep vein thrombosis.
Deep vein thrombosis (DVT) is a common condition. Most cases arise as complications during the perioperative period. This can largely be prevented by adequate prophylaxis, principally using low-dose subcutaneous heparin. Only a minority of DVTs produce serious complications, but it is not currently possible to predict the clinical behaviour of any DVT, once formed. For this reason, any identified DVT should be vigorously treated. The mainstay of treatment remains systemic anticoagulation with heparin and then warfarin. Warfarin should be continued for 1 month in postoperative cases and 3 months in spontaneous cases, provided there is no ongoing predisposing factor. Recurrent spontaneous DVT formation is an indication for lifelong anticoagulation. Recent evidence suggests that the subcutaneous route of administration of heparin has advantage over traditional intravenous infusion. Some large DVTs require thrombolysis, and it is now possible to treat the underlying anatomical defects with angioplasty and endovascular stenting, although the long-term outcome of these procedures has not yet been established. For patients with contraindications to the use of anticoagulants, a variety of (temporary and permanent) percutaneously inserted vena caval filters are now available. The principal complications of DVT are pulmonary embolism, which may be fatal, and the development of a postphlebitic leg. The avoidance of these depends on adequate prophylaxis and vigorous treatment of the primary DVT.
Anticoagulants↗