Biomedical subjects
Publications and source records attributed to R M Greenhalgh.
Two cases of claudication of the cauda equina due to ischaemia secondary to distal aortic disease in the Small Aorta syndrome are reported. The association has not been previously reported and the appropriate management is discussed.
The purpose of this study was to establish whether women with peripheral arterial disease can be distinguished from controls on the basis of plasma lipid and apolipoprotein profiles. One group of patients with peripheral arterial disease (n = 20) was characterized by a localized aortic stenosis referred to as the 'small aorta syndrome' (SAS). The other group of patients with peripheral arterial disease (n = 23) had a diffuse segmental pattern of stenoses referred to as the 'stenosing peripheral arterial disease' (SPAD). After correcting for the effects of age and body mass index, the SAS group had elevated plasma total cholesterol (TC) levels when compared to normal controls (P less than or equal to 0.008), while the SPAD group had triacylglycerol (TG) levels different from controls (P = 0.02). Both groups of patients were characterized by reduced levels of apolipoprotein A-I (P less than or equal to 0.04) and increased levels of apolipoprotein C-III (P less than or equal to 0.002). Apolipoproteins B and E were also elevated in both groups of patients but not significantly. Mutivariate analyses indicated that the A-I/C-III ratio correctly discriminated 97.8% of the SAS and the A-I/C-III ratio plus A-I discriminated 89.8% of the SPAD patient from the controls. In addition, multivariate analyses showed that the variables age, TC/Apo B, Apo B/C-III and TG/C-III discriminated SPAD from SAS patients with a correct classification of 93.2%. Results of this study showed that the measurement of apolipoproteins A-I, B and C-III in conjunction with TC and TG is of potential use for differentiating patients with peripheral arterial disease from normal controls as well as for distinguishing patients with SAS from those with SPAD. It seems that particular patterns of peripheral arterial disease in women may be associated with slightly different alterations in the plasma lipoprotein system.
A preliminary subcutaneous dose of heparin given with premedication, followed by a continuous infusion of low-dose heparin up to 2 hours after operation, was given to 20 of 40 patients undergoing major abdominal operation randomly allocated to either act as controls or receive prophylaxis. The anticoagulant effect of heparin was determined by immunologic measurements of antithrombin III (AT III) and by assay of AT III and antifactor Xa activity on postoperative days 1 and 3. Despite lowered plasma AT III levels on postoperative day 3, the patients who had received low-dose heparin had significantly increased plasma antifactor Xa activity when compared with control patients (P less than 0.05). The incidences of thrombosis within 48 hours (early deep venous thrombosis) after operation were 9 of 20 control patients and 1 of 20 patients who received prophylaxis (P less than 0.01 by Fisher's exact test). Preoperative blood samples from another group of patients undergoing major abdominal operation were examined by the thromboelastograph saline dilution test, which has previously been shown to be a predictor of the risk of early deep vein thrombosis. The patients who were considered to be at high risk were treated with low-dose heparin as before, and the low-risk patients received no prophylaxis. The high-risk patients had lower levels of AT III before operation and before heparin administration than the low-risk patients and significantly lower levels on day 3 (P less than 0.02), whereas on day 3 the high-risk patients had significantly raised levels of plasma antifactor Xa. No patient in either group developed deep vein thrombosis within 48 hours of operation.
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An instrument for monitoring the blood flow in skin flaps by temperature measurement is described. This compares the temperature of the flap with adjacent normal skin. An experimental assessment of the technique is presented. Although many of the problems associated with absolute temperature measurement were eliminated, the reaction to circulatory change within a flap was slow. However, with further refinement, the principle may have a place in clinical practice, especially in replantation surgery.
A technique based on reflection spectrophotometry has been tested for use as a monitor of the cutaneous circulation in experimental skin flaps. A very rapid indication was given of either arterial or venous insufficiency in a previously healthy flap. Post-operative monitoring produced characteristic traces for successful and unsuccessful free flaps. The ability of this method to discriminate between a satisfactory flap, an arterial failure, and a venous failure was highly significant (P less than 0.001).
A method is described for predicting the outcome of experimental free flaps at the time of surgery using a directional ultrasound Doppler flowmeter. Tests of both arterial and venous anastomoses have been developed. Provided that both anastomoses are individually assessed, the technique is 100% accurate and is recordable. Spectral analysis of truly directional Doppler signals has provided knowledge of the peripheral resistance within a flap.
Intradermal interstitial fluid pressure (IFP) in the rat epigastric flap has been measured under varying conditions of blood flow. Pressure changes were not as expected. An attempt has been made to explain these anomalous results using radiolabelled isotopes.
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A preliminary study suggested that some patients with ischaemic rest pain improved during treatment with naftidrofuryl (Praxilene). Therefore, a controlled trial was performed in which 16 patients were treated for 7 days with placebo (given intravenously and in tablet form), and were then given Praxilene for a further 10 days and assessed subjectively and objectively. The drug regimen used was Praxilene 200 mg 8-hourly by mouth and 200 mg twice-daily intravenously. Although no objective improvement could be attributed to the drug, 7 of the 16 patients showed subjective improvement during the placebo period, but reported no further improvement during the Praxilene period (placebo responders). Five patients did not respond to the placebo but reported an improvement at all. Praxilene produced subjective improvement in the symptoms of rest pain in 5 patients out of 16 in this small study.
Fasting levels of serum triglyceride, serum cholesterol, lipoprotein, uric acid, fibrinogen and carboxyhaemoglobin (COHb) were measured in 64 patients with stenosing arterial disease before reconstructive surgery, and were compared with those for normal, age- and sex-matched controls. All except fibrinogen were significantly higher in the patients with arterial disease than in the controls. The outcome of arterial reconstruction, assessed both clinically and by Doppler pressure measurement, was compared in terms of these risk factors. The reconstruction of 12 patients failed between 3 months and 5 years, leaving 52 patients with patent reconstructions at the end of the follow-up period. There was no difference between the two groups in terms of any of the risk factors, except for COHb. The COHb level (associated with inhalation of cigarette smoke) was significantly higher in the reconstruction failure group than in the reconstruction success group. We believe that patients should stop smoking cigarettes before reconstructive arterial surgery is undertaken.
An experimental model is described for end-to-end and end-to-side anastomosis involving rabbit femoral vessels. In this experimental situation the ultimate test of patency is transection beyond the anastomosis. Against this the micro-electromagnetic flow probe has been evaluated using 17 rabbits and 24 procedures. Likewise the directional Doppler has been evaluated with 13 rabbits involving 22 procedures. The condition of the anastomosis could always be accurately assessed by the directional Doppler but not always by the electromagnetic flow probe.
There are many factors which contribute to the outcome of arterial reconstruction--the site and extent of disease and its rate of progression as well as mechanical and biochemical factors. Mechanical influences are described in 10 patients in whom dilatation of their Dacron graft occurred between 1.4 and 4.5 years after reconstructive surgery. The outcome of arterial reconstruction has also been examined in relation to a number of biochemical risk factors. Only carboxyhaemoglobin levels (associated with cigarette smoking) were higher amongst those patients whose reconstructions failed during a 5-year follow-up compared with those whose reconstructions remained patient. There is little evidence that dietary advice is merited, but all patients should stop smoking cigarettes before elective arterial surgery.
In order to perform extracranial to intracranial microrevascularisation a good end-to-side microvascular anastomosis technique is the first essential. The rabbit femoral vessels are similar in size to the human cortical branches of the middle meningeal artery and superficial temporal artery and an easy technique of end-to-side anastomosis of these vessels is described. This pays particular attention to proof of patency until the last stitch is applied. Assessment of patency in all three directions is checked by the directional Doppler or the electromagnetic flow probe.
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The fall in ankle systolic pressure after exercise serves as an objective indicator of the severity of haemodynamically important peripheral arterial disease. Twenty-six patients were studied to establish the effects of different work loads on the pressure response and to develop a test to standardise these effects. The patients walked for one or two minutes at 4 km/h and one or two minutes at 6 km/h, and the fall in pressure was the same when measured immediately after exercise. The time taken for the pressure to return to the pre-exercise value varied. As the fall in pressure occurs after only one minute of exercise at 4 km/h on a 10% slope, this might be adopted as a standard test. It is acceptable to the patient, since claudication, angina, and shortness of breath rarely occur. It is sensitive enough to detect mild or asymptomatic disease and is useful in following up patients.
In vitro dilution of blood with normal saline produces an increase in coagulability which can be accurately measured by the thrombelastograph. The degree to which the coagulability of an individual patient's blood is increased by such dilution appears to be directly related to that patient's risk of developing a postoperative deep venous thrombosis. In a small group of patients undergoing major abdominal surgery, a preoperative test based on the coagulability increase after in vitro saline dilution successfully predicted all those who subsequently developed a postoperative deep venous thrombosis on 125I-fibrinogen scanning.
Using a new method of measuring whole blood clotting time, we have confirmed the findings of others, that blood clots faster when diluted with saline. A prospective trial was designed to test the hypothesis that intravenous saline peroperatively causes hypercoagulation and increases the risk of venous thrombosis. Sixty patients admitted for routine laparotomy were randomly allocated to either a group receiving intravenous fluids during or after operation (Wet), or a group receiving no intravenous fluids (Dry). The Wet patients became significantly more haemodilute and hypercoagulable than the Dry (P < 0.001), and these changes correlated. A postoperative deep vein thrombosis occurred in 30 per cent of the Wet patients, but in only 7 per cent of the Dry (P < 0.05). The need for intravenous fluids during uncomplicated surgery is probably unproved, and their greater use may have contributed to the increasing prevalence of venous thromboembolism.