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Biomedical subjects

M Horrocks

Publications and source records attributed to M Horrocks.

At least 55 records · Page 3Linked to original sources
PubMed1995

Use of hand-held Doppler to identify 'difficult' forearm veins for cannulation.

Intravenous cannulation is a necessary procedure in many hospital patients. Some patients are regarded as having 'impossible' veins that are invisible and impalpable despite venous tourniquet. We investigated the use of a hand-held Doppler to identify veins suitable for percutaneous cannulation in such patients. A total of 24 arms in 12 patient volunteers with invisible and impalpable forearm veins was studied by squeezing the ipsilateral hand and using a hand-held 8 MHz Doppler probe on the forearm. Each venous signal was noted and the loudest chosen. Classification as 'good' or 'poor' was made on signal strength. The best signal was then mapped and the direction was indicated by a line on the skin. Each forearm was examined using a colour-flow Duplex. All veins were noted and diameters measured with and without tourniquet. These results were compared with the best veins found by hand-held Doppler. In all, 23 (96%) arms had the largest vein correctly identified by the hand-held Doppler. All 19 (100%) described as 'good' on signal had a diameter of 2.0-4.2 mm (mean 3.2 mm). All 4 (100%) described as 'poor' on Doppler signal had diameters of 1.4-1.7 mm (mean 1.6 mm). Hand-held Doppler, used as described, can accurately identify forearm veins larger than 2.0 mm in diameter in patients with invisible and impalpable veins with venous tourinquet. These veins should be amenable to percutaneous cannulation.

Catheterization, Peripheral↗
PubMed1994

Femoropopliteal angioplasty for severe limb ischaemia.

Fifty patients undergoing 51 percutaneous transluminal angioplasties of the femoropopliteal segment for severe limb ischaemia were reviewed regularly. They comprised 30 men and 20 women of median age 70 (range 56-85) years. There were two deaths within 30 days. At 2 years the cumulative patient survival rate was 60 per cent. Eleven angioplasties were technical failures, 25 failed in the first 6 months and 14 were successful at 6 months' follow-up; in addition one patient died from myocardial infarction within 30 days of technically successful angioplasty. Subsequent vascular procedures were successful in 11 limbs following failed angioplasty. The primary limb survival rate was 42 per cent at 2 years. There were eight major complications after angioplasty, requiring amputation in five instances. Of the 23 long occlusions (greater than 5 cm) that were recanalized and dilated, 22 procedures failed within 6 months. The run-off score and diabetic status did not predict outcome. In this group of patients angioplasty had a low durability. Dilatation of long occlusions is associated with high rates of reocclusion and, on the basis of these results, should not be performed.

Aged↗
PubMed1994

Preoperative assessment of the pedal arch using pulse generated runoff and subsequent femorodistal outcome.

Calf vessel continuity with an intact pedal arch is an important factor in femorodistal (FD) bypass for critical ischaemia. Pulse generated runoff (PGR) was used in combination with the pedal arch patency test of Roedersheimer to determine preoperatively calf vessel and pedal arch patency. Three pedal arch groups were identified; complete (two calf vessels in continuity), incomplete (one vessel) and occluded (no vessels). One hundred non-reversed FD grafts were performed for critical ischaemia (63 men and 37 women), median age 72 (range 43-89 years). Sixteen grafts were to the above knee popliteal artery, 36 to the distal popliteal, three to the tibioperoneal trunk and 45 to a single calf vessel. There were 25 complete, 64 incomplete and 11 occluded pedal arches. The overall primary patency rate was 73%, nine grafts were successfully revised giving a secondary patency rate of 83.5%. The secondary graft patency rates for the above knee popliteal, below knee popliteal, tibioperoneal and single calf vessel grafts were 100, 92, 66 and 66% respectively. The 1 year graft patency rates for grafts to a complete, incomplete and occluded pedal arch were 88, 75 and 9% respectively (Lee-Desu p < 0.01). Similar results were obtained for limb salvage; 100, 84 and 24% respectively (p < 0.01). These results confirm the value of PGR in the preoperative assessment of patients with critical ischaemia. In reconstructions to the popliteal artery, PGR derived pedal arch status does not appear to influence the outcome. By contrast PGR derived pedal arch status in an excellent predictor of success following reconstructions to a single calf vessel.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Early reoperation rates after arterial surgery.

Between 1 January 1985 and 31 December 1991, 2426 patients underwent arterial surgery. Three hundred and seventy one reoperations were performed on 258 patients within 30 days of the initial procedure. One hundred and ninety three (52%) of the operations were attempted revascularisations, 95 (26%) were amputations and 58 (16%) were to control bleeding. One hundred and sixty nine (66%) of first operations were successful, but 76 patients required a further 113 reoperations. The mortality of reoperation was 16%, while the mortality of patients not requiring reoperation was 9% (p < 0.01). The mean hospital stay in days was higher in patients requiring reoperation (p < 0.05). Where appropriate, patients should be informed of the significant incidence of reoperation and reoperative mortality after vascular surgery. The increased hospital stay in reoperated patients has financial implications.

Adolescent↗
PubMed1994

Transcranial Doppler evaluation of cerebral hyperperfusion syndrome after carotid endarterectomy.

Cerebral hyperperfusion syndrome after carotid endarterectomy is rare. Unilateral headache, confusion, seizures or focal neurological signs may occur and intracranial haemorrhage may be a terminal event. We report a case of hyperperfusion accompanied by transient hemiparesis. The changes in cerebral perfusion were documented using transcranial Doppler sonography which helped to make the diagnosis.

Arterial Occlusive Diseases↗
PubMed1994

Criteria for identification of the "at-risk" infrainguinal bypass graft.

The criteria for identifying the "at-risk" femorodistal bypass are controversial. Eighty-eight patients were entered into a surveillance programme using ankle-brachial pressure indices (ABPI), colour Duplex and intraarterial digital subtraction angiography (IADSA). Changes in ABPI of more than 0.1 identified 12/22 (51%) grafts thought to be "at-risk". In the 88 grafts, a PMV (peak mean velocity) < 45 cm per second had a sensitivity and specificity of 55 and 85% compared to 91 and 95% if a PMV < 45 cm per second and a V2/V1 ratio of greater than 2 was used to identify the 22 grafts "at-risk". In total 341 examinations were performed, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy for impedance analysis was 70, 90, 48, 97 and 91% respectively, compared to 93, 97, 77, 99 and 97% for colour Duplex in identifying the "at-risk" grafts. Between 6 weeks and 12 months the mean PMV was seen to drop by 29% and the mean impedance score by 19%. The most sensitive mode of non-invasive graft surveillance is colour Duplex providing the assessment involves both a measurement of the velocity ratio and the absolute velocity. However, impedance analysis is a better screening test than ABPI and PMV.

Angiography, Digital Subtraction↗
PubMed1994

The aetiology of vein graft stenoses.

The aetiology of vein graft stenosis is poorly understood. In a cohort of 88 patients, the mean internal diameter of the vein grafts that developed a stenosis was 3.7 (3.1-4.2) mm compared to 4.7 (4.4-5.0) mm in those that did not (p = 0.006). The mean lowest compliance value in the 11 patients who developed a stenosis was 0.1 (0.07-0.13) % per mmHg compared to 0.21 (0.19-0.23) % per mmHg in the rest (p < 0.001). The presence of vein incompetence, site of tributaries or valves and the degree of endothelial cell loss were not related to the development of vein graft stenoses. The presence of a macrophage infiltrate (p < 0.001), lymphocyte infiltrate (p < 0.025) and subendothelial smooth muscle cells (p < 0.05) were all significantly more common in those grafts that developed a stenosis. Vein quality is an important factor in the development of graft stenoses.

Aged↗
PubMed1994

Prediction of long saphenous vein graft adaptation.

The ability of vein to dilate may allow smaller veins to be used for bypass if this change could be predicted. Sixty patients undergoing femorodistal popliteal or infrapopliteal bypass have had their long saphenous vein studied. Diameter measurements of the long saphenous vein have been performed using an ATL Duplex scanner at the groin, mid-thigh and knee. Measurements were performed preoperatively both at rest and with a venous occlusion cuff to dilate the vein and subsequently at 7 days and 3, 6, 9, 12 months after implantation. The mean diameter of the vein at the mid thigh was 4.2 mm non dilated, 5.1 mm with occlusion, 5.4 mm 7 days postoperatively and 5.5 mm at 12 months (p < 0.01 ANOVA). The mean diameter of the vein at the knee was 3.8 mm non-dilated, 4.8 mm with occlusion, 4.8 mm at 7 days and 5.0 mm at 12 months after operation (p < 0.01 ANOVA). If the minimum resting internal diameter of vein regarded as being suitable for bypass was 3 mm, this technique would have increased the vein utilisation rate by 22%. These results show that by using a technique of venous occlusion at the time of preoperative vein mapping the adaptive response of the vein can be predicted and this can result in an increased rate of vein utilisation.

Aged↗
PubMed1994

Angioplasty gives good results in critical lower limb ischaemia. A 5-year follow-up in patients with known ankle pressure and diabetic status having femoropopliteal dilations.

137 consecutive patients with known ankle pressures and diabetic status had attempted femoro-popliteal dilatation for lower limb ischaemia in an English provincial teaching hospital. All except one were followed until failure or death to assess survival and amputation rates. Non-diabetic patients with critical limb ischaemia had a 5 year survival rate of 62.2% (SE 17.1) compared to 50.5% (SE 7.0) for claudicants, with no significant difference on logrank testing. Diabetics had a relative risk of amputation of 11.2 compared to nondiabetics. Patients with pre-treatment ankle pressures of 50 mm or less had a relative risk of amputation of 2.6 compared to those with higher resting pressures. It is concluded that angioplasty should be the treatment of first choice in critical lower limb ischaemia whenever it is technically possible. Including patients with rest pain in the critical ischaemia group does not significantly affect cumulative patency rates.

Adult↗
PubMed1994

Blood flow in the internal carotid artery and velocity in the middle cerebral artery during carotid endarterectomy.

A stenosing atherosclerotic plaque of the internal carotid artery acts as a source of emboli and may impede flow. The contribution made by a stenosed carotid artery to cerebral perfusion is unclear. This study examined blood flow in the internal carotid artery and a comparison was made with the effect of clamping on flow velocity in the middle cerebral artery. Some 50 patients were assessed before carotid endarterectomy by preoperative duplex scanning, triplanar arteriography and transcranial Doppler ultrasonography. At operation, maximal flow in the internal carotid artery was measured using a Doppler flowmeter and flow velocity was monitored by transcranial Doppler. No correlation was found between the degree of stenosis and resting flow velocity. Mean flow in the internal carotid artery in patients with > 90% stenosis was significantly lower than those with lesser stenoses (P < 0.01). However, a mean minimal blood flow of 141 ml/min passed through the > 90% stenoses. The effect of internal carotid artery clamping on flow velocity was similar irrespective of the degree of stenosis. In patients with > 90% stenosis, the internal carotid artery continues to make an important contribution to cerebral perfusion.

Aged↗
PubMed1993

Choice of agent for peripheral thrombolysis.

Evidence has been accumulating that tissue plasminogen activator (tPA) is a more rapid and effective agent than streptokinase for peripheral thrombolysis. Twenty-three patients with acute limb-threatening ischaemia treated with tPA (0.5 mg h-1) over 15 months were compared with 20 consecutive patients previously receiving streptokinase (5000-10,000 units h-1). There were no major differences between the rates of complete and partial lysis (61 per cent for tPA versus 65 per cent for streptokinase) or limb salvage (65 versus 55 per cent respectively). Complication rates were also similar. It was not possible to show that tPA, an agent ten times more expensive than streptokinase, was superior for peripheral thrombolysis.

Adult↗
PubMed1993

Intraoperative measurement of vascular graft resistance as a predictor of early outcome.

The quality of distal run-off is one of the most important factors influencing the early outcome of femorodistal vein grafting. During femoropopliteal and infrapopliteal bypass, assessment of graft resistance and flow were made using a combination of Doppler flowmeter recordings and measurements of arterial pressure. In a series of 100 reconstructions there were 12 early failures. The mean (95 per cent confidence interval (c.i.)) maximal flow measurement in the group of grafts that failed when anastomosed to the popliteal artery or tibioperoneal trunk was 125 (74-176) ml/min compared with 256 (223-289) ml/min in successful grafts (P = 0.006). The corresponding figures for grafts inserted into a single crural vessel were 99 (72-126) and 165 (137-193) ml/min (P < 0.02). In the group that failed the mean (95 per cent c.i.) resistance after papaverine injection was 1.02 (0.82-1.22) peripheral resistance units (p.r.u.) compared with 0.47 (0.44-0.51) p.r.u. in the successful group (P < 0.001). Using a combination of resistance > 0.9 p.r.u. and capacity loss ratio after papaverine injection < 10 per cent to identify grafts that subsequently failed, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 92, 97, 85, 99 and 97 per cent respectively. These results confirm that haemodynamic measurements can be used at operation to identify a group of patients in whom bypass is likely to fail.

Adult↗