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Biomedical subjects

I A Thomson

Publications and source records attributed to I A Thomson.

At least 19 recordsLinked to original sources
PubMed2001

Non-saphenofemoral venous reflux in the groin in patients with varicose veins.

OBJECTIVES: To investigate the incidence, clinical significance, anatomical variation and physiology of non-saphenofemoral venous reflux (non-SF reflux) in the groin. DESIGN: Prospective study. MATERIALS: A total of 1072 vascular diagnostic workups in 680 patients with possible venous diseases to the legs were included. METHODS: Duplex scanning and air plethysmography. RESULTS: A total of 1022 legs had venous diseases. Of these, 101 (9.9%) had non-SF reflux in the groin. Such reflux occurred in recurrent varicose veins (RVV) in 16.3%, in primary varicose veins (PVV) in 6.1% and in deep venous thrombosis (DVT) in 8.0%. Two patterns of reflux were distinguished: epigastric reflux from lower abdominal wall veins (71 legs) and pudendal reflux from perineal and/or gluteal veins (30 legs). Pudendal reflux was almost exclusive to women and did not occur with DVT. If there was only non-SF reflux at the groin the venous filling indices (VFI) were close to normal (1.7+/-1.0 ml/s for RVV, 1.9+/-1.2 for PVV, 1.7+/-1.0 for DVT) and no active ulcers were observed. However, if non-SF reflux was associated with saphenofemoral or other reflux the VFIs (3.3+/-2.3 ml/s for RVV, 3.8+/-1.5 ml/s for PVV) were abnormal (p <0.05) and ulcers occurred in 11/32. CONCLUSION: Non-SF reflux in the groin is common. Such reflux may be missed at initial surgery and lead to recurrence of varicose veins. However, the venous physiological disturbance of such reflux is mild and it is not associated with ulcers unless combined with reflux at other sites in the leg.

Female↗
PubMed2000

Venous physiology in the different patterns of recurrent varicose veins and the relationship to clinical severity.

Venous function measured by air-plethysmography (APG) was compared to anatomical patterns of reflux assessed by duplex scanning and associated clinical features in 253 limbs with recurrent varicose veins following previous superficial venous surgery. The results showed that a previous history of deep venous thrombosis, previous procedure with preservation of the long saphenous vein, and a history of healed ulcer or current ulcer were each associated with worse venous function. Patterns of reflux which included multiple sites of reflux and presence of deep incompetence were also associated with worse venous function. Where there was reflux in the groin, limbs with a wide recurrent saphenofemoral junction presented the worst venous filling time and venous filling index, whereas those with reflux unrelated to the common femoral vein had nearly normal venous physiology and occurred almost exclusively in females. The other patterns of recurrence in the groin were physiologically indistinguishable from each other. In conclusion, certain patterns of reflux, clinical and operative features are associated with worse venous physiology in limbs with recurrent varicose veins. These features of recurrence with more severe physiological disturbance may necessitate a higher priority for surgical intervention.

Blood Flow Velocity↗
PubMed1999

Complexity- and risk-adjusted model for measuring surgical outcome.

BACKGROUND: Although currently available surgical scoring systems have good outcome predictive power, their use is often limited by complexity and their non-dynamic nature. The aim of this study was to develop and test a risk adjustment for general surgical audit which is both simple and dynamic, while preserving a high predictive power for surgical morbidity. METHODS: Twelve easily measured, well defined prognostic variables for morbidity were identified from the Otago Surgical Audit data collection form and stratified into suitable categories. Logistic regression was used to adjust for confounding between factors, identifying risk factors with the strongest prognostic value for the outcome of severe and intermediate complications. The resulting model was tested by back-validation and validation. RESULTS: The derived risk adjustment included all 12 variables. Adjusted odds ratios for all variables were markedly lower than unadjusted values. After logistic regression, the strongest predictors of postoperative morbidity were duration of operation, operation category, inpatient status and organ system in which the procedure was carried out. The area under the receiver operating characteristic curve was 0.86. CONCLUSION: A simple dynamic model for surgical morbidity has been developed which is comparable to previously published surgical scoring systems in terms of predictive power. This risk adjustment tool can be incorporated into the existing audit system, enabling comparison of surgical unit performance.

Adolescent↗
PubMed1999

Venous morphology predicts class of chronic venous insufficiency.

OBJECTIVES: this study aimed to determine specific morphological differences in long saphenous veins from patients with various grades of chronic venous insufficiency. DESIGN: comparable veins from a control group were compared with patients with either primary varicose veins or those with associated skin changes including venous ulcers. MATERIALS: below-knee segments of saphenous vein were examined from a total of 64 patients. METHODS: veins were examined for elastic-tissue disruption and endothelial-cell changes and comparisons made between clinical groups. RESULTS: elastic-tissue disruption, as measured by fragmentation of the elastic lamina and the percentage of the intimal-medial boundary containing elastin, increased with increasing severity of venous disease. Moreover, endothelial cells became more densely packed, as measured by endothelial cell and endothelial-cell nuclei density, with increasing severity of disease. Other measures such as the density of multinucleated "giant" endothelial cells and the number of nuclei per "giant" cell did not correlate with venous disease, however. CONCLUSIONS: this study demonstrates that several morphological characteristics of superficial saphenous veins correlate with severity of venous disease. In particular, the alterations to the structure of elastic tissue within these veins appears indicative of the progressive nature of chronic venous insufficiency.

Aged↗
PubMed1998

Staphylococcal neonatal necrotising fasciitis: survival without radical debridement.

Necrotising fasciitis is a serious infection associated with high morbidity and mortality. The conventional treatment is radical resection of the involved area with antibiotic as well as intensive supportive therapy. We describe a case of extensive truncal necrotising fasciitis in a neonate, secondary to Staphylococcus aureus infection successfully treated with intensive antibiotic therapy and multi-organ support, followed by fasciotomies, drainage and betadine irrigation. The successful outcome without radical resection could be due to the viability of superficial skin, S aureus as the causative organism and the excellent blood supply of cutaneous neonatal tissue.

Anti-Bacterial Agents↗
PubMed1996

Endothelin-1 is increased overlying atherosclerotic plaques in human arteries.

The distribution of Endothelin-1 (ET-1), a potent vasoactive peptide, within endothelium of human atherosclerotic arteries was examined using a novel en face immunohistochemical technique. The vast majority of endothelial cells were immunoreactive for ET-1. Staining intensity was increased in areas overlying atherosclerotic plaques, calcified media, fatty streaks and about flow dividers, compared with adjacent regions. Multinucleated 'giant' endothelial cells were more common in regions containing strong ET-1 staining than elsewhere. Clusters of leucocytes (probably monocytes) were frequently observed adhering to the endothelial monolayer but not neighbouring regions of denudation. Occasionally underlying macrophage/foam cells and smooth muscle cells were exposed to the surface and included in the en face (Häutchen) preparation. Smooth muscle cells did not stain for ET-1 while macrophages and the larger foam cells were positive for ET-1. These results support the hypothesis that expression of ET-1, at sites containing atheromatous disease, may be involved in the development of atherosclerosis.

Aged↗
PubMed1994

Iloprost reduces leukocyte adhesion in skeletal muscle venules following ischaemia in a rat model of femorodistal bypass.

UNLABELLED: Intraarterial bolus treatment with the prostacyclin analogue iloprost appears to have a prolonged beneficial effect on femorodistal bypass graft flow which extends beyond the duration of its vasodilator properties. The effect of iloprost on the microcirculation rendered ischaemic over the time course of a distal bypass operation was investigated in this study without the use of fluorescent light. METHODS: A rat model was designed to allow prolonged direct observation of leukocyte-venular endothelial adhesion in a femorodistal bypass simulation. The extensor digitorum longus (EDL) muscle of 10 rats was subjected to two 30 minute periods of ischaemia by a non-venous occluding tourniquet and to simulate some of the changes of chronic ischaemia the adverse effect of ischaemia was accentuated by indirect electrical stimulation via the lateral popliteal nerve. RESULTS: Intraarterial bolus treatment with iloprost significantly reduced the total numbers of leukocytes observed in EDL venules, and the numbers exhibiting evidence of adhesion by rolling or sticking to venule endothelium compared with saline controls at one hour post ischaemia. Ischaemia induced vasodilatation and reduced shear stress by a similar and significant amount in both groups. CONCLUSION: Two periods of ischaemia and reperfusion similar to those which occur during bypass grafting resulted in changes in the distal microcirculation consistent with reperfusion injury. Intraarterial bolus treatment with iloprost prevented these leucocyte-endothelial changes. It appears iloprost may have a role in reducing leukocyte-induced reperfusion injury in femorodistal bypass surgery.

Animals↗
PubMed1993

Adjuvant prostanoid treatment during femorodistal reconstruction.

A prospective randomized placebo-controlled trial was conducted to determine the effects of the stable prostacyclin analogue iloprost on early graft patency and hemodynamic parameters during femorodistal reconstruction for critical leg ischemia. Peripheral resistance and graft blood flow were measured using an operative Doppler flowmeter and graft pressure transducer. Postoperative graft surveillance was continued at 1-month and then at 3-month intervals by duplex Doppler ultrasonography, measurement of ankle-brachial pressure indices, and intravenous digital subtraction angiography when indicated. In patients receiving 3000 ng of iloprost (n = 45) infused into the graft on completion there was an immediate mean decrease in peripheral resistance of 44% that persisted to skin closure in comparison with controls (n = 38) in whom no such decrease in resistance occurred (p < 0.001, Wilcoxon test). During the same period, mean graft blood flow increased in iloprost-treated patients by 74.5% compared with controls in whom there was a 6% increase in flow (p < 0.001). Primary cumulative patencies at 1 month were significantly higher in iloprost-treated grafts, 98% compared to 83% for controls (p < 0.05, log-rank test). Cumulative primary patencies at 1 year and secondary patencies at 1 month and 1 year were also greater in the iloprost-treated group (67%, 98%, and 87.6%, respectively) compared to controls (65%, 86%, and 79.3%, respectively), but these did not achieve statistical significance. A single bolus infusion of iloprost has prolonged beneficial effects on graft blood flow and peripheral resistance during femorodistal reconstruction. This is reflected by improved early primary graft patencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The role of computerized tomography in aorto-iliac vascular disease.

Computerized tomography (CT) now has a definite place in the assessment of aortic vascular disease. In a study of 96 patients with abdominal or thoracic aorto-iliac problems, CT proved most useful in the management of haemodynamically stable patients with abdominal aortic aneurysms that were suspected of leaking. The complex anatomy associated with thoracic and abdominal aneurysms and aortic dissection was clearly defined. The interpretation of scans on postoperative aortic graft patients was difficult and less often helpful. The incidental finding of aortic disease during abdominal scans for a variety of other indications was infrequent and seldom contributed to patient management. The indications for CT have become far more selective.

Aged↗
PubMed1993

Postoperative chylothorax: a case for recycling?

Postoperative chylothorax in a patient who was rapidly deteriorating despite conservative treatment is described. A system of recycling chyle from the pleural space through a filter and pump into the subclavian vein is discussed. The history of reinfusion of chyle is reviewed.

Aged↗
PubMed1991

Aggressive arterial reconstruction for critical lower limb ischaemia.

A consecutive series of 315 patients underwent arterial reconstruction for 329 critically ischaemic lower limbs over a 5-year period. Patients were not excluded from limb salvage surgery on the basis of poor run-off on preoperative angiography. Femorocrural bypass to a single calf vessel was required in 239 limbs (73 per cent); the 30-day cumulative mortality rate was 7 per cent, rising to 41 per cent at 5 years. Cumulative graft patency at 30 days, 1 year, 2 years and 5 years was 96, 85, 84 and 82 per cent respectively and was independent of the level of reconstruction. In situ long saphenous vein was the conduit of choice for distal bypass but, when this was absent, satisfactory results were obtained with arm vein or composite vein grafts. Acceptable results can be obtained for reconstructive surgery without preoperative angiographic selection of patients. An aggressive approach to limb salvage is therefore justified.

Aged↗
PubMed1990

Effect of isoflurane on the canine hepatic circulation and hepatic oxygen balance.

We have studied the effects of increasing concentrations of isoflurane (1%, 1.5% and 2%) on the hepatic circulation and the oxygen supply and demand of the liver in six barbiturate-anaesthetized greyhounds. Following laparotomy, the hepatic arterial and portal venous blood flows were measured continuously using electromagnetic flow probes, and mean arterial pressure and cardiac output were measured as appropriate. Cardiac output was maintained while mean arterial pressure and systemic vascular resistance decreased in a dose dependent manner. Hepatic arterial and total liver blood flows and oxygen supplies decreased significantly at all isoflurane concentrations. Portal venous blood flow and portal venous oxygen supply did not decrease significantly until the concentration of isoflurane was increased to 2% and 1.5%, respectively. Hepatic oxygen consumption was reduced with 2% isoflurane (P less than 0.05), but this was insufficient to offset the reduction in hepatic oxygen supply and resulted in an increased extraction of oxygen by the liver.

Anesthesia, General↗
PubMed1988

Effects of ketamine on liver blood flow and hepatic oxygen consumption. Studies in the anaesthetised greyhound.

The effects of three increasing doses of ketamine on the blood flow to, and oxygen consumption of, the liver, were studied in seven anaesthetised greyhounds. Hepatic arterial and portal venous blood flows were measured continuously using electromagnetic flow probes, and mean arterial pressure and cardiac output monitored as appropriate. Ketamine, even at the highest dose, had little effect on the blood flow to the liver: hepatic arterial blood flow and portal venous blood flow did not differ significantly from their baseline values. However, the oxygen delivery to the liver decreased due, probably, to an increase in oxygen consumption by the pre-portal organs.

Anesthesia, Intravenous↗
PubMed1986

Effects of certain i.v. anaesthetics on liver blood flow and hepatic oxygen consumption in the greyhound.

The effects of increasing concentrations of thiopentone, Althesin and etomidate on liver blood flow and hepatic oxygen consumption were investigated in the anaesthetized greyhound. All three agents studied produced dose-related decreases in general cardiovascular indices such as mean arterial pressure, cardiac output and systemic vascular resistance; all three anaesthetics produced decreases in liver blood flow. During the low rates of infusion with Althesin and etomidate, significant decreases in hepatic arterial blood flow were recorded at a time when the systemic circulation was not significantly affected. Indeed, during the low rates of infusion with each of the three agents, hepatic arterial resistance and mesenteric vascular resistance increased by up to 40% above baseline values. During the high rates of infusion, hepatic arterial and mesenteric vascular resistances either returned to or decreased below control values and the decreases in liver blood flow were a consequence of generalized cardiovascular depression. Despite relatively unchanged hepatic oxygen consumption, all the anaesthetics produced significant decreases in the hepatic oxygen supply.

Alfaxalone Alfadolone Mixture↗
PubMed1985

The uniformity of liver perfusion as measured by krypton-85 clearance.

The uniformity of regional liver perfusion was studied in eight anaesthetised dogs by measuring the clearance of 85Kr with three beta detectors, and the results were compared with independent measurements of mean perfusion by electromagnetic flowmetry. The intra-hepatic flow distribution was found to be heterogeneous, with a coefficient of variation between locations which averaged 17%. The pattern of flow varied from liver to liver, and there was no consistent tendency for any one of a limited number of locations to be better or less well perfused than any other. Discrepancies between 85Kr clearance and flowmeter measurements were of a similar magnitude to inter-regional variations in flow, and there was no evidence of a systematic difference between the two measurement techniques. Individual 85Kr clearance measurements can misrepresent the perfusion of the liver as a whole, and averaging several measurements performed in different locations is likely to yield a better estimate of mean flow.

Animals↗
PubMed1983

Effect of increased concentrations of carbon dioxide during halothane anaesthesia on liver blood flow and hepatic oxygen consumption.

The effects of hypercapnia (during halothane anaesthesia) on the hepatic circulation and hepatic oxygen consumption were investigated in anaesthetized greyhounds. The administration of 1% halothane alone caused significant decreases in both hepatic arterial and portal venous blood flows. Hepatic oxygen consumption did not change significantly. When carbon dioxide was added to the inspired gas mixture during the continued administration of halothane, hepatic arterial blood flow showed a further decrease (P less than 0.01), while portal venous flow increased markedly. This resulted in an overall increase in total liver blood flow. Hepatic oxygen supply increased also. However, hepatic oxygen consumption increased during the periods of hypercapnia. Thus, although the hypercapnia increased the oxygen supply to the liver, there was no improvement in the supply: demand ratio.

Anesthesia, Inhalation↗