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Biomedical subjects

G M Baxter

Publications and source records attributed to G M Baxter.

At least 37 records · Page 2Linked to original sources
PubMed1997

Current concepts in management of abdominal adhesions.

Adhesions are an important complication after abdominal surgery in horses and foals, especially after small intestinal resection and anastomosis. Prevention therapies used in horses have included nonsteroidal anti-inflammatory drugs, antibiotics, heparin, dimethyl sulfoxide, carboxymethylcellulose, and meticulous surgical technique; however, the ideal surgical technique and prevention therapy has not been determined. Further, treatment of abdominal adhesions has a poor prognosis, emphasizing the need for improvements in prevention methods.

Abdomen↗
PubMed1996

The value of serial Doppler imaging in central retinal vein occlusion: correlation with visual recovery.

A prospective study of 80 patients with central retinal vein occlusion (CRVO) was performed to determine whether Doppler flow measurements can predict visual outcome. All patients at presentation, had full ophthalmological examination, fluorescein angiography, relative afferent pupillary defect test and electroretinography to distinguish between ischaemic and non-ischaemic occlusions. In addition, all patients were examined at presentation with colour Doppler ultrasound using a 7.5 MHz linear array probe. Both the clinical examinations and colour Doppler ultrasound were repeated at one year following initial presentation in a smaller group of 20 patients. A significant reduction in velocity within the central retinal vein was noted in the ischaemic compared with non-ischaemic CRVO affected eye at the time of the baseline scan. The minimum venous velocity within the central retinal vein was most severely affected. No velocity difference was present within the ophthalmic artery. Follow-up at one year with colour Doppler ultrasound showed an increase in blood velocity values within the central retinal vein in the CRVO affected eye but this was of no prognostic value and did not correlate with clinical outcome. Serial colour Doppler ultrasound examinations, therefore, have no clinical application in patients with CRVO and are of no prognostic value.

Adult↗
PubMed1996

Instrument sterilization, skin preparation, and wound management.

Recent advances in instrument sterilization include the introduction of gas plasma sterilization and the increased use of glutaraldehyde. Gas plasma sterilization has the advantages of no toxic residue effects, reduced turnover time, and applicability for sterilization of heat- and moisture-sensitive instruments. Chlorhexidine gluconate (4%) appears to be a superior preoperative surgical scrub for both the surgeon and the patient because of its increased antimicrobial efficacy, residual activity, and minimal tissue reactions. There are many new wound dressings and topical medications for treatment of wounds, but the efficacy of most of these preparations has been evaluated only in humans, dogs, and cats. The ideal topical wound preparation and dressing for equine wounds, particularly wounds affecting the distal limb, have not yet been found.

Animals↗
PubMed1996

Surgical materials and wound closure techniques.

Recent innovations in surgical materials have helped to enhance wound healing and protect surgical wounds from infection. Materials such as polyglyconate have been evaluated in equine tissues and found efficacious. Other materials, such as poliglecaprone 25, appear to have qualities useful to equine surgery but are untested in equine tissues. Care must be taken to fully evaluate a new surgical material because its usefulness in equine tissues may not match that in human or laboratory animal tissues. Furthermore, use of disposable materials in surgery, although considered ideal for maintenance of sterility, may come under more scrutiny in the future as environmental issues gain prominence. We tend to reserve disposable materials for prolonged procedures and for procedures that carry high risk of failure if infection develops.

Animals↗
PubMed1996

Instrumentation and techniques for treating orthopedic infections in horses.

Orthopedic infections-those involving bones, joints, tendon sheaths, or bursae-are some of the most difficult problems for equine surgeons to treat successfully. Sources of the infection are usually hematogenous, traumatic, or iatrogenic and knowledge of the most likely causative bacteria is very useful in selecting the most appropriate antimicrobial(s) to either prevent or treat these infections in horses. This article discusses the clinical findings, diagnosis, treatment, and prevention of orthopedic infections in horses. More recent treatment methods such as synovial drainage techniques (arthroscopy and arthrotomy), intrasynovial antimicrobials, regional perfusion of antimicrobials, and antimicrobial-impregnated polymethylmethacrylate (PMMA) beads or cylinders are also addressed.

Animals↗
PubMed1996

Colour Doppler imaging in giant cell (temporal) arteritis: serial examination and comparison with non-arteritic anterior ischaemic optic neuropathy.

The ophthalmological manifestations of giant cell arteritis (GCA) present a difficult diagnostic and management problem to the ophthalmologist. The orbital circulation is frequently involved in the disease process. The effects of GCA on orbital blood flow assessed by colour Doppler imaging (CDI) were investigated in this study. Serial CDI examinations of the orbital blood vessels were performed (at presentation, 2 days, 1 week and at 1 month) on 7 patients with GCA. CDI examination at presentation was also performed on 4 patients with non-arteritic anterior ischaemic optic neuropathy (AION) for comparison. Blood flow could not be detected in up to three arteries in the affected (ipsilateral) orbit of 6 GCA patients at presentation. Five of these patients were also found to have undetectable blood flow in the posterior ciliary arteries of the contralateral orbit. Serial CDI examination revealed blood flow alterations in arteritic patients despite treatment. Return of blood flow to normal was slow, and related to the clinical features. By contrast, only 1 of the patients with non-arteritic AION showed undetectable blood flow in a posterior ciliary artery. GCA leads to widespread and prolonged alterations in orbital blood flow. CDI allows the detection and monitoring of such alterations in orbital blood flow, which correlate with the clinical features of GCA. Serial CDI examinations in GCA may be used to aid management decisions.

Aged↗
PubMed1996

Colour Doppler ultrasound in renal artery stenosis: intrarenal waveform analysis.

Renal artery stenosis (RAS) is the commonest secondary cause of hypertension and may result in renal ischaemia with resultant renal failure. Recent studies hve suggested that colour Doppler ultrasound, with spectral analysis of the intrarenal waveforms, can identify those patients with a significant RAS. A prospective study was performed in which colour Doppler ultrasound was compared with angiography in 73 patients (143 kidneys) presenting for renal angiography. Colour Doppler ultrasound was unsuccessful in 16% of kidneys due to a combination of technical failures and small kidney size. Accessory renal vessels were present in 14% of kidneys on angiography but none was detected by ultrasound. Of the 120 kidneys that had both examinations, no significant difference in intrarenal pulsatility or resistive index was noted between the angiographically stenosed and normal arteries. There were significant differences for intrarenal peak and end diastolic velocities, and acceleration time and index. Of these measurements, acceleration time was the best indicator of RAS. The probability of detecting a high grade RAS in an individual patient did not reach 90% until the acceleration time was prolonged to more than 0.12 s. Intrarenal colour Doppler ultrasound is not a general screening test for RAS and it should be reserved for selected patient groups where the incidence of disease is high. Patients with prolonged acceleration times of more than 0.12 s have a high likelihood of at least 70% RAS and should proceed directly to angiography.

Adult↗
PubMed1995

A comparison of colour Doppler imaging of orbital vessels and other methods of blood flow assessment.

BACKGROUND: Comparison of the haemodynamic measurements obtained by colour Doppler imaging and other methods of ocular blood flow measurements was desired. METHODS: The blood velocity findings from colour Doppler imaging of patients with central retinal vein occlusion were compared to the results of fluorescein video-angiography, continuous tonography and ophthalmodynamometry. RESULTS: Patients with low or undetectable blood velocities in the central retinal vein had longer retinal dye transit times on fluorescein video-angiography. Tonography showed a positive correlation with the velocities in the ophthalmic artery, but ophthalmodynamometry showed a negative correlation with these velocities. CONCLUSION: The relationships between the blood velocities in orbital vessels and other blood flow measurements emphasise that there is a complex interaction of the blood flow parameters. Care must therefore be taken when interpreting the results of studies.

Aged↗
PubMed1995

Colour Doppler ultrasound in renal transplant artery stenosis: which Doppler index?

A prospective study comparing colour Doppler ultrasound (US) with the 'gold standard' of intra-arterial digital subtraction angiography in the evaluation of renal transplant artery stenosis was performed. Both the intrarenal vessels and the transplant renal artery were examined by Doppler US. Diagnostic arteriography was performed only if, on Doppler, the peak systolic velocity in the transplant renal artery exceeded 1.5 ms-1. Of 109 patients, the transplant artery could not be visualized using colour Doppler US in three, and these were omitted from statistical analysis. Of the remaining 106 patients, 31 had a peak systolic velocity greater than 1.5 ms-1 in the transplant renal artery and were referred for DSA. Of the multiple renal Doppler indices recorded, the peak systolic velocity in the transplant artery was the best discriminating measurement for the detection of renal artery stenosis. A peak systolic velocity of > or = 2.5 ms-1 in the transplant renal artery had a sensitivity of 100% and a specificity of 95% for the detection of renal artery stenosis ( > 50% diameter reduction). Although a significant difference in Pulsatility Index, Resistive Index, Acceleration Index and Acceleration Time was recorded from the intrarenal vessels in the angiographically normal and stenosed groups with Doppler, these measurements were less useful as discriminating diagnostic tests. In conclusion, the peak systolic velocity in the transplant renal artery is the most sensitive Doppler criterion for renal artery stenosis and is sensitive and specific enough to be used as a screening test. The intrarenal acceleration time and index should not be used in isolation.

Angiography, Digital Subtraction↗
PubMed1995

Renal transplant vein occlusion: an early diagnostic sign?

We report new Doppler ultrasound findings in two patients with renal vein thrombosis and obstruction following renal transplantation. In both cases there was a marked reduction in the systolic peak with relatively normal diastolic flow in the intrarenal arterial waveforms. Venous flow was still detectable at the renal hilum in both cases, and throughout the graft in one case. We suggest that, in the absence of signs of proximal renal artery stenosis, small amplitude arterial waveforms with a depressed systolic peak and maintained diastolic flow, despite intrarenal venous flow, represent renal vein thrombosis in evolution or renal vein obstruction. These findings merit early surgical exploration.

Adult↗
PubMed1995

Influence of age, systemic blood pressure, smoking, and blood viscosity on orbital blood velocities.

The influence of multiple systemic factors upon the blood velocities obtained from the orbital circulations was investigated. The velocities obtained by colour Doppler imaging from the ophthalmic artery, central retinal artery, and vein from 95 ophthalmologically healthy volunteers were analyzed. The effects of age, systemic blood pressure, and smoking habit were examined. In 24 volunteers blood viscosity was also measured and its relation with blood velocity assessed. Age was weakly negatively correlated with the blood velocities in the ophthalmic artery and weakly positively correlated with resistance to flow in the retinal circulation. Systolic blood pressure showed a positive correlation with the peak systolic velocities in the arteries while cigarette smoking was associated with lower ophthalmic artery velocities. Increased haematocrit and viscosity were positively correlated with resistance to flow proximal to the ophthalmic artery and red cell rigidity negatively correlated with the pulsatility of flow in the retinal vein. These results help to identify the roles of systemic conditions in the ocular circulation. The influence of blood viscosity on retinal venous flow may be relevant to the pathogenetic mechanisms of conditions such as central retinal vein occlusion.

Age Factors↗
PubMed1995

Color Doppler imaging of the eye: normal ranges, reproducibility, and observer variation.

Color Doppler ultrasonography has numerous potential applications in the diagnosis and monitoring of many ocular disease processes. One of its advantages over other investigative and diagnostic tests is its safety and repeatability. To be able to fully assess this technique it is important to have good control data and to know the reproducibility of the technique for each of the retrobulbar vessels. Color Doppler ultrasonography was performed on 80 volunteers, and normal ranges of blood velocity were calculated for the ophthalmic artery and for the central retinal artery and vein. Reduction in the peak systolic and end diastolic velocities in the ophthalmic artery and an increase in resistive index in the central retinal artery and vein were noted with advancing age. With regard to reproducibility of the retrobulbar vessels, 15 healthy persons were chosen at random and intra- and interobserver studies performed. The most reliable and reproducible vessels were the ophthalmic artery and central retinal artery and vein. Greater variation was noted in the posterior ciliary vessels, whereas the superior ophthalmic and vortex veins were unreliable in both detection and velocity measurement. The results provide normal ranges for future studies and demonstrate that reproducible results can be obtained for the orbital vasculature using color Doppler imaging.

Adult↗
PubMed1995

Abnormalities in oxygenation, coagulation, and fibrinolysis in colonic blood of horses with experimentally induced strangulation obstruction.

OBJECTIVE: To measure arterial and venous blood gas, coagulation, and fibrinolysis variables in blood from isolated segments of control and ischemic large colons for the purpose of identifying variables for rapid, indirect assessment of colonic mucosal injury. DESIGN: Variables were determined at specific intervals during the 4-hour study (3 hours of ischemia and 1 hour of reperfusion). ANIMALS: Seven clinically normal horses between 2 and 15 years old. PROCEDURES: Horses underwent laparotomy and occlusion of the lumen and vasculature of the mid-portion of the pelvic flexure of the large colon. During ischemia of 1 randomly-chosen colonic segment, variables were measured to determine colonic mucosal damage and were compared with histologic scores of colonic biopsy specimens. RESULTS: Significant (P < 0.05) differences from control values were observed over time for venous pH, PCO2, PO2, oxygen saturation, oxygen content, arteriovenous oxygen difference, and lactate and glucose concentrations. Mean histologic scores of biopsy specimens obtained from ischemic colons were significantly (P < 0.05) greater (indicating greater damage) than those from control colons, and increased significantly (P < 0.05) with duration of ischemia. CONCLUSIONS: Venous lactate, oxygen saturation, and PO2 values were the most significant predictors of the severity of histologic damage within the ischemic colons (R2 = 0.661). CLINICAL RELEVANCE: Venous blood gas and lactate values in the large colon are good predictors of the amount of intestinal damage incurred during 3 hours of ischemia, and may be clinically useful for the rapid determination of colonic viability.

Animals↗
PubMed1994

Variance mapping in colour flow imaging: what does it measure?

Flow disturbance is known to occur in association with high grade carotid stenosis and cause spectral broadening and fluttering in the Doppler spectral waveform distal to the stenosis. Colour flow variance mapping has been proposed as a means of documenting its presence. We prospectively evaluated this hypothesis by studying 15 patients with high grade (> 50%) stenotic lesions in the internal carotid artery. In all 15 cases, the site of increased variance on the colour Doppler map corresponded to the point of maximum velocity. In 10 cases of greater than 75% stenosis, the point of aliasing on the traditional colour Doppler map and the site of maximal variance occurred at the stenotic jet (length 7.3 +/- 2.3 mm) and not along the full length of disturbed flow (19.3 +/- 5.5 mm). In five patients with stenoses between 50-75% diameter narrowing, decreasing the colour Doppler pulse repetition frequency (PRF) created a region of abnormal variance corresponding to the site of aliasing. In all 15 stenoses, the site of maximum flow disturbance, defined as fluttering in the Doppler spectral waveform, was not apparent on the variance map. We conclude that the variance map does not reflect flow disturbance and is most likely to occur at sites of aliasing.

Aged↗
PubMed1994

Colour Doppler sonography of femoral vein stenosis: a report of three cases.

Colour Doppler sonography (CDS) is becoming an increasingly popular method of examining the deep venous system of the lower limb, particularly in the investigation of possible deep venous thrombosis (DVT). We describe a further application of CDS observed in three intravenous (i.v.) drug abusers who presented with symptoms mimicking a DVT. All three cases had femoral vein stenosis occurring at their injection site. This was demonstrated by CDS and at the same time DVT excluded.

Adult↗
PubMed1994

Central retinal vein occlusion, an investigation by color Doppler imaging. Blood velocity characteristics and prediction of iris neovascularization.

PURPOSE: To determine pulsatile blood velocities in the orbital vasculature in patients with central retinal vein occlusion (CRVO). METHODS: The ophthalmic artery, central retinal artery, and vein of 80 patients with CRVO and 95 control subjects were investigated by color Doppler imaging. The patients were examined by ophthalmoscopy, relative afferent pupillary measurement using cross-polarized filters, fundus fluorescein angiography, and electroretinography to estimate the degree of retinal ischemia. RESULTS: Blood flow velocities in the central retinal vein and artery of eyes with CRVO were significantly lower than in fellow eyes and controls. The measurements from the vein were most reduced and in some cases absent in those eyes with "ischemic" CRVO. Velocities also were reduced in the central retinal artery of the affected eyes, but no correlation with "ischemia" was detected. The risk of iris neovascularization in patients examined within 3 months of onset of CRVO can be determined from the flow velocities with a high degree of predictability (75% sensitivity and 86% specificity). CONCLUSIONS: Blood velocity was reduced in the retinal circulation of patients with CRVO and reduced even further in the "ischemic" variant of CRVO. The results indicate that noninvasive color Doppler imaging could play a major part in the routine assessment of patients with CRVO within 3 months of onset.

Adult↗