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Biomedical subjects

G M Baxter

Publications and source records attributed to G M Baxter.

At least 19 recordsLinked to original sources
PubMed1998

Evaluation of digital and laminar blood flow in horses given a low dose of endotoxin.

OBJECTIVE: To measure blood flow in the palmar digital artery and laminae corium, using ultrasonic and laser Doppler flowmetry, respectively. ANIMALS: 6 healthy horses. PROCEDURE: Digital blood flow and laminar perfusion, respectively, were measured by placing a flow probe around the palmar digital artery and a laser Doppler flow probe in a hole in the dorsal aspect of the hoof wall. All horses were given saline (0.9% NaCl) solution (1 L, IV, during a 30-minute period). Seven days later, each horse was given endotoxin (0.1 microgram/kg of body weight, IV, in 1 L of saline solution, during a 30-minute period). Digital blood flow, laminar perfusion, heart and respiratory rates, body temperature, and clinical signs of endotoxemia were recorded throughout a 240-minute period. Repeated-measures ANCOVA was used to evaluate changes in outcome variables. RESULTS: Treatment with saline solution did not cause a change in measured variables. All horses had mild clinical signs of endotoxemia. Endotoxin treatment caused a significant decrease in digital blood flow and increases in heart rate and body temperature. Laminar perfusion decreased after endotoxin treatment. CONCLUSIONS: Endotoxin administration caused a profound transient decrease in digital blood flow and a less substantial decrease in laminar perfusion. CLINICAL RELEVANCE: Horses with clinical endotoxemia were likely to have decreased digital blood flow and possibly, decreased laminar perfusion, potentially predisposing them to vascular alterations within the digits.

Animals↗
PubMed1998

Effects of 6alpha-methylprednisolone acetate on an equine osteochondral fragment exercise model.

OBJECTIVE: To determine effects of intra-articularly administered 6alpha-methylprednisolone acetate (MPA) in exercised horses with carpal osteochondral fragmentation. ANIMALS: 18 horses: 3 groups of 6 each. PROCEDURE: An osteochondral (chip) fragment was created in 1 randomly chosen middle carpal joint of each horse. Polyionic fluid (PF) was injected into both middle carpal joints of horses in the control group. In horses of the MPA-control group, MPA was injected into the middle carpal joint without an osteochondral fragment; a similar volume of PF was injected into the contralateral middle carpal joint. In the MPA-treated group of horses, 100 mg of MPA was injected into the middle carpal joint containing the osteochondral fragment; a similar volume of PF was injected into the contralateral joint. Injections were administered on postsurgical days 14 and 28, and horses were exercised on a high-speed treadmill for 8 weeks, starting on postsurgical day 15. RESULTS: Clinical improvement in degree of lameness was not associated with MPA administration. Joints that contained an osteochondral fragment and were treated with MPA had lower prostaglandin E2 concentration in synovial fluid, and lower scores for intimal hyperplasia and vascularity in synovial membrane, compared with PF-treated joints. However, articular cartilage erosion and morphologic lesions suggested possible deleterious effect of intra-articular MPA administration. CONCLUSIONS: Some beneficial effects of MPA administration on synovial fluid and synovial membrane were identified; however, the deleterious findings contrast with those associated with triamcinolone acetonide used in a similar model, but agree with other results of MPA administration in normal and abnormal joints.

Animals↗
PubMed1997

Survey of diplomates of the American College of Veterinary Surgeons regarding postoperative intra-abdominal adhesion formation in horses undergoing abdominal surgery.

OBJECTIVE: To obtain information from specialists in equine surgery as to prevalence of, predisposing factors for, and methods to prevent postoperative adhesion formation in horses undergoing abdominal surgery. DESIGN: Survey. PROCEDURE: Surveys were mailed to 196 diplomates of the American College of Veterinary Surgeons involved in equine practice. RESULTS: 60 (31%) surveys were returned. Most respondents (55/60) routinely informed clients of the risk of postoperative adhesion formation in horses with small intestinal lesions. When asked after which procedures they routinely used measures to prevent adhesions, 56 of 60 (93%) indicated that they did after small intestinal resection and anastomosis and 56 of 60 (93%) indicated that they did after any abdominal surgery in foals. The 4 methods most frequently listed when respondents were asked which methods were effective at preventing adhesion formation were meticulous surgical technique, administration of antibiotics and nonsteroidal anti-inflammatory drugs, intraoperative peritoneal lavage, and methods that prevent abdominal contamination. Most respondents (50/60) thought that at least some horses with colic secondary to adhesion formation could be managed medically. Fifty-four (90%) respondents indicated that they were successful less than half of the time when treating horses with adhesions severe enough to require additional surgery. CONCLUSION: In general, respondents thought that less than 15% of horses undergoing abdominal surgery would develop adhesions, but that horses with small intestinal disease and foals were most prone to develop adhesions. Meticulous surgical technique was thought to be the most important factor in preventing adhesions, and many prevention regimens reported to be effective in the literature were not commonly used in practice.

Abdomen↗
PubMed1997

Effect of renal-artery stenting on progression of renovascular renal failure.

BACKGROUND: Placement of renal-artery stents has a high technical success rate in atherosclerotic renovascular disease, but little is known about the clinical benefits of the procedure. We monitored renal function serially before and after stent insertion in patients with renovascular renal failure. METHODS: Renal function was assessed before and after stent placement by means of serial serum creatinine values in 32 patients with atherosclerotic renal-artery stenosis. The effect on the progression of renal failure was analysed in 23 patients by comparison of the reciprocal slopes of serum creatinine versus time plots before and after stent placement. FINDINGS: 33 transluminal stents were placed in 32 patients with atherosclerotic renovascular disease. Immediate patency was achieved in all cases: the angiographic restenosis rate at 6 months was 12% (n = 24). One patient died after a procedure-related haemorrhage. Median diastolic blood pressure was significantly lower after stenting than before (95 [IQR 86-103] vs 87 [81-90] mm Hg; p > 0.01) but the requirement for antihypertensive drugs was unchanged. Renal function improved or stabilised in 22 (69%) of the 32 patients. Progression of renal failure was significantly slowed after the procedure; the mean (SE) of the slopes of reciprocal serum creatinine values was -4.34 (0.85) L mumol-1 day-1 before stent placement, and -0.55 (1.0) L mumol-1 day-1 after stent placement (p < 0.01, two-sample t test). INTERPRETATION: Renal-stent placement in selected patients slows the progression of renovascular renal failure and may delay the need for renal replacement therapy.

Aged↗
PubMed1997

Renal artery stent placement in renal artery stenosis: technical and early clinical results.

We report the technical and early clinical results of renal artery stent placement in 29 consecutive patients treated at a single centre over a 30-month period, employing the Palmaz balloon-expandable stent. Of 32 arteries treated, 23 (72%) were atheromatous, ostial stenoses. Immediate technical success was achieved in all 29 patients. Follow-up angiography was performed on 25 patients at 6.7 months (mean) and demonstrated a patient restenosis rate of 16%. All surviving patients were followed up for a minimum of 6 months. Blood pressure control was improved in eight (50%) of hypertensive patients, and renal function improved in seven (33%) and stabilized in six (29%) patients with chronic renal impairment (serum creatinine > 150 mumols/l). Complications occurred in seven (24%) of patients, including one procedure-related death. Our experience indicates that stent placement has an initial high technical success rate in renal artery stenosis and that this patency is maintained at repeat angiography with a low restenosis rate. Renal artery stenting is likely to extend the role of percutaneous renal revascularization especially in atheromatous ostial lesions. A randomized trial will be required to evaluate its role compared with balloon angioplasty.

Adult↗
PubMed1997

Technical report: an alternative mechanical technique of pseudoaneurysm compression therapy.

Graded manual compression therapy under ultrasound guidance has become the standard first line treatment of post-catheterization femoral pseudoaneurysms. Although effective, this treatment is often poorly tolerated by both patient and operator. We describe a new mechanical technique which has proven successful in our department, and is well tolerated by both patients and staff.

Aged↗
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↗