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Biomedical subjects

G M Baxter

Publications and source records attributed to G M Baxter.

At least 55 records · Page 3Linked to original sources
PubMed1994

Acute laminitis.

Laminitis is an inflammation of the sensitive laminae along the dorsal aspect of the digit and is considered to be a secondary complication of several predisposing or primary factors. Affected horses are usually very lame, have increased digital pulses, are painful to hoof testers along the toe of the foot, and have evidence of downward rotation or distal displacement of the distal phalanx present on radiographs. Treatments for acute laminitis include anti-inflammatory drugs, anti-endotoxin therapy, vasodilators, antithrombotic therapy, corrective trimming and shoeing, and surgical procedures. Treatment regimens are very controversial and the true efficacy of these treatments is unknown. The quality of laminae damage that occurs with laminitis, however, probably has greater influence on the success of treatment and outcome of the horse than the treatment regimen itself.

Acute Disease↗
PubMed1993

Extensor tendon lacerations in horses: 50 cases (1982-1988).

Medical records of 50 horses with extensor tendon lacerations affecting 53 limbs over 7 years (1982 to 1988) were reviewed to determine the clinical features and prognosis for athletic soundness after treatment. Mean and median ages were 4.8 and 3 years, respectively. Eighty-nine percent of the injuries involved the hind limbs, with approximately equal distribution between the right and left limbs. Hind limb lacerations involved the long digital extensor tendon (28 limbs), lateral digital extensor tendon (3 limbs), or both tendons (16 limbs). Forelimb lacerations involved the common digital extensor tendon (2 limbs), lateral digital extensor tendon (1 limb), or both tendons (3 limbs). Joint involvement was found in 6 cases. Wound management varied according to wound characteristics, financial constraints of owners, and clinician preference. External coaptation consisted of a 3-layered cotton bandage in 33 limbs, splint and cotton bandage in 12 limbs, fiberglass or plaster-of-Paris cast in 5 limbs, and no form of coaptation in 3 limbs. Follow-up information for 40 cases at least 1 year after injury revealed that 29 (73%) horses had returned to athletic soundness, 7 (18%) horses were pasture sound, 3 horses were chronically lame, and 1 horse was euthanatized during treatment because of wound sepsis. Depending on the hind limb tendons involved, return to athletic soundness ranged from 62% (long digital and lateral digital extensor tendons lacerated) to 80% (long digital extensor tendon lacerated) The small number of forelimb lacerations precluded any comparative data.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Lower limb colour flow imaging: a comparison with ankle: brachial measurements and angiography.

Peripheral lower limb vascular disease represents a substantial health problem. Arteriography is currently the 'gold standard' imaging modality. However, much effort is presently being channeled towards alternative non-invasive techniques. To date, this involves mainly the interpretation of ankle: brachial pressure indices and segmental pressure measurements. A prospective pilot study of 20 patients (40 limbs) comparing these two techniques with colour Doppler ultrasound was carried out. Although ankle: brachial indices could accurately predict disease (sensitivity 100%, accuracy 92.5%), it failed to localize it; neither a high thigh: brachial index nor segmental drop could localize disease to the iliac (accuracy 70%) or femoro-popliteal (accuracy 55%) vessels respectively. Colour Doppler ultrasound correctly differentiated iliac from femoro-popliteal disease. It had an overall diagnostic accuracy of 90% in the femoral and popliteal vessels for both occlusion and stenosis and diagnosed 10 of 11 iliac lesions. Colour Doppler ultrasound has many advantages over pressure measurements in that it can both diagnose and localize arterial lesions accurately. We feel that using both techniques prior to angiography can accurately separate patients into either a surgical or angioplasty group. This may help utilize angiographic resources and radiologists' time more efficiently as well as reducing radiation dose to both patients and staff.

Adult↗
PubMed1993

Color Doppler velocimetry of the optic nerve head in arterial occlusion.

BACKGROUND: Color Doppler velocimetry allows simultaneous imaging by B-scan and Doppler ultrasound. This facilitates estimation of blood velocity in the orbital vessels. A pulse arterial waveform providing blood velocity measurements can be obtained from the optic nerve head. The vascular pattern in this region consists of multiple peripapillary blood vessels and a central artery. The exact contribution of the arteries in this area to velocimetry readings was undetermined. METHODS: In this study, the arterial pulses at the optic nerve head of seven patients with central retinal artery occlusion (CRAO) and seven with anterior ischemic optic neuropathy (AION) were examined by color Doppler velocimetry. RESULTS: No velocimetric measurements were obtainable at the optic nerve head in three of four patients with acute CRAO (examined within 24 hours of onset) despite color recordings obtainable in the peripapillary region. In contrast, all patients with AION showed characteristic arterial pulse waveforms from the artery that was situated centrally in the optic nerve. No peripapillary color indices were detectable in three of the four patients with ischemic optic neuropathy who were examined within 24 hours of onset of their symptoms. Follow-up investigation showed that there was reperfusion of both arterial circulations within 1 week. CONCLUSION: The results demonstrate that color Doppler ultrasound of the optic nerve head provides velocimetric measurements of blood flow in the central retinal artery. Although some investigators using different apparatuses have produced velocimetry measurements from the posterior ciliary arteries, in this study reliable measurements were not obtainable form color indices in the peripapillary area.

Aged↗
PubMed1993

Colour Doppler velocimetry of the arterial vasculature of the optic nerve head and orbit.

Blood flow in the orbital vasculature can be investigated by colour Doppler velocimetry which allows simultaneous imaging of B-scan and Doppler ultrasound. In this paper we review the results of our recent studies on the arterial vasculature of the orbit and optic nerve head. A control study is described in which reliable measurements were obtained from the ophthalmic artery at the orbital apex, the medial orbit, and the complex of the central retinal artery and posterior ciliary arteries. Patients with occlusion of the central retinal artery and posterior ciliary arteries were examined. The results indicate that readings at the optic nerve head primarily represent blood flow in the central retinal artery. A study of the effects of posture on velocimetry demonstrated no change in the measurements obtained. Finally, topical timolol 0.5% was found to reduce the resistive indices of flow in the central retinal artery.

Adult↗
PubMed1993

Color Doppler flow imaging in central retinal vein occlusion: a new diagnostic technique?

Central retinal vein occlusion (CRVO) is a common cause of sudden visual loss and can occur at any age. Accurate diagnosis is essential, as differentiation of ischemic and nonischemic forms of the disease has prognostic importance. The introduction of color Doppler flow ultrasound has, for the first time, allowed visualization of the retrobulbar vessels; the central retinal artery and vein are easily identifiable. The authors conducted a prospective, blinded trial and compared images and waveforms from 20 patients with CRVO with those from 20 age-matched healthy volunteers. No difference in velocity indexes from the central retinal artery was detected between the patients' affected and unaffected eyes or between the affected eyes and control eyes. A marked reduction in venous velocity was recorded in the central retinal vein in the affected eyes when compared with that of the unaffected patient and control eyes. There was no difference in venous flow between the unaffected patient and control eyes. These initial results suggest that color Doppler flow imaging may have a role in the diagnosis of CRVO. Color Doppler flow imaging is non-invasive, is easy to perform, is well tolerated by patients, and allows temporal assessment.

Aged↗
PubMed1993

Evaluation of occlusive dressings for management of full-thickness excisional wounds on the distal portion of the limbs of horses.

Two 2.5-cm2 full-thickness skin wounds were created surgically over the lateral aspect of the cannon bone of each limb of 6 horses (n = 48 wounds). Dressings evaluated were a nonadherent gauze pad (group 1); a synthetic semiocclusive dressing, (group 2); equine amnion (group 3); and a synthetic fully occlusive dressing (group 4). Wounds were assessed subjectively at each dressing change, and total wound area, area of granulation tissue, and area of epithelium in each wound were determined by computerized digital analysis of photographs of the wounds. Complete healing time (wound covered by epithelium) also was determined for each wound. Statistical comparisons were made, using Kruskal-Wallis analysis and a Mann-Whitney U test. Median time to complete healing was: group 1, 53 days; group 2, 71 days; group 3, 63 days; and group 4, 113 days. Time to complete healing was significantly longer for wounds of group-4 horses than all other groups, and wounds of group-1 horses healed faster than did those of group-2 horses (P < 0.05). Wounds in group-4 horses required significantly (P < or = 0.05) more excisions of granulation tissue (median, 11.5 times) than did those in group-1 (median, 3.5), group-2 (median, 5.5) or group-3 (median, 2.5) horses. Epithelial tissue was detected later in wounds of group-4 horses (median, 27 days) than in wounds of horses in groups 1, 2 or 3 (median, 17 days); however, this difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Treatment of a mandibular bone cyst by use of a corticocancellous bone graft in a horse.

A 1-year-old Appaloosa stallion had a mass on the right rostral hemimandible. The mass was firm, did not cause signs of pain, and was identified as a bone cyst by radiography and biopsy. Surgical correction included curettage of the cystic cavity and grafting the defect with both cortical and cancellous bone. By 5 months, the cystic cavity was ossifying; continued remodeling with an increase in bone density was apparent 22 months after surgery.

Animals↗
PubMed1992

Septic metritis secondary to torsion of a pedunculated uterine fibroleiomyoma in a filly.

A 2-year-old Arabian filly was referred for evaluation of a serosanguineous vaginal discharge. Palpation per rectum revealed a large, fluid-filled uterus and a uterine mass. The filly developed septic metritis and secondary laminitis as a result of torsion and necrosis of a pedunculated uterine mass. Ovariohysterectomy was performed. The entire cervix was removed with the uterus. Gross examination of the excised uterus revealed 3 intraluminal masses. Histologic evaluation identified the tumors as fibroleiomyoma. The filly recovered completely, and there was no recurrence of the tumor.

Animals↗
PubMed1992

Tension-band wiring and lag screw fixation of a transverse, comminuted fracture of a patella in a horse.

A transverse, comminuted fracture of the patella was treated surgically by combining tension-band wiring and lag-screw fixation in a horse. Partial patellectomy or smaller detached fragments of the patella was performed. Satisfactory healing of the fracture was evident 10 weeks after surgery, and there were no complications. Implants were not removed. The horse was sound at a trot 4 months after surgery and was used for pleasure riding 8 months later.

Animals↗
PubMed1992

Uroperitoneum attributable to ruptured urachus in a yearling bull.

Ruptured urachus was found to result in uroperitoneum in a yearling Beefmaster bull. The uroperitoneum was initially believed to be attributable to ruptured bladder secondary to urolithiasis; however, catheter decompression of the bladder through an ischiatic urethrotomy did not resolve the uroperitoneum. The persistent urachus was diagnosed and removed through caudal right flank laparotomy with the bull standing. The urachus was attached to the umbilicus, communicated with the lumen of the bladder, and had a mucosal lining. Ruptured urachus is an unusual cause of uroperitoneum, but can cause clinical signs identical to those of ruptured bladder. Persistent urachus is a congenital abnormality in many species, but may be hereditary in Beefmaster cattle. In addition, the bull in this report developed hyperkalemia, which is considered an unusual finding in cattle with uroperitoneum.

Animals↗
PubMed1992

Calf vein anatomy and flow: implications for colour Doppler imaging.

Early experience has suggested that colour flow Doppler ultrasound may have a diagnostic role in calf vein thrombosis. Before its accuracy within the calf can be adequately assessed, normal calf vein flow and anatomy needs to be understood. We, therefore, studied 40 normal volunteers, age range 24-75 years (mean 45.4), M:F 22:18, and assessed both flow and venous diameter in each of the three sets of calf veins in the supine and erect positions and once again in both these positions following the application of an above knee band. Paired sets of veins were present in all posterior tibial and common peroneal sets, but in only 85% of the anterior tibial group. Significant flow variations were present between different sets of veins, there being relatively less appreciable flow within the common peroneal (p < 0.05). Both band application and erect posture produced significant increases in venous diameter (p < 0.01, p < 0.001) in the posterior tibial and common peroneal veins, aiding visualization but at the cost of reducing flow following band application (p < 0.05, p < 0.01). The erect posture had no deleterious effect on calf vein flow. We, therefore, recommend that when the patency of calf veins is being assessed scanning should be performed in both a supine and erect position as this will help vein visualization without a reduction in flow, and thus avoid misinterpretation.

Adult↗
PubMed1992

Colour flow imaging of calf vein thrombosis.

Ultrasound and more recently colour Doppler ultrasound has been successfully used in the diagnosis of lower limb venous occlusive disease. Colour Doppler ultrasound has shown promise in the diagnosis of calf vein thrombosis but to date there has been no prospective trial to specifically evaluate its potential. In view of this, we carried out a prospective trial of 50 patients comparing the accuracy of colour Doppler ultrasound with venography in the diagnosis of deep venous thrombosis both above and below knee but in particular with respect to the detection of calf vein clot. Of the 50 patients studied, 10 had only one imaging modality performed as there were eight venographic failures and two ultrasonic failures. Comparison was only thus possible in 40 cases. As in previous studies, colour Doppler ultrasound was shown to be accurate in the diagnosis of thrombosis within the femoro-popliteal veins and had a sensitivity and specificity of 100% respectively. With respect to calf vein lesions, there was one false negative scan using the ultrasonic technique giving a sensitivity of 95%, specificity of 100% and accuracy of 97.5%. We feel colour Doppler ultrasound can and should be used as a first line alternative to venography and can be employed for the exclusion of both above and below knee deep venous thrombosis. Venography should now be reserved for those patients who are unsuitable for ultrasound examination or who have an equivocal ultrasound scan.

Adult↗
PubMed1992

Color Doppler ultrasound of orbital and optic nerve blood flow: effects of posture and timolol 0.5%.

Color Doppler ultrasound allows simultaneous imaging with real-time ultrasound and superimposed color-coded vascular flow, allowing visualization of vessels previously beyond the resolution of conventional imaging, such as those in the orbit. With this technique, 20 healthy volunteers were studied. Three regional vessels named 1, 2, and 3 were identified. No significant difference in maximum or minimum blood velocity or resistive index was detected between vessels 1 and 2, although significant differences were noted between both these vessels and vessel 3 (P less than 0.01 and P less than 0.001, respectively). These regional variations are unaffected by small but significant rises in pulse (P less than 0.05) and diastolic blood pressure (P less than 0.01) induced by postural change. No significant change within each vessel was recorded in response to posture, reflecting autoregulation within these vessels. Using a similar technique, 10 healthy volunteers were studied at baseline and at 2 hr and 3 d following the unilateral instillation of 0.5% timolol eye drops. A fall in resistive index was recorded in vessel 3 for both eyes (P less than 0.05, timolol administered eye; P less than 0.01 timolol-free eye). This effect was independent of any simultaneous fall in intraocular pressure that occurred only in the eye receiving timolol drops (P less than 0.01). These results support the presence of B receptors in the vessels at the optic nerve head (vessel 3). A fall in resistive index should not compromise the blood supply in this region, and may even increase it.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1991

Repair of an open radial fracture in an adult horse.

An open radial fracture in an adult horse (450 kg) was repaired by internal fixation, using two 18-hole 4.5-mm broad dynamic compression plates and 5.5- and 4.5-mm bone screws. The fracture healed completely, but when evaluated 9 months after surgery, the horse was lame on the fractured limb at a trot. Local infiltration of anesthesia along the distal half of the bone plates greatly ameliorated the lameness, suggesting that the plates were irritating the soft tissues and extensor tendons along the cranial and lateral aspects of the antebrachium. Both bone plates were removed simultaneously with no complications, and the horse became sound.

Animals↗