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in Journal of the American Veterinary Medical Association

Abstract

Objective—To establish the incidence of and risk factors for seizures following myelography performed with iohexol in dogs.

Design—Retrospective case series.

Animals—503 dogs.

Procedures—Medical records were searched for dogs that underwent myelography between April 2002 and December 2004. Data extracted included body weight, breed, age, sex, volume and dose of iohexol, site of injections, location of lesion, duration of anesthesia, surgical procedures immediately after myelography, use of acepromazine, and presence or absence of seizures.

Results—15 (3%) dogs had postmyelographic seizures. Risk factors significantly associated with seizures were size of dogs (large dogs were 35.35 times as likely to have seizures as were small dogs), location of contrast medium injection (dogs in which iohexol was injected into the cerebellomedullary cistern were 7.4 times as likely to have seizures as were dogs in which iohexol was injected into the lumbar cistern), location of lesion (dogs with lesions at the level of the cervical portion of the vertebral column were 4.65 times as likely to develop seizures as were dogs with lesions in other regions), and total volume of iohexol. Mean ± SD total volume of iohexol was 11.73 ± 5.52 mL (median, 10.5 mL [range, 3.0 to 21.0 mL]) for dogs that had seizures and 4.57 ± 4.13 mL (median, 3.5 mL [range, 0.75 to 45.0 mL]) for those that did not.

Conclusions and Clinical Relevance—Large-breed dogs with cervical lesions and large volumes of iohexol injected into the cerebellomedullary cistern had the highest risk of seizures. The use of contrast medium volumes > 8 mL in large dogs should be avoided, with preference given to injections into the lumbar cistern.

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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Objectives

To determine radiation exposure to personnel during fluoroscopic imaging of limbs of horses with a portable unit and to determine distance from the c-arm at which radioprotective clothing is not required.

Design

Repeated-measures cohort study.

Sample Population

Part 1, 1 forelimb and 1 hind limb from each of 5 equine cadavers; parts 2 and 3, personnel involved during imaging of limbs of 5 and 9 horses, respectively.

Procedure

Radiation exposure rates were mapped around the suspended c-arm of a portable fluoroscopy unit during imaging of various joints of equine cadaver limbs. During similar examinations in live horses, exposure rates to the fluoroscopist and assistant were measured. Mean duration for fluoroscopy of various joints was determined by observing an experienced fluoroscopist. Exposure to fluoroscopists and assistants per examination and per annum was estimated.

Results

Radiation exposure rates were dependent on distance and direction relative to the c-arm and consistently highest on the tube side of the unit. Exposure was significantly greater than background amounts until approximately 4.7 m from the c-arm. During examination of live horses, exposure was highest to the fluoroscopist's hand nearest the tube. Typically, exposure to the fluoroscopist and assistant during carpal examination was 25 to 40 times greater than that for comparable radiographic examination. Annual exposure for fluoroscopists was more than twice the recommended maximum permissible dose.

Conclusions and Clinical Relevance

Fluoroscopic imaging of limbs of horses represents a major source of radiation exposure. Annual maximum permissible doses of radiation will be rapidly exceeded if required radioprotective clothing is not worn. (J Am Vet Med Assoc 1999;215:372–379)

Free access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Objective—To describe and compare the distribution of technetium Tc 99m (99mTc) pertechnate following intraosseous or IV injection (with or without use of a tourniquet) in the distal portion of the forelimb in standing horses.

Animals—4 horses.

Procedure—Each horse received 4 forelimb treatments in random sequence: intraosseous infusion with tourniquet application (IOT), intraosseous infusion without tourniquet application, IV infusion with tourniquet application (IVT), and IV infusion without tourniquet application. Dynamic nuclear scintigraphic imaging of the third metacarpal bone, proximal and middle phalanges, and distal phalanx was performed from the start of each treatment until 1 hour after infusion was completed. Radionuclide activity was compared within and between treatment groups.

Results—Tourniquet application was necessary to maintain high levels of radionuclide activity in the distal portion of the forelimb after intraosseous or IV infusion with 99mTc pertechnate; IVT and IOT treatments resulted in similar radionuclide activity in the proximal and middle phalanges and distal phalanx. Of the 4 treatments, there was significantly higher radionuclide activity in the distal aspect of the third metacarpal bone after the IOT treatment.

Conclusions and Clinical Relevance—By use of a tourniquet, radionuclide administration via the intraosseous or IV routes resulted in effective perfusion of the distal portion of the forelimb and similar distribution of the agent in the phalanges of horses. Further studies are required to ascertain whether these findings apply to delivery of therapeutic agents in infected tissues via IOT or IVT. (Am J Vet Res 2005;66:1267–1272)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate whether changes in gastric myoelectrical activity in healthy, awake dogs can be detected via multichannel electrogastrography (EGG).

Animals—6 healthy hound-breed dogs.

Procedures—For each dog, 8-channel EGG was performed after food had been withheld for 12 hours and at 30 minutes after subsequent feeding; 60 minutes after feeding, atropine (0.04 mg/kg) was administered IM to induce ileus, and 30 minutes later, EGG was again performed. Mean cycles per minute (cpm) values of the dominant frequency (a measure of the rhythmicity of gastric electrical activity) and mean power ratios (ie, power measured after treatment divided by the power measured when food was withheld) were calculated. Motility of the gastric antrum was assessed via B-mode ultrasonography during the same phases; contractions determined ultrasonographically were correlated with EGG power for each channel in each phase.

Results—The criterion for stability (SD of the dominant frequency < 15% of the cpm value in at least 3 of the 8 EGG channels) was met in 4 of the 6 dogs (only in long-distance channels). The mean power ratios were significantly higher in the postprandial phase than in the ileus phase. Compared with the postprandial phase, significantly fewer contractions per minute were evident ultrasonographically in the ileus and food-withholding phases. There was a significant and good correlation between EGG power and ultrasonographic findings in all 8 channels.

Conclusions and Clinical Relevance—Electrogastrography may be useful in assessing gastric myoelectrical activities in awake dogs with naturally occurring gastrointestinal disease, including gastric dilatation-volvulus.

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in American Journal of Veterinary Research

Abstract

Objective—To compare quantitative magnetic resonance (QMR), dual-energy x-ray absorptiometry (DXA), and deuterium oxide (D2O) dilution methods for measurement of total body water (TBW), lean body mass (LBM), and fat mass (FM) in healthy cats and to assess QMR precision and accuracy.

Animals—Domestic shorthair cats (58 and 32 cats for trials 1 and 2, respectively).

Procedures—QMR scans of awake cats performed with 2 units were followed by administration of D2O tracer (100 mg/kg, PO). Cats then were anesthetized, which was followed by QMR and DXA scans. Jugular blood samples were collected before and 120 minutes after D2O administration.

Results—QMR precision was similar between units (coefficient of variation < 2.9% for all measures). Fat mass, LBM, and TBW were similar for awake or sedated cats and differed by 4.0%, 3.4%, and 3.9%, respectively, depending on the unit. The QMR minimally underestimated TBW (1.4%) and LBM (4.4%) but significantly underestimated FM (29%), whereas DXA significantly underestimated LBM (9.2%) and quantitatively underestimated FM (9.3%). A significant relationship with D2O measurement was detected for all QMR (r 2 > 0.84) and DXA (r 2 > 0.84) measurements.

Conclusions and Clinical Relevance—QMR was useful for determining body composition in cats; precision was improved over DXA. Quantitative magnetic resonance can be used to safely and rapidly acquire data without the need for anesthesia, facilitating frequent monitoring of weight changes in geriatric, extremely young, or ill pets. Compared with the D2O dilution method, QMR correction equations provided accurate data over a range of body compositions.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare quantitative magnetic resonance (QMR), dual-energy x-ray absorptiometry (DXA), and deuterium oxide (D2O) methods for measurement of total body water (TBW), lean body mass (LBM), and fat mass (FM) in healthy dogs and to assess QMR accuracy.

Animals—58 Beagles (9 months to 11.5 years old).

Procedures—QMR scans were performed on awake dogs. A D2O tracer was administered (100 mg/kg, PO) immediately before dogs were sedated, which was followed by a second QMR or DXA scan. Jugular blood samples were collected before and 120 minutes after D2O administration.

Results—TBW, LBM, and FM determined via QMR were not significantly different between awake or sedated dogs, and means differed by only 2.0%, 2.2%, and 4.3%, respectively. Compared with results for D2O dilution, QMR significantly underestimated TBW (10.2%), LBM (13.4%), and FM (15.4%). Similarly, DXA underestimated LBM (7.3%) and FM (8.4%). A significant relationship was detected between FM measured via D2O dilution and QMR (r 2 > 0.89) or DXA (r 2 > 0.88). Even though means of TBW and LBM differed significantly between D2O dilution and QMR or DXA, values were highly related (r 2 > 0.92).

Conclusions and Clinical Relevance—QMR was useful for determining body composition in dogs and can be used to safely and rapidly acquire accurate data without the need for sedation or anesthesia. These benefits can facilitate frequent scans, particularly in geriatric, extremely young, or ill pets. Compared with the D2O dilution method, QMR correction equations provided accurate assessment over a range of body compositions.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To assess the effects of alterations in PaCO 2 and PaO 2 on blood oxygenation level–dependent (BOLD) signal intensity determined by use of susceptibility-weighted magnetic resonance imaging in brains of isoflurane-anesthetized dogs.

Animals—6 healthy dogs.

Procedures—In each dog, anesthesia was induced with propofol (6 to 8 mg/kg, IV) and maintained with isoflurane (1.7%) and atracurium (0.2 mg/kg, IV, q 30 min). During 1 magnetic resonance imaging session in each dog, targeted values of PaCO 2 (20, 40, or 80 mm Hg) and PaO 2 (100 or 500 mm Hg) were combined to establish 6 experimental conditions, including a control condition (PaCO 2, 40 mm Hg; PaO 2, 100 mm Hg). Dogs were randomly assigned to different sequences of conditions. Each condition was established for a period of ≥ 5 minutes before susceptibility-weighted imaging was performed. Signal intensity was measured in 6 regions of interest in the brain, and data were analyzed by use of an ANCOVA and post hoc Tukey-Kramer adjustments.

Results—Compared with control condition findings, BOLD signal intensity did not differ significantly in any region of interest. However, signal intensities in the thalamus and diencephalic gray matter decreased significantly during both hypocapnic conditions, compared with all other conditions except for the control condition.

Conclusions and Clinical Relevance—In isoflurane-anesthetized dogs, certain regions of gray matter appeared to have greater cerebrovascular responses to changes in PaCO 2 and PaO 2 than did others. Both PaO 2 and PaCO 2 should be controlled during magnetic resonance imaging procedures that involve BOLD signaling and taken into account when interpreting findings.

Full access
in American Journal of Veterinary Research