Complications associated with the use of iohexol for myelography of the cervical vertebral column in dogs: 66 cases (1988-1990).

Medical records of 66 dogs that had undergone myelography, using iohexol (240 mg of iodine/ml, 0.3 to 0.5 ml/kg of body weight) during a 2-year period, were reviewed. In 3 dogs, myelography was performed twice during different anesthetic procedures. Neurologic abnormalities were more pronounced the day after myelography in dogs with caudal cervical spondylomyelopathy (P less than 0.01), meningitis (P less than 0.01), or extradural tumors (P less than 0.05). Neither anesthetic regimen nor duration of anesthesia significantly affected the frequency of complications. Seizures occurred after myelography in 6 dogs, and 1 dog had seizures after each of 2 myelographic procedures. The frequency of seizures was significantly greater in male Doberman Pinschers afflicted with caudal cervical spondylomyelopathy. Male dogs (P less than 0.01) and Doberman Pinschers (P less than 0.001) had higher prevalence of seizures. Caudal cervical spondylomyelopathy was associated with higher prevalence of seizures, compared with all other diagnoses (P less than 0.001). Seizures were significantly more prevalent when body weight was greater than or equal to 29 kg (P less than 0.001), when greater than or equal to 2 injections of contrast medium were administered (P less than 0.016), or when 2 injections of contrast medium were given at the cisterna magna (P less than 0.015). The 10% prevalence of seizures after myelography with iohexol in the study reported here is greater than in previous reports, but is lower than that reported after myelography using metrizamide.     

Neurotoxicologic effects of the nonionic contrast agent iopamidol on the leptomeninges of the dog

The effect of iopamidol on the leptomeninges was tested and compared with that of metrizamide and normal saline solution in 18 dogs. Pathologic and clinical effects were evaluated at 24 hours and 14 days after cisternal injection of iopamidol, metrizamide, or normal saline solution. Pathologic changes were evaluated by microscopic examination of serial CSF samples and of sections of brain and spinal cord with the leptomeninges intact. Clinical changes were subjectively evaluated. Electromyograms and EEG were performed on each dog after physical and neurologic examination. There were no changes seen in neurologic status, electromyogram, or EEG in any of the dogs immediately after subarachnoid injection nor at 24 hours or 14 days later. Pathologic changes were limited to mild, moderate, or severe patchy hemorrhagic leptomeningitis seen at 24 hours after iopamidol or metrizamide was injected. The severity of changes were judged to be similar with both these agents. The CSF analysis and histologic evaluation of brain and spinal cord sections revealed a neutrophilic response to iopamidol and a mononuclear response to metrizamide. These findings indicate that iopamidol has minimal neurotoxicologic effect on the leptomeninges and therefore has merit as a myelographic agent.     

A PROSPECTIVE CLINICAL TRIAL COMPARING METRIZAMIDE AND IOHEXOL FOR EQUINE MYELOGRAPHY

A prospective clinical trial comparing adverse postmyelographic effects and myelographic quality of metrizamide and iohexol was conducted. Using a predetermined, randomized assignment, 24 horses exhibiting neurologic signs were administered either metrizamide (180 mgl/ml) or iohexol (180 mgl/ml) via cerebellomedullary puncture. Each horse was evaluated postmyelographically for adverse effects. Myelographic quality was assessed by a numerical scoring method. Adverse effects were observed more frequently with metrizamide (21) compared with iohexol (6) myelography (p < 0.05). Seizures, intensification of preexisting neurologic signs and prolonged anesthetic recovery were the most common complications after myelography. There was no difference in myelographic quality (p > 0.05). We conclude that iohexol is safer than metrizamide for equine myelography and that quality myelograms can be obtained with either contrast medium.     

A COMPARISON OF IOPAMIDOL AND METRIZAMIDE FOR CERVICAL MYELOGRAPHY IN THE DOG

Cervical myelography using iopamidol, a new nonionic contrast medium, was studied in nine dogs. Postmyelographic seizure activity, motor evoked potentials, and rectal temperatures were monitored, and myelographic quality was subjectively evaluated. The results were compared with data from eight dogs that had metrizamide myelography. The iopamidol group had fewer seizures ( p < 0.01) but exhibited no difference in motor evoked potential or rectal temperature recordings. Myelographic quality was similar for iopamidol and metrizamide. The study suggests that iopamidol was less neurotoxic than metrizamide for canine cervical myelography.     

Clinical evaluation of metrizamide as a myelographic agent in the dog.

Metrizamide, a new, water-soluble contrast agent, was clinically evaluated as a myelographic agent in 17 dogs. Nine dogs were given lumbar subarachnoid injections and six were given cisternal injections. Two dogs were given cisternal and lumbar injections; in one dog, both injections were given on the same day. The dosage ranged from 0.3 to 0.57 ml/kg of body weight, using an isotonic solution of metrizamide. Of eight dogs given cisternal injections, two experienced convulsive activity requiring diazepam treatment during the anesthetic recovery period. The lumbar injections did not cause convulsions. Satisfactory radiographic density persisted up to 45 minutes after injection, allowing time for several views to be obtained. In general, metrizamide appeared to be an adequate myelographic agent in the dog.     

IOHEXOL AND IOPAMIDOL MYELOGRAPHY IN THE DOG: A CLINICAL TRIAL COMPARING ADVERSE EFFECTS AND MYELOGRAPHIC QUALITY

In a blind clinical trial, adverse effects after iohexol and iopamidol myelography were evaluated in 151 dogs. Eighty-one dogs were given iohexol (240 mgI/ml) and 70 dogs were given iopamidol (200 mgI/ml) by pre-determined assignment. Each dog was evaluated postmyelographically for seizures, hyperthermia, prolonged recovery from anesthesia and intensification of pre-existing neural signs. Myelographic quality was evaluated with a subjective scoring method. In comparing iohexol and iopamidol groups, there was not a statistically significant difference in the incidence of adverse effects or in myelographic quality. Iopamidol and iohexol appeared to be equally efficacious for routine canine myelography.     

Iohexol myelography in the horse

Iohexol, a water soluble non-ionic contrast agent, was evaluated for myelography in the horse. Both 300 and 350 mg iodine/ml iohexol gave diagnostic cervical myelograms. Pathological changes were limited to extradural oedema and an increase in the number of white blood cells and specific gravity in the cerebrospinal fluid two days after myelography. This increase in white blood cells in the cerebrospinal fluid was, however, much less than that recorded by other authors using metrizamide and iopamidol contrast media. These findings indicate that iohexol is a less irritant myelographic contrast agent than those previously evaluated in the horse.     

IOHEXOL MYELOGRAPHY IN THE DOG

Myelography with iohexol (180 mg iodine/ml, 0.25 ml/kg), a new nonionic radiologic contrast medium, was performed in 100 dogs of 33 different breeds. In 96 of the dogs the iohexol mixed evenly with the cerebrospinal fluid, providing an homogeneous, continuous column of contrast medium within the subarachnoid space, and a radiologic diagnosis of a normal myelogram or disease involving the spinal cord was made. Pooling of iohexol in the dorsal part of the subarachnoid space occurred in four dogs; whether this was related to poor mixing of contrast medium with cerebrospinal fluid or disease of the spinal cord and meninges requires further study. Postmyelographic signs of central nervous system irritation (fasciculations of the temporal muscles and three episodes of seizure activity) were observed in only one dog and were controlled with diazepam. The presenting neurologic signs were aggravated after myelography in four other dogs, two of which were eventually killed. This study provided further evidence of the increased safety of iohexol compared with metrizamide, the first of the nonionic media, as a contrast medium for myelography in the dog.     

ST segment depression and ventricular fibrillation in a dog after contrast agent administration

An 11-year-old Toy Poodle underwent a computed tomography examination with contrast (iohexol) enhancement under anesthesia. Heart rate and R-wave amplitude on electrocardiogram (ECG) increased 2.5 min after iohexol administration, and end-tidal carbon dioxide decreased to 12 mmHg. A progressive ST segment depression was observed on ECG. Subsequently, the ECG waveform changed to ventricular fibrillation. However, spontaneous circulation returned following cardiopulmonary resuscitation. Myocardial ischemia or anaphylactic shock was suspected in the dog, which explains the ST segment depression observed on ECG. When performing radiological examinations with a contrast agent, the ECG waveform changes, such as an increase in heart rate, R-wave amplitude, or ST segment depression, should be carefully monitored. This might enable early detection of cardiac dysfunction and the ensuing cardiac arrest in dogs.     

Comparison of nonionic contrast agents iohexol and iotrolan for cisternal myelography in dogs

During this investigation, the use of iohexol was compared with iotrolan for canine cisternal myelography. Iohexol and iotrolan myelography was done in 6 dogs by cisternal puncture with a 6-week interval between both procedures; each dog served as its own control. Cerebrospinal fluid (CSF) was collected for baseline analysis from each dog immediately before the contrast agent was injected. Cerebrospinal fluid samples were obtained at 1, 3, 7, and 14 days after injection of each contrast medium for cytologic and chemical analysis. Total CSF leucocyte count and glucose concentration did not change significantly in comparison with baseline data in any of the samples. After the injection of iohexol, protein concentration increased significantly in the 24-hour sample, and lactate dehydrogenase activity increased significantly in the 3-day sample. Significant difference was not found between the different samples collected at 1, 3, 7, and 14 days, compared with both contrast media. None of the dogs had seizure activity during a 5-hour postmyelographic observation period. Pathologic changes were not found by gross or microscopic examination of the spinal cord. Although a degradation in time of radiographic quality of all myelograms took place, the average radiographic score decreased more rapidly with iohexol. The average score at 90 minutes with iotrolan was comparable with the score at 45 minutes with iohexol, and the average score at 150 minutes with iotrolan was better than the score at 90 minutes with iohexol. At 5 and 10 minutes after cisternal injection, no significant difference was observable between the myelograms, but from 45 minutes onward, myelograms with iotrolan were superior.     

Effect of dry, soft moist, and canned dog foods on postprandial blood glucose and insulin concentrations in healthy dogs

The effect of dry, soft moist, and canned dog foods on immediate postprandial plasma glucose and insulin concentrations was evaluated in clinically normal dogs. Dogs were fed either dry (10 dogs; group I), soft moist (10 dogs; group II), or canned (8 dogs; group III) dog food for 5 consecutive days. On the fifth day, plasma glucose and insulin concentrations were determined in each dog prior to, during, and at 5, 10, 15, 30, 45, 60, 90, 120, 180, and 240 minutes after ingestion of the food. The alterations in plasma glucose concentrations were not significantly different from prefeeding values until 240 and 180 minutes after feeding for groups I and III, respectively. In contrast, the increments in plasma glucose were significantly (P less than 0.01) increased from basal concentrations at 30 and 45 minutes after feeding in group-II dogs. The maximal mean postprandial plasma glucose concentration was significantly (P less than 0.0001) less for group III, compared with concentrations for groups I and II, but there was no significant difference between concentrations for groups I and II. Although a biphasic insulin secretory response was found in all 3 groups of dogs, the patterns of phase-2 insulin secretion and the total amount of insulin secreted during the study were significantly different. There was a rapid increase in the plasma insulin concentration immediately after phase 1 in group II, with maximal plasma insulin concentrations occurring 30 minutes after feeding, followed by a gradual decrease in concentrations throughout the remainder of the study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of anesthetic regimen on the frequency of seizures after cervical myelography in the dog

We examined the influence of various anesthetic drug combinations on the frequency of seizures in dogs after cervical myelography with metrizamide. Over a 12-month period, 78 dogs admitted to the teaching hospital for cervical myelography were assigned randomly to 1 of 6 anesthetic protocols. Myelography was performed, and the dogs were observed for signs of seizure activity after recovery from anesthesia. The person making the decision as to whether or not a dog had had a seizure was unaware of the anesthetic protocol that had been used. Preanesthetic treatment with pentobarbital (5.0 mg/kg) and maintenance of anesthesia with methoxyflurane significantly reduced the frequency of seizures (P less than 0.05). No reduction in seizure frequency was seen with any anesthetic protocol using halothane as the maintenance agent.     

Effects of intracameral injection of tissue plasminogen activator on corneal endothelium and intraocular pressure in dogs.

Contact wide-field specular microscopy was performed on eyes of 16 healthy dogs after tissue plasminogen activator at a concentration of 25 micrograms/100 microliters (group 1, n = 8) or 50 micrograms/100 microliters (group 2, n = 8) was injected into 1 anterior chamber of each dog. The contralateral eye served as a nontreated control. Applanation tonometry was used to measure intraocular pressure in both eyes for up to 168 hours. By use of computerized morphometric analysis and pachymetry, changes from baseline values in endothelial cell density, cell morphologic features, and corneal thickness were evaluated at postinjection hours 24, 48, and 168. Significant mean differences in intraocular pressure were not detected between treated eyes of group-1 dogs and those in group 2 at designated times, or between treated and nontreated eyes of dogs in either group. Mean corneal thickness of treated and nontreated eyes was similar in both groups through postinjection hour 168. Changes in mean percentage of endothelial cell sides were observed only in treated eyes of group-2 dogs, with the mean percentage of hexagons at postinjection hour 168 decreasing by 18%, a decrease that was significantly (P less than 0.05) greater than the decrease in nontreated eyes. The mean percentage of 6-sided cells in treated eyes of group-2 dogs was significantly (P less than 0.05) less than that in treated eyes of group-1 dogs at postinjection hour 168.     

Effect of intravenous administration of dextrose or lactated Ringer's solution on seizure development in dogs after cervical myelography with metrizamide

The effect of fluid (5% dextrose in water or lactated Ringer's solution) administered intravenously on the development of seizures after cervical myelography with metrizamide was studied in 10 dogs. In a crossover experimental design, 8 dogs were used twice. Urine output was measured during the second part of the study to determine whether diuresis was a factor affecting seizure development. Dogs given 5% dextrose in water had significantly (P less than 0.05) fewer seizures than did dogs given lactated Ringer's solution. This was attributed to an increase in CSF glucose concentration and was not associated with diuresis.     

Use of physiatry as the sole treatment for three paretic or paralyzed dogs with chronic compressive conditions of the caudal portion of the cervical spinal cord

Physiatry alone was used to treat 3 large (30- to 40-kg [66 to 88 lb]) mature (6- to 9-year-old) dogs that were tetraparetic or tetraplegic. All 3 dogs had myelographic evidence of multiple chronic compressive extradural lesions of the caudal portion of the cervical spinal cord. All dogs improved substantially after a course of intensive physical treatment. For 2 dogs, an abbreviated treatment regimen was continued by the owners after the dogs were discharged. Both of these dogs regained and retained normal neurologic function. The other dog improved but was treated infrequently at home. That dog's signs recurred, and the dog was euthanatized. Persistent use of physical treatment for paralysis that results from conditions affecting the cervical spinal cord may be useful even without concurrent surgical or pharmacologic treatments.     

Myelographic localization of spinal cord compression in dogs. A comparison between cisternal and lumbar injections of metrizamide "Amipaque" in diagnosing and locating spinal cord compression.

Metrizamide is a new water-soluble contrast medium possessing unique properties, one of which is that even in an isotonic solution it has a radiographic density sufficient for a diagnostic myelogram. Whereas in the past myelography with water-soluble preparations invariably entailed lumbar injections, which are technically difficult in dogs, the fact that isotonic metrizamide causes so little tissue irritation has made it possible to inject the contrast solution into the cisterna magna. The author has compared metrizamide myelograms obtained with both cisternal and lumbar injections. Myelography with a cisternal injection is preferable for demonstrating cervical cord compressions and also in cases in which it is desirable to obtain myelographic information on both the cervical and the thoraco-lumbar areas. If, on the other hand, it is necessary to determine exactly the extent of a thoraco-lumbar compression before decompressive laminectomy, the contrast should be injected in the lumbar region in such an amount and at a pressure high enough to ensure that the contrast is forced past the site of the compression. The safety of metrizamide will probably enable a better prognosis following surgery than was previously possible.     

Effects of limited food consumption on the incidence of hip dysplasia in growing dogs.

Forty-eight 8-week-old Labrador Retrievers were allotted to 2 groups of 24 dogs each; 1 group was fed ad libitum and the other group was given 25% less of the same feed until the dogs were 2 years old. Radiography of the hip joints was done when the dogs were 30, 42, 54, 78, and 104 weeks old. Subluxation was measured by the Norberg angle on radiographs made with the dog in the standard (extended limb) position. Independent of age at which the radiography was done, there was less subluxation of the femoral heads in the limit-fed dogs. Using the Swedish method of hip joint evaluation on the same radiographs, it was found that fewer dogs on limited food intake had signs of hip dysplasia. Radiographs done when dogs were 2 years old, for all the methods used (Norberg angle in standard and frog-limb position, the Orthopedic Foundation for Animals [OFA] score, and the Swedish score), revealed less hip dysplasia (less joint subluxation and less degenerative joint disease) in the limit-fed dogs. Using the OFA method, 7 of the 24 limit-fed dogs and 16 of the 24 ad libitum-fed dogs were diagnosed as having hip dysplasia. Similarly, using the Swedish method, 5 of the 24 limit-fed dogs and 18 of the 24 ad libitum-fed dogs were diagnosed as having hip dysplasia. The food-intake-related differences were significant both for the OFA score and for the Swedish score.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary fiber supplementation on glycemic control in dogs with alloxan-induced diabetes mellitus.

The effect of a high insoluble-fiber (IF) diet containing 15% cellulose in dry matter, high soluble-fiber (SF) diet containing 15% pectin in dry matter, and low-fiber (LF) diet on glycemic control in 6 dogs with alloxan-induced insulin-dependent diabetes mellitus was evaluated. Each diet contained greater than 50% digestible carbohydrate in dry matter. A crossover study was used with each dog randomly assigned to a predetermined diet sequence. Each dog was fed each diet for 56 days. Caloric intake was adjusted weekly as needed to maintain each dog within 1.5 kg of its body weight measured prior to induction of diabetes mellitus. All dogs were given pork lente insulin and half of their daily caloric intake at 12-hour intervals. Mean (+/- SEM) daily caloric intake was significantly (P less than 0.05) less when dogs consumed the IF diet vs the SF and LF diets (66 +/- 3 kcal/kg, 81 +/- 5 kcal/kg, and 79 +/- 4 kcal/kg, respectively). Serum alkaline phosphatase activity was significantly (P less than 0.05) higher when dogs consumed the LF diet vs the IF and SF diets (182 +/- 37 IU/L, 131 +/- 24 IU/L, and 143 +/- 24 IU/L, respectively). Mean postprandial plasma glucose concentration measured every 2 hours for 24 hours, beginning at the time of the morning insulin injection, was significantly (P less than 0.05) lower at most blood sampling times in dogs fed IF and SF diets, compared with dogs fed the LF diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence of perioperative arrhythmias in 50 young, healthy dogs

The objective of this study was to assess the type and frequency of cardiac dysrhythmias occurring after routine ovariohysterectomy or orchidectomy in young, healthy dogs by using 2 anesthetic protocols (group I: propofol and isoflurane; group II: thiopental and halothane). Fifty dogs under 2 years of age, judged to be clinically normal by physical examination and standard electrocardiography, were evaluated by using 24-hour ambulatory electrocardiography. The most common dysrhythmias in the postoperative period were 2nd degree atrioventricular block (44%), ventricular premature complexes (44%), and atrial premature complexes (32%). For study purposes, more than 100 ventricular or atrial premature complexes per 24 hours, or any occurrence of R-on-T phenomenon, ventricular or atrial tachycardia were classified as clinically significant arrhythmias. Significant arrhythmias were observed in 9 dogs in the postoperative period, 5 of which were in group I and 4 in group II. All of these dogs were under 1 year of age. The R-on-T phenomenon occurred in 4 dogs in group II and 1 dog in group I. Results from this study show that significant arrhythmias, including R-on-T phenomenon, can occur in the perioperative period in young, healthy dogs undergoing routine surgeries with both protocols used.     

EFFECTS OF METRIZAMIDE MYELOGRAPHY ON CEREBROSPINAL FLUID ANALYSIS IN THE DOG

The effect of metrizamide myelography on the composition of cerebrospinal fluid (CSF) was studied. Seven dogs received an intracisternal injection of metrizamide. An intracisternal puncture was performed in three additional dogs that did not receive metrizamide. CSF was collected before myelography and 24, 72, and 144 hours after myelography from all dogs. A significant increase in the percentage of neutrophils (p<0.05) and a pleocytosis noted 24 hours after myelography (p<0.02) were attributed to the effect of metrizamide. Significant increases in total protein concentration (p<0.001) and erythrocyte count (p<0.05), and a decrease in the percentage of small mononuclear cells (p<0.01) were attributed to repeated intracisternal puncture. No significant changes were observed for CSF creatine phosphokinase activity or the percentage of large mononuclear cells.