Standing myelography in the horse using a nonionic contrast agent.

Standing myelography in the horse has been previously described. In that study, metrizamide was used and significant complications were reported. In recent years, the introduction of less-toxic nonionic contrast media has reduced the incidence of complications. This study was undertaken to determine whether standing myelography using a nonionic contrast medium could provide a diagnostic study and be performed safely in the equine patient. Standing myelography was performed in eight horses. The contrast medium used was iohexol. In five horses a myelogram of diagnostic quality was achieved; in one horse contrast flowed only to the level of C6 and in two horses contrast medium did not reach the cervical subarachnoid space. Owing to the difficulty in achieving good flow of the contrast medium in some horses, this procedure may be of limited utility. However, if puncture of the lumbosacral subarachnoid space can be achieved easily and quickly, standing myelography may be a clinically useful procedure. It may be attempted in cases in which the economic value of the patient makes myelography under general anesthesia impractical. In patients presenting for evaluation of ataxia it may be possible to perform a standing myelogram at the time of CSF sample collection from the lumbosacral space.

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.

Intraneoplastic application of metrizamide-containing liposomes: kinetic studies with computed tomography.

Liposomes may serve as drug carriers not only for systemic chemotherapy but also for intraneoplastic drug therapy because they show a sustained drug release. In the present study, the in vivo kinetics of intraneoplastic deposits of large multilamellar vesicles containing metrizamide was followed up in a rat tumor model with computed tomography. The influence of four different lipid compositions on the retardation capacity of large multilamellar liposomes was investigated. By comparing the dynamic data of X-ray attenuation and volume of liposome deposits, a rank order for the in vivo stability of metrizamide containing multilamellar vesicles could be established: the least stable liposomes were made of pure dimyristoyl-phosphatidyl-choline, the most stable type was made of equimolar parts of stearoyl-palmitoyl-phosphatidyl-choline and cholesterol. Of intermediate stability were liposomes made of equimolar parts of dimyristoyl-phosphatidyl-choline and cholesterol, and those made of pure stearoyl-palmitoyl-phosphatidyl-choline. The addition of 50% cholesterol increased the membrane stability of both dimyristoyl-phosphatidyl-choline and stearoyl-palmitoyl-phosphatidyl-choline liposomes. No diffusion of large multilamellar liposomes away from the injection site was observed. The in vivo stability of the liposomes was considerably less than that observed in vitro, suggesting active degradation processes. It is concluded that large, multilamellar liposomes may be suitable carriers for intraneoplastic chemotherapy. The present model is easily adaptable to be transferred into clinical conditions, and may allow direct monitoring of intraneoplastic liposome-mediated chemotherapy in human brain tumors.

Lung tumor incidence after intrabronchial administration of the nonionic contrast agent metrizamide.

RATIONALE AND OBJECTIVES: Metrizamide has been used for examination of the gastrointestinal tract and tracheobronchial tree of infants. Contrast agents may enter the lungs during such examinations. The current study was undertaken to determine whether there would be any later pulmonary effects when metrizamide was administered to the lungs of weanling mice. METHODS: One hundred fifty mice (18-21 days old), divided into groups, received either 75 microL of metrizamide, using the manufacturer's diluent (190 mg iodine [I]/mL), or saline solution administered to the lungs by injection into the trachea. The mice were observed for the duration of their lives. Moribund animals were killed. At death, all animals underwent necropsy. The lungs were fixed in formalin, and histologic sections were examined for pathologic changes. RESULTS: The incidence of lung tumors was increased (P less than .05) in the lungs of mice receiving metrizamide compared with those receiving saline. Eighteen percent of the lung tumors in the metrizamide-treated mice were lymphomas, a histologic type not found in the saline-treated controls. CONCLUSIONS: A hypothesis proposing that metrizamide may be an initiator of carcinogenic transformation rather than a carcinogen was developed.

[The reduction in the local anesthetic dose required for a caudal epidural block in infants and children using a Teflon cannula].

We investigated the spread of mepivacaine mixed with a radio-opaque substance in caudal epidural anesthesia for hernioplasty in 37 patients aged from 3 months to 5 years. All patients were placed in the left lateral position. Conventional caudal epidural anesthesia was performed on one group of patients (Group C) using a 23 gauge needle (25 mm in length). This new method was also performed on another group (Group N) using a 23 gauge Teflon cannula (63 mm in length), which was introduced as close to the S1 segment as possible. The volume for 9 segmental anesthesia (7.0 +/- 2.3 ml) was determined by following Takino's formula: Volume (ml.segmental-1) = 0.067 x [body weight (kg)] + 0.06. The amount was injected from the S1 in Group N patients, and the cephalad spread of the anesthetic reached Th12.8 +/- 0.8 on left side, and L1.1 +/- 0.7 on right side. When the volume for 13 segmental anesthesia (11.5 +/- 2.8 ml) was injected in Group C patients, the cephalad spread of the anesthetic reached Th12.6 +/- 1.2 on the left side, and Th12.5 +/- 1.1 on the right side. In conclusion, we detected no significant difference between Group C and Group N in the cephalad spread of the anesthetic. The required dose of local anesthetic for caudal epidural anesthesia using the Teflon cannula was about two-third the volume of that used for the conventional local anesthetic method.

[Electronystagmographic evaluation of changes in vestibular reactions after administration of diverse substances into cerebral ventricles]. / Elektronistagmograficheskaia otsenka izmeneniia vestibuliarnykh reaktsii posle vvedeniia v zheludochki mozga razlichnykh veshchestv.

Vestibulo-oculomotor reflexes (nystagmus) were recorded by the method of electronystagmography in 33 neurosurgical patients before and after ventriculography. Cerebral ventricles were examined using water soluble compounds (conray, dimeriks, amipaque) in 18 patients or water soluble compounds combined with majodil emulsion in 15 patients. Ventriculography by means of water soluble compounds led to insignificant changes in nystagmic parameters while that by means of X-ray contrasting mixtures caused a frequent and noticeable enhancement of stem vestibular reactions as related to all nystagmic parameters and a significant increase of vestibulo-autonomic reactions.

Serial EEG recordings following intrathecal metrizamide administration.

EEG recordings were obtained before and after intrathecal metrizamide injection in 50 consecutive patients who underwent metrizamide myelography or cisternography. EEG tracings were recorded daily until the pattern returned to baseline. One patient (2%) developed seizures. The most frequent EEG abnormality was generalized slowing of various degrees. In 15 patients (30%), the EEG record was normal throughout the study. In 4 patients (8%), EEG disturbances were seen up to the fifth day after the procedure. Patients who had undergone cervical myelography and cisternography had a marginally higher frequency of EEG disturbances than patients who underwent lumbar myelography. The causes inducing these time-related disturbances are discussed, as compared to pharmacokinetics of intrathecally administered metrizamide.

In vitro release and depot effect after intratumoral application of metrizamide-containing liposomes.

The drug release and intratumoral residence time of small and large liposomes composed of saturated phospholipids and cholesterol were measured in vitro and in tumor-bearing rats by computed tomography. The in vitro release of metrizamide at 37 degrees C was higher in tissue fluid than in diluted serum and PBS-buffer. The extent of release was 20%/48 h for the 100 nm-liposomes and 10%/48 h for the 480 nm liposomes. The decrease of x-ray contrast after intratumoral application resulted in a half-life of t50 = 0.05 d for metrizamide solution and t50 = 0.42 d for small liposomes. Large liposomes showed a linear decrease in contrast, the half-life being t50 = 15 d. While small liposomes rapidly leave the tumor, large liposomes rest intact in the tumor for about 30 d. Therefore they fulfill a fundamental prerequisite for intratumoral depots of cytostatics with controlled release.

Addition of local anesthetics to contrast media. II. Increase of acute mortality in mice with intravenous contrast administration.

The acute intravenous toxicity (i.v. LD50) of solutions of the ratio 1.5 contrast media metrizoate or diatrizoate and the ratio 3.0 contrast medium metrizamide was determined in mice with and without the addition of local anesthetics to the solutions. The two local anesthetics mepivacaine or lidocaine were added to final concentrations up to 2.0 mg/ml of the contrast medium solutions. This corresponds to clinically used concentrations. All additions of local anesthetics to the solutions increased the mortalities caused by the contrast medium solutions. Addition of local anesthetics to a final concentration of 2 mg/ml approximately doubled the acute intravenous toxicity of the contrast media. The ratio 3 contrast media produce less hypertonic solutions than the ratio 1.5 contrast media and should be preferred for angiography because they cause less pain and do not require the addition of local anesthetics which increase the acute toxicity of the solutions.

F-responses after metrizamide and iohexol lumbar myelography.

We measured several F- and averaged F-response variables before and after lumbar myelography with metrizamide and iohexol in order to evaluate possible effects of these contrast agents upon proximal motor nerve conduction and motor neurone exitability. Averaged F-response onset latency increased while both duration and amplitude decreased after iohexol myelography. These changes were interpreted as signs of minor neural depression but they were slight and without clinical significance in the individual patient. F-response variables were not affected after metrizamide myelography.

Percutaneous minidose metrizamide endomyelographic computed tomography in syringomyelia.

Two patients presented with syringomyelia, each unusual. After neuroradiographic diagnosis with delayed metrizamide computed tomography (CT) or magnetic resonance imaging (MRI), an interesting diagnostic question arose. A percutaneous minidose metrizamide endomyelographic CT (PMDMECT) study clarified each situation and directly affected the neurosurgical approaches. The features of each case, the technique of PMDMECT, and postoperative follow-up data are reported.

Complications of myelography after partial metrizamide withdrawal.

Lumbar metrizamide myelography (LMM) has been associated with a high incidence of side effects. A total of 94 patients underwent LMM for suspected disc disease or spinal stenosis. In Group 1 a 22-gauge spinal needle was used. Containing the same amount and concentration of metrizamide, an 18-gauge spinal needle was used in Group 2 after which there was partial withdrawal of the metrizamide (average withdrawal: 73%). In Group 1 a total of 38% of patients experienced one side effect whereas 8.5% had two side effects. In Group 2 a total of 8.5% of patients experienced one side effect and 4.25% had two side effects. This study demonstrates a statistically (P less than 0.003) lower incidence of side effects with metrizamide withdrawal after myelography.

Facet joint degeneration as a cause of low back pain.

Recognizing that not all patients with low back pain have lumbar disc disease, the authors began to inject facet joints in June 1982 and have experience now with 21 patients, each injected under fluoroscopic control with a mixture of local anesthetic and steroid. One technical problem occurred when large osteophytes blocked access to the facet joints. Otherwise, there were no complications and minimal morbidity. Most patients (15 of 20; 75%) had an initial response, but a much smaller number (six of 18 followed more than three months; 33%) had a lasting response. Repeat injections, when done, always led to temporary improvement but rarely to lasting relief (one of five; 20%). Three factors characterized the patients: a negative screening examination for other causes of back pain or sciatica; back pain with tenderness localized over one or more facet joints; and radiologic changes of degenerative joint disease within the facet joints. Facet joint disease may be a significant cause of low back pain. The above three criteria are useful in clinical identification of patients with this problem. Facet joint injections play an important role in the diagnosis and treatment of low back pain.

Low-dose metrizamide spinal computed tomography in outpatients.

Delineation of the thecal sac in CT can be improved by the presence of intrathecal metrizamide. This may be especially helpful in postoperative patients in whom the landmarks are often obscured by epidural scarring. Metrizamide-enhanced CT was performed on outpatients using 2 1/2 ml metrizamide (170 mg I/ml). Follow-up is available on 40 patients. The procedure was well tolerated with only three instances of severe headache, one case of vomiting, and no reported seizures. Adequate opacification was obtained at 92% of the levels examined with fair opacification at the remainder of the levels. This technique is considered a safe and useful outpatient procedure.

CT of extraarachnoid metrizamide instillation.

Because CT of spinal extraarachnoid metrizamide collections may be misleading, we reviewed the postmetrizamide CT scans of 425 patients in order to characterize the appearance of subdural or epidural metrizamide. Eight patients were found to have extraarachnoid metrizamide contrast collections. In all patients, both the subarachnoid space and the extraarachnoid collection were opacified with metrizamide. In seven patients, a subdural collection of metrizamide created a mass upon the opacified subarachnoid space. Three of these subdural collections were less dense than the opacified subarachnoid compartment and simulated soft-tissue disease, including tumor and an arteriovenous malformation. The hypodense collections are probably a result of leakage of metrizamide and cerebrospinal fluid through the spinal needle defect. CT clues for diagnosing these potentially misleading subdural collections include preservation of the normal dural and epidural interface, identification of small islands of metrizamide within a suspected soft-tissue "mass," the presence of concomitant epidural contrast material collections, and the absence of adjacent vertebral-body destruction.