Post-lymphangiographic computed tomography in chylothorax after esophagogastrectomy: a case report.

Chylothorax is a rare complication of thoracic surgery. Lymphangiography has long been considered to be the standard of reference for diagnosis and post-treatment evaluation while the role of post-lymangiographic CT is debated. We report a case of chylothorax in a 68-year-old male following esophagogastrectomy for which conservative treatment and thoracic duct ligation failed. Lymphangiography performed after these attempts revealed persistent thoracic duct leakage into the right pleural space. Subsequent non-contrast CT and reformatted images clearly depicted the sources of leakage, and this documentation targeted direct percutaneous treatment. Unfortunately, the lack of access precluded the planned percutaneous CT-guided embolization of the thoracic duct. Nevertheless, this case suggests that post- lymphangiographic CT can serve as a value-added modality in the evaluation and potential treatment of chylothorax.

Calcium binding by radiopaque media.

This study quantified the binding of ionic calcium by contrast media with disodium edetate and trisodium citrate versus those with only calcium disodium edetate. First, calcium binding by sodium diatrizoate with calcium disodium edetate was measured using an ion-selective electrode at ionic strengths of .08, .16, and .80 molal. Significant binding of calcium was observed, and the probable reaction product is calcium chloride diatrizoate. Second, solutions were mixed containing Renografin 76 (or Hypaque 76) and NaCl at a physiologic ionic strength. The Renografin, which contains disodium edetate and trisodium citrate, caused significantly more binding than did the Hypaque. However, 60% of the drop in ionic calcium was observed with Hypaque and is related to the diatrizoate anion. The nonionic agent iopamidol produced no decrease in ionic calcium. Significant reductions in ionic calcium are produced by both the diatrizoate anion and by edetate and citrate additives.

Pharmacokinetics and excretion of iohexol after lumbar myelography in man.

Pharmacokinetics and excretion of iohexol, a new nonionic water-soluble contrast medium, were determined after lumbar myelography. Peak plasma concentrations were obtained 2 to 6 hours after injection and ranged from 29 to 177 microgram/ml. Terminal elimination half-life was 4.0 hours, and over 90% of the dose was recovered in the urine within 24 hours. In one patient with a large lumbar cauda equina tumor, absorption and excretion were delayed; but eventually 99% was recovered indicating a large capacity for reabsorption via the lumbar subarachnoid space. One mild headache of 5 minutes' duration was reported in a 73-year-old woman. No significant changes in vital signs, neurologic examinations, or serum chemistries were observed.

Changes in serum magnesium during excretory urography. A comparison of ionic and nonionic contrast media.

RATIONALE AND OBJECTIVES: It is known that ionic contrast media (CM) bind magnesium and that patients with asthma often benefit from magnesium injections. Similarly, asthmatics have a higher incidence of CM reactions. This work tests the hypothesis that ionic CM alter serum magnesium more than nonionic CM. METHODS: Ten patients were divided into two groups; one group received iothalamate and the other received iohexol. RESULTS AND CONCLUSIONS: The total magnesium level changed significantly from baseline in the iothalamate-treated group (P less than .01). Iothalamate produced a significant decrease in protein-bound magnesium (P less than .01) with a significant increase in filterable magnesium (P less than .01). Iohexol did not produce significant changes for any of the magnesium fractions. The patient with the most clinically significant adverse reaction (though minor) had the lowest baseline magnesium level. Further studies with larger groups including patients with asthma are needed.

Renal handling and physiologic effects of the paramagnetic contrast medium Gd-DOTA.

Gadolinium DOTA (Gd-DOTA) is a magnetic resonance (MR) contrast agent similar to Gd-DTPA but with greater stability in vitro. The effects of a high intravenous dose (0.5 mmol/kg) of Gd-DOTA (1360 mOsm/kg) on renal excretory function and its general systemic effects are examined in this animal study. This dose was selected to accentuate and better define the qualitative nature of these effects. A decrease in arterial pressure of 8% (131.9 +/- 6.8 at 120 minutes versus a control of 142.8 +/- 3.7 mm Hg, mean +/- standard error of mean, no significant change in electrocardiogram (ECG) lead II, a 16% increase in renal blood flow (106.0 +/- 5.4 at 7.5 minutes versus 91.2 +/- 3.2 ml/min), and a decrease in arterial hematocrit of 9% (38.9 +/- 1.5 at 120 minutes versus 41.9% +/- 1.7%) were noted. In general, qualitatively similar effects have been noted as a nonspecific effect of other hyperosmolar solutions. The filtration fraction decreased (0.23 +/- 0.01 at 7.5 minutes versus 0.28 +/- 0.02) followed by a rapid return to baseline values. No significant change was noted in glomerular filtration rate throughout the experimental protocol. Urine flow increased nearly 1.5-fold and osmolal clearance (Cosm) increased approximately 1.5 times. A natriuresis occurred as the fractional excretion of sodium (FENa+) increased from a control value of 3.5 +/- 0.3 to 5.2 +/- 0.5 at 7.5 minutes. The systemic and renal physiologic effects of high-dose intravenous Gd-DOTA on the kidney reflects a nonspecific, osmotically induced alteration. These data suggest that the main systemic and renal physiologic actions of Gd-DOTA are a nonspecific response to agent osmolality that is similar qualitatively to conventional, water-soluble contrast media.

Luminal diameter and vasa vasorum response to stent dilation in the rabbit aorta.

RATIONALE AND OBJECTIVES: We examined the changes in luminal diameter and vasa vasorum after stent dilation of the aorta of nonatherosclerotic rabbits. METHODS: Balloon-expandable stents were placed in the aortas of rabbits at the L3 level and were expanded. After 8 weeks, the rabbits were euthanized, perfused with barium sulfate particles, frozen, sectioned, and X-rayed. RESULTS: The luminal intrastent diameter (2.3 +/- 0.23 mm) was significantly different (p < .05) from the expanded stent diameter but was not different from the luminal diameter above (2.3 +/- 0.53 mm) and below (1.9 +/- 0.18 mm) the stent. The number of vasa vasorum at the stent (46 +/- 7.2) was significantly increased compared with above (21 +/- 4.8, p < .001) and below (14.4 +/- 4.6, p < .001) the stent. CONCLUSION: After 8 weeks, luminal diameter was uniform. The increased vasa vasorum in the stented section suggested an increase in blood flow to the aortic wall, which may be important to the remodeling process.

Comparison of vasa vasorum after intravascular stent placement with sirolimis drug-eluting and bare metal stents.

The cytostatic drug, sirolimis has shown prevention in neointimal hyperplasia after stent placement. Recent studies have shown persistent inflammation seen with drug-eluting stents (DES) may result in late stent thrombosis. The aim of this study is to compare effects of bare metal stents (BMS) and sirolimis DES on the neointima and vasa vasorum in stented rabbit aortas. Stents were implanted in eight New Zealand rabbits for 9 weeks. Group I rabbits received BMS. Group II rabbits received sirolimis DES. A balloon-mounted BMS or DES was placed in the infrarenal aorta. Following euthanasia, aortas were perfused with barium sulfate and sectioned for histology. After 9 weeks the qualitative intrastent luminal diameter was fairly uniform in both the DES and the BMS. The thickness of neointima was similar in both groups. The number of vasa vasorum in the sirolimis DES increased compared with the BMS (P < 0.05). An increased number of vasa vasorum produced by the DES when compared with the BMS shows a difference in response to local vessel injury in rabbits. This result suggests that vasa vasorum may play a role in the persistent inflammation generated by sirolimis-coated stents.

Neural tissue uptake and clearance of iohexol following lumbar myelography in rabbits.

The diffusion of water-soluble contrast media (CM) into the extracellular space of the central nervous system following injection into the subarachnoid space has previously been shown. As a result of this, water-soluble CM will come in direct contact with the neurons and may interfere with their normal function. The toxic effects would thus be a result both of the molecular properties of the CM as well as the local tissue concentration. The neuronal tissue uptake and clearance of metrizamide in rabbits following lumbar myelography was described in a previous study by our group. This study indicated some retention of metrizamide in the spinal cord probably as a result of binding of the CM to the cell membrane. The mechanism for this has not yet been shown although it may relate to the binding of metrizamide via its 2-deoxy-D-glucose (2-DG) portion and the specific glucose membrane carrier. The present investigation was performed to evaluate the diffusion kinetics of a new non-ionic CM. With iohexol, which lacks a 2-DG component in its molecule a direct relationship between the neural tissue and CSF concentration was found which seems to follow a simple diffusion model. Since iohexol shows no sign of entrapment in the tissue, the contact time for neurons will be shorter than that seen with metrizamide assuming that their rate of drainage from the CSF is identical.

Canine model of contrast medium induced fibrillation.

The injection of radiocontrast media into coronary arteries will produce a low incidence of ventricular fibrillation. This study establishes the injection duration (or contact time) required to produce fibrillation during right coronary angiography in dogs using a 370 mg I/ml, meglumine/sodium diatrizoate formulation (Renografin 76, Squibb). The mean contact time required to induce fibrillation was 18.8 +/- 5.8 seconds for 66 injections in 47 dogs. Prolonged ischemia of greater than 170 s did not produce either fibrillation or arrhythmias, therefore fibrillation is caused by properties of the media. The contact time was not significantly influenced by test injections and was not significantly different in repeated experiments. The canine contact time model of contrast media induced ventricular fibrillation is reproducible and will facilitate the study of risk factors that increase the possibility of fibrillation.

Factors modifying contrast media induced fibrillation.

Factors effecting contrast media induced ventricular fibrillation were studied in anesthetized dogs using contact time as the measured parameter. Injections of meglumine/sodium diatrizoate (370 mg I/ml) were made into the right coronary artery at 0.4 ml/s until fibrillation occurred. A contrast medium containing calcium chelators was found to produce fibrillation in a significantly shorter contact time than a similar medium without calcium chelators. Pre-treatment by the cardiac glycoside, ouabain, increased the contact time for fibrillation as did the production of a sub-acute infarction in the left coronary artery and a previous fibrillation and resuscitation. The data suggest that calcium binding additives increase the risk of fibrillation while pre-treatment with cardiac glycosides, the presence of stable infarcts in the non-injected areas, or a previous fibrillation and resuscitation do not increase risk.

Incidence of fibrillation with isotonic contrast media for intra-arterial coronary digital subtraction angiography.

Intra-arterial digital subtraction angiography (DSA) can produce coronary artery opacification with isotonic contrast media. In this study we have examined the importance of electrolyte composition in isotonic formulations on the incidence of fibrillation. Right coronary injections of media were made for 25 s in anesthetized dogs. Isotonic meglumine diatrizoate and iohexol produced fibrillation in more than 68% of the injections, while sodium diatrizoate, saline, meglumine/sodium ioxaglate and iohexol with added sodium diatrizoate never produced fibrillation. These animal studies demonstrate a significantly higher risk of fibrillation (p less than 0.005) with isotonic nonionic and ionic media not containing sodium ions.

Microangiography of the rabbit temporomandibular joint in the open and closed jaw positions.

The purpose of this investigation was to test the hypothesis that jaw position significantly affects the vascular morphology of the temporomandibular joint (TMJ). The study was performed using intravascular perfusion with 30% Micropaque and 40% gelatin. Six anesthetized New Zealand white rabbits were divided into 2 groups of three. Group 1 rabbits were perfused in the resting, closed-jaw position and group 2 rabbits were perfused while the jaw was held open. The animals were killed with an overdose of pentobarbital and frozen. The heads were hemisected, fixed, decalcified, and embedded in Cedukol. Sagittal sections were cut at the level of the meniscus and radiographed with a specimen x-ray unit on high-resolution film. The 6 rabbits (12 TMJs) demonstrated consistent microvascular differences. In 83% of the jaws in group 2 rabbits the anterior condylar vein was not seen or appeared patchy whereas the same vein was readily seen in all jaws of group 1 (P less than .01). The superior condylar vasculature was distended in 83.3% of group 2 jaws and in 16.7% of group 1 jaws (P less than .05). This study demonstrates significant changes in vascular morphology when the jaw is placed in the open position.

Work in progress: reduction of calcium activity by radiopaque contrast media.

An in vitro examination of the effects of radiopaque contrast media anions, cations, additives, and ionic strength on ionic calcium level using ion-specific electrodes was made. The calcium-binding additives sodium citrate and sodium EDTA produced the largest reduction in ionic calcium. At the same iodine concentration the anions diatrizoate, iothalamate, metrizoate, and ioxaglate reduced ionic calcium by essentially the same amount. Sodium compounds reduced ionic calcium more than did meglumine compounds, a difference that is probably related to dissociation. The nonionic compounds iohexol and iopamidol did not reduce ionic calcium significantly. Ionic strength appears to have little direct effect on ionic calcium at and above physiologic levels. All ionic contrast media bind significant amounts of ionic calcium at the high concentrations achieved during selective arteriography. Since the anions are only weak calcium binders supplemental calcium can restore the level of ionic calcium.

Lumbar myelography with iohexol and metrizamide. A double-blind clinical trial.

Two non-ionic contrast media, iohexol and metrizamide, were compared in a double-blind clinical trial which included 50 patients who underwent lumbar myelography for disc herniation or spinal stenosis. The frequency of adverse reactions was lower for iohexol which is recommended for extended trials and for examination of other compartments of the subarachnoid space.

Contrast media induced fibrillation: comparison of Angiovist 370 and Renografin 76. Work in progress.

Angiovist 370, a new formulation of meglumine/sodium diatrizoate, is being marketed for coronary arteriography. Angiovist 370 contains no significant calcium chelator additives, but according to manufacturer specifications may have a pH as low as 6.0. The contact times required to produce ventricular fibrillation with Angiovist 370 and with Renografin 76 were compared using a canine right coronary arteriography model. The fibrillation contact time was 32.2% longer for the Angiovist 370 than for the Renografin 76. The lower pH therefore does not appear to increase the risk of contrast media induced fibrillation. The increased contact time and safety factor with the Angiovist 370 is most likely related to the absence of calcium chelators in the formulation.