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G T Benness

Publications and source records attributed to G T Benness.

45 records · Page 3Linked to original sources
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Urographic excretion studies with metrizamide and "Dimer": a high dose comparison in dogs.

Metrizamide, a new non-ionic, triodinated contrast agent has been considerable for intravenous urography. Theory predicts that lower osmotic diuresis with this agent should lead to higher urinary iodine concentrations than with ionic agents, at equivalent iodine doses. However, a distinct advantage with metrizamide has not been observed with doses of 175 mgI/kg or less. In this study metrizamide and sodium locarmate were given intravenously to dehydrated dogs at a dose level of 600 mgI/kg. During the studies the concentrations and outputs of major urinary solutes were compared. Comparisons of urinary iodine concentrations and outputs showed that at this dose the predicted advantage with metrizamide can be observed.

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Urographic excretion studies: preliminary results with a six-iodine, singly-ionizing sodium salt--P.286.

Preliminary results of comparative studies with a new water-soluble contrast agent are described. The new agent, with the code P.286, is a molecule with 6 iodine atoms attached and only one ionizing group. The sodium salt of the new agent has been compared with sodium iothalamate and metrizamide in dogs. The results suggest that the sodium salt of P.286 is superior in terms of urinary iodine concentration to both sodium iothalamate and metrizamide.

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Comparison of iopamidol, ioxaglate, and diatrizoate during coronary arteriography in dogs.

Iopamidol and ioxaglate are two new contrast media which have an osmolality approximately half that of diatrizoate for the same iodine concentration. These three contrast media were compared with each other and with Hartmann's solution during coronary arteriography in dogs using hemodynamic and electrocardiographic parameters in addition to coronary venous sinus sampling to measure changes in osmolality, electrolyte, and contrast media concentration. Iopamidol and ioxaglate had similar, but less toxic, effects in comparison with diatrizoate. These new contrast media may offer a reduction in the morbidity and mortality of coronary arteriography.

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Cholangiographic excretion studies. Solu-Biloptin and Biligrafin comparison.

The biliary concentration and output of two cholangiographic agents, Solu-Biloptin (calcium ipodate) and Biligrafin (meglumine iodipamide), were compared in labrador dogs. The maximum output of ipodate was approximately 20 mumol/min compared with 16 mumol/min for iodipamide. The maximum bile iodine concentration with both ipodate and iodipamide was similar (18-20 mgI/Ml) but the molar concentration of ipodate was almost twice that of iodipamide. Iodipamide was found to be much more choleretic, producing 0.025 ml of bile/mumole excreted compared with 0.009 ml/mumole for ipodate. Compared with iodipamide the lower choleretic effect and higher molar concentration of ipodate suggests that hepatic conjugation of the oral agent may permit its excretion in bile salt micelles.

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Comparison of blood-brain barrier disruption by intracarotid iopamidol and methylglucamine iothalamate.

Using a canine model, the effect of intracarotid injections of the ionic contrast medium methylglucamine iothalamate was compared with that of the nonionic contrast medium iopamidol of similar iodine concentration (280 mg 1/ml). The degree and distribution of blood-brain barrier disruption was assessed using Evans blue stain as a visual marker and by contrast enhancement measured by a computed tomographic (CT) scanner. In all studies with methylglucamine iothalamate, Evans blue staining was demonstrated, and CT enhancement demonstrated a significant mean difference (p less than 0.01) between the control and injected hemispheres. The absence of blood-brain barrier disruption with iopamidol is probably related to its lower osmolality (570 mosmol/kg) compared with methylglucamine iothalamate (1,424 mosmol/kg) and the absence of any cation.

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Comparison and evaluation of osmotic blood-brain barrier disruption following intracarotid mannitol and methylglucamine iothalamate.

The effect of intracarotid injections of methylglucamine iothalamate has been compared with that of mannitol solution of similar osmotic strength. The degree and distribution of blood-brain barrier disruption was assessed using Evans' Blue dye as a visual marker and by contrast enhancement measured by computer tomography (CT) scanner. Evans' Blue staining was found to match CT enhancement closely. It was also found that methylglucamine iothalamate injections resulted in significantly greater blood-brain barrier permeability. The relevance of these findings to chemotherapy of brain tumours is discussed briefly.

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Brain parenchyma penetration by intrathecal ionic and nonionic contrast media.

Metrizamide, a nonionic water-soluble contrast medium, has been shown to penetrate normal brain when injected intrathecally. Recently it was suggested that the complications following intrathecal metrizamide are directly related to the cerebral concentration reached. Metrizamide, both in experimental animals and clinically, is regarded as less neurotoxic than equivalent iodine concentrations of ionic contrast media. In this study the degree and depth of brain penetration of intrathecal metrizamide and methylglucamine iothalamate (Conray 280), using a similar iodine concentration (280 mg l/ml), was compared at 1 hr in adult greyhound dogs. The depth of penetration and concentration reached in the cortical gray matter was determined by coronal computed tomographic scanning of the brain after removal. No significant difference was found between the two contrast media, suggesting that the rate of diffusion across the cerebrospinal fluid-brain interface is similar and that the difference in neurotoxicity is not explained by a reduced concentration of contrast medium in the case of nonionic metrizamide, when compared with ionic methylglucamine iothalamate. Using Evans blue as a qualitative marker, no evidence of gross blood-brain disruption was demonstrated in the area of maximum penetration with either contrast medium.

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Cholangiographic excretion studies: a comparison of iodipamide and iodoxamate in the dog.

Iodoxamic acid is a new hexaiodinated cholegraphic contrast agent. The methylglucamine salts of iodoxamate and iodipamide were administered to labrador dogs as an intravenous infusion. Bile salts were also infused. The biliary concentration and output of the two agents were compared. Bile flow rate, bile salt concentration and bile salt output with the two agents were also compared. The biliary output of iodoxamate (0.70-0.78 mumol/min/kg) was more than 50% higher than the iodipamide output (0.46 mumol/min/kg). Bile salt output and concentration with iodoxamate infusion were lower than with iodipamide infusion. The bile flow rate was higher with the new agent. The complementary effects of increased contrast output and decreased bile salt output with the new agent led to a significantly higher biliary iodine concentration compared with iodipamide. The results of this study support the suggestion that iodoxamate represents a significant advance in the cholegraphic contrast media field.

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