Lasser Ec

Steroids: theoretical and experimental basis for utilization in prevention of contrast media reactions.

In vitro and in vivo studies were done to examine the effects of methylprednisolone on the adverse reactions induced by contrast media. At very high concentrations, the steroid potentiated the complement-activating effect produced in vitro by iodipamide, but inhibited the immune and nonimmune mechanisms of hemolysis. Rabbits pretreated for 3 days with intramuscular methylprednisolone (at high or low dosages) were significantly protected against an LD47 challenging dose of iodipamide. Those treated once with a low intravenous dose immediately prior to iodipamide challenge were protected to a lesser degree. Rabbits treated once with a very high intravenous dose of steroid evidenced no protection. A hyper-responsive dog was consistently protected against adverse reactions to injected sodium iothalamate by a 3-day steroid pretreatment.

Complement and contrast material reactors

Patients showing systemic reactions to intravascular contrast media and patients receiving contrast media without reaction have significantly different mean values (p is less than 0.05) for functionally determined serum C1-esterase inhibitor (C1 INH) and total hemolytic complement (CH50). The lower concentration of these components in reactors appears in baseline serum samples (as well as after injection), and suggests that many anaphylactoid reactions to contrast media are conditioned by earlier complement consumption, and result directly from contrast-induced activation of complement, and other activation system components in the presence of inhibitor depression.

Heparin-like anticoagulants in asthma

In a previous study, and in the present study, we have found that the baseline plasma samples of patients with asthma contain average levels of an endogenous heparin‐like material (EHM) that is significantly higher than that noted in non‐allergic, non‐asthmatic controls. This material appears to have properties of both heparin and heparan sulfate. Three out of six patients responding to inhalational antigen challenge displayed an acute increment in EHM concentration that coincided with a fall in FEV1 values. The relation of EHM concentration to provoked asthma, or to asthma in general, remains to be determined.

Activation systems in contrast idiosyncrasy.

Both animal and human data suggest the possibility that the C1 esterase inhibitor may play an important controlling role in contrast media systemic reactions. This critical controlling protein has a major inhibitory effect on C1, kallikrein, activated factor XII of the intrinsic coagulation system, and on plasmin. In addition, it probably has other inhibitory effects not so well documented. Any circumstance that contributes to a continuing activation of the complement, coagulation, kinin, or fibrinolytic systems may result in partial consumption of the inhibitor and predispose the individual to adverse reactions to contrast challenge.

Changes in complement and coagulation factors in a patient suffering a severe anaphylactoid reaction to injected contrast material: some considerations of pathogenesis.

A patient, suffering a severe anaphylactoid reaction to contrast material injected for an intravenous pyelogram, developed a consumption coagulopathy and evidence of complement activation. Precontrast complement values suggested that the patient had been processing complement via the classical pathway, perhaps as a consequence of an earlier protracted Klebsiella infection. Following contrast injection, a precipitous fall in total hemolytic complement (CH50) and in the concentration of the C1 esterase inhibitor (C1 INH) developed, as well as a diminution in C4 and C3 with the evolution of C3 conversion products. The possible role that these changes might play in the pathogenesis of idiosyncratic reactions to contrast media is considered.

A role for nitric oxide in x-ray contrast material toxicity

RATIONALE AND OBJECTIVES We assessed the role that nitric oxide (NO) plays in contrast media (CM) toxicity, using 100% lethal dose (LD100) studies in hyperimmune Brown Norway (BN) rats. METHODS Ninety-two BN rats and 41 Sprague-Dawley (SD) rats underwent CM LD100 tail vein injections with methylglucamine iothalamate or sodium iothalamate to the point of cessation of respiration. Methylglucamine hydrochloride also was injected. The injections were accompanied by L-arginine (L-Arg) or D-arginine (D-Arg) analogues or by an H1 blocker. L-Arg analogues inhibit NO formation, and D-Arg analogues do not. RESULTS An L-Arg analogue, but not a D-Arg analogue, increased the tolerance of BN rats (p < .005) for methylglucamine iothalamate but not for sodium iothalamate. The L-Arg analogue also protected BN rats against methylglucamine chloride injections (p < .002). H1 blockade protected BN rats against methylglucamine iothalamate (p < .0005) and methylglucamine chloride (p < .005) injections. None of these measures altered the CM tolerance of SD rats. In SD rats, injections of either methylglucamine iothalamate or sodium iothalamate along with a D-Arg analogue or normal saline were better tolerated than similar injections in BN rats (p < .01 and .002 for methylglucamine iothalamate and sodium iothalamate, respectively). In SD rats but not BN rats, sodium iothalamate was better tolerated than was methylglucamine iothalamate (p < .0005). CONCLUSION NO appears to play a significant role in BN rats LD100 CM toxicity and has been implicated by others in the blood pressure fall characterizing some forms of antigen-induced anaphylaxis [1, 2]. The results of the current study and the literature suggest that methylglucamine-modulated release of histamine from mast cells may underlie the NO production.

Intravascular hematocrit effect in cross-sectional ct imaging

Venous fluid-fluid levels were seen on CT or MR of three patients being evaluated for possible thrombosis. In all three cases, further investigation (by ultrasonography, venography, or surgery) revealed the cause of the fluid-fluid level to be slowly flowing blood without thrombosis. On CT done after intravenous contrast medium administration, the nondependent half of the vessel was denser than the dependent half. In an attempt to confirm this MR and CT picture and, particularly, to explain the dense upper half on CT, we conducted an in vitro study. Our study confirmed that when blood with diatrizoate sodium is not clotted and allowed to settle, a similar fluid-fluid level is observed by CT imaging. Our results indicate that an intravascular fluid-fluid level seen on cross-sectional images represents slowly flowing blood, not thrombosis.

Mechanisms of blood pressure change after bolus injections of X-ray contrast media

each animal after the induced pressure effect subsided. Modification of the CM effects in individual animals was studied by injections of the following substances either before or after the CM: NG-nitro-L-arginine methyl ester (L-NAME; Sigma, St Louis, Mo), which inhibits nitric oxide synthesis; sodium nitroprusside (SNP; Sigma), a nitric oxide donor histamine (Sigma); phenylephrine (Sigma), an alpha-adrenergic agonist; phentolamine (Sigma), an alpha-adrenergic antagonist; L-arginine; (Sigma), which accentuates nitric oxide synthesis; diphenhydramine (Benadryl; Sigma), an H1 blocker); and BQ 123 (American Peptide, Sunnyvale, Calif), an endothelin-1 inhibitor.

Alpha-2-Macroglobulin-Kallikrein Complex: A Temperature-Sensitive Mediator in Contact-System-Induced Inflammation with a Potential Role in Late and Delayed Hypersensitivity Responses

Maximal complexing of alpha 2-macroglobulin (alpha 2M) and kallikrein (KK) occurs at a temperature of 22-24 rather than at 37 degrees C. The protease expressivity of the complex is also maximal at 22-24 degrees C. alpha 2M-KK complex, sustained permeability changes in guinea pig skin. These findings suggest that the complex, rather than free KK, could play a role in the kinin release reported in some late-phase reactions, some instances of delayed-type hypersensitivity and some cold-induced reactions.

Contrast and electrolyte dynamics of the intravenous pyelogram. II. Disparities in serum and urine concentrations of meglumine and anion.

Intravenous or intra-aortic injections of meglumine iothalamate in dogs indicate a slightly different tissue distribution and excretory pattern of the meglumine cation and the iothalamate anion. Differences in serum and urinary concentrations of these ions suggest some cellular penetration of the meglumine anion. In addition, there seems to be some evidence for both tubular absorption and tubular excretion of meglumine as a minor component in the renal excretion of this ion. No significant differences could be demonstrated for either urinary load or concentration when the sodium salts of iothalamate were compared to the methylglucamine salts.