The adverse effects of angiographic radiocontrast media

Computed tomography numbers obtained for varying iodine contrast concentrations by different-generation dual-energy computed tomography scanners

We compared the computed tomography (CT) numbers from monochromatic images obtained using the first-generation (Discovery CT750 HD: GE Healthcare, Milwaukee, WI) and second-generation (Revolution CT: GE HealthCare) dual-energy CT (first and second DECT) scanners in phantom and clinical studies. In a polypropylene phantom, eight polypropylene tubes containing iodine at various concentrations (0.5, 1, 2, 5, 10, 12, 20, 30 mg I per ml) were arranged in an outer circle. The iodine densities and CT numbers obtained after imaging with different-generation DECT scanners were analyzed. The CT numbers from images obtained from 61 consecutive patients with aortic disease who underwent CT with different-generation DECT scanners were compared during the arterial and delayed phases. The iodine concentration obtained from second DECT was more accurate than that from the first DECT in the phantom study. A significantly higher contrast enhancement was observed with the second DECT compared with the first DECT during the arterial phase in the clinical study. Contrast enhancement was higher with the second DECT than with the first DECT, and the second DECT was effective in minimizing the use of contrast materials.

Adverse drug reactions in patients with phaeochromocytoma: incidence, prevention and management

The dangers of phaeochromocytomas are mainly due to the capability of these neuroendocrine tumours to secrete large quantities of vasoactive catecholamines, thereby increasing blood pressure and causing other related adverse events or complications. Phaeochromocytomas are often missed, sometimes only becoming apparent during therapeutic interventions that provoke release or interfere with the disposition of catecholamines produced by the tumours. Because phaeochromocytomas are rare, evidence contraindicating use of specific drugs is largely anecdotal or based on case reports. The heterogeneous nature of the tumours also makes adverse reactions highly variable among patients. Some drugs, such as dopamine D(2) receptor antagonists (e.g. metoclopramide, veralipride) and beta-adrenergic receptor antagonists (beta-blockers) clearly carry high potential for adverse reactions, while others such as tricyclic antidepressants seem more inconsistent in producing complications. Other drugs capable of causing adverse reactions include monoamine oxidase inhibitors, sympathomimetics (e.g. ephedrine) and certain peptide and corticosteroid hormones (e.g. corticotropin, glucagon and glucocorticoids). Risks associated with contraindicated medications are easily minimised by adoption of appropriate safeguards (e.g. adrenoceptor blockade). Without such precautions, the state of cardiovascular vulnerability makes some drugs and manipulations employed during surgical anaesthesia particularly dangerous. Problems arise most often when drugs or therapeutic procedures are employed in patients in whom the tumour is not suspected. In such cases, it is extremely important for the clinician to recognise the possibility of an underlying catecholamine-producing tumour and to take the most appropriate steps to manage and treat adverse events and clinical complications.

Is contrast as bad as we think? Renal function after angiographic embolization of injured patients

BACKGROUND

Angiographic embolization (AE) is increasingly used to control bleeding after severe trauma. Serious concerns have been raised about the safety of high-volume i.v. contrast in hypotensive, hypovolemic patients.

STUDY DESIGN

In a prospective cohort study, 100 consecutive trauma patients underwent AE for bleeding in the abdomen and pelvis. Serum creatinine (Cr) levels were measured before the procedure and up to 5 days after the procedure. Contrast nephropathy was defined as an increase in Cr levels after AE of more than 25% over the baseline measurement. An average of 248 +/- 59 mL of nonionic, low-osmolality contrast was used in all cases.

RESULTS

Compared with the baseline, no increase in Cr levels after AE was observed among all patients (1.02 +/- 0.24 versus 0.94 +/- 0.26 mg/dL; p = 0.01) or among subgroups of patients who had any of the following risk factors for renal failure: older than 60 years, Injury Severity Score > or = 15, shock on arrival, renal injury, elevated Cr levels (> or = 1.5 mg/dL) before AE, or administration of a high volume of contrast (> 250 mL). Contrast nephropathy developed in five patients by means of mild Cr elevations. In all of these patients, Cr returned to baseline within 5 days of AE. Renal failure requiring hemodialysis developed at 41 and 55 days after AE in two patients with multiple organ failure who eventually died.

CONCLUSIONS

Administration of nonionic contrast during AE causes mild and transient contrast nephropathy in 5% of severely injured patients. Our study adds additional support for the safety of AE for trauma.

Effect of radiologic contrast media on cell volume regulation in rabbit proximal renal tubules

RATIONALE AND OBJECTIVES

Most radiographic contrast media are hyperosmotic and able to shrink cells with which they are in contact. The authors studied cell volume control in rabbit proximal renal tubules after incubation with three contrast media: iohexol, ioxaglate, and iodixanol.

MATERIALS AND METHODS

Proximal renal tubules were isolated from rabbit kidneys. The tubules were exposed to Ringer solutions containing 5% vol/vol iohexol (final osmolality, 330 mOsm), ioxaglate (323 mOsm), iodixanol (305 mOsm), or mannitol (control solutions with identical osmolalities), and tubule volumes were monitored. After 2 hours of incubation, the tubules were stimulated with a hyposmotic Ringer solution (165 mOsm). Three groups of 10 experiments were performed.

RESULTS

All solutions induced cell shrinkage (8.3%+/-3.8 [standard error] to 15.4%+/-0.5), which was completely or partly reversible in most experiments (volume increase, 44.8%+/-14.7 to 149.9%+/-107.3) but not those with iohexol and iodixanol. With exposure to the hyposmotic solution, the cells swelled by 11.0%+/-1.8 to 39.7%+/-4.8. In general, the tubules that had been exposed to the most hyperosmotic solution swelled the most. Those exposed to contrast media showed less swelling than the mannitol-exposed controls. In all control experiments, the cells exhibited a gradual shrinkage (43.6%+/-28.5 to 87.0%+/-13). This regulatory response was partly inhibited in tubules exposed to iohexol (39.9%+/-15.8 shrinkage) or iodixanol (8.9%+/-15.8) and completely inhibited in those exposed to ioxaglate. Iohexol and ioxaglate exposure also led to a decrease in water permeability.

CONCLUSION

Exposure to hyperosmotic contrast medium tends to induce prolonged cell shrinkage, decrease the water permeability of the cellular plasma membranes, and compromise the ability to regulate cellular volume. These changes seem to reflect both the hyperosmolality of the solutions and their inherent chemical properties.

Effect of radiologic contrast material on cell volume regulation in proximal renal tubules from trout (Salmo trutta)

RATIONALE AND OBJECTIVES

Most radiographic contrast media (CM) are hyperosmotic and pose an osmotic threat to cells they are in contact with. To study these effects at the cellular level, cell volume regulatory mechanisms were observed in proximal renal tubules following exposure to the CM iohexol, ioxaglate, and iodixanol.

MATERIALS AND METHODS

Isolated renal tubules from trout (Salmo trutta) were exposed to 5% vol/vol iohexol (326 mOsm), ioxaglate (314 mOsm), or iodixanol (300 mOsm) or mannitol (to achieve the same osmolalities), and cell volume changes were observed videometrically.

RESULTS

Iohexol and ioxaglate solutions induced a rapid shrinkage (12%-13%) not followed by cell volume regulation. Without CM (same osmolality), the cells shrank 11% but then showed a 77%-88% volume recovery. This reswelling was inhibited by 55% with the Na+, K+, Cl- symporter inhibitor bumetanide (50 micromol/L). Iodixanol did not significantly affect cell volume. Tubules preincubated with CM or mannitol were then stimulated with a hypoosmotic Ringer solution (160 mOsm) resulting in a 26%-36% cellular volume increase. Compared with results of experiments without mannitol and CM, preexposure to iohexol or ioxaglate almost completely inhibited the expected regulatory shrinkage phase, while previous exposure to hyperosmotic solutions with mannitol reduced the shrinkage response by 40%-53%.

CONCLUSION

In this system, the hyperosmotic iohexol and ioxaglate cause cell shrinkage followed by an impaired cell volume regulatory response. Exposure to these two CM also inhibits cell volume regulation on hypoosmotic stimulation. The isosmotic iodixanol has no such effects. These changes appear to some extent to be a result of the CM's degree of hyperosmolality, but this property alone does not explain these findings.

Neuroimaging contrast agents in ophthalmology

Magnetic resonance (MR) imaging and computed tomography (CT) are routinely performed with the use of contrast materials in the diagnosis of neuro-ophthalmologic disease. Iodinated agents are commonly used in CT scanning and femoral contrast arteriography, and gadolinium is used in MR imaging. While contrast materials contribute greatly to diagnostic accuracy, they may also be responsible for adverse effects, ranging in severity from mild discomfort to death. The most frequent and severe side effects are associated with ionic iodinated contrast agents, while the rate of adverse reactions is less with use of nonionic iodinated contrast agents. Side effects and adverse reactions to gadolinium are uncommon, but they do occur. In neuro-ophthalmologic diagnosis, MR imaging is generally preferred over CT scanning, partly because of its greater ability to delineate soft tissue intracranial structures, but also because of the relative safety of gadolinium as a contrast agent. Properties of contrast agents are discussed in the context of specific imaging techniques and tissues investigated. Types and severity of adverse effects as well as risk factors for incurring such effects are summarized.

Iohexol: effects on uptake of radioactive iodine in the thyroid and on thyroid function

RATIONALE AND OBJECTIVES

The authors attempted to determine whether the use of nonionic contrast media causes uptake of iodine by the thyroid to be blocked and whether use of these agents could cause iodine-induced hyperthyroidism.

MATERIALS AND METHODS

Twenty-eight persons, including 22 with thyroid disease, were included in the study. Subjects underwent computed tomography (CT) of the thyroid after injection of 100 mL of iohexol. Thyroid function variables were measured before CT scanning and 1 week and 1 month later. In 16 subjects, uptake of iodine-131 by the thyroid was measured before and 1 week after CT.

RESULTS

I-131 uptake was reduced to 53.4% at 1 week after the injection of iohexol but became normal within a few weeks (followed up in one patient). An accelerated escape of I-131 from the thyroid was seen during the 1st days after the iohexol administration. Eight of 22 patients with an underlying thyroid disease had a temporary change in thyroid function. In four patients, the serum thyrotropin level was increased 1 week after the iohexol administration. In four other patients, temporary hyperthyroidism developed during the following months.

CONCLUSION

Iohexol can be used in patients with an underlying thyroid disease, but close monitoring in the following months is necessary.

Toxicological safety assessment of iomeprol, a new X-ray contrast agent

The toxicology of pharmaceutical formulations of iomeprol, a new nonionic iodinated radiographic contrast agent, was studied in rodents (mice, rats and guinea-pigs) and non-rodents (rabbits and dogs). When injected intravascularly the acute toxicity of iomeprol, both in terms of median lethal dose and symptoms, was comparable to that of analogous triiodinated nonionic contrast media (CM). Intravenous daily dosing for 4 weeks showed that iomeprol was well tolerated at doses as high as the maximum dose anticipated for clinical use. Moreover, the compound did not possess reproductive, developmental, or genetic toxicity. Tissue tolerability was completely superimposable on those of reference CM such as iopamidol and iohexol. Finally, no antigenic potential was detected either in mice or guinea-pigs. These favourable toxicological characteristics bode well for iomeprol as an intravascular radiographic contrast agent.

Novel injectable fluorinated contrast agents with enhanced radiopacity

Novel emulsions containing iodinated fluorinated radiopaque (IFR) molecules were prepared and evaluated as injectable contrast agents with prolonged intravascular persistence. Various stable IFR/egg yolk phospholipid emulsions were produced, heat-sterilized, and tested as to their radiopacity, shelf-stability and in vivo tolerance. No significant change in mean particle sizes was observed over a 3-month storage period at 40 degrees C. Intravenous injection of an emulsion of a 0.39 g/kg bw dose of a typical IFR, C6F13CH = CIC6H13 (F6H6IE) in rabbits led to high contrast in the liver and spleen. The same radiopacity of the liver was achieved with 7 times less IFR than perfluorooctyl bromide. Histological examination after 24 h, and blood analysis after 24, 48 h and 7 days, demonstrated normal functioning of the liver, even when high concentrations of IFR were present. The neat IFR was tolerated i.p. in mice at a 45 g/kg bw dose. Emulsified IFR was tolerated in rats and mice i.v. at a 8 g/kg bw dose. The iodinated fluorinated molecule tested appears promising for the formulation of new contrast agents for diagnosis.