The haemodynamic effects of iodinated water soluble radiographic contrast media: a review

Hemodynamic effects of intravenous bolus injection of iopromide 370 twice in abdominal contrast-enhanced CT and coronary CTA dual-site sequential examinations

Little information is available about how intravenous bolus injection of iopromide 370 twice in a short time will affect hemodynamics and whether the changes reach clinically relevant levels. In the present study, 31 healthy adult volunteers received abdominal contrast-enhanced CT and coronary CTA sequential examinations. The same dose and rate of normal saline was injected 30 min in advance as self-control. Hemodynamic data were noninvasively collected at selected time points from 1 min prior to injection to 30 min post-injection. The results showed that after iopromide 370 injection, except for stroke volume, all other indicators changed immediately during the first injection, changed most significantly during the second injection (P < 0.05), and returned to baseline within 10 min. Heart rate and cardiac output exhibited the most pronounced changes, with an increasing rate of 33.5% and 33.8%, respectively. For indicators with a change range of > 15% during the second injection, except for mean arterial pressure and total peripheral resistance, the proportions of subjects for the other indicators between the two groups were statistically different (P < 0.05). In conclusion, intravenous bolus injection of iopromide 370 twice in dual-site sequential examinations induced dose-cumulative and time-dependent hemodynamic effects, which all fluctuated within the normal ranges.

Iodine Deficiency and Mortality in Spanish Adults: Di@bet.es Study

Background: Longitudinal data assessing the impact of iodine deficiency (ID) on mortality are scarce. We aimed to study the association between the state of iodine nutrition and the risk of total and cause-specific mortality in a representative sample of the Spanish adult population. Methods: We performed a longitudinal observational study to estimate mortality risk according to urinary iodine (UI) concentrations using a sample of 4370 subjects >18 years representative of the Spanish adult population participating in the nationwide study Di@bet.es (2008-2010). We used Cox regression to assess the association between UI at the start of the study (<50, 50-99, 100-199, 200-299, and ≥300 μg/L) and mortality during follow-up (National death registry-end of follow-up December 2016) in raw models, and adjusted for possible confounding variables: age, sex, educational level, hypertension, diabetes, obesity, chronic kidney disease, smoking, hypercholesterolemia, thyroid dysfunction, diagnosis of cardiovascular disease or cancer, area of residence, physical activity, adherence to Mediterranean diet, dairy and iodinated salt intake. Results: A total of 254 deaths were recorded during an average follow-up period of 7.3 years. The causes of death were cardiovascular 71 (28%); cancer 85 (33.5%); and other causes 98 (38.5%). Compared with the reference category with adequate iodine nutrition (UI 100-300 μg/L), the hazard ratios (HRs) of all-cause mortality in the category with UI ≥300 μg/L were 1.04 (95% confidence interval [CI 0.54-1.98]); however, in the categories with 50-99 UI and <50 μg/L, the HRs were 1.29 [CI 0.97-1.70] and 1.71 [1.18-2.48], respectively (p for trend 0.004). Multivariate adjustment did not significantly modify the results. Conclusions: Our data indicate an excess mortality in individuals with moderate-severe ID adjusted for other possible confounding factors.

Effect of bolus administration of non-ionic radiopaque contrast media on blood pressure variation

INTRODUCTION

Haemodynamic changes may occur with the rapid intravenous injection of contrast media due to the osmolality of such pharmaceuticals. This study sought to evaluate the effect of bolus administration of intravenous contrast media on blood pressure variation during the Contrast-Enhanced Computed Tomography (CECT) of the abdomen.

METHODS

The study included 74 patients who underwent abdominal CECT and they were placed in the first group receiving a maximum of 80 ml of iodinated contrast via pressure injector (4 ml/s). A further 74 patients, who underwent non-contrast enhanced abdominal CT, were placed in the second group in which 80 ml of normal saline was administered via the same manner. Patients with hypertension and who were on anti-hypertensive drugs were excluded from the study. Non-invasive blood pressure was monitored before the injection of contrast media/saline and immediately after the portal venous phase for the CECT scan and after 45 s following the administration of normal saline in the non-contrast CT group. Mean systolic and diastolic blood pressures from both groups were compared to find out the effect of contrast bolus administration on blood pressure variation.

RESULTS

Both systolic and diastolic blood pressure increased with the injection of contrast media among CECT scan group. No significant changes in systolic and diastolic blood pressure were found before and after the scan in the non-contrast group.

CONCLUSION

Bolus administration of 80 ml saline has no effect on blood pressure. The increased blood pressure in contrast enhanced studies was induced by the iodinated contrast media and not by the bolus effect.

Extraosseous Colonic Uptake of 99mTc-MDP Associated With Iodinated Contrast CT

Extraosseous Tc-MDP uptake on bone scans is frequently encountered and has a broad differential diagnosis. A small subset of such patients can present with intestinal Tc-MDP uptake. We present the case of a 35-year-old woman with status after right nephrectomy for renal cell carcinoma, being followed with bone scan for osseous metastases. Follow-up imaging revealed new faint Tc-MDP uptake in the right hemiabdomen. Correlation with contrast-enhanced CT localized this uptake to the ascending colon. Enteric Tc-MDP uptake and its association with iodinated contrast should be considered in the differential diagnosis of extraosseous enteric Tc-MDP uptake.

Migraine and Non-Migraine Headaches Following Diagnostic Catheter-Based Cerebral Angiography

BACKGROUND AND OBJECTIVE

No reliable estimates of headaches following catheter-based cerebral angiography are available. We performed an observational cohort study to ascertain the frequency and type of headaches following catheter-based cerebral angiography.

MATERIALS AND METHODS

Consecutive patients who underwent cerebral angiography through the transfemoral (or infrequently radial) route were included. Each patient underwent a brief neurological assessment after the procedure and more detailed assessment was performed if any patient reported occurrence of a headache. The headaches were classified as migraine if the diagnostic criteria specified by International Headache Society were met. The headache severity was classified using a visual numeric rating scale and time to reach pain free status for 2 consecutive hours was ascertained.

RESULTS

Migraine headaches occurred in 5 (3.1%, 95% confidence interval [CI] 1.0-7.2%) of 158 patients who underwent cerebral angiography. The median severity of migraine headaches was 10/10 and time to resolution of headaches was 120 minutes (range 60-360 minutes). Migraine headaches occurred in 4 (18.1%, 95% CI 5.2-40.3%) of 22 patients with a history of migraine and 4 (23.5%, 95% CI 6.8-50%) of 17 patients with regular migraine headaches (≥1 episodes per month). Headaches occurred in 6 (3.8%, 95% CI 1.8-8.0%) patients who did not meet the criteria for migraine headaches.

CONCLUSIONS

We provide occurrence rates of migraine headaches, an under-recognized adverse event, in patients undergoing catheter-based cerebral angiography.

Influence of preoperative imaging on fibula free flap harvesting

INTRODUCTION

The fibula free flap (FFF) is the gold standard for the reconstruction of large maxillofacial defects. Magnetic resonance angiography (MRA) seems to supersede digital subtraction angiography (DSA) as the reference in preoperative evaluation, being non-invasive and having equivalent diagnostic results. The aim of this study was to assess the impact of preoperative MRA versus DSA on the viability of FFF and its success rate.

MATERIAL AND METHODS

A total of 216 patients, who underwent mandibular or maxillary FFF reconstruction from January 1995 to January 2011, were retrospectively included in the study. Of them, 101 patients underwent preoperative DSA and 115 underwent MRA. Recorded criteria were as follows: age, sex, tobacco consumption, defect etiology, preoperative vascular assessment, donor-site choice and flap failure. The DSA group was compared to the MRA group.

RESULTS

The harvested side was switched in 15.7% of cases with preoperative MRA versus 4% with DSA. Our success rate was higher (96.1%) with MRA than with DSA (88.1%) (P<0.05). More atherosclerotic patients (P=0.004) were diagnosed through MRA. MRA and DSA showed similar results in anatomical variation detection.

CONCLUSION

MRA is less invasive and more effective in atherosclerosis detection than DSA. Therefore, donor-site switching was more frequent in the MRA group, which led to a better success rate. MRA should replace DSA as the reference in preoperative assessment.

Incidental 99mTc MDP uptake in the intestines and intravenous CT contrast

AIM

We evaluated the association between intestinal visualization on bone scintigraphy and IV CT contrast in patients with breast cancer.

PATIENTS, METHODS

452 patients with breast cancer underwent a 99mTc methylene diphosphonate (MDP) bone scan for surveillance of bone metastasis. Presence, site and intensity of intestinal uptake were visually assessed. For patients with intestinal visualization, medical records were reviewed to identify the alleged potential causes. When IV CT contrast was administrated on the same day as bone scan, the time between IV CT contrast injection, 99mTc MDP administration and bone scan was assessed.

RESULTS

Intestinal 99mTc MDP uptake was observed in 44 of the 452 patients (9.7%). Bone scans showed no thyroid or gastric uptake that suggested free pertechnetate. There were no patients with documented causes of intestinal uptake except for one patient with vesicoenteric fistula. Of the 452 patients, 149 (33.0%) underwent IV contrast-enhanced CT on the same day as bone scan. Forty of the 44 patients (90.9%) with intestinal uptake on bone scan underwent IV contrast-enhanced CT on the same day, whereas 109 of 408 (26.7%) patients without intestinal uptake on bone scintigraphy underwent IV contrast-enhanced CT on the same day (p < 0.001). The patients who underwent IV contrast injection between Tc-99m MDP administration and acquisition of bone scans had significantly more frequent intestinal uptake than patients who underwent IV contrast injection either before 99mTc MDP administration or after bone scanning (42.4% vs. 1.8%, p < 0.001).

CONCLUSIONS

IV CT contrast injection administered on the same day as bone scintigraphy is significantly associated with 99mTc MDP uptake in the intestines among patients with breast cancer.

Diagnostic Accuracy, Image Quality, and Patient Comfort for Coronary CT Angiography Performed Using Iso-Osmolar versus Low-Osmolar Iodinated Contrast: A Prospective International Multicenter Randomized Controlled Trial

RATIONALE AND OBJECTIVES

The impact of iso-osmolar versus low-osmolar iodinated contrast on diagnostic accuracy for coronary computed tomography angiography (CCTA), against the reference standard of invasive coronary angiography (ICA), has not been determined. We sought to compare in an international multicenter randomized controlled trial the impact of iso-osmolar iodixanol versus low-osmolar iopamidol on diagnostic accuracy, image quality, patient symptoms, and heart rate variability.

MATERIALS AND METHODS

Adult patients who were clinically referred for ICA were randomly assigned to receive either iodixanol (n = 133) or iopamidol (n = 133) with an investigational CCTA. CCTA stenosis and image quality were scored by consensus of independent blinded core laboratory readers. Degree of stenosis by ICA was evaluated using quantitative coronary angiography and used to calculate diagnostic accuracy. Heart rate variability and patient-reported symptom questionnaires were compared between the two groups.

RESULTS

A total of 266 subjects underwent both CCTA and ICA (57 ± 11 years, 58% male). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for detecting coronary artery disease were 86.8%, 93.7%, 84.6%, 94.7%, and 91.7% for iodixanol and 94.7%, 88.4%, 76.6%, 97.7%, and 90.2% for iopamidol, respectively, on a per-patient level. These values were not significantly different between the two groups. There was no significant difference in image quality and heart rate increase or variability. The majority of patients reported symptoms (59.4%), with no differences in the overall or individual rate of any or moderate to severe symptoms between the two groups. Patients receiving iodixanol reported lower incidence of moderate to severe flushing (3.0% vs. 12.8%, P = .005). Lower rates of moderate to severe symptoms were particularly evident for patients with ≥55 years receiving iodixanol versus iopamidol (8.5% vs. 24.6%, P = .01).

CONCLUSIONS

Diagnostic performance and image quality were similar for CCTA performed with iso-osmolar versus low-osmolar iodinated contrast. Indices of patient comfort were improved with iso-osmolar iodinated contrast.

Adverse reactions following administration of contrast media for diagnostic imaging in anaesthetized dogs and cats: a retrospective study

OBJECTIVE

To evaluate incidences of adverse reaction after the administration of contrast media.

STUDY DESIGN

Retrospective observational study.

ANIMALS

Animals included 356 dogs and 58 cats receiving non-ionic iodinated contrast agents, and 425 dogs and 49 cats receiving gadolinium-based contrast agents.

METHODS

Anaesthesia records of dogs and cats receiving intravenous (IV) gadobutrol for magnetic resonance imaging (MRI) or IV iohexol for computed tomography (CT) were reviewed. Changes in pulse rate, respiratory rate and mean arterial pressure at 5 minutes after administration of the contrast medium were evaluated. Changes of 10-20% were considered mild, those of >20% moderate, and reactions that required immediate treatment were considered severe. Associations of sex, age and weight with contrast reaction were investigated using logistic regression. Differences in the incidences of reactions to CT and MRI contrast media were examined with chi-squared tests. A p-value of <0.05 was considered to indicate statistical significance.

RESULTS

Of cats receiving iohexol, eight (13.8%) had mild and 10 (17.2%) had moderate reactions. Of cats receiving gadobutrol, six (12.2%) had mild and six (12.2%) had moderate reactions. No cats had severe reactions and the risk for reaction was not associated with type of medium, age, weight or sex (p > 0.2). Of dogs receiving iohexol, 64 (18.0%) had mild, 65 (18.3%) had moderate and three (0.8%) had severe reactions. Of dogs receiving gadobutrol, 42 (9.9%) had mild, 87 (20.5%) had moderate and one (0.2%) had a severe reaction. When dogs receiving iohexol were compared with those receiving gadobutrol, the odds ratio of a moderate reaction was 2.0 (95% confidence interval 1.34-3.10; p = 0.001). These estimates did not change substantially after adjustment for age, weight and sex.

CONCLUSIONS AND CLINICAL RELEVANCE

Severe reactions to iohexol and gadobutrol are rare in dogs and cats; moderate reactions are more likely with iohexol than with gadobutrol.

Effects of Mn-DPDP and manganese chloride on hemodynamics and glucose tolerance in anesthetized rats

BACKGROUND

Previous studies have demonstrated that magnetic resonance imaging may be a method of choice to visualize transplanted pancreatic islets. However, contrast agents may interfere with microcirculation and affect graft function.

PURPOSE

To evaluate the effects manganese-containing contrast media on regional blood flow and glucose tolerance.

MATERIAL AND METHODS

Anesthetized rats were injected intravenously with MnCl2 (10 µM/kg body weight) or Mn-DPDP (Teslascan™; 5 µM/kg body weight). Blood flow measurements were made with a microsphere technique 10 min later. In separate animals vascular arteriolar reactivity in isolated, perfused islets was examined. Furthermore, an intraperitoneal glucose tolerance test was performed in separate rats.

RESULTS

Glucose tolerance was unaffected by both agents. No changes in regional blood flow were seen after administration of Mn-DPDP, except for an increase in arterial liver blood flow. MnCl2 increased all blood flow values except that of the kidney. MnCl2, but not Mn-DPDP, caused a vasoconstriction in isolated rat islet arterioles but only at very high doses.

CONCLUSION

Mn-DPDP administration does not affect glucose tolerance or regional blood flow, besides an increase in arterial hepatic blood flow, and may therefore be suitable for visualization of islets.

Contrast media viscosity versus osmolality in kidney injury: lessons from animal studies

Iodinated contrast media (CM) can induce acute kidney injury (AKI). CM share common iodine-related cytotoxic features but differ considerably with regard to osmolality and viscosity. Meta-analyses of clinical trials generally failed to reveal renal safety differences of modern CM with regard to these physicochemical properties. While most trials' reliance on serum creatinine as outcome measure contributes to this lack of clinical evidence, it largely relies on the nature of prospective clinical trials: effective prophylaxis by ample hydration must be employed. In everyday life, patients are often not well hydrated; here we lack clinical data. However, preclinical studies that directly measured glomerular filtration rate, intrarenal perfusion and oxygenation, and various markers of AKI have shown that the viscosity of CM is of vast importance. In the renal tubules, CM become enriched, as water is reabsorbed, but CM are not. In consequence, tubular fluid viscosity increases exponentially. This hinders glomerular filtration and tubular flow and, thereby, prolongs intrarenal retention of cytotoxic CM. Renal cells become injured, which triggers hypoperfusion and hypoxia, finally leading to AKI. Comparisons between modern CM reveal that moderately elevated osmolality has a renoprotective effect, in particular, in the dehydrated state, because it prevents excessive tubular fluid viscosity.

Contrast-induced kidney injury: mechanisms, risk factors, and prevention

In general, iodinated contrast media (CM) are tolerated well, and CM use is steadily increasing. Acute kidney injury is the leading life-threatening side effect of CM. Here, we highlight endpoints used to assess CM-induced acute kidney injury (CIAKI), CM types, risk factors, and CIAKI prevention. Moreover, we put forward a unifying theory as to how CIAKI comes about; the kidney medulla's unique hyperosmolar environment concentrates CM in the tubules and vasculature. Highly concentrated CM in the tubules and vessels increases fluid viscosity. Thus, flow through medullary tubules and vessels decreases. Reducing the flow rate will increase the contact time of cytotoxic CM with the tubular epithelial cells and vascular endothelium, and thereby damage cells and generate oxygen radicals. As a result, medullary vasoconstriction takes place, causing hypoxia. Moreover, the glomerular filtration rate declines due to congestion of highly viscous tubular fluid. Effective prevention aims at reducing the medullary concentration of CM, thereby diminishing fluid viscosity. This is achieved by generous hydration using isotonic electrolyte solutions. Even forced diuresis may prove efficient if accompanied by adequate volume supplementation. Limiting the CM dose is the most effective measure to diminish fluid viscosity and to reduce cytotoxic effects.

The influence of contrast agent injection on physiological flow in the circle of Willis

X-ray videodensitometry allows in vivo flow measurements from gradients in contrast agent concentration. However, the injection of contrast agent alters the flow to be measured. Here, the temporal, spatial, and inter-patient variability of the response to injection are examined. To this purpose, an injection is prescribed in the internal carotid in a 1D wave propagation model of the arterial circulation. Although the resulting effect of injection is constant over a cardiac cycle, the response does vary with the location within the cerebral circulation and the geometry of the circle of Willis. At the injection site, the injection partly suppresses the incoming blood flow, such that the distal flow is increased by approximately 10%. This corresponds to approximately 20% of the injection rate added to the blood flow during injection, depending on the vascular geometry. In the communicating arteries, the flow direction is reversed during injection. Since the measured flow is not equal to the physiological blood flow, the effect of injection should be taken into account when deriving the flow from travelling contrast agent.

The contrast media iohexol causes vasoconstriction of the proximal left anterior descending coronary artery: implications for appropriate stent sizing

The effect of the contrast agent iohexol on reference vessel size in patients with proximal left anterior descending disease is unknown. Quantitative coronary angiography and intravascular ultrasound were performed in 15 patients with atherosclerotic disease of the proximal left anterior descending. Mean proximal reference vessel diameter was 2.95 +/- 0.59 mm with quantitative coronary angiography and 4.65 +/- 0.66 mm with intravascular ultrasound (P < .05). Intracoronary injection of iohexol resulted in a significant decrease in intravascular ultrasound-measured proximal reference vessel diameter from 4.65 +/- 0.66 mm to 4.47 +/- 0.68 mm (P = .002). Vasoconstrictive response to iohexol in the proximal reference vessel ranged from -0.04 mm to 0.5 mm with a mean of 0.18 +/- 0.16 mm. This study shows that iohexol can cause significant vasoconstriction of the proximal reference vessel in patients with severe disease involving the proximal left anterior descending.

Fatal anaphylactoid reaction following ioversol administration

We report a fatal intravenous ioversol administration in a 60-year old male patient. Although the introduction of new low-osmolar non-ionogenic contrast media with a more favourable efficacy-toxicity balance has diminished the side-effects significantly, everyone involved in radiodiagnostic procedures should be aware of the potential life-threatening effects. Especially patients with risk factors for side-effects should be monitored carefully.

Rebleeding of ruptured cerebral aneurysms during three-dimensional computed tomographic angiography: report of two cases and literature review

Although three-dimensional computed tomographic angiography (3D-CTA) is less complicated and time-consuming than conventional cerebral angiography (CCA) and represents a reliable alternative for evaluating cerebral aneurysms, some patients experience aneurysmal rerupture during 3D-CTA. Two women, 79 and 71 years old, who presented with severe subarachnoid hemorrhage (SAH) underwent 3D-CTA within 3 h after SAH onset. Their images clearly indicated extravasation from their aneurysms. Neither patient recovered from deep coma, and both died within 2 days. We reviewed the literature with special reference to the condition of SAH patients at admission and the interval between SAH onset and 3D-CTA, and discuss serious complications of 3D-CTA study. Although aneurysmal rerupture may reflect the natural course, rerupture during 3D-CTA, especially in SAH patients who are in poor clinical condition during the acute stage, should be recognized as a potentially fatal complication. Their blood pressure must be strictly controlled and factors such as their clinical condition and the interval from the ictus must be considered.

Effects of iodinated contrast media on common carotid and brachial artery blood flow and wall shear stress

The aim of our study was to evaluate the effect of the intravenous contrast media iomeprol on wall shear stress, blood flow and vascular parameters in the common carotid and brachial artery. Thirty outpatients undergoing thoracic or abdominal spiral CT scans were studied. The internal diameter and flow velocity of the common carotid and brachial artery were evaluated by ultrasound, and blood viscosity was measured before and after low osmolality iomeprol (Iomeron 350) injection. The wall shear stress, blood flow and pulsatility index were calculated. To test the differences between groups, the Wilcoxon rank test and Mann Whitney U test were applied. Blood viscosity decreased slightly, but significantly after contrast media (4.6+/-0.7 vs. 4.5+/-0.7 mPa.s, P = 0.02). Contrarily, blood flow and wall shear stress did not change in the common carotid artery, but significantly decreased in the brachial artery (0.9+/-0.4 vs. 0.6+/-0.3 ml/s, P < 0.0001, and 41.5+/-13.9 vs. 35.3+/-11.0 dynes/cm2, P < 0.002, respectively), whereas the pulsatility index significantly increased in the brachial artery (5.0+/-3.3 vs. 7.5+/-5.3, P < 0.001). Iomeprol injection causes blood flow and wall shear stress reduction of the brachial artery; the rise in the pulsatility index suggests an increase in peripheral vascular resistance. Further investigation is needed to evaluate whether these modifications can be clinically relevant.

Hypothesis: Dietary Iodine Intake in the Etiology of Cardiovascular Disease

This paper reviews evidence suggesting that iodine deficiency can have deleterious effects on the cardiovascular system, and correspondingly, that a higher iodine intake may benefit cardiovascular function. In recent years, public health bodies have aggressively promoted sodium restriction as a means of reducing hypertension and the risk of cardiovascular disease. These inducements have led to a general decline in iodine intake in many developed countries. For example, a United States national health survey conducted in the early 1970s observed that 1 in 40 individuals had urinary iodine levels suggestive of moderate or greater iodine deficiency; twenty years later, moderate to severe iodine deficiency was observed in 1 in 9 participants. Regional iodine intake has been shown to be associated with the prevalence of hypothyroidism and hyperthyroidism, where autoimmune hypothyroidism is the more common of the two in regions with moderate to high iodine intake. Both of these thyroid abnormalities have been shown to negatively affect cardiovascular function. Selenium, an important antioxidant in the thyroid and involved in the metabolism of iodine-containing thyroid hormones, may play an interactive role in the development of these thyroid irregularities, and in turn, cardiovascular disease. Iodine and iodine-rich foods have long been used as a treatment for hypertension and cardiovascular disease; yet, modern randomized studies examining the effects of iodine on cardiovascular disease have not been carried out. The time has come for investigations of sodium, hypertension, and cardiovascular disease to also consider the adverse effects that may result from mild or greater iodine deficiency.

Effects of iodinated contrast media on blood and endothelium

The aim of the study was to assess the effects of iodinated contrast media on blood components and endothelium based on experimental and clinical studies and to produce clinically relevant guidelines for reducing thrombotic and hematologic complications following the intravascular use of contrast media. A report was drafted after review of the literature and discussions among the members of the Contrast Media Safety Committee of the European Society of Urogenital Radiology. The final report was produced following discussion at the 12th European Symposium on Urogenital Radiology in Ljubljana, Slovenia (2005). Experimental data indicate that all iodinated contrast media produce an anticoagulant effect and that this effect is greater with ionic contrast media. Several of the in vitro and experimental in vivo studies on haematological effects of contrast media have not been confirmed by clinical studies. Low- or iso-osmolar contrast media should be used for diagnostic and interventional angiographic procedures, including phlebography. Meticulous angiographic technique is the most important factor for reducing the thrombotic complications associated with angiographic procedures. Drugs and interventional devices that decrease the risk of thromboembolic complications during interventional procedures minimize the importance of the effects of contrast media.

Open four-compartment model in the measurement of liver perfusion

RATIONALE AND OBJECTIVES

The goal was to improve informativeness in the determination of liver perfusion with a clinically available iodinated computed tomography (CT) contrast agent by developing open multicompartmental modeling.

MATERIALS AND METHODS

Contrast-enhanced functional CT (fCT) examinations were conducted with temporal resolutions of 200-500 msec to 6 New Zealand White rabbits. First, we applied conventional open two-compartment model for the determination of arterial and portal blood flows (FA and FP), blood and interstitial volume fractions (fb and fi), and capillary permeability-surface area product (PS) of liver parenchyma. Then, we improved the modeling of vascular physiology by developing three- and open four-compartment models. For comparison, conventional single-compartment model was applied. We determined FA and FP also by using the peak-gradient method.

RESULTS

Conventional two-compartment model yielded identical fittings with single-compartment model and does not provide unique solutions for fb and fi. The presented open four-compartment model provided FA and FP values of 0.40 +/- 0.19 and 1.99 +/- 0.57 mL/min/mL (tissue), fb and fi values of 0.30 +/- 0.05 and 0.19 +/- 0.04 mL/mL (tissue), and PS values of 4.0 +/- 1.7 mL/min/mL (tissue). FA and FP are in a good agreement with those derived by using the peak-gradient method.

CONCLUSIONS

With the use of clinical extracellular iodinated CT contrast agent, the presented open four-compartment model provided physiological arterial and portal blood flow values and is also a potential tool in the assessment of blood and interstitial volume fractions and capillary permeability-surface area product. Moreover, the model requires neither measurements from hepatic vein or from other organs nor visual determination of arterial or portal phase.

Contrast media: interactions with other drugs and clinical tests

Many patients with multiple medical problems who are receiving a variety of drugs are investigated with imaging techniques which require intravascular contrast media. The Contrast Media Safety Committee of the European Society of Urogenital Radiology therefore decided to review the literature and to draw up simple guidelines on interactions between contrast media and other drugs. An extensive literature search was carried out and summarized in a report. Based on the available information, simple guidelines have been drawn up. The report and guidelines were discussed at the 11th European Symposium on Urogenital Radiology in Santiago de Compostela. Contrast media may interact with other drugs, and may interfere with isotope studies and biochemical measurements. Awareness of the patient drug history is important to avoid potential hazards. Simple guidelines are presented.

Prevention of contrast media nephrotoxicity--the story so far

Contrast media nephrotoxicity (CMN) in patients with pre-existing renal impairment remains a clinically significant problem. The first step to reduce the chance of CMN is to identify patients at risk through the use of screening questionnaires and renal function measurement. Patients at risk requiring injection of contrast medium (CM) because of important clinical indications should receive a small dose of either non-ionic iso-osmolar dimeric or non-ionic low osmolar monomeric CM and hydration. Intravenous infusion (1 ml/kg body weight/h) of 0.9% saline starting 4 h before CM injection and continuing for at least 12 h afterwards is effective in reducing the incidence of CMN. Prophylactic haemodialysis does not lower the risk of this complication. The value of pharmacological manipulation with renal vasodilators (calcium channel blockers, dopamine, atrial natriuretic peptide, fenoldopam (selective dopamine-1 receptor agonist), prostaglandin E(1), non-selective adenosine receptors antagonist (theophylline), non-selective endothelin receptor antagonist or the antioxidant acetylcysteine has not been fully proven. However, haemofiltration for several hours before and after contrast medium injection offers good protection against CMN in patients with advanced renal disease.

Review article: Effects of radiographic contrast media on the lung

The pulmonary adverse effects of intravascular use of water soluble radiographic contrast media (RCM) include bronchospasm, pulmonary oedema and increase in the pulmonary arterial blood pressure (Ppa). Symptomatic bronchospasm is rare but subclinical increase in airways resistance is common after intravascular injection of RCM. Experimental studies have demonstrated that the low osmolar ionic dimer ioxaglate can induce significant bronchospasm in comparison with other types of RCM. Histamine and endothelin, which are potent bronchoconstrictors and released in response to the administration of RCM, do not seem to mediate the bronchospastic effect of RCM. Pretreatment with corticosteroids or antihistamine does not appear to prevent RCM induced bronchospasm, but the administration of beta(2) adrenergic agonist can abolish this adverse effect. RCM induced pulmonary oedema can be secondary to endothelial injury causing an increase in the permeability of the microcirculation. It may also occur in patients with incipient cardiac failure, when large doses of RCM particularly of the high osmolar type are used. A rise in Ppa induced by RCM seems to be secondary to an increase in pulmonary vascular resistance through direct effects on the pulmonary circulation. Low osmolar non ionic monomers induce the least changes in the pulmonary circulation and should be the contrast media of choice for intravascular use in patients with pulmonary hypertension. The mechanisms responsible for the effects of RCM on airway resistance and pulmonary circulation remain unclear. Intrabronchial administration of high osmolar water soluble RCM is dangerous and can induce severe bronchial irritation and pulmonary oedema. Low osmolar RCM are well tolerated by the lungs following aspiration with minimal histological reaction.

Use of additives to contrast media to improve imaging in plain film and computed tomography urography

RATIONALE AND OBJECTIVES

To investigate the effects of additives to iodinated radiograph contrast agents on image quality in plain film and CT urography.

MATERIALS AND METHODS

Urea (52 mg/mL), iloprost (10, 20, 50, and 100 ng/mL), nifedipine (0.02 mg/mL), papaverine (0.625 mg/mL) and sodium nitroprusside (0.05 microg/mL) were added to commercial iopromide (300 mg/mL) and iotrolan preparations (280 mg/mL) and plain film urograms were obtained at different time points after contrast injection in rabbits and dogs at iodine doses of 300 or 600 mg/kg body weight. The experiments were repeated in rabbits using CT imaging and iopromide or iotrolan plus urea (52 mg/mL) or iloprost (20 ng/mL) and iodine doses of 50 mg/kg body weight.

RESULTS

Urea and iloprost at low concentrations (10 and 20 ng/mL) increased image quality both in plain film and in CT urography. Iloprost at high concentrations (50 and 100 ng/mL), nifedipine, papaverine and sodium nitroprusside decreased image quality. An increase in image quality was accompanied by faster renal elimination of the contrast agent.

CONCLUSION

Image quality in plain film and CT urography might be improved by additives to the contrast medium. More data, particularly on dose-response relationships are needed.

Effects of radiographic contrast media on pulmonary vascular resistance of normoxic and chronically hypoxic pulmonary hypertensive rats

Intravascular radiographic contrast media (RCM) can be associated with significant morbidity in patients with pulmonary hypertension (PH). This study investigated the direct effect of the four main classes of RCM (high osmolar ionic monomer "diatrizoate"; low osmolar ionic dimer "ioxaglate"; low osmolar non-ionic monomer "iopromide"; and iso-osmolar non-ionic dimer "iotrolan") in ex vivo isolated rat lungs perfused with blood at 20 ml min(-1) under basal conditions (air + 5% CO2 ventilation, pulmonary artery pressure (Ppa) 16-20 mmHg) and when Ppa was raised by hypoxic vasoconstriction in normal rats (2-3% O2+5% CO2 ventilation, Ppa increased by 4-14 mmHg). The effects of low osmolar RCM (ioxaglate, iopromide and iotrolan) were also studied in rats with PH induced by chronic hypoxia (3 weeks 10% O2, Ppa 26-36 mmHg). Increasing volumes (0.05 ml, 0.1 ml, 0.3 ml, and 0.5 ml) of RCM, mannitol (osmolar and pH control) or normal saline (volume control) were added to the 10 ml blood reservoir (n=4-9 per group). In normal rats, RCM caused a dose-dependent slow rise in Ppa. The maximum rise in mean+/-SEM Ppa at the cumulative dose of 0.95 ml was ioxaglate 13.8+/-1.6 mmHg>iotrolan 7.3+/-1.7 mmHg=diatrizoate 9.8+/-2.2 mmHg>iopromide 3.0+/-0.8 mmHg (p<0.05). The rise in Ppa induced by ioxaglate and iotrolan was significantly greater than in the mannitol and saline controls (p<0.05). Pre-treatment with endothelin receptor A/B blockade (SB209670) did not abolish the rise in Ppa induced by diatrizoate (0.95 ml) in the normal rat (3.8+/-1.3 mmHg diatrizoate alone and 3.4+/-1.1 mmHg in the presence of 40 microM SB209670, n=5 per group). When Ppa was raised by acute hypoxia, ioxaglate and diatrizoate (0.5 ml) caused a fall in Ppa (percentage fall -53+/-23 and -118+/-10, respectively, p<0.001) while iotrolan and iopromide caused a small further rise in Ppa, which was significant with iotrolan at a dose of 0.3 ml (percentage rise in pressure 14.2+/-2.3, p<0.05). In chronic pulmonary hypertensive rats, RCM (0.95 ml) caused an overall slow progressive rise in Ppa (iopromide 6.8+/-1.7 mmHg< ioxaglate 11.6+/-2.5 mmHg=iotrolan 12.7+/-1.1 mmHg). However, ioxaglate initially induced an acute fall of Ppa (maximum fall 4.22+/-0.9 mmHg, p<0.05) for almost 20 min. In summary, iopromide induced the least change in Ppa of normal and pulmonary hypertensive rats. The pathophysiology of the effects of RCM on the pulmonary circulation remains uncertain.

Comparison of the effects of radiographic contrast media on dehydration and filterability of red blood cells from donors homozygous for hemoglobin A or hemoglobin S

Iodinated radiographic contrast media have traditionally been contraindicated in patients with sickle cell disease because their high osmolality may induce osmotic shrinkage of red blood cells, impair blood flow through the microcirculation, and precipitate or exacerbate a sickle cell crisis. This study investigated that concept by comparing the hematological and rheological effects in vitro of four X-ray contrast media of differing osmolalities: Visipaque (290 mOsm/kg), Hexabrix (600 mOsm/kg), Omnipaque (844 mOsm/kg), and RenoCal-76 (1940 mOsm/kg). Blood was tested from 10 normal and 10 sickle cell donors at drug concentrations of 0, 1, 10, and 30% w/v in an attempt to approximate the relative concentrations of contrast medium to blood that might occur during the bolus-injection and circulation-diluted phases of drug administration. Parameters evaluated included hematology, red cell morphology, and red cell flow resistance through a micropore filter to approximate the microcirculatory effects. Significant hematological effects for both normal and sickle cell donors included a concentration dependent decrease in hematocrit and MCV, and increase in MCHC, all of which varied directly with the osmolality of the contrast media in the order of RenoCal-76 > Omnipaque > Hexabrix > Visipaque. The contrast media had minor effects on red blood cell morphology except for RenoCal-76, 10-30% in which marked echinocytosis was observed. There was no significant increase in the number of irreversibly sickled cells in donors with hemoglobin S. Filterability of red cell suspensions through capillary size pores was impaired in both normal and sickle cell samples in direct proportion to the osmolality of the contrast media, as listed above. Filterability effects were greater for sickle cells than for normal red cells. Visipaque, which was closest to isotonicity, had little effect on red cell volume and had no significant effect on filterability of normal or sickle cells. These results suggest that microcirculatory impairment following infusion of contrast media may occur in sickle patients because of the unusual rheological sensitivity of HbSS red cells, and may be avoided by choice of an isotonic medium.

Effects of radiographic contrast media on proliferation and apoptosis of human vascular endothelial cells

The aim of the study was to determine the effects of radiographic contrast media (RCM) on proliferation and apoptosis of human vascular endothelial cells. Human umbilical vein endothelial cells (HUVECs) were exposed for either 1 min or 15 min to RCM (diatrizoate, ioxaglate, iopromide, iotrolan) at an iodine concentration of 250 mgl ml-1. Controls were complete growth medium (CGM) and saturated mannitol (osmotic control). [3H]thymidine incorporation was used to determine cell proliferation 24 h after exposure. Apoptosis was determined at 1 h and 6 h by terminal uridine nick end labelling (TUNEL), time lapse video microscopy (TLVM) and DNA electrophoresis. Mean proliferation rates (%) (+/- SEM) (p-values compared with the CGM control) at 1 min and 15 min, respectively, were: diatrizoate: 31.9 (10.6), 5.8 (1.5) (p < 0.001); ioxaglate: 48.4 (10.9), 20.4 (4.5) (p < 0.001); iopromide: 63.4 (8.7), 58.2 (10.2) (p < 0.05); iotrolan: 84.7 (7.3), 72.8 (12.4) (p = ns); saturated mannitol 50.5 (9.6), 45.9 (10.0) (p < 0.001). Mean apoptotic indices (%) (+/- SEM) at 1 h and 6 h following 1 min exposure, respectively, were: CGM: 0.25 (0.13), 0.23 (0.08); diatrizoate: 2.18 (0.19), 2.69 (0.34) (p < 0.001); ioxaglate: 1.90 (0.23), 1.69 (0.02) (p < 0.05); iopromide: 0.59 (0.04), 0.33 (0.02) (p = ns); iotrolan: 0.30 (0.07), 0.27 (0.1) (p = ns); saturated mannitol 2.11 (0.24), 1.4 (0.1) (p < 0.05). After 15 min exposure, apoptosis rates at both 1 h and 6 h, respectively, were: iotrolan: 0.29 (0.17), 0.51 (0.16) (p = ns); diatrizoate: 3.19 (0.81), 11.66 (1.75) (p < 0.001); ioxaglate: 1.88 (0.14), 2.87 (0.20) (p < 0.05); iopromide: 1.06 (0.11), 1.52 (0.15) (p < 0.05); saturated mannitol 1.62 (0.09), 4.63 (0.74) (p < 0.05). TLVM and DNA electrophoresis confirmed the occurence of apoptosis after exposure to RCM. In conclusion, saturated mannitol and all tested RCM, with the exception of iotrolan, (diatrizoate > ioxaglate > iopromide) reduced proliferation and increased apoptosis of HUVECs. The effects were more pronounced with ionic RCM and seem to depend on osmolality as well as the chemical structure of these agents. Endothelial injury and apoptosis may be responsible for some of the side effects associated with intravascular use of RCM.