Introduction
General rule for contrast material injection
Computed tomography contrast material
Coronary CT Angiography
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The injection duration should be as long as or slightly longer than the estimated scan duration. For very short scans, the injection duration should be at least 10 s [5].
Other protocols
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In CT angiography (CTA) protocols, the right heart typically appears washed out. In some clinical settings, it may be desirable to have some opacification of the right heart.
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Triphasic protocols consist of an initial high flow rate contrast injection (3–6 ml/s), followed by a second injection of either a mixture of contrast and saline (3–6 ml/s) or a contrast injection at lower injection rate (e.g., 2 ml/s), followed by a third injection of a smaller volume of saline.
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Regarding the protocol for the evaluation of delayed enhancement, further studies are required.
Magnetic resonance contrast material
Adverse effects of iodinated and gadolinium contrast medium
Patient selections and preparation strategies
Risk factors for adverse intravenous contrast material reactions
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The history obtained should focus on identification of factors that may indicate either a contraindication to contrast media use or an increased likelihood of a reaction.
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Severe, life-threatening reactions, although rare, can occur in the absence of any specific risk factors with any type of media [1].
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Risk factors for adverse reactions to contrast media are summarized in Table 1.Table 1Risk factors for adverse intravenous contrast material reactionsIodinated contrast mediaGadolinium contrast mediaPatients at increased risk of reactionaPrevious moderate or severe acute reaction to iodine contrast agentPrevious moderate or severe acute reaction to gadolinium contrast agentAsthmaAsthmaSignificant allergiesaSignificant allergiesaSignificant cardiac diseaseHyperthyroidism or other thyroid diseasebMultiple myelomac
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In pregnant patients, it is unclear how iodinated or gadolinium contrast agents will affect the fetus, these agents should be administered only with extreme caution. Free iodine in radiographic contrast medium given to the mother has the potential to depress fetal/neonatal thyroid function. Neonatal thyroid function should be checked during the 1st week if iodinated contrast media have been given during pregnancy. No effect on the fetus has been seen after gadolinium contrast media [22].
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In lactating patients, breast feeding may continue normally when iodinated or gadolinium agents are given to the mother [22].
Preparation strategies
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For patients at increased risk of reaction, consider an alternative test not requiring the agent. For the evaluation of coronary artery, non-contrast MR angiography can be an alternative examination [23].
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There is no concrete clinical evidence on the effectiveness of use of premedication in patients undergoing contrast enhanced CT or MRI examinations.
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However, the premedication is preferable in patients at higher risk for an acute allergic-like reaction.
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If the radiologists does intend to use premedication then a useful option can be prednisolone 30 mg orally, given 12–2 h before the contrast medium [2].
At the time of examination
To reduce the risk of adverse reactions
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Some of the strategies to avoid contrast media induced adverse events are listed in Table 2.Table 2Strategies to reduce the risk of contrast medium induced adverse reactionsIodinated contrast mediaGadolinium contrast mediaUse a non-ionic contrast mediumUse a different gadolinium contrast agent for previous reactors to contrast mediumUse a different iodinated agent for previous reactors to contrast medium
Extravasation
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Inappropriate injection site (small vessels),
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High volume of contrast media or high osmolar contrast media.
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Use of power injectors.
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Most injuries are minor.
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In severe cases, ulceration, soft tissue necrosis or compartment syndrome may be observed.
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A compartment syndrome is more likely to occur after extravasation of larger volumes of contrast media [29]; however, it also has been observed after extravasation of relatively small volumes, especially when this occurs in less capacious areas (such as over the ventral or dorsal surfaces of the wrist).
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Use appropriate sized plastic cannula placed in a suitable vein to handle the flow rate.
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A test injection with normal saline.
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Use non-ionic iodinated contrast medium as far as possible.
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Conservative management (limb elevation, use of ice packs) is adequate in most cases.
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Close clinical follow-up for several hours is essential for all patients in whom extravasations occur, since the severity and prognosis of a contrast medium extravasation injury are difficult to determine on initial evaluation of the affected site.
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An immediate surgical consultation is indicated for any patient in whom one or more of the following signs or symptoms develops: progressive swelling or pain, altered tissue perfusion as evidenced by decreased capillary refill at any time after the extravasation has occurred, change in sensation in the affected limb, and skin ulceration or blistering.
Type of adverse reactions
Acute adverse reaction
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The classification of severity of reactions to contrast media has been shown in Table 3.Table 3Classification of severity of reactions to contrast mediaMinorModerateSevereNauseaFaintnessHypotensive shockVomiting (Limited)Vomiting (Severe)Pulmonary edemaPruritisUrticaria (Profound)Respiratory arrestDiaphoresisFacial edemaCardiac arrestLaryngeal edemaConvulsionsBronchospasm
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The majority of adverse side effects are mild non-life-threatening events that require only observation and supportive treatment.
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Severe adverse side effects, however, may have a mild or moderate prodrome. Nearly all life-threatening reactions occur immediately or within the first 3 h after contrast media injection [30].
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Prediction of occurrence or severity is impossible, although there are some known risk factors, and anticipation and vigilance are critical [31].
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Mild reactions do not require treatment, but, as noted, they may presage or evolve into a more severe reaction. Any patient with any reaction should, therefore, be observed for 20–30 min, or as necessary, to ensure clinical stability and recovery.
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Moderate adverse events, by definition, are not immediately life-threatening (although they may progress to be so) but often require treatment.
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Severe adverse events are potentially or immediately life-threatening.
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Serious contrast reactions are rare and have occurred in 1 or 2 per 1,000 (0.1–0.2%) intravascular injections of HOCM and in 1 or 2 per 10,000 (0.01–0.02%) IV injections of LOCM [1]. In a report from Asia, this frequency was 0.22% of intravascular injections of ionic and 0.04% of non-ionic IV injections [33].
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The management for acute adverse reactions is the same with generalized anaphylactoid reaction. This is summarized in Table 4.Table 4Management plan for contrast medium induced acute adverse reaction1. Call for resuscitation team2. Suction airway as needed3. Elevate patient’s legs if hypotensive4. Oxygen by mask (6–10 l/min)5. Intramuscular adrenaline (1:1,000), 0.5 ml (0.5 mg) in adults. Repeat as needed. In pediatric patients 0.01 mg/kg to 0.3 mg (max. dose)6. Intravenous fluids (e.g. normal saline, lactated Ringer’s)7. H1-blocker e.g. diphenhydramine 25–50 mg intravenously
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β-blockers may impair the response to treatment of bronchospasm induced by contrast medium.
Delayed reactions
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An adverse reaction which occurs 1 h to 1 week after contrast medium injection.
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The incidence of delayed adverse cutaneous reactions has been reported to range from 0.5 to 2% [39].
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The main types of delayed reactions are given in Table 5.Table 5Characteristics of contrast medium induced delayed adverse reactionsIodinated contrast mediaGadolinium contrast mediaLate adverse reactionsMainly skin rashesNone describedVery late adverse reactionsThyrotoxicosisNephrogenic systemic fibrosis(Patients with untreated Graves’ disease)
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Relatively common symptoms are nausea, vomiting, drowsiness, headache, and pruritus without urticaria, all of which are self-limited and many of which are self limiting and do not require any therapy [39].
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Skin reactions are true late adverse reactions. They are usually mild to moderate and self limiting. Delayed cutaneous reactions are not, however, associated with other acute adverse events such as bronchospasm or laryngeal edema.
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The management of late adverse reactions is identical to that of other drug induced skin reactions.
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Delayed cardiopulmonary arrest has also been reported, but this and other severe systemic reactions are probably related to etiologies other than the contrast media.
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Currently, very late reactions to gadolinium media in the form of nephrogenic systemic fibrosis (NSF) are a major concern, and are dealt with in detail in chapter D.
Contrast-induced nephropathy (iodinated contrast medum)
Risk factors for adverse intravenous contrast medium induced nephropathy
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The major risk factors for CIN is given in Table 6.Table 6Risk factors for contrast medium induced nephropathyPatient relatedPre-existing renal insufficiency (serum creatinine level > 1.5 mg/dl; Especially, patients with eGFR less than 30 ml/min)Diabetes mellitusDehydrationCardiovascular diseaseAge over 70Use of diureticsContrast medium relatedHigh osmolality agentsLarge doses of contrast medium
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Serum creatinine values should be measured within 7 days of contrast media administration.
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There is no universally agreed upon threshold of serum creatinine elevation (or degree of renal dysfunction) beyond which iodinated contrast media should not be administered.
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Serum creatinine has limitations as an accurate measure of renal function because it is influenced greatly by the patient’s gender, muscle mass, nutritional status, and age.
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Direct measurement of GFR with insulin or a similar clearance marker would be preferable, however, generally impractical.
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However, these equations are less accurate for Asians, with greater bias at estimated GFR (eGFR) less than 60 ml/min/1.73 m2 [3]. This difference would be accounted for by the difference in muscle mass. African-American people probably have a greater muscle mass than Asian. Interestingly, the correction coefficients for the modification of the MDRD Study equation were considerably different even among patients of Asian origin. For example, the correction coefficient for patients of Chinese origin was 1.233 [4] and that for patients of Japanese origin 0.808 [3].
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The establishment of GFR-estimating formulae specific for patients of different race is required. For example, in Japan, new formula is recommended as follows; eGFR (ml/min/1.73 m2) = 194 × Serum creatinine−1.094 × Age−0.287 × 0.739 (if female) [3].
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Metformin is excreted unchanged in the urine. In the presence of renal failure, either pre-existing or induced by iodinated contrast medium, metformin may accumulate in sufficient amounts to cause lactic acidosis. Depending on serum creatinine level, metformin will have to be stopped either before or at the time of contrast medium administration.
Prevention or amelioration
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Consider an alternative imaging method not using iodinated contrast media. For the evaluation of coronary artery, non-contrast MR angiography can be an alternative examination [23].
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Stop nephrotoxic drugs, mannitol and loop diuretics at least 24 h before [44].
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Start hydration. A suitable intravenous regime is 100 ml/h of normal saline beginning 12 h before and continuing 12 h after examinations. In hot climates the volume should be increased [45].
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Stop metformin from the time of contrast medium administration or 48 h. Only restart metformin if serum creatinine remains normal or unchanged 48 h after contrast medium.
At the time of examination
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Use low or iso-osmolar contrast media.
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Use the lowest dose of contrast medium consistent with a diagnostic result.
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Continue hydration for at least 6 h [49].
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In patients suffering from end-stage renal disease, there is no need for urgent dialysis [50].
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Correlation of time of the contrast medium injection with the hemodialysis session in dialysis patients is unnecessary [50].
Nephrogenic systemic fibrosis (gadolinium contrast media)
High risk | Low risk |
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Patients with chronic kidney disease (CKD) 4 and 5 (eGFR < 30 ml/min/1.73 m2) | Patients with CKD 3 (30 ml/min/1.73 m2 < eGFR < 60 ml/min/1.73 m2) |
Patients on dialysis | |
Patients with acute renal insufficiency in the perioperative liver transplantation period |
Preparation strategies
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In patients with already being dialyzed.
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In patients with eGFR < 30 ml/min/1.73 m2, who are not on chronic dialysis.