Contrast media are widely used in imaging, normally with CT, MRI, X ray and more late by ultrasound. Iodinated contrast media is the most common contrast agent used and help in separating between normal and pathological countries. common indicant for contrast media, including inflammatory conditions, infective or neoplastic. However, endovenous contrast is shown when the contrast will increase the diagnostic value. In patients with impaired nephritic map, non-contrast scans or alternate imaging scrutiny can supply equal diagnostic information.
Iodinated contrast media
Iodine-based agents iodobenzoic acerb compound 2,4,6-tri. Intravascular disposal of iodized contrast media followed by a subdivision that is fast to the extracellular infinite, the volume of H2O that moves into the circulation and so chiefly through nephritic elimination. iodinated contrast media classified as non-ionic and ionic.These may hold a high osmolality ( ionic monomer ) or a low osmolality ( ionic dimer, non-ionic monomer iopromide for illustration, and non-ionic dimer ) . Contentss osmolality, viscousness and I contrast media are closely related. Side effects increased with higher osmolality. Iodine content is non an independent index of inauspicious events.The non-ionic dimers are preferred because of lower osmolality and less.But chemotoxicity they are more resilient than the non-ionic monomer, and more expensive.
Non-ionic agents
Iopamidol is a non-ionic monomer is used that is two times the plasma osmolality, iodine concentration 300 milligram / milliliter. Iodixanol is a non-ionic dimer, and the iodine concentration of 300 milligrams / milliliter was close to plasma osmolality ( 290 m Osmol / kilogram ) .Due to higher costs, which are used selectively to review at any osmolality can impact the quality review ( eg, CT angiography and coronary bosom disease lower appendage angiography for terrible ischaemia ) .
TYPES OF CONTRAST MEDIA
There are two types of contrast media, negative contrast media ( more radiolucent than environing tissues ) and positive contrast media ( more radiopaque ) . They achieve this difference by absorbing less or more severally of the incident radiation than do the surrounding tissues.
Negative contrast surveies will demo the location, size and wall thickness of the organ and will demo pronounced wall thickener and big luminal filling defects such as multitudes or foreign organic structures. They give small information about the mucosal surface, smaller make fulling defects such as vesica concretion may be overexposed and little cryings in the wall may be missed.
Positive contrast surveies give little more information than negative contrast surveies but are the best manner of observing a little defect in the wall of the organ, as minor contrast escape is easy seen.
Double contrast surveies use a little sum of positive contrast medium to surface the mucosal surface of a hollow organ such as the vesica, followed by distention with air. This gives much better mucosal item than a positive or negative survey entirely, and will besides more faithfully demo little filling defects in the puddle of residuary positive contrast medium.
NEGATIVE CONTRAST MEDIA
The most normally used negative contrast agent used in veterinary skiagraphy is room air. It is used chiefly in the vesica ( pneumocystogram ) but can besides be used in the gastro-intestinal piece of land ( pneumogastrogram, pneumocolon ) and in articulations ( negative arthrogram ) .
POSITIVE CONTRAST MEDIA
Barium and iodine readyings are the commonest positive contrast media, looking radiopaque due to their high atomic Numberss ( 56 and 53 severally ) . Barium is presented as Ba sulfate and I as complex organic molecules.
Ionic agents
ionic contrast media contraindicated for intrathecal usage. Merely iotroxate, which binds reversibly to plasma proteins advance the elimination of gall, is approved for endovenous cholangiography in Australia.
Non-iodinated contrast media
These agents are largely used in ultrasound ( microbubble readying ) and MRI MRI.The agents such as Gadolinium is paramagnetic and shorten the T1 relaxation time.They sometimes used in digital angiography decrease in persons allergic to iodized radiographic contrast media. a higher volume of contrast needed for sufficient declaration.
Carbon dioxide is besides used for digital angiography when compared with iodized decrease is contraindicated. However, important proficient restrictions. This can non be used for angiography in the stop or when a shunt right-to-left, to forestall the happening of ischaemic encephalon of the bubble.
Security
Although contrast media are by and large safe, side effects sometimes occur.
Hypersensitivity reactions
Hypersensitivity reactions to contrast media, including E anaphylactic IgE-mediated and non-Ig, with mast cell activation, curdling, quinine and complementary mechanisms, enzyme suppression and thrombocyte collection. 1
mild reactions to moo osmolar contrast media media occurs in less than 3 % of patients and consisted of tegument roseola, sickness, blushing or hypersensitivity urtikaria.reaksi moderate and terrible, including bronchospasm and wheezing, atrophedema, coronary arteria cramp, hypotension, cardiac arrhythmias, hilang.Sebaliknya consciousness of bosom failure and terrible reactions are rare, occur in less than 0.04 % non-ionic iodized contrast injection. Deaths due to contrast media reaction is low ( less than one decease in 100 000 patients ) . 2, 3
Inside, parental decease associated with contrast media disposal was significantly higher. Childs are more sensitive to alterations in fluid volume associated with contrast disposal.
Even little doses can do the injection of iodized contrast reaction.Test no reaction recommended.The reaction may happen instantly, but was postponed after an hr or sometimes a hebdomad can besides occur.These reaction ( 2-5 % ) , but non for their possible anaphylaxis T cell-mediated and may dwell of urtication, rash angioedema.The makulopapular and related osmolality contrast media reaction.Contrast media that is most serious non-fatal reactions can be prevented by utilizing lowosmolar contrast media.
Hazard factors
Previous reaction to contrast media is the most of import hazard factors and convey the absolute hazard of 20-60 % when exposed to the following. Asthma increases the hazard significantly, particularly the hazard of bronchospasm. Beta blockers have been associated with hypersensitivity and may decline bronchospasm. A history of allergic reactions require several interventions to increase the hazard of acute reaction to iodinated contrast three to five times. Vasovagal reactions may happen during endovenous contrast media.
Medical
If reactions occur, endovenous contrast media must be stopped immediately.Despite mild reactions are frequently self-limiting and decide without specific intervention, a reaction that began during or shortly after injection must ever be regarded as symptoms advancement. Vasovagal reactions are treated with lower organic structure tallness, and 0.6 milligram of atropine as light indicated.Treat delayed hypersensitivity reactions with unwritten antihistamines.
Chemical reactions associated with bronchospasm and wheezing, stridor or laryngospasm and hypotension should be treated with epinephrine, endovenous fluids and O, other antihistamines with or without cortisol. Cannulation may be needed and medicines may be needed to back up the instance for 2-3 yearss berat.adrenalin Intramuscular ( 1:1000 ) is the pillar of intervention for terrible reactions and can be repeated every 5 proceedingss if necessary. The initial dosage for grownups is 0.25-0.5 milliliter for those weighing less than 50 kilograms and 0.5 milliliter for those weighing more than 50 kg.Corticosteroids non utile in the early direction of E-mediated reaction of non-Ig, but is believed to forestall or cut down the symptoms is delayed. Most patients recover from their reaction with no long-run morbidity. 4 Patients who experience terrible reactions should be encouraged to transport Medic Alert card. terrible reactions should be reported to the Office of Drug Safety ( www.tga.gov.au / ADR / bluecard.htm ) .
Patients with perennial reaction to contrast media can non be given so that other modes should be considered for probe. However, when intravascular iodinated contrast must be given, a different agent and should be used for low osmolar and premedication with corticoids for 24-48 hours before the process is widely practiced.
Contrast-induced kidney disease
In this instance, arterial vasoconstriction and nephritic tubular alterations in glomerular hemodynamics because of the quality of plasma oncotic force per unit area caused by nephritic inadequacy kontras.Pada media, acetylcysteine ( a vasodilative and antioxidant ) and fenoldopam ( a vasodilative ) has been studied as a bar scheme with no positive result uncertain. 5
Acute kidney hurt in patients who can non be hydrated and have normal nephritic map having contrast media is less than 4 mL / kilogram. In patients with mild nephritic damage, hydration before contrast media injection normally prevent kidney map diminution.
research options such as non-contrast MRI, ultrasound and digital angiography decrease of C dioxide should be considered in patients with moderate to terrible nephritic damage. dimeric non-ionic contrast media have the advantage of non more than monomer contrast media in relation to contrast-induced nephropathy. 6
Most infirmary based radiology pattern now requires the measuring of serum creatinine and calculated glomerular filtration rate ( GFR ) before injection of contrast media.This because kidney failure is a possible factor in the infirmary and the decease of long-run mortality of older patients with mild nephritic damage. 7 If a GFR less than 60 mL/min/1.72m 2, urged cautiousness and patients should be sufficiently hydrated when iodinated contrast medium Gadolinium or used.
Metformin
Metformin has been associated with some instances of kidney failure and lactic acidosis in patients having contrast media. If contrast media cause nephritic failure, Glucophage, a renally produced, can make toxic degrees cause lactic acidosis. Now it is suggested that Glucophage be stopped at least 12 hours before the contrast survey and will non be extended for at least 36 hours after the process, and longer if the serum creatinine had non returned to the beginning. Alternate Method of patient glucose direction may be needed during that clip period.
Reducing hazard
The most of import factor in cut downing contrast-induced kidney diseases are:
Avoid reiterating the survey on high dosage short interval
equal hydration with endovenous entree if necessary
Low usage of non-ionic contrast medium osmolar
the usage of diluted contrast medium at the lowest practical volume
avoid utilizing the same drugs that can do nephritic vasoconstriction ( anti-inflammatory non-steroid ) .
In most instances, nephritic map returned to the beginning without particular treatment.In terrible instances intervention is the same as for patients with cannular mortification from other causes.
Nephrogenic systemic fibrosis
Gadolinium-based agent associated with nephrogenic systemic fibrosis in patients with down nephritic map. 8, 9 The bulk of instances in people who received high doses for CT or angiography digital Gadolinium decrease in iodized contrast is known as hypersensitivity.
Patients with a GFR less than 30 ml / min are considered at high hazard of nephrogenic systemic fibrosis and the hazard of Gadolinium completely.The should be avoided in patients with GFR over 60 milliliters min / receive low-dose Gadolinium ( 0.1 milliliter / kilogram ) is neglected demands. Research for Gadolinium in patients with mild nephritic damage should be determined by clinical grounds.
Iodinated contrast media and thyroid
iodinated contrast-induced hyperthyroidism is rare. Iodine has no important consequence in patients with normal thyroid map. Patients with multinodular goitre Graves ‘ and the increased hazard, and those with hyperthyroidism should non have contrast.
Patients with thyrotoxicosis may develop thyroid crisis, thyroid map trials and truth will be influenced by media.These contrast intravascular contrast media can besides impact thyroid diagnostic surveies of isotopes up to eight minggu.Pesakit with thyroid carcinoma scheduled for intervention with radioactive I should non have contrast, because can detain the intervention for eight hebdomads.
Contrast media extravasation
New CT angiographic techniques affecting contrast media power injectors, larger volume and higher degrees of injection. Consequently there are somewhat higher incidence of contrast medium extravasation at or near the injection site. In terrible instances, there is a hazard of skin loss, although this is less with a low osmolar agents.
Treatment aims to cut down the metabolic demands of the tegument with cold compresses for 20 proceedingss, and increase the soaking up of high contrast medium and crepe patch.
Decision
Iodinated contrast media are by and large used for imaging with a assortment of diagnostic low-osmolar modalities.The, agents of non-ionic monomer contrast with a really low hazard of serious reactions. Patients should be carefully evaluated for hazard factors, including history of old reactions to contrast media, asthma, medical conditions with peculiar accent on nephritic map and thyroid medicines, and this clip, particularly metformin, and beta blockers. terrible hypersensitivity reactions should be treated as another anaphylactic reaction with Intramuscular epinephrine.
