If a cannula is not sited correctly or tissues, contrast may extravasate into the surrounding tissues. Patients who are currently on long-term dialysis can receive contrast without risk. In patients with acute renal failure who require a CT scan with contrast, the clinical team will need to balance the risks and benefits and consider other options for investigation or ways to mitigate the risk, e.g. The risk of renal dysfunction from IV contrast is now thought to be lower than it was once considered. The exact mechanism is not clear, but assessment of U&Es with an eGFR prior to a contrast-enhanced CT scan will be mandatory in many centers. Iodinated IV contrast can contribute to worsening renal function, especially in patients with acute or chronic renal failure. Shellfish allergies were once considered a contraindication for IV contrast, but this is no longer the case. If a patient has had an allergic reaction in the past to contrast, he or she may be pre-medicated with steroids and/or antihistamines. This risk has decreased over recent years with newer contrast agents but is still real. There is a very small risk that some people may have anaphylactic reactions to the contrast media and in those cases, cardiac arrhythmia may result in cardiac arrest. IV contrast is an iodinated liquid that is injected into a vein. According to the ACR Committee on Drugs and Contrast Media, there are no reported complications of intraosseous injections at 5 mL/s 5. Pressure rates must be high due to the intramedullary pressure within the bone. In the context of the critically ill patient where intravenous access is not possible, iodinated contrast can be administered via an intraosseous injection. Smaller peripheral cannula may be acceptable. Some examinations don't require pump injection because delayed post-contrast imaging is all that is required, e.g. An example would be a routine CT of the abdomen and pelvis. Other examinations are less dependent on a tight bolus of contrast and the pump injects at slower (but controlled) rates. In many centers, pump-injection is not permitted through central lines. CT pulmonary angiogram, CT aorta, limb CT angiogram. As time progresses, the column of contrast becomes more dilute, vascular definition decreases and venous artefact increases. Tests that require a large cannula include CT angiograms, e.g. In order to achieve that pressure, the patient needs to have a relatively large cannula in a large vein. This requires a pump that injects up to 300 psi. In some cases, it is important to inject the contrast quickly to keep the bolus tight. NB: typical times in brackets, when contrast reaches those structures Appropriate IV access Once IV contrast has been injected, it flows around the vascular system in a predictable fashion: These are a large group of chemical preparations developed to aid in the characterization of pathology by improving the ability of an imaging modality to differentiate between different biological tissues. Intravenous contrast media used in CT (often shortened to IV contrast) are a type of contrast media.
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