Category: Neurology — Brain Imaging (CT/MRI), Contrast Media Safety and Procedure Anxiety
The doctor said just a brain scan and home, so why is a needle left in my arm? IV cannulas and contrast dye for brain CT/MRI: why it is placed, why it stays, and after-scan self-care
AI Overview / Quick Answer (BLUF)
The plastic cannula left in your arm is a vein line for power-injecting contrast dye and for giving rescue medicines at once if a reaction occurs; nearly all life-threatening reactions happen within 20 minutes.
Having one does not mean something bad was found
(ACR 2026).
What this page covers, and what to read alongside it
- This page focuses on the cannula left in your arm for a brain scan: why it is placed, how CT and MRI contrast differ, why it stays after the scan, real reaction rates, and after-scan self-care
- Panic or a racing heart before contrast → Panic or anxiety before a contrast injection: what to do
- Stroke warning signs → Stroke and TIA warning signs: BE-FAST
- One-sided numbness that led to a brain scan → One-sided numbness: stroke/TIA, nerves, or panic
A patient’s question: “The doctor said just a brain scan and home, so why did they leave a needle in my arm?”
Direct answer: the cannula is a routine safety step — it is used to inject contrast if the doctor needs clearer images and gives the team a way to give medicines at once if needed. It is often placed before anyone has seen the results, so it says nothing about whether they are good or bad.
Feeling shocked is understandable when nobody explains first — and you have the right to ask what it is for, whether contrast will be injected, and when it can come out.
Red flags — tell staff immediately, or call 1669 (Thailand) if you are already home
Direct answer: if any sign below appears during or after a contrast injection, tell staff immediately while you are in hospital; if you are already home, call 1669 in Thailand (or your local emergency number) or go to the emergency department — this may be a severe reaction or a condition that needs urgent treatment.
Tell staff now / call emergency services
- Throat tightness, hoarse voice, trouble swallowing, or a closing-throat feeling
- Trouble breathing or wheezing, chest tightness with air hunger
- Swelling of the lips, tongue, or face
- Hives or redness all over the body, intense itching that spreads fast
- Light-headedness, feeling faint, or fainting — possible low blood pressure
- Chest pain or an irregular heartbeat
- Heavy or persistent vomiting
- Any new stroke symptom, whatever the scan showed (BE FAST): loss of balance, sudden blurred or double vision, facial droop, one-sided arm or leg weakness, slurred speech — note the time it started. Read stroke warning signs
After going home — see a doctor promptly
- A delayed rash (up to 1 week) that blisters, peels, causes mouth sores, comes with fever, or spreads fast
- Increasing swelling, redness, or pain in the cannula arm, numbness, pale or cold fingers, or blisters
- Passing much less urine or body swelling, especially with known kidney disease
1. Why a cannula (IV / saline lock) is left in when you are “only” having a brain scan
Direct answer: the cannula is a small soft plastic tube in a vein (not a metal needle left in place) with three main purposes: power-injecting contrast, readiness for urgent tests or treatment, and a route for immediate medicines if a reaction occurs — every ACR reaction algorithm starts with “preserve IV access.”
(ACR Manual on Contrast Media 2026)
Why the team places the cannula
- Power injector contrast: imaging blood vessels needs a fast, precisely timed injection. The ACR prefers a 20G or larger cannula for flow rates of 3 mL/s or more, ideally in the elbow crease — so a good vein must be secured in advance, not an ordinary injection needle
- Stroke pathway: if stroke is suspected, CT angiography (CTA) or CT perfusion may follow immediately, and clot-dissolving medicine may be given through the vein — every minute counts, so the line must be ready first
- Emergency medicine route: if you react to the dye, the team can give antihistamines, corticosteroids, fluids, or other medicines at once without hunting for a new vein when blood pressure may be low and veins hard to find
- Placed just in case: many brain CTs are non-contrast (for example after a head injury, or the first stroke CT to exclude bleeding), but emergency departments often place a cannula early in case blood tests, medicines, or further scans are needed
A cannula in your arm ≠ bad news
Placing a cannula is preparation, not a diagnosis. Many people with a cannula finish the scan and go home exactly as the doctor said — what tells you the result is the doctor’s explanation after reading the images. If nobody has explained yet, simply ask: “Is this for contrast, or just in case?”
In the stroke pathway: why CTA is done quickly
The 2019 AHA/ASA guideline calls for non-contrast brain CT first to exclude bleeding before considering IV clot-dissolving treatment within 4.5 hours of symptom onset, and CTA to look for a large-vessel blockage in people who may benefit from clot retrieval (thrombectomy), which in selected patients is possible up to 6–24 hours.
The guideline also states that in people without a history of kidney disease, CTA can proceed before a creatinine result so no time is lost.
(Powers WJ, Stroke 2019)
2. How CT and MRI contrast differ, and what they show
Direct answer: CT uses iodine-based dye (iodinated low-osmolar contrast), which absorbs X-rays, while MRI uses gadolinium-based contrast agents, which change the magnetic signal — different classes that do not cross-react, and MRI does not use “iodine dye” as is often assumed.
Both highlight blood vessels and areas where the blood-brain barrier is damaged, such as tumors, infection, or inflammation.
Iodinated contrast for CT and CTA
Used to image brain vessels (blockages, aneurysms), brain blood flow (CT perfusion), and masses or infection when MRI is not possible. It is excreted by the kidneys, has a blood half-life of about 2 hours, and with normal kidney function is almost completely cleared from the blood within 24 hours.
Gadolinium-based contrast for MRI
Used for tumors, meningeal inflammation, abscesses, active demyelinating disease, and some vascular questions. The dose is far smaller than CT contrast and reactions are rarer. For people with severe kidney disease or on dialysis, the team chooses an ACR group II agent, for which the risk of nephrogenic systemic fibrosis (NSF) is very low or possibly nonexistent.
Why contrast is sometimes skipped and sometimes needed
- No contrast: to look for bleeding, skull fracture, or brain swelling — fresh blood is already visible and contrast could obscure it
- Contrast: to look for blocked or bulging vessels, tumors, abscesses, infection, or inflammation where the blood-brain barrier is damaged
Warm flush, metallic taste, feeling like you wet yourself: normal or not?
MRI gadolinium usually does not cause this flush; you may feel coolness at the injection site. If you feel pain or swelling in the arm during the injection, say so immediately — the ACR advises stopping the injection when a patient reports this.
Comparison table: non-contrast brain CT vs contrast CT/CTA vs brain MRI without contrast vs MRI with gadolinium
| Scan | Typical reasons | Contrast agent | Why a cannula is needed | Approximate scan time | Main risks |
|---|---|---|---|---|---|
| Non-contrast brain CT | Head injury, sudden severe headache, suspected stroke (first step, to exclude bleeding) | None | Not needed for the scan itself, but emergency departments often place one in case of further tests or medicines | Under 1 minute of scanning; about 5–10 minutes in the room | Low-dose radiation; no contrast risk |
| Contrast CT / CTA / CT perfusion of the brain | Finding a blocked vessel in stroke, aneurysm, tumor or abscess when MRI is not possible | Iodinated low-osmolar contrast | Power injection needs a 20G or larger cannula at the elbow crease, plus a medicine route if a reaction occurs | About 1–2 minutes of scanning; about 10–15 minutes including setup | Allergic-like reactions about 0.6%, severe about 0.04%; extravasation about 0.7%; kidney considerations when eGFR is below 30 |
| Brain MRI without contrast | Small strokes, numbness, dizziness, seizures, chronic headache with warning features | None | Often not needed, unless the doctor may decide to add contrast or a calming medicine is required | About 20–45 minutes | No radiation; noise and confined space; metal or implanted devices must be declared |
| Brain MRI with gadolinium | Tumor, infection, meningeal inflammation, demyelinating disease, post-treatment follow-up | Gadolinium-based contrast agents | Contrast is injected mid-scan; also a medicine route if a reaction occurs | About 5–15 minutes added to a plain MRI | Allergic-like reactions about 0.01–0.22%, severe about 0.008%; group II agents for dialysis patients |
Summarized from the ACR Manual on Contrast Media 2026, Powers 2019, and Wang 2007 — scan times are approximate and vary by scanner and hospital.
3. Why the cannula stays after the scan: the 20-minute watch
Direct answer: the ACR Manual states that nearly all life-threatening reactions occur within the first 20 minutes after contrast injection, so teams usually keep the cannula in during observation to give medicines at once — and in the emergency department it may stay until a doctor reviews the images and decides on next steps.
Most reactions are mild.
(Wang CL, AJR 2008)
When reactions happen
- Acute reactions: mostly during injection to within 1 hour, and nearly all severe ones within the first 20 minutes
- Delayed reactions: usually skin rashes, from 30–60 minutes up to 1 week, mostly between 3 hours and 2 days (ACR)
- When it comes out: the team usually removes it before you go home. Don’t remove it yourself, and don’t leave with a cannula still in your arm — ask the nurse when it can come out
How likely is a reaction, really?
The ACR summarizes allergic-like reactions to iodinated contrast at about 0.6%, severe at about 0.04%; for gadolinium agents 0.01–0.22%, severe about 0.008%.
A Michigan series found 545 reactions among 84,928 injections (0.6%): 77% mild, 21% moderate, 2% severe.
At the Mayo Clinic, across 456,930 doses, adverse effects occurred with 0.15% of iodinated and 0.04% of gadolinium doses; hives were the most common
(Hunt CH, AJR 2009),
and a meta-analysis of 716,978 gadolinium administrations found allergic-like reactions at 9.2 per 10,000, severe at 0.52 per 10,000
(Behzadi AH, Radiology 2018).
Iodinated rates from ACR 2026 and Wang 2008; gadolinium rates from Behzadi 2018 — population figures, not a prediction of any individual’s risk.
Contrast reaction severity table: signs, what the team does, and when reactions usually occur
| Grade / type | Signs (per ACR) | What the team usually does | When it usually occurs |
|---|---|---|---|
| Mild: physiologic | Transient warmth or flushing, metallic taste, limited nausea or vomiting, headache, dizziness, anxiety, a vasovagal episode that resolves on its own | Reassurance and observation; medicines are rarely needed | During injection to a few minutes after |
| Mild: allergic-like | Limited hives or itching, limited skin swelling, itchy throat, nasal congestion, sneezing, red eyes | Observation for 20–30 minutes, possibly an antihistamine; the cannula is kept in | Mostly within the first 20 minutes |
| Moderate | Widespread hives, facial swelling without breathing difficulty, throat tightness or hoarseness without breathlessness, mild wheezing, protracted vomiting, isolated chest pain | Medicines through the cannula, such as antihistamines, inhaled bronchodilators, oxygen; some need epinephrine; vital-sign monitoring | Mostly within the first 20 minutes |
| Severe | Face or throat swelling with breathing difficulty, laryngeal swelling, wheezing with low oxygen, widespread redness with low blood pressure, shock, seizure, arrhythmia | Intramuscular epinephrine, oxygen, IV fluids through the cannula, call the resuscitation team | Nearly all within the first 20 minutes |
| Delayed skin reaction | Raised red rash, hives, itching; more common with iodinated contrast; usually mild and self-limited; very rarely blistering or peeling | Antihistamines or topical corticosteroids as prescribed; the allergy is recorded; blisters, mouth sores, or fever need urgent review | 30–60 minutes up to 1 week, mostly 3 hours to 2 days |
Summarized from the ACR Manual on Contrast Media 2026, Brockow 2005, and Christiansen 2002 — not a self-diagnosis tool for allergy.
Premedication and anti-anxiety medicine: not given to everyone
The ACR does not recommend premedication (a corticosteroid plus an antihistamine) just because of other allergies, asthma, or a shellfish allergy. It is reserved for people with a prior reaction to the same class of contrast, whose risk is about 5 times higher.
A systematic review of randomized trials concluded that in unselected patients the benefit of premedication is doubtful
(Tramèr MR, BMJ 2006),
and even among people with a prior reaction, about 569 must be premedicated to prevent one severe reaction
(Mervak BM, AJR 2015).
Anti-anxiety medicine is not routine either — if you are very frightened, tell the team beforehand so the doctor can decide case by case.
The myth: “shellfish allergy means iodine allergy, so no contrast”
Iodine is not an allergen, and people with shellfish allergy have a risk similar to those with other food allergies or asthma, not higher. The same review reported severe reactions at 0.02–0.5%, unrelated to “iodine allergy” or seafood allergy
(Schabelman E, J Emerg Med 2010)
— but always tell the team about every allergy.
A rash after you get home
Delayed rashes affect about 2–3% of people who receive iodinated contrast, usually a raised red rash or hives that fade on their own, and can appear up to 7 days after injection; the mechanism involves T cells
(Christiansen C, 2002).
Photograph the rash, tell the hospital that did the scan so it is recorded, and mention it before any future scan — blisters, peeling, mouth sores, or fever need a doctor at once.
Contrast leaking outside the vein (extravasation)
Across 69,657 iodinated contrast injections, extravasation occurred in 475 (0.7%), usually as swelling or pain in the arm; nearly all adults had minimal or no effects, and serious complications were rare and usually involved large volumes
(Wang CL, Radiology 2007).
The ACR advises elevating the arm above heart level and using cold or warm compresses per staff protocol; there is no clear evidence that one is better.
Does worry or a racing heart before scans happen often, enough to disrupt sleep or keep you from appointments?
Analyze severity and get personalized guidance from our Advisory team.
For throat tightness, breathing difficulty, facial swelling, fainting, or stroke symptoms, tell staff or call emergency services first — no need to take the score first. This score sorts urgency; it is not a diagnostic tool.
Take the Mental-Health Warning-Sign Score (free)
4. After-scan self-care: fluids, kidneys, metformin, breastfeeding, and the cannula arm
Direct answer: with normal kidneys, drink normally or a little more; the contrast is almost fully cleared within about 24 hours — there is no universal 1.5–2 liter rule. People with heart failure, on dialysis, or on fluid restriction should follow their team.
Metformin and breastfeeding usually do not need to stop.
(Davenport MS, Radiology 2020)
How much to drink
The randomized AMACING trial in people with an eGFR of 30–59 found that no prophylactic IV fluids was non-inferior to IV fluids: post-contrast kidney injury 2.6% vs 2.7%, and 5.5% of those given IV fluids had complications from the fluids
(Nijssen EC, Lancet 2017).
The ACR–NKF consensus recommends IV saline to protect the kidneys only for people with acute kidney injury or an eGFR below 30 who are not on dialysis — drinking large amounts is not a universal “flush,” and can be harmful for people on fluid restriction.
When contrast leaves the body, and the kidneys
Both iodinated and gadolinium agents have a blood half-life of about 2 hours and are almost completely cleared from the blood within 24 hours with normal kidney function; urine does not change color.
The risk of iodinated contrast injuring the kidneys was historically overstated because older studies lacked control groups who received no contrast (they could not separate contrast-induced AKI from contrast-associated AKI). Dialysis schedules do not need to change because of a contrast injection
(van der Molen AJ, Eur Radiol 2018).
Metformin
Per the ACR Manual, people with an eGFR of 30 or higher and no acute kidney injury can continue it, with no mandatory repeat kidney test. If the eGFR is below 30 or there is acute kidney injury, doctors usually stop it at the time of the scan, withhold it for 48 hours, and restart after kidney function is rechecked — don’t stop or restart on your own without asking. For standard-dose gadolinium, metformin does not need to be stopped.
Breastfeeding
The ACR states it is safe to continue breastfeeding after both iodinated and gadolinium contrast — the amount of iodinated contrast a baby actually absorbs is less than 0.01% of the mother’s dose, and less than 0.04% of a gadolinium dose passes into milk. If you are still worried, you may pump and discard for 12–24 hours; there is no benefit in stopping beyond 24 hours
(Webb JA, Eur Radiol 2005).
Caring for the cannula arm
- After removal, press gauze firmly for 2–3 minutes (longer if you take antiplatelet or anticoagulant medicines); don’t rub or bend the elbow hard
- Mild bruising is common and usually fades in 1–2 weeks; compresses are optional, not required for everyone
- If there is pain or swelling in the arm during or after injection, it may be extravasation — tell staff, elevate the arm, and follow their advice on cold or warm compresses
- Don’t remove the cannula yourself — the tip can break off or bleed; let the nurse remove it
After-scan checklist table: fluids, cannula arm, metformin and kidneys, breastfeeding, and when to call
| Topic | What to do | Who should do it differently | When to contact the team |
|---|---|---|---|
| Fluids | Drink normally or a little more; eat as usual | Heart failure, dialysis, cirrhosis with ascites, or fluid restriction: follow your team; don’t add extra fluids yourself | More swelling, breathlessness lying flat, or much less urine |
| Cannula arm | Press for 2–3 minutes after removal; mild bruising is normal | On anticoagulants: press longer. After extravasation: elevate the arm and use compresses as instructed | Increasing swelling, redness, pain, numbness, pale cold fingers, or blisters |
| Metformin and kidneys | eGFR 30 or higher and no acute kidney injury: continue | eGFR below 30 or acute kidney injury: doctors usually withhold for 48 hours and check kidney function before restarting | Unsure whether to stop, or no repeat kidney test booked when your doctor asked for one |
| Breastfeeding | Continue after both contrast CT and contrast MRI | Mothers who remain worried: may pump and discard for 12–24 hours; longer is unnecessary | Any worrying change in the baby: consult a pediatrician |
| Symptoms to call about | Watch your skin and breathing for 1 week after contrast | Prior contrast reaction: declare it before every future scan | Throat tightness, breathing difficulty, facial swelling, fainting, stroke symptoms: call 1669 (Thailand) or local emergency services. Blistering rash or fever: see a doctor at once |
Summarized from the ACR Manual on Contrast Media 2026, Davenport 2020, van der Molen 2018, and Webb 2005.
5. Afraid of needles or scans, shocked because nobody explained: how to cope
Direct answer: feeling shocked when a cannula is placed without explanation is a normal reaction. What helps most is to ask the team why the cannula is there, say that you are scared, and breathe slowly — if you have had panic or a racing heart before contrast, read Panic or anxiety before a contrast injection: what to do.
You have the right to ask: short questions you can use
- “Is this cannula for contrast, or just in case?”
- “Which contrast will I get, CT or MRI, and do you need to know about allergies or kidney disease?”
- “What will the injection feel like? Is a warm flush normal?”
- “When can the cannula come out, and what should I watch for at home?”
Slow breathing while waiting and during the injection
- Breathe in through the nose for a count of 4 so the belly rises, then out slowly through the mouth for 6; repeat 5–10 times
- Press your feet into the floor or bed and notice your body weight to bring attention back to the present
- Tell yourself: “The warm flush is just the contrast; it passes in seconds”
- If you feel panic building, say so — the team is already watching and can help faster than silent endurance
Thailand context
- Medical emergencies in Thailand: call 1669 — say when and where you received contrast
- If you have reacted to contrast, ask the hospital to record the allergy and keep the generic name of the agent on a card or your phone to declare every time
- Procedures, coverage, and costs for contrast scans vary by hospital and health scheme — confirm with your hospital
Scientific mechanism (synthesized by the author)
Synthesized by
Asst. Prof. Dr. Norawit Raatpiboon:
iodine has a high atomic number (53), so it strongly absorbs X-rays and iodinated blood appears bright on CT — capturing the brain’s arteries requires the contrast to arrive as a tight bolus within seconds, which needs a power injector through an adequately sized plastic cannula in a large vein, which is why the line is placed in advance.
Gadolinium is a paramagnetic metal that makes nearby water molecules relax faster (T1 shortening), so enhanced areas appear bright on MRI; it is bound to a carrier molecule (chelate) so that free gadolinium does not cause toxicity.
Healthy brain tissue is protected by the blood-brain barrier, so contrast stays inside vessels; where this barrier is damaged by tumor, infection, or inflammation, contrast leaks into tissue and “enhances,” revealing the lesion.
Most allergic-like reactions are not IgE-mediated allergy: the agent directly triggers basophils and mast cells to release histamine, which is why they can occur on first exposure and have nothing to do with “iodine allergy,” while delayed rashes are T-cell–mediated.
Both classes are filtered unchanged by the kidneys with a half-life of about 2 hours — the cannula kept in during the first 20 minutes is a safety insurance for the highest-risk window, not a sign of disease.
Frequently asked questions (FAQ)
The doctor said I’d just have a brain scan and go home, so why was a needle left in my arm?
What stays in your arm is a small plastic tube in a vein, not a metal needle. It lets the team power-inject contrast dye, which needs a good vein and a cannula of the right size, and it gives them a way to give medicines at once if you react to the dye. In the emergency department it is often placed before any results are known, in case you need more tests such as CT angiography or urgent treatment. It is a routine safety step and does not mean something abnormal was found.
Does having an IV cannula mean my brain scan result is bad?
No. The cannula is usually placed before the scan or before a doctor has read the images, so it has nothing to do with the result. Many brain CT scans are done without contrast, but in the emergency department or when stroke is suspected, teams often prepare a line in case more tests or urgent medicines are needed. You can always ask the doctor or nurse why it was placed.
Is the contrast used for CT the same as for MRI?
No. CT uses iodinated contrast, which absorbs X-rays, while MRI uses gadolinium-based contrast agents, which change the magnetic signal. The two classes do not cross-react: a past reaction to one class does not predict a reaction to the other any more than an unrelated allergy does. Always tell the team about any allergy.
I felt a hot flush all over and a metallic taste during the injection. Is that dangerous?
Usually not. A warm flush, a feeling of having wet yourself, or a metallic taste are common physiologic effects of iodinated contrast and fade within seconds to a few minutes. The ACR classifies them as mild reactions. But throat tightness, wheezing, lip or face swelling, or hives all over the body must be reported to the team immediately.
Why wasn’t the cannula removed right after the scan?
Because nearly all life-threatening contrast reactions happen within the first 20 minutes after injection, according to the ACR Manual on Contrast Media. The team usually keeps the line in during observation so medicines can be given at once if needed, and in the emergency department it may stay until a doctor reviews the images and decides on next steps. Don’t remove it yourself; ask the nurse when it can come out.
I’m allergic to shellfish. Can I have contrast dye?
In general, yes. A shellfish allergy does not raise the risk of a contrast reaction more than other allergies do, and iodine is not an allergen. People with unrelated allergies have about a 2 to 3 times higher risk of an already low risk, so the ACR does not recommend premedication just because of a shellfish allergy. If you have reacted before to the same class of contrast, tell the team so they can plan for you individually.
Does everyone need to drink 2 liters of water after contrast?
There is no single number for everyone. With normal kidney function, the contrast is almost completely cleared by the kidneys within about 24 hours, so drink normally or a little more if you have no restrictions. People with heart failure, on dialysis, or on fluid restriction should follow their team’s instructions. IV saline to protect the kidneys is recommended by the ACR and NKF for people with acute kidney injury or an eGFR below 30 who are not on dialysis.
Do I need to stop metformin or breastfeeding after contrast?
Usually not. Per the ACR Manual, people with an eGFR of 30 or higher and no acute kidney injury can continue metformin. If the eGFR is below 30 or there is acute kidney injury, doctors usually stop it at the time of the scan and withhold it for 48 hours until kidney function is rechecked. For breastfeeding, the ACR states it is safe to continue after both iodinated and gadolinium contrast because very little reaches the milk and even less is absorbed by the baby. If you are still worried, you may pump and discard for 12 to 24 hours.
After going home, which symptoms mean I should return to hospital or call emergency services?
Call 1669 in Thailand or your local emergency number, or go to the emergency department at once, for throat tightness, trouble breathing, wheezing, lip or face swelling, hives all over, fainting, chest pain, or heavy vomiting, and for any new stroke symptoms such as facial droop, arm or leg weakness, or slurred speech. See a doctor promptly for a delayed rash within a week that blisters, comes with fever, or spreads fast, for increasing swelling, redness, or pain in the cannula arm, or for passing much less urine.
E-E-A-T and academic citations
Written by Asst. Prof. Dr. Norawit Raatpiboon (ผศ.ดร.นรวิชญ์ ราษฎร์พิบูลย์) — synthesized from the American College of Radiology Manual on Contrast Media (2026), the AHA/ASA guideline, ESUR guidance, and PubMed-indexed research (September 2026).
- ACR Manual on Contrast Media, 2026 edition. American College of Radiology Committee on Drugs and Contrast Media
- Wang CL, et al. Frequency, outcome, and appropriateness of treatment of nonionic iodinated contrast media reactions. AJR Am J Roentgenol 2008 (PMID 18647910)
- Hunt CH, et al. Frequency and severity of adverse effects of iodinated and gadolinium contrast materials: retrospective review of 456,930 doses. AJR Am J Roentgenol 2009 (PMID 19770337)
- Behzadi AH, et al. Immediate Allergic Reactions to Gadolinium-based Contrast Agents: A Systematic Review and Meta-Analysis. Radiology 2018 (PMID 28846495)
- Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med 2010 (PMID 20045605)
- Davenport MS, et al. Use of Intravenous Iodinated Contrast Media in Patients with Kidney Disease: Consensus Statements from the ACR and the NKF. Radiology 2020 (PMID 31961246)
- Nijssen EC, et al. Prophylactic hydration to protect renal function from intravascular iodinated contrast material (AMACING). Lancet 2017 (PMID 28233565)
- Tramèr MR, et al. Pharmacological prevention of serious anaphylactic reactions due to iodinated contrast media: systematic review. BMJ 2006 (PMID 16880193)
- Mervak BM, et al. Rates of Breakthrough Reactions in Inpatients at High Risk Receiving Premedication Before Contrast-Enhanced CT. AJR Am J Roentgenol 2015 (PMID 26102383)
- Brockow K, et al. Management of hypersensitivity reactions to iodinated contrast media. Allergy 2005 (PMID 15647034)
- Christiansen C. Late-onset allergy-like reactions to X-ray contrast media. Curr Opin Allergy Clin Immunol 2002 (PMID 12130948)
- van der Molen AJ, et al. Post-contrast acute kidney injury. Part 2: risk stratification, hydration, metformin and chronic dialysis patients (ESUR). Eur Radiol 2018 (PMID 29417249)
- Webb JA, et al. The use of iodinated and gadolinium contrast media during pregnancy and lactation. Eur Radiol 2005 (PMID 15609057)
- Wang CL, et al. Frequency, management, and outcome of extravasation of nonionic iodinated contrast medium in 69,657 intravenous injections. Radiology 2007 (PMID 17392249)
- Powers WJ, et al. Guidelines for the Early Management of Patients With Acute Ischemic Stroke: 2019 Update. Stroke 2019 (PMID 31662037)
Medical disclaimer
This content provides general education about cannulas left in the arm and contrast injections for brain imaging —
it is not a diagnosis, an interpretation of your scan, or an individual treatment plan. Research figures describe patient groups and do not predict any one person’s risk.
Medicine and agent names on this page are generic or class names, not brand names. Do not stop or start any medicine, including metformin, on your own, and do not remove a cannula yourself.
Procedures and coverage vary by hospital — confirm with your hospital. For throat tightness, breathing difficulty, facial swelling, fainting, chest pain, or stroke symptoms, tell staff, go to the emergency department, or call 1669 in Thailand (or your local emergency number) immediately.