RISK FACTORS FOR CONTRAST ALLERGY

Prior contrast reaction

5x likelihood of subsequent reaction

Atopy (asthma, allergic rhinitis, and allergy to eczema)

2-3x likelihood of contrast reaction than non-atopic pts

Seafood or Shellfish allergy

No predictive value for allergic reaction

Multiple Myeloma or Sickle cell

No risk if normal Cr and using LOCM

Pheochromocytoma

Studies have not found any significant risk of hypertensive crisis with IV injection of LOCM (avoid arterial injection)

Hyperthyroidism (especially in iodine-deficient areas)

Risk of iodine-provoked delayed hyperthyroidism (may occur after 4-6wks) but usually self-limiting

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PREMEDICATE

FOR CONTRAST ALLERGY

Non-urgent study (P.O.)

50mg Prednisone PO 13hr, 7hr, and 1hr before + 50mg Benadryl PO/IV/IM 1hr before

OR

32mg Medrol O 12hr and 2hr before + 50mg Benadryl PO/IV/IM 1hr before

Note: if patient can’t take PO may give 200mg Hydrocortisone IV instead

Urgent study (I.V.)

40mg Solu-Medrol or 200mg Solu-Cortel IV q4hr until contrast study + 50mG Benadryl IV 1hr before

2nd option (less effective): 7.5mg Decadron or 6mg Betamethasone IV q4hr until contrast study + 50mg Benadryl IV 1hr before (use this strategy if patient allergic to Solu-Medrol or allergic to ASA/NSAIDs especially if asthmatic)

Others things to consider

-FInd out what contrast agent caused intial reaction (and avoid using same agent)

-Use Visipaque instead (no recommendation per ACR)

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IODINATED CONTRAST INJECTION PROTOCOLS

Contrast warming

Warming to 37C (human body temp) lowers viscosity and improves flow rate (no contrast warming for Gad)

Rate of injection

-Adults 5cc/s and <300psi

-Peds 2cc/s and <300psi

-20G catheter AC=can handle up to 5ml/s

-22G catheter AC=can handle up to 3ml/s

-Peripheral IV (hand/wrist)=can handle up to 1.5ml/s

-9.5-10F central catheter=can handle up to 2.5ml/s

Catheters approved for power injection

-PICC (Power PICC, Cook Spectrum, Morpheus, Narilyst)
-PORT (Smartport “scalloped edges”, Powerport “triangular”, Power PAC port “CT” label)

-CVC (Arrowgard Blue Plus, Power Hickman tunneled, Power Hohn)

-Dialysis catheter (generally not used unless BARD Trialysis)

Intraosseous (IO) line

Power injection is possible for FAST1 and EZ-IO catheters; rate up to 5ml/s (max PSI 300); need to give local anesthesia with Lidocaine prior to injection for pain (see ACR guide for details)

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AIR EMBOLISM

Signs

Air bubbles within MPA, RV, and intracranial veins

Symptoms

-Air hunger, SOB, cough, chest pain, pulmonary edema, tachycardia, hypotension, expiratory wheezing

-Neuro symptoms due to stroke or decreased cardiac output, or paradoxical air embolism (higher risk if R-to-L shunt)

Treatment

-Place left lateral decubitus (left side down to keep bubbles within right heart)

-100% oxygen via mask

-Hyperbaric oxygen therapy

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EXTRAVASATION

Evaluation

-Volume of non-ionic contrast extravasated

-Ask about symptoms like pain, burning, paresthesia

-Look for erythema, skin integrity and erythema, capillary refill, distal sensations

-Mark edge of edematous skin with marker for reference

Treatment

-Elevation of extremity (above level of heart to promote resorption)

-Cold compresses (aid with pain relief while warm compresses aid in resorption and in improving blood flow)

-Give written instructions (for follow up if worsening signs/symptoms)

-Consider surgical consult (if large volume >100ml and signs/symptoms of compartment syndrome or skin breakdown)

Complications

-Skin breakdown (blistering or ulceration or necrosis)

-Compartment syndrome

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CONTRAST-INDUCED NEPHROPATHY (CIN)

Diagnosis

-Sudden deterioration in renal function within 48hrs of iodinated contrast (≥50% increase in Cr or absolute increase of ≥0.3)

-Avoid IV contrast if eGFR <30 or if patient is in acute renal failure (no risk if dialysis-dependent ESRD)

-Does not occur with Gad

-Incidence of CIN from cardiac angio (intra-arterial injection) is higher than from contrast-enhanced CT scan (intravenous injection)

Risk factors for CIN

-Advanced age (>60yo)

-Dehydration

-DM

-HTN requiring medical therapy

-Cardiovascular disease

-Multiple Myeloma

-Multiple contrast medium doses within short interval (<24hr)

-Hyperuricemia

-History of renal disease including dialysis, renal transplant, single kidney, renal cancer, renal surgery

When to check Cr

-Check Cr and eGFR within last 1month for outpatients and within 1wk for inpatients if any of following:

-Age >60

-Any risk factors listed above

-Currently taking Metformin (does not increase risk of AKI but rather lactic acidosis if AKI develops)

Contrast elimination

T1/2 of LOCM contrast elimination is 2hrs (takes ~24hrs of nearly all contrast to be eliminated in patient with normal renal function)

Mitigation of CIN

-IOCM (like Visipaque) has no clear advantage over LOCM for renal protection (but some still suggest it)

-IV hydration protocol: isotonic fluid hydration with 0.9%NS or LR 100cc/hr beginning 6-12hrs before and continue 4-12hrs after (oral hydration is less effective)

-No evidence to support use of Sodium bicarbonate and Mucomyst

-Use lower dose of contrast (80cc or less)

-Avoid repeat contrast administration <48hrs

-Some suggest MRI with IV Gad with low-risk for NSF (like Gadavist, Multihance, Prohance or Dotarem) may be better choice than CT as long as eGFR not <30

Some practical pointers

-eGFR ≥45: IV contrast ok

-eGFR 30-45: use ½ dose Visipaque

-eGFR<30: avoid IV contrast (discuss with ordering provider and proceed only if risk outweighs benefits and give IV hydration before/after scan)

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METFORMIN

Use

-Oral anti-hyperglycemic agent to treat patients with non-insulin-dependent DM

-Glucophage, Glucovance, Glipizide (Metaglip), Fortamet, Riomet, Avandamet, Janumet, Prandimet, Actoplus Met etc

Risk

-Decreased renal excretion if patient develops CIN leading to metformin-associated lactic acidosis

-Metformin itself is not a risk factor for developing CIN

When to withhold Metformin

-Patients with acute kidney injury or severe (stage IV or V) chronic renal disease with eGFR<30: withhold Metformin at time of or just prior to contrast injection and restart 48hrs after only after rechecking Cr and making sure renal function is normal

-No need to withhold Metformin if no evidence of AKI or eGFR≥30

-No issues with Gad and Metformin

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PREGNANCY

CT scan and

Iodinated contrast (LOCM)

-Avoid CT abd/pelv and if needed delay until after 1^st trimester if possible

-Teratogenesis threshold of 5rads or 50mSv (pregnancy termination advisable for fetal dose >10rads or 100mSv)

-LOCM are ok in pregnancy

-Contrast crosses blood-placenta barrier and into fetus (excreted by fetal kidney into amniotic fluid and them swallowed but only 1% absorbed from GI tract)

-No risk of neonatal hypothyroidism with nonionic contrast

-Premedication regimen for contrast reaction ok if needed

MRI and

Gadolinium

-MRI OK in all trimesters (no consent needed for MRI without Gad)

-Avoid Gad in pregnancy unless absolutely need (must get consent if used)

-Gad crossed blood-placenta barrier and into fetus (excreted by fetal kidney into amniotic fluid and them swallowed)

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BREASTFEEDING

Iodinated contrast

-Safe for infants (may pump&dump for 12-24hrs)

-<1% excreted in breast milk in 24hrs and less than <1% of contrast ingested by infant is absorbed in GI tract so therefore infant systemic dose is <0.01% of IV dose given to mother

-Milk taste could potentially be altered

Gadolinium

-Safe for infants (may pump&dump for 12-24hrs)

-<0.04% excreted in breast milk in 24hrs and less than <1% of contrast ingested by infant is absorbed in GI tract so therefore infant systemic dose is <0.0004% of IV dose given to mother

-Milk taste could potentially be altered

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CHILDREN

Iodinated contrast

-1.5-2.0cc/kg  for neonates and infants

-24G angiocatheter in peripheral location can be used safely with power injector for rate up to 1.5cc/s (max 150psi)

-Incidence of contrast allergic reaction in children is lower than adults

Gadolinium

-Not approved for children less than 2yrs of age

-Children can develop NSF (avoid Gad if eGFR<30)

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MRI SAFETY

(MRI safe and conditional device list)

MRI safe

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(please refer to www.mrisafety.com for specific device)

-Cardiac valves (mechanical/bioprosthetic) and annuloplasty rings

-Coronary and aortic stents/grafts—can image immediately after placement (true for most passive implants)

-Vascular coils (mostly safe; not aneurysm coils)

-Cardiac closure/occluders (mostly safe; some conditional)

-PICC/CVC

-IVC filter

-Biliary stents

-Penile/testicular prosthesis/implant

-Retinal tack and glaucoma valve (mostly safe)

-Antimicrobial wound dressing (some unsafe)

-Dental implants

-ORIF hardware and joint replacements

-Spinal fixation hardware

-Harrington rods (placed after 1960s)

-Permanent makeup and tattoo (may put cold compress over large tattoos during MRI to avoid burn)

MRI conditional (means no hazard in specified MRI environment)

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(please refer to www.mrisafety.com for specific device)

-Embolization coils (risk heating based on length)  

-Atrial appendage clip (Atriclip)

-LVAD (ventriculo-assist device)

-Loop recorders

-Temperature probes

-Epidural or nerve block catheters

-Implantable drug (non-insulin) infusion pumps

-Neurostimulators (deep brain, spinal, peripheral vagal nerve)

-Eye/ocular/eyelid prosthesis/implant

-IUD and Essure

-Dobbhoff tube

-VP shunt valve

-Pectus bar implant (sternal)

-EEG electrodes

MRI unsafe

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(please refer to www.mrisafety.com for specific device)

-Aneurysm clips/coils (some are conditional but need name/type/model/material information)

-Intra-ocular metallic foreign body

-Pacemaker/ICD (mostly unsafe; some are conditional)

-Transvenous temporary pacers or retained/abandoned transvenous pacing wires (epicardial wires ok)

-SG catheter (some conditional) and IABP

-Implanted stimulators (bone growth and ?TENS)— neurostimulators are conditional

-Implanted insulin infusion pumps (other infusion pumps are conditional)

-EKG electrodes/wires

-Medicinal patch (NTG, nicotine, hormonal, etc)

-Pill or capsule camera (for endoscopy)

-Breast tissue expanders

-Shrapnel/bullet/metallic fragments (assume all are ferromagnetic; need to assess location/proximity with respect to vital organs; safe if subcutaneous and away from vessels/nerves or embedded in bone; heating usually not an issue with smaller fragments)

-Hearing aids (remove) and cochlear implants (some are conditional; external component always have to be removed)

-Prosthetic limbs (with microprocessors)

-External fixators (including Halo device)

-Magnetically adjustable ortho implants like NuVasive Intramedullary rod

-Scoliosis hardware

-Body piercing (needs to be removed if ferromagnetic)

-Linx reflux management beads

-Triggerfish contact lens sensor for IOP monitoring

Claustrophobia

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-0.5-2.0mg Ativan PO one hour before exam

-Not allowed to drive x12hrs

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MAGNETIC: Iron, cobalt, carbon, steel (in certain forms), nickel .

NON-MAGNETIC: aluminum, brass, bronze, copper, chromium, gold, sliver, bronze, platinum, lead, lithium, mercury, tin, titanium, tungsten, zinc 

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GADOLINIUM

Contraindications

-Not approved for children less than 2yrs of age

-Avoid in pregnancy unless absolutely needed

-T1/2 (like LOCM) of elimination is 2hrs (takes ~24hrs of nearly all contrast to be eliminated in patient with normal renal function)

Adverse reaction

-Pain at injection site, nausea/vomiting, headache, paresthesias, dizziness

-No cross-reactivity btwn gad and iodinated contrast

-Asthmatic are at higher risk

-No definite risk of vaso-occlusion in sickle-cell dz

-Less toxic than iodinated contrast in case of extravasation

NSF

-Avoid Gad in patients with eGFR<40

-Risk factors (check eGFR): age>60, dialysis, renal transplant, single kidney, renal surgery, history of renal cancer, HTN, DM

-For inpatient, prefer Cr and eGFR within last 2days

-For outpatient, prefer Cr and eGFR within last 6wks and for those with prior eGFR<60 prefer within last 1wk

-In emergent setting if Gad is given to patient on dialysis (use lowest dose possible), plan to dialyze as soon as possible following Gad administration (hemodialysis is better than peritoneal dialysis)

-Fibrosing disease primarily affecting cutaneous/subcutaneous tissues with initial symptoms of sin thickening and pruritis which can progress to contractures and joint immobility (can be also be fatal)

-Develops within days to months after exposure

-Related to dissociation of Gad from chelate and in patients with severe renal disease there is delayed clearance and upon binding to anions like phosphate dissociated Gad can deposited in tissues as an insoluble precipitate

-Most cases in patients with significant acute/chronic renal disease (eGFR<30) or on dialysis who receive

 -Most cases of NSF with Omniscan, Magnevist, Optimark

-Few if any cases of NSF with Group II agents like Multihance, Prohance, Gadavist, Dotarem

-Unknown for newer Group III agents like Ablavar and Eovist

Practical pointers

-eGFR >40: Give Gad

-eGFR 30-40: check for any trend of acute renal failure (avoid if acute renal failure); use half dose (single dose 0.1mmol/kg); use Gad agent with fewest NSF cases like Multihance etc; consider written consent

-eGFR <30 or on dialysis: Don’t give Gad unless absolutely needed (must obtain consent)

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ORAL CONTRAST

Barium

-Like Readi-CAT II (CT scan), EZ paque (SBFT), EZ HD (for double contrast UGI), Liquid Polibar plus (BE) etc

-Avoid if there is risk of leak into mediastinum or peritoneum

-Preferred over water-soluble contrast if patient is at risk of aspiration (HOCM worse than LOCM if aspirated)

-For leak study, start with water-soluble contrast first and if negative then try barium which can help detect small leaks

-Can be used in diluted form for CT scan “Readi-Cat II” (images just as good as water soluble contrast) especially if patient is allergic to iodinated contrast

HOCM water-soluble

IONIC iodinated contrast

-Like Gastroview and Gastrografin

-Avoid if history of severe reaction to iodinated contrast especially if compromised mucosal protection in setting of active IBD since 1-2% can be absorbed and excreted into urine 

-Avoid if risk of aspiration (use barium or LOCM instead)

-Used for suspected bowel perforation or leak (bowel fistula, sinus tract, or abscess); to confirm percutaneous feeding tube position; SBO with timely surgery anticipated

-For fluoro studies, can be used undiluted in adults but should be diluted for children or elderly to avoid fluid shifts

-Always dilute for CT scan (mix 5cc in 500cc water bottle and have them drink over 15min  and scan 1-2hr later)

LOCM water-soluble

NON-IONIC iodinated contrast

-Like Isovue-370, Ultravist-300, Visipaque-320, Omipaque etc

-All agents used for IV contrast can be given safely PO or PR as off-label use (Omnipaque 240/300 is actually FDA-approved for PO use for CT and Omnipaque 350 for fluoro studies)

-mix 50cc in 1L water

-Avoid if history of severe reaction to iodinated contrast especially if compromised mucosal protection in setting of active IBD since 1-2% can be absorbed and excreted into urine 

-Regarded safe in patients with risk of aspiration

-Can be given undiluted but need to be diluted for CT to reduce streak artifact

-Only benefit over HOCM agents is reduced-risk of contrast-related pneumonitis in aspiration-prone patients and taste is more palatable if given undiluted (especially in patients with nausea)

-Most CT scanner use PO water-soluble agents (LOCM Omnipaque if aspiration risk or diluted HOCM Gastrografin if no aspiration risk) for PO use in ER/inpatients and diluted barium (readi-CAT II) for outpatients

-Some CT scanners avoid stocking any HOCM agents like Gastroview or Gastrografin for PO use to avoid potential mis-administered via IV

Volumen

-Contains very small amount of barium and sorbitol to promote luminal distention and limit reabsorbtion of water (CT and MR enterography)

-20 HU attenuation on CT and low intensity on T1 and T2 sequences

-As good as PEG but less side effects

-Self-limited side-effects of nausea, cramping, gassiness, and diarrhea

-Ok to given in setting of contained perforations/fistulae

Bowel prep

-Risk of hypokalemia (K<3.5) especially in patients on diuretics without potassium supplements (weakness/fatigue is common and muscle cramping if severe; can get palpitations)

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CONTRAST REACTION

CATEGORIES (ACR)