Contrast Agents
Contrast Agents tests selection, dosing, adverse reactions and prophylaxis for iodinated, gadolinium and ultrasound contrast.
Iodinated contrast
Risk factors for contrast-induced nephropathy include eGFR below 30, diabetes, dehydration and heart failure; use the lowest volume, hydrate and avoid repeat dosing. Metformin is generally continued unless eGFR is very low or there is acute kidney injury. Reactions: mild (nausea, urticaria), moderate (bronchospasm), severe (anaphylaxis) - treat with adrenaline, oxygen and fluids and call for help. Premedication with steroids is reserved for prior moderate or severe reactions, not for everyone.
Gadolinium
Group I linear agents carry the highest risk of nephrogenic systemic fibrosis; use group II macrocyclic agents when gadolinium is essential in renal impairment. Gadolinium crosses the placenta; use only if essential in pregnancy.
Worked example
A patient with eGFR 25 needs a liver MRI. The study is justified, so use a macrocyclic group II agent at the lowest dose rather than withholding all gadolinium or using a linear agent.
Traps
Checking creatinine instead of eGFR; premedicating all patients; confusing allergy history with prior reaction severity; using gadolinium in pregnancy without justification; forgetting extravasation management.