Contrast Media

Contrast media

INTRODUCTION & HISTORY Substances which help in better differentiation

between adjacent tissues Contrast media may be positive or negative Substances which increase beam attenuation &

help in better visualization radiologically are called as positive contrast media.

Intravascular iodinated CM introduced in practice by Moses Swick a urologist in 1928

Used selectan and uroselectan : Pyridone ring structures.

Selectan and uroselectan synthesized by Binz & Roth.

Mechanism of action of CM Beam attenuation governed by -ud

I = Io x e d=thickness of substance u=linear coefficient of radiation governed by 1- physical density(at. Wt.) 2- atomic no.(more imp.) u directly propotional to at. Wt. proportional to 3’rd power of at. No.

Mechanism of action of CM Iodine being high atomic no. substance increases the attenuation by increasing the

linear coefficient of radiation .

Why only iodine :1. high atomic no. 532. very tight binding to benzene ring3. Special property of attenuation of

routinely used X ray beams called as “K-edge effect”

Basic Chemistry Triiodinated benzene ring is the

basic constituent of all contrast media.

Benzene ring has 6 carbons numbered 1 to 6 clockwise (Kekule)

Carbon 1 attachment differentiates ionic from non ionics

Iodine attached at position 2,4,6 carbons

Basic chemistry ( contd. )

C3 & C5 have amide attachments to increase solubility and also to reduce protein binding.

At C1 in ionics acidic group with sodium or meglumine is attached

At C1 in non ionics amide group is attached.

Basic properties Iodine to particle ratio : most important

factor governing the attenuation Iodine to particle ratio for various media: ionic : monomer - 3:2 dimer - 3:1

non ionic : monomer - 3:1 dimer - 6:1

Basic properties (contd.)

Osmolality : -Depends on no. of particles so

always higher for ionic media and monomers.

-Contrast media classified as HOCM and LOCM .

-Ionic monomers called as HOCM and rest called as LOCM.

Basic properties (Contd.) Solubility Factors increasing solubility: hydroxyl group amide group salt ( Na / Meg ) Viscosity Depends on : particle size (most imp.) temp solvent

Sodium VS MeglumineParameter Sodiu

mMeglumine

Solubility Less Better

Tolerance Less Better

BBB effect Crosses

Not

Vascular effects

More Less

Viscosity Low High

Diuretic Less Strong

Opacification Better Less

Bronchospasm

No Yes

Constituents

Triiodinated benzoic acid Stabilizers : calcium/ sodium

edetate Buffers : phosphate Preservatives :not disclosed

what is ideal

Low osmolality Low viscosity High water solubility Biological inertness Safety Heat and chemical stability Cost effective

Classification Ionic media : includes : Monomers : Dimers Non ionic media : includes : Monomers : Dimers HOCM and LOCM

Ionic contrast media

Monomers : diatriazoic acid iodamic acid ioglicic acid

iothalamic acid ioxithalamic

acid

Ionic contrast media

Ionic dimers : ioxaglic acid iocarmic acid

Non ionic contrast media

Monomers : iohexol iopamidol ioversol iopromide iopentol

Non ionic contrast media

Dimers : iotrol iotrolan iodixanol

Commonly used preparations Ionic contrast media : - monomers : diatrizoate based German remedies urograffin (60,76) angiograffin(65) Unique ( JB chemicals ) trazograph ( 76,60,plus) May and Baker iothalamate based : conray (280,420)

Commonly used preparations Non ionic monomers : most commonly used

media Nycomed Omnipaque : iohexol Mallinckrodt corporation Optiray : ioversol German remedies Ultravist : iopromide J B Chemicals Lek-Pamidol : iopamidol

Bracco Iopamiro : iopamidol

Commonly used preparations

Non ionic dimers : German remedies Isovist : iotrolan Visipaque : iodixanol

Pharmacodynamics

Excretion by glomerular filtration 95%

Tubular excretion and protein binding negligible

Half life : 30-60 minutes

Contrast media and body system interactions

kidney : conc. of media (5-8 times) Heart : conducting system : ionic CM cause bradycardia d/t Na

content Pumping action : decreases Vessels : damage to endothelium & blood

cells

Contrast media and body system interactions

Brain and myelon : can enter if BBB defective :

chemotoxicity and electrical changes. Thyroid gland : some iodide ions always

present in contrast. causes problems in abnormal thyroid effect takes wks to appear as hormone

production takes time.

Contrast media side effects

Reactions due to osmolality1. Endothelial damage2. Thrombosis and thrombophlebitis3. Damage to BBB4. Vasodilation 5. Vascular pain6. Hypervolumia and CVS side effects

Contrast media side effects

Reactions due to chemotoxicity chemotoxicity occurs due to cations more common with Na than MegDamage can occur to Neurons , myocardium , endothelium , RBCs , kidney

Contrast media side effects

Immunological reactions true allergic reactions are very very rare .

Hence called as anaphylactoid or allegroid reactions .

Basis is 1. Histamine release2. Inactivation of Enzymes especially ACE and

C1 esterase inhibitor3. Activation of protein cascades like

coagullation,compliment and kallikrein systems

Contrast media side effects

Reactions unrelated to media1. pyrogenic reactions ( d/t IL-2,TNF

productions)2. Vasovagal reaction3. Hypertensive attacks in

pheochromocytoma

Contrast media side effects

Limbic system involvement in reactions ( anxiety and fear )

1. Nausea and vomiting 2. Vasovagal reaction3. Temperature elevation cardiac

dysrhythmias4. urticaria

Reactions and management

Minor reactions: 5% Nausea/vomiting : reassure

inj.prochlorperazine (5-10 mg IM) prevent aspiration Mild urticaria observe H1 blocker( diphenhydramine 25-50mg

IM/IV)

Reactions and management Intermediate reactions- 1% extensive urticaria : H1 blocker + H2 blocker Bronchospasm : O2 inhalation MDI B2 agonist inj. Theophylline inj. Epinephrine SC/IV

Reactions and management

Laryngeal edema : O2 inhalation intubation if

requiredinj. Epinephrine

Hypotension : elevate legs monitor pulse & manage

accordingly

Reactions and management

Severe reactions- 0.05%Anaphylactoid reactionsc/b hypotension with tachycardiaIV fluidsInj. Epinephrine (sc/im)Inj. HydrocortO2 inhalation

Reactions and management

Vasovagal reactionsc/b hypotension with bradycardiaO2 inhalationIV fluidsInj. Atropine

Reactions and management

Pulmonary edemaElevate head endO2

Inj. LasixInj. MorphinInj. Hydrocort

Reactions and management

Seizures & convulsionsO2 inhalationPrevent aspirationInj. Diazepam Hypertensive crisisO2

NitroglycerineInj. LasixIf pheochromocytoma, manage

accordingly

Reactions and management

Extravasation of contrast mediaElevation of extremityIce packsPlastic surgery consultation

-if large volume, -skin ulceration or blistering

-worsening symptomsFollow up until resolution

Prevention is always better

Identify high risk patients1. Prior reaction to CM2. Allergic conditions3. Asthma 4. Diabetes mellitus5. Very old and very young6. Paraproteinemia and increased viscosity7. Cardiac disease

Prevention is always better Pre medications required in

I. Previous reaction to CM (11 times high risk)II. History of allergic conditions

MedicationsTab Wysolone 10 mg qid 2-3 daysTab Rantac 150 mg bd 2-3 daysInj Hydrocort 100mg ivInj Hydrocort 100mg iv 24 hrs & 12 hrs before

procedure and 100 mg iv at procedure

Prevention is always better

Proper hydration required inI. paraproteinemic conditionsII.hyperviscocity conditionsDon`t allow any type of dehydrationIV fluids: 500- 1000 ml during

procedure3-3.5 Ltrs orally over next 12 hours

Prevention is always better

Drug adjustmentsDiabetes mellitus: If on Biguanides,stop at least 1 week before- avoids

lacticacidosis.Thyroid disease: continue sulphonylureas for at least 2-3 weeks to avoidhormonal disturbance

Drugs used in Management

Epinephrine 1:1000 (sc/ im) contains 1mg/ml1:10000 (iv) contains 1mg/10ml

Precautious use in Cardiac disease, hypertension & Pt onB-blockers Atropine

0.6-1.2 mg iv monitored by pulse ratePrecautious use in Glaucoma , BHP Corticosteroids: not useful in acute reactions

Hydrocort 100 mg iv Prednisolone 10 mg oral

Drugs used in Management

Antihistaminics: both H1 & H2 blockers usedDiphenehydramine (H1) 50 mgCimetidine (H2) 300 mg

B2 agonists: used by MDISalbutamol, terbutaline

Lasix: 40 mg ivmonitor electrolytes

AnticonvulsantsDiazepam 5mg iv

Antihypertensivesphentolamine ( pheochromocytoma), Nifedipine

Storage & how to use Room temperature Dark place Don`t freeze Once opened use within 4 hours Don`t mix with other drugs Don`t prick rubber lid at the same place

repeatedly

Storage & how to use Dose :Max Ionics : 2-3ml/ kgNonionics: 5ml/ kgDose= 5ml/kg

Sr Creat Don`t remove IV line as it may be

needed later Don`t leave the pt unattended for at

least half an hour

Some other facts Laboratory tests like urine protein, serum

electrolytes may be affected so do either prior or 24 hrs after procedure.

Some enzymes may become elevated. Breast feeding to be avoided for at least 5

days. Trans placental/ milk passage can cause

iodine mumps or hypothyroidism in child.

Thank you...

Dr Pankaj Dixit