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Benzene ring with carbon atoms numbered clockwise as positions 1-6

Dissociates into an anion (benzene ring) and cation (sodium)

Position 1:  COOH (acid group) that makes benzoic acid and allows for the formation of salts/amides, influences water solubility. Has a NEGATIVE charge
Positions 2, 4, and 6: each contain one iodine atom  (3 total iodine atoms per molecule)
Positions 3 and 5: each contain a side group that determine HOCM class, lower toxicity & fat solubility, and increase solubility & excretion by kidneys

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Ionic contrast media molecules tend to be smaller

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Can be either a monomer (1 benzene ring with 3 iodine atoms) or a dimer (2 benzene rings with 6 total iodine atoms)

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Ionic monomers, HOCM have higher osmolality than  blood ) plasma (up to 5-8x) (1800-2100 mOsm/kg of water)

Can also come in the form of LOCM (ionic dimers) that have about 2x as much osmolality as blood (600-850 mOsm/kg of water)

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3:2
(3 iodine atoms : 2 particles for osmolality)

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Side groups help increase the solubility (hydrophilic) and
reduce fat solubility

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CM containing meglumine salts are more viscous and less toxic due to lower iodine content

CM containing sodium salts are less viscous but more toxic

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Miscibility is the ability of the agent to mix with body fluids

Ionic CM is highly miscible with the blood, but tends to pull water into the blood because its osmotic pressure is higher than in the surrounding tissues

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Less persistence

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The osmotic effect caused by the dissociation in the blood means ionic CM is more likely to cause an adverse reaction
Can have hypertonic and chemotoxic side effects

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These molecules do not dissociate into an anion and cation when introduced into the bloodstream

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Nonionic contrast media molecules tend to be large

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Can either be a monomer or a dimer

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Considered LOCM (300-484 mOsm/kg of water)

Monomers have about 2-3x more osmolality than blood

Dimers have about the same level of osmolality that blood does

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3:1
(3 iodine atoms : 1 osmotically active particle)

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nonionic CM is more soluble in water (hydrophilic) with low fat solubility

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viscous, must be warmed to body temperature before injection to decrease viscosity

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Less miscibility

Nonionic CM is more water soluble in blood plasma, making it less toxic at the cellular level

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More persistence

Nonionic CM is less toxic to the body and can remain in the body for longer periods of time without causing serious damage

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Because these molecules don't dissociate in the blood, they have a lesser osmotic effect and are less likely to cause adverse reactions

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Has same benzene ring and iodine molecule placement as ionic parenteral contrast media
Can contain either meglumine or sodium salts

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BaSO4
Compound composed of 1 barium, 1 sulfur, and 4 oxygen atoms

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High osmolality

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Not soluble in water

forms suspension when mixed with water

stabilizing agents (sodium carbonate and sodium citrate) prevent flocculation when mixed with stomach acid

Not absorbed in the body

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Not absorbed through body membranes. Rather, it passes through the GI tract without interaction with other tissues

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Used during studies of the GI tract when no obstruction or perforation is suspected

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perforation of GI tract

Diverticulitis

Ulcerative Colitis

Toxic Megacolon

Chronic constipation

Pre-CT (too dense)

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aspiration --> pneumonia

leakage into vascular system

severe constipation

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Water-soluble

can be diluted with water for enemas or CT scans

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Can be absorbed through mucosa and excreted through the kidneys, however, most is passed through the GI tract and out the rectum

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Suspected bowel perforation

bowel obstruction

pre-operative procedure

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history of aspiration

esophagotracheal fistula

iodine allergies

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can cause diarrhea, systemic hypovolemia, dehydration, or electrolyte imbalance

If aspirated, osmotic effusion can cause pulmonary edema, pneumonitis, and even death

anaphylaxis (theoretical)

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Gases (air, oxygen, carbon dioxide, nitrous oxide)

gas-producing crystals or tablets

soda water

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SAFE to inject into synovial joints, can be used in the GI tract

UNSAFE to use in vessels because it will cause a gas embolus!

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SAFE to use in the GI tract, is rapidly absorbed by the body

UNSAFE to use in vessels because it will cause a gas embolus!

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SAFE to use in the GI tract and vessels, because it will not cause a gas embolus!

One of the best and most common gases used as contrast media

rapidly absorbed by the body

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SAFE to use in the GI tract and vessels, because it will not cause a gas embolus!

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UGI or esophagrams

Barium enemas

Enteroclysis

Double contrast arthrograms

Soft tissue neck studies

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High osmolality
causes significant osmotic action in the GI tract

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diarrhea

systemic hypovolemia

dehydration

electrolyte imbalance

aspiration

pulmonary edema, pneumonitis, death

causes copious osmotic effusion

contraindicated in esophagotracheal fistula or in patients with hx of aspiration

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UGI, Esophagram

adults --> not diluted

Peds --> 30-60 mL diluted with 1:1 water

Enemas

adults --> 1:4 water to gastro to make mixture approximately isotonic

peds --> 1:5 dilution

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Not metabolized
Ionic CM dissociates, but there is no further breakdown of molecules

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Not metabolized
Nonionic CM does not dissociate and there is no separation of molecules

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High Osmolality (1960 mOsm/kg water)

Water-soluble

Distribution into intracellular and extravascular spaces

no biotransformation

elimination half-life is 90 minutes

primarily excreted by the kidneys

80% is eliminated 3 hours after injection

98% of contrast is eliminated within 1 week

some evident of accumulation in brain tissue (heavy metal chelates)

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patients with renal disease or poor renal function
Nephrogenic systemic fibrosis (NSF)