Re: Unwarranted assumption

[Richard Terrass <ricter@wn.net>]

SFisher373@aol.com wrote:
> 
> Radiology departments have used iodinated contrast agents for years with a
> high(10%) chance of reaction. Now we try to use non ionic compounds which
> have a lower rate of reaction.


I feel the 10% incidence quoted for contrast reactions is somewhat
misleading in that it depends on what you are defining as a contrast
reaction. Contrast reactions can range from something as mild as a brief
wave of nausea or something akin to hot flashes to anaphylactic shock.
The vast majority of reactions are mild and do not require medical
treatment. 

The non-ionic (or more correctly low osmolar) contrast agents still
contain Iodine. A quick look at the contents of a bottle of Omnipaque
shows approximately 300mg/mL organicly bound iodine. 

Contrast reactions due to a true allergy to iodine are felt by many to
be extremely rare. I believe that risk factors such as a prior history
of moderate or severe contrast reactions, asthma, multiple allergies,
and/or impaired renal function are probably much more accurate
predictors of the likelihood of contrast reactions than a shellfish
allergy which may not be due to the iodine content of the shellfish. The
fact that the low osmolar agents have a lower incidence of minor and
moderate reactions tends to support the thought that factors other than
iodine content are responsible for most contrast reactions including
osmolarity, sodium content, injection rate, and even patient
expectations.

-- 

Richard Terrass, M.Ed., R.T.(R) 
Massachusetts General Hospital Dept. of Radiology, 
Wang ACC 515, 15 Parkman St, Boston, MA 02114 
Office:(617) 726-7726  Fax:(617) 726-5282  Home:(617) 783-4771         

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