Download Question #35 - Shellfish allergy patient prep

Question of the Week #35
Preoperative assessment
You are interviewing your patient, Ms. C., who is scheduled for a laparoscopic cholecystectomy with
possible cholangiogram. When you ask her about any allergies to foods or drugs, Ms. C. tells you that
she cannot eat shrimp because she is “deathly allergic to them.” What implications does this
information have on your development of a plan of care for Ms. C?
Response:
Any history of an allergic or adverse response to a drug or food should be taken seriously, especially
since many of the signs and symptoms of an allergic response (e.g. itching, difficulty breathing) can be
masked during a general anesthetic. The American College of Radiology (2010) recommends that “any
patient who describes an ‘allergy’ to a food or contrast media should be questioned further to clarify the
type and severity of the ‘allergy’ or reaction, as these patients could be atopic (allergy-prone) and at
increased risk for reactions.” Patients considered to be at risk include those with a previous reaction to
contrast media and patients with asthma, thyroid diseases, renal failure, and those on certain
medications, including metformin, Beta-blockers, interleukin, and NSAIDS (Messenger, 2009; Morcos et
al, 2008; Schabelman & Witting, 2010).
A cross reactivity between a shellfish allergy and an allergy to products containing iodine can safely be
placed in the “sacred cow” category. This myth was propagated by studies done in the early to mid1970’s that linked an acute reaction to iodinated contrast media to patients with shellfish allergies, even
though the percentages associated with reactions to contrast media were equal to or greater in patients
with other types of food allergies or asthma (Schabelman & Witting, 2010).
Iodine is an essential mineral without which the body cannot survive. It is found in thyroid hormones
and amino acids (Wykoff et al, 2011). A true allergy to iodine does not exist and as such it cannot be
considered an allergan. People reacting to shellfish, contrast media or a skin preparation agent are
actually reacting to other components in these substances.
An allergic reaction to shellfish is in response to proteins in the fish called tropomysins. These proteins
do not contain iodine. Tropomysins are specific to shellfish, so people who are allergic to shellfish can
generally safely eat scaled fish, which do not contain tropomysins.
Povidine-iodine (PI), a popular skin preparation agent, is composed of polyvinylpyrrolidine (povidine)
and iodine. Anaphylaxis to PI is rate; of those reported, most involved a reaction to povidine; none
reported a positive reaction to iodine. Shellfish allergy does not equate to an iodine allergy and is not a
contraindication to topical PI (Wykoff et al, 2011). The chemical structure of povidine, with or without
iodine, is not similar to contrast media, and a direct cross-reactivity has not been demonstrated. A
reported allergy to contrast media is not a contraindication to use topical PI.
Reactions to contrast media containing iodine are not due to the iodine, but are thought to be caused by
the hyperosmolarity of the solution. This reaction is not attributed to IgE, even though the end result
(degranulation of mast cells and basophils with the resulting histamine response) mimics that of a true
IgE, Type I anaphylactic reaction (Schabelman & Witting, 2010). The older generation of contrast media
had a very high ionic content, but any hyperosmolar fluid, regardless of its content, is very irritating to
the body. Most hospitals now use low osmolarity or non-ionic contrast agents which are better
tolerated by the body, with a concurrent reduction in adverse reactions. Thomsen (2006) recommended
that a low osmolarity or non-ionic contrast media drug be used for high-risk patients.
A review of the literature found that many physicians are still holding on to the shellfish allergy/iodine
myth. A study done by Beaty et al (2008) of 113 physicians found that 65.3% of radiologists and 88.9%
of cardiologists replied “yes” to the question “Do you or someone on your behalf inquire about a history
of seafood or shellfish allergy prior to the administration of contrast media?” 34.7% of the radiologists
and 50% of the cardiologists answered “Yes” to the question, “Would you withhold radiocontrast media
administration, or recommend premedication with corticosteroids/antihistamines based on a history of
seafood or shellfish allergy?” Interestingly enough, Draganov and Forsmark (2008) included an allergy to
shellfish as a factor thought to be associated with increased risk for reaction to contrast media (p. 1100).
Almost as controversial is the prophylactic use of corticosteroids for premedicating high-risk patients.
Although it seems like a good idea, this practice has been shown to be of limited benefit during severe
events. Studies show that the greatest benefit for high-risk patients is in the administration of 40-60mg
of prednisone po begun 12-24 hours prior to the procedure, and repeated with diphenhydramine po the
day of surgery (Messenger & Casserly, 2009). Some investigators question the efficacy of this practice
(Draganov & Forsmark, 2008; Schabelman & Witting, 2010). Hubbard et al (2008) states that there is no
proof that prophylactic use of steroids at the time of injection of contrast media has any effect at all.
Continuing physician education will help prevent withholding a necessary diagnostic study or needless
prophylactic treatment.
In the case of our patient, Mrs. C., conducting a thorough pre-operative assessment should include
inquiring about a history of any allergies and the type of reactions encountered with each to determine
whether it was a true life-threatening anaphylaxis as opposed to other adverse reactions which may be
uncomfortable or annoying but are self-limiting. Allergic responses as well as other undesirable
reactions should be documented in the patient record and communicated to the appropriate care
givers. Mrs. C should be asked about all medications she is currently taking, including over-the-counter,
and she should be assessed for risk factors for contrast media reactions. The article by Morcos et al
(2008) contains a questionnaire for iodine-based contrast media administration. It is comforting to note
that an allergy to seafood is not on the list of risk factors.
Mrs. C. should be educated that her allergy to shellfish does not mean she is allergic to iodine and does
not change the risk of reaction to contrast media any more than any other allergy. Although a
cholangiogram does not involve intravascular injection of a contrast media, the drug may be absorbed
into the bloodstream from the common bile duct.
All patients receiving a contrast media drug should be monitored for 20 minutes after the administration
of the radiocontrast for adverse reactions. Resuscitative equipment and drugs should be readily
available. A severe reaction should be treated in the same way as a severe anaphylactic reaction.
Now might be a good time to review the treatment protocols at your facility for adverse
reactions/anaphylactic responses. Talk with your rapid response team or ED department about
recognizing early signs and symptoms of an allergic response, and consider partnering with them to
develop a mock drill related to an adverse response to a drug.
Resources and references:
American Academy of Allergy, Asthma, and Immunology. Peer-reviewed medical content in both English
and Spanish. Retrieved Oct. 24, 2011 from http://www.aaaai.org/home.aspx
American College of Radiology. (2010). Patient selection and preparation strategies. In Manual of
Contrast Media (Version 7). Retrieved Oct. 24, 2011 from
http://www.acr.org/SecondaryMainMenuCategories/quality_safety/contrast_manual/PatientSelection.
aspx
Beaty, A.D., Lieberman, P.L., & Slavin, R.G. (2008). Seafood allergy and radiocontrast media: Are
physicians propagating a myth? American Journal of Medicine, 121(2), 158.e1-158.e4.
Bickham, P., & Golembiewski, J. (2010). Contrast media in the operating room. Journal of PeriAnesthesia
Nursing, 25(2), 94-103.
Burlingame, B. (2006). Shellfish and iodine allergies. AORN Journal, 83(2), 480-481.
Draganov, P.V., & Forsmark, C.E. (2008). Prospective evaluation of adverse reactions to iodinecontaining contrast media after ERCP. Gastrointestinal Endoscopy, 68(6), 1098-1101.
Food allergy and anaphylaxis network. Non-profit organization that provides resources and information
related to food allergies. Great resource for patients, as it is very consumer user-friendly. Retrieved Oct.
24, 2011 from http://www.foodallergy.org/
Hubbard, C.R., Blankenship, J.C., Scott, T.D., et al. (2008). Emergency pretreatment for contrast allergy
before direct percutaneous coronary intervention for ST-elevation myocardial infarction. American
Journal of Cardiology, 102(11), 1469-1472.
Mertes, P.M., Lambert, M., Gue´ant-Rodriguez, R.M., et al. (2009). Perioperative anaphylaxis.
Immunology and Allergy Clinics of North America, 29(3), 429-451.
Messenger, J.C. & Casserly, I.P. (2009). Advances in contrast media and contrast injectors. Cardiology
Clinics, 27(3), 407-414.
Morcos, S.K., Bellin, M.-F., Thomsen, H.S. et al. (2008). Reducing the risk of iodine-based and MRI
contrast media administration: Recommendation for a questionnaire at the time of booking. European
Journal of Radiology, 66(2), 225-229.
O’Malley, R.B., Cohan, R.H., Ellis, J.H., et al. (2011). A survey on the use of premedication prior to
iodinated and Gadolinium-based contrast material administration. Journal of the American College of
Radiology, 8(5), 345-354.
Schabelman, E., & Witting, M. (2010). The relationship of radiocontrast, iodine, and seafood allergies: A
medical myth exposed. The Journal of Emergency Medicine, 39(5), 701-707.
Thomsen, H.s. (2006). European Society of Urogenital Radiology (ESUR) guidelines on the safe use of
iodinated contrast media. European Journal of Radiology, 60(3), 307-313.
Velazquez, V., DIGiorgi Y., & Hernandez, Y. (2011). Misconceptions about shellfish allergies and iodine
radiocontrast media administration. Journal of Allergy and Clinical Immunology, 127(2), AB195.
Wykoff, C.C, Flynn, H.W., & Han, D.P. (2011). Allergy to povidine-iodine and cephalosporins: The clinical
dilemma in ophthalmic use. American Journal of Ophthalmology, 151(1), 4-6.