Emergency physicians dispel common beliefs about contrast allergies, antibiotics in nasal packing, tap water as an irrigation solution, and herniation after lumbar puncture

1. Contrast Allergies: Stop the Crustacean Bashing

The short message is, “Iodine is not an allergen!”¹

There are many theories about what causes “allergic-like” reactions from contrast media. However, we can stop asking about shellfish and strawberry allergies as iodine content has nothing to do with these reactions. As a matter of fact, if we are worried about iodine, we’re asking the wrong questions. The iodine content of shrimp is 1,000 mcg/kg, but chicken contains a whopping 1,248 mcg/kg. Perhaps we should have been asking about chicken allergies instead of shellfish.

The fact is that those with seafood allergies are at the same low risk for contrast reactions as those with other food allergies and asthma. In addition, only 7 to 17 percent of those with prior contrast reactions are at a risk of recurrence.¹ That’s likely much less than most of us would have thought.

A much more plausible explanation for contrast reactions seems obvious when reviewing the evolution of intravenous contrast materials. Data collected from 1985 to 1999 reflected an adverse reaction rate of 6 to 8 percent with ionic (high-osmolar) contrast use, compared with 0.2 percent with exclusive nonionic (low-osmolar) contrast use.² It stands to reason that most patients reporting a contrast reaction in the distant past experienced a reaction due to ionic contrast.

2. Lack of Backing for Antibiotics and Nasal Packing

It’s socially unacceptable to pick your nose, and it’s medically unnecessary to use antibiotics when packing one.

Although it’s a small study, we probably don’t need large numbers to disprove something that never had proof to begin with.

Nasal packing for spontaneous epistaxis, most with Merocel and some with zinc paste and Foley catheters, was utilized. In this prospective observational series, 78 were treated with amoxicillin/clavulanate and 76 without antibiotics. All patients were observed for otitis media, sinusitis, toxic shock syndrome, and any other infectious complication.³

No patients in either group developed an infectious complication. Particularly with close follow-up, antibiotics appear to be unnecessary.

3. Wounds: The Magic Cleanser

Tap water—and lots of it—is likely the best irrigation solution. In this meta-analysis of 11 studies, tap water, distilled water, cooled boiled water, and normal saline were evaluated. The studies included wounds in pediatrics and adults. Here is the breakdown:

• open fractures: one trial
• surgical wounds: four trials
• chronic wounds: one trial
• lacerations: five trials

In the laceration trials, tap water was compared to saline, and the relative risk of infection was 0.63.4 Thus, if tap water was utilized, infection was less likely than with saline irrigation.

With respect to irrigation additives, such as Betadine, the available data show that 1% solutions probably don’t impede wound healing in lacerations but certainly don’t reduce infections either. However, 10% (standard) Betadine is tissue toxic.^5-9

4. CT Before LP: Contrary to Popular Teaching, Heads Will Not Explode

This is an outdated concept without foundation to begin with. “Pathological arguments are made for supporting this practice, but no evidence exists to support these concerns.”¹⁰ First, herniation following lumbar puncture is very rare. The issue has never been about increased intracranial pressure; the issue is “brain shift” or “elevated CSF pressure.”¹¹ To drive this point home, just consider the number-one treatment for idiopathic intracranial hypertension (pseudotumor cerebri). Not only is it safe to LP these patients without risk of herniation, it’s recommended. If you still believe a CT is necessary prior to LP, Joffe further reported that in patients at risk for herniation, the CT is frequently normal, and a normal CT does not ensure the safety of LP.¹⁰

All of this hysteria began in 1969 when Dr. Duffy was managing 30 patients with end-stage brain tumors and decided to tap them all. One hundred percent herniated, 50 percent immediately and the rest within 12 hours. All of the patients had progressive headache, an altered mental status, and localizing neurological findings.¹² Even on a bad day, I don’t see any of us performing LPs on such patients.

A few other articles of interest on the topic:

1. Archer BD. Computed tomography before lumbar puncture in acute meningitis: a review of the risks and benefits. CMAJ. 1993;148(6):961-5.
   • No evidence supporting routine CT prior to LP for meningitis.
   • If atypical features (i.e., neuro findings) exist, CT may be indicated.
2. Hasbun R, Abrahams J, Jekel J, et al. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. N Engl J Med. 2001;345:1727-33.
   • 52 of 56 patients with abnormal CTs had uneventful LPs.
   • Performing CT first basically doubles the length of stay (LOS), approximately six versus three hours. If you need the CT (i.e., SAH evaluation), consider doing the LP first, and reduce the LOS by 50 percent.

Kevin M. Klauer, DO, EJD, FACEP, is director of the Center for Emergency Medical Education (CEME) and chief medical officer for Emergency Medicine Physicians, Ltd., Canton, Ohio; on the Board of Directors for Physicians Specialty Limited Risk Retention Group; assistant clinical professor at Michigan State University College of Osteopathic Medicine; and medical editor in chief of ACEP Now.

References

1. Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med. 2010;39(5):701-7.
2. Cochran ST, Bomyea K, Sayre JW. Trends in adverse events after IV administration of contrast media. Am J Roentgenol. 2001;176:6, 1385-1388.
3. Pepper C, Lo S, Toma A. Prospective study of the risk of not using prophylactic antibiotics in nasal packing for epistaxis. J Laryngol Otol. 2012;126(3):257.
4. Cooper D, Seupaul R. Is water effective for wound cleansing? Ann Emerg Med. 2012;60(5):626.
5. Goldenheim PD. An appraisal of povidone-iodine and wound healing. Postgrad Med J. 1993;69 Suppl 3:S97-105.
6. Roberts AH, Roberts FE, Hall RI, et al. A prospective trial of prophylactic povidone iodine in lacerations of the hand. J Hand Surg. 1985;10(B):370-374.
7. Rogers DM, Blovin GS, O’Leary JP. Povidone-iodine wound irrigation and wound sepsis. Surg Gynecol Obstet. 1983;157:426-430.
8. Cooper ML, Laxer JA, Hansbrough JF. The cytotoxic effects of commonly used topical antimicrobial agents on human fibroblasts and keratinocytes. J Trauma. 1991;31:775-784.
9. Rodeheaver G, Bellamy W, Kody M, et al. Bactericidal activity and toxicity of iodine-containing solutions in wounds. Arch Surg. 1982;117(2):181-186.
10. Joffe AR. Lumbar puncture and brain herniation in acute bacterial meningitis: a review. J Intensive Care Med. 2007;22(4):194-207.
11. van Crevel H, Hijdra A, de Gans J. Lumbar puncture and the risk of herniation: when should we first perform CT? J Neurol. 2002;249(2):129-37.
12. Duffy GP. Lumbar puncture in the presence of raised intracranial pressure. Br Med J. 1969;1:407-409.