Patient Encounter 1

A 44-year-old male is admitted to the hospital for treatment of a cellulitis. He states that he has no known allergies. He is prescribed IV nafcillin for his infection. During the first infusion, he notices that his ears are itching and he calls for a nurse. Upon the nurse's arrival, the patient appears nervous and is having difficulty breathing.

What type allergic reaction is the patient most likely having?

What is the first action this nurse should take?

Outline the medical treatment for this reaction and how fast should it be started?

The health care professional is faced with a difficult task when approaching a patient who claims a history of penicillin allergy. While as many as 12% of hospital patients state they have an allergy to penicillin, about 90% will have negative skins tests.10 Table 54-4 shows the traditional protocol for penicillin skin testing.11 This test only evaluates IgE-mediated reactions. A patient with a history of other serious reactions such as erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis should not receive penicillins and should not be tested.

^^ Penicillins and cephalosporins both have a f-lactam ring joined to an S-containing ring structure (penicillins: a thiazolidine ring, cephalosporins: a dihy-drothiazine ring). The extent of cross-allergenicity appears to be relatively low, with an estimate of around 4%.12 Cross-allergenicity is less likely with newer generation cephalosporins compared to the first generation agents. Anaphylactic reactions to cephalosporins are rare, with a predicted range of 0.0001% to 0.1%. Minor skin reactions including urticaria, exanthem, and pruritis are the most common allergic reac-

tions with cephalosporins, showing severe reactions less often than with penicillins. Table 54-4 Procedure for Performing Penicillin Skin Testing

Materials

Volume (in Drops)

Pre-Pen 6 x 1Gr' M

1

Penicillin G 10r000 units/mL

1

ยก^Lactam drug 3 mg/mL

1

0.03% albumin sa Ii ne t :ori t rol

1

Histamine control (1 mg/mU

1

Place a drop of each test material on the volar surface of the forearm

Prick the skin with a sharp needle inser i ed through the drop at a angle yenily tenting the skin in an upward motion Interpret skin responses after 15 minutes A wheal at least 2x2 mm with erythema is considered positive If the prick tost is nonreactive, proceed to the intradermal test if the histamine control is nonreactive, the test considered uninterruptible

B. Intradermal Skin Testing

Materials

Volume [rriL}

Pre-Pen 6 x icm

0.02

Penicillin G 10r000 Units/ml

0.02

/3-Lactam drug 3 mg/rnL

0.02

0.03% Albumin-saline control

0,02

Histamine control (0.1 mg/rnL)

0.02

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