Upon arrival in the ICU, the patient quickly stabilized hemodynamically. She was weaned from all inotropic support within 2 hours of arrival. The patient lost 800 mL of blood through wound VAC over the first 12 hours postoperatively and required a total of 11 units of pRBC, 6 units fresh frozen plasma, and 3 units of pooled cryoprecipitate, all of which were compatible. Laboratory values, including arterial pH, lactic acid, and coagulation studies, normalized on the evening of surgery, and, by the next morning, the patient was alert and was extubated without difficulty. Steroids were tapered without hemodynamic compromise while the patient was in the ICU. Cardiology examination revealed no abnormalities. Because of the temporal association of blood transfusion with cardiovascular collapse, pRBC units were retested for antibodies and cultured. Both of these investigations were negative. Wound cultures again were positive for Staphylococcus epidermidis, and blood cultures were negative. The patient was started on daptomycin based on susceptibility profiles. Serum histamine levels taken during initial resuscitation in the operating room were normal. The serum tryptase level obtained at the same time was markedly elevated at >700 ng/mL (normal, <11.5 ng/mL), although this information was not available until several days later.
The patient underwent 2 additional surgeries during the same admission, including the prosthesis removal and tobramycin cement spacer placement, without incident. She was discharged home, again without incident. The patient was later evaluated by an outside allergist and underwent skin puncture and intradermal allergy testing. The results were consistent with a strong IgE-mediated hypersensitivity. Interestingly, she was found not to have a penicillin allergy.
Discussion
Vancomycin hypersensitivity reactions include the anaphylactoid reaction red man syndrome and a true IgE-mediated anaphylactic reaction. Red man syndrome is much more common, with reported rates in infected patients from 3.7% to 47%,4,5 when vancomycin is given at the suggested rate of 1 g over 1 hour. The reaction occurs because of histamine release from mast cells and basophils, and does not require previous sensitization.3 The rate of infusion is directly related to the development of symptoms, with 100% of patients developing symptoms in 1 study with rapid infusion (1 g over 10 min).6 Red man syndrome can typically be prevented by slowing the rate of infusion or by giving an H1 blocker.3 Anaphylaxis is more rare but can occur.7 Anaphylaxis is mediated by vancomycin-specific IgE, which requires previous exposure, as was the case with our patient. Interestingly, the patient had received vancomycin many times without any signs of a hypersensitivity reaction. Antihistamines are not effective in treating anaphylaxis, and epinephrine is the first-line agent.3 This was clearly demonstrated in this case, as there was a significant hemodynamic response to epinephrine and a negligible response to other vasopressors, specifically norepinephrine and vasopressin.
Most hypersensitivity reactions during the course of a surgical procedure occur with induction of anesthesia, with neuromuscular blocking agents and antibiotics being the most common causes.8 In our case, antibiotics were held until after deep cultures were taken. Given the time from induction to the anaphylactic reaction, it is unlikely the reaction resulted from the induction agents or the neuromuscular blocking agent. The possibility of a transfusion reaction was also investigated, since a unit of pRBC was still being transfused when symptoms began. An acute hemolytic transfusion reaction has the classic triad of fever, flank pain, and hemoglobinuria, and can also present as DIC.9 Under anesthesia, DIC can often be the presenting sign. In this case, a hemolytic transfusion reaction appeared very unlikely. All of the blood components the patient received were rechecked and found to be compatible, posttransfusion analysis showed no evidence of hemolysis in any sample, and the direct antiglobulin test was negative in all components.
To our knowledge, there are no reported cases of vancomycin-induced anaphylaxis with concomitant DIC. Symptoms of anaphylaxis after exposure to a possible antigen include rapid onset of hypotension or rapid onset of signs in at least 2 organ systems, including cutaneous, gastrointestinal, respiratory, and cardiovascular.10 Anaphylaxis with DIC is rare after exposure to any substance but has been reported.11 In fact, induction of systemic anaphylaxis in mice is known to cause DIC, with platelet-activating factor suggested as an important common mediator. A similar mechanism is suspected in humans.12
Confirmation of, and, certainly, prediction of, a vancomycin hypersensitivity reaction is difficult. Histamine levels can be used as a measure of mast-cell degranulation, but serum levels peak within 5 minutes and quickly return to baseline, limiting its diagnostic usefulness.3 Tryptase is an enzyme found in the secretory granules of mast cells. It has become an accepted marker of acute anaphylaxis, and, in vancomycin hypersensitivity reactions, can also distinguish between anaphylactic and anaphylactoid reactions.13 Tryptase levels peak 1 to 2 hours after the reaction, making this easier to measure than histamine, but results may not be available for several days, making it useful only in retrospect, as in our case. Skin testing is probably the best way to confirm a hypersensitivity reaction, although even this has been questioned with vancomycin because some find a high false-positive rate3, while others think the false-negative rate is likely too high.7 In this case, we were able to confirm our initial clinical suspicion with both an elevated tryptase level and a positive skin test.