Severe bronchospasm or anaphylaxis?

In response to the recent anaphylaxis guidelines [1], we would like to report a case of severe bronchospasm misinterpreted as anaphylaxis. A young adult female presented for removal of a cervical spine tumour. Following induction of anaesthesia, she received vecuronium and ventilation by bag/mask was initially easy. After tracheal intubation, cefuroxime was administered and a throat pack inserted. A combination of bronchospasm and severe hypotension immediately ensued, and whilst no urticarial rash developed, a diagnosis of anaphylaxis was made. Cefuroxime was identified as the likely precipitant as it was administered immediately before the onset of symptoms. She received prompt anaphylaxis management per the Association of Anaesthetists of Great Britain and Ireland guidelines [1]. Bronchospasm, the predominant clinical feature, was so severe it necessitated disconnection of the breathing circuit and manual compression of the chest wall to facilitate exhalation. Following a positive response to treatment, a decision to proceed with surgery was made together with the neurosurgeons. Despite an increased risk of coagulopathy associated with anaphylaxis, the team felt that the need to preserve hand function, which was being compromised by the tumour, justified the fact that we proceeded to surgery. Surgery was uneventful. The patient's trachea was extubated successfully the following morning. Tryptase and complement levels were all normal; however, this doesn’t rule out anaphylaxis [1]. Skin prick testing for neuromuscular blockers cefuroxime, propofol, lidocaine, remifentanil and latex were performed, all of which were subsequently negative. With hindsight, we suggest that movement of the tracheal tube during insertion of the throat pack precipitated bronchospasm, and the high inflation pressures with auto-PEEP resulted in reduced venous return, hypotension and cardiovascular collapse, thus mimicking anaphylaxis. We conducted an internal survey of all anaesthetists in the Leeds General Infirmary asking them about the timing of administration of intravenous antibiotics in theatre and also to rank the anaphylactic risk of various neuromuscular blockers. One hundred responded (an 83% response rate). Although 25% of respondents believed antibiotics should be given more than 30 min before induction, only 15% administer them before and 5% give them with induction agents. Previously, the Association of Anaesthetists of Great Britain and Ireland has recommended that antibiotic administration should be separated from induction [2], thereby allowing the normal haemodynamic changes at induction of anaesthesia to resolve, yet over 70% of respondents administer antibiotics within 10 min of induction. Anaphylaxis under anaesthesia is rare, but in 60% of cases neuromuscular blocking drugs are the causative agents and in only 15% are antibiotics at fault [1]. Our assumption that cefuroxime rather than vecuronium was the precipitant was therefore likely to have been incorrect. Suxamethonium is the most likely of the neuromuscular blockers to cause anaphylaxis, followed by rocuronium [3]. Twenty-five percent of those surveyed failed to rank suxamethonium as the highest-risk agent and 40% thought rocuronium to be low-risk. Whether sugammadex will increase rocuronium’s use waits to be seen, but clearly anaesthetists underrate its allergic potential. Like the anaesthetists in the case above, most respondents regarded vecuronium as the safest neuromuscular blocking drug (38%) or ranked it 5th or lower, out of 7 agents (65%). This is not in accordance with the literature which gives vecuronium medium risk [3]. Even though cis-atracurium was regarded as the safest agent by 27% it is only used by 2% of respondents. This incident highlights how the deleterious effects of gas trapping during bronchospasm can masquerade as anaphylaxis. In addition, our survey suggests that anaesthetists are poorly informed regarding the anaphylactic potential of neuromuscular blocking drugs, and that the choice of the latter is not guided by concerns over anaphylactic risk. The administration of antibiotics, at induction, is at variance with both ideal practice and guidance.