Anesthesiology
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Review
Presumed β-Lactam Allergy and Cross-reactivity in the Operating Theater: A Practical Approach.
- β-lactam allergy, particularly penicillin allergy is the most common perioperative patient-reported sensitivity, in up to 35% of patients.
- Unneccessary switching to non-β-lactams for surgical prophylaxis is not cost-free, and is contributing to the rise of c. difficile and vancomycin-resistant Enterococcus (VRE).
Patient history of penicillin allergy is of variable quality, and often does not allow the allergy to be ruled-out.
Step 1 – differentiate drug side effects from allergy. Isolated nausea, vomiting or diarrhoea are usually side effects.
Step 2 – identify the type of hypersensitivity.
- Most drug reactions are Type 4 (T-cell mediated), delayed from 2 hours to days after exposure. Mostly benign cutaneous symptoms (eg. rash) that do not necessarily require avoiding future β-lactam exposure, except in the case of Stevens-Johnson syndrome.
- Type 1 (IgE-mediated) hypersensitivities are immediate (minutes to 2 hours) but less common, causing urticaria, angioedema and/or anaphylaxis. Future exposure should be avoided.
- Type 2 (cytotoxic) and Type 3 (immune complex) are much less common, and present with more serious, though delayed, reactions (days to weeks).
Take home: Mild symptoms (eg. rash developing more than 2h after exposure) probably do not require β-lactam avoidance. If there is a history of moderate or severe reaction, then avoiding all β-lactams is wise.
Of interest: Although R1 side-chain similarity is the main contributor to penicillin-cephalosporin cross-reactivity, importantly, 1st generation cephazolin has a different R1 side-chain and has been reported to not cross-react. Other cephalosporins share side-chains with specific penicillins.
Finally, stop giving IV test doses. It makes no sense from a safety point of view and offers no useful information.
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Classical Article
Classic Papers Revisited: My Love Affair with the Venous System.
The Pathophysiology of Aortic Cross-clamping and Unclamping. By Gelman S. ANESTHESIOLOGY 1995; 82:1026-60. ⋯ Aortic cross-clamping is associated with the formation and release of many mediators which constitute a double-edged sword: they may mitigate or aggravate the harmful hemodynamic effects of AoX and unclamping. Injuries to the lungs, kidneys, spinal cord, or abdominal viscera are caused mainly by ischemia and reperfusion of organs distal to aortic cross-clamping. A clear understanding of the pathophysiologic mechanisms involved in these processes should help to promote rational, well-focused, and effective measures to prevent and treat homeostatic disturbances occurring during AoX and unclamping.