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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Comparative Study
Cost-benefit Analysis of Maintaining a Fully Stocked Malignant Hyperthermia Cart versus an Initial Dantrolene Treatment Dose for Maternity Units.
WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: The Malignant Hyperthermia Association of the United States recommends that dantrolene be available for administration within 10 min. One approach to dantrolene availability is a malignant hyperthermia cart, stocked with dantrolene, other drugs, and supplies. However, this may not be of cost benefit for maternity units, where triggering agents are rarely used. ⋯ It is not of cost benefit to maintain a fully stocked malignant hyperthermia cart with a full supply of dantrolene within 10 min of maternity units. We recommend that hospitals institute alternative strategies (e.g., maintain a small supply of dantrolene on the maternity unit for starting treatment).
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WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: The pharmacokinetics of infused drugs have been modeled without regard for recirculatory or mixing kinetics. We used a unique ketamine dataset with simultaneous arterial and venous blood sampling, during and after separate S(+) and R(-) ketamine infusions, to develop a simplified recirculatory model of arterial and venous plasma drug concentrations. ⋯ Arterial drug concentrations measured during drug infusion have two kinetically distinct components: partially or lung-mixed drug and fully mixed-recirculated drug. Front-end kinetics suggest the partially mixed concentration is proportional to the ratio of infusion rate and total pharmacokinetic flow. This simplified modeling approach could lead to more generalizable models for target-controlled infusions and improved methods for analyzing pharmacokinetic-pharmacodynamic data.
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WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Xenon is an elemental anesthetic with nine stable isotopes. Nuclear spin is a quantum property which may differ among isotopes. Xenon 131 (Xe) has nuclear spin of 3/2, xenon 129 (Xe) a nuclear spin of 1/2, and the other seven isotopes have no nuclear spin. This study was aimed to explore the effect of nuclear spin on xenon anesthetic potency. ⋯ Xenon isotopes with nuclear spin are less potent than those without, and polarizability cannot account for the difference. The lower anesthetic potency of Xe may be the result of it participating in conscious processing and therefore partially antagonizing its own anesthetic potency. Nuclear spin is a quantum property, and our results are consistent with theories that implicate quantum mechanisms in consciousness.