Anesthesiology
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Randomized Controlled Trial
Caffeine Accelerates Emergence from Isoflurane Anesthesia in Humans: A Randomized, Double-blind, Crossover Study.
What did they do?
Using a randmoized, double-blind crossover study, Fong et al anaesthetized eight male volunteers twice with 1.2% isoflurane for 1 hour, after propofol induction. In the final 10 minutes subjects were randomized to IV caffeine or placebo. No opioids were administered.
Receiving IV caffeine hastened emergence by over 40%, as measured by BIS and psychomotor testing.
Return of gag reflex was used as the marker of emergence, although time to emergence was consistent with eye opening and BIS.
How much caffeine did they give?!?
15 mg/kg of caffeine citrate, equivalent to 7.5 mg/kg of base caffeine – the same caffeine as in two large cups of coffee for a 70 kg male.
Come on, surely this isn't that important?
Although the mean 7 min difference may not appear clinically significant, especially when using more modern volatiles, this study is a good proof of concept of how caffeine may be a useful clinical tool when faced with delayed emergence after anesthesia and for patients at greatest risk of persistent psychomotor depression post-anesthesia, such as the elderly.
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Randomized Controlled Trial
Individual Positive End-expiratory Pressure Settings Optimize Intraoperative Mechanical Ventilation and Reduce Postoperative Atelectasis.
Optimal intraoperative PEEP varies among patients. Individualizing PEEP reduces post-operative atelectasis.
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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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This article reviews advancements in the genetics of malignant hyperthermia, new technologies and approaches for its diagnosis, and the existing limitations of genetic testing for malignant hyperthermia. It also reviews the various RYR1-related disorders and phenotypes, such as myopathies, exertional rhabdomyolysis, and bleeding disorders, and examines the connection between these disorders and malignant hyperthermia.
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Comparative Study
Comparison of an Updated Risk Stratification Index to Hierarchical Condition Categories.
The Risk Stratification Index and the Hierarchical Condition Categories model baseline risk using comorbidities and procedures. The Hierarchical Condition categories are rederived yearly, whereas the Risk Stratification Index has not been rederived since 2010. The two models have yet to be directly compared. The authors thus rederived the Risk Stratification Index using recent data and compared their results to contemporaneous Hierarchical Condition Categories. ⋯ Risk Stratification discrimination and minimum-variance predictions make it superior to Hierarchical Condition Categories. The Risk Stratification Index provides a solid basis for care-quality metrics and for provider comparisons.