Zworth Reading

Are high doses of naloxone required for nitazene overdoses?LOE 1 (Rapid systematic review)

Emergency Medicine Journal

In patients with nitazene overdose, what naloxone dose is required for reversal compared to standard opioid overdoses?

Background: nitazenes are a class of synthetic opioids that have been implicated in a growing number of overdose deaths across Canada and North America over the last few years, often mixed into the illicit fentanyl supply. Across 5 included studies, naloxone doses of 0.4-4.4 mg achieved reversal. This range is consistent with standard dosing for other synthetic opioids and does not support the common narrative that nitazenes require dramatically higher naloxone doses.

Rapid review with only 5 eligible papers. The evidence base is thin because nitazenes are relatively new to the illicit supply and most exposures are un-attributed at the point of care. Included studies are heterogeneous (case reports, case series, observational data) with survivorship bias built in. Dose-response cannot be established. That said, the absence of any signal requiring heroic naloxone doses is reassuring and clinically useful. The key practical caveat: in the ED we almost never know the patient took nitazene specifically. We suspect opioid or fentanyl overdose and manage it as such with the understanding that supply is often contaminated. So this evidence largely reinforces existing practice rather than requiring us to change anything.

Bottom line: Reassuring rather than practice-changing. Continue to titrate naloxone to respiratory effort, as you would for any suspected opioid overdose. The fear that nitazenes require 10+ mg of naloxone up front is not supported by current evidence. Be prepared to redose, as with any synthetic opioid, but you do not need to escalate initial doses because you suspect a novel opioid.

Is there evidence that intranasal ketamine can provide adequate procedural sedation in paediatric patients?LOE 2-4 (BET review of RCT and observational data)

Emergency Medicine Journal (Best Evidence Topic report)

In children requiring ED procedural sedation, does intranasal ketamine provide adequate sedation compared to IV ketamine?

BET review of 8 pediatric studies (~150 patients across mostly laceration repair and burn management). Typical dosing 4-9 mg/kg IN, with the largest study reporting 88% procedural success. IV ketamine remained modestly more effective (largest comparison: 64% IN vs 86% IV success). No serious adverse events reported across the pooled studies; nausea/vomiting was the most common side effect. The reviewers recommend a starting dose of ~4 mg/kg IN.

The evidence is heterogeneous, mostly single-arm observational and small trials, with only one adequately-powered comparison to IV ketamine. Sample sizes are small and most studies lack a non-inferiority comparator. Reviewers appropriately acknowledge these limits. For clinical decision-making the signal is clear enough: IN ketamine works most of the time in cooperative pediatric patients, and the safety profile is reassuring at the doses used.

Bottom line: A good overview of a genuinely useful ED tool that we could probably use more often. IN ketamine has a slightly lower success rate than IV ketamine, but it's a real option worth considering for laceration repair, burn dressing changes, and other painful procedures in the severely needle-phobic child. Start at ~4 mg/kg IN, be honest with parents about the ~10-15% failure rate, and plan for IV rescue if needed.

Contrast Controversies: Contrast Media Reactions in Emergency MedicineKnowledge translation / clinical review

EMOttawa  ·  LOE 3-4 (observational data + synthesis of 2025 CAR/CSACI, ACR/AAAAI, and ESUR guidelines)

Timely review synthesizing the recently updated 2025 guidelines on contrast media hypersensitivity from three major bodies: the Canadian Association of Radiologists / Canadian Society of Allergy and Clinical Immunology (CAR/CSACI), the American College of Radiology / American Academy of Allergy, Asthma, and Immunology (ACR/AAAAI), and the European Society of Urogenital Radiology (ESUR). Key evidence points: true hypersensitivity reactions to contrast are very uncommon (large South Korean cohort of >11.7 million low-osmolar contrast administrations showed immediate HR rate of 0.38%, severe reactions in only 0.02%). The 2025 CAR/CSACI guideline now recommends AGAINST routine corticosteroid premedication for patients with a history of HR of any severity to low-osmolar contrast. Current evidence favours switching the contrast agent (when the culprit is known) over corticosteroid premedication. The post walks through a practical approach to the patient with a documented contrast reaction history.

Bottom line: Contrast reactions come up constantly in the ED and we need a clear evidence-based approach. This post is worth reading in full. Two big takeaways from the 2025 guidelines: (1) routine corticosteroid premedication is no longer recommended even for prior severe reactions (2) when the previous culprit agent is known, switching to a different low-osmolar contrast is more effective than premedication. Truly reassuring given how often 'contrast allergy' delays needed imaging in sick patients.

ACG Clinical Guideline: Colonic Diverticulitis

American College of Gastroenterology

• CT imaging is essential to confirm diagnosis, particularly at first presentation and in severe cases
• Routine antibiotics are NOT recommended for low-risk patients with acute uncomplicated diverticulitis
• Antibiotics ARE appropriate for: high-risk features, immunocompromise, frailty, or inability to ensure safe outpatient management
• Colonoscopy recommended after recovery for complicated diverticulitis; suggested for uncomplicated with alarm symptoms or overdue CRC screening

GRADE methodology used. The no-antibiotics recommendation for uncomplicated diverticulitis is based on multiple RCTs showing no benefit — this is strong evidence. Other recommendations are moderate to low quality.

Conflicts with existing guidance: Aligns with European guidelines but may conflict with local practice patterns where antibiotics remain routine for all diverticulitis.

Bottom line: This reinforces what the evidence has been saying for years: uncomplicated diverticulitis in low-risk patients does not need antibiotics. The challenge is defining 'low-risk' in the ED: immunocompetent, non-frail, reliable follow-up, no systemic toxicity. If you're uncertain, antibiotics remain appropriate. But the reflexive 'diverticulitis = cipro/flagyl' approach is no longer evidence-based.

Bat exposure and rabies — a fatal caseLOE 5 (Case report / clinical teaching)

CMAJ Practice Case  ·  Infectious Disease / Public Health

Case-based teaching on the recognition of bat exposure as a rabies risk and the imperative of timely post-exposure prophylaxis.

CMAJ case describing a pediatric patient who died of rabies after a bat exposure where the family did not initially seek medical attention and therefore post-exposure prophylaxis was not administered. This was the first case of locally acquired rabies in Ontario since 1967.

Very sad case, but also a very high-yield teaching piece. The learning points are practical and directly relevant to ED practice. Any direct physical contact with a bat is a potential rabies exposure. Bat bites can be tiny and undetected, and the presumption should be that if a bat has been in contact with a person, it is treated as an exposure. Once symptoms of rabies develop, it is essentially uniformly fatal, meaning the ED window for prophylaxis is the entire clinical opportunity. Standard PEP is rabies immunoglobulin + vaccine series.

Bottom line: Worth reading the whole article. Key ED takeaways: any physical contact with a bat is a potential rabies exposure and warrants PEP unless the bat can be tested and cleared. When it comes to bats, the threshold for calling public health and starting immunoglobulin + vaccine is very low.