Tick killing in situ before removal to prevent allergic and anaphylactic reactions in humans: a cross-sectional study

The Australasian Society of Clinical Immunology and Allergy (ASCIA) recommends killing ticks in situ with an ether-containing spray and allowing them to drop off. The rationale is that this helps prevent allergy or anaphylaxis, since removal by other means might squeeze intra-abdominal contents and introduce more allergens.

One would think such a recommendation is based on high-quality evidence. It turns out this paper is probably the best evidence we have to inform practice. Oh great! Let’s have a look.

Just a word of warning, this ride is about to get bumpy.

Let’s start with the paper’s conclusion. It states, “[Our] results support killing ticks in situ before careful removal by mouthparts to reduce allergic/anaphylactic reactions…”

This wording suggests the researchers prospectively compared freezing with other methods of removal. But they didn’t. I am not joking.

The authors report their experience essentially using one method of tick removal and conclude it worked well. Once again, they did not properly compare it with anything else.

They do mention that anaphylaxis still occurred in some patients after ticks were frozen. Is it possible that the brief act of freezing a tick causes it to regurgitate more allergenic contents compared with careful removal using fine tipped forceps? The honest answer is that we simply do not know. There is clear clinical equipoise here and a proper comparative trial would be entirely ethical.

Unfortunately, there has now been a considerable amount of confidently expressed advice from ASCIA and others telling people that ticks must be killed before removal and that you should “freeze it and don’t squeeze it.” The certainty of these recommendations is not justified based on the evidence available.

One might ask, what is the harm in freezing before removal? Well, putting aside the possibility that we do not actually know whether freezing could worsen allergic reactions, the sprays themselves come with some cost. I checked my local pharmacy and they were about $25. The recommendation may also encourage people to present to busy emergency departments and wait hours before removal. Even worse, some people may become reluctant to remove ticks at all, despite prolonged attachment being associated with tick paralysis and tick-borne infections.

Oh, and not to be pedantic, but the title of the paper describes it as a cross-sectional study. It isn’t. It’s a prospective case series, or at best a prospective cohort study without a comparator group.

This is not a rant. It is simply pointing out the obvious. There is currently no good quality evidence supporting the recommendation to kill ticks in situ before removal. For all we know, it may even make things worse.

The emperor has no clothes!

 

Covering:

Taylor BWP, Ratchford A, Nunen S, et al. Tick killing in situ before removal to prevent allergic and anaphylactic reactions in humans: a cross-sectional study (although it’s not). Asia Pac Allergy. 2019;9(2):e15. [Link to full text of paper]

 

Evolution of secondary findings in acute cholecystitis: A temporal analysis from POCUS to subsequent imaging

Sonographic signs of cholecystitis tend to progress from the primary findings of cholelithiasis and a positive sonographic Murphy’s sign to the secondary findings of gallbladder wall changes, namely wall thickening and pericholecystic oedema. The presence of these secondary signs increases the specificity for diagnosing cholecystitis and surgeons often rely on them to guide admission and treatment decisions.

How quickly these changes develop has not really been established… until now.

These authors from the USA performed a dual site retrospective cohort study with good methodology. They included adult patients who underwent POCUS in the ED and later had a formal radiology ultrasound after admission.

The gold standard for diagnosing cholecystitis was primarily positive histology following cholecystectomy.

A total of 352 patients were included, with a 50% prevalence of cholecystitis.

Among the 252 patients without initial gallbladder wall changes on ED POCUS, around 20% developed wall changes on subsequent imaging, with a median time of 4 hours. Gallstones and a positive sonographic Murphy’s sign predicted the later development of wall changes.

The authors conclude that the evolution of cholecystitis is a dynamic process. This makes intuitive sense, as inflammatory conditions evolve over time, so there are no major surprises here.

There was another important finding. Acute cholecystitis can occur without gallbladder wall changes. In this study, most patients with cholecystitis did not have wall changes in the ED and never developed them prior to cholecystectomy. Importantly, these patients had positive histology following surgery, so this was unlikely to represent false positive diagnoses.

Interestingly, there was no mention of stones impacted in the gallbladder neck. This is the most common cause of cholecystitis. In my experience, it is also a fairly specific finding that strongly suggests developing cholecystitis.

So what is the take home message?

Yes, cholecystitis is a dynamic process. It takes time, with a median of 4 hours in this study, for gallbladder wall changes to appear on ultrasound if they are going to develop at all. This raises the possibility of repeat imaging in early presenters or in patients observed in a short stay unit when there is reasonable clinical suspicion for cholecystitis. 

Covering:

D. Ivanov, D. Cannata, K. A. Chin et al. Evolution of Secondary Findings in Acute Cholecystitis: A Temporal Analysis from Point of Care to Subsequent Imaging. J Emerg Med 2025;78:266-274. [link to article]

Duration of resuscitation interruption using point-of-care ultrasound versus traditional manual pulse check: A systematic review and meta-analysis

We know manual pulse checks during CPR are unreliable and often slow. “Do you feel a pulse…? I’m not sure… is that my pulse?”

So, is a POCUS pulse check faster and more accurate? Hmmm…

But first: what is a POCUS pulse check?

No, it’s not just looking at the heart during a rhythm check. It means using a linear probe to assess the carotid artery for compressibility and pulsatility, or using pulse-wave Doppler at the femoral artery to assess flow velocity.

So, is this actually better than our old-school manual checks?

The authors reviewed seven studies involving 496 participants. Overall, ultrasound was associated with a shorter pulse-check duration—by about 1.39 seconds.

Yes, that is not exactly a clinically earth-shattering difference.

(For what it’s worth, I’m a little skeptical of the overall data. Pulse checks in both groups were remarkably quick—around 3 to 10 seconds. This is quite different from earlier studies reporting much longer interruptions.)

But the more interesting difference is accuracy. Who cares how fast it is if it gets the answer wrong?

Three studies reported accuracy data. Manual pulse checks had a pooled sensitivity of 62% and specificity of 91%. POCUS pulse checks performed much better, at 99% and 96%, respectively.

Thoughts? Should we abandon manual pulse checks?

To be fair, major guideline groups (ILCOR, ACC/AHA, etc.) have recognised this problem and have been moving away from manual pulse checks for years. For lay rescuers, they now recommend looking for signs of life instead. Even so, health professionals are still checking pulses.

The authors do add some caution: the overall certainty of evidence is low. They also highlight the need for standard protocols, operator training, and high-quality prospective studies before practice changes too much.

For what it’s worth, I usually have a quick peek at the heart during rhythm and pulse checks. If it’s not moving, there's no point hunting for a pulse. (If you want to see this in action, check out Vijay’s paper in Emergency Medicine Australasia.)

Oh, and a strong word of caution: do not waste time checking for a pulse when a shockable rhythm is present!

If you want the best paper using a femoral artery catheter as the gold standard, look at Cohen’s study below. They used femoral pulse-wave Doppler to calculate peak systolic velocity and correlated it with blood pressure. It sounds complicated, but it's not. To me, this looks like the most promising technique.

What’s the takeaway?

POCUS pulse checks may catch on. Keep your eyes peeled and your finger on the pulse… or maybe not.

Covering:

Neto ES, Scapin M, Lazaro-Paulina F, et al. Duration of resuscitation interruption using point-of-care ultrasound versus traditional manual pulse check: A systematic review and meta-analysis. Amer J Emerg Med. 2025;98:145-152. [Link to article]

Cohen AL, Li T, Becker LB, et al. Femoral artery Doppler ultrasound is more accurate than manual palpation for pulse detection in cardiac arrest. Resuscitation. 2022;173:156-65. [Link to article]

Haematoma block is the most efficient technique for closed forearm fracture reduction: a retrospective cohort study

The answer to some research questions are so glaringly obvious that they really don’t need to be studied.

Anyone who has done a haematoma block for a wrist fracture knows that they are a lot quicker and less resource intensive than a Bier’s block or procedural sedation. This is the major advantage of choosing a haematoma block over the other techniques.

Nevertheless, these researchers from Australia put the answer in black and white with this retrospective cohort study. Looking at the metric of ED length of stay (LOS), they proved that haematoma block was faster in their two ED’s. The mean ED LOS was 187 minutes for haematoma block, 227 minutes for Bier’s, and 239 minutes for procedural sedation.

I suspect that other ED’s might have more impressive differences if they have trouble accessing crowded resuscitation rooms and qualified staff that are busy with other tasks.

On the flip side, procedural sedation had a higher rate of successful first attempt reduction at 94% vs. 76% for haematoma block. But groups were not randomised and reductions under procedural sedation were twice as likely to have senior staff present and an orthopaedic registrar.

They also mention the cost of consumables and opportunity cost were less with haematoma block. No surprise here.

More patients had complications with procedural sedation 18%, Bier’s 14% and 13% with haematoma block. All but one of the complications of haematoma block were due to “block failure.” I don’t believe this to be a complication but rather an expected outcome. Sometimes haematoma blocks simply don’t work and one needs to proceed to plan B. No big deal.

In their conclusion, the authors state haematoma block “should be the default anaesthetic technique” for closed reduction of closed forearm fracture reductions. Obviously, the choice is multifactorial and comes down to patient and local institutional factors. But generally speaking, I agree.

Covering:

Pitman GR, Soeyland T, Popovic G, Thomson D. Haematoma block is the most efficient technique for closed forearm fracture reduction: a retrospective cohort study. Emerg Med J. 2024 Sep 25;41(10):595-601. doi: 10.1136/emermed-2023-213591. PMID: 39019579. [link to article]

Predictive value of indirect ultrasound signs for low risk of acute appendicitis in paediatric patients without visualisation of the appendix on ultrasound

Have you ever ordered an ultrasound on a patient and had the report come back stating “appendix not visualised”? This seems to be a common and frustrating occurrence. We have historically considered this to be a result that doesn’t change our thought process, and we throw the report in the bin.

But what about the indirect signs of appendicitis that may be seen on ultrasound? If the appendix is inflamed, often so are the surrounding structures. Can the presence or absence of indirect signs change how we think about the post-test probability of disease?

Researchers from a single centre in beautiful Valladolid, Spain conducted a retrospective study of paediatric patients aged 3-13 who were thought possibly to have appendicitis and had a diagnostic workup.

There were 1,756 patient encounters. They used the Alvarado score to risk stratify the kids into low, intermediate or high risk. The positive appendicitis rate was ultimately found to be 18%.

A total of 60% of children had an ultrasound performed. About half the time the appendix was not visualised. In this cohort of patients, they went further to look at the ultrasound report for possible indirect signs of appendicitis.

Indirect ultrasound findings independently associated with appendicitis were a small amount of free fluid (OR 5), abundant free fluid (OR 30), and inflammation of the periappendiceal fat (OR 7).

The authors conclude that the absence of these indirect signs ruled out appendicitis in patients with low or intermediate suspicion with a sensitivity of 85% and a negative predictive value of 99% even when the appendix was not visualised. The missed cases tended to be patients that presented early after onset of pain as they likely had less inflammation present.

Some might argue that 85% sensitivity is not good enough. But appendicitis is not aortic dissection. I think a lower sensitivity is acceptable so that we are not causing harm by over investigation and admission.  A short delay to diagnosis of appendicitis is not likely to be harmful especially in early presenters that don’t have ultrasound signs of inflammation. Obviously, we must give good discharge instructions and return precautions for those that we send home.  

To be complete, there were a lot of limitations to this retrospective study. But there are other studies out there with similar results and conclusions.

Next time you get an ultrasound report of “appendix not visualised” make sure you read further. Indirect signs might be your friend.

Covering:

Pernía J, Cancho T, Segovia I, de Ponga P, Granda E, Velasco R. Predictive values of indirect ultrasound signs for low risk of acute appendicitis in paediatric patients without visualisation of the appendix on ultrasound. Emerg Med J. 2024 Jul 22;41(8):475-480. doi: 10.1136/emermed-2023-213466. PMID: 38729752. [link to article]

 

The Oakland Score to identify low risk patients with lower GI bleed that can be safely discharged

The Oakland score was derived in 2015 but it somehow slipped my attention. The score is quite simple and mostly includes at a combination of age, vital signs and hemoglobin level to risk stratify patients [Oakland score MdCalc link]. 

This new external validation study was a multicenter effort that was conducted in 140 US hospitals. It identified 38,067 patients admitted to the hospital with a primary diagnosis of lower GI bleed by ICD-10 codes. They retrospectively applied the Oakland score to these inpatients to see if this decision instrument could identify a group that was safe for discharge. Test characteristics of the score were reported at several cut-offs (8,9, and 10 points)

The primary outcome to determine “safe discharge” was a composite of an absence of the following: in hospital rebleeding, RBC transfusion, therapeutic colonoscopy, mesenteric embolization, laparotomy, in hospital death and readmission with subsequent lower GI bleeding 28 days.

Results?

Average age was 70 years old and 68% of patients received a blood transfusion. Yikes! These were not low risk patients… probably why they were admitted in the first place.

Applying the rule to this inpatient cohort identified a measly 8.7% of patients considered safe for discharge at the 8-point threshold with a sensitivity of 98.4% and 16% specificity. If the threshold score was increased to 10, identified 17.8% with similar sensitivity but increased specificity to 32%.

Overall, it’s a pretty bad decision instrument in this population as it is not discriminatory. It pretty much calls everyone positive. 

However, I think there is a bigger issue with this study.

It was conducted on inpatients. The decision to admit was already made!

For overall utility, it should have been done in the ED. Nevertheless, the authors did state, “a prospective cohort study is needed, in which all patients presenting to the emergency department are included, regardless of their admission status.”

For what it is worth, I might see myself documenting a low-risk Oakland score to support my decision to send home a low-risk patient with lower GI bleed home. But in its current form, I fear the lack of specificity may result in more patients being admitted to hospital if we apply it without thinking.

Ultimately, yes, I would really like to see this study prospectively validated in an ED population and compared to gestalt. Anyone interested in a research project?

Covering:

Oakland K, Kothiwale S, Forehand T, Jackson E, Bucknall C, Sey MSL, Singh S, Jairath V, Perlin J. External Validation of the Oakland Score to Assess Safe Hospital Discharge Among Adult Patients With Acute Lower Gastrointestinal Bleeding in the US. JAMA Netw Open. 2020 Jul 1;3(7):e209630. doi: 10.1001/jamanetworkopen.2020.9630. PMID: 32633766; PMCID: PMC7341175. [link to full text article]

 

 

 

 

 

Subarachnoid haemorrhage in the ED… pushing the boundary of negative CT out to 24 hours?

On non-contrast head CT, a SAH is usually found by identifying the presence of bright white blood in the subarachnoid space. But over time, the blood becomes isodense and becomes more difficult to find. As such, we are generally happy to exclude SAH if we have a negative non-contrast head CT performed within 6 hours of headache onset. But what about a longer time window… is a CT adequately sensitive to exclude SAH up to 24 hours?

These authors from the UK sought to answer this question by conducting a prospective multicentre cohort study of consecutive patients presenting to the ED with acute headache.

Investigation, diagnosis and management were conducted using their standard practice. All patients were followed up for 28 days to see if they missed any haemorrhages.

3663 patients were enrolled. About 90% got a CT and one third got a lumbar puncture after negative CT. Prevalence of SAH was 6.5% (n=237).

What were the results?

A CT withing 6 hours of headache onset was 97% sensitive with a negative predictive value of 99%. CT within 24 hours had a sensitivity of 94% and a post-test probability of disease of less than 1%. The authors believe this data will inform clinicians and patients about the need (or not) for further investigation after a negative CT.

Although I would very much like to believe these conclusions, there is one major concern with the methodology.

Incorporation bias.

The head CT, the test that they are trying to determine was good or not, formed a crucial part of the gold standard. An alternative title to the paper could have been, “We did a head CT to excluded SAH, it was negative, and we believed it.”

To be fair to the authors, it would be unfeasible and not ethical to have performed angiograms and lumbar punctures on all patients to exclude SAH. And their 28 day follow up was probably a reasonable surrogate to find missed SAH’s.

What should we conclude?

This study provides some evidence that we might be able to push the time window of CT a bit further. But I doubt the quality of this study will be enough to change guidelines. Unfortunately, there still is no right answer, and we will continue to engage in shared decision-making discussions with our patients.

 

Covering:

Trainee Emergency Research Network (TERN). Subarachnoid haemorrhage in the emergency department (SHED): a prospective, observational, multicentre cohort study. Emerg Med J. 2024 Oct 4:emermed-2024-214068. doi: 10.1136/emermed-2024-214068. [Link to article]