Month: July 2023

Toss Up: A Little Bleeding, or A Lot of Platelets

Platelets are the good little minions of hemostasis. In their absence, invasive procedures develop additional risk, ranging from minimal to clinically important, and the mitigation strategy ranges from avoidance, the alternative procedural techniques, to prophylactic platelet transfusions. Platelets, like any blood product, are associated significant risks, not limited to acute lung injury, transfusion-related circulatory overload, allergic reactions, and more.

This prospective, randomized trial evaluated whether, in patients with thrombocytopenia, a platelet transfusion was necessary before central venous catheter placement. Enrolled patients included those undergoing in-hospital, ultrasound-guided CVC placement, primarily “regular” CVCs, placed into the internal jugular and subclavian veins. Patients randomized to transfusion received one unit of platelet concentrate roughly one hour prior to the procedure. The primary outcome was CVC-related bleeding, graded on a scale of 0 to 4, where Grade 3 and 4 bleeding was associated with significant intervention.

In those receiving a platelet transfusion prior to CVC placement, grade 3 and 4 bleeding was seen in 4 of 188 (2.1%) of patients, compared with 9 of 185 (4.9%) of those who did not receive a transfusion. There were also excesses of Grade 1 and 2 bleeding in those who did not receive a transfusion prior to the procedure. Secondary subgroup analyses were underpowered to determine if any specific subgroups were at higher risk, but it is reasonable to suggest the risk may increase as the initial platelet count decreases, while internal jugular placement was the safest site.

The cost of this initial protection was, obviously, quite a number of platelet transfusions. Owing to observed bleeding complications, the mean number of units of platelets transfused following CVC placement was much higher in the group not having received a prophylactic transfusion. However, when the initial prophylaxis is taken into account, the transfusion cohort received more than double the platelets within 24 hours of the procedure. Red blood cell transfusion was not different between groups, and other observed length-of-stay and mortality outcomes are probably not reliably different.

The trial is presented as “negative”, as the differences in serious bleeding fail to meet the pre-specified endpoint for non-inferiority. The authors, however, make an appropriately nuanced interpretation regarding the sliding scale of risk for bleeding, and suggest lower platelet counts, and those likely to require a platelet transfusion in the near future for other clinical indications, represent the most judicious population in which to consider prophylactic transfusion.

“Platelet Transfusion before CVC Placement in Patients with Thrombocytopenia”

https://www.nejm.org/doi/full/10.1056/NEJMoa2214322

When ChatGPT Writes a Research Paper

It is safe to say the honeymoon phase of large language models has started to fade a bit. Yes, they can absolutely pass a medical licensing examination when given carefully constructed prompts. The focus now turns to practical applications – like, in this example, using ChatGPT to write an entire scientific paper for you!

There is no reason to go through the details of the paper, the content, the findings, or any aspect of fruit and vegetable consumption. It is linked only to prove that it exists, and was written in its entirety by an LLM. To create the article, the authors used prompts containing the actual data set, prompts for an introduction, summary tables, and a discussion – impressively, as part of an automated prompting engine written by the authors, not just a laborious manual process. The initial output was not, as you might expect, entirely appropriate, requiring substantial re-prompting and revision – but, in the end, as you may see, the output resembles a paper basically indistinguishable from an undergraduate or graduate student-level output.

There were, of course, hallucinations, banal unfounded declarations, and the expected simply fabricated references. But, considering a year or two ago, no one would have ever talked about or suggested a LLM could write any semblance of a robust research paper, this is still fairly amazing. Considering this sort of writing is close to peak intellectual accomplishment, it’s fair to say similar automated techniques may replace a great deal of lesser content generation.

“The Impact of Fruit and Vegetable Consumption and Physical Activity on Diabetes Risk among Adults”
https://www.nature.com/articles/d41586-023-02218-z

Anchoring on Bias

The results of this paper are hardly surprising, since the witnessed phenomenon – “anchoring bias” – exists as defined. However, it’s always fun to see it demonstrated objectively.

In this little piece of research, authors collated four years of encounters to Veterans Affairs emergency departments in the U.S. and parsed out the triage reason between “congestive heart failure” versus all others. These two groups were then compared regarding the rates of objective testing for pulmonary embolism, frequency of ordering B-type natiuretic peptide, and both initial and 30-day diagnoses of pulmonary embolism.

As the title suggests, the authors identify differences in testing associated with the recorded reason for visit – with less frequent testing for PE, increased confirmatory testing for CHF, and fewer diagnoses of PE at the initial visit. However, the 30-day rate of diagnosis for PE was the same between the two groups – 1.2% in those initially presenting for reason of CHF, and 1.1% for all others.

The implication suggested by these authors is the subsequent similar frequency of PE at 30 days represent a delayed or missed initial diagnosis, with the culprit being an element of cueing from the patient triage reason or other elements of medical history. This is obviously not a study design with the ability to conclusively demonstrate such a causative effect; a prospective design randomizing patients with an initial “CHF” reasons for visit to an alternative such as “shortness of breath” would tease out this effect. That said, this likely still represents an undercurrent of anchoring bias.

“Evidence for Anchoring Bias During Physician Decision-Making”
https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/2806464

Fall Recap

It is the long, cold dark here in Christchurch – improved dramatically by leaving for the U.S. for four weeks!

Firstly, the blog may be making a bit of a comeback – the ugly demise of Twitter seems to necessitate a better method of knowledge translation, such as blog posts that can be replicated across whichever platform is progressing towards dominance.

Next, of course, the Annals of Emergency Medicine Podcast continues apace. We’ve had two excellent co-hosts these past months whose background is far more diverse than ourselves, and we will be continuing to feature additional guests in coming months.

What have I been putting into ACEPNow?

Lastly, the Annals of Emergency Medicine Journal Club features important articles from outside the Emergency Medicine literature: