The Elephant in the PECARN/CHALICE/CATCH Room

A few months ago, I wrote about the main publication from this study group – a publication in The Lancet detailing a robust performance comparison between the major pediatric head injury decision instruments. Reading between the lines, as I mentioned then, it seemed as though the important unaddressed result was how well physician judgment performed – only 8.3% of the entire cohort underwent CT.

This, then, is the follow-up publication in Annals of Emergency Medicine focusing on the superiority of physician judgment. Just to recap, this study assessed 18,913 patients assessed to have had a mild head injury. Of these, 160 had a clinically important traumatic brain injury and 24 underwent neurosurgery. The diagnostic performance of these decision instruments is better detailed in the other article but, briefly, for ciTBI:

  • PECARN – ~99% sensitive, 52 to 59.1% specific
  • CHALICE – 92.5% sensitive, 78.6% specific
  • CATCH – 92.5% sensitive, 70.4% specific

These rules, given their specificity, would commit patients to CT scan rates of 20-30% in the case of CHALICE and CATCH, and then an observation or CT rate of ~40% for PECARN. But how did physician judgment perform?

  • Physicians – 98.8% sensitive, 92.4% specific

Which is to say, physicians missed two injuries – each detected a week later in follow-up for persistent headaches – but only performed CTs in 8.3% of the population. As I highlighted in this past month’s ACEPNow, clinical decision instruments are frequently placed on a pedestal based on their own performance characteristics in a vacuum, and rarely compared with clinician judgment – and, frequently, clinician judgment is as good or better. It’s fair to say these head injury decision instruments, depending on the prevalence of injury and the background level of advance imaging, may actually be of little value.

“Accuracy of Clinician Practice Compared With Three Head Injury Decision Rules in Children: A Prospective Cohort Study”

On Anesthesiology Knows Sedation

“These guidelines are intended for use by all providers who perform moderate procedural sedation and analgesia in any inpatient or outpatient setting …”

That is to say, effectively by fiat, if you perform procedural sedation, these guidelines apply to YOU.

This is a publication by the American Society of Anesthesiologists, and sponsored by various dental and radiology organizations. This replaces a 2012 version of this document – and it has changed for both better and worse.

Falling into the “better” column of this document, this guideline no longer perpetuates the myth of requiring a period of fasting prior to an urgent or emergent procedure. Their new recommendation:

“In urgent or emergent situations where complete gastric emptying is not possible, do not delay moderate procedural sedation based on fasting time alone”

However, some things are definitely “worse”. By far the largest problem with these guidelines – reflecting the exclusion of emergency medicine and critical care specialties from the writing or approving group – is their classification of propofol and ketamine as agents intended for general anesthesia. They specifically differentiate practice with these agents from the use of benzodiazepines or adjunctive opiates by stating:

“When moderate procedural sedation with sedative/ analgesic medications intended for general anesthesia by any route is intended, provide care consistent with that required for general anesthesia.”

These guidelines do not describe the care of patients receiving general anesthesia, but, obviously, we are not performing general anesthesia in the Emergency Department – and, I expect most hospitals do not credential their Emergency Physicians for general anesthesia. The impact of these guidelines in a practical sense on individual health system policy is unclear, particularly in the context of safe use of these medications by EPs for decades, but it’s certainly just one more pretentious obstacle to providing safe and effective care for our patients.

“Practice Guidelines for Moderate Procedural Sedation and Analgesia 2018”

“The Newest Threat to Emergency Department Procedural Sedation”

Using PERC & Sending Home Pulmonary Emboli For Fun and Profit

The Pulmonary Embolism Rule-Out Criteria have been both lauded and maligned, depending on which day the literature is perused. There are case reports of large emboli in patients who are PERC-negative, as well as reports of PE prevalence as high as 5% – in contrast to its derivation meeting the stated point of equipoise at <1.8%. So, the goal here is to be the prospective trial to end all trials and most accurately describe the impact of PERC on practice and outcomes.

This is a cluster-randomized trial across 14 Emergency Departments across France.  Centers were randomized to either a PERC-based work-up strategy for PE, or “conventional” in which virtually every patient considered for PE was tested using D-dimer. Interestingly, these 14 centers also crossed-over to the alternative algorithm approximately halfway through the study period, so every ED was exposed to both interventions – some of which used PERC first, and vice versa.

Overall, they recruited 1,916 patients across the two enrollment periods, and these authors focused on the 1,749 who received per-protocol testing and were not lost to follow-up. The primary outcome was any new diagnosis of venous thromboembolism at 3 month follow-up.  This was their measure of, essentially, clinically important missed VTE upon exiting their algorithm. The headline results here were, in their per-protocol population, that 1 patient was diagnosed with VTE in follow-up in the PERC group compared with none in the control cohort. This met their criteria for non-inferiority, and, just at face value, the PERC-based strategy is clearly reasonable. There were 48 patients lost to follow-up, however, but given the overall prevalence of PE in this population, it is unlikely these lost patients would have affected the overall results.

There are a few interesting bits to work through from the characteristics of the study cohort. The vast majority of patients considered for the diagnosis of PE were “low risk” by either Wells or simplified Revised Geneva Score. However, 91% of those in the PERC cohorts were “low risk”, as compared to 78% in the control cohort – which, considering the structure of this trial, seems unlikely to have occurred by chance alone. In the PERC cohort, about half failed to meet PERC and these patients – plus a few protocol violations – moved forward with D-dimer testing. In the conventional cohort, 99% were tested with D-dimer in accordance with their algorithm.

There were then, again, more odd descriptive results at this point.  The results of the D-dimer testing (≥0.5 µg/mL) were positive in 343 of the PERC cohort and 471 of the controls. However, physicians only moved forward with CTPA in 38% of the PERC cohort and 46% of the conventional cohort.  It is left entirely unaddressed why patients entered a PE rule-out pathway and ultimately never received a definitive imaging test after a D-dimer above threshold. For what it’s worth, then, the fewer patients undergoing evaluation for PE in the PERC cohort led to fewer diagnoses of PE, fewer downstream hospital admissions and anticoagulants, and their ED length of stay was shorter. The absolute numbers are small, but patients in the control cohort undergoing CTPA were more likely to have subsegmental PEs (5 vs. 1), which, again, ought to generally make sense.

So, finally, what is the takeaway here? Should you use a PERC-based strategy? As usual, the answer is: it depends. Firstly, it is almost certainly the case the PERC-based algorithm is safe to use. Then, if your current approach is to carpet bomb everyone with D-dimer and act upon it, yes, you may see dramatic improvements in ED processes and resource utilization. However, as we see here, the prevalence of PE is so low, strict adherence to a PERC-based algorithm is still too clinically conservative. Many elevated D-dimers did not undergo CTPA in this study – and, with three month follow-up, they obviously did fine. Frankly, given the shifting gestalt relating to the work-up of PE, the best cut-off is probably not PERC, but simply stopping the work-up of most patients not intermediate- or high-risk.

“Effect of the Pulmonary Embolism Rule-Out Criteria on Subsequent Thromboembolic Events Among Low-Risk Emergency Department Patients: The PROPER Randomized Clinical Trial”