Friday, August 24, 2012

Head to Head With Head CT Rules

The "headline" you'll see from this article is that the Canadian Head CT Rule outperforms the New Orleans Criteria for radiographic imaging in minor head trauma.  Specifically, it outperforms it in this prospective, observational cohort from several hospitals in Tunisia, consecutive patients with blunt trauma to the head and at least one symptom secondary to the head trauma.

The most striking thing about this article, however, remains the gruesome number of false positives generated by each of these head CT decision rules.  While, obviously, the intent is to capture all the cases requiring neurosurgical intervention, the New Orleans Criteria could not rule out potential need for neurosurgical intervention in 1,180 out of 1,582.  When the theoretical purpose of these rules is to prevent "scanning everyone", we're not getting much bang for our buck.  The Canadian Head CT Rule was better – but still indicated a need for scan in 656 out of 1,582.

While the article focuses mostly on the need for neurosurgical intervention in GCS 15 patients, it's interesting to see their "secondary outcomes" which did not need "intervention".  Only 34 total patients in their cohort required intervention – while they found 133 skull fractures, 41 subdurals, 45 epidurals, 69 subarachnoids/hemorrhagic contusions, and 1 case of pneumocephalus.  The Canadian rule would have missed 11 of the 218 "clinically significant" findings, for a sensitivity of 95%.  The article does not specific precisely which types of findings were missed, but, clearly, many of those may be argued to be not significant.  Unfortunately, deriving a better rule based on a more liberal definition of "clinical significance" is likely to result in more missed interventions – but it's still probably worth trying.

"Prediction Value of the Canadian CT Head Rule and the New Orleans Criteria for Positive Head CT Scan and Acute Neurosurgical Procedures in Minor Head Trauma: A Multicenter External Validation Study"
http://www.ncbi.nlm.nih.gov/pubmed/22251188

Wednesday, August 22, 2012

How Fast Can We Rule-Out AMI?

Six hours?  Two hours?  One hour?  McDonalds' drive-thru?

This is the paper from Archives of Internal Medicine that's been making the rounds in the lay press regarding how quickly the ER should be able to detect your AMI with the new highly-sensitive troponins.  This is the APACE, prospective, international, multi-center study evaluating patients with "symptoms suggestive of acute myocardial infarction" and onset within the last 12 hours.

In this cohort, 1247 patients were recruited – and >300 were excluded for either going straight to the cath lab or having "another procedure performed" at the 1-hour time mark – and received hs-cTnT at index, 1, 2, 3, and 6 hours after presentation.  Myocardial necrosis was defined as a hs-cTnT >99th percentile, which for this assay is 14 ng/L, and a diagnosis of acute MI was made by two independent cardiologists upon review of records and lab results.

The authors split their cohort into two groups, a derivation cohort and a validation cohort, and did some statistical wrangling to come up with two cut-off strategies – one for rule-in and one for rule-out.  They were able to make diagnostic decisions on ~76% of their cohort at the one-hour time point, and 52 ng/L at presentation or an increase within an hour of 5 ng/L or more was ~94% specific for AMI.  Likewise, 12 ng/L and an increase less than 3 ng/L at 1 hour was ~100% sensitive for AMI.  The remaining 25% of their cohort was in a non-diagnostic zone.  At 30 days, there was one death in their rule-out cohort, for a 99.8% survival rate.

So, can you use this strategy?  If you feel as though this study is externally valid to your populations and you're using the same Roche Diagnostics test, you certainly may.  Every piece of data is something you can incorporate to your discussions with a patient regarding diagnostic certainty and risk.  Even an extra hour occupying an ED bed rather than moving out to a chest pain observation facility can significantly impede ED flow, while observation admissions are costly and inconvenient to patients.  The ideal strategy will depend on the capabilities of individual departments.

This study, along with the primary author, are sponsored in part by Abbott, Roche, and Siemens.
www.ncbi.nlm.nih.gov/pubmed/22892889

Monday, August 20, 2012

Intensive Blood Pressure Control in ICH

Not much works to treat ICH – and this retrospective analysis of INTERACT1 tries to coordinate a couple leaps to pull a different spin out of old data.  Unfortunately, it's still a re-analysis of essentially a negative trial, and that limits its utility for the purists.

INTERACT1 randomized patients with ICH to either "intensive" blood pressure lowering or conventional treatment – most of whom received some BP control – and noted significant improvements in hematoma volume.  However, the 90-day safety/clinical outcomes data did not show any difference in mortality or dependency.  This publication reverses the strategy, taking a look at the associations between good clinical outcomes and hematoma volume – and finds that increases in hematoma volume at 24 hours clearly predict poor clinical outcomes.

So, if intensive BP control reduces hematoma expansion and reduced hematoma expansion improves clinical outcomes, then why was INTERACT1 negative?  I suspect we'll find out more when INTERACT2 is published....

"Hematoma growth and outcomes in intracerebral hemorrhage: The INTERACT1 study"

Sunday, August 19, 2012

"Propoven"

Medication shortages are affecting many hospitals – we're low/out of prochlorperazine, injectable metaclopromide, etomidate, propofol, brevital – and one of the replacements we've recently been introduced to is "Propoven", a European manufacture of propofol.

It has only minor differences from propofol, but it should be noted it requires strict sterile technique when handling and has more medium-chain fatty acids.  An informational letter from Kabi describing a few of the differences is here:

AHRQ Infection Control @ ACEP

Jeremiah Schuur, featured on EM Lit of Note for his timely critique of the inadequacy of the "quality" measure for non-contrast head CT, passes along a notification of a pre-ACEP conference in ED infection control practices.


Sponsored by AHRQ, ACEP, and infection control societies, find more information about the conference here:

http://edip.partners.org/conference/