Friday, August 3, 2012

Vancouver Chest Pain Rule in Tehran


Iran and Canada would be considered by most to be very different places.  However, from a cardiovascular standpoint, it seems they're not so disparate.

This is a prospective, validation study of the Vancouver Chest Pain Rule.  The Vancouver rule is one of many 2-hour accelerated rule-outs operating under the presumption that all disease can never be detected – sensitivity will never be 100%, but this assumes a context in which a discussion may be had with the patient about outpatient disposition.  Essentially, any patient under 40 years without a history of coronary artery disease and a normal EKG simply gets discharged.  Older than 40 and atypical chest pain is discharged either immediately after a CK-MB < 3.0 µg/L, or receives a 2-hour delta + repeat EKG if > 3.0 µg/L.  Essentially, the rule is designed only to ensure all unusual NSTEMIs are picked up.

In the initial study, the 30-day ACS rate for the discharged group was 1.2%.  In this Iranian study, the 30-day ACS rate of 292 very-low-risk patients is 1.3%.  Two of the four patients meeting criteria for discharge by CK-MB had positive troponins.  Considering CK-MB is nearly considered anachronistic now, most modern EDs would have not have discharged these patients based on troponin testing.  A third patient had EKG changes on the second EKG – which should fail the Vancouver rule, so I'm uncertain why it was included in their very-low-risk group.  Finally, the last patient had an entirely normal evaluation and a subsequent 70% lesion discovered on angiography a week later.  No mention of the hemodynamic significance/relation to ischemia of this lesion is noted.

A few hundred patients is hardly a definitive validation, but it's a nice demonstration that 50% of their cohort could have been discharged in two hours – and with the same 30-day event rate as the poor people being made to glow in the CCTA studies.

"Validation of the Vancouver Chest Pain Rule: A Prospective Cohort Study"

Wednesday, August 1, 2012

Tramadol: A Myth of Safety

For me, tramadol lands squarely in the gap between oral analgesics I might use for "no pain" – ibuprofen, acetaminophen – and analgesics I might use for "real pain" – hydrocodone derivatives.  The literature describing the analgesic properties of tramadol is bizarre, with multiple comparisons with placebo, nerve blocks, adjunctive epidural anesthesia, etc., and very few head-to-head comparisons to the sorts of medications we routinely use.  When there are comparative efficacy reports, they typically conclude that tramadol is effective...just as effective as the NSAIDs its being compared with.

The theory I've heard people use when considering use of tramadol is that it has a better safety profile than hydrocodone and is less dependence-forming.  These claims may be true, but I do not believe they are true to the extent that it is clinically relevant.  Tramadol still generates an opioid withdrawal syndrome and, as this article describes, overdose/abuse still results in apnea with need for ventilatory support.

Additionally, tramadol is a GABA antagonist, lowering seizure threshold.  Of the 525 patients overdosing primarily on tramadol retrospectively identified at this Iranian hospital, 19 experienced apnea and 242 (46.1%) experienced seizures.  This is retrospective and co-ingestants cannot be fully ruled out, but the propensity for seizure is far more surprising than the incidence of apnea.

Tramadol has a role in pain control prescribing, but, in my practice, that role is tiny.

"Tramadol-induced apnea"
http://www.ncbi.nlm.nih.gov/pubmed/22809771

Tuesday, July 31, 2012

The "Peripheral" IJ

Some patients just have no IV access – no superficial peripherals, no deep peripherals, no external jugular veins.  In a critical emergency, this is the perfect time for an intraosseous line.  But, what about the situation where IV access is simply necessary, but not urgent?  Placing a central line is the last thing we're interested in doing – draping, opening a costly central line kit, billing for an expensive procedure, exposing them to risks of over-the-wire techniques in the central circulation.

This technique, described formally here by folks from Highland Hospital, involves placing a standard, peripheral catheter into the internal jugular vein under ultrasound guidance.  While I think this is a fantastic idea – much faster and less expensive than a full multi-lumen central line set-up – I wouldn't characterize it as "risk-free", either.  The nine cases in this year-long review all demonstrated a lack of complications, but more data would help refine the procedural risks.


"The ultrasound-guided 'peripheral IJ': internal jugular vein catheterization using a standard intravenous catheter."

Monday, July 30, 2012

Excitement For/Failure of CCTA

The third of the big CT coronary angiography studies from the last year – and, yet again, this is positive for its primary endpoint.


However, that value of that endpoint is another matter – mean length of stay in the hospital.  For the CCTA cohort, that mean was 23.2 hours and the "standard evaluation" was 30.8 hours.  However, more illuminating – and further favoring CCTA – is that the median CCTA evaluation time was 8.6 hours compared with 26.7 hours in the "standard evaluation" group.  Just like in the previous studies, CCTA is faster, and, for some patients, much, much faster.


But, as you can probably gather from that mean/median discrepancy, a substantial cohort in the CCTA group went on to have some pretty extensive downstream testing and prolonged hospital stays.  This means, from a costs standpoint, the two strategies eventually even out.  No significant safety differences were detected between the two strategies.


Now that we've seen the full results of ROMICAT II, CT-STAT, and ACRIN-PA, we have a pretty good idea of what this test does.  If you must evaluate these low-risk chest pain patients with imaging of some sort, need to clear them out of your Emergency Department quickly, your cardiology team is excited to take on the false positives, and you're unconcerned about the downstream harms – then CCTA is the test for you.  If the potential harms, the poor specificity, and the non-functional nature of the test concerns you – then no one will fault you for dragging your feet.


The accompanying editorial gets it right - this is still a test looking for the correct application.  However, we don't just need a better test – we need a better consensus for whom we're simply not going to test.


"Coronary CT Angiography versus Standard Evaluation in Acute Chest Pain"