Friday, December 28, 2012

Breast Cancer From Pediatric Trauma Imaging

Evaluations for significant pediatric blunt trauma tend to be rather rare.  However, one flip side to improved vehicular safety is that previously fatal accidents turn into diagnostic dilemmas with otherwise well-appearing children after horrific potential injury mechanisms.

This specific article tries to address the risk/benefit ratio for imaging the pediatric thoracic spine after trauma, with a focus on the lifetime excess attributable risk for breast cancer.  They used estimates of radiation to breast tissue from plain films and CT, and then applied the predictions from the BEIR VII report to determine EAR.  From all these various calculations, their worst-case scenario derived an excess of 79.6 cases of breast cancer per 10,000 CT scans in females aged less than 12 years.

Unfortunately, the proponents of CT imaging cite these studies and say we've done nothing but document theoretical risk (based on atomic bomb exposure) – while ignoring that the risk of missed injury is equally theoretical.  As usual, the prudent course of action is to perform additional testing only when explicitly indicated – the additional cases of breast cancer are not trivial, but neither are missed injuries.  The rate of additional breast cancer cases is certainly not so high that CTs should be skipped when clinically indicated.

"Theoretical Breast Cancer Induction Risk From Thoracic Spine CT in Female Pediatric Trauma Patients"
www.ncbi.nlm.nih.gov/pubmed/23184109

Wednesday, December 26, 2012

Predicting Immediate Improvement After tPA

tPA for stroke remains controversial, to say the least.  The reasons behind the Emergency Medicine/Neurology disconnect are complex and covered elsewhere.  Regardless, thrombolysis is here to stay – and probably helps some patients.  The hard part is finding those patients with the most favorable risk/benefit ratio.

This is a study that looked at diffusion-weighted imaging to try and predict which patients were most likely to rapidly improve with tPA.  These authors enrolled sixty-six patients with acute stroke eligible for tPA under the Japanese license and performed diffusion-weighted MRI on each of them.  Previous studies had suggested an ASPECTS score > 7 predicted response to tPA – and this study confirmed it.  Essentially, this translates as larger vascular territories showing greater improvement in NIHSS after tPA than smaller vascular territories.

There's a bit of a bias in this study, since smaller vascular territories may have produced smaller initial NIHSS.  The population was quite old for a stroke study – median age 79.  And, truly, the more interesting data presented is the breakdown demonstrating the massively favorable impact of early (within 1 hour) recanalization after tPA administration.

But, mildly interesting paper, important as part of a slow, gradual trend of attempts to delineate which patients have the best potential to benefit from tPA.

"DWI-ASPECTS as a Predictor of Dramatic Recovery After Intravenous Recombinant Tissue Plasminogen Activator Administration in Patients With Middle Cerebral Artery Occlusion"
www.ncbi.nlm.nih.gov/pubmed/23212169

Monday, December 24, 2012

Saving Lives Through More Sleep

Or, at least, that's the theory.  Ever since the infamous Libby Zion case – surely exemplar of similar occurrences throughout medicine training programs – institutional focus on resident workload and wellness has been emphasized as a surrogate marker for patient safety.  Better-rested residents, working fewer hours, will have fewer misses and derive more substantial benefit from their educational opportunities.

This randomized trial from the University of Pennsylvania evaluating the performance of the new protected sleep time afforded to interns under ACGME rules.  These authors used wrist-based sleep activity monitors to measure the cumulative sleep time on-shift for interns randomized to either traditional 30-hour blocks or blocks with a nap period between 12:30am and 5:30am.  The primary outcome was sleep obtained on shift, with secondary outcomes being total hours of sleep during a call cycle, and post-call scores on the Karolinska Sleepiness Scale.

Well, protected sleep time works – 2.86 vs. 1.98 hours of sleep at the VA hospital, and 3.04 vs. 2.04 at the University hospital, with significantly fewer no-sleep nights as well.  And, the Karolinska Sleepiness Scale means also favored the nap-time group 7.10 vs. 6.65 at the VA and 6.79 vs 5.91 at the University.

But, as I said before, these are surrogate markers for patient safety.  One extra hour of sleep?  Less than a full point on the KSS?  Let's look specifically at the subjective self-reported meaning of the KSS in the range these physicians were reporting:

  • 5 = neither alert nor sleepy
  • 6 = some signs of sleepiness
  • 7 = sleepy, but no effort to keep awake
  • 8 = sleepy, some effort to keep awake

Regardless of intervention group, they're ... pretty much a little sleepy, but not generally struggling to stay awake.  I remain a little skeptical this will account for a substantial improvement in patient safety – at least, at this single-residency experience.

"Effect of a Protected Sleep Period on Hours Slept During Extended Overnight In-hospital Duty Hours Among Medical Interns"