Journal Feed Weekly Wrap-Up

We always work hard, but we may not have time to read through a bunch of journals. It’s time to learn smarter. 
Originally published at JournalFeed, a site that provides daily or weekly literature updates. 
Follow Dr. Clay Smith at @spoonfedEM, and sign up for email updates here.

#1: Time = Brain in Carbon Monoxide Poisoning

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Patients treated with hyperbaric oxygen therapy (HBO2) within 6 hours of carbon monoxide (CO) exposure had better 6-month neurocognitive outcomes than patients who received treatment within 6-24 hours. Poor outcomes increased as time-to-treatment increased.

Why does this matter?
HBO2 likely decreases mortality and improves cognitive outcomes in patients with symptomatic CO poisoning. While initiation within 24 hours of exposure is recommended, previous studies have suggested better outcomes if it is started within 6 hours. When it comes to HBO2 for CO poisoning, is time really brain?

Don’t Dilly-Dally
This retrospective, single-center study of 706 patients with symptomatic CO poisoning compared neurocognitive outcomes based on HBO2 delay intervals. Patients were classified into early (≤6 hours) or late (6-24 hours) groups based on time from CO exposure to HBO2 initiation. The late group was further divided into Case-1 (6-12 hour) and Case-2 (12-24 hour) groups.

After propensity score matching, the early group showed significantly fewer poor outcomes at 6 months than the late group, as measured by Global Deterioration Scale (p=0.027). The early group also had significantly fewer poor outcomes than the Case-2 group at 1 month (p=0.035), and both Case-1 (p=0.033) and Case-2 (p=0.004) groups at 6 months. As treatment interval increased, the number of patients with poor prognoses increased (p=0.008).

This study is limited by its observational design and by the challenge of pinpointing exact CO-exposure time. Though it did not compare late HBO2 with no HBO2, the increase in poor prognoses as time-to-treatment increased suggests that we should still initiate treatment as quickly as we can.

Effect of Hyperbaric Oxygen Therapy Initiation Time in Acute Carbon Monoxide Poisoning. Crit Care Med. 2021 Oct 1;49(10):e910-e919. doi: 10.1097/CCM.0000000000005112.

#2: High or Low-Dose IM Ketorolac for Musculoskeletal Pain?

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For ketorolac dosing in acute musculoskeletal pain, 15mg IM was non-inferior to 60 mg IM.

Why does this matter?
Opioid-sparing pain management options are essential in the ED, and ketorolac is one our staples. While JF has reviewed several articles (here and here) regarding IV dosing of ketorolac, what can the literature teach us about IM dosing? Can we get maximum analgesia with minimal dosing?

Same Story, Different Route
In this single-blinded non-inferiority trial, 110 adults with acute musculoskeletal pain were randomized to either 15 mg or 60 mg of IM ketorolac. For the primary outcome, a standard 100 mm visual analog scale was used to measure change in pain at 60 minutes. The group receiving 15 mg reported a decrease in pain from baseline of 29.7 (SD 22.5) vs the 60 mg dose group whose decrease in pain was 29.9 (SD 23.1). The mean difference between the groups was 0.1 mm (95%CI -8.5 to 8.7), which was less than the predetermined non-inferiority margin of 13mm.

This small study really only tells us that 15mg IM isn’t worse than 60mg IM, but from this information, paired with other literature, we can extrapolate that using the lowest effective dose is the winning strategy for ketorolac – helping us maximize analgesia and minimize adverse effects like GI bleeding, platelet inhibition, and renal impairment.

Comparing two doses of intramuscular ketorolac for treatment of acute musculoskeletal pain in a military emergency department. Am J Emerg Med. 2021 Jul 31;50:142-147. doi: 10.1016/j.ajem.2021.07.054. Online ahead of print.

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This retrospective review demonstrated that bilateral lower extremity pain, sensory loss in a dermatomal distribution, and loss of bilateral ankle or knee reflexes were the best correlates to a radiographic diagnosis of CEC (cauda equina compression). Also, rectal exam had little to no diagnostic utility.

Why does this matter
Atraumatic back pain is an incredibly common complaint in the ED, and it is our job as ED providers to rule out the big emergencies – with cauda equina syndrome (CES) being at the top of the list. Diagnosis is time critical, but unfortunately requires significant resources (boarding time, transport, MRI techs, radiologists). Accurate and timely diagnosis of CES is challenging, as classic symptoms are often not strong predictors, and data is limited on the prognostic accuracy of individual clinical features. This study provides guidance on which symptoms and clinical findings should carry more weight when deciding what to include in your work up.

But doc…is that…necessary?

Design: This was a 4-year retrospective review within a single tertiary referral center in the UK.  Self-reported symptoms along with objective physical exam findings were collected prospectively by treating clinicians within a structured clinical proforma. Inclusion criteria were limited to patients presenting with atraumatic back pain suspected to have CEC who subsequently underwent MRI imaging to establish a “definitive” diagnosis.

Results: Of the 996 patients that met inclusion criteria, 111 (11.1%) had CEC on MRI. Authors used univariate logistic regression to identify which individual factors were associated with radiographic CEC, then subsequently performed a multivariate analysis to determine relative significance of each factor. Data from the multivariate analysis suggested that the most frequent self-reported symptom suggestive of CEC was bilateral leg pain (OR 1.9) with the most frequent objective examination findings being dermatomal loss of sensation (OR 1.7) and absent bilateral ankle or ankle and knee jerks (OR 3.4). They did not demonstrate any benefit to digital rectal examination in identifying CES. It is important to note that when the various clinical findings were described for sensitivity and specificity, the individual performance of all history or exam elements was poor.

Limitations: This was a single-center, retrospective study. Selection bias was introduced, as not all patients who presented to the ED with atraumatic back pain got an MRI; thus, there was no data on these patients to determine clinical outcome. The study also used radiographic evidence of CES as a “gold standard,” as opposed to operative findings.

Implications:  While it is certainly interesting to know which symptoms correlate most often to CEC, it might be equally important to note that the evidence also demonstrated the relative lack of importance of each individual factor when it comes to specificity and sensitivity. Knowing this, we shouldn’t rely on the presence or absence of specific clinical symptoms to rule in or rule out CES. The evidence demonstrating the limited diagnostic utility of the digital rectal exam provides an opportunity for shared decision making prior to performing this invasive exam, and, if validated in the future, could possibly be completely avoided.

Determination of potential risk characteristics for cauda equina compression in emergency department patients presenting with atraumatic back pain: a 4-year retrospective cohort analysis within a tertiary referral neurosciences centre. Emerg Med J. 2021 Oct 12;emermed-2020-210540. doi: 10.1136/emermed-2020-210540. Online ahead of print.

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