Journal Feed Weekly Wrap-Up
- Oct 16th, 2021
- Clay Smith
#1: Is Distal (aka Calf Vein) DVT as Dangerous as Proximal DVT?
Patients treated with anticoagulation for isolated distal deep vein thrombosis (IDDVT) vs. proximal deep vein thrombosis (PDVT) did not experience significant differences in overall mortality, VTE recurrence, major or minor bleeding within 12-months. Subgroup analysis found lower recurrence rates, major bleed, and death in those treated with DOACs vs. UFH/LMWH/warfarin.
Why this does this matter?
CHEST guidelines recommend serial imaging without anticoagulation in select patients with IDDVT, and ACEP has B level evidence for anticoagulation. Both CHEST and ACEP recommend DOACs as the first-line therapy in uncomplicated patients who undergo anticoagulation. Understanding outcomes for patients with IDDVT vs PDVT could sway our decision to anticoagulate or not, what anticoagulant to use, and help us provide appropriate shared decision making and education for our patients.
Continued stasis in ED management
This was a single-center retrospective study of 1922 consecutive LE DVT patients diagnosed with ultrasound who were treated with anticoagulation. 746 had IDDVT, defined by isolation to the posterior tibial, peroneal, soleal, or gastrocnemius venous segments. 1176 had PDVT, defined by any involvement of the popliteal femoral or iliac veins, including those with coexisting distal involvement. IDDVT was more often related to recent surgery, immobilization, or trauma, while PDVT was more often unprovoked or in the setting of active malignancy. A larger majority of PDVT patients had a history of VTE.
Within 12 months, 2.3% of IDDVT and 3.1% of PDVT (p=.217) experienced recurrent VTE, which manifested as PE in 60% of IDDVT and 39.5% of PDVT. 7.2% of IDDVT vs 3.9% of PDVT (p =0.001) had died at 3 months, but death at 12 months was similar at 14.6% in IDDVT and 13.4% in PDVT (p=.468). Major bleeding within 12 months occurred in 3.2% of IDDVT and 4.3% of PDVT (p=.217). In both IDDVT and PDVT, a statistically significant lower proportion of VTE recurrence, major bleeding, and death was observed in those treated with DOACs vs. LMWH/UFH/warfarin; however, results may have been confounded.
This study excluded IDDVT patients managed without anticoagulation and serial observation, was not limited to those diagnosed in the emergency department, and did not compare those managed solely outpatient versus those admitted. For this reason, the findings are not as informing for ED management. However, this study makes me more apt to treat IDDVT and use a DOAC. If a patient can’t afford or obtain a DOAC, it makes me nervous considering them for outpatient treatment.
Outcome of anticoagulation in isolated distal deep vein thrombosis compared to proximal deep venous thrombosis. J Thromb Haemost. 2021 Sep;19(9):2206-2215. doi: 10.1111/jth.15416. Epub 2021 Jul 21.
#2: An Easier Way to Find the Cricothyroid Membrane
Anesthesiologists were more successful in identifying the cricothyroid membrane (CTM) when palpating upwards from the sternal notch compared to palpating down from the hyoid bone.
Why does this matter?
In a can’t oxygenate – can’t ventilate scenario, a surgical airway is needed. Accurately identifying the proper landmarks (the CTM) is a key component to the successful surgical airway. Studies show palpation techniques are not always accurate. If there was a new palpation technique that improved accuracy, it would be an easy step to take in helping secure a surgical airway.
Started from the bottom, now we’re here
Patients undergoing general anesthesia during elective procedures were randomized to two manual palpation techniques for identifying the CTM. The study designers chose to exclusively use female patients because identification of the CTM is more challenging than males. The first “conventional laryngeal handshake” method utilizes grasping the hyoid bone and subsequently moving in a caudal direction, next identifying the thyroid laminae, then the CTM. The second “modified upwards laryngeal handshake” involves grasping the trachea at the sternal notch and moving in a cranial direction until the cricoid cartilage is palpated, then subsequently identifying the CTM.
Confirmation of the CTM location was done using ultrasound. Patients randomized to the modified laryngeal handshake technique (n=99) were more likely to correctly identify the CTM than those randomized to the conventional laryngeal handshake technique (n=99) (84% vs 56%, OR 4.36, 95%CI 2.13 – 8.93, p < 0.001). Midline was also more likely to be correctly identified in the modified technique, and there was no difference in time taken to identify the CTM between techniques.
While POCUS is becoming the gold standard for identification of the CTM, it is not always practical or available in a can’t oxygenate – can’t ventilate scenario. While patients with past laryngeal surgery or anatomical abnormalities were excluded, the results of this are intriguing. I have always palpated from the top down, and I plan on trying this new technique next time I am in the cadaver lab to see how it goes.
Comparison of the Conventional Downward and Modified Upward Laryngeal Handshake Techniques to Identify the Cricothyroid Membrane: A Randomized, Comparative Study. Anesth Analg. 2021 Sep 13. doi: 10.1213/ANE.0000000000005744. Online ahead of print.
Traditional laboratory cutoff values for D-dimer assays can still be employed in patients with COVID-19 to effectively rule out pulmonary embolism.
Why does this matter?
COVID-19 has been shown to induce a hypercoagulable state which makes patients more prone to form blood clots. Additionally, many symptoms of COVID-19 overlap with symptoms of PE, which may increase provider suspicion, tempting a clinician to go straight to CT pulmonary angiography (CTPA). Utilizing D-dimer testing may decrease the number of unnecessary scans and radiation exposure, but can we trust it in COVID-19 patients?
To the donut of truth?
This multicenter retrospective observational cohort study identified 1158 patients from five EDs within a single hospital system that underwent CTPA and D-dimer testing during a single encounter. There were two different D-dimer assays used; however, standard cutoff values were followed for each individual assay. D-dimer testing had to be performed within 24 hours of CTPA scan but was not always performed prior to CTPA (D-dimer was a standard admission lab in COVID positive patients). Patients were classified as COVID positive if they had a positive test at any point during the encounter. In COVID positive patients, the sensitivity of D-dimer testing was 100% (95%CI 87.6%-100%), specificity was 11.9% (95%CI 7.9%-17.1%), and negative predictive value (NPV) was 100%. In COVID negative patients the sensitivity was 97.6% (95%CI 91.5%–99.7%), specificity was 14.4% (95%CI 12.1%–17%), and NPV was 98.3% (95%CI 93.8%–99.6%). Based on this study, the strong NPV amongst COVID patients with a negative D-dimer would allow us to effectively rule out PE.
Additionally, ROC curves were constructed for each assay, and authors found that increasing the cut-offs from 0.5 mg/L FEU (fibrinogen equivalent units) to 0.67 mg/L FEU for assay 1 and from 230 ng/mL DDU (D-dimer units) to 662 ng/mL DDU for assay 2 allowed for maintenance of 100% sensitivity while increasing specificity to 28.9% on assay 1 and 58.5% on assay 2. These results suggest a higher cutoff value, or COVID adjusted D-dimer, may improve diagnostic accuracy and is an area of interest for future studies.
The impact of COVID-19 on the sensitivity of D-dimer for pulmonary embolism. Acad Emerg Med. 2021 Aug 23. doi: 10.1111/acem.14348. Online ahead of print.