When life gives you LEMONs- Predicting difficult intubations in the ED

Article:

Reed MJ, Dunn MJ, & McKeown DW. Can an Airway Assessment Score Predict Difficulty at Intubation in the Emergency Department? Emerg Med J 2005; 22(2): 99 – 102.

Main Points:

  1. Rapid assessment tools can be helpful in predicting difficult intubations in the emergency department
  1. Use of SOME elements of the LEMON (look, evaluate, mallampati, obstruction, neck mobility) approach to airway assessment MAY be helpful in predicting likely laryngoscopic view (Cormack- Lehane grade) as a proxy for difficulty of intubation. The following are more likely found in patients with high grade views (2-4).
  • large incisors
  • reduced inter-incisor distance
  • reduced thyroid to floor of mouth distance

Background:

Predicting difficult intubations is not always straightforward. At the time of publication (2005), little validation of rapid assessment of possible difficult intubations in the ED. The authors test the use of the LEMON approach as a predictor of difficult intubations, and suggest key parts of the assessment that are most helpful.

 

Details:

The study was a prospective, observational trial conducted in the UK at a teaching Emergency Department between June 2002 and September 2003.   156/177 patients intubated over that time were included in the study. Those excluded were done so because no LEMON assessment was completed. Of the remaining included, a modified LEMON assessment was completed including: LOOK- facial trauma, large incisors, large tongue, facial hair; EVALUATE- inter-incisor distance (<3 fingers), hyoid-mental distance (<3 fingers), thyroid to floor of mouth distance (<2 fingers); MALLAMPATI 1/2 versus 3/4 ; OBSTRUCTION; and NECK MOBILITY- cervical collar versus no collar. One point was assigned for each criterion that was found. If a criterion was though unassessable, a score of zero was given. Outcome was determined by laryngoscopic view as outlined by the Cormack-Lehane grading scale; grade 1 was considered an easy intubation, grades 2-4 were considered difficult. ALL intubations were successful, and if multiple attempts were used, the grade of view on the successful attempt was used. Authors used Fischer’s exact test to compare the categorical variables, Student’s t test to compare continuous data. Spearman rank sum test was used to assess correlation between categorical variables.

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LBBB doesn’t have to block an MI diagnosis

What we are taking about:

Sgarbossa EM, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators. N Engl J Med. 1996 Feb 22;334(8):481-7.


Main Points:

In the presence of a left bundle branch block, suspect acute infarction when:

  1. ST-segment elevation ≥1 mm and concordant with QRS complex
  2. ST-segment depression ≥1 mm in lead V1, V2, or V3
  3. ST-segment elevation ≥5 mm and discordant with QRS complex

Background:

The presence of left bundle branch block on the electrocardiogram may conceal the changes of acute myocardial infarction, which can delay both its recognition and treatment. This study aimed to identify electrocardiographic criteria for the diagnosis of acute infarction in the presence of left bundle-branch block.


Methods:

This was a retrospective cohort study looking at electrocardiograms of North American patients enrolled in the GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) trial who presented with chest pain, had left bundle-branch block on baseline EKG, and acute myocardial infarction confirmed by enzyme studies (total of 131 patients). These EKGs were blindly compared with the electrocardiograms of control patients from the Duke Databank for Cardiovascular Disease who had chronic coronary artery disease and left bundle-branch block. The patients in the control group did not have acute chest pain at the time of the electrocardiographic recording.

Multivariate Analysis was used to determine independent predictors of acute myocardial infarction. These criteria were used to develop a scoring system to identify patients with acute myocardial infarction. Continue reading

A clot in the lungs! And you are too nonspecific! You give D-dimers a bad name.

This is part of a recurring series examining landmark articles in Emergency Medicine, in the style of ALiEM’s 52 Articles.

Discussing: Wells, P., Anderson, D., & Rodger, M. (2001). Excluding Pulmonary Embolism at the Bedside Without Diagnostic Imaging: Management of Patients With Suspected Pulmonary Embolism Presenting To the Emergency Department By Using a Simple Clinical Model and D-dimer. Annals of Internal Medicine, 135(2), 98–107.

 

Main Points: Wells’ scoring system for risk of PE, when combined with a negative D-dimer, is useful to rule out patients unlikely to have significant illness from PE within the next 90 days.

  1. This scoring system combined with D-dimer measurement does not accurately identify patients who are likely to have PE at this encounter or subsequent encounters.

 

Background: Pulmonary embolism (PE) is a common disease (CDC estimates for 2015 are up to 1 in 1,000 persons) and half of patients with PE are not properly diagnosed in the ED due in part to non-diagnostic results of a V/Q scan. This reality presents a diagnostic challenge to ED physicians who are determining which patients should receive a CT scan, and risk stratifying patients for a PE. This study sought to validate the Wells’ Criteria  for determining pretest probability of pulmonary embolism in the ED population.

 

Methods: This was a prospective cohort study of consecutively recruited ED patients at four medical centers in Canada from September 1998 to September 1999. The authors excluded patients with upper extremity deep vein thromboses (DVTs) as the likely source of PE, patients who were symptom free for three days prior to presentation, those who had been on anticoagulation for 24-hours prior to presentation, patients who were not expected to live more than three months after presentation, or anyone who could not get IV contrast, was pregnant, lived too far away for follow-up, or was younger than 18 years of age.

Included patients were risk-stratified by ED physicians based upon the follow criteria:

  1. Objective clinical signs and symptoms of DVT (swelling and pain over deep vein region, 3 points)
  2. HR > 100 BPM (1.5 points)
  3. Immobilization (bed rest, except for using the bathroom, for more than 3 days) or surgery within the past fours weeks (1.5 points)
  4. Previously diagnosed DVT or PE (1.5 points)
  5. Hemoptysis (1 point)
  6. Malignancy (current diagnosis, diagnosis within the last six months, current chemo or palliative care. 1 point)
  7. PE as the most likely, or equally likely diagnosis (based upon clinical gestalt, 3 points)

A patient with a total score of less than 2 was considered low risk, 2-6 was moderate risk, more than 6 was considered high risk. Each patient’s D-dimer level was then measured, and he or she was evaluated for PE based upon an algorithm that can be found in the article (Figure 1). The evaluation included V/Q scan, bilateral lower extremity ultrasound, and/or pulmonary angiogram based upon risk stratification, D-dimer level, and imaging results.

All participants followed-up at 90 days via phone or in-person to recount events that occurred since the initial encounter.

 

Results: The data from 930 patients (average age of 50.5 years) were analysed, with prevalence of PE at 90 days found to be 9.5%. PE was diagnosed in 40.6% of patients with high pretest probability, 16.2% in moderate pretest probability group, and 1.3% in the low pretest probability group. These results indicate the negative predictive value of the d-dimer to be 97.3% in the entire cohort, and 99.5% in the low probability group, 93.9% in the moderate probability group, and 88.5% in the high probability group. In this study the Wells’ criteria/D-dimer model demonstrated poor positive predictive value because it only found PE in 16.9% of patients that were indicated to have any level of image testing (V/Q scan, DVT ultrasound, or angiography based upon the algorithm above). Seventeen patients (0.6%) who had PE and DVT ruled out based upon this model had suspicious events for PE or DVT on follow-up, with five of those events confirmed to be a PE or DVT.

 

While 17 people died during this study, none of the patients who had PE ruled out by the model died from a PE within 90 days of their initial presentation to the ED.

 

Points to consider:

  • Ten percent of the patients enrolled in the study did not have the protocol followed exactly, which limits the external validity of the study.
  • There were no imaging tests performed on the low-risk patients, so we cannot accurately say that they did not have a PE, only that they had a low risk of clinically meaningful event over the subsequent 90 days (either diagnosed PE or death).
  • This study used the more specific SimpliRED D-dimer rather than the traditional immunoassay linked D-dimer thus decreasing the sensitivity of this model compared to the traditional D-dimer assay.

 

Further Study: Only 17% of patients who ruled in for testing were found to have a PE, so there is clearly room to increase the positive predictive value of this tool. Fortunately there have been a number of subsequent studies that have tested methods to increase the specificity of this model, and we have included citations to a few of those studies in the related articles below.

 

Level of Evidence:

ACEP Clinical Policy Grading Level IIB

 

Surprises:

  1. V/Q scan was the test that was used to determine presence or absence of PE, and the current standard is CTPA as it is a more reliable test.
  2. SimpliRED D-dimer was used in this study, not the traditional immunoassay linked D-dimer, which may affect how this criteria applies to patients your department.
  3. Low risk patients got no V/Q scan, so we cannot be sure of actual incidence of PE in these patients, though they were followed up on so we do know there are few risks to not testing these patients for PE.

 

Relevant articles:

Simplification of the revised Geneva score for assessing clinical probability of pulmonary embolism: http://archinte.jamanetwork.com/article.aspx?articleid=414578

 

Performance of 4 Clinical Decision Rules in the Diagnostic Management of Acute Pulmonary Embolism: A Prospective Cohort Study: http://annals.org/article.aspx?articleid=746965

 

Diagnostic accuracy of D-dimer assay in suspected pulmonary embolism patients: http://ac.els-cdn.com/S0422763813003166/1-s2.0-S0422763813003166-main.pdf?_tid=4ce51214-6b05-11e5-9303-00000aacb35d&acdnat=1444010801_80598bd9006f6434671a010c02d76997

 

Source Articles:

Wells, P., Anderson, D., & Rodger, M. (2001). Bedside Without Diagnostic Imaging: Management of Patients With Suspected Pulmonary Embolism Presenting To the Emergency Department By Using a Simple Clinical. Annals of Internal Medicine, 135(2), 98–107.

ACEP Clinical Policy Committee. (2003). Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting With Suspected Pulmonary Embolism. Annals of Emergency Medicine, 41(2), 257–270.

Anderson, D. R., & Barnes, D. C. (2009). Computerized tomographic pulmonary angiography versus ventilation perfusion lung scanning for the diagnosis of pulmonary embolism. Current Opinion in Pulmonary Medicine, 15(5), 425–429.

Passed out…Peace out. Who can go home after syncope?

Discussing: Quinn et al. Annals of Emergency Medicine. Prospective Validation of the San Francisco Syncope Rule to Predict Patients With Serious Outcomes

Main Points:
1. This 2006 prospective cohort trial aimed to validate a clinical rule to help risk stratify patients presenting to the ER with syncope in relation to short term outcomes. The rule was validated to have a sensitivity of 98% in preventing serious outcomes after syncope within 30 days.

2. The San Francisco Syncope rule is positive if the patient has a chief complaint of “shortness of breath”, a medical history of CHF, a presenting SBP <90mm Hg, a hematocrit <30%, or an abnormal ECG result (any non-sinus rhythm or new changes).

Background:

Approximately 25% of the general population will have an episode of syncope in their lifetime. Patients with syncope account for 1-2% of all Emergency Department visits and hospital admissions. Patients admitted for syncope, however, have been shown to receive little to no further diagnostic care, nor do they often receive a firm diagnosis concerning the cause of their syncope. Given this, the authors’ purpose was to validate the decision rule in a prospective cohort of consecutive ED patients by determining whether it can predict short-term serious outcomes.

Syncope was defined as “transient loss of consciousness with return to baseline neurologic function,” and patients presenting with acute syncope or pre-syncope were screened for the study. When a clinician had finished working up the selected patient, a short Web-based questionnaire was completed to evaluate for aspects of the history, ECG, vitals or lab results that pertain to the decision rule. In this trial, the decision rule was 98% sensitive and 56% specific to predict a serious outcome within 30 days. If applied in the study cohort, this clinical rule may have decreased syncope admissions by 24%.

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‘Let’s talk about N-STEMI, Let’s talk about Cath, baby, Let’s talk about all the good things and the bad things that may be…’

This is part of a recurring series examining landmark articles in Emergency Medicine, in the style of ALiEM’s 52 Articles.

Discussing: Mehta et al., NEJM 2005. Routine vs. Selective Invasive Strategies in Patients With Acute Coronary Syndromes. A Collaborative Meta-analysis of Randomized Trials PMID: 15956636

Main Points:

  1. This 2005 meta-analysis was devised to answer one of medicine’s most stubborn (but important) questions: Is an ‘early invasive’ strategy for Unstable Angina (UA) and Non-ST-Elevation Myocardial Ischemia (NSTEMI) associated with improved outcomes compared to medical therapy alone?
  2. Yes and no! High-risk patients with positive biomarkers and evidence of ongoing ischemia seem to gain long-term benefit from immediate coronary angiography and revascularization. This benefit appears to outweigh the increased hazard associated with a routine invasive strategy.
  3. Patients with negative biomarkers and lower risk don’t appear to gain long-term benefit from invasive strategy and therefore the increased hazard of a routine invasive strategy is not justified in this group. Patients with negative biomarkers do just as well with medical therapy alone.

 

Background:

 

Acute Coronary Syndrome (ACS) comprises a spectrum of illness. Presenting signs, symptoms and clinical findings (elevated troponin, EKG changes) are thought to correlate with the degree and the acuity of ischemia. In theory, patients with more severe illness are thought to benefit from more aggressive therapies – i.e. invasive revascularization – while patients with less severe illness have been thought to derive equal benefit medical therapy alone. To an extent, these suppositions have been proven true: There are clear mortality benefits to emergent PCI for patients with STEMI. However, optimal treatment for patients presenting with unstable angina or NSTEMI remains controversial. Importantly, the goal of revascularization in STEMI is different then in NSTEMI/UA. For STEMI, PCI is intended to restore perfusion by eliminating an occlusive thrombus. In NSTEMI, thrombi typically are not occlusive – thus the focus of PCI is to improve long-term outcomes.

 

The purpose of this study was to determine whether a routine invasive strategy vs. a selective invasive strategy was more effective in the treatment of ACS. The authors devised a meta-analysis of randomized trials to answer this question. Continue reading

Slow, big breaths ain’t what the doctor’s ordering

This is part of a recurring series examining landmark articles in Emergency Medicine, in the style of ALiEM’s 52 Articles.

Discussing:  The Acute Respiratory Distress Syndrome Network. “Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome” N Eng J Med, May 2000; 342(18): 1301-08

Main Points

This landmark study was stopped early! It determined that in patients with acute respiratory distress syndrome (ARDS) who are treated with lower tidal volumes than those treated with traditional volumes:

  1. Mortality is decreased by 31.0% vs 39.8% (P = 0.007)
  2. Breathing without assistance increases by the 28th day by 65.7% vs 55.0%
  3. The number of ventilator free days increases by 12 ± 11 vs 10 ± 11. days (P = 0.007)

ARDS is a life-threatening condition for which the mortality was quoted in this study to be approximately 40 to 50 percent.  (To be blunt, any study that uses death as its primary outcome is looking at a very ill cohort.) 

Much has been learned about the pathophysiology of ARDS, but very little headway has been made in the treatment of it. The authors of this study looked at adjusting ventilatory tidal volume and plateau pressures for treatment for ARDS.  The authors also measured plasma interleukin-6 in the first 204 of 234 patients as a measure of lung inflammation. The results were significantly in favor of the lower tidal volume group.  

Details

This was a prospective, randomized controlled study that assorted 861 patients into two groups.  Patients were randomly selected to be treated with tradition ventilation treatments, initial tidal volumes of 12 ml per kilogram of predicted body weight and a plateau pressure of 50 cm of water or less, versus lower tidal volumes of 6 ml per kilogram of predicted body weight and a plateau pressure of 30 cm of water or less.

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Stop Mucking Around and Throw the End Tidal On: A Safer Way to Perform Procedural Sedation and Analgesia!

This is part of a recurring series examining landmark articles in Emergency Medicine, in the style of ALiEM’s 52 Articles.

Discussing: “Does End-tidal Carbon Dioxide Monitoring Detect Respiratory Events Prior to Current Sedation Monitoring Practices?” Burton, J. Harrah, J. Germann, C. Et al. Acad Emerg Med, May 2006, 13(5): 500-4

 

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Main Points:

  1. This trial was stopped early after an interim safety analysis demonstrated that standard care was potentially placing patients at higher risk for delayed recognition of acute respiratory events. 17 out of 20 acute respiratory events recorded in the dataset demonstrated changes in the end tidal carbon dioxide (ETCO2) level indicative of hypoventilation or apnea.
  2. Twenty acute respiratory events were recorded in the study cohort of 60 procedural sedation and analgesia (PSA) encounters. In 14 of these episodes, the ETCO2 demonstrated changes prior to SpO2 change or clinically observed hypoventilation.

Background:

PSA is a routine practice that is critical to many tasks in the emergency department. There are many guidelines from various professional societies that discuss the components of PSA and associated requirements for safe patient monitoring. Many clinicians use a wide array of pharmacologic options based on patient characteristics when performing PSA, yet it is always challenging to predict how each individual will respond to the drugs used. Therefore, having an extra tool for patient monitoring that will improve safety is a great aid for quality patient care.

ACEP has issued multiple guidelines over the past decade to keep up with the evolution of clinical practice as well as technologic changes such as capnography. Currently ACEP has a level B recommendation for the use capnography as part of the PSA monitoring tools. The article by Burton and his colleagues is one of many studies that helped change practice patterns over the past ten years. The authors collected a prospective convenience sample of two 30 patient blocks undergoing PSA at a single tertiary ED. There was an attending and 3 residents collecting ETCO2 data during PSA events and the clinical team was blinded to this information. The purpose was to identify the ability of ETCO2 to detect acute respiratory events before conventional strategies. Continue reading

Think pulmonary embolism and you may find it….

This is part of a recurring series examining landmark articles in Emergency Medicine, in the style of ALiEM’s 52 Articles.

Discussing:  “Prospective Multicenter Evaluation of the Pulmonary Embolism Rule-out Criteria.” (J Thromb Haemost 2008;  Kline JA et al.)

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boringem.org

Main Points

  1. Pulmonary Embolism Rule-out Criteria (PERC):
  • age < 50,
  • heart rate < 100 bpm
  • SaO2 < 95%
  • no hemoptysis
  • no estrogen use
  • no surgery/trauma requiring hospitalization within 4 weeks
  • no unilateral leg swelling
  • no prior venous thromboembolism

2) PERC in combination with clinical gestalt for low suspicion of pulmonary embolism (PE) reduces the probability of venous thromboembolism (VTE) to below 2%.

Background

Chest pain is the most common emergency department chief complaint.  The differential diagnosis is vast, and includes high acuity conditions (such as myocardial infarction, aortic aneurysm, and pulmonary embolism) down to low acuity conditions (such as reflux, muscle strain and anxiety.)  Pulmonary embolism is one of the high risk clinical conditions that should not be missed. However, determining which patient should or should not be worked up for pulmonary embolism can be difficult.   Continue reading

Of course the patient’s blue…that’s why I’m intubating.

 

Discussing: “Preoxygenation, Reoxygenation, and Delayed Sequence Intubation in the Emergency Department” (Weingart SD, J Emerg Med. 2010 Apr 7)

Main Points:

  1. Patients requiring intubation should be classified by oxygenation saturation as low risk, high risk and apneic.  
  2. Reservoir face masks with oxygen set at the highest rate possible are the recommended sources of high FiO2 during preoxygenation.  
  3. All patients, if possible, should be intubated with the head-elevated position to increase safe apnea time.
  4. Consider using CPAP masks, noninvasive positive pressure ventilation or PEEP valves on a bag-valve mask in patients who cannot achieve oxygen saturations greater than 93%-95%
  5. Rocuronium may provide a longer duration of a safe apneic period in patients with a high risk of desaturation.
  6. A nasal cannula set at 15 L/minute is effective at providing oxygenation during the apneic period.

Background:

Intubation is a vital procedure to the Emergency Physician.  Yet there is more to it than just placing an endotracheal tube.  There is the setup, positioning, oxygenation, sedation, checking tube placement, and more.  On top of this, there is the underlying illness to consider.  The truth is, the majority of patients intubated in the Emergency Department (ED) are sick.  Something is very physiologically wrong, and they are not maintaining adequate oxygenation.  It becomes your job to do this for them.  The authors in this article did an extensive literature review on pre-intubation and peri-intubation techniques which reduce the risk of hypoxia in the adult patient requiring intubation in the ED.   Continue reading

Crack the Chest

Part of our recurring ’52 Articles’ series exploring landmark articles in Emergency Medicine, inspired by the ALiEM blog’s index project, 

Main Points:

  1. Over 23 years 950 patients underwent post injury thoracotomy at Denver Health Medical Center and overall survival was noted to be 4.4 percent with 3.9 percent surviving functionally intact.
  1. Using various assumptions for cost analysis the authors concluded that “the benefit-charge ratio was strongly in favor of performing EDT [emergency department thoracotomy] at 5.6:1, it was 1.8:1 if adjusted for the cost of maintaining all neurologically injured survivors throughout their lifetime.”

Background:

Emergency department thoracotomy remains a hotly debated procedure within the scope of emergency medicine.  Not only is it a resource intense process that potentially places providers at increased risk for blood borne infections, but it is also one whose utility has been questioned given the limited success rate of meaningful patient outcomes. The authors of this study reviewed a cohort of consecutive trauma patients presenting to a level I hospital in Denver, CO in hopes of clarifying not only the costs as well as the utility of the procedure. The authors in this study reported “neurologically intact survival at time of discharge” as one of the study outcomes; however, it does not appear that any patients had post-hospitalization follow up to evaluate for any future changes. Continue reading