Novel Management of PEA Arrest (Calgary EM Journal Club)

ACLS management of PEA arrest is traditionally done using CPR, epinephrine and running through the H’s and T’s. Unfortunately, the H’s and T’s can be difficult to recall in a stressful situation, and furthermore, they do not approach cardiac arrest in a physiologic manner.

We recently reviewed the following paper that uses a novel approach to the management of PEA arrest.

Littmann et al. (2013) A simplified and structured teaching tool for the evaluation and management of pulseless electrical activity. Medical Principles and Practice 2014.

Hypothesis

The authors suggest a revision of the current approach to PEA arrest in order to streamline diagnosis and thus guide resuscitation.

Methods:

The authors reviewed the current evidence around the ACLS guidelines.

Results/Proposed recommendations

Based on the literature review the authors felt cause-specific treatment of PEA arrest is more user friendly than the current ACLS teaching for a number of reasons.

  • The current ACLS teaching H’s and T’s of ACLS are cumbersome.
  • The current ACLS teaching is difficult to remember in code situation.
  • The proposed changes focus on more likely causes of PEA arrest.
  • The proposed changes provides a framework to work from.

As a result, the authors proposed the following algorithm to diagnose and manage the most common underlying etiologies of PEA arrest.

littman_pea_algorithm

 

Photo courtesy Adelaide Emergency Physicians

Conclusion

The authors felt that their simplified and structured approach offered additional advantages over the current ACLS teachings in three main ways:

  1. Organized approach using EKG telemetry to differentiate between narrow complex (mechanical cause) vs. wide complex (Metabolic cause) PEA.
  1. The structured approach reduces the number of possible diagnosis for either wide or narrow QRS morphology.

 

Wide complex

A wide complex morphology in PEA arrest is likely to be hyperkalemia or sodium channel blocker toxicity.

 

Narrow complex

Whereas a narrow complex EKG are more likely to be due to PE, cardiac tamponade, tension pneumothorax or hyperinflation. In addition, with narrow complex morphology in PEA arrest, the use of ED ultrasound is likely to further identify the underlying cause.

 

  1. The algorithm provides specific treatment recommendations depending on the initial QRS morphology.
  1. Wide complex
    1. In the case of a wide complex (metabolic cause) PEA arrest the recommendations suggest IV calcium chloride and sodium bicarbonate depending if the clinical picture is hyperkalemia or sodium channel blockers overdose.
  1. Narrow complex
    1. In the case of narrow complex (mechanical cause) PEA arrest the recommendation suggest fluids wide open and using additional ultrasound to help determine if pericardiocentesis, needle decompression, thrombolysis or ventilator management is needed.

Critical Appraisal:

Pro:

  • A comprehensive review of current ACLS PEA arrest guidelines
  • Common sense approach to PEA arrest

Cons:

  • Recommendation only – not a study
  • No data to suggest improved outcomes etc.
  • Difficult to conduct future RCT to determine effect.

 

Journal Club Discussion:

There were a number of strengths and weaknesses that came out of the group discussion:

Strengths:

  • The recommendations were based on solid review of the current literature/guidelines and most liked the idea of a structured approach to PEA arrest.
  • The recommendations focused on the most likely causes of PEA arrest and removed ancillary causes that would appear obvious during assessment (eg. Hypothermia, hypoxia). The group agreed that this provided for a more manageable list to remember as well as a framework for treatment.
  • The addition of mechanical hyperinflation as a cause was uniformly agreed as a strong point of the recommendations.
  • The additional use of ultrasound was seen as a good step forward in helping to better identify underlying etiology of the PEA arrest.

Weaknesses:

  • The absence of trauma, hypokalemia, hypoglycemia, hypothermia, hypoxia and acidosis was a concern for some who felt that there can be subtle presentations that would go un-noticed.
  • Generalizable/Staff dependent – Requires ED physicians to be trained in use of ultrasound. (eg. rural areas etc.)

 

Overall, most journal club participants agreed that the framework was a good idea and helped with recall of important etiology; however, most did say that it would not substantially change their practice as they already use the current model without difficulty or use a modified version of the proposed recommendations.

For more reading on PEA, and whether it actually exists, check out the EDECMO podcast episode #13, here.

Cheers,

Chris

 

 

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Empiric antibiotics after cardiac arrest?

The July 2014 EM:RAP Paper Chase reviewed a paper claiming 38% of OHCA (Out of Hospital Cardiac Arrest) patients are bacteremic, and thus we should routinely give antibiotics to post-arrest patients.

We reviewed this paper at the Calgary Journal Club recently and unfortunately, the authors conclusions are more leap of faith than anything else.

This single center, prospective observational trial enrolled a convenience sample of 250 OHCA patients, 77 were excluded and 173 were analyzed.   Anaerobic and aerobic blood cultures were taken at the time of arrest.

65/173 (38%) of cultures were positive, and ED survival was lower in the bacteremic vs. non bacteremic group (25% vs. 40%, p<0.042).  Sounds great until you see there are no differences between groups for length of stay, overall and 28 day mortality (p>0.05).

When critically appraising the article, we find the following.

  • Pros:
    • Prospective, observational study that may become the pilot for further study into bacteremia and OHCA
  • Cons:
    • Single centered
    • Study was not designed to determine the infectious causality of cardiac arrest or factors influencing ROSC
    • Randomly drawn blood cultures, true prevalence of bacteremia is not known
  • Discussion Points – AKA Concerns
    • The results of this study were not generalizable to our population (or most) given that the study was conducted in an inner city hospital in Detroit with an 85% African American population.
    • The definition of bacteremia in the study:
      • It was unclear how many blood cultures were drawn in total
      • There was an unknown timeline of blood culture growth – with late cultures more likely representing a contaminant
      • Their definition led to a huge sensitivity but a low specificity
      • The species distribution heavily favoured skin flora. And some of those species are not pathologic invasive species (eg. S. epidermidis)
    • The question of whether the OHCA caused the bacteremia vs. the bacteremia causing the cardiac cannot be answered based on this paper. It is likely that a large proportion of the bacteremic patients were contaminants. It is also likely that sicker patients received more lines, another potential for skewing these patients towards bacteremia.
    • It was discussed that 69% of bacteremic patients vs only 30% of non-bacteremic OHCA ED survivors received empiric antibiotics. It was thought that this suggests that ED staff are able to identify something different about these patients from the presentation leading them to suspect sepsis. It would have been a nice question to ask the ED staff the question: “What was your working diagnosis?” to see if sepsis was suspected at a time after antibiotic administration.

To summarize, the study results dont’ support the author’s conclusions. The authors speculate on potential causation based on weak data. They cannot imply causation based on this study. We agree with the authors that more study is needed to determine temporal causation regarding bacteremia and cardiac arrest.

It was universally decided that this paper would not change our practice overall and that bacteremia in OHCA is an interesting idea, more investigation is needed. Also, we should really be vigilant for inciting infectious causes of OHCA and initiating antibiotics early when infection is suspected.

Cheers,

Chris 

Coba et al. The Incidence and Significance of Bacteremia in Out of Hospital Cardiac Arrest. Resuscitation 2014.

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Pericarditis: Treatment and Diagnosis Pocket Card

1heart

Hi all,

This post contains a pocket card for the evidence based diagnosis and treatment of pericarditis as of 2014.  This came up after a recent U of C EM Journal Club in which the residents commented that there was just too much to remember with regard to the use of colchicine, it’s dosing, contraindications, etc. when treating pericarditis on shift.

You can take a look at my post reviewing the evidence on colchicine for pericarditis over at REBEL:EM, as well as the recent Calgary journal club review of Imazio’s ICAP paper, here.

This card will serve as a quick resource which you can put into your evernote or download onto your phone as a pdf file for on shift use.

Disclaimer: Everything here is evidence based, but the dosing of NSAID or ASA has not been compared/optimized in studies.  The listed dosing regimens are my own suggested ones, but feel free to modify as you see fit.

pericarditisPVcardCalgaryversion

Screen shot 2015-01-17 at 4.43.50 PM

To download a PDF version of the pocket card,  click here.

pericarditisPVcardCalgaryversion

Cheers,

Chris

 

 

 

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Pericarditis and Myocarditis (Calgary EM Journal Club)

1heart

The December journal club reviewed two papers, first up was Imazio’s paper investigating the benefits of treating pericarditis with colchicine.  You should definitely know this paper and be implementing it into practice. This is a must read.

The second paper was a retrospective review looking at the presenting symptoms and labwork abnormalities in pediatric myocarditis.

Paper #1

Imazio et al. A Randomized Trial of Colchicine for Acute Pericarditis NEJM 2013

METHODS/SETTING/DESIGN/NUMBER OF PATIENTS INCLUDED

  • Multicenter, double-blind randomized trail
  • 240 patients, 120 per study group

INTERVENTION/CONTROL

  • Colchicine at a dose of 0.5mg BID for 3 months for pts weighing > 70kg or 0.5 mg once daily for patients weighing <= 70 kg, vs placebo.
  • Each participant also took a tapering dose of conventional anti-inflammatory therapy with aspirin, Ibuprofen, or corticosteroid.
  • PPIs were also prescribed for GI prophylaxis

INCLUSION CRITERIA

  • 18 years of age or older
  • First episode of pericarditis
  • Etiology either idiopathic, viral, after cardiac injury, or associated with connective tissues disease
  • Acute pericarditis was diagnosed with 2 of the following:
    • Typical chest pain (sharp and pleuritic, improved by sitting up and leaning forward), or pain radiating to trapezius ridge.
    • A pericardial friction rub
    • Suggestive changes on ECG (widespread ST segment elevation or PR depression)
    • New or worsening pericardial effusion

EXCLUSION CRITERIA

  • Tuberculous, neoplastic, or purulent pericarditis
  • Evidence of myopericarditis as indicated by elevation in serum troponin levels. This has become controversial with the new use of high sensitivity trops.
  • Severe liver disease or current aminotransferase levels of more than 1.5 times the upper limit of the normal range
  • Serum creatinine level of more than 221 umol/L
  • Skeletal myopathy or a serum CK level above upper limit of the normal range
  • Blood dyscrasia
  • Inflammatory bowel disease
  • Hypersensitivity to Colchicine or CI to it’s use
  • Current treatment with Colchicine
  • Life expectancy of < 18 months
  • Pregnant, lactating women, or women of childbearing potential who were not protected by contraception

OUTCOMES

Outcome measure(s):

Primary

  • Incessant or recurrent pericarditis

Secondary

  • Symptom persistence at 72 hours
  • Remission within 1 week
  • Number of recurrences
  • The time to the first recurrence
  • Disease-related hospitalization
  • Cardiac tamponade
  • Constrictive pericarditis

RESULTS

PRIMARY OUTCOME

  • Incessant or recurrent pericarditis occurred in 20 patients (16.7%) in the colchicine group, and 45 patients (37.5%) in the placebo group
  • Relative risk reduction in the colchicine group of 0.56; 95% CI
  • NNT to prevent on case of incessant or recurrent pericarditis was 4

SECONDARY OUTCOME

  • Reduced frequency of symptom persistence at 72 hours (19.2% vs 40.0%, P=0.001)
  • Reduced number of recurrences per patient (0.21 vs 0.52, P=0.001)
  • Reduced rate of hospitalization related to pericarditis (5.0% vs 14.2%, P=0.02)
  • Improved rate of remission within 1 week (85% vs 58.3%, P< 0.001)
  • Prolonged time to first recurrence (24.7 weeks vs 17.7 weeks, P <0.001)
  • No significant difference in the incidence of adverse events (9.2% vs 8.3% for GI side effects)
  • Multivariable analysis showed independent risk factors for recurrence were the use of glucocorticoids (OR 4.17,95% CI, 1.28 to 13.53; P=0.02) and CRP elevation at presentation (OR 3.15; 95% CI, 1.05 to 9.49; P=0.04)

STUDY CONCLUSION

  • In patients with acute pericarditis, colchicine, when added to conventional anti-inflammatory therapy, significantly reduced the rate of incessant or recurrent pericarditis

CRITICAL APPRAISAL

Pros: This was a well designed, randomized, double-blind placebo controlled trial that was powered to find a clinically meaningful difference in a patient-centred outcome. The population studied was fairly representative of the patient population we will be seeing in the ED, and the follow-up interval was adequate, with excellent treatment adherence.

Cons: This study was not powered to detect differences in the more rare side effects that can be associated with colchicine, though it is not pragmatic to design such a trial. As there was no pre-planned subgroup analysis of patients who received the weight-adjusted lower dose versus those who received the conventional dose, and there is no evidence to suggest why a cut-off of 70kg was used, it is not accurate to state that low dose and conventional dose colchicine are equally efficacious, though it is biologically plausible and also supported by the results of the CORE and COPE trials.

Discussion Points: In light of the strong methodology of this trial, as well as multiple other favorable trials of colchicine in acute pericarditis (eg. CORP, COPE, recent Cochrane Review), using colchicine in first-episode, uncomplicated pericarditis patients will be considered by most staff. The trial used dosing regimens of 0.5-1.0mg daily based on patient weight; however, in Canada, colchicine is available as 0.6mg tablets, which would result in a 20% higher dose than that in the study. The clinical criteria used to define acute pericarditis in the trial are helpful to making the diagnosis of pericarditis in practice. Surprisingly, there was no increase in adverse GI side effects in the colchicine group.

Paper #2

Freedman et al. Pediatric Myocarditis: Emergency Department Clinical Findings and Diagnostic Evaluation Pediatrics 2007

OVERVIEW: This was a retrospective study aimed at describing the clinical presentations of pediatric patients with myocarditis– a very rare disease. This article was used to discuss how to critically appraise retrospective studies.

METHODS/SETTING/DESIGN/NUMBER OF PATIENTS INCLUDED

  • Retrospective chart review looking at patients from May 2000 to May 2006
  • Hospital for Sick Children in Toronto
  • 31 patients with Myocarditis (16 with biopsy proven/definite myocarditis, and 15 with probable myocarditis)
  • Charts were reviewed twice by single investigator, and two investigators independently classified patients exclusively into 1 of 5 presentations

INTERVENTION/CONTROL

  • 5 ED clinical presentations were defined:
    • Respiratory (rhinorrhea, cough, shortness of breath)
    • Gastrointestinal (nausea, vomiting, diarrhea, or abdominal pain)
    • Cardiac (chest pain or palpitations)
    • Hypoperfusion (lethargy, lightheadedness, dizziness, syncope, or seizure)
    • Kawasaki associated
  • CXR defined as abnormal and associated with myocarditis if cardiomegaly, pulmonary vascular congestion, or pleural effusion present
  • ECG defined as abnormal and associated with myocarditis if one of the following present: axis deviation, decreased ventricular voltages, ST segment or T wave abnormalities, atrial enlargement, ventricular enlargement, heart block, or an infarction pattern
  • Echocardiogram findings defined as consistent with myocarditis included increased ventricular end systolic or diastolic dimension, reduced shortening or ejection fractions, atrioventricular valve regurgitation, and regional wall motion abnormalities
  • Lab tests used age appropriate normal values were used (troponins were not used)

INCLUSION CRITERIA

  • All patients < 18 yrs of age
  • Diagnosed at Hospital for Sick Children as having myocarditis between May 2000 and May 2006
  • Initial presentation was to an emergency department (either Hospital for Sick Children or transferred from another institution) or if the child underwent autopsy at Hospital for Sick Children and had a diagnosis of myocarditis
  • Initial presentation with myocarditis
  • Either having definite myocarditis (biopsy proven) or probable myocarditis (diagnosis assigned by pediatric cardiologist on basis of history, physical examination, and investigation results in the absence of an endomyocardial biopsy or in presence of negative biopsy results)

EXCLUSION CRITERIA

  • No ED visit
  • Patients who did not meet the definitions of definite or probably myocarditis
  • Inadequate documentation of initial presentation
  • Discharge diagnosis other than myocarditis

OUTCOMES

Outcome measure(s):

Primary

  • Relative frequency of ED presenting symptom complexes in children with myocarditis

Secondary

  • Sensitivity of clinical exam findings, laboratory investigations, chest radiographs, ECGs, and echocardiograms in diagnosis myocarditis

RESULTS

PRIMARY OUTCOME

  • The most common presenting symptoms at the time of ED presentation relate to the respiratory system
  • These are age related and patients > 10 years of age present predominantly with chest pain, and < 10 with respiratory symptoms. Overall more presented with respiratory symptoms

SECONDARY OUTCOME

  • Sensitivity of clinical exam findings: most common physical exam feature was respiratory distress (68%), followed by tachycardia (18%)
  • Sensitivity of laboratory investigations: AST level is most sensitive marker for myocarditis with an elevated value in 85% (including 1 child who had normal ECG and CXR
  • Sensitivity of CXR: 55% sensitivity with cardiomegaly being most common abnormality (42%), followed by pulmonary venous congestion (32%)
  • Sensitivity of ECGs: 93% of cases, with ST or T wave abnormalities being the most common (67%), and Axis deviation second with 37%
    • 97% of children with either ECG or CXR done had an abnormality on one test
  • Sensitivity of echocardiograms: 87% had abnormalities consistent with myocarditis with myocardial dysfunction detected more frequently among those with definite myocarditis

STUDY CONCLUSION

  • Pediatric myocarditis presents primarily with respiratory and cardiac complaints
  • Maintain a high index of suspicion for myocarditis even in absence of clinical findings of CHF
  • When adequate clinical suspicion exists, screening tests should include CXR and ECGs
  • Evidence of elevated liver enzyme levels should raise additional concern regarding myocarditis in the appropriate clinical scenario

CRITICAL APPRAISAL

Pros: Given how rare the diagnosis of myocarditis is (0.5/10000), the retrospective design of this trial was very appropriate. Moreover, the authors strengthened the quality of their chart review and limited potential bias as best possible by clearly defining variables a priori, drawing on multiple databases for patients to include, describing how missing or conflicting variables were dealt with, and using a third reviewer to clarify discrepancies in coding of the primary outcome.

Cons: Given that the lab tests and other investigations in the study were not necessarily applied to the entire population, a true sensitivity cannot be calculated based on the results.

Discussion Points: This article was used as an example to discuss how retrospective studies can be methodologically strengthened. Troponins were not checked routinely in this patient population. Key clinical take-homes include: the overall very low incidence of myocarditis, the biphasic age distribution, and that young children tend to present with respiratory symptoms, while older children tend to present with cardiac symptoms.

Thanks to Anjali Pandya (PGY-3 FRCPC EM program) and Tasha Haiduk (CCFP-EM resident) as well as Shawn Dowling for the journal club appraisals.

Cheers,

Chris

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Problems with the Alvarado and Pediatric Appendicitis Scores (Calgary EM Journal Club)

appendicitis

In part 1 of this journal club, we reviewed the utility of a clinical decision rule for the inconclusive ultrasound in appendicitis.  Today we look at a meta-analysis of the Alvarado and Pediatric Appendicitis Score (PAS).

Onto the article.

Ann Emerg Med. 2014 Oct;64(4):365-372.e2. doi: 10.1016/j.annemergmed.2014.02.025. Epub 2014 Apr 14.

What are the most clinically useful cutoffs for the Alvarado and Pediatric Appendicitis Scores? A systematic review.

Ebell MH1Shinholser J2.

Methods/Setting/Design

This systematic review included articles from a PubMed search and a search of reference lists of previous systematic reviews. Only prospective studies were included. Likelihood ratios were calculated for each of low, moderate and high-risk score groups for each score from the set of articles.

Total number of articles included for analysis: 26, with n = 3193 in adult studies and n = 4776 in pediatric studies.

The outcome measure was likelihood ratios calculated for various levels of Alvarado and PAS score cutoffs, deemed low (<4), moderate (5-7) and high-risk scores (>7) at various levels of pre-test probability for appendicitis.

The results of this systematic review found that in adults with a pre-test probability of >60%, and Alvarado score >7 suggests a very high likelihood (>85%) of appendicitis, while a pre-test probability of <50%, with an Alvarado score <4 suggests a very low likelihood of appendicitis (<3%).

In children with a pre-test probability of appendicitis >60%, an Alvarado score <4 suggests a very low likelihood of appendicitis (<3%), while a pre-test probability of >50% with an Alvarado score of >7 suggests a very high likelihood of appendicitis (>85%). The Pediatric Appendicitis Score was not as predictable at various pre-test probabilities for rule-out or rule-in of appendicitis.

it-is-decided

Critical appraisal and journal club consensus:

The literature search in this systematic review was incomplete, searching only one database for full-text articles, whereas a more comprehensive strategy would have searched the grey literature (published abstracts, conference abstract presentations) and there should have been a more systematic approach to searching the reference lists of published reviews. Furthermore, there were many non-English articles included and there is risk of misinterpretation of results in all of these articles. Articles included had a high degree of heterogeneity of results and should not have been pooled for analysis.

While the overall objectives of the review aim to identify clinical score cutoffs that reliably predict important clinical outcomes (i.e. >85% likelihood of appendicitis and <3% likelihood appendicitis), their results may not be easily applied to ED patient care. The results are presented in an algorithm of estimation of pre-test probability combined with either Alvarado Score or Pediatric Appendicitis Score to lead to “rule-out” or “rule-in” decisions. Estimating pre-test probability is often not so straightforward in EM practice. Estimating pre-test probability is often not so straightforward in EM practice. Additionally, we are not simply “ruling-in” appendicitis at a >85% likelihood threshold and sending patients off to surgery, as the article suggests may be done, as this would result in an unacceptable 15% negative laparotomy rateThis study does not address imaging for appendicitis as an adjunct to clinical evaluation for appendicitis, as is the common practice in the ED.

Discussion at journal club emphasized that “pre-test probability” is a difficult to quantify value, and many clinicians will rely on clinical gestalt and components of the Alvarado (+/- Pediatric Appendicitis Score) when determining pre-test probability. It follows that if forming a pre-test probability of appendicitis based on components of the scoring systems, continuing on to use the same scoring system to reach a different post-test probability is not logical or clinically sound. Furthermore, the findings rely heavily on a structured clinical scoring system to “rule out” appendicitis, which is a clinical condition that can present atypically as often as it presents typically.

Thanks to Kathryn Crowder (CCFP-EM resident) and Shawn Dowling for this summary.

Cheers,

Chris

 

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The Negative or Inconclusive Ultrasound in Appendicitis – Can a CDR help?

abdominal_pain-pic

The September edition of journal club featured two articles focused on the diagnosis of appendicitis.  These articles each highlight some critical EBM points, which is why I’m breaking them apart into separate posts. This post will only focus on the first article, which examined a potential clinical decision rule for the management of patients with inconclusive or negative ultrasonography in the setting of suspected appendicitis.

 

 

Acad Emerg Med. 2014 May;21(5):488-96. doi: 10.1111/acem.12374.

A simple clinical decision rule to rule out appendicitis in patients with nondiagnostic ultrasound results.

Leeuwenburgh MM1Stockmann HBBouma WHHoudijk APVerhagen MFVrouenraets BCobben LPBossuyt PMStoker JBoermeester MAOPTIMAP Study Group. 

 

Objective
  • Intent of the clinical decision rule (CDR) was to create a tool that could rule out appendicitis in patients with negative or inconclusive ultrasounds without additional imaging such as a CT or MRI and be safely discharged and seen the following day for reassessment.
  • Their aim was to identify low risk patients for appendicitis with negative or inconclusive ultrasound that they defined as <10%.
Setting
  • Carried out in the Netherlands at University and Teaching hospitals
Population and Inclusion Criteria
  • Development and Validation data were retrospectively extracted from 2 different imaging studies occurring at different times.
  • There were 199 patients in the development set and 120 patients in the validation set.
  • In both the development and validation set, subjects were selected from a diagnostic accuracy study and were patients with clinically suspected appendicitis that presented to the Emergency department who had negative or inconclusive ultrasound results.
  • All patients in both groups received additional imaging such as a CT scan. An expert panel that based its decision on all data attained including pathology and clinical course determined a final diagnosis of appendicitis.

appendicitisultrasoundpic

Methods
  • 14 clinical variables associated with appendicitis were identified from the two diagnostic accuracy studies.
  • Development population: Univariate logistic regression methods were used to estimate odds of appendicitis based on each variable. Those with positive association were included in a multivariable logistic regression model; ultimately they came up with the most promising variables to build the CDR. CRP was added on to see if it would increase sensitivity.
  • 4 variables were identified to make a CDR (male, migration of pain to RLQ, vomiting and WBC >12), they applied this to the development and validation population retrospectively.
Results/Conclusion
  • The 4 variables identified as most promising were male, migration of pain to RLQ, vomiting and WBC >12.
  • The addition of CRP>10 did not significantly improve the sensitivity of the rule.
  • The authors applied their 4 variable CDR to both the development and validation population set. In the development set they claim that use of the rule would reduce the probability of appendicitis from 26% (51/199 – these are the number that had +ve appy) to 12% (15/126 that were discharged ultimately had appendicitis)
  • In the validation set, applying the CDR reduced the probability of appendicitis from 20% (24/120 – total in group that had +ve appy) to 6% (4/72 – these were discharged home that ultimately had +ve appy).
  • They compare the NPV of the CDR as 94% (CI 87-98%), which was comparable to the NPV of CT and MRI (there was no statistical difference).
  • The authors conclude that their CDR significantly reduces the probability of appendicitis in negative and inconclusive u/s and those patients could be safely discharged home with next day evaluation.

Screen shot 2014-12-04 at 3.28.13 PM

Critical Appraisal/Group Discussion

There are multiple methodologic standards for interpreting a CDR.  The Annals of Emerg Med has a nice 2014 update on this here.  This would be a good paper to read or bookmark for residents.

The clinical scenario in which an emergency physician is presented with a young patient with clinically suspected appendicitis and an inconclusive ultrasound is common and one that could benefit from a well designed CDR to rule out disease in a moderate to high risk patient. Unfortunately, other than asking a relevant question, there are several limitations of this CDR that prevents it from being clinically useful.

First, the rule would have been more helpful if it resulted in a definitive course of action such as CT vs No CT or discharge only, rather than next day re-evaluation for all. Its design and methodological standards were also not ideal. Data for both the development and validation were retrospectively taken from two separate diagnostic accuracy studies that a priori were not designed to create a CDR. Patients were selected as a convenience sample introducing sampling and spectrum bias and there was no mention of blinding. Resident and staff radiologists performed ultrasounds, which is not the standard here in Canada. This may also explain the high rate of positive appendicitis in negative ultrasounds as the skill level of the ultrasonographers varied immensely.

It was also puzzling that the authors included negative ultrasounds in their study, as most physicians with a negative ultrasound would typically send the patient home with clear discharge instructions. In addition, the radiologists were aware of the fact that they were involved in a diagnostic accuracy study that likely introduced a performance bias and may have influenced the high inconclusive ultrasound rate (22 and 47%). In addition to the aforementioned, external validity was also limited by the CDR performance difference in the development and validation set (12% vs 6% miss rate) and by a high prevalence of appendicitis (52-60%). There were a few experts in pediatric appendicitis in attendance and our local data was quite different – we had a much lower prevalence of incompletely visualized appendices.

Ultimately there was consensus that a ‘miss rate’ of 12% was too high for both pediatric and adult populations. A miss rate of 3-5% would be more reasonable. In general when most staff are presented with a negative ultrasound, if there is a re-assuring re-examination of the patient they will discharge them with very clear instructions of when to return to medical attention. With respect to an inconclusive ultrasound, where there is a lot more diagnostic uncertainty, most staff will proceed to a CT scan if clinically concerned in the adult population. Our pediatric emergency colleagues typically get their patients admitted for serial examinations from general surgery.

An inconclusive ultrasound in the context of clinically suspected appendicitis remains a clinical presentation that would benefit from a CDR that is both methodologically rigorous in derivation and leads to a defined clinical action.

Look for more on appendicitis in the coming weeks.  We review a meta-analysis of the Alvarado Score and Pediatric Appendicitis Score, and focus on measures of heterogeneity within a meta-analysis.

Thanks to Natasha Wright (PGY-2) for contributing and Shawn Dowling (FRCPC) for reviewing this summary.

Cheers,

Chris

 

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