A case report describes the echo findings of a patient with a traumatic left sided pneumothorax. Although the subcostal view was unremarkable, upon imaging the parasternal region, the sonographer noted a flickering phenomenon where the heart was clearly visualized in late diastole, but would disappear in mid- systole only to reappear in late diastole during the next cardiac cycle. This ‘‘heart point’’ sign occurs because as the heart fills with blood in diastole, it enlarges and displaces the air from the precardiac space, allowing the heart to transiently contact the chest wall and be visualized with US. As the heart contracts during systole, the pneumothorax fills the space between the heart and the anterior chest wall, preventing the transmission of US and causing the heart to momentarily disappear from view.
The Heart Point Sign: Description of a New Ultrasound Finding Suggesting Pneumothorax
Academic Emergency Medicine 2010;17(11):e149–e150
Tag Archives: diagnosis
A-a gradient unhelpful in pregnancy
Given that thromboembolism is the leading cause of maternal death in the UK according to the latest UK CEMACE report, it would be nice to have reliable non-ionising tests in the ED to rapidly rule out this disease in pregnant women. Unfortunately, the alveolar-arterial oxygen gradient does not do the job.
A recent study compared the A-a gradient with CTPA as the gold standard. Of 102 patients who were pregnant or up to 6 weeks post-partum, there were 13 PEs (2 antepartum and 11 postpartum). The best sensitivity, specificity, and negative and positive predictive values for A-a gradients were 76.9%, 20.2%, 80.0%, and 11.5%, respectively.
Assessment of the alveolar-arterial oxygen gradient as a screening test for pulmonary embolism in pregnancy
Am J Obstet Gynecol. 2010 Oct;203(4):373.e1-4
Small bowel obstruction
When assessed against CT as gold standard, ultrasound diagnosis of small bowel obstruction by emergency physicians compared favourably with abdominal radiographs.
US exams were performed using a phased array probe in the bilateral colic gutters, epigastric and suprapubic regions to assess for (1) the presence of fluid-filled, dilated bowel (defined as >25mm) proximal to normal or collapsed bowel, and (2) decreased or absent bowel peristalsis (defined as back and forth movements of spot echoes inside the fluid-filled bowel). Either finding was considered ‘positive’ for small bowel obstruction.
Bedside ultrasonography for the detection of small bowel obstruction in the emergency department
Emerg Med J. 2010 Aug 22. [Epub ahead of print]
Can we tell if AF is new?
One of the dilemmas in selecting appropriate therapy for atrial fibrillation in the emergency situation is determining whether the AF is of acute onset or not. AF causes release of natriuretic peptide from the heart, so measuring these peptides may give a clue to the recency of onset if the kinetics are known. This of course can only apply to those patients without heart failure, who have another cause for elevated natriuretic peptide levels.
A study of N-terminal pro-BNP levels in patients with acute onset AF, and without clinical or radiological evidence of heart failure, showed the pattern of rise and fall. The key finding in this study is the rapid rise of plasma NT-proBNP levels to peak followed by a rapid decline, probably due to depletion of the granules in atrial myocytes in which pro-BNP is stored.
The authors describe the following implication of the study:
According to our observations, a rising trend is markedly indicative of the fact that AF onset did not happen more than 24–48 h before presentation. As a consequence, obtaining two to three plasma NT-proBNP levels within 24 h of presentation in patients with AF without heart failure who cannot satisfactorily pinpoint the time of onset may assist in determining whether the onset of the arrhythmia was recent. Such information is pertinent to decisions concerning anticoagulation and cardioversion.
Short-term fluctuations of plasma NT-proBNP levels in patients with new-onset atrial fibrillation: a way to assess time of onset?
Heart. 2010 Jul;96(13):1033-6
Fancy new ACS tests
It’s hard to keep track of all new proposed biomarkers that may be useful in the work up of acute coronary syndrome (ACS) patients. We’re all used to troponin now – so we really want to know how novel tests measure up against the existing standard, in particular for the timeframe in which troponin is less helpful, namely the first six hours.
A systematic review examine the evidence for the following biomarkers in the early assessment (ie, within 6 h of symptom onset) of suspected ACS:
- CK-MB: CK-MB and 2 h ΔCK-MB have potential in diagnosing AMI in the first hours after symptom onset. Whether CK-MB has value in the early diagnostic assessment of ACS in addition to clinical symptoms, ECG or other markers has rarely been studied.
- myoglobin: myoglobin might be of value in early ruling out of AMI and ACS in suspected patients because of the relatively high NPV; its PPV, however, is low. However, it is not yet known whether myoglobin has diagnostic value in addition to symptoms, signs and other diagnostic tests (eg, ECG), because of the lack of multivariable analysis
- heart-type fatty acid binding protein (H-FABP): H-FABP seems to have some potential as an early diagnostic marker of AMI or ACS, but its value in addition to clinical features and other markers has not been studied
- ischemia modified albumin (IMA): IMA could be a potential marker for early ruling out of ACS in chest pain patients because of its relatively high NPV, especially combined with cTn and ECG. However, its PPV is low. Importantly; IMA seems to add relevant diagnostic information to more readily available diagnostic parameters. However, problems with the stability of IMA and its lack of cardiospecificity have been reported
- pregnancy-associated plasma protein A: contradictory results indicate that the diagnostic value of PAPP-A in patients suspected of having ACS has not been evaluated properly
- glycogen phosphorylase isoenzyme BB: GPBB might be a marker for myocardial ischaemia and myocardial necrosis, although the available research is limited and does not assess the added value of the marker.
- myeloid-related protein 8/14: more research is needed to evaluate the (added) diagnostic value of MRP 8/14 in patients suspected of having ACS.
The authors also point out the introduction of high-sensitivity troponin assays may further improve diagnosis of ACS. They refer to a study in patients with suspected AMI presenting at the emergency department, which showed that a sensitive cTnI assay had a higher NPV than a standard cTnT assay and comparable PPV for detecting AMI within 6 h of symptom onset. The PPV was 79.3% and 80.7%, respectively; the NPVs were 95.3% and 88%. The Full Text of this high-sensitivity troponin paper is here
The review makes the following conclusions:
- current guidelines advocate the use of cardiac troponin or CK-MB when cTn is not available, and myoglobin in the first 6 h in addition to cTn
- IMA and H-FABP seem to be promising diagnostic biomarkers in the early diagnostic assessment of patients suspected of having ACS
- There is an urgent need for adequately designed studies of (novel) ACS markers and their combinations against contemporary troponin assays
Novel biochemical markers in suspected acute coronary syndrome: systematic review and critical appraisal
Heart. 2010 Jul;96(13):1001-1
Another pneumoperitoneum
This Video from Academic Emergency Medicine shows distinct hyperechoic foci with reverberation artifacts visualised within free fluid, suggesting associated free intraperitoneal air (in a patient with a gastric perforation)
The full article is available here
Pneumoperitoneum
This video from the Trauma Association of Canada shows sonographic detection of intraperitoneal free air
[quicktime]http://www.traumacanada.org/media/pneumoperitoneum_video.mov[/quicktime]
Finding the sick febrile kid
Finding children with serious illness among the multitudes who present with fever is the number one challenge in paediatric emergency medicine.
A two year prospective cohort study was conducted at the Children’s Hospital Westmead in Sydney to develop and test a multivariable model to distinguish serious bacterial infections from self limiting non-bacterial illnesses.
A standardised clinical evaluation that included mandatory entry of 40 clinical features was recorded by physicians on around 15000 febrile kids under age 5. Clinical, laboratory and radiological follow up was undertaken to identify one of three key types of serious bacterial infection (SBI): urinary tract infection, pneumonia, and bacteraemia.
7.2% had SBI – urinary tract infection 3.4%, pneumonia 3.4%, and bacteraemia 0.4%.
A diagnostic model was developed using multinomial logistic regression methods. Physicians’ diagnoses of bacterial infection had low sensitivity (10-50%) and high specificity (90-100%), whereas the clinical diagnostic model provided a broad range of values for sensitivity and specificity.
The authors suggest that a computer assisted diagnostic decision tool could be used to determine the likelihood of serious bacterial infection.
The strongest positive predictors of serious bacterial infection were a generally very unwell appearance, high temperature, chronic disease, and prolonged capillary refill time. For children with pneumonia, other predictors were coughing, difficulty breathing, abnormal chest sounds, and to a lesser extent tachypnoea, chest crackles, and tachycardia. For urinary tract infection, the presence of urinary symptoms was by far the strongest indicator, whereas for bacteraemia, tachycardia and crying were also strong indicators although an editorial points out that only 64 cases of bacteraemia occurred, so this last result should be treated with caution.
The accuracy of clinical symptoms and signs for the diagnosis of serious bacterial infection in young febrile children: prospective cohort study of 15 781 febrile illnesses
BMJ. 2010 Apr 20;340:c1594
Delirium guidelines
The UK’s National Institute for Health and Clinical Excellence (NICE) has produced guidelines on delirium.
Delirium (sometimes called ‘acute confusional state’) is a common clinical syndrome characterised by disturbed consciousness, cognitive function or perception, which has an acute onset and fluctuating course.
Some snippets from the guideline include:
- If indicators of delirium are identified, carry out a clinical assessment based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria or short Confusion Assessment Method (short CAM) to confirm the diagnosis.
- In critical care or in the recovery room after surgery, CAM-ICU should be used. A healthcare professional who is trained and competent in the diagnosis of delirium should carry out the assessment.
- If there is difficulty distinguishing between the diagnoses of delirium, dementia or delirium superimposed on dementia, treat for delirium first.
- If a person with delirium is distressed or considered a risk to themselves or others and verbal and non-verbal de-escalation techniques are ineffective or inappropriate, consider giving short- term (usually for 1 week or less) haloperidol or olanzapine.
The CAM-ICU assessment tool is demonstrated in the video below, which is found along with other helpful delirium resources at http://www.icudelirium.co.uk
NICE Guidance: Delirium: diagnosis, prevention and management
Complex acid-base problems
Working out the expected compensatory response to an acid base disturbance often reveals a second acid-base problem that was otherwise hidden. I regularly use Winter’s formula when I see a metabolic acidosis, but I have trouble remembering the others, so here they are, from Harwood-Nuss’ Clinical Practice of Emergency Medicine (apologies if you ‘think’ in kilopascals):
Formulas Describing Expected Compensatory Response to Primary Acid–Base Disturbances
Simple Metabolic Acidosis
- Predicted decreased PCO2 mm Hg = 1.2 × Δ(HCO3-) mEq/L
- Predicted PCO2 mm Hg = 1.5(HCO3-) mEq/L + 8 ± 2
- Anticipated PCO2 approximates last two digits of arterial pH
Simple Metabolic Alkalosis
- Predicated increased Δ PCO2 mm Hg = 0.67 × Δ(HCO3-) mEq/L
Simple Acute Respiratory Acidosis
- Predicted decreased ΔpH units = 0.8 × Δ PCO2 mm Hg
- Predicted increased Δ(HCO3-) mEq/L = 0.1 × Δ PCO2 mm Hg
Simple Chronic Respiratory Acidosis
- Predicted decreased ΔpH units = 0.3 × Δ PCO2 mm Hg
- Predicted increased Δ(HCO3-) mEq/L = 0.35 × Δ PCO2 mm Hg
Simple Acute Respiratory Alkalosis
- Predicted increased ΔpH units = 0.8 × Δ PCO2 mm Hg
- Predicted decreased Δ(HCO3-) mEq/L = 0.2 × Δ PCO2 mm Hg
Simple Chronic Respiratory Alkalosis
- Predicted increased ΔpH units = 0.17 × Δ PCO2 mm Hg
- Predicted decreased Δ(HCO3-) mEq/L = 0.5 × Δ PCO2 mm Hg