Tag Archives: Ultrasound

Saline can be used in place of US gel

A study comparing sterile saline as a conduction agent with ultrasound gel showed adequate visualization of anatomic structures for ultrasound-guided vascular access. The authors state that given sterile saline’s theoretical advantages over gel in terms of availability, cost, safety and ease of use in the procedural field, it should be considered as a viable alternative to gel as a conduction agent.

Saline - so many uses we hadn't thought of

Use of sterile saline as a conduction agent for ultrasound visualization of central venous structures
Emerg Med Australas. 2010 Jun;22(3):232-5

Ultrasound of intracranial haematoma

Using a 2Mhz transducer insonating through the temporal acoustic bone window, Italian physicians detected the expansion of an extradural haematoma. In their discussion they highlight that transcranial sonography of brain parenchyma in adults has been proposed by several authors for the evaluation of the ventricular system, monitoring of midline shift, diagnosis and follow-up of intracranial mass lesions. In one study, of 151 patients, 133 (88%) had a sufficient acoustic bone window. Note that the skull contralateral to the acoustic bone window is visualised.

Arrow indicates EDH; asterisk indicates mesencephalon

Bedside detection of acute epidural hematoma by transcranial sonography in a head-injured patient
Intensive Care Med. 2010 Jun;36(6):1091-2

B lines be gone!

Vicki Noble’s Emergency Ultrasound team describe the resolution of Songraphic B lines on the lung ultrasound of a patient with end stage renal disease who presented with dyspnoea due to pumonary oedema which was treated with CPAP.
B-lines are hyperechoic vertical lines that originate at and slide with the pleura and extend radially to the edge of the screen without fading. Isolated B-lines may be seen in normal lungs, but diffuse B-lines in multiple zones indicate interstitial thickening, most commonly seen in congestive heart failure (CHF).

Image from cardiovascularultrasound.com

This case is interesting because it describes real-time resolution of B-lines during therapy in the ED demonstrating that in CHF, B-lines reflect acute rather than chronic changes within lung parenchyma.
Real-time resolution of sonographic B-lines in a patient with pulmonary edema on continuous positive airway pressure
Am J Emerg Med. 2010 May;28(4):541.e5-8

Echo best test for acute LVF in ED

Three diagnostic tests for acute left ventricular heart failure in dyspnoeic patients were compared, with the gold standard being the diagnosis by three independent reviewers (two cardiologists and one respiratory physician) who were blinded to the results of the tests being examined. The tests in question were  NT-proBNP, the Boston criteria, and limited echo performed by emergency physicians.

The primary goal of the echo study was the detection of the following echocardiographic variables, expressed as present or absent: reduced LV ejection fraction (LV ejection fraction <50% on subjective visual estimation of the change in LV size between diastole and systole) and the ‘‘restrictive’’ pattern on pulsed Doppler analysis of mitral inflow (using the apical view).

According to the authors, pulsed Doppler analysis of mitral inflow can be described by three patterns: 1) an ‘‘impaired relaxation’’ pattern, suggesting no increase in LV filling pressures; 2) a ‘‘normal’’ or ‘‘normalized’’ pattern; and 3) a restrictive pattern, suggesting an increase in LV filling pressures.

Trained emergency physicians were able to perform EDecho in a median of 4 minutes, obtaining Doppler data in an average of 80% of patients presenting for acute dyspnea. Considering the 125 patients with both EDecho variables available, reduced LV ejection fraction was less accurate than the restrictive mitral pattern for the diagnosis of aLVHF. The restrictive pattern was more sensitive (82%) and specific (90%) than reduced LV ejection fraction and more specific than the Boston criteria and NT-proBNP for the diagnosis of aLVHF. The accuracy of the restrictive pattern in the overall population was 75%, compared with accuracy of 49% for both NT-proBNP and Boston criteria.

Diagnostic accuracy of emergency Doppler echocardiography for identification of acute left ventricular heart failure in patients with acute dyspnea: comparison with Boston criteria and N-terminal prohormone brain natriuretic peptide.
Acad Emerg Med. 2010 Jan;17(1):18-26

Oblique view for IJV cannulation

Simple really. Using the transverse view the needle tip can be hard to visualise. In the longitudinal view you don’t see the carotid artery. Applying an oblique view with an obliquely oriented needle “uses the superiority of the short axis view by visualizing all of the important surrounding structures (artery and vein) in an oblong view while allowing continuous real-time visualization of the long axis of the needle, therefore providing a larger, more easily visible target with a brighter more easily recognized needle.” The ultrasound probe is orientated at approximately 45° so that the medial end of the ultrasound probe aligns with the patient’s contralateral nipple or shoulder.

The oblique view: an alternative approach for ultrasound-guided central line placement
J Emerg Med. 2009 Nov;37(4):403-8

Full Text Article

Collapsible IVC predicts ‘low’ CVP

The IVC undergoes a change in diameter during the respiratory cycle. Investigators compared the degree of sonographic IVC respirophasic diameter change with CVP in 73 patients and found >= 50% change in diameter predicted a CVP< 8 mmHg with 91% sensitivity (95% CI 71% to 99%) and 94% specificity (95% CI 84% to 99%). The positive predictive value was 87% (95% CI 66% to 97%), and the negative predictive value was 96% (95% CI 86% to 99%). Presumably the rather arbritrary CVP of 8 was chosen because of its importance as a target for goal directed therapy in sepsis guidelines. A more meaningful endpoint such as a fluid responsive cardiac output might be a more clinically relevant application of this technique, which had been demonstrated previously.

Emergency Department Bedside Ultrasonographic Measurement of the Caval Index for Noninvasive Determination of Low Central Venous Pressure
Ann Emerg Med. 2010 Mar;55(3):290-5