Intensively Ultrasonic An introduction to the clinical use of ultrasound

in the critical care environment.Dr. Daniel Rankmore - 2011

Talk Outline1. the physics2. the equipment3. novel clinical uses4. vascular access5. final words

the physics

Ultrasound Physics

Mechanical Electric Energy

Reflection / Refraction / Attenuation

Sound Wave Propagation (Wave)

Vibrating Particles (Medium)

Electric Mechanical Energy

Pulse Echo & Piezoelectrics

Basic PrinciplesReflection• The change in direction of a sound wave at the

interface of two mediums.

Refraction• The change in direction of a sound wave due to a

change in speed.

Absorption• Mechanical to heat energy.

Scatter• As surfaces are not uniform reflection/refraction

results in multiple directions.

Basic PrinciplesAcoustic Windows• Positioning of the probe over tissues

Echogenicity• Hyperechoeic – highly reflective• Aechoiec – no reflections

Acoustic Impedance• Density of tissue & frequency effect speed.

Acoustic Attenuation• The gradual loss of energy through a medium.

ArtifactsShadowing• Reduced penetration due to highly

reflective surfaces. Eg. Bone.

Acoustic Enhancement• Distal enhancement due to relatively

reduced attenuation.

Reverberation• Sound ‘bounces’ between two highly

reflective objects.

KnobologyPower• On/Off

Gain• Degree of echo amplification.

Depth• Focus of beam and displayed depth

Doppler• Doppler = Doppler• 2D = No Doppler

the equipment

The MachineSonosite M-Turbo Sonosite S-Series

which probe to use

Frequency

↑Frequency

↑Detail

Pattern

Special Purpose

The Probes

Linear10-5MHz 38mm

Phase Array5-1MHz 21mm

Linear13-6MHz 25mm

Curvy-linear5-2 Mhz 60mm

LinearFreq – 13-6MhzMax Depth – 6cm

Applications:Vascular Access, PneumothoraxNerve Blockade, Muscloskeletal

CurvedFreq – 5-2 MhzMax Depth – 30cm

Applications:FAST, Major vessel ?AAA, HemothoraxPleurocentesis, Peracentesis, BladderHepatobiliary, Obstetrics

PhasedFreq – 5-1 MhzMax Depth – 35cm

Applications:Echocardiography

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novel clinical uses

Cliff Reid’s Blog

http://resusme.em.extrememember.com/

extensions to FAST

PneumothoraxExtended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax: experience at a community based level I trauma center.

- Injury. 2011 May;42(5):511-4. Epub 2010 Feb 10.

- 204 Patients. Clinical examination was positive in 17 patients (true positive in 13/21, 62%; 4 were false positive and 8 were false negative), CXR was positive in 16 (true positive in 15/19, 79%; 1 false positive, 4 missed and 2 CXR not performed before chest tube) patients and EFAST was positive in 21 patients (20 were true positive [95.2%], 1 false positive and 1 false negative). In diagnosing pneumothorax EFAST has significantly higher sensitivity compared to the CXR (P=0.02).

hqmeded.org23 yo male stabbed with a cooking fork (6min)

(Link)Thoracic ultrasound for pneumothorax (Link)

Pelvic Fractures Ultrasonic detemination of pubic symphyseal widening in trauma:

FAST-PS. J Emerg Med 2011 May 40(5):528-33 STUDY OBJECTIVES: We hypothesized that an ultrasound image of the PS as

part of the FAST examination (FAST-PS) would be an accurate method to determine if pubic symphysis diastasis was present.

RESULTS: Twenty-three trauma patients were evaluated with both plain radiographs and US (11 PM, 12 ED). Four patients had radiographic PS widening (3 PM, 1 ED) and 19 patients had radiographically normal PS width; all were correctly identified with US. US measurements were compared with plain X-ray study by Bland-Altman plot. With one exception, US measurements were within 2 standard deviations of the radiographic measurements and, therefore, have excellent agreement. The only exception was a patient with pubic symphysis wider than the US probe.

CONCLUSION: Bedsid ultrasound examination may be able to identify pubic symphysis widening in trauma patients. This potentially could lead to faster application of a pelvic binder and tamponade of bleeding.

vascular

Art Line InsertionUltrasound-guided catheterization of the radial artery: a systematic review and meta-analysis of randomized controlled trials.

- Chest. 2011 Mar;139(3):524-9. Epub 2010 Aug 19.

- Conclusion: Four trials with a total of 311 subjects were included in the review, with 152 subjects included in the palpation group and 159 in the ultrasound-guided group. Compared with the palpation method, ultrasound guidance for arterial catheterization was associated with a 71% improvement in the likelihood of first-attempt success (relative risk, 1.71; 95% CI, 1.25-2.32).

airway

Peadiatric ETT SizePrediction of pediatric endotracheal tube size by ultrasonography.- Acta Anaesthesiol Scand. 2011

Apr;55(4):422-8. doi: 10.1111/j.1399-6576.2010.02372.x. Epub 2011 Feb 2.

- Conclusion: Measuring subglottic airway diameter with ultrasonography facilitates the selection of appropriately sized ETTs in pediatric patients. This selection method better predicted optimal outer ETT diameter than standard age- and height-based formulas.

brains

Pre-hospital Transcranial DopplerPre-hospital transcranial Doppler in severe traumatic brain injury: a pilot study.

- Acta Anaesthesiol Scand. 2011 Apr;55(4):422-8. doi: 10.1111/j.1399-6576.2010.02372.x. Epub 2011 Feb 2.

- 18 patients. Matched GCS/MAP. 9 abnormal. Link with pupil changes and mortality.

- Conclusion: Our preliminary study suggests that TCD could be used in pre-hospital care to detect patients whose cerebral perfusion may be impaired

Post CrainectomyUse of ultrasonography in hemicraniectomized patients: a report of two cases.

- Intensive Care Med. 2010 Jun;36(6):1091-2.

- Zampieri and colleagues from Brazil report the use of brain ultrasound in two ICU patients who had had hemicraniectomies. ‘using the hemicraniectomy as an insonation window could be useful as a noninvasive triage tool and reduce the need for patient transport to the imaging center.’

Optic NerveUltrasound measurement of optic nerve sheath diameter in patients with a clinical suspicion of raised intracranial pressure.

- Emerg Med J. 2011 Aug;28(8):679-81. Epub 2010 Aug 15.

- To assess if ultrasound measurement of the optic nerve sheath diameter (ONSD) can accurately predict the presence of raised intracranial pressure (ICP). 26 patients.  For any acute intracranial abnormality the value of ONSD was 100% specific (95% CI 76% to 100%) and 60% sensitive (95% CI 27% to 86%). 

vascular accessIntroduction…

Transverse

Keeps other structures in view

Easiest to find vessel

LongitudinalCan be better for deeper

structuresAllows visualisation of

needle & wire advancing within the vessel

Which is the vein?1. Know the anatomy

Which is the vein?2. Static views on Ultrasound

1. Arteries have thicker walls

2. Arteries are rounder

Which is the vein?3. Dynamic views on Ultrasound

1. Compressibility Collapse vs. Winking

2. Doppler BART – Blue Away Red

Towards Flow – Pulsatile vs.

Continuous

vascular ultrasoundhow I use ultrasound for vascular access…

PreparationEquipment

Sonosite S Series – Linear 25mm – Gel/ Sock/ Opsite Tourniquet Gown/ Gloves Skin Prep – Chlorhex Local – 2-3ml 1% Lignocaine Line (IVC/ CVC/ PICC/ Vascath/ Art line) Flush – 20ml 0.9% N-Saline Dressing (Opsite/ Statlock/ Suture)

StaffPatient

sßcan the vesselConfirms the direction of

the vesselReveals anatomical

variations (and other structures)

Gives insight into patency (ie. thrombus)

identify the targetPrep the skinHold the probe lowOrientate the probeAdjust depth and gainVessel centralLocal anesthetic

advance on target Pencil grip @ 30-45 degrees Advance needle ‘I can’t see the needle!’

Stay midline Bright echogenic circle Shadow Do the jiggle Tenting Move the probe

Flashback Check the wire

hqmeded.orgUltrasound Guided Intravenous Peripheral

Placement (7min) - LinkUltrasound Guidance for Central Venous Catheter -

Link2 yo with DKA - Link

some final words…

think in three dimensions

Simplify the angles

Prior Preparation Prevents Piss Poor Performance

1. Optimise position (you & the patient)

2. Have an assistant (& talk to them)

3. Get the right equipment

4. Understand the equipment

5. Understand the anatomy

6. Know the complications (& what to do)

7. Practice

ReferencesMa JO, Mateer JR. Emergency Ultrasound. McGraw

Hill. 2003.Sangers RC, Winter R. Clinical Sonography: A

practical guide. Fourth Edition. Lippincott Williams & Wilkins. 2007.

WikipediaGoogle Images