Introduction to procedural ultrasound

Introduction toProcedural Ultrasound

Richard Hay

Procedural UltrasoundAim

Provide an overview of uses and techniquesWhyWhenHow

Advantages and disadvantagesBasic tips

Ultrasound Guided Procedures

Vascular accessCentral, Peripheral, Arterial

AspirationThoracocentesisParacentesisPericardiocentesisJoint aspirationSupra-pubic aspiration

Foreign body detection and removalNerve blocks

Why use Ultrasound for Procedures

Allows visualisation of anatomy prior to an invasive procedureDetect abnormal anatomyIdentify interposed structures

Better localisation of targetPrevent invasive procedure being attempted when

not indicated

Basic Ultrasound Knowledge for Learning Procedural Ultrasound

Choice of probeField of viewFrequency

The ultrasound beamSlice thickness and beam width

The ultrasound imageFluid is blackSoft tissues are greyAir and metal hyperechoic and cause

reverberationBone and stones cause shadowing

Basic Ultrasound Knowledge for Learning Procedural Ultrasound

The ultrasound imageWhat the needle looks like

Transverse Comet tail artifact Beam width artifact

Longitudinal Reverberation artifact

Size and depth measurement

Procedural TechniquesMethods

Indirect approachMark the spot

Direct approachReal time

Transverse (out of plane) Longitudinal (in plane)

Procedural TechniquesIndirect approach

Best forLarge static targets not too far away

Ascites Pleural effusion

Small superficial targets

Indirect approachTechnique

Locate target with US and identify best site for skin entryMeasure size and depthObserve for changes with respiration

Note midpoint and axial direction of transducerRemove transducer and mark skinPerform procedure

Indirect approachAdvantages

QuickEasy

Less coordination requiredLess experience required

No requirement for sterile transducer cover

Indirect approachDisadvantages

Not under direct visionNot good for small distant targetsPatient must not move between marking and

procedure

Procedural TechniquesDirect method

Needle is advanced under direct US visionTwo different approaches

Transverse Target in transverse section in center of image Needle approach is perpendicular to the scan plane

Transverse Approach

Procedural TechniquesDirect method

Needle is advanced under direct US visionTwo different approaches

Transverse Target in transverse section in center of image Needle approach is perpendicular to the scan plane

Longitudinal Target in longitudinal section across image Needle approach is along the scan plane

Longitudinal Approach

Transverse approachIndications

Two or more parallel structures that appear similar when seen in longitudinal section

Not enough room for longitudinal approach

Transverse approachTechnique

Target in center of US imageNote depth of target

Needle in line with midpoint of transducer a few centimeters away

Slowly advance needle and watch tip by:Fanning transducer toward needle and back to

targetJiggle needle to move soft tissuesBeware not to advance needle beyond the scan

plane

Transverse approachAdvantages

Can see and avoid structures either side of the target

Can use a steeper angle of approachLess space at anatomical site required

Transverse approachDisadvantages

Needle harder to see in cross sectionOften rely on just the tissue movementDepth of needle difficult to assessSterile transducer cover required

Longitudinal approachIndications

Small targets requiring precise needle placementPeripheral vascular accessNerve blocksBiopsy

Longitudinal approachTechnique

Identify target in transverse then go to longitudinal viewNote depth of targetConsider needle trajectory and desired target

entry pointNeedle in line with midpoint of long axis of

transducerSlowly advance needle under direct vision

Angle corrections required to keep needle in line with scan plane

Longitudinal approachAdvantages

Better localisation of needleVisually striking

Watch needle all the way to the targetCan see structures deep and superficial to the target

Longitudinal approachDisadvantages

Difficult to line up three objectsUS beam, needle, targetRequires more

Coordination Practice

Cannot see structures either side of targetTwo adjacent parallel structures can look similar

Easy to slip from one to the other

Longitudinal approachDisadvantages

Difficult to line up three objectsUS beam, needle, targetRequires more

Coordination Practice

Cannot see structures either side of targetTwo adjacent parallel structures can look similar

Easy to slip from one to the otherMore space required at anatomical site

Shallow approach angleTransducer longitudinal

Procedural UltrasoundGeneral Comments

PositioningEnsure patient and operator comfortable

Line upPatient, target and transducer, screen

Watch the screen not your hands

Procedural UltrasoundGeneral Comments

PositioningEnsure patient and operator comfortable

Line upPatient, target and transducer, screen

Watch the screen not your handsUse the transducer to find the needleMake sure local anaesthetic is free of air

Procedural UltrasoundGeneral Comments

Vein vs arteryVeins

Thin walls, compress, respiratory variation, valsalva, triple pulsation

Arteries Round, thicker wall, single pulsation

Procedural UltrasoundGeneral Comments

Vein vs arteryVeins

Thin walls, compress, respiratory variation, valsalva, triple pulsation

Arteries Round, thicker wall, single pulsation

NervesView in transverseNeedle along scan plane

Procedural UltrasoundSummary

Ultrasound is useful for many proceduresImproved safety and successBasic ultrasound knowledge requiredA number of different techniques

Suit different circumstancesLearned skill

Practice