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Review Article

eedle Visualization in Ultrasound-Guidedegional Anesthesia: Challenges and Solutions

i Jinn Chin, M.B.B.S., F.A.N.Z.C.A., M. Med., F.R.C.P.C.,nahi Perlas, M.D., F.R.C.P.C., Vincent W. S. Chan, M.D., F.R.C.P.C., andichard Brull, M.D., F.R.C.P.C.

Needle visualization is important for safe and successful ultrasound-guided peripheral nerve block. However,accurate and consistent visualization of the needle tip can be difficult to achieve. This review article describesmany of the challenges affecting needle visualization, summarizes the relevant literature on ultrasound imagingof needles, and offers practical strategies for improving needle tip visibility. Finally, future directions for researchand development are suggested. Reg Anesth Pain Med 2008;33:532-544.

Key Words: Needle visualization, Peripheral nerve block, Regional anesthesia, Ultrasound.

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h e foremost advantage of ultrasound (US)-guided peripheral nerve block (PNB) is the ability

o visualize both anatomical structures of interest asell as the advancing block needle. Ideally, US guid-

nce should translate into greater efficacy, by ensur-ng accurate deposition and spread of local anestheticround the target nerve; and improved safety, byvoiding unintentional intraneural and intravascularuncture and injection. While the identification ofelevant anatomical structures can become relativelyasy with practice and development of a trained eye,eeping the needle tip in view as the needle is ad-anced toward the target is much more difficult.1

ailing to do so was the most common error observedn residents learning to perform US-guided PNB.2 Per-istent failure to visualize the needle tip was docu-ented even after performing more than 100 US-

uided PNB, suggesting that experienced practitionersan also face difficulty.2 Needle advancement and/orocal anesthetic injection without adequate needle tipisualization may result in unintentional vascular,eural, or visceral injury.

From the Department of Anesthesia and Pain Management,oronto Western Hospital, University Health Network, Toronto,ntario, Canada.Accepted for publication June 5, 2008.Reprint requests: Richard Brull, M.D., F.R.C.P.C., Department

f Anesthesia, Toronto Western Hospital, University Health Net-ork, 399 Bathurst Street, Toronto M5T 2S8, Ontario, Canada.-mail: [email protected]© 2008 by the American Society of Regional Anesthesia and

ain Medicine.

r1098-7339/08/3306-0001$34.00/0doi:10.1016/j.rapm.2008.06.002

32 Regional Anesthesia and Pain Medicine, Vol 33, No

This review article describes many of the chal-enges in needle visualization, summarizes the rel-vant literature on ultrasound imaging of needles,nd offers practical strategies for improving needleip visibility.

ethods

We performed a literature search of the MEDLINEatabase from January 1960 to January 2008 us-

ng the search terms “ultrasound” and “needle” andimited the search by excluding terms related tonatomical structures or techniques that we consid-red irrelevant to peripheral nerve block. Thesencluded “endoscopic,” “endobronchial,” “brain,”lung,” “pancreas,” “kidney,” “ovary,” “prostate,”nd “fetus.” The search was limited to articles in thenglish language. This search strategy captured,427 articles, of which we eliminated 4,358 basedn their titles. We reviewed the remaining abstractsnd eliminated a further 29 articles due to lack ofelevance. We reviewed the full text of the remain-ng 40 articles for relevance to our topic. We iden-ified another 11 articles of interest from the refer-nce lists of the reviewed articles. The selectedrticles were graded according to their level of evi-ence as recommended by the Centre for Evidence-ased Medicine (Appendix 1).

esults and Discussion

We identified 34 articles of direct relevance, in-luding letters and case reports. These are summa-
ized in Table 1 and discussed below. Where appro-
6 (November–December), 2008: pp 532–544

mailto:[email protected]

Table 1. Summary of Needle Visualization Strategies in Ultrasound-Guided Peripheral Nerve Block

ReferenceLevel of

Evidence Study Design/Subject(s) Study Interventions Outcomes Key Results

Needle guidesHatada et al.3 3b Retrospective case-control study.

Patients undergoing ultrasound-guided fine needle aspirationbiopsy of the breast.

Mechanical fixed needle guidevs. freehand technique.

Accuracy ofpathologicaldiagnosis.

1. Greater sensitivity of freehand technique for tumors�3 cm in diameter.

Phal et al.4 5 Comparative laboratory study.Gelatin liver phantom.

Mechanical fixed needle guidevs. freehand technique.

1. Procedure time.2. Sample quality of

biopsy specimen.

1. Shorter time to perform biopsy using a needleguide, especially for less experienced operators.

2. No difference in quality of biopsies.Tsui5 5 Descriptive feasibility study.

Water bath model.Optical needle guide (laser-

sighting apparatus for inplane needle-beamalignment).

Not applicable. 1. Feasible in the laboratory model.2. No data on clinical use.

Echogenic needle designPerrella et al.6 1b Controlled clinical trial (both

interventions in each patient).Patients undergoing tissue

biopsies or aspiration of fluidcollections or percutaneousnephrostomy.

Biosponder 20G to 22Gneedles vs. standard Turner20G biopsy needle.

Subjectiveassessment ofNTV.

1. Poor NTV with standard biopsy needle in allpatients.

2. Excellent NTV of Biosponder needle in 16 patients.There was technical equipment failure in the other4 patients.

Bergin et al.7 1b Randomized controlled trial.Patients undergoing tissue

biopsy.

Polymer coated needle vs.uncoated 20G needle.

Subjectiveassessment ofNTV and NSV.

1. NSV moderate to good in 79% coated vs. 28%uncoated.

2. NTV moderate to good in 100% coated vs. 84%uncoated.

3. No correlation between lesion depth and NTV.Jandzinski et al.8 1b Randomized controlled trial.

Patients undergoing thyroid orliver biopsy

Polymer coated vs. Tefloncoated vs. etched tip vs.untreated 22G needle.


1. Best NTV with polymer coated needle for boththyroid and liver biopsy.

2. Superior NTV with untreated needle vs. Tefloncoated and etched tip needles for liver biopsy, butnot thyroid biopsy.

Gottlieb et al.9 5 Comparative laboratory study.Rabbits undergoing kidney

biopsy.

Polymer coated vs. uncoated22G spinal needles.

Subjectiveassessment ofNSV.

1. Superior NSV with coated vs. uncoated needle.2. Deterioration in visibility of coated needle with

repeated use.Culp et al.10 5 Comparative laboratory study.

Gelatin liver phantom.Polymer coated needle vs.

dimpled distal shaft vs.uncoated 21G needle.

Objective andsubjectiveassessments ofNV.

1. Superior NV with coated and/or dimpled needles.2. NV decreases with increasing needle-beam angle.

Threshold for good visibility is 10° (coated and/ordimpled needles) vs. 40° (standard needle).

Hopkins and Bradley11 5 Comparative laboratory study.Sponge-based liver phantom.

Teflon coated and/orechogenic tip vs. untreated18G and 22G needles.

Subjectiveassessment ofNV.

1. Superior NV with echogenic 20G needles vs.untreated needles at 10° needle-beam angle.

2. No difference in NV at 60° needle-beam angle orfor 18G needles.

Needle

Tip

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Table 1. (Continued)

ReferenceLevel of


Nichols et al.12 5 Comparative laboratory study.Liquid-based liver phantom.

Polymer coated vs. dimpleddistal shaft vs. prototypedimpled needle vs.roughened tip vs.nonenhanced plastic coatedneedle.

Objectiveassessment ofNV.

1. All needles highly visible at 90° needle-beamangle.

2. Nonenhanced and roughened tip needles poorlyvisible at needle-beam angle �60°.

3. Good NV with polymer coated needle at needle-beam angles �45°.

4. Best NV with dimpled distal shaft needles at allneedle-beam angles �15°.

Deam et al.13 5 Comparative laboratory study.Synthetic gel phantom.

Textured tip vs. standard 22Gspinal needle vs. 18GTuohy needle vs. 22Ginsulated needle.


1. Superior NV with textured needle vs. all others2. NV of textured needle unaffected by angle of

insertion.

Needle manipulationBondestam and Kreula14 5 Descriptive laboratory study.

Water bath model.Needles of varying diameter

10G to 25G, and bevelangles 10° to 70°.

Various insertion angles andbevel orientations used.

Objectiveassessment ofNTV.

1. Superior NTV at larger needle-beam angles.2. Superior NTV with larger needle diameter.3. Superior NTV with bevel opening oriented 0° or

180° to beam vs. 90° or 270°.4. No difference in NTV with bevel angle.

Bisceglia et al.15 5 Comparative laboratory study.Blood agar phantom.

The “pump maneuver” –pumping the stylet up anddown in the needle 7 times –applied to a 21G stylettedbiopsy needle.


1. NTV consistently increased by pump maneuver.2. Increase in NTV was transient, lasting 5 to 10

minutes, and attributed to microbubble formation.

Bradley16 5 Descriptive laboratory study.Sponge-based liver phantom.

18G biopsy needle inserted atvarious insertion angles andneedle-transducerdistances.


1. Needle-transducer distance of 2 cm to 3 cm and aneedle-beam angle of 55° to 60° recommended toachieve good NV and a short needle track length.

Schafhalter-Zoppoth et al.17 5 Descriptive laboratory study.Gelatin liver phantom.

Nonechogenic needles ofvarying tip bevel designsand diameters (18G-22G).

Objective andsubjectiveassessments ofNTV.

1. Best NTV with Hustead tip, followed by Quinckeand Tuohy tip.

2. Superior NTV with 17G to 18G vs. 20G to 22Gneedles.

3. Superior NTV at needle-beam angle �60° with inplane approach.

4. Superior NTV at needle-beam angle �30° with outof plane approach.

Maecken et al.18 5 Descriptive laboratory study.Water bath model and pork

tissue phantom.

Nonechogenic block needleswith varying diameters(19G-22G).


1. Acceptable NTV for all needles at 0° to 45°needle-beam angle in the water bath model.

2. Acceptable NTV using the in plane approach for allneedles in tissue phantom at 0° needle-beamangle but only for 3 needles at 45° needle-beamangle.

3. Acceptable NTV using the out of plane approach in11 out of 12 needles in tissue phantom at 45°needle-beam angle.

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Table 1. (Continued)

ReferenceLevel of


Ultrasound imaging technologyMesurolle et al.19 1b Controlled clinical trial.

Patients undergoing breastbiopsy.

Tissue harmonic imaging vs.frequency compoundimaging vs. conventionalB-mode imaging.


1. Inferior NV with tissue harmonic imaging vs.conventional imaging.

2. Equivalent NV with frequency compound imagingvs. conventional imaging.

Cohnen et al.20 2b Comparative laboratory andclinical trial.

Cadaveric liver phantom and 10cirrhotic patients undergoingtransjugular intrahepaticportosystemic stent-shuntinsertion.

Spatial compound imaging vs.conventional B-modeimaging.

Objective andsubjectiveassessments ofNV.

1. Superior NV with spatial compound imaging atsmaller needle-beam angles �60°.

Saleh et al.21 5 Comparative laboratory study.Cadaveric muscle phantom.

Spatial compound imaging vs.conventional B-modeimaging.

Objectiveassessment ofNV.

1. Good NV with all imaging modes at large needle-beam angles (78°-90°).

2. Reduced NV at smaller needle-beam angles(65°-72°), but NV is improved by spatial compoundimaging.

Karstrup et al.22 5 Comparative laboratory study.Gel liver phantom.

Automatic tissue optimizingvs. coded excitation vs.coded harmonic imaging vs.conventional B-modeimaging.


1. Best NTV with automatic tissue optimizing andcoded excitation settings.

2. Superior NTV with conventional imaging thancoded harmonic imaging.

Baker et al.23 2b Controlled clinical trial.Patients undergoing breast

biopsy.

Active beam steering toincrease needle-beam angletoward 90° vs. no beamsteering.

Subjectiveassessment ofNSV and NTV.

1. Excellent NTV with beam steering in all cases(needle-beam angle of incidence increased by18° on average).

2. NTV and NSV improved by beam steering in 6 outof 8 cases from “not identified/barely perceptible” to“excellent perceptibility.”

Color DopplerFeld et al.24 1b Controlled clinical trial (both


biopsy.

ColorMark vibrating needlesystem vs. conventional B-mode ultrasound.


1. Needle tip visualized in 92% of procedures withColorMark system vs. 77% of procedures withconventional imaging.

2. Superior NTV with ColorMark system.Jones et al.25 1b Controlled clinical trial (both


biopsy.

ColorMark vibrating needlesystem vs. conventional B-mode ultrasound.

Subjectiveassessment ofNTV and NSV.

1. NTV and NSV improved by ColorMark system in58% of superficial (�3 cm depth) biopsies, but onlyin 13% of deep biopsies.

Armstrong et al.26 1b Descriptive laboratory andclinical study.

Urethane phantom and patientsundergoing electivepericardiocentesis.

ColorMark vibrating needlesystem.

Accuracy oflocalization ofneedle tip in thephantom.

Successfulvisualization ofneedle tip inpatients.

1. ColorMark system permitted accurate localizationof needle tip in the phantom.

2. The needle tip was visualized in 72% of patients.

NOTE: ColorMark manufactured by EchoCath Inc., Princeton, NJ; and Biosponder manufactured by Advanced Technology Laboratories, Bothell, WA.Abbreviations: G, gauge; NSV, needle shaft visibility; NTV, needle tip visibility; NV, needle visibility in general (tip/shaft not specified).

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536 Regional Anesthesia and Pain Medicine Vol. 33 No. 6 November–December 2008

riate, we have supplemented the available evi-ence from the literature with recommendationsased on our experience with US-guided PNB athe Toronto Western Hospital using conventional-dimensional US and standard (nonechogenic)lock needles.

eedle-Beam Alignment: In Planeeedle Approach

hallenges/Background

There are 2 methods of orienting the needle rel-tive to the US beam in US-guided PNB: the inlane and out of plane approaches.27 In the in planeeedle approach, the needle is inserted in the samelane as the US beam and is visible as a brightyperechoic line. Needle-beam alignment is criticalo visualize the shaft (i.e., profile) of the needle inhe in plane approach. The freehand technique re-uires bimanual coordination in 3 dimensionshilst looking away at a 2-dimensional image on

he US screen. This, coupled with the narrow widthf the US beam (as little as 1 mm at the focal zonef high frequency transducers), can make it difficulto maintain needle-beam alignment as the needle isdvanced.2

trategies

Mechanical needle guides. Needle-beam align-ent can be facilitated by the use of a mechanicaleedle guide attached to the transducer. Whilehere are no published descriptions of mechanicaleedle guides in US-guided PNB, they have beenompared with the freehand technique in 2 studiesf US-guided needle biopsy.3,4 Mechanical guidesignificantly reduced biopsy procedure time com-ared with a freehand technique, especially for lessxperienced operators.4 However the mean differ-nce was only 20 seconds and this may not belinically significant. Interestingly, the use of needleuides did not improve biopsy quality;4 in fact di-gnostic accuracy was better with the freehandechnique for biopsy of smaller targets (�3 cm iniameter).3 This suggests that the precision of nee-le tip placement afforded by mechanical needleuides may be inadequate for US-guided PNB, asarget nerves are often 1 cm or less in diameter.

Optical needle guides. Tsui5 described a la-er-sighting apparatus that facilitates in plane nee-le-beam alignment and that can be assembledrom inexpensive off-the-shelf components. Thisptical guide provides a clear visual indication ofrecise needle-beam alignment, and may proveseful in teaching and developing bimanual coor-
ination in novices. However, a portion of the nee- u
le shaft has to protrude from the skin surface at allimes to allow alignment with the laser. This mayequire the use of longer block needles that can beore difficult to manipulate. As the author pointed

ut, the method is also unsuitable for continuousatheter techniques that require the probe (andaser) to be encased in a sterile sleeve.

ecommendations

The utility of mechanical needle guides in inter-entional ultrasound is controversial.28-30 Whileeedle guides may minimize challenges with nee-le-beam-alignment in the in plane approach andherefore be helpful for the less experienced oper-tor,4,28.30 they also restrict needle redirection.29

djustable guides have been described in order tovercome this limitation,31-33 but redirection stillequires complete withdrawal and reinsertion ofhe needle. The demands of US-guided PNB are alsoifferent from that of US-guided biopsy. Given thatne adjustments in needle trajectory and depth areften required to achieve adequate local anestheticpread around the target nerve, our preference isor a freehand technique. Nevertheless, the use of

echanical needle guides in US-guided PNB shoulde investigated.It is our experience that in plane needle-beam

lignment can be achieved by careful manipulationf transducer and needle using the freehand tech-ique. Resting the medial edge and/or fingers of theperator’s transducer hand on the patient and ap-lying firm pressure downwards with the trans-ucer will minimize slipping on gel-covered skinFig 1). Firm pressure has the added advantage ofompressing adjacent veins and reducing distanceo the target. Operator fatigue also contributes tonintentional transducer movement and may be

ig 1. The operator’s transducer hand should be restingn the patient for support as shown in (A), to preventnintentional slipping of the transducer. The other handosition illustrated in (B) will predispose to fatigue and
nintentional transducer movement.

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Needle Tip Visualization Techniques • Chin et al. 537

educed by careful attention to ergonomics, such asaising the bed to an appropriate height to allow anrect posture during performance of the block. Ifhe needle tip becomes poorly visible at any time, ithould not be advanced further. The first step toroubleshooting a “disappearing” needle is to visu-lly inspect needle and transducer position and ex-lude gross misalignment. The transducer shouldhen be moved in a slow and controlled manner,sing the 3 basic (sliding, tilting, and rotating)ovements described by Marhofer and Chan,34 un-

il the needle shaft and tip have been brought backnto view. We do not recommend moving theransducer and needle at the same time when try-ng to align them, as this makes the task moreifficult and increases the risk of unintentional nee-le trauma.

eedle-Beam Alignment: Out of Planeeedle Approach


In the out of plane needle approach, the longitu-inal axis of the needle is inserted in a plane per-endicular to that of the US beam.27 Visualizing theeedle tip in this approach can be difficult, as onlycross-sectional area of the needle is imaged. In a

el phantom, the tip appears as a bright hyper-choic dot, often with an anechoic acoustic shadowmmediately below it (Figs 2A and 2B). It is more

ig 2. With the needle in-erted at a 45° angle in theut of plane approach, it iselatively easy to confusehe shaft, indicated by thepper arrow in (A), for theip, indicated by the arrown (B), as the 2 images areimilar; both being echo-enic dots. (A) The acous-ic shadow (lower arrow)ast by the shaft is morerominent, and may be alue to distinguish it fromhe tip. (C) Inserting theeedle at a steeper anglend closer to the trans-ucer (tip indicated by ar-ow) reduces the length ofeedle shaft that can be

maged, and makes this er-or less likely.

ifficult to identify the needle tip in clinical practiceue to the lack of contrast between it and theurrounding echogenic tissue. The needle shaft maylso be mistaken for the tip as both have a similarppearance in cross-section.

trategies

A “walkdown” technique has been suggested toid out of plane needle tip visualization.35 This con-ists of inserting the needle at a distance from theransducer equivalent to the depth of the target,uch that the tip will eventually intersect the USeam and target at a trajectory angle of approxi-ately 45°. The initial insertion angle should, how-

ver, be shallow so as to facilitate detection of theeedle tip. The needle is then incrementally angled,ith the tip visualized at progressively greaterepths until the target is reached. Potential disad-antages of this technique include the need forultiple needle passes and a long needle track to

each deeper targets, both of which may increaseatient discomfort.

ecommendations

There are no clinical data to support any partic-lar technique of out of plane needle insertion. It isur preference to insert the needle close to theransducer (within 1 cm), irrespective of targetepth, and at a steeper (approximately 75°) angle to

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he skin (Fig 2C). Visibility of the needle tip haseen shown to be better at smaller rather thanarger needle-beam angles in the out of plane ap-roach.17,18 We also rely heavily on surrogatearkers to confirm needle tip location (see below).

chogenic Needle Design


The echogenicity of commonly used block nee-les under clinical conditions was investigated byaecken and colleagues.18 The authors found the

isibility of 9 of 12 needles to be unacceptable whennserted at a 45° angle in an animal tissue phan-om.18 In contrast, all needles had excellent visibil-ty scores in a water bath regardless of insertionngle.18

These findings can be explained in terms ofcoustic impedance, which is a measure of the de-ree to which sound waves are transmitted throughparticular medium. At the interface between me-ia with different acoustic impedances, some of theound waves are reflected whilst the others areransmitted. The amount of reflection that occurs isroportional to the difference in acoustic imped-nce between the media. Hence, metal needleshigh impedance) are clearly visible as bright ob-ects against the dark uniform background providedy gel phantoms and water baths (low impedance).his often leads novices who are training on gelhantoms to erroneously conclude that needle vi-ualization is easily achieved. Soft tissue, however,s a heterogeneous mix of fluid, fat, muscle, andonnective tissue, each with different acoustic im-edances. Reflection of sound waves occurs at eachf these tissue interfaces, giving soft tissue a speck-ed echogenic appearance. The reduced visual con-rast between needle and the background of softissue makes it difficult to distinguish between thewo. The multiple acoustic interfaces also cause re-raction (scatter) and attenuation of returning ech-es,36 further reducing needle visibility.

trategies

Physical enhancement of needle echogeni-ity. The problem of poor needle visibility haseen addressed by the development of echogeniceedles. Echogenic needles are engineered to in-rease the reflection of US waves back towards theransducer. The most echogenic needle designs in-lude a polymer coating that traps microbubblesEcho-Coat, STS Biopolymers, Henrietta, NY), and aimpled distal shaft (Echotip, Cook, Bloomington,N). Their superior needle tip and shaft visibility has
een demonstrated in both laboratory9-13 and clin- i
cal settings,7,8 and is especially significant at smalleedle-beam angles.9-13 However only 1 study toate involved needles designed for regional anes-hesia;13 all others involved needles designed forltrasound-guided tissue biopsy.Electronic enhancement of needle echoge-

icity. A unique innovation in needle design ishe Biosponder biopsy needle (Advanced Technol-gy Laboratories, Bothell, WA), which has a styletith a piezoelectric polymer sensor at the tip. USaves striking the sensor generate electrical im-ulses that are transmitted along the stylet andable attached to the US machine. The needle tip ishen displayed as a bright flashing marker on theS image. In a small study of 20 patients undergo-

ng biopsy or fluid drainage, the Biosponder systemreatly improved needle tip visibility comparedith a standard biopsy needle.6 The authors con-

luded that the tip of the Biosponder needle coulde consistently identified regardless of body habi-us, tissue echogenicity, and depth or size of thearget. However, despite the obvious potential, nother reports on the use of the Biosponder systemave been published.

ecommendations

Echogenic block needles are likely to becomeore widely available in the future, but it is clear

rom the radiological literature that some designserform better than others. Clinical trials will beeeded to establish the individual efficacy of theseeedles before they can be recommended for use.

eedle Manipulation


The visibility of nonechogenic needles may benhanced by manipulating the needle in severalays, including altering the needle-beam angle,rienting the needle bevel appropriately, and prim-ng the shaft.14-18

trategies

Needle-beam angle. The angle at which theeedle shaft and US beam intersect (needle-beamngle) greatly affects needle visibility (Fig 3). Themooth metallic surface of a standard needle is apecular (mirror-like) reflector of US waves, hencegreater number of echoes will return to the trans-ucer as the needle-beam angle approaches 90°.36

s a result, in plane needle tip and shaft visibility isetter at larger needle-beam angles;10,13,14,16,17 theptimal angle appears to be �55°.10,16,17 Interest-

ngly, out of plane needle tip visibility is better at

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maller needle-beam angles (�30°); however, theeason for this is not clear.17,18

Needle bevel orientation. Needle tip visibil-ty is better when the bevel opening is orientedither to directly face the US beam (0°) or to face80° away from the beam.11,14

Priming the needle. There appears to be littleifference in visibility between needles primed withither water or air.17 Inserting a guidewire will sig-ificantly increase needle shaft visibility.17 How-ver, this effect is lost if very tightly-fitting guide-ires are used, as there is no longer an acoustic

nterface between the shaft and guidewire.17 Forhe same reason, stylet and hollow needles haveimilar visibility.17 However if a stylet needle issed, pumping the stylet up and down several timesithin the shaft may transiently increase needle

chogenicity.15 The effect of this “pump maneuver”s attributed to the formation of microbubbles abouthe needle tip and shaft.

Using needles of larger diameter. Bettereedle tip visibility can be obtained with largeriameter needles,14,17 but at the expense of in-reased tissue trauma and patient discomfort.

ecommendations

A needle-beam angle close to 90° offers the besteedle visibility when using an in plane needlepproach (Fig 3).10,13,14,17 However maintaining aarge needle-beam angle is not always feasible, es-ecially when targeting deeper nerves, e.g., the in-raclavicular brachial plexus. In these situations, aheel-in” maneuver may be helpful. This involvesressing one end (the “heel”) of the transducerore deeply into the patient than the other end

the “toe), thus increasing the needle-beam angleFig 4). It is our routine practice to prime needles

ig 3. (A) A 22-gauge needle is initially inserted in ahallow trajectory toward the axillary brachial plexus,nd both the shaft and tip are clearly visible. The needle-eam angle (indicated by dashed lines) is almost 90° andeflection back to the transducer is maximal. (B) As theeedle trajectory increases, and the needle-beam angleecomes smaller, the shaft becomes less echogenic, andhe tip is no longer clearly visible.

ith fluid (local anesthetic or dextrose 5%) to avoid s

bscuration of the image by the echogenic artifacthat occurs with injection of air. We continue to use2-gauge block needles for single shot PNB as wend in most cases the increase in visibility affordedy larger needles does not warrant the correspond-ng increase in patient discomfort.

ltrasound Imaging Technology


As ultrasound technology has advanced, new im-ging modes have been developed; these includepatial compound imaging, frequency compoundmaging, tissue harmonic imaging, beam steering,nd 3-dimensional US. These modes are designed tomprove image quality and increase the amount ofnformation that can be obtained from an US ex-mination; however, their effect on needle visibilityaries.

trategies

Compound and harmonic imaging. Com-ound imaging involves acquiring multiple imagesf the same object and combining them into a singlemage; the images may be acquired from differentngles in the same plane (spatial compound imag-ng) or acquired at different frequencies (frequencyompound imaging). Tissue harmonic imagingorms an image using echoes at twice the emittedrequency; this higher frequency harmonic signal ispontaneously generated by propagation throughissues.

When compared with conventional B-mode im-ging, spatial compound imaging consistently im-roves needle visibility20,21 while tissue harmonicmaging worsens it.19,22 Frequency compound im-ging does not appear to have a significant effect oneedle visibility.19

Electronic beam steering. Electronic beamteering is a technology that allows the US beam toe tilted relative to the transducer, thus increasinghe needle-beam angle of incidence toward 90°.his greatly improved needle tip and shaft visibilityn a small study of 7 patients undergoing breastiopsy.23

Three-dimensional ultrasound. Preliminaryase reports on the use of 3-dimensional US touide PNB suggest that a third dimension (i.e.,lane view) may be able to give additional informa-ion about needle and catheter location.37,38 How-ver, the present technology does not appear tonhance needle visibility per se, and all of the chal-enges associated with poor needle echogenicityikely still apply. Additional limitations of 3-dimen-
ional US currently include a slower frame rate and

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bulkier transducer,38 both of which can makeeedle-beam alignment more difficult.Color Doppler detection of the needle tip.ovement of an object within an US beam pro-

uces a Doppler shift in the frequency of the re-ected echoes.39 The color Doppler functionvailable on most modern US machines modulateshis frequency shift into a color signal, and is com-only used to detect blood flow. It may also besed to localize a moving needle tip against atationary background. The ColorMark deviceEchoCath Inc, Princeton, NJ) clips onto the needlehaft and induces minute vibrations at the needle
ip (maximum amplitude 15 �m, which is imper- n
eptible to touch), which are sufficient to generatesignal with color Doppler. The ColorMark device

ignificantly improved needle tip visibility in pa-ients undergoing tissue biopsy and pericardiocen-esis.24-26 A prototype device based on similarrinciples has recently been described for re-ional anesthesia using an 18-gauge Tuohy blockeedle and 20-gauge stylet catheter in a cadaverodel.40 Other methods to generate movement at

he needle tip have been described, including anscillating air column,41 manual motion of theeedle,42,43 and vibration induced by rotation of aent stylet within the needle;44 however, there is

Fig 4. A 22-gauge needle isinserted in a steep trajectory(small needle-beam angle)toward the infraclavicularbrachial plexus. (A) Theneedle shaft (small arrows)and tip (large arrow) arepoorly visible. (B) The nee-dle-beam angle is effectivelyincreased by applying a“heel-in” maneuver to theposition illustrated in (C),and pressing the caudadend of the transducer moredeeply into the patient asshown in (D), thus increas-ing the echogenicity of theneedle shaft (small arrows),and tip (large arrow), asshown in (B). AA, axillaryartery; PMM, pectoralis ma-jor muscle.

o evidence from comparative studies to support

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he efficacy of these methods in improving needleisibility.

ecommendations

Spatial compound imaging is available on most ofhe newer compact US machines and should besed whenever possible.20,21 Harmonic imagingay improve the visibility of hypoechoic targets but

annot be recommended for improving needle vis-bility.19,22 Electronic beam steering is potentiallyseful, especially when performing deeper in planelocks at small needle-beam angles, e.g., infracla-icular. Early limitations of this technology in-luded deterioration of image quality, and vulner-bility to noise and distortion;45 hence it has noteen a standard feature on most machines. This isikely to change; for example, the LOGIQe (GEealthcare, Wauwatosa, WI) compact US unit nowffers a beam steering function (B-Steer) designedo improve needle visibility. One concern ishether nerve visibility may be compromised with

he change in beam angle given that many nervesre anisotropic (i.e., their echogenicity varies de-ending on the angle at which they are insonated).The use of color Doppler combined with a mov-

ng needle tip is promising,24-26 and worthy of fur-her investigation. Although manually-inducedeedle motion has been described,42,43 our own

imited experience suggests that this generates toouch color artifact along the needle shaft to allow

ccurate localization of the tip. Adjusting the coloroppler gain (usually the only means of adjustingolor Doppler imaging parameters on compact USachines) can help reduce artifact but also reduces

he signal intensity at the needle tip. Mechanicallynduced, high frequency vibratory motion of theeedle tip, such as that generated by the ColorMarkevice, appears to be the most practical technique,lthough it still requires optimization of color Dopp-er settings for successful use.24,26 The ColorMarkevice could be used with existing block needles,lthough this has not been reported to date. Itspplication in PNB may be limited by its bulk,hich caused bending of the shaft when used with2-gauge needles.25 In addition, it performed lessell at depths �3 cm, due to attenuation of theeedle tip vibration.25,41 Finally, we have observedeterioration in image quality within the coloroppler target area in some US machines that can

ender nerves nearly invisible. It would be counter-roductive to increase needle tip visibility at thexpense of target visibility and this issue will need
o be addressed if the technique is to become useful. m
urrogate Markers of Needleip Location


Despite the strategies discussed above, the oper-tor may still encounter difficulty in achieving goodeedle tip visibility. However, needle tip locationay be inferred using other methods described in

he literature.

trategies and Recommendations

Tissue movement. Jiggling the needle inmall, controlled, in-out movements creates corre-ponding visible tissue movement at the needle tipnd is recommended when advancing the needle.29

ne should be aware that tissue motion may beransmitted beyond the needle tip as well as alonghe needle shaft, making it difficult to preciselyocate the tip, especially when using the out oflane needle approach. We recommend the use ofhort-beveled needles because in our experience,hey minimize the risk of piercing nerves and arter-es in the event of unintentional needle contact.uch needle contact may in fact provide furtherisual cues to tip location (Fig 5). Short-beveledeedles also provide tactile feedback when “pop-ing” through fascial layers; this is a useful adjuncto visible tissue movement.

Hydrolocation. Hydrolocation involves rapidnjection of a small amount of fluid (0.5-1 mL) toonfirm needle-tip position by both tissue move-ent and the appearance of a small anechoic

pocket” (Fig 5).46 Further injection of fluid alsoids in opening up the space between anatomicaltructures (hydrodissection), thus creating an ob-tacle-free path for further needle repositioning.he needle tip is often accentuated as a bright echo-enic structure within the dark anechoic pocket ofuid. Either local anesthetic or 5% dextrose may besed as the injectate. The advantage of using 5%extrose is that it preserves the motor response toubsequent electrical stimulation.47,48 There is alsoess “waste” of local anesthetic by deposition distantrom the target nerve.

Microbubble injection. A variation on theechnique of hydrolocation is the injection of mi-robubbles, which are highly echogenic and serves an US contrast agent. Microbubble injection haseen used to confirm catheter tip location in con-inuous PNB.49,50 However, the potential disadvan-age of any technique involving injection of air intooft tissue is deterioration of image quality. Micro-ubbles cause acoustic shadowing that obscures thearget area, and can persist for up to 2 minutes or
ore.51 We consider this deterioration to be a sig-

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ificant disadvantage in single shot PNB, whereepositioning of the needle is often required afternitial injection to achieve optimal local anestheticpread around the target.

onclusion

Needle visualization during US-guided regionalnesthesia is likely essential for safety and efficacy.

ig 5. (A) A 22-gauge needle is inserted toward theusculocutaneous nerve, but the tip is not clearly visible.

B) Indentation of the fascia surrounding the musculo-utaneous nerve indicates the location of the needle tip.C) Injection of a small amount of fluid confirms theocation of the needle tip next to the musculocutaneouserve (hydrolocation). The needle tip is also highlightedy the contrast between it and the anechoic pocket ofuid.

owever, accurate and consistent needle tip visu-

lization is hampered by several factors, includinghe difficulty of needle-beam alignment, and theoor echogenicity of commonly available blockeedles in the clinical setting. In our experience,ystematic manipulation of the needle and trans-ucer to ensure needle-beam alignment, maintain-ng a large needle-beam angle where possible, andtilizing surrogate markers of tip location such asissue movement and hydrolocation are most help-ul. Future avenues for improving visualization in-lude the development of more echogenic needles,nd advances in ultrasound imaging technology,uch as 3-dimensional US, and the use of coloroppler to identify a moving needle tip.

ppendix

Selected articles for this review were graded ac-ording to their level of evidence as recommendedy the Centre for Evidence-Based Medicine.

References

1. Chapman GA, Johnson D, Bodenham AR. Visualisa-tion of needle position using ultrasonography. Anaes-thesia 2006;61:148-158.

2. Sites BD, Spence BC, Gallagher JD, Wiley CW, Ber-trand ML, Blike GT. Characterizing novice behaviorassociated with learning ultrasound-guided periph-eral regional anesthesia. Reg Anesth Pain Med 2007;32:107-115.

3. Hatada T, Ishii H, Ichii S, Okada K, Yamamura T.Ultrasound-guided fine-needle aspiration biopsy forbreast tumors: Needle guide versus freehand tech-nique. Tumori 1999;85:12-14.

4. Phal PM, Brooks DM, Wolfe R. Sonographicallyguided biopsy of focal lesions: A comparison of free-hand and probe-guided techniques using a phantom.AJR Am J Roentgenol 2005;184:1652-1656.

5. Tsui BC. Facilitating needle alignment in-plane to anultrasound beam using a portable laser unit. RegAnesth Pain Med 2007;32:84-88.

6. Perrella RR, Kimme-Smith C, Tessler FN, RagavendraN, Grant EG. A new electronically enhanced biopsysystem: Value in improving needle-tip visibility dur-ing sonographically guided interventional proce-dures. AJR Am J Roentgenol 1992;158:195-198.

7. Bergin D, Pappas JN, Hwang JJ, Sheafor DH, PaulsonEK. Echogenic polymer coating: Does it improve nee-dle visualization in sonographically guided biopsy?AJR Am J Roentgenol 2002;178:1188-1190.

8. Jandzinski DI, Carson N, Davis D, Rubens DJ, VociSL, Gottlieb RH. Treated needles: Do they facilitatesonographically guided biopsies? J Ultrasound Med2003;22:1233-1237.

9. Gottlieb RH, Robinette WB, Rubens DJ, Hartley DF,Fultz PJ, Violante MR. Coating agent permits im-proved visualization of biopsy needles during sonog-
raphy. AJR Am J Roentgenol 1998;171:1301-1302.

1

1

1

1

1

1

1

1

1

1

2

2

2

2

2

2

2

2

2

2

3

3

3

3

3

3

3

3

3

3

4


0. Culp WC, McCowan TC, Goertzen TC, Habbe TG,Hummel MM, LeVeen RF, Anderson JC. Relativeultrasonographic echogenicity of standard, dimpled,and polymeric-coated needles. J Vasc Interv Radiol2000;11:351-358.

1. Hopkins RE, Bradley M. In-vitro visualization of bi-opsy needles with ultrasound: A comparative studyof standard and echogenic needles using an ultra-sound phantom. Clin Radiol 2001;56:499-502.

2. Nichols K, Wright LB, Spencer T, Culp WC. Changesin ultrasonographic echogenicity and visibility ofneedles with changes in angles of insonation. J VascInterv Radiol 2003;14:1553-1557.

3. Deam RK, Kluger R, Barrington MJ, McCutcheonCA. Investigation of a new echogenic needle for usewith ultrasound peripheral nerve blocks. Anaesth In-tensive Care 2007;35:582-586.

4. Bondestam S, Kreula J. Needle tip echogenicity. Astudy with real time ultrasound. Invest Radiol 1989;24:555-560.

5. Bisceglia M, Matalon TA, Silver B. The pump maneu-ver: An atraumatic adjunct to enhance US needle tiplocalization. Radiology 1990;176:867-868.

6. Bradley MJ. An in-vitro study to understand success-ful free-hand ultrasound guided intervention. ClinRadiol 2001;56:495-498.

7. Schafhalter-Zoppoth I, McCulloch CE, Gray AT. Ul-trasound visibility of needles used for regional nerveblock: An in vitro study. Reg Anesth Pain Med 2004;29:480-488.

8. Maecken T, Zenz M, Grau T. Ultrasound characteris-tics of needles for regional anesthesia. Reg Anesth PainMed 2007;32:440-447.

9. Mesurolle B, Bining HJ, El Khoury M, Barhdadi A,Kao E. Contribution of tissue harmonic imaging andfrequency compound imaging in interventionalbreast sonography. J Ultrasound Med 2006;25:845-855.

0. Cohnen M, Saleh A, Lüthen R, Bode J, Mödder U.Improvement of sonographic needle visibility in cir-rhotic livers during transjugular intrahepatic porto-systemic stent-shunt procedures with use of real-time compound imaging. J Vasc Interv Radiol 2003;14:103-106.

1. Saleh A, Ernst S, Grust A, Fürst G, Dall P, Mödder U.Real-time compound imaging: Improved visibility ofpuncture needles and localization wires as comparedto single-line ultrasonography [in German]. Rofo2001;173:368-372.

2. Karstrup S, Brøns J, Morsel L, Juul N, von der ReckeP. Optimal set-up for ultrasound guided puncturesusing new scanner applications: An in-vitro study.Eur J Ultrasound 2002;15:77-84.

3. Baker JA, Soo MS, Mengoni P. Sonographicallyguided percutaneous interventions of the breast us-ing a steerable ultrasound beam. AJR Am J Roentgenol1999;172:157-159.

4. Feld R, Needleman L, Goldberg BB. Use of needle-vibrating device and color Doppler imaging for sono-graphically guided invasive procedures. AJR Am J
Roentgenol 1997;168:255-256.
5. Jones CD, McGahan JP, Clark KJ. Color Dopplerultrasonographic detection of a vibrating needle sys-tem. J Ultrasound Med 1997;16:269-274.

6. Armstrong G, Cardon L, Vilkomerson D, Lipson D,Wong J, Rodriguez LL, Thomas JD, Griffin BP. Local-ization of needle tip with color Doppler during peri-cardiocentesis: In vitro validation and initial clinicalapplication. J Am Soc Echocardiogr 2001;14:29-37.

7. Gray AT. Ultrasound-guided regional anesthesia:Current state of the art. Anesthesiology 2006;104:368-373.

8. Dodd GD 3rd, Esola CC, Memel DS, Ghiatas AA,Chintapalli KN, Paulson EK, Nelson RC, Ferris JV,Baron RL. Sonography: The undiscovered jewel ofinterventional radiology. Radiographics 1996;16:1271-1288.

9. Matalon TA, Silver B. US guidance of interventionalprocedures. Radiology 1990;174:43-47.

0. Memel DS, Dodd GD 3rd, Esola CC. Efficacy ofsonography as a guidance technique for biopsy ofabdominal, pelvic, and retroperitoneal lymph nodes.AJR Am J Roentgenol 1996;167:957-962.

1. Buonocore E, Skipper GJ. Steerable real-time sono-graphically guided needle biopsy. AJR Am J Roentge-nol 1981;136:387-392.

2. Han D, Lan Seo Y, Soon Choi C, Chul Kim H, YoungYoon D, Hoon Bae S, Hee Moon J, Hyup Kim S, SooKim S, Han H. A steerable guiding device: The newmethod in ultrasound guidance. Invest Radiol 2002;37:626-631.

3. Reid MH. Real-time sonographic needle biopsyguide. AJR Am J Roentgenol 1983;140:162-163.

4. Marhofer P, Chan VW. Ultrasound-guided regionalanesthesia: Current concepts and future trends.Anesth Analg 2007;104:1265-1269.

5. Tsui BC, Dillane D. Needle puncture site and a “walk-down” approach for short-axis alignment during ul-trasound-guided blocks. Reg Anesth Pain Med 2006;31:586-587.

6. Sites BD, Brull R, Chan VW, Spence BC, Gallagher J,Beach ML, Sites VR, Hartman GS. Artifacts and pitfallerrors associated with ultrasound-guided regionalanesthesia. Part I: Understanding the basic principlesof ultrasound physics and machine operations. RegAnesth Pain Med 2007;32:412-418.

7. Feinglass NG, Clendenen SR, Torp KD, Wang RD,Castello R, Greengrass RA. Real-time 3-dimensionalultrasound for continuous popliteal blockade: A casereport and image description. Anesth Analg 2007;105:272-274.

8. Foxall GL, Hardman JG, Bedforth NM. Three-dimen-sional, multiplanar, ultrasound-guided, radial nerveblock. Reg Anesth Pain Med 2007;32:516-521.

9. Taylor KJ, Holland S. Doppler US. Part I. Basic prin-ciples, instrumentation, and pitfalls. Radiology 1990;174:297-307.

0. Klein SM, Fronheiser MP, Reach J, Nielsen KC,Smith SW. Piezoelectric vibrating needle and cathe-ter for enhancing ultrasound-guided peripheral
nerve blocks. Anesth Analg 2007;105:1858-1860.

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4

4

4

4

4

4

4

4

5

5

5


1. Cockburn JF, Cosgrove DO. Device to enhance visi-bility of needle or catheter tip at color Doppler US.Radiology 1995;195:570-572.

2. Hamper UM, Savader BL, Sheth S. Improved needle-tip visualization by color Doppler sonography. AJRAm J Roentgenol 1991;156:401-402.

3. Longo JM, Bilbao JI, Barettino MD, Larrea JA, Pueyo J,Idoate F, deVilla VH. Percutaneous vascular and non-vascular puncture under US guidance: Role of colorDoppler imaging. Radiographics 1994;14:959-972.

4. Harmat A, Rohling RN, Salcudean SE. Needle tiplocalization using stylet vibration. Ultrasound Med Biol2006;32:1339-1348.

5. Cheung S, Rohling R. Enhancement of needle visi-bility in ultrasound-guided percutaneous procedures.Ultrasound Med Biol 2004;30:617-624.

6. Perlas A. A concerning direction: In response. Anes-thesiology 2004;100:1326-1327.

7. Tsui BC, Kropelin B. The electrophysiological effect ofdextrose 5% in water on single-shot peripheral nervestimulation. Anesth Analg 2005;100:1837-1839.

8. Tsui BC, Kropelin B, Ganapathy S, Finucane B. Dex-trose 5% in water: Fluid medium for maintainingelectrical stimulation of peripheral nerves duringstimulating catheter placement. Acta AnaesthesiolScand 2005;49:1562-1565.

9. Dhir S, Ganapathy S. Use of ultrasound guidance andcontrast enhancement: A study of continuous infra-clavicular brachial plexus approach. Acta Anaesthesiol
Scand 2008;52:338-342.
0. Swenson JD, Davis JJ, DeCou JA. A novel approachfor assessing catheter position after ultrasound-guided placement of continuous interscalene block.Anesth Analg 2008;106:1015-1016.

1. Kort A, Kronzon I. Microbubble formation: In vitro andin vivo observation. J Clin Ultrasound 1982;10:117-120.

2. Centre for Evidence-Based Medicine. Levels ofevidence. http://www.cebm.net/index.aspx?o�1025.Accessed July 15, 2008.

Appendix 1. Levels of Evidence as Defined bythe Oxford Centre for Evidence-Based Medicine

(May 2001)

Level Therapy/Prevention, Etiology/Harm

1a Systematic review (with homogeneity) of RCTs1b Individual RCT (with narrow confidence interval)1c All or none2a Systematic review (with homogeneity) of cohort studies2b Individual cohort study (including low quality RCT; e.g.,

�80% follow-up)2c “Outcomes” research; ecological studies3a Systematic review (with homogeneity) of case-control

studies3b Individual case-control study4 Case series (and poor quality cohort and case-control

studies)5 Expert opinion without explicit critical appraisal, or

based on physiology, bench research or “firstprinciples”

Abbreviation: RCT, randomized controlled trial.
Adapted from the Centre for Evidence-Based Medicine.52
http://www.cebm.net/index.aspx?o=1025

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