ultrasound-guided regional anesthesia and analgesia · regional anesthesia and pain medicine &...

Ultrasound-Guided Regional Anesthesia and AnalgesiaA Qualitative Systematic Review

Spencer S. Liu, MD, Justin E. Ngeow, BA, and Jacques T. YaDeau, MD, PhD

Abstract: Ultrasound guidance has become popular for performanceof regional anesthesia and analgesia. This systematic review summarizesexisting evidence for superior risk to benefit profiles for ultrasoundversus other techniques. Medline was systematically searched forrandomized controlled trials (RCTs) comparing ultrasound to anothertechnique, and for large (n 9 100) prospective case series describingexperience with ultrasound-guided blocks. Fourteen RCTs and 2 caseseries were identified for peripheral nerve blocks. No RCTs or case serieswere identified for perineural catheters. Six RCTs and 1 case series wereidentified for epidural anesthesia. Overall, the RCTs and case seriesreported that use of ultrasound significantly reduced time or number ofattempts to perform blocks and in some cases significantly improved thequality of sensory block. The included studies reported high incidence ofefficacy of blocks with ultrasound (95%Y100%) that was not signifi-cantly different than most other techniques. No serious complicationswere reported in included studies. Current evidence does not suggest thatuse of ultrasound improves success of regional anesthesia versus mostother techniques. However, ultrasound was not inferior for efficacy, didnot increase risk, and offers other potential patient-oriented benefits. AllRCTs are rather small, thus completion of large RCTs and case series areencouraged to confirm findings.

Key Words: ultrasound, peripheral nerve block, epidural anesthesia.

(Reg Anesth Pain Med 2009;34: 47Y59)

U se of ultrasound to guide placement of needles and cathe-ters for regional anesthesia and analgesia has become in-

creasingly popular. Recent review articles on this topic havebeen published in major anesthesia journals,1Y5 and many anes-thesiology meetings offer lectures and workshops on the useof ultrasound including the 2008 annual meetings of the Ame-rican Society of Regional Anesthesia and Pain Medicine (http://www.asra.com/education/ASRA-brochure-2008.pdf) and theInternational Anesthesia Research Society (http://www.iars.org/documents/2008%20Program.pdf). Increased popularity ofultrasound may be due to multiple reasons such as dissatisfac-tion with success rates of traditional block techniques,6 prefer-ence for a visual endpoint, increased familiarity with ultrasound,overall increased exposure to regional anesthesia,7 or a belief inincreased safety with use of ultrasound guidance. As with anynew technology, it becomes critical during evolution of use toprovide evidence for superior risk/benefit profiles over existingmethods to justify evidence-based adoption of a new techno-

logy. This systematic review will summarize existing evidenceand suggest future directions.

METHODSThe National Library of Medicine_s Medline database was

searched for the time period 1966 to November 2007. Twoauthors (S.S.L. and J.T.Y.) performed independent searches.Search strategies included the terms Bultrasound,[ Bnerveblock,[ continuous,[ Bepidural anesthesia,[ Bepidural anal-gesia,[ and Bspinal anesthesia.[ This initial search identified430 potential articles for systematic review. All of the aboveabstracts were reviewed for potential inclusion in the system-atic review. Only the following types of articles were included:randomized controlled trials (RCTs) comparing ultrasoundguidance to an alternative technique, and large prospectivecase series that could provide estimates of efficacy and safety asdefined for the described ultrasound guidance technique. Wedefined a Blarge[ case series as 9100 patients. Assuming anapproximately 90% efficacy rate, then this sample size allows a95% confidence interval of T5% of true incidence. For thepurpose of this review, we defined efficacy or success as notrequiring conversion to an alternative anesthetic technique (e.g.,general anesthesia). After selecting the initial articles, the ref-erence list of each of the analyzed articles was checked for anyadditional studies, as were the authors_ personal files for ad-ditional references that met all inclusion criteria.

RESULTS

Peripheral Nerve BlocksRandomized controlled trials for ultrasound-guided

upper extremity anesthesia. Seven RCTs for adults thatcompared ultrasound guidance to an alternative techniquewere identified (Table 1).8Y14 All RCTs reported some clinicalbenefit with ultrasound guidance; however, none reported astatistically significant difference in block efficacy in terms offailed block requiring general anesthesia. Six of 7 RCTsreported no significant differences between techniques inrequiring supplemental analgesia.8,9,11Y14 No persistent compli-cations were observed in any RCT. Two RCTs measured patientsatisfaction without noting any differences in techniques.8,12

Five studies examined axillary block for upper extremityprocedures.8Y12 Four of 5 RCTs measured block performanceand all reported either fewer needle passes or faster time forblock performance (G5 minutes difference).8Y11 Four of 5 RCTsreported faster or more complete early onset of sensory or motorblock, however, no RCTs reported a significant difference inonset of surgical anesthesia.8Y10,12 Soeding et al. examinedinterscalene block for shoulder surgery and also reported morecomplete early sensory and motor block without any differencein anesthetic success or duration of analgesia.12 Williams et al.examined supraclavicular block with either ultrasound alone orultrasound with nerve stimulator, and noted faster blockperformance time (5 minutes difference) without a differencein onset or success of sensory and motor block.13 No differences

REVIEW ARTICLE

Regional Anesthesia and Pain Medicine & Volume 34, Number 1, January-February 2009 47

From the Department of Anesthesiology, Hospital for Special Surgery andWeill Medical College of Cornell University, New York, NY.Accepted for publication April 12, 2008.Address correspondence to: Spencer S. Liu, MD, Department of Anesthe-

siology, Hospital for Special Surgery, 535 E 70th Street, New York, NY10021 (e-mail: [email protected]).

Copyright * 2009 by American Society of Regional Anesthesia and PainMedicine

ISSN: 1098-7339DOI: 10.1097/AAP.0b013e3181933ec3

Copyright @ 2009 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

TABLE

1.Ra

ndom

ized

Con

trolledTrialswith

Ultrasou

nd-G

uide

dUpp

erExtrem

ityPe

riphe

ralN

erve

Bloc

k

Study

Groups(n:Technique)

PrimaryOutcom

eBlock

Perform

ance

OnsetTim

eEfficacy

Com

plication

sPatient

Satisfaction

Casati200

78Axillary

block

Forearm,wristandhand

procedures

30:4nervebranches,

injectionultrasou

nd30

:4nervebranches,

injectionNS

20mL0.75

%ropivacaine

Powered

todetect

a5minutedifference

intheon

setof

nerveblockade.

Fewer

median(range)

needle

passes

for

ultrasou

nd4*

(3Y8)

versus

stim

ulator

8(5Y13).

End

pointforperformance:

only

forw

ardmovem

ent

oftheneedle

preceded

byaretractio

nof

atleast

10mm

coun

tedas

apass.

Sensory

onsetfaster

with

ultrasou

nd;1

4T6

versus

18T6minutes.*

Nodifference

inonseto

fmotor

blockor

readinessforsurgery.

NoGA:1

00%

inboth

groups.No

supplement:same

forultrasound

(97%

)versus

NS(94%

).

Moreblock-relatedpain

with

NS(48%

)versus

ultrasound(20%

).Noneurologic

complications

at24

hoursineither

group.

No

difference

infuture

acce

ptance

ofanesthetic

techniqu

e(100

%ultrasou

ndvs.93%

nerve

stim

ulator).

Chan20

079

Axillary

block

Handsurgery

64:3injectionultrasou

nd62

:3injectionNS

62:3injectionbo

th42

mL2%

lidocaine

with

0.5%

bupivacaine

Powered

todetect

anincrease

inrate

ofsuccessful

block

(providing

complete

sensory

anesthesia

inthedistribu

tionof

all3

target

nerves:median,

radial,ulnar)

from

anestim

ated

baselin

eof

80%

to95

%.

Faster

bloc

kpe

rforman

cewith

ultrasound

versus

NS

versus

both

(9.3*vs.

11.2

vs.12.4minutes).

Endpointfor

performance:

timefrom

palpationof

axillaryarteryorultrasound

probeapplicationtothe

endof

thelocal

anestheticinjection.

Morecompletesensory

blockat

30minutes

with

ultrasoundandboth

versus

NS(83vs.81

vs.63%

).*Nodifference

inonsetof

motor

block.

NoGA:sam

eultrasound

versus

NSversus

both

(98vs.95vs.98%

).Nosupplement:same

forultrasound

(95%

)versus

NS(86%

)versus

both

(92%

).

Nodifference

intransientpo

stblock

paresthesiafor

ultrasou

ndversus

NSversus

both

(20

vs.21

vs.15

%).

More

localbruising

with

NSversus

ultrasoundversus

both

(13*

vs.3

vs.0%).

N/A

Sites20

0610

Axillary

block

Handsurgery

28:TA

28:3injectionultrasou

nd10

mL1.5%

lidocaine

with

5Kg/mL

epinephrine

Powered

todetecta20

%difference

intherate

offailedblocks

(blocks

notdonewith

in20

minutesorrequiring

intraoperative

conversion

toGA).

Faster

blockperformance

inultrasou

ndgrou

pversus

TAgrou

p:7.9*

T3.9versus

11.1T5.7minutes,

respectiv

ely.

End

pointfor

performance:

timefrom

completionof

sterile

preparationtothe

finalw

ithdraw

alof

the

needle.

Nodifferencesbetween

grou

psultrasou

ndand

TAinpercentofpatients

with

completesensory

ormotorblock(5Y30

minutes

postblock)

except

motor

at15

and

25minutes.*

Feweroverallfailures

inultrasound

versus

TA:0%versus28%.*

NoGA:ultrasound

(0%)

versusTA

(14%

).Nosupplement:same

forboth

ultasound

andTA

at82%.

On1to

2week

follo

w-up,

nodo

cumented

cases

ofpersistin

gparesthesias.

N/A

Liu

2005

11

Axillary

block

Forearm

andhand

surgery

30:ultrasound

singleinjection

30:UD

30:ND

0.5mL/kg1.5%

lidocaine

with

5Kg/kg

epinephrine

Powered

todetecta20

%difference

intherate

ofadverseou

tcom

es.

Faster

performance

inultrasou

ndandUDgrou

psversus

ND:6.5T1.3and

6.7T1.3versus

8.2*

T1.5minutes.

End


timefrom

needlepu

ncture

(ND)or

ultrasou

ndapplicationon

skin

tothe

completionof

thelocal

anesthetic

injection.

Sim

ilarefficacy

inall

3grou

psat

blocking

all7

sensoryandmotor

nerves

after40

minutes:ultrasou

ndandND,70%

;UD,73%

.

NoGA:no

differences

betweenultrasound

versus

UDversus

ND(97versus

100

versus

100%

).Nosupplement:no

differencesbetween

ultrasoundversus

UDversus

ND(87

vs.90

vs.90%

).

Com

binedincidence

ofadverseevents

(paresthesia,axillary

vesselpuncture,and

subcutaneous

hematom

a)ingroup

NDsignificantly

higherthan

inultrasoundandUD

groups:20%

*versus

0%versus

0%.

N/A

Liu et al Regional Anesthesia and Pain Medicine & Volume 34, Number 1, January-February 2009

48 * 2009 American Society of Regional Anesthesia and Pain Medicine


Soeding

2005

12

Interscalene

andAxillary

block

Upp

erlim

bsurgery

20:ultrasou

nd13

:ISB,7:

axillary

20:surface

land

mark-based

11:ISB,9:

axillary

3mg/kg

ropivacaine

Not

performed.

N/A

More

complete

sensory

andmotor

blockat10

and

20minutes

post

blockwith

ultrasound.*

NoGA:nodifference

ultrasou

ndversus

land

mark(95vs.

90%).

Nosupp

lement:N/A.

Sim

ilarduration

ofanalgesiafor

ultrasou

ndversus

land

mark(10.3vs.

11.2ho

urs).

Noseizureor

neurapraxiain

either

grou

p.

Similarp

atient

satisfaction

scores

ultrasound

versus

landmark

(rated

onPO

D7,9.2

vs.8.9,out

of10).

Williams

2003

13

Sup

raclavicular

block

Distalarm,forearm,or

hand

surgery

40:u

ltrasound-guidedwith

NS(ultrasound

group)

40:N

S(N

Sgroup)

1:1Bupivacaine

0.5%

with

Lidocaine

2%with

1:200,000epinephrine

Not

performed.

Faster

blockperformance

ingroupultrasound

than

ingroupNS:

5.4*

T2.4minutes

versus

9.8T

7.5minutes.

End


intervalbetweenfirst

needleinsertionand

finaln

eedlewith

draw

al.

Sim

ilarrate

ofpartialor

completesensoryblock

inallnerve

territo

ries

after30minutes.

Groupsultrasound

versus

NS:

95%

versus

85%.

55%

ofgroupultrasound

and65%

ofgroupNS

hadcompleteblockof

allnerve

territo

ries.

NoGA:n

odifferences

betweenultrasound

andNS(100

vs.92%

).Nosupplement:no

differencesbetween

ultrasound

andNS

(85vs.78%

).Sim

ilardu

ration

for

ultrasou

ndandNS:

846T53

1versus

652T47

3minutes).

After

1week:

2patientsfrom

grou

pultrasou

ndrepo

rted

paresthesias

and

1patient

from

grou

pNSrepo

rted

loss

ofsensationon

the

palm

arsurfaceof

thethum

b.

N/A

Dingemans

2007

14

Infraclavicularblock

Hand,forearm,and

distal

arm

surgery

36:ultrasou

nd-guided

perivascular

(ultrasou

ndgrou

p);29

patients

requ

ired

1injectionfor

desiredspread;6

patientsrequ

ired2

injections;1patient

requ

ired

3injections

36:sing

leinjection

ultrasou

nd-guided

with

NS(N

Sgrou

p)0.5mL/

kg(toamax.o

f40

mL)

of1:30.5%

bupivacaine

and2%

lidocaine

with

1:20

0,00

0epinephrine

Powered

todetect

difference

of1.6minutes

inperformance

time

betweenthe2

techniqu

es.

Faster

blockperformance

forultrasou

ndgrou

pthan

forNSgrou

p(3.1*T1.6

versus

5.2T4.7minutes).

End


timebetweenskin

puncture

andfinalneedle

with

draw

al.S

imilar

lock

-related

discom

fort

scores

forultrasou

ndand

NSgrou

ps(2.8

vs.2

.5).

More

complete

sensory

blockafter30

minutes

forultrasou

ndversus

NS(86%

*vs.57

%).

InGroup

ultrasound,

numberof

injections

(singlevs.m

ultip

le)did

notaffectrateof

complete

block

(86%

forboth).

NoGA:10

0%bo

thgrou

ps.

Nosupp

lement:

greatersuccess

with

ultrasou

ndversus

NS

(92vs.74

%*).

Sim

ilartim

eintervalsfrom

blockto

first

analgesic

use

for

grou

psultrasou

ndandNS(7

T3vs.

8T5ho

urs).

1patientwith

paresthesia

lasting

7days

ingrou

pultrasou

nd.

N/A

Abbreviations:GA,g

eneralanesthesia;N/A,n

otapplicable;ND,n

erve

stim

ulator

with

double

injection;

NS,n

erve

stim

ulator;TA

,transarterial;UD,u

ltrasound

with

doubleinjection;

POD,

postoperativeday;

ISB,interscaleneblock.

*Pe.05in

statistical

assays

forsignificance.

Regional Anesthesia and Pain Medicine & Volume 34, Number 1, January-February 2009 US-Guided Regional Anesthesia and Analgesia

* 2009 American Society of Regional Anesthesia and Pain Medicine 49


were noted for surgical efficacy. Dingemans et al. examinedinfraclavicular block with either ultrasound alone, or ultrasoundwith nerve stimulator-guided single injection.14 They notedfaster block performance (3 minutes difference), more completeearly block, and significantly less need for analgesic supple-mentation with ultrasound alone.

One RCT was identified for pediatric patients undergoinginfraclavicular block for arm and forearm surgery15 (Table 2).Use of ultrasound guidance reduced discomfort during blockplacement and hastened onset of sensory and motor block. Therewere no differences in discomfort during surgery, althoughsensory block duration was greater with ultrasound guidance.

No RCTs were identified for perineural catheters.Randomized controlled trials for ultrasound-guided

lower extremity and lower body anesthesia. Four RCTs inadults that compared ultrasound guidance to an alternativetechnique were identified (Table 3).18Y21 No RCTs observed adifference between techniques in failed blocks. No RCTsobserved any persistent complications. Three RCTs examinedfemoral nerve blocks.18,20,21 Casati et al. examined ultrasoundversus nerve stimulator-guided femoral nerve blocks in patientsundergoing knee arthroscopy with a preexisting sciatic nerveblock.18 The RCT was designed to determine the minimum ef-fective anesthetic volume (MEAV) for the femoral nerve block;as such it was designed to directly measure a 50% effective dosewith a planned 50% failure rate in both groups. MEAV wassignificantly less in the ultrasound group. Marhofer et al.performed 2 RCTs examining femoral nerve block in hip traumapatients.20,21 Both RCTs observed faster and more completeearly onset of sensory block with ultrasound. Both RCTs ob-served no differences in failed blocks. One RCTexamined ultra-sound plus nerve stimulator versus nerve stimulator alone forlateral sciatic block for foot and ankle surgery.19 Addition ofultrasound decreased number of needle passes but did not shortenblock performance time. Addition of ultrasound improved toler-ance to ankle tourniquet, and increased the number of patientsnot needing any analgesics. However, incidence of block failurerequiring spinal anesthesia was not different between groups.

Two RCTswere identified in pediatric patients (Table 2).16,17

One study examined ilioinguinal/iliohypogastric nerve blockcombined with a fixed concentration of sevoflurane for inguinalhernia and urologic surgery.16 Patients randomized to ultrasoundguidance required less local anesthetic for the block, less fen-tanyl with incision, and less postoperative analgesics. One RCTexamined sciatic and femoral blocks for lower extremity sur-gery.17 Less local anesthetic was required for the block withultrasound and a longer duration of postoperative analgesia(È3 hours greater) was reported.

No RCTs were identified for perineural catheters.Large case series for peripheral nerve blocks. Two

prospective case series were identified for infraclavicular22 andfor supraclavicular blocks (Table 4).23 All case series reported998% success rate as defined by not needing conversion togeneral anesthesia and none reported any persistent complica-tions, although no patients were followed up for greater than24 hours. No large prospective case series was identified forultrasound-guided lower extremity or lower body blocks. Nolarge prospective case series was identified for ultrasound-guided perineural catheters.

Central Neuraxial BlocksRandomized controlled trials for ultrasound-guided

central neuraxial blockade. Six RCTs24Y29 were identifiedthat compared ultrasound guidance to an alternative technique(Table 5). Five RCTs were from the same authors, had similar

study design, and were performed for placement of obstetricalepidurals.24Y28 Of these 5, all but 1 employed prepunctureultrasound scanning to identify the puncture site, the depth ofthe epidural space, and the angle for needle passage. In 4 RCTs,all epidurals were placed by the same author with inherentlimitations on applicability to other clinicians.24,26Y28 In theinitial RCT,27 preparation time was the same with or withoutultrasound prescanning, and prescanning reduced puncture at-tempts needed for successful combined spinal epidural. Thesecond RCT26 randomized parturients with presumed difficultepidural puncture to prescanning and similarly found reducedpuncture attempts. Additionally, this study found that ultrasoundprescanning for epidurals improved parturient satisfaction andreduced visual analog scale pain scores during labor. The nextRCT24 was of larger scale, and found that the scan added75 seconds to the preparation time. Patients in the ultrasoundgroup needed fewer puncture attempts, fewer intervertebralspaces were punctured, and fewer catheter advancementattempts were made. Patients in the ultrasound group reportedlower pain scores during labor or surgery, and had fewerheadaches and backaches. The failure rate was the same inboth groups. The most recent study from this group28

randomized 10 parturients per group to combined spinal epi-dural performed either without ultrasound, with an ultrasoundprescan, or with online ultrasound imaging during perfor-mance of the block. In both ultrasound groups, fewer punctureattempts were needed compared with control. Patient satisfac-tion was the same in all groups. No major differencesin epidural block were found between prescanning and realtime ultrasound use in this study, but a power analysis was notpresented.

A final RCT from the same group examined the effect ofprepuncture ultrasound scanning on resident performance forepidural placement for obstetrics.25 In the control group,residents had an initial success rate of 60%, which increasedover time to 84%. Success rates for the ultrasound groupincreased from 86% to 94%. No persistent complications wereobserved in any RCT from these authors.

One RCT for pediatric patients undergoing epiduralcatheter placement in addition to general anesthesia for majorsurgery was identified (Table 5),29 which compared real timeultrasound-guided epidural placement to a standard loss ofresistance technique. No primary outcome was specified. Use ofultrasound guidance reduced the rate of needle to bone contacts(17% vs. 71%), and increased the speed of catheter placement(3 vs. 4 minutes). All epidurals were placed successfully, nomajor complications occurred in either group, and postoperativeanalgesia was similar in both groups.

Large case series for ultrasound-guided central neurax-ial blockade. One large prospective case series was identifiedfor central neuraxial blockade.30 Prepuncture ultrasound scan-ning was performed to identify the distance from the skin to theepidural space for 180 pediatric patients. In 179 patients, theepidural space was located with the first puncture attempt. Nopostoperative complications were noted.

DISCUSSION

Does Ultrasound Guidance ImproveBlock Efficacy?

Current evidence suggests that efficacy for ultrasound-guided regional anesthesia and analgesia as defined by failedblocks is similar to most other techniques such as neurostimula-tion. Importantly, ultrasound guidance was not reported to beinferior in any RCT. In general, RCTs are small and quite diverse




TABLE

2.Pe

diatric

Rand

omized

Con

trolledTrialswith

Ultrasou

nd-G

uide

dPe

riphe

ralN

erve

Bloc

ks

Study

Groups(n:Technique)

Pow

erAnalysis

Block

Perform

ance

OnsetTim

eEfficacy

Com

plication

sPatient

Satisfaction

Marho

fer

2004

15

Infraclavicularbrachial

plexus

block

Arm

andforearm

surgery

20:ultrasou

nd,medianage6

(range

2Y10

)20

:NS,medianage6

(range

1Y9)

Premed

ication

with

rectal

midazolam

1mL/kgup

toamaxim

umof

10mgand

intrav

enous

midazolam

0.05

to0.1mL/kg

Rop

ivacaine

0.5%

0.5mL/kg

Not

performed

Low

erVASdu

ring

theperformance

oftheblocks

inultrasou

ndversusNS,m

ean:3

(range

1Y4)

versus

3.75

(range

3Y5)*

Sho

rter

sensoryblock

onsettim

esforultrasou

ndversus

NS(m

edian):9(range

5Y15

)versus

15(range

5Y25

)minutes*

Morecompletesensoryblockat

10minutew

with

ultrasound*

formusculocutaneous,median,

andulnarnervedistributio

nsMorecompletemotor

blockat

10minuteswith

ultrasound*for

axillary,musculocutaneous,

andulnarnerves

Nodifference

inVAS

observed

before

blocks,

30minutes

afterblocks,

ordu

ring

surgery

Lon

germ

edian(range)

sensory

block

duratio

nforultrasou

ndversus

NS:

384(280Y480)

versus

310

(210

Y420

)minutes*

N/A

N/A

Willschk

e20

0516

Ilioingu

inal/ilioh

ypog

astric

nerveblockfollo

wing

indu

ctionwith

GA

Ingu

inal

hernia

repair,

orchidop

exy,or

hydrocelerepair

50:ultrasou

ndgrou

p50

:FCgrou

pGA:8%

sevofluranevia

facemask,

then

1MAC

halothanein

nitrou

soxide

with

O2

Levob

upivacaine

0.25

%variablevolumes

Powered

todetect50

%difference

between

2grou

psin

block

sufficiency(or

insufficiencyas

indicated

by910

%increase

inheart

rate

ormeanarterial

pressure

follo

wing

skin

incision

)

N/A

Low

erincidenceof

increasedheartrate

atskin

incision

for

ultrasou

ndversus

FC:6%

versus

22%*

Fewer

patientsneeding

additio

nalfentanyl

onskin

incision

forultrasou

ndversus

FC:4%

versus

26%*

Fewer

patientsrequiring

postoperativerectal

acetam

inophenin

ultrasou

ndversus

FC:

6%versus

40%*

Low

eram

ount

ofLA

needed

forultrasou

ndversus

FC:0.19

(0.05)

versus

0.3mL/kg*

Nocomplications

occurred

ineither

ultrasou

ndor

NSgrou

p

N/A

Oberndo

rfer

2007

17

Sciatic(allpatients)and

femoral(14patients)blocks

Surgery

ofon

elower

extrem

ity23

:ultrasou

nd23

:NS

Premedicationwith

oral

midazolam

0.5mg/kg

GA

indu

ced

with

sevo

flurane

8%viaface

mask,

1MAC

halothanein

nitrou

soxide

with

O2

Levob

upivacaine

0.5%

(NSgrou

p:0.3mL/kg;

ultrasou

ndgrou

p:variabledo

sage)

Powered

todetect

anincrease

inblock

duratio

nfrom

300to

450minutes

forNS

versus

ultrasou

ndgu

idance

N/A

N/A

Lon

gerdu

ratio

nof

analgesiain

ultrasou

nd*

versus

NS:50

8(178

)versus

335(169

)minutes

Low

ervolumeof

LA

needed

insciatic

and

femoralblocks

for

ultrasou

ndversus

NS:

0.2

(0.06)

versus

0.3

mL/kg,*and0.15

(0.04)

versu

s0.3

mL/kg,*

respectively

Nocomplications

ineithergrou

pdu

ring

block

performance

N/A

Abbreviations:FC,fascial

click;

GA,generalanesthesia;LA,localanesthetic;N/A,notapplicable;NS,nervestim

ulator;VAS,visualanalog

score.

*Pe.05in

statistical

assays

forsignificance.




TABLE

3.Ra

ndom

ized

Con

trolledTrialswith

Ultrasou

nd-G

uide

dLo

wer

Extrem

ityPe

riphe

ralN

erve

Bloc

k

Study

Groups(n:Technique)

Pow

erAnalysis

Block

Perform

ance

OnsetTim

eEfficacy

Com

plication

sPatient

Satisfaction

Casati

2007

18

Femoral

NBwith

preceding

sciatic

NB

Kneearthroscopy

30:Femoral

NBusingNS

30:Fem

oralNBusingultrasound

Sciatic:12

mL2%

mepivicaine,

doubleinjectionwith

NSusing

subglutealapproach

Femoral:variable

volumes

of0.5%

ropivacaine

Powered

todetect

3mL

difference

MEAV50

N/A

Nodifference

inpercent

ofpatientsshow

ing

incompleteblock

(requiring

intra-articular

infiltrationwith

intravenou

sfentanyl

supp

lement)after30

minutes:50

%of

grou

pultrasound

and56%

ofgroupNS

Low

erMEAV50,

and(SD)for

groupultrasound

versus

group

NS:15

(4)versus

26(4)m

L*

At24ho

urs,allpatients

show

edcomplete

recovery

ofsensory

andmotor

functio

ns.

Noneurological

complications

repo

rted

N/A

Dom

ingo

-Triado

2007

19

Sciatic

NBat

midfemoral

level

Foot

andanklesurgery

30:ultrasou

ndwith

NS(group

ultrasou

nd)31

:NSalon

e35

mL0.5%

ropivacaine

Powered

todetect

25%

difference

inthenu

mber

ofattempts

toperform

thetechniqu

e

Higherlevelo

fsuccessin

sciatic

nervelocationon

firstattempt

forgrou

pultrasou

ndversus

NS:

76.7%

versus

41.9%*

Nodifference

intim

eto

performtheb

lock

End

pointforblock

perfirmance:tim

efrom

firstn

eedleinsertionto

successfulnerve

locatio

norfrom

begginning

ofultrasound

techniqu

eto

successful

nervelocation

Nodifference

inon

settim

e,or

indu

ratio

nof

sensoryand

motor

block

Qualityof

sensoryblockand

toleranceto

tourniqu

etbetterin

grou

pultrasou

nd:96

.7%

versus

71%

achieved

completesensory

block,*

93.3%

versus

48.4%

toleratedthetourniqu

etwith

out

sedatio

n.*

No

difference

infailedblock

requ

iringspinal

anesthesia

with

ultrasou

nd(3%)

versus

NS(6.6%)

One

patient

had

neurop

athicpain

intheinnervationarea

ofthesciatic

1week

afterpu

ncture.Re

solved

in10

days

N/A

Marho

fer

1998

20

3-in-1

block

Hip

surgeryaftertrauma

20:ultrasou

nd(group

A),

20mL0.5%

bupivacaine

20:ultrasou

nd(group

B),

20mL0.5%

bupivacaine

20:ultrasou

nd(group

C),

30mL0.5%

bupivacaine

Not

performed

N/A

Sho

rter

onset(sensatio

nat

G30

%of

initial

value)

Ultrasound

versus

NS:13

T16

(group

A)versus27

T12

(group

B)

versus

26T13

(group

C)m

inutes*

Nodifference

incomplete3-in-1

blocks

(sensatio

natG30

%initial

value)

observed

inultrasou

nd(95%

)versus

NS(both80

%).

Nomotor

evaluatio

nQualityof

blockbetterin

grou

pA

than

grou

psBandCdu

ring

first

hour:finalsensationat

4T5%

ofinitialvalueversus

21T11

%and22

T19

%,respectively*

Nodifference

infailedblocks;

grou

pA

(5%),

grou

pB(10%

),grou

pC(5%)

Nocomplications

lasted

long

erthan

24ho

ursin

anypatients

N/A




in terms of type of block, anesthetic and analgesic agents, andcomparative control techniques. Most RCTs compared ultra-sound with nerve stimulator but other techniques includedfascial pops, transarterial, surface landmarks, and ultrasoundcombined with nerve stimulator. The use of the combinedtechnique may be especially difficult to evaluate, as it may beconfusing which endpoint (visual vs. stimulating current thresh-old) to accept if there is discrepancy.31 A further confoundingfactor for review was diversity in number of injections used forboth ultrasound and control techniques. Previous studies withnerve stimulator-guided peripheral nerve blocks have demon-strated increased efficacy with either multiple injections32,33 orspecific multinerve motor responses,34 yet not all RCTs usedmultiple injections or multinerve stimulation for the controlgroups, and may have thus artificially reduced the efficacy of thecontrol technique.13,14,19 Finally, many RCTs were performedin a limited number of institutions with access to and expertisewith ultrasound guidance, thus generalization of results to otherenvironments may be limited.

All included RCTs and the 3 included prospective caseseries reported success rates for upper extremity peripheralnerve blocks of 95% to 100% for ultrasound guidance. Thesesuccess rates were similar (95%Y100%) to use of nervestimulator-guided upper extremity blocks in the includedRCTs for review, and from previously published much largerprospective case series (300Y700 patients) using nerve stimu-lator for upper extremity peripheral nerve blocks.35,36 Othertechniques, such as transarterial and surface landmarks, were notconsistently compared in more than 1 RCT. Only 1 RCT wasperformed in pediatric patients with similar lack of differencein anesthetic efficacy but with a prolonged duration of post-operative analgesia (È70 extra minutes).15 As mentioned, only2 small (e200 patients) prospective case series were identifiedfor ultrasound-guided supra-clavicular and infraclavicularblocks. No RCTs or large, prospective case series were identifiedfor ultrasound-guided perineural catheters.

There were even fewer data for lower extremity peripheralnerve blocks. Only 3 RCTs and 1 MEAV study in adults wereidentified. Success rates were 90% to 97% with use of ultra-sound or nerve stimulator. This is consistent with a previouslarge prospective case series for nerve stimulator-guided sciaticblocks that reported 97% success rate in 500 patients.37 TwoRCTs with pediatric patients were identified; they reportedimproved postoperative analgesia with use of ultrasound forlower extremity and inguinal hernia and urologic surgery. Nolarge prospective case series was identified for ultrasound-guided lower extremity peripheral nerve blocks. No RCTs orlarge prospective case series were identified for ultrasound-guided perineural catheters.

None of the epidural RCTs showed reduced failure ratesfrom addition of ultrasound guidance. Use of ultrasoundprescanning in parturients consistently reduced the number ofpunctures, and number of vertebral interspaces attempted. How-ever, almost all of these RCTs were performed entirely by asingle operator and may have limited applicability to otherclinicians. The largest (150/group) of these RCTs did report aprobably clinically insignificant reduction in pain scores (0.8 vs.1.3) during labor or Cesarean delivery (both were analyzedtogether) with ultrasound prescanning.24 One small RCT with10 subjects per group did not report an advantage for real timescanning versus prescanning with ultrasound for obstetricalcombined spinal epidural analgesia.28 Another RCT reportedfaster learning curves for residents with prepuncture ultra-sound scanning, but the control learning curve lagged behindpreviously reported learning curves for residents learningM

arho

fer

3-in-1

block

Not

Performed

N/A

Sho

rter

onsetforultrasou

ndversus

NS:Nodifference

infailed

Norecorded

N/A

1997

21

Hip

surgeryaftertrauma

16T14

versus

27T16

block:

ultrasou

nd(5Q)

complications

20:ultrasou

ndminutes*

versus

NS(10Q

)after24

hours

20:NS

Nodifference

incomplete3-in-1

20mL0.5Q

bupivacaine

block(sensatio

nat

G30

initial

value)

observed

inultrasou

nd(95Q

)versus

NS(85Q

).Nomotor

evaluatio

nBetterqu

ality

ofblockforperiod

after30

to60

minutes

inultrasou

nd10

Qversus

27T14Q

ofinitial

value*

Abbreviations:M

EAV50,m

inim

umeffectiveanestheticvolumeof

ropivacaine0.5%

providingadequatesurgicalblockof

thefemoralnervewith

in30

minutes

in50

%of

patients;N/A,notapplicable;N

B,

nerveblock;

NS,nervestim

ulator.

*Pe.05in

statistical

assays

forsignificance.




traditional loss of resistance epidural placement.38 The pediatricepidural study also reported no differences in failed blocks.29 Nolarge prospective case series was identified for adults. One caseseries was identified for pediatrics. Prepuncture scanning re-sulted in a 99% success rate of locating the epidural space withfirst puncture attempt. This success rate is better than a 91%success rate reported for epidural localization with a 17-gaugeneedle loss of resistance technique (number of attempts notspecified)39 and a 94.3% first attempt success rate observed withstaff anesthesiologists locating the epidural space with the Bdripand tube method.[40

Does Ultrasound Guidance Offer OtherPotential Benefits?

Faster block performance or fewer needle passes.Consistently, RCTs for ultrasound-guided peripheral nerveblocks report that blocks can be performed more quickly thanwith nerve stimulator (approximately 3 minutes),9Y11,13,14 withfewer needle passes,8,19 and less discomfort.14,15 All RCTs forepidural blocks also reported fewer attempts, fewer needlepasses, or faster performance with prepuncture scanning or realtime scanning and analysis (Table 5). Although these findingswould seem inherently advantageous, only 2 of the 5 RCTs thatmeasured satisfaction noted a statistically significant differencebetween groups.8,12,24,26,28 We note that none of these studiesconsidered satisfaction to be a primary outcome, and were notpowered to determine a difference in this outcome.

Faster initial onset of block. Overall, ultrasound resultedin faster onset of block and more complete block during earlymeasurement periods (e30 minutes) after upper and lowerextremity peripheral nerve blocks.8Y10,12,14,15,19Y21 This findingmay be explained by closer approximation of the needle andlocal anesthetic solution to the nerves with use of ultrasound. Asnoted above, this enhanced onset of block with ultrasound didnot ultimately reduce incidence of failed blocks requiring con-version to general anesthesia. This apparent discrepancy may bedue to the additional onset time allowed to all block techniqueswith patient transport, positioning, and surgical preparation.

Reduced dose of local anesthetic. Four included RCTsreported reduced need for dose of local anesthetic.16Y18,20 Noneof the studies was a rigorous dose response comparison sointerpretation is difficult. It is tempting to speculate that abilityof ultrasound to closely approximate the needle to the targetnerve would allow a reduction in dose of required local anes-thetic. If proven, this may be a safety advantage for reduced riskof toxic systemic reactions to local anesthetics. However, thismay be a theoretical advantage as a recent large scale prospec-tive surveillance study of 158,000 regional anesthetics reportedno cardiac arrest and 7 seizures (0.004% incidence) due to localanesthetic toxicity.41

Does Ultrasound Guidance Reduce Risk of NerveInjury From Regional Anesthesia and Analgesia?

A potential advantage is that direct visualization of a needlewith ultrasound should help prevent intraneural puncture andinjection of local anesthetic with resultant reduction in risk ofneural injury. This may be especially relevant for peripheralnerve blocks, as recent studies suggest that intraneural injectionsmay frequently occur with a fascial pop technique,42 and thatreliance on a minimum stimulating current of 0.3 mA to 0.5 mAwith a nerve stimulator may not identify intraneural or very closeperineural needle placement.31,41,43,44 However, current evi-dence is insufficient to answer this question. Virtually no RCTsor prospective case series observed any persistent complications,but the subject numbers for each study are too small for mean-ingful extrapolation to various block locations. Similarly, in theepidural studies, permanent injury was not identified in anypatients, with or without ultrasound. However, only 1 small epi-dural study used real time scanning to identify position of theneedle during block performance. Current estimates of perma-nent nerve injury after peripheral nerve blocks range from0.03%41 to 3%45 depending on location of block, and wouldrequire 3,068 patients in a randomized trial to determine a 50%reduction from 3% to 1.5%, and 91,200 patients in a case se-ries to determine a 95% confidence interval of 1% for thetrue incidence of a studies technique. Estimates for permanent

TABLE 4. Large (n 9 100) Case Series of Ultrasound-Guided Peripheral Nerve Block

StudyType of Block and

Specifics Block Performance

Efficacy (NotRequiringGeneral

Anesthesia)

Efficacy (NotRequiring

SupplementalAnalgesics) Complications

Sainz Lopez200623

n = 200 (all by author) Not applicable 98% (95% CIof96Y99%)

97% (95% CIof95Y99%)

No persistent complicationsbut unspecifiedobservation period

Supraclavicular block 3injection

Hand and elbowsurgery

10 mL 2% mepivacaineSandhu200222

n = 126 10 T 4.4 minutes (timefrom imaging to end ofinjection)

98% (95% CIof 95Y99%)

93% (95% CIof88Y97%)

No complications within24 hoursInfraclavicular block 3

injectionComplete sensory andmotor block 6.7 T 3.2minutes

Hand, forearm, and AVfistula surgery

33 mL 2% lidocainewith epinephrine1: 200,000 andNaHCO3 (0.9 mEq/10 mL)

Abbreviation: CI, confidence interval; AV, arterio-venous.




TABLE

5.Ra

ndom

ized

Con

trolledTrialsan

dCaseSe

rieswith

Ultrasou

nd-G

uide

dEp

idural

Ane

sthe

sia/Ana

lgesia

inAdu

ltsan

dChildren

Study

Groups(n:Technique)

Pow

erAnalysis

Block

Perform

ance

OnsetTim

eEfficacy

Com

plication

sPatientSatisfaction

Grau2004

28

Obstetric

epidural

anesthesia

Not

performed

Greater

levelo

fsuccessin

reaching

theepidural

spaceon

thefirstattempt

inonlineultrasound

groups

versus

control:100%

versus

40%*

Elapsed

timebetween

injectionandfirst

effectsor

complete

bloc

kshow

edno

differencesacross

the3

groups

Incidenceof

failedblocks

notreported

Nodifference

intheincidenceof

headache

orbackache

after

CSEacross

the3groups

Nodifference

inpatient

satisfactionwith

the

epiduralanesthesiaacross

the3groups:1.65

T0.74

(control)versus

1.35

T0.57

(offlin

e)versus

1.2T

0.42

(online)

ona

satisfactionscaleof

1(verygood)to

6(insufficient)

10:CSE(control)

Overall,

fewer

punctureattemptsinboth

ultrasound

groups

versus

control:10

(online)

and

13(offlin

e)versus

18*

Nodifference

inaverageVASduring

the

operationacross

the3

groups:0.7T0.94

(control)versus

0.3T

0.94

(offlin

e)versus

0.3T1.63

(online)

10:CSEwith

offline

prepuncture

ultrasound

scan

(offlin

e)

Fewerinterspaces

puncturedbefore

successful

locatio

nof

the

epidural

spacein

online

versus

control:0versus

5patientsrequiring

achange

ofpuncturesite*

10:CSEwith

onlin

eultrasound

imaging

during

epidural

puncture

(online)

All

blocks

wereperformed

bytheauthor,T

.G.

Spinal:1.5mL

bupivacaine0.5%

Epidural:7.5mL

bupivacaine0.5%

plus

10Kg

sufentanil

Grau2003

25

Obstetric

epidural

anesthesia

Not

Performed

Improvem

entin

successrate

ofepidural

anesthetic

inCG

versus

UG

after60

cases:60

T15%

upto

84T25%

versus

86T15%

upto

94T9%

*

N/A

N/A

N/A

N/A

10residents(5/group)

wereassigned

toperform

theirfirst

60obstetric

epiduralseither

with

orwith

out

prepunctureultrasound

imaging

Success:adequate

obstetricepidural

anesthesiawith

in3

attempts;VASG1

during

entireprocedure;

nointerventio

nfrom

asupervisor

300:

LORtechnique

(CG)

300:

LORtechniquewith


imagingof

puncture

area

(UG)

Grau2002

24

Obstetric

epidural

anesthesia

Not

performed

Low

eraverage

numberof

puncture

attempts

needed

forsuccessful

epiduralspace

cannulationin

UG

versus

CG:1

.3T0.6

versus

2.2T1.1

attempts*

Nodifference

betw

een

UG

and

CG

inonsetfrom

injectionto

completeblock

Nodifference

infailed

blocks

0%UG

versus

1%CG

Lessfrequent

postpartum

headache

andbackache

inUG

versus

CG:33(22%

)versus54

(36%

)patients*

Higherlevelofsatisfactionin

anesthesiaprocedureinU

Gversus

CG:1.3T0.5versus

1.8T0.9on

asatisfaction

scaleof

1(verygood)to6

(insufficient)*

150:

LORtechniquewith


imagingof

puncture

area

(UG)

Fewer

intervertebral

spaces

puncturedbefore

successfulidentificationof

theepidural

spacein

UG

versus

CG:1

.1T0.4

versus

1.3T0.6*

More

cases

ofcomplete

analgesiain

UG

versus

CG:147versus

138

patients*

(Con

tinuedon

next

page)




150:

LOR,(CG)

Fewer

catheter

advancem

ent

attemptson

averageinUG

versus

CG:1.3

T0.6

versus

2.1T1.1tim

es

Low

ermaxim

umVAS

inUG

versus

CG:0.8T

1.5versus

1.3T2.2*

Bothgroups:85

labor

analgesia,65

cesarean

section

Allblocks

wereperformed

bytheauthor,T.G.

Com

pletemotor

blockin

100%

ofpatientsinboth

groups

Laboranalgesia:11

to15

mLof

bupivacaine2.5mg/mLplus

10Kgsufentanil

Cesareansection:14

to16

mLof

bupivacaine5.0mg/mLplus

20Kgsufentanil

Grau2001

26

Obstetric

epidural

anesthesia

Not

performed

Fewer

puncture

attempts

madein

ultrasound

versus

CG:1.15

T0.9

versus

2.6T1.4*

N/A

No

difference

infailed

blocks:0%

ultrasound

versus

5%CG

N/A

Higherlevelof

satisfactionin

anesthesiaprocedurein

ultrasoundversus

CG:1.3T

0.5versus

2.1T1.3on

asatisfactionscaleof

1(very

good)to6(in

sufficient)*

36:LORtechnique

with

prepuncture

ultrasound

scan

(ultrasound

group)

Fewer

intervertebral

spaces

punctured

before

successfully

reaching

the

epidural

spacein

ultrasound

versus

CG

(1.3

T0.5vs.

1.5T0.7)*

Maxim

umVAS

during

laborwith

epidural

anesthesia

lower

inultrasound

versus

CG:0.8

T1.4

versus

1.8T2.7*

36:LORtechnique

alone(CG

group)

Fewer

catheter

advancem

ent

attemptsin

ultrasound

versus

CG:1.1T0.4

versus

1.3T0.6*

10to

13mL

bupivacaine0.25

mg/mLplus

10Kg

sufentanil

Allblocks

wereperformed

bytheauthor,T.G.

Grau2001

27

Obstetric

epidural

anesthesia

for

Cesareansection

Not

performed

Highersuccessrate

inlocatin

gtheepidural

spaceon

thefirsttryin

ultrasound-CSEversus

CSE:75%

versus

20%.*

N/A

N/A

N/A

N/A

40:CSE

Athirdattempt

was

needed

in1patient

for


8patientsforCSEalone

(3%

vs.20%)*

40:CSEwith

prepuncture

ultrasound

imaging

(ultrasound-CSE)

Fewer

interspaces

puncturedbefore

successful

locatio

nof

theepidural

spacein


CSE:versus

6patients

requiringachange

ofpuncture

site*

Spinal:1.5mL

bupivacaine0.5%

Allblocks

wereperformed

bytheauthor,T

.G.

Epidural:7.5mL

bupivacaine0.5%

plus

10Kgsufentanil

Patients

Study

Groups(n:Technique)

Pow

erAnalysis

Block

Perform

ance

OnsetTim

eEfficacy

Com

plication

sSatisfaction

TABLE

5.(con

tinued)




neurologic injury after central neuraxial block range from 0.02%to 0.0009%45 and would require even more subjects for adefinitive RCT or case series.

CONCLUSIONS AND FUTURE DIRECTIONSCurrent evidence is sparse and suggests that use of

ultrasound for peripheral nerve blocks hastens block perfor-mance and onset of block, however onset of surgical anesthesia,and need for conversion to general anesthesia is not significantlyaffected. There are several limitations inherent to this systematicqualitative review. New technologies, such as ultrasound, mustbe mastered through practice and shared experience. Adoptiontherefore often precedes the best evidence of benefit, as manyyears of trial (and sometimes error) are required before Bbest[use of a technology is determined. Rapid improvement of thetechniques using the new technology over time makes compar-isons using older literature difficult. Also, practitioner experi-ence with the new technology will initially be less than withestablished ones, further confounding many attempts at com-parison. Thus, additional well designed RCTs or appropriatelyperformed meta-analyses would be welcome to confirm ourimpressions.

As block or epidural success rates are high (990%) withconventional techniques, future RCTs would need to be appro-priately large and sufficiently powered in order to examine apotential difference in efficacy as a primary outcome. RCTs forperineural catheters are completely lacking and should beperformed with primary outcomes of time required to place thecatheter, and success of catheter in terms of need to convert toalternative analgesic technique. Central neuraxial RCTs outsideof the obstetric or pediatric population are entirely lacking.Additional epidural studies are needed in all patient populationswith meaningful primary outcomes, such as improved analgesia,or fewer failures. Ideally, future epidural studies would blind thesubjects and the data collector to group assignment. Large(hundreds to thousands of patients) prospective case series arelacking and would be useful for all techniques to define popula-tion rates of efficacy, and complications from use of ultrasound.Generation of such evidence is an ambitious task and may ormay not ultimately affect acceptance and popularity of ultra-sound. We note that there are no previously published data toshow conclusive superiority of neurostimulation in terms ofblock success or safety, yet this has become a common standardof regional anesthesia practice today. The same analogy mayextend to ultrasound. It is conceivable that a difference in blockoutcome cannot be demonstrated for ultrasound in the hands ofthe regional anesthesia experts, yet popular preference mayultimately launch ultrasound as the preferred technique.

Finally, several potential patient-oriented benefits may beassociated with ultrasound, such as faster block performance,fewer needle passes, and less discomfort and minor side effectsfrom block performance. Additional potential yet poorly definedbenefits from ultrasound guidance may include: (1) an increasein the practice of peripheral nerve blocks, even in the hands ofthe trainees and occasional regional anesthesia practitioners; (2)understanding of why blocks fail as judged by local anestheticspread; (3) avoidance of an unintentional intravascular injection;(4) avoidance of an unintentional pleural and vascular puncture;(5) early detection of an early intraneural injection; (6) recogni-tion or avoidance of an unintentional intramuscular and intra-peritoneal injection; and (7) an understanding of inconsistentmotor response associated with electrical stimulation. We en-courage future studies which examine and quantify these impor-tant patient-oriented and more qualitative outcomes. AlthoughW

illschke

2006

29

Pediatricepidural

catheterplacem

ent

Not

performed

Epiduralcathetersplaced

more

swiftlyintheultrasound

groupthan

intheLOR

group:

162T75

versus

234T138seconds*

N/A

N/A

Noduralpuncture

occurred

ineither

group

N/A

Childrenfrom

neonateto

6years

Bonecontactoccurred

infewer

child

renfor

ultrasound

vs.L

OR:17%

versus

71%*

32:ultrasound-guided

catheter

placem

ent

32:LORcatheter

placem

ent

Major

abdominal

orthoracic

surgery

Levobupivacaine

0.25%

0.2mL/kg

Kil2007

30

Pediatricepidural

anesthesia

Not

performed

Epiduralspacelocated

upon

firstpuncture

attempt

in179of

180

cases(99.4%

)

N/A

N/A

Noincidences

ofduralpuncture,

bloody

tap,

orpostoperative

complications

relatedto

epidural

cannulationoccurred

N/A

n=180,aged

2to84

months

Urologicsurgery

Abbreviations:CG,control

group;

CSE,combinedspinal-epidural;LOR,loss-of-resistance;N/A,notapplicable;UG,ultrasound

group;

VAS,v

isualanalog

score.

*Pe.05in

statistical

assays

forsignificance.




potentially fruitful, it is important to note that validatedinstruments to measure patient-oriented outcomes are lacking,and should also be developed in concert.46

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2. De Tran QH, Clemente A, Doan J, Finlayson RJ. Brachial plexus blocks:a review of approaches and techniques. Can J Anaesth. 2007;54:662Y674.

3. Marhofer P, Chan VW. Ultrasound-guided regional anesthesia: currentconcepts and future trends. Anesth Analg. 2007;104:1265Y1269.

4. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regionalanaesthesia. Br J Anaesth. 2005;94:7Y17.

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