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TRANSVERSUS ABDOMINIS PLANE (TAP) BLOCK
By Karim Mukhtar, MB BCh, MSc, FRCA
Royal Liverpool and Broadgreen University Hospitals, Liverpool U.K.
Abd o min al field blocks h ave b een arou n d f or a lon g time an d h ave b een exten sively use d as th ey
are mostly tech nically unch allen gin g. Th ey, h ow ever, provide limited an algesic fields, h en ce multiple
injections are usu ally required. Tradition ally th ese blocks h ave blin d en d poin ts (pops) makin g th eir
success unpredictable.
Th e description of th e lan dmark techniqu e f or performin g transversu s abdominis plan e (TAP) block
advoc ate d a sin gle en try poin t, th e trian gle of Petit, to access a n u mber of abd o min al w all n erves
h en ce providin g more w idespread an algesia . (1) More recen tly, ultrasou n d guided TAP block h as
be en describe d w ith pro mises of better localization an d de position of th e local an aesth etic with
improved accuracy (2).
The Journal of NYSORA 2009; 12: 28-33
TRANSVERSUS ABDOMINIS PLANE (TAP) BLOCK
INTRODUCTION
Abdominal field blocks have been around for a
long time and have been extensively used as they are
mostly tech nically u n ch allen gin g. Th ey, h ow ever, provide
limited analgesic fields, hence multiple injections are
usu ally required. Tra dition ally th ese blocks h ave blin d en d
points (pops) makin g their success unpredicta ble .
The description of the landmark technique for
performing transversus abdominis plane (TAP) block
advocated a single entry point, the triangle of Petit, to
access a number of abdominal wall nerves hence
providin g more w idespre a d an algesia . (1) More recen tly,
ultrasound guided TAP block has been described with
pro mises of better localization an d d ep osition of th e local
anaesth e tic with improve d accur acy (2).
arises from the anterior rami of spinal nerves T7 to L1.
These include the intercostal nerves (T7 -T11), the
subcostal nerve (T12), and the iliohypogastric and
ilioinguinal nerves (L1).
Anatomy
Innervation of the anterolateral abdominal wall
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Figure 1. Cutaneous innervation of the abdominal wall .
Coloured region is mostly blocked by a single injection
posterior TAP block.
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TRANSVERSUS ABDOMINIS (TAP) BLOCK
Th e anterior divisions of T7-T11 con tinu e from th e
intercostal spac e to en ter th e ab do min al w all betw een th e
intern al obliqu e an d transversu s ab do minis mu scles u ntil
th ey reach th e rectus abdominis, which th ey perforate an d
su pply, en din g as an terior cutan e ou s bran ch es su pplyin g
the skin of the front of the abdomen. Midway in their
course th ey pierce th e extern al obliqu e mu scle givin g off
th e lateral cu tan eou s bran ch w hich divides in to an terior
an d post erior bran ch es th at su pply th e extern al o bliqu e
muscle and latissmu s dorsi respectively.
Th e an terior bran ch of T12 co mmu n icates with th e
iliohypogastric n erve an d gives a bran ch to th e pyramidalis.
Its lateral cutaneous branch perforates the internal and
extern al obliqu e mu scles an d d escen ds over th e iliac crest
and supplies sensation to the front part of the gluteal
region.
Th e ilioh ypogastric n erve (L1) divides betw een th e
intern al obliqu e an d tran sversu s ab do minis n ear th e iliac
crest into lateral and anterior cutaneous branches, the
former su pplyin g part of th e skin of th e gluteal region while
the latter supplies the hypogastric region .
Th e ilioin guin al n erve (L1) co mmu nicates with th e
iliohypogastric nerve between the internal oblique and
tran sversu s abd o minis n e ar th e an terior part of th e iliac
crest. It su pplies th e u pper an d medial part of th e thigh an d
part of the skin coverin g the genitalia.(3)
Block Technique
Figure 2. T7 to T12 spinal nerves pathway and branches in
the abdominal wall
Blind TAP
The point of entry for the blind TAP block is the lumbar
trian gle of Petit. Th is is situ ate d betw e en th e low er costal
margin an d iliac crest. It is boun d an teriorly by th e extern al
obliqu e mu scle an d posteriorly by th e latissmis dorsi. Th is
technique relies on feeling double pops as the needle
traverses th e extern al obliqu e an d intern al obliqu e muscles.
A blunt needle will make the loss of resistance more
appreciable.
The aim of a TAP block is to deposit local
an aesth etic in th e plan e b etw een th e in tern al obliqu e an d
transversus abdominis mu scles targetin g th e spin al n erves
in this plan e. Th e inn ervation to ab do min al skin , mu scles
and parietal peritoneum will be interrupted. If surgery
traverses the peritoneal cavity, dull visceral pain (from
spasm or inflammation f oll owin g surgical insult) will still be
experien ced. Th e block can be perf ormed blin d or u sin g
the ultrasound
Figure 3. Lumbar triangle of Petit between external
oblique muscle and latissmis dorsi.
CM: costal margin, IC: iliac crest.
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Ultrasound- guided TAP
The ultrasound probe is placed in a transverse
plan e to th e lateral abd o min al w all in th e midaxillary lin e,
betw een th e low er costal margin an d iliac crest. Th e u se of
ultrasound allows for accurate deposition of the local
anaesth e tic in the correct neurovascular plane.
If prolon g ed analgesia is required beyon d the
duration of a single shot of local anaesth etic , a catheter
can be introdu ce d into the transversus abdominis plane
through a touhy needle. After opening up the plane with 2
ml of saline, the catheter is introduce d aroun d 3 cm
beyond the needle tip . Position is verified by injecting the
local anaesth etic bolus (20ml). An infusion of a dilute local
anaesth e tic is started at a rate of 7 to 10 ml per hour.
TRANSVERSUS ABDOMINIS (TAP) BLOCK
Performing the ultrasound-guided block
Requirements
-Ultrasou n d machin e with a high frequ en cy probe (10-5
MHz)
-Ultrasound probe cover
-Antiseptic for skin disinfection
-Sterile ultrasound gel
-Needle: 50 mm or 80 mm needle
-20ml needle and injection tubing
-20 to 30 ml local anaesthetic (any local anaesthetic
concen tration , this block relies on local an aesth etic spread
rather than concen tration ,i.e. is volume depen dan t.)
Indications
This block is indicated for any lower abdominal
surgery inclu din g appen dectomy, h ernia repair, caesarean
section (4), abdomin al hysterectomy (5) and prostatectomy
(6). Efficacy in laparoscopic surgery has also been
demon strated (7). Bilateral blocks can be given f or midlin e
incision s or laparosc opic surgery. C are sh ou ld b e tak en
not to exceed recommended safe doses of local
anaesth e tic agent with bilateral injection s.
There has been controversy in the literature
regarding the spread and level of block achieved with a
sin gle TAP in jection . Wh ilst early stu dies sh ow ed a T7 t o
L1 spread with a sin gle posterior injection makin g th e block
suitable f or midlin e abd o min al in cision s (8), oth er stu dies,
h ow ever, f ailed t o d e mon strate a s prea d ce ph alad to T1 0
makin g it more suited for lower abdomin al surgery (9).
Figure 4. Schematic view of an ultrasound-guided
tranaversus abdominis plane block. EO: external
oblique, IO: internal oblique, TA: transversus
abdominis, LA: local anaesthestic
In a small ca dav eric stu dy, T1 1, T1 2 an d L1 w er e
most con sisten tly presen t in th e tran sversu s ab d o min is
plan e, while T10 w as present in 50% of th e cases (10). It is
reason able to expect a g oo d an algesic eff ect in th e region
betw e en T10 an L1 f ollowin g a sin gle posterior in jection .
Au g men tation with a su bcost al in jection will h elp attain a
high er block u pto T7. Th e su bcostal TAP is a modification
of th e origin al techniqu e in w hich th e ultrasou n d pro be is
placed ju st ben eath th e costal margin an d parallel to it. Th e
needle is th en introduced from th e lateral side of th e rectus
mu scle in plan e of th e ultrasou n d b ea m an d 10 ml of local
injected in to th e tran sversus abdominis plan e to exten d th e
an algesia provide d by th e p osterior TAP block ab ove th e
umbilicus (11).
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T ECHNIQUE
Whilst the patien t is in the supine position , a high frequen cy ultrasou n d probe is placed transverse to the
abdomin al wall betw een the costal margin and iliac crest.
The image produced shows (from above downwards) skin, subcutaneous tissue, fat, external oblique, internal
oblique, transversu s abdominis. The peritoneu m and bowel loops may also be visualized deeper to the muscles.
Figure 6. Image of the abdominal wall. E0: external oblique, IO: internal oblique, TA: transversus abdominis
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TRANSVERSUS ABDOMINIS (TAP) BLOCK
Th e n eedle is in trodu ced in plan e of th e ultrasoun d probe directly un der th e probe an d advanced un til it reach es
th e plan e betw e en th e in tern al obliqu e an d tran sversu s a bd o minis mu scles. Th e n e edle can also be in tro du ced a f ew
cen timeters medial to th e prob e (a distance e quivalen t to th e de pth of th e plan e as view ed on th e ultrasou n d i ma g e).
Th e pro be w ill h ave to f ollow th e n ee dle en try poin t me dially in its su perficial path an d is th en return ed to its origin al
position in the midaxillary line as the needle is directe d deep er.
U pon reachin g th e plan e, 2 ml of salin e is in jected to confir m correct n ee dle position after which 20 ml of local
an aesth etic solution is in jected. Th e tran sversus abdominis plan e is visu alized expan din g with th e in jection ( appears as
a hypoechoic space).
Figure 7. Correct local anaesthetic deposition in the transversus abdominis plane.
CLICK HERE TO VIEW VIDEO OF THIS TECHNIQUE.
Complications
Th er e h ave b een n o rep orted co mplication s to d ate w ith th e ultrasou n d gu ided t ech niqu e. A f ew complication s h ave
been reported with blin d TAP block, th e most significant of which w as a case report of in trah epatic injection (12). Other
complication s inclu de: intraperiton eal in jection , bow el h emato ma an d tran sien t femoral n erve palsy . Local an aesth etic
toxicity could also occur du e to th e large volu mes required to perf or m this block especially if it w as don e bilaterally. As
with any regional technique, careful aspiration will help avoid intravascular injections.
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TRANSVERSUS ABDOMINIS (TAP) BLOCK
R EFERENCES
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Website:
www.heartw e b.com.a u/d ow nloa ds TAPblock.pdf
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274-5.
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