ANZCA Bulletin June 2011 - Australian and New Zealand College of ...

Illuminating the intervertebral
abyss with neuraxial ultrasound
continued
In the past I have received comments
that anaesthetists tried the technique
for the first time on a morbidly obese
patient and they could not identify
any structures and therefore they did
not find it useful. My response is that
this practice is not helpful. We found
that it is important to start practicing
by scanning thin patients with easy
sonoanatomy. This is imperative in
order to master the skill.
I am of the view that anyone can
confidently perform an epidural
ultrasound scan. It is as simple as
scanning from the sacrum upwards and
when the desired interspace is identified
turning the probe transverse. This is
facilitated by pattern-recognising two
images – in the paramedian (sagittal)
oblique view a “sawtooth” pattern and
in the transverse view a “flying bat” 8 .
Ultrasound was discovered by Lazarro
Spallanzani in 1790 when he found that
bats navigate with their ears rather than
eyes in flight. One could argue tonguein-cheek
that ultrasound has now
come full circle with the development
of epidural ultrasound as we are
looking for pictures of flying bats when
performing the scan.
Preprocedural ultrasound is particularly
useful for:
• Identifying the exact interspace that the
procedure is performed at. Research
has shown that anaesthetists who
employ landmark techniques are
only correct 30 per cent of the time in
predicting the lumbar interspace in
comparison to a criterion standard.
Ultrasound can more than double
this accuracy 9 .
• Measuring the distance from the skin
to the ligamentum flavum. Studies
have shown good correlation between
ultrasound measurement and actual
needle depth not only for the lumbar
spine, but also the thoracic and
cervical spine 1,10,11 . I routinely use
ultrasound to facilitate placement of
thoracic epidurals. The implication
of this is that you can more easily
anticipate when the needle will
penetrate the ligamentum flavum
when you are performing an epidural
and also if a longer than standard
needle is required in a morbidly obese
patient.
• Identify the needle insertion point. It
is important to note that this requires
meticulous skin marking.
• Recognising scoliosis via identifying
assymmetrical intervertebral spaces.
If possible, perform the puncture on
a symmetrical intervertebral space.
• The angle of the puncture by
noting the angle of the probe
while identifying all the important
structures.
• Recognising a preserved interspace in
patients with previous back surgery 12 .
• Feasibility of performing a neuraxial
technique. If it is not always possible
to recognise the important vertebral
structures especially in patients with
vertebral deformities and previous
back surgery. An ultrasound scan
might inform your decision-making
process with regards to proceeding
with the procedure safely. It is also
important to note that not all patients
have good images on ultrasound
depending on their body water or
habitus and the resolution of the
equipment. Fortunately parturients
have increased total body water,
which can improve image quality.
Karmakar et al described a novel
real-time technique for performing
ultrasound guided epidurals 13 .
Although it has some promise, it is still
problematic to perform this technique as
a single operator in advanced cases. The
area of real-time epidurals is currently
the focus and future of advances in
the field and it remains to be seen if
3D ultrasound will be helpful.
In Australia and New Zealand we
are international leaders in using
ultrasound for limb and trunk blocks
and also for performing heart scans.
However, the pace of extending
ultrasound to neuraxial anaesthesia
has been slow. Although serious
complications are low when performing
these techniques, obesity presents us
with a fresh challenge.
I believe that the time is ripe for
neuraxial ultrasound to blossom and,
in particular, that mothers will in
future receive an ultrasound scan when
requesting an epidural. Therefore, I
propose that neuraxial procedures no
longer have to be the proverbial stab
into a dark intervertebral abyss.
Dr Nico Terblanche, FANZCA
Royal Hobart Hospital, Hobart,
Tasmania
References:
1. Arzola C, Davies S, Rofaeel A, Carvalho
JC.Ultrasound using the transverse
approach to the lumbar spine provides
reliable landmarks for labor epidurals.
Anesth Analg 2007; 104:1188-92.
2. Balki M, Lee Y, Halpern S, Carvalho JC.
Ultrasound imaging of the lumbar spine
in the transvers plain: the correlation
between estimated and actual depth of
the epidural space in obese parturients.
Anesth Analg 2009; 108:1876-81.
3. Watterson LM, Hyde S, Bajenoy S,
Kennedy SE. The training environment
of junior anaesthetic registrars learning
epidural labour analgesia in Australian
teaching hospitals. Anaesth Intensive Care
2007;35:38-45.
4. Grau T, Bartusseck E, Conradi R, Martin
E, Motsch J. Ultrasound imaging improves
learning curves in obstetric epidural
anesthesia: a preliminary study. Can J
Anaesth 2003; 50 :1047-50
5. Terblanche N, Lawson R, Blackford D,
Oeder V. Ultrasound imaging of the
obstetric epidural space: validation of
a training programme. SOAP 2010;
Abstract: 288.
6. Deacon A, Melhuis N, Terblanche N.
The learning curve of lumbar epidural
ultrasonography – when is competency
reached SOAP 2010; Abstract: 271.
7. Margarido CB, Arzola C, Balki M, Carvalho
JC. Anesthesiologists’ learning curves
for ultrasound assessment of the lumbar
spine. Can J Anaesth 2010; 57: 120-6.
8. Carvalho JC. Ultrasound-facilitated
epidurals and spinals in obstetrics.
Anesthesiol Clin 2008; 26:145-58.
9. Watson MJ, Evans S, Thorp JM. Could
ultrasonography be used by an
anaesthetist to identify a specified lumbar
interspace before spinal anaesthesia Br J
Anaesth. 2003; 90: 509-11.
10. Grau T, Leipold RW, Delorme S, Martin
E, Motch J. Ultrasound imaging of the
thoracic epidural space. Reg Anesth Pain
Med 2002; 27:200-6.
11. Kim SH, Lee KH, Yoon KB, Park WY, Yoon
DM. Sonographic estimation of needle
depth for cervical epidural blocks. Anesth
Analg 2008; 106:1542-7.
12. Costello JF, Balki M. Cesarean
delivery under ultrasound-guided
spinal anesthesia in a parturient
with poliomyelitis and Harrington
instrumentation. Can J Anesth 2008: 55;
606-611.
13. Karmakar MK, Li X, Ho AM, Kwok WH,
Chui PT. Real-time ultrasound-guided
paramedian epidural access: evaluation
of a novel in-plane technique.
Br J Anaesth 2009; 102: 845-54.
Acknowledgements:
Roger Wong (photography) and Katrina
Webster (pregnant model).
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ANZCA Bulletin June 2011