ultrasound guidance - The Global Regional Anesthesia Website

72 Pages·2012·6.5 MB·English

UltrasoUnd
GUidance
for Vascular Access
and Regional Anesthesia
Brian a. Pollard, md, med
ULTRASOUND
GUIDANCE
for Vascular Access
and Regional Anesthesia
Brian A. Pollard BSc, MD, MEd, FRCPC
www.usrabook.com
Illustrations by Diana Kryski, MScBMC
www.kryski.com
Book Design and Layout by John Beadle
www.john-beadle.com
Library and Archives Canada Cataloguing in Publication
Ultrasound Imaging for Vascular Access and Regional Anesthesia
Brian A. Pollard BSc, MD, MEd, FRCPC
© 2012
All rights reserved. The contents of this book, in whole and in part, through any reproduction, are
copyright of Brian A. Pollard, BSc, MD, MEd, FRCPC, and Ultrasonix Medical Corporation. The
illustrations in this book, in whole and in part, through any reproduction, are copyright of Diana
Kryski, MScBMC. Use in connection with any form of electronic adaptation, computer software, or
by similar or dissimilar methodology now known or hereafter developed is forbidden.
The use in this publication of trade names, trademarks, service marks, and similar terms, even if
they are not identified as such, is not to be taken as an expression of opinion as to whether or not
they are subject to proprietary rights. While the advice and information in this book are believed
to be true and accurate at the date of going to press, neither the author, Ultrasonix Medical
Corporation, nor the publisher can accept any legal responsibility for any errors or omissions that
may be made, and make no warranty, express or implied, with respect to the material contained
herein. The author/Ultrasonix Medical Corporation/publisher do not assume any liability for injury
and/or damage to persons or property arising from this publication. It is the responsibility of the
clinician to determine appropriate practice to ensure patient safety at all times.
ISBN 978-0-9877634-0-2
Design and layout by JB Graphics
Printed and bound in Toronto, Canada
ULTRASOUND IMAGING
for Vascular Access and Regional Anesthesia
SECTION 1
INTRODUCTION TO ULTRASOUND
1 Understanding Ultrasound Physics for Clinical Assessment
2 Learning to Scan
3 Principles of Needle Skills
4 Integrating Scanning and Needle skills
SECTION 2
ULTRASONIX GPS FOR NEEDLE NAVIGATION
5 Using GPS for Needle Navigation In-Plane and Out-of-Plane
SECTION 3
ULTRASOUND FOR VASCULAR ACCESS
6 Ultrasound Characteristics of Arterial and Venous Flow
7 Ultrasound-Guided Vascular Access Line Placement
SECTION 4
ULTRASOUND-GUIDED BLOCKS
8 Femoral Nerve Block
9 Brachial Plexus Blocks
10 Sciatic Nerve Blocks
SECTION 5
ULTRASOUND-ASSISTED BLOCKS
11 Epidural and Spinal Blocks
SECTION 6
CONTINUOUS NERVE BLOCK CATHETER TECHNIQUES
12 In-Dwelling Catheters for In-Patients and Out-Patients
SECTION 7
IMPLEMENTING ULTRASOUND IN THE HOSPITAL SETTING
13 Patient, Surgical, and Hospital Expectations
SECTION 1
INTRODUCTION TO ULTRASOUND
A
lthough ultrasound has recently emerged within clinical an-
esthesia practice, the routine use of this technology among
anesthesiologists continues to develop in both community and
academic settings. The introduction of ultrasound techniques
to anesthesia for vascular access and regional anesthesia is
currently a focus for anesthesia education, and is paralleled
by a drive for technological innovation and development among industry lead-
ers. Efforts to incorporate ultrasound into anesthetic practice are fundamentally
rooted in the goals of improving patient safety and interventional anesthesia
efficacy. Although most anesthesiologists are well aware of the challenges of
vascular access and regional anesthesia (for both success and potential com-
plications), the introduction of this technology presents novel challenges of ac-
quiring new knowledge and skill sets to achieve these goals.
Consequently, the familiar training adage of “see one, do one, teach one” is
no longer tenable. Ultrasound education must provide clinicians with a com-
prehensive and step-wise approach to understand the fundamentals of the
equipment and acquire new skills to suit their unique practice needs and set-
ting. Through an understanding of this technology at a clinical level, rather than
simply teaching with specific technical agendas or checklists, individuals may
continue to utilize ultrasound to its fullest capacity.
As with acquiring any new skill, there will be initial challenges for both the
novice and experienced anesthesiologist. From correlating anatomy with sono-
anatomy, and visualizing needles and fluid dynamics in real-time below the skin
surface, ultrasound provides opportunities and unique challenges for vascular
access and regional anesthesia. As our clinical practice evolves, so will the
expectations placed upon us by patients, surgeons, hospitals, and governing
agencies. Achieving the goals of improving patient safety, interventional effi-
ULTRASONIX INTRODUCTION TO ULTRASOUND 1
cacy, and overall patient satisfaction will require the learner to set their own
self-directed path towards defining their clinical interests, scope of practice,
and skills self- assessment.
The following chapters provide a foundation for clinicians to approach, develop,
and refine essential knowledge and skills to integrate ultrasound into routine
anesthesia practice. By pairing the basic clinical principles of the ultrasound
equipment with the most recent technological innovations in needle guidance,
the goal is to optimize time devoted to reading and bench learning to the clini-
cal setting and benefit patient care. This text is designed to provide the basis
from which ongoing, self-directed learning through books, journals, and hands-
on workshops may be facilitated.
Brian A. Pollard
2 ULTRASONIX INTRODUCTION TO ULTRASOUND
CHAPTER 1
Understanding Ultrasound Physics for Clinical
Assessment
The ability to acquire, manage, and interpret an ultrasound image is a prerequi-
site to any other skill set. Therefore competency with ultrasound imaging must
be achieved prior to interventional procedures. Appreciating the difference
between three-dimensional patient anatomy and the two-dimensional screen
image is fundamental for ultrasound-guided interventions. Even in the most
limited discussions of ultrasound physics as it relates to our clinical practice,
there are new concepts that present challenges upon first approach.
The Ultrasound Transducer – Source of Energy and Image
Each ultrasound transducer is required to a) create a source of energy that
when applied to the skin safely penetrates the tissues, and b) receive any en-
ergy reflected back to the transducer from the tissues. To generate the ultra-
sound energy, an electrical current is applied to the crystal component within
the transducer face. The current is then converted to mechanical (ultrasound)
energy and transmitted to the tissues at very high (megahertz) frequencies.
The ultrasound energy produced then travels through the tissues as pulsed,
longitudinal, mechanical waves originating from the point the transducer con-
tacts the skin.
The transducer (or ‘probe’) is potentially the most limiting component of any
ultrasound scan or subsequent interventional procedure, as it determines
the characteristics of the energy that is emitted, received, and subsequently
processed for anatomical representation on screen (Fig. 1.1). Understanding
how this component works is essential, because an inability to optimally select
specific transducer characteristics will result in limited image acquisition, and
therefore potentially impact safety and eventual block success.
Resolution
Our ability to ‘visualize’ the anatomy deep to the transducer in contact with the
skin surface is dependent on the potential resolution for each scanned area.
Resolution is determined by the extent to which the energy that leaves the
transducer penetrates the tissues and returns to the transducer to accurately
ULTRASONIX INTRODUCTION TO ULTRASOUND 3
Fig. 1.1 Schematic illustration of transducer with energy emitted and returned through tissues
represent the anatomical structures below. Unfortunately, once the vibrational
ultrasound energy leaves the crystalline face of the transducer, it is immediately

and progressively degraded as it contacts and enters the tissues. This concept
of emitted energy that is ‘lost’ (not returned to the transducer) is known as the
attenuation of ultrasound energy. It can occur through absorption, reflection,
scattering, or refraction of the ultrasound waves (Fig. 1.2). The degree of ultra-
sound energy attenuation is directly proportional to the frequency of the energy
emitted and the total distance the signal must travel in returning to the trans-
ducer from a structure of interest. This attenuation of the emitted ultrasound
energy may contribute to the distortion or misrepresentation of anatomical rela-
tionships characterized on the ultrasound screen image.
4 ULTRASONIX INTRODUCTION TO ULTRASOUND
Fig. 1.2 Schematic illustration of a) absorption, b) reflection, c) scattering, d) refraction
Even with beam attenuation, it is still possible to visualize anatomical structures

on screen when separated by less than one millimeter. The clinician’s task is
to choose the best transducer for each scan, optimize the equipment settings,
and remain aware of potential artifacts (and pitfalls) due to the attenuation
of ultrasound energy. The physical properties of ultrasound waves travelling
through tissues act not only to reveal anatomical relationships, but also to hide
and misrepresent anatomical structures on screen. When examining anatomi-
cal representations on the two dimensional ultrasound screen, our resolution is
determined by the ability to differentiate structures in the ‘X’ (horizontal) and ‘Y’
(vertical) axes. In the language of ultrasound imaging, these are described as
Lateral Resolution and Axial Resolution respectively (Fig. 1.3).
Lateral Resolution describes the potential to visualize two structures that are
in a plane perpendicular to the direction of the ultrasound beam. This is the
ability to visualize two structures at the same tissue depth relative to the face of
the ultrasound transducer in contact with the skin (appearing ‘side-by-side’ on
screen). Lateral resolution can be improved by increasing either the frequency
ULTRASONIX INTRODUCTION TO ULTRASOUND 5
Fig. 1.3 Schematic illustration of axial and lateral resolution for discrete objects
or diameter of the ultrasound transducer.
Axial Resolution describes the potential to visualize two structures that are situ-
ated in a plane parallel to the emitted ultrasound beam. These are structures
located at different tissue depths relative to the face of the ultrasound trans-
ducer (one object appears ‘above’ the other on screen). Axial resolution can be
improved by selecting transducers with higher frequencies.
Although both lateral and axial resolution are improved with higher frequency
transducers, all ultrasound energy is progressively degraded as it travels fur-
ther through tissues. This degree of attenuation (‘loss’) is proportional to the
frequency of the energy applied. Higher frequency energy is ‘lost’ to the tissues
to a greater extent than lower frequency energy with progressive tissue penetra-
tion. Irrespective of frequency, lateral and axial resolution always decrease with
increasing tissue depth (Fig. 1.4).
For the lateral and axial resolution of superficial structures, ultrasound imaging
should be performed with the highest frequency transducer available. When
6 ULTRASONIX INTRODUCTION TO ULTRASOUND