Ultrasound for central venous
access
A Hatfield
A Bodenham
Central venous catheterization
Central venous catheterization (CVC) is a common invasive procedure. In the UK in 1994, an
estimated 200 000 central venous access procedures were undertaken. Historically, central
venous access was gained by surgical cut-down
onto an appropriate vessel. The Seldinger technique is now the predominant method for directly inserting catheters into great veins.
Several factors should be considered before
any attempt at CVC: (i) indication for catheterization; (ii) duration of catheterization;
(iii) available sites; (iv) risks of complications;
and (v) experience of the operator. Indications
for CVC will not be discussed further. Common sites for catheterization are the internal
jugular vein, subclavian vein, femoral vein
and external jugular vein.
Many different approaches to CVC guided
by surface landmarks (SLM) have been described, suggesting no single route is always
reliable and safe. Latto and colleagues have
described these approaches and their advantages and disadvantages in detail.1
a fascial sheath with the axillary artery and
brachial plexus. It passes behind the clavicle
and becomes the subclavian vein at the outer
border of the first rib. It crosses the rib in the
subclavian vein groove and lies upon the pleura
where it joins the internal jugular vein to form
the brachiocephalic vein. The subclavian vein
lies anterior to the phrenic nerve and scalenus
anterior muscle. The subclavian artery lies
immediately behind scalenus anterior. Occasionally, both the subclavian vein and the subclavian artery lie posterior to scalenus anterior.
Femoral vein
The femoral vein lies within the femoral triangle and is medial to the femoral artery.
Both vessels lie within the femoral sheath,
the femoral nerve being lateral to this. This
relationship is most constant at the level of
the inguinal ligament. At a variable point distal
to the ligament overlap of the vein by the superficial femoral artery occurs. Ultrasound studies
show this often occurs at a more proximal level
than traditional texts suggest.
Key points
Complications of central
venous catheterization (CVC)
can be serious and often go
unreported.
It is often possible to predict
patients in whom CVC will be
difficult.
Use of real-time ultrasound
to guide needle insertion has
been demonstrated to
improve success rates and
reduce complications.
NICE currently recommend
the use of ultrasound for
placing catheters in the
internal jugular vein in adults.
Portable machines are
relatively cheap to purchase
and training is available in
their use.
Blind passage of the needle
Complications
Anatomy
The anatomy of the commonly used veins provides an explanation for many complications
that occur.
Internal jugular vein
The internal jugular vein follows a course from
the jugular foramen in the base of the skull to a
point between the clavicular and sternal heads
of the sternocleidomastoid muscle. It lies deep
to this muscle and is usually lateral to the
carotid artery. Both vessels lie within the
carotid sheath with the vagus nerve. Nearby
structures include the phrenic nerve, thoracic
duct, vertebral artery and thyroid lobe. The
apex of the lung is close to the inferior portion
of the internal jugular vein.
Subclavian vein
The axillary vein (formed from the brachial and
basilic veins) passes medially from the axilla in
Complications are often related to blind passage of the needle. They include: bleeding,
arterial puncture, pneumothorax, nerve damage, pain and dyspnoea. Less common complications include: thoracic duct damage,
tracheal damage, endotracheal tube damage,
respiratory obstruction (by haematoma), and
cerebrovascular accident caused by puncture
of the vertebral or carotid artery. Manual pressure on the artery after puncture may contribute to brain injury.
Complication rates
The SLM-guided technique has been shown to
have a complication rate of up to 10% with a
catheterization failure rate of up to 12% in
adults.
No formal system exists in the UK to record
the number of attempts at central venous cannulation and success rate. Uncertainty exists as
to what constitutes a complication (e.g. in one
series, failure was only considered to have
doi 10.1093/bjaceaccp/mki055
Continuing Education in Anaesthesia, Critical Care & Pain | Volume 5 Number 6 2005
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A Hatfield
Consultant Anaesthetist
Department of Anaesthesia
Bradford Teaching Hospitals NHS Trust
Duckworth Lane
Bradford
BD9 6RJ
Tel: 01274 364065
Fax: 01274 366548
E-mail: [email protected]
(for correspondence)
A Bodenham
Consultant Anaesthetist
Department of Anaesthesia
The General Infirmary at Leeds
Great George Street
Leeds
LS1 3EX
187
Ultrasound for central venous access
occurred with the SLM technique after one patient had undergone
15 unsuccessful passes). It seems likely that failures and complications are underestimated and underreported.
Ultrasound for central venous access
Guidelines for CVC have been described.2 These include: appropriate choice of site, correct patient positioning and use of a seeker
needle to locate the vein. Limiting the number of stabs and having
a strategy for failure are also important. However, despite
adequate training and use of guidelines, avoidable failures and
complications still occur.
Ultrasound
Medical ultrasound uses sound frequencies in the range 3–15 MHz
(the upper limit of human hearing is 20 kHz). The piezoelectric
effect is used to generate soundwaves and the probe acts as both
transmitter and receiver. Tissue penetrance is inversely related to
probe frequency. Thus, high frequency probes (7.5–10 MHz) are
most useful for CVC.
There are various modes of ultrasound. B-mode (brightness
mode) provides real-time two-dimensional images; most clinicians
are familiar with this. Many machines can combine B-mode with
Doppler imaging (duplex scanning). Quantitative assessment of
blood flow is possible because moving red blood cells reflect sound
waves producing a Doppler shift. Audible Doppler-only machines
provide no image and are of limited value in CVC.
Soundwaves are attenuated as they pass through body. Fluidfilled structures appear black as fluid transmits sound well and
there is no reflection. Sound is reflected off bone and air as they do
not transmit sound well. This generates a bright echo (seen as
white) on the image; it also results in an acoustic shadow
(black) in which no structures can be seen. In normal patients,
imaging intrathoracic structures is limited by air-filled lungs.
Advantages of ultrasound techniques
Ultrasound clearly demonstrates vein diameter, patency, direction
and relation to surrounding structures. The benefit of steep head
down and the Valsalva manoeuvre on the diameter of the internal
jugular vein is clearly seen (Fig. 1).
The internal jugular vein may overlie the carotid artery to
varying degrees. Ultrasound examination shows this overlap
may increase with rotation of the head.
The benefit of real-time ultrasound in CVC appears to be intuitive. It is also supported by many studies. A meta-analysis by
Randolph and colleagues examined eight prospective studies of
portable ultrasound guided CVC in normal patients.3 Success
rates in this group are high when experienced operators use
SLM-guided techniques. All procedures in the review were
performed by non-radiologists. The use of ultrasound in normal
patients increased catheterization success rates, reduced number
of passes required for success and decreased the incidence of
complications when compared with traditional SLM-guided
188
Fig. 1 Cross-sectional view of the neck, as seen from below,
demonstrating the effect of the Valsalva manoeuvre on the diameter of the
right internal jugular vein (IJV). The carotid artery (CA) does not distend in
response to the manoeuvre.
Table 1 Criteria for prediction of difficult or complicated central venous access
Surface landmarks difficult to identify or use (e.g. obesity; local swelling)
Limited sites for access attempts (e.g. other catheters; pacemaker; local surgery or
infection)
Previous difficulties during catheterization (e.g. >3 punctures at one site; 2 sites
attempted; failure to gain access)
Previous complication (e.g. arterial puncture; pneumothorax; nerve injury)
Known vascular abnormality (e.g. blocked great vein with collaterals)
Coagulopathy-uncorrected (INR >2; APTT >1.5; platelets <50 109 litre 1)
Patient unable to tolerate supine position (e.g. short of breath; increased intracranial
pressure)
Poorly compliant/agitated awake patient
Multiple previous long term catheterization (e.g. home TPN; dialysis catheters)
techniques. This was despite the inclusion of an equivocal
Doppler-only study. A more recent meta-analysis has confirmed
the benefit of B-mode ultrasound for safe CVC and also demonstrated opportunity cost savings.4 This paper was consistent with
others in emphasizing the limitation of Doppler-only techniques.
Difficulties can be anticipated in some groups of patients
(Table 1) and ultrasound is particularly useful during CVC in
these circumstances.5 In addition, many patients have been ‘salvaged’ using real-time ultrasound after failed SLM-guided
attempts.
Using ultrasound
The ultrasound technique can be taught on healthy individuals
(including oneself ) and patients. Agar phantoms have been manufactured for the same purpose and help with needle visualization.
A water bath allows the principles of needle visualization to be
appreciated. Therefore, a novice operator is able to develop
confidence in their ability to position probes and needles, and
Continuing Education in Anaesthesia, Critical Care & Pain | Volume 5 Number 6 2005
Ultrasound for central venous access
identify structures with minimum risk. When competency with the
equipment is achieved, supervised attempts at CVC can be undertaken.
By providing a two-dimensional image, B-mode ultrasound
can be used to examine structures in the transverse and longitudinal planes in a dynamic manner. The operator can rapidly build
up a three-dimensional appreciation of the underlying anatomy.
Arteries are seen to pulsate and are difficult to compress with the
ultrasound probe. Veins are non-pulsatile and collapse or distend
depending on probe pressure, patient position and respiration
(Fig. 1). This enables the operator to identify and differentiate
between the two structures. Vein patency, course and relationship
to surrounding structures are easily established. Ultrasound examination also enables the operator to determine the optimum
patient position for subsequent attempts at CVC.
Performing real-time ultrasound guidance
It takes only a few moments to screen and identify the most appropriate vein for CVC. The initial examination does not need to be
performed aseptically. During guided catheterization, asepsis is
maintained by using sterile gel and a sterile sheath to cover the
probe and a portion of its cable. Sheaths are commercially
available and cheap. A previously unopened tube of gel (waterbased) can be used if sterile sachets are not available.
Standard CVC kits are used and patients are prepared in the
usual manner. An assistant places gel on the probe and carefully
lowers it into the sterile sheath held by the operator. The operator
then removes air bubbles under the sheath by gently sweeping
them out of the gel with a finger. It is important that some gel
remains on the probe to provide acoustic contact with the sheath.
(A)
Sterile gel is then placed onto the covered probe providing the final
contact with the patient.
The chosen vessel can be visualized and catheterized in transverse or longitudinal view. The longitudinal view provides a
clearer image of the needle passage and entry into the vein.
Some probes may have an attachment to guide the needle for
both approaches. The authors prefer to use a free-hand technique.
Whilst maintaining the image of the vessel on screen, the needle is
introduced into the patient. The needle is usually visible but often
its initial presence is seen as distortion of local tissues. Control of
the tip is maintained at all times by keeping both the vessel
and needle in view, thus avoiding inadvertent passage into
surrounding structures. The anterior vessel wall is seen to indent
under pressure from the needle tip until a ‘give’ occurs and the vein
wall re-expands. The needle tip should then be visible within the
lumen (Fig. 2(A)).
Apposition of the anterior and posterior walls of the vein
occurs frequently. This explains why blood is often aspirated
during withdrawal of a needle rather than on insertion. Careful
withdrawal of the needle should result in entry into the lumen.
If this fails, a further pass at a shallower angle is usually successful
(additional head-down can also be helpful).
The probe is temporarily set aside on a sterile drape and the
guidewire passed in the usual way. It can then be used to confirm
that the guidewire is within the lumen (Fig. 2(B)). With appropriate skin preparation, it is also possible to ensure that the guidewire
has not passed in an unwanted direction (e.g. right or left internal
jugular vein, left subclavian vein). Correct position of the catheter
tip is important and should be checked in the usual way with a
chest x-ray or electrocardiographic guidance.
(B)
Fig. 2 (A) The needle tip seen indenting the anterior wall of the left internal jugular vein (LIJV). (B) A guidewire (GW) has been passed through the needle
and is seen emerging into the lumen of the vessel.
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189
Ultrasound for central venous access
(A)
(B)
Fig. 3 (A) Left internal jugular vein (LIJV) with thrombus obliterating nearly the entire lumen of the vessel. (B) Pressure applied with the probe demonstrates
lack of compressibility of the vein caused by thrombus.
Failure of the SLM technique
Despite impeccable SLM technique, failure to catheterize a vessel
may occur and repeated attempts often result in a complication.
Ultrasound frequently provides an explanation for the difficulty.
It may demonstrate absence of the expected vein or, if previously
catheterized, a vein may be stenosed and not distend with headdown tilt or the Valsalva manoeuvre. Occasionally, thrombus may
be present within the vein preventing needle entry or free aspiration of blood (Fig. 3).
Ultrasound can be used to identify an appropriate vessel before
a SLM-guided attempt at CVC. Knowledge that a vessel is present,
patent and in the ‘expected’ anatomical position can increase the
confidence of the operator; however, failures still occur.
To gain maximum benefit from the use of ultrasound real-time
guidance using B-mode (two-dimensional image) is most appropriate. In addition it provides trainees with an opportunity to
see and learn about applied anatomy.
The absence of a dynamic two-dimensional image with
Doppler-only devices greatly limits their usefulness for CVC,
especially in the difficult patient.
Future developments
The National Institute for Clinical Excellence (NICE) has
provided clinical guidelines for the use of real-time B-mode ultrasound for CVC. These are limited to supporting the use of
ultrasound for elective internal jugular vein catheter insertion.
NICE have not provided explicit advice on the use of ultrasound
in more challenging situations. With time, training and experience,
190
it is likely that real-time ultrasound guidance will become the
preferred method for CVC in most situations. Recently, ultrasound has been demonstrated to be beneficial in catheterizing
both the axillary6 and mid-arm basilic and cephalic veins.7
The challenge is how to fund widespread distribution of
machines and train large numbers of personnel in their use. Ultrasound is increasingly used for other procedures including pleural
drainage and nerve blockade.8
References
1. Latto IP, Ng WS, Jones PL, Jenkins BJ. Percutaneous Central Venous and Arterial
Catheterisation, 3rd Edn. London: WB Saunders, 2000
2. Waldman CS. Use of central venous catheters (CVC)—an algorithm. Care of
the Critically Ill 2001; 17: 148–9
3. Randolph AG, Cook DJ, Gonzales CA, Pribble CG. Ultrasound guidance
for placement of central venous catheters: a meta-analysis of the literature.
Crit Care Med 1996; 24: 2053–8
4. Hind D, Calvert N, McWilliams, et al. Ultrasonic locating devices for central
venous cannulation: meta-analysis. Br Med J 2003; 327: 361–4
5. Hatfield A, Bodenham A. Portable ultrasound for difficult central venous
access. Br J Anaesth 1999; 82: 822–6
6. Sharma A, Bodenham AR, Mallick A. Ultrasound guided axillary vein
cannulation for central venous access. Br J Anaesth 2004; 93: 188–92
7. Sandhu NS, Sidhu DS. Mid arm approach to basilic and cephalic vein using
ultrasound guidance. Br J Anaesth 2004; 93: 292–4
8. Hatfield A, Bodenham AR. Ultrasound: an emerging role in anaesthesia and
intensive care. Br J Anaesth 1999; 83: 789–800
See multiple choice questions 137–139
Continuing Education in Anaesthesia, Critical Care & Pain | Volume 5 Number 6 2005