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Central venous cannulation: ultrasound techniques
CORE: INTENSIVE CARE
Central venous cannulation: ultrasound techniques
Learning objectives After reading this article, you should be able to: C list the indications for central venous cannulation and describe the commonly used insertion sites C explain the advantages of ultrasound-guided central venous catheter insertion C describe the limitations of the technique and potential pitfalls for the novice operator C understand the importance of needle-tip visualization and avoidance of arterial cannulation
Simon Flood Andrew Bodenham
Abstract Central venous cannulation is commonly undertaken by a range of specialties in diverse clinical settings. Central veins may be cannulated by the landmark, ultrasound-guided or open surgical cut-down techniques. Complications of central venous catheter (CVC) insertion are common and may lead to significant morbidity and very occasional mortality. Twodimensional ultrasound-guided central venous catheter placement has been shown by randomized controlled trials to be superior to the landmark technique. It reduces both the number of needle passes required for successful placement and the incidence of complications. Constant needle-tip visualization is a challenge for the novice operator. The UK National Institute for Clinical Excellence (NICE) has recommended since 2002 that following appropriate training, clinicians should use ultrasound wherever practical in both elective and emergency internal jugular vein catheterization. Most clinicians would now recommend its use for all routes of access.
entering the vein in real time. Indirect guidance describes using ultrasound to confirm the position of a patent vein prior to cannulation. Although less demanding for the novice, it does not provide all the advantages of direct techniques. Central veins may also be cannulated by a surgical cut down.
Complications of CVC insertion Complications from attempted CVC insertion are common. Depending on case mix and operator skill, up to 10% of attempted cannulations lead to a complication. Complication rates correlate to the number of needle passes and may lead to significant morbidity and occasional mortality.3 Common complications include arterial puncture, haematoma and pneumothorax.
Keywords Central venous catheter; femoral; jugular; subclavian veins; ultrasound; venous cannulation
Ultrasound technology Royal College of Anaesthetists CPD Matrix: 2A04
Two-dimensional (2D) ultrasound uses high-frequency sound, reflected from tissue interfaces, to generate an image of superficial structures. Fluid-filled structures such as blood vessels appear dark. Air, bone and needles are hyperechogenic and appear bright. Structures deep to air or bone will not be visualized (acoustic shadowing). Low-frequency sound penetrates deeper than high frequency, but produces lower-resolution images. Central veins are generally accessed within a few centimetres of the skin, so high-frequency (7.5e10 MHz), high-resolution probes are used. 2D ultrasound may be combined with Doppler imaging (Duplex) to show blood flow and direction. This can be useful in differentiating arteries from veins (Table 1).
Indications for central venous access Central venous catheters (CVCs) are commonly inserted to facilitate monitoring (i.e. central venous pressure, cardiac output) or delivery of drugs (e.g. vasopressors, chemotherapy agents) into the central circulation. CVCs also allow provision of total parenteral nutrition, renal replacement therapy or transvenous cardiac pacing. An estimated 250,000 are inserted annually in UK hospitals.1
Methods of cannulation
Distinguishing features of arteries and veins under ultrasound
The traditional ‘landmark technique’ relies on using surface anatomical features and palpable arterial pulses as a guide to deeper structures. Ultrasound guidance may be direct or indirect.2 Direct guidance uses ultrasound to visualize the needle
Simon Flood MRCP FRCA DICM is a Consultant in Anaesthesia and Intensive Care Medicine at the Leeds Teaching Hospitals NHS Trust, UK. Conflict of interest: none declared. Andrew Bodenham FRCAFFICM is a Consultant in Anaesthesia and Intensive Care Medicine at the Leeds Teaching Hospitals NHS Trust, UK. Conflict of interest: AB has received honoraria from ultrasound manufacturers for teaching courses.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
Arteries
Veins
Pulsatile Not easily compressed, visualization improves with compression Round Characteristic pulsatile Doppler signal
Non-pulsatile Easily compressed
Elliptical Characteristic more continuous Doppler signal Change shape on respiration/Valsalva
Table 1
1
Ó 2013 Elsevier Ltd. All rights reserved.
CORE: INTENSIVE CARE
subclavian vessels and is easily visualized by ultrasound (Figure 1); it is also at risk from a low internal jugular approach.
Limitations of the technique All new clinical skills have an associated learning curve and ultrasound-guided cannulation does not easily grant novices immediate success. Adequate training, practice and supervision are required to gain competence. An appreciation of how 2D images relate to three-dimensional (3D) anatomy is essential. Constant visualization of needle-tip position may initially be difficult to maintain and loss of the needle-tip view risks complications. Figure 1 Non-compressible thrombus completely blocking the right subclavian vein. More commonly there will be a crescent of thrombus partially blocking the vein. White arrow, chest wall/pleura; SCA, subclavian artery.
Insertion sites The internal jugular vein (Figure 2) is a superficial structure lying adjacent to the carotid artery. It is often the most convenient site of access in the anesthetized patient. There is wide variability in the relationship (including overlap) between artery and vein and some patients will have a dominant venous circulation on one side of the neck. The subclavian vein is preferred in the head-injured patient (minimal effect on intracranial pressure) or for prolonged access. The clavicle restricts visualization of the subclavian vein, but by moving a short distance laterally, the axillary artery and vein may be visualized (Figure 3). Further laterally, the operator will note a greater distance between vein and pleura, reducing the risk of pneumothorax. This advantage is balanced by a smaller diameter and deeper vessel compared with a more medial approach. It may be difficult to visualize and access the vein in obese or muscular patients. Supraclavicular approaches are also used. The femoral vein is favoured in those unable to tolerate headdown positioning. Traditional teaching suggests the superficial femoral artery does not cross the femoral vein until several centimetres below the inguinal ligament. Radiological studies have shown crossover is higher than commonly appreciated.4 Ultrasound allows verification of anatomy and accurate first pass puncture of the common femoral vein.
Advantages of ultrasound Ultrasound can identify aberrant anatomy or thrombosed/ stenosed vessels (Figure 1). In both scenarios, alternative access sites should be sought and useless needle passes avoided. Ultrasound can detect valves or collapsed veins. Valves are avoided by adjusting the needle insertion point. Empty veins are more easily cannulated following fluid resuscitation, head-down positioning, intermittent positive pressure ventilation or positive end-expiratory pressure, or the Valsalva manouvre. Ultrasound may identify guidewire or catheter misplacement, for example imaging the neck during subclavian vein cannulation may identify retrograde passage into the internal jugular vein. Arteries accompanying the major veins are easily visualized with ultrasound. In well-filled veins, real-time ultrasound allows the operator to cease forward movement of the needle once the anterior wall is penetrated and the needle tip lies within the lumen, avoiding posterior vein wall puncture and haematoma formation. Vessel transfixion may be unavoidable when cannulating an empty vein. The pleura lies immediately posterior to the
Figure 2 Cross-sectional view of right internal jugular vein (IJV) and carotid artery (CA) with needle introduced in the short axis. (a) Needle tip is seen just indenting the anterior vein wall. (b) Needle further indents the vein wall but the tip is still covered by vein wall which is ‘tented’ into the lumen, no blood can be aspirated. (c) Needle tip has passed through the vein wall to lie within lumen, vein has re-expanded and correct position is confirmed by free aspiration of blood. The green dot in the upper right-hand corner of each image is an orientation marker. The probe is correctly orientated when a palpable marker on the probe is on the same side as the green dot on display. This ensures that right and left in the image correspond correctly to medial and lateral on the patient.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
2
Ó 2013 Elsevier Ltd. All rights reserved.
CORE: INTENSIVE CARE
Figure 4 A J-tipped guidewire passing through a needle entering a mock vein, imaged longitudinally, in an agar phantom. T, tip. Figure 3 Cross-sectional view of axillary vein (AxV) and artery (AxA). Note: the small circular arterial branch anterior to the vein (arrow).
more echogenic. Many operators now suggest using crosssectional vessel visualization and needle in plane approaches or hybrid variations of techniques.
High-frequency ultrasound can identify peripheral veins in the limbs. This is useful in the obese or intravenous drug user and may facilitate central venous access with a peripherally inserted central catheter (PICC) in the mid-upper arm to avoid flexure at the elbow.
Verification of needle/wire/catheter placement Inadvertent arterial puncture by a needle or guidewire is usually remedied without serious sequelae by careful removal and application of sustained direct pressure. Dilatation over a wire or cannulation of an artery can be associated with severe morbidity (cerebrovascular accident, local haemotoma, haemothorax, arteriovenous fistula) and occasional mortality. The American Association of Anaesthetists (ASA) recommends a four-stage position verification procedure.6 Arterial puncture cannot be ruled out by colour of aspirated blood or the absence of pulsatile flow. Needle-tip position should therefore be confirmed by real-time ultrasound, blood gas analysis or pressure monitoring. Secondly, guidewire position should be confirmed by ultrasound, transoesophageal echocardiography or ECG analysis. Compliance with these two checks should prevent accidental dilatation of an artery. Thirdly, before use, venous placement of the catheter itself should be confirmed by ultrasound, pressure monitoring or fluoroscopy. Finally, the catheter tip position should be checked on a chest radiograph. This may be safely delayed, for example, until completion of surgery and is not a prerequisite for catheter use. In the event of inadvertent arterial dilatation/cannulation, the device should be left in situ and the urgent advice of an interventional radiologist or vascular surgeon sought. The dilator/ catheter may then be safely removed under fluoroscopic guidance or at open surgery with measures in place to manage subsequent haemorrhage, embolus or dissection.6 A
Evidence for ultrasound guidance Seven randomized controlled trials examining internal jugular vein cannulation concluded ultrasound improved first attempt success rate, reduced the number of needle passes and decreased the incidence of complications compared with the landmark technique.1,5 Ultrasound also reduced the time to successful cannulation. Trends are similar for other sites.
Equipment preparation The display should be positioned on the opposite side of the patient to the operator. The image should anatomically be in the orientation as seen from the position of the operator. An orientation marker in the image (as shown by a green dot used by the manufacturers of the devices used in Figures 2 and 3) should be matched to a palpable marker on the probe. Correct orientation ensures that the image moves in a logical direction when the probe is moved and that the needle moves in the same direction in the patient as on the display. If in doubt, touch the scan surface at one end of the probe and watch for the accompanying display artefact.
Needle-tip visualization The spatial relationship between needle and probe may be ‘short’ or ‘long’ axis and the image cross-sectional or longitudinal. It is common to use a cross-sectional view and short axis insertion (Figure 2). This method provides excellent visualization of surrounding structures. It takes practice to maintain constant needle-tip visualization as the tip may inadvertently pass through the beam and the shaft be mistaken for the tip. Alternatively, the vein may be imaged longitudinally and the needle inserted in the long axis. This gives superior needle/wire views but does not provide concurrent images of surrounding structures (Figure 4). Some needles have their distal 1 cm machined to make them
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
REFERENCES 1 National Institute for Clinical Excellence. Guidance on the use of ultrasound locating devices for placing central venous catheters. London: 2002. Also available at: http://www.nice.org.uk/Guidance/ TA49; (accessed 5 August 2012). 2 Lamperti M, Bodenham AR, Pittiruti M, et al. International evidencebased recommendations on ultrasound-guided vascular access. Intensive Care Med 2012; 38: 1105e17. 3 Mansfield PF, Hohn DC, Fornage BD. Complications and failures of subclavian-vein catheterisation. N Engl J Med 1994; 331: 1735e8.
3
Ó 2013 Elsevier Ltd. All rights reserved.
CORE: INTENSIVE CARE
4 Hughes P, Scott C, Bodenham A. Ultrasonography of the femoral veins, implications for vascular access. Anaesthesia 2000; 55: 1199e202. 5 Wigmore TJ, Smythe JF, Hacking MB, Raobaikady R, MacCallum NS. Effect of the implementation of NICE guidelines for ultrasound guidance on the complication rates associated with central venous catheter placement in patients presenting for routine surgery in a tertiary referral centre. Br J Anaesth 2007; 99: 662e5.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
6 American Society of Anesthesiologists Task Force on Central Venous Access. Practice guidelines for central venous access. Anesthesiol 2012; 116: 539e73. FURTHER READING Hamilton H, Bodenham A, eds. Central venous catheters. Oxford: Wiley Blackwell, 2009.
4
Ó 2013 Elsevier Ltd. All rights reserved.
Central venous cannulation: ultrasound techniques
Learning objectives After reading this article, you should be able to: C list the indications for central venous cannulation and describe the commonly used insertion sites C explain the advantages of ultrasound-guided central venous catheter insertion C describe the limitations of the technique and potential pitfalls for the novice operator C understand the importance of needle-tip visualization and avoidance of arterial cannulation
Simon Flood Andrew Bodenham
Abstract Central venous cannulation is commonly undertaken by a range of specialties in diverse clinical settings. Central veins may be cannulated by the landmark, ultrasound-guided or open surgical cut-down techniques. Complications of central venous catheter (CVC) insertion are common and may lead to significant morbidity and very occasional mortality. Twodimensional ultrasound-guided central venous catheter placement has been shown by randomized controlled trials to be superior to the landmark technique. It reduces both the number of needle passes required for successful placement and the incidence of complications. Constant needle-tip visualization is a challenge for the novice operator. The UK National Institute for Clinical Excellence (NICE) has recommended since 2002 that following appropriate training, clinicians should use ultrasound wherever practical in both elective and emergency internal jugular vein catheterization. Most clinicians would now recommend its use for all routes of access.
entering the vein in real time. Indirect guidance describes using ultrasound to confirm the position of a patent vein prior to cannulation. Although less demanding for the novice, it does not provide all the advantages of direct techniques. Central veins may also be cannulated by a surgical cut down.
Complications of CVC insertion Complications from attempted CVC insertion are common. Depending on case mix and operator skill, up to 10% of attempted cannulations lead to a complication. Complication rates correlate to the number of needle passes and may lead to significant morbidity and occasional mortality.3 Common complications include arterial puncture, haematoma and pneumothorax.
Keywords Central venous catheter; femoral; jugular; subclavian veins; ultrasound; venous cannulation
Ultrasound technology Royal College of Anaesthetists CPD Matrix: 2A04
Two-dimensional (2D) ultrasound uses high-frequency sound, reflected from tissue interfaces, to generate an image of superficial structures. Fluid-filled structures such as blood vessels appear dark. Air, bone and needles are hyperechogenic and appear bright. Structures deep to air or bone will not be visualized (acoustic shadowing). Low-frequency sound penetrates deeper than high frequency, but produces lower-resolution images. Central veins are generally accessed within a few centimetres of the skin, so high-frequency (7.5e10 MHz), high-resolution probes are used. 2D ultrasound may be combined with Doppler imaging (Duplex) to show blood flow and direction. This can be useful in differentiating arteries from veins (Table 1).
Indications for central venous access Central venous catheters (CVCs) are commonly inserted to facilitate monitoring (i.e. central venous pressure, cardiac output) or delivery of drugs (e.g. vasopressors, chemotherapy agents) into the central circulation. CVCs also allow provision of total parenteral nutrition, renal replacement therapy or transvenous cardiac pacing. An estimated 250,000 are inserted annually in UK hospitals.1
Methods of cannulation
Distinguishing features of arteries and veins under ultrasound
The traditional ‘landmark technique’ relies on using surface anatomical features and palpable arterial pulses as a guide to deeper structures. Ultrasound guidance may be direct or indirect.2 Direct guidance uses ultrasound to visualize the needle
Simon Flood MRCP FRCA DICM is a Consultant in Anaesthesia and Intensive Care Medicine at the Leeds Teaching Hospitals NHS Trust, UK. Conflict of interest: none declared. Andrew Bodenham FRCAFFICM is a Consultant in Anaesthesia and Intensive Care Medicine at the Leeds Teaching Hospitals NHS Trust, UK. Conflict of interest: AB has received honoraria from ultrasound manufacturers for teaching courses.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
Arteries
Veins
Pulsatile Not easily compressed, visualization improves with compression Round Characteristic pulsatile Doppler signal
Non-pulsatile Easily compressed
Elliptical Characteristic more continuous Doppler signal Change shape on respiration/Valsalva
Table 1
1
Ó 2013 Elsevier Ltd. All rights reserved.
CORE: INTENSIVE CARE
subclavian vessels and is easily visualized by ultrasound (Figure 1); it is also at risk from a low internal jugular approach.
Limitations of the technique All new clinical skills have an associated learning curve and ultrasound-guided cannulation does not easily grant novices immediate success. Adequate training, practice and supervision are required to gain competence. An appreciation of how 2D images relate to three-dimensional (3D) anatomy is essential. Constant visualization of needle-tip position may initially be difficult to maintain and loss of the needle-tip view risks complications. Figure 1 Non-compressible thrombus completely blocking the right subclavian vein. More commonly there will be a crescent of thrombus partially blocking the vein. White arrow, chest wall/pleura; SCA, subclavian artery.
Insertion sites The internal jugular vein (Figure 2) is a superficial structure lying adjacent to the carotid artery. It is often the most convenient site of access in the anesthetized patient. There is wide variability in the relationship (including overlap) between artery and vein and some patients will have a dominant venous circulation on one side of the neck. The subclavian vein is preferred in the head-injured patient (minimal effect on intracranial pressure) or for prolonged access. The clavicle restricts visualization of the subclavian vein, but by moving a short distance laterally, the axillary artery and vein may be visualized (Figure 3). Further laterally, the operator will note a greater distance between vein and pleura, reducing the risk of pneumothorax. This advantage is balanced by a smaller diameter and deeper vessel compared with a more medial approach. It may be difficult to visualize and access the vein in obese or muscular patients. Supraclavicular approaches are also used. The femoral vein is favoured in those unable to tolerate headdown positioning. Traditional teaching suggests the superficial femoral artery does not cross the femoral vein until several centimetres below the inguinal ligament. Radiological studies have shown crossover is higher than commonly appreciated.4 Ultrasound allows verification of anatomy and accurate first pass puncture of the common femoral vein.
Advantages of ultrasound Ultrasound can identify aberrant anatomy or thrombosed/ stenosed vessels (Figure 1). In both scenarios, alternative access sites should be sought and useless needle passes avoided. Ultrasound can detect valves or collapsed veins. Valves are avoided by adjusting the needle insertion point. Empty veins are more easily cannulated following fluid resuscitation, head-down positioning, intermittent positive pressure ventilation or positive end-expiratory pressure, or the Valsalva manouvre. Ultrasound may identify guidewire or catheter misplacement, for example imaging the neck during subclavian vein cannulation may identify retrograde passage into the internal jugular vein. Arteries accompanying the major veins are easily visualized with ultrasound. In well-filled veins, real-time ultrasound allows the operator to cease forward movement of the needle once the anterior wall is penetrated and the needle tip lies within the lumen, avoiding posterior vein wall puncture and haematoma formation. Vessel transfixion may be unavoidable when cannulating an empty vein. The pleura lies immediately posterior to the
Figure 2 Cross-sectional view of right internal jugular vein (IJV) and carotid artery (CA) with needle introduced in the short axis. (a) Needle tip is seen just indenting the anterior vein wall. (b) Needle further indents the vein wall but the tip is still covered by vein wall which is ‘tented’ into the lumen, no blood can be aspirated. (c) Needle tip has passed through the vein wall to lie within lumen, vein has re-expanded and correct position is confirmed by free aspiration of blood. The green dot in the upper right-hand corner of each image is an orientation marker. The probe is correctly orientated when a palpable marker on the probe is on the same side as the green dot on display. This ensures that right and left in the image correspond correctly to medial and lateral on the patient.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
2
Ó 2013 Elsevier Ltd. All rights reserved.
CORE: INTENSIVE CARE
Figure 4 A J-tipped guidewire passing through a needle entering a mock vein, imaged longitudinally, in an agar phantom. T, tip. Figure 3 Cross-sectional view of axillary vein (AxV) and artery (AxA). Note: the small circular arterial branch anterior to the vein (arrow).
more echogenic. Many operators now suggest using crosssectional vessel visualization and needle in plane approaches or hybrid variations of techniques.
High-frequency ultrasound can identify peripheral veins in the limbs. This is useful in the obese or intravenous drug user and may facilitate central venous access with a peripherally inserted central catheter (PICC) in the mid-upper arm to avoid flexure at the elbow.
Verification of needle/wire/catheter placement Inadvertent arterial puncture by a needle or guidewire is usually remedied without serious sequelae by careful removal and application of sustained direct pressure. Dilatation over a wire or cannulation of an artery can be associated with severe morbidity (cerebrovascular accident, local haemotoma, haemothorax, arteriovenous fistula) and occasional mortality. The American Association of Anaesthetists (ASA) recommends a four-stage position verification procedure.6 Arterial puncture cannot be ruled out by colour of aspirated blood or the absence of pulsatile flow. Needle-tip position should therefore be confirmed by real-time ultrasound, blood gas analysis or pressure monitoring. Secondly, guidewire position should be confirmed by ultrasound, transoesophageal echocardiography or ECG analysis. Compliance with these two checks should prevent accidental dilatation of an artery. Thirdly, before use, venous placement of the catheter itself should be confirmed by ultrasound, pressure monitoring or fluoroscopy. Finally, the catheter tip position should be checked on a chest radiograph. This may be safely delayed, for example, until completion of surgery and is not a prerequisite for catheter use. In the event of inadvertent arterial dilatation/cannulation, the device should be left in situ and the urgent advice of an interventional radiologist or vascular surgeon sought. The dilator/ catheter may then be safely removed under fluoroscopic guidance or at open surgery with measures in place to manage subsequent haemorrhage, embolus or dissection.6 A
Evidence for ultrasound guidance Seven randomized controlled trials examining internal jugular vein cannulation concluded ultrasound improved first attempt success rate, reduced the number of needle passes and decreased the incidence of complications compared with the landmark technique.1,5 Ultrasound also reduced the time to successful cannulation. Trends are similar for other sites.
Equipment preparation The display should be positioned on the opposite side of the patient to the operator. The image should anatomically be in the orientation as seen from the position of the operator. An orientation marker in the image (as shown by a green dot used by the manufacturers of the devices used in Figures 2 and 3) should be matched to a palpable marker on the probe. Correct orientation ensures that the image moves in a logical direction when the probe is moved and that the needle moves in the same direction in the patient as on the display. If in doubt, touch the scan surface at one end of the probe and watch for the accompanying display artefact.
Needle-tip visualization The spatial relationship between needle and probe may be ‘short’ or ‘long’ axis and the image cross-sectional or longitudinal. It is common to use a cross-sectional view and short axis insertion (Figure 2). This method provides excellent visualization of surrounding structures. It takes practice to maintain constant needle-tip visualization as the tip may inadvertently pass through the beam and the shaft be mistaken for the tip. Alternatively, the vein may be imaged longitudinally and the needle inserted in the long axis. This gives superior needle/wire views but does not provide concurrent images of surrounding structures (Figure 4). Some needles have their distal 1 cm machined to make them
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
REFERENCES 1 National Institute for Clinical Excellence. Guidance on the use of ultrasound locating devices for placing central venous catheters. London: 2002. Also available at: http://www.nice.org.uk/Guidance/ TA49; (accessed 5 August 2012). 2 Lamperti M, Bodenham AR, Pittiruti M, et al. International evidencebased recommendations on ultrasound-guided vascular access. Intensive Care Med 2012; 38: 1105e17. 3 Mansfield PF, Hohn DC, Fornage BD. Complications and failures of subclavian-vein catheterisation. N Engl J Med 1994; 331: 1735e8.
3
Ó 2013 Elsevier Ltd. All rights reserved.
CORE: INTENSIVE CARE
4 Hughes P, Scott C, Bodenham A. Ultrasonography of the femoral veins, implications for vascular access. Anaesthesia 2000; 55: 1199e202. 5 Wigmore TJ, Smythe JF, Hacking MB, Raobaikady R, MacCallum NS. Effect of the implementation of NICE guidelines for ultrasound guidance on the complication rates associated with central venous catheter placement in patients presenting for routine surgery in a tertiary referral centre. Br J Anaesth 2007; 99: 662e5.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 14:1
6 American Society of Anesthesiologists Task Force on Central Venous Access. Practice guidelines for central venous access. Anesthesiol 2012; 116: 539e73. FURTHER READING Hamilton H, Bodenham A, eds. Central venous catheters. Oxford: Wiley Blackwell, 2009.
4
Ó 2013 Elsevier Ltd. All rights reserved.