Vascular Access

Consultant Topic Champions: Luke Phillips

Vascular access is a core procedure for any emergency clinician. Patient factors such as obesity, IV drug use, oedema, previous chemotherapy and anatomy can make peripheral venous and arterial access difficult.  Ultrasound allows us to visualise these vessels and improve our chances of success.  In addition real-time guided central venous access increases successful central line placement as well as improving patient safety and decreasing complication rates.

Completion of accreditation in this topic will allow the clinician to become proficient in vascular access of both peripheral veins and arteries and central veins.

Learning Objectives

  • Become proficient in the use of ultrasound and integrating this with the physical techniques for accessing central and peripheral veins and in arterial access
  • Be able to access vessels using both longitudinal and transverse techniques and optimise ultrasound images.
  • Have knowledge of the anatomy at various sites that you will be accessing including associated structures and surface anatomy
  • Be able to distinguish veins from arteries including the use and limitation of colour doppler and B-mode compression ultrasound.

Probe Selection, Orientation & Machine Setup

The linear high frequency probe should be used for all vascular access. The machine should be set to a vascular pre-set and most new machines including the SPARQ have a needle visualisation pre-set.

Generally it is best to position the US machine so it is in your line of site and you do not need to turn or look away from the needle. Pre-scan your area of interest prior to prepping the patient and your sterile field and adjust your depth so the vessel is in the middle of your screen (or set to appropriate level of focus).

The probe can be orientated either transverse across the vessel or longitudinally in line with the vessel.  When starting out it is best to attempt the transverse approach and this approach has proved somewhat more successful in a number of studies.
Planes of Ultrasound in Vascular Access
Image obtained from http://www.aium.org/resources/guidelines/usgva.pdf
Please use a probe cover when attempting vascular access as the risk of probe contamination with blood products in vascular access is extremely high
Identifying Veins and Arteries
It is important when scanning for vascular access to be able to distinguish between arteries and veins.  The following tips will help you to identify your target vessel.
  • Know the normal anatomy of your central veins.  For example, just below the inguinal ligament, the artery is normally placed lateral to the vein. Anatomical variations are common.
  • Arteries are round with generally thicker walls while veins are ovoid. The artery is pulsatile whereas the vein is usually not. Larger central veins may have respiratory variation in size.

  • Compressibility – The muscular wall of the artery resists deformation when compressed, while a non-thrombosed vein is able to be compressed.
  • Color Flow Doppler:  The artery shows an intermittent pulsatile flow with color whereas the vein shows a gradually undulating continuous flow. The color of the flow as this can be changed by changing the direction of angulation of the probe.
  • Pulsed wave Doppler – Selecting the PWD and placing the cursor at the center of the vessel and obtaining a trace will show a steady gradually changing flow in the vein and sharply accelerating, pulsatile flow in the artery.

 

Peripheral Venous Cannulation

The upper limb is most common site to access peripheral veins.   Anatomy of the venous system is outlined below.

Ultrasound Guided Peripheral IV Cannulation. Microcast from Ultrasound Podcast

It is extremely important to select a long enough cannula to avoid dislodgement when the patient moves and tissue extravasation. Generally I would use a long cannula for any IV access that is deeper than just superficial to the skin.  Be extremely cautious using inotropes and contrast in US guided peripheral IV cannula as they have a much higher risk of dislodgement and misplacement. The table below outlines the cannula length required for the depth of the vein.

IV Catheter Length Guidelines – Reproduced from http://www.acepnow.com/article/10-tips-ultrasound-guided-peripheral-venous-access/2/

Central Venous Access

Central venous access is core skill for an emergency physician to have. A sterile technique should be performed in all but time critical scenarios and should be performed as per your hospital policy.

The anatomy of both the femoral and internal jugular veins and their surrounding structures is of vital importance to avoid complications.  Subclavian vein cannulation using ultrasound requires advanced skill and will not be discussed here.

Ultrasound Images of Femoral (FV) and Internal Jugular (IJ) Vein and their surround Structures (N – femoral nerve, FA – femoral artery, CA – carotid artery)

Arterial Access

Arterial access for monitoring haemodynamics and blood gases is usually performed by accessing the radial artery.  In situations where this is not feasible the femoral and then brachial artery would be the subsequent preferences.  The video below outlines how to access the radial artery using ultrasound. Generally US is used as a rescue technique for failed blind technique or impalpable pulses but I frequently use it to assess the size , depth and direction of the artery prior to accessing via a blind technique.

Ultrasound Guided Radial Artery Cannulation – Microcast from Ultrasound Podcast

Learning & Accreditation Process

Accreditation of eFAST within the department will involve:

  • Completion of online learning module through UTEC (Geelong ED Sign on code = GORUS) or have completed an accredited course.
  • Attend departmental workshop.
  • Completion of a logbook which includes 3 supervised peripheral access scans (Venous or Arterial) & 5 supervised central access scans.
  • 2 formative assessments and 1 summative assessment by an ED consultant (these can be included in your logbook scans and are not in addition). Form available for online completion (Smart phone/Tablet compatible). There should be at least one peripheral and one central access scan assessed.
  • CCPU Syllabus and formative and summative assessment forms
  • Ongoing credentialing requirements include completion of logbook requirements every 2 years.

Minimum Imaging Requirements for Logbook

  • Generally this will require an assistant.
  • A still optimised image of the vessel being accessed is required
  • A video loop of the vessel being accessed or
  • A second still image of the vessel containing either the wire or the cannula.

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