Paediatric arterial line insertion in the operating room

Key points

• Neonates are at higher risk of developing arterial line related complications.

• Aseptic technique, ultrasound guidance reduces complication rates.

• Contact NICU coordinator 021 874 779 to set up heparin infusion before transfer back to NICU.

• Pressure bag setting for saline flushes at <300mm Hg for patients under 10 kg.

Objective

Insertion practice and management of paediatric arterial lines in the operating room.

Indications

Patients who are critically unwell and/or having surgery with cardiovascular, respiratory, neurological and metabolic challenges require arterial line insertion for:

1. Perioperative continuous arterial blood pressure monitoring

2. Perioperative frequent blood sampling and monitoring.

Complications

Clinical indication and risk profile should be assessed carefully for each patient by senior clinicians.

The following complications can be transient but some may lead to permanent damage and can be devastating.

1. Bleeding from insertion site, disconnection or dislodgement

2. Haematoma

3. Vasospasm

4. Thrombosis and thromboembolism leading to limb ischaemia

5. Inadvertent retention of guide wire

6. Damage to peripheral nerves

7. Infection – local and systemic

8. Arteriovenous fistula

9. Arterial aneurysm

10. Arterial injection of drugs that may induce vessel damage

Risk assessment

Risk of complications is higher in

1. Premature neonates

2. Weight < 2 kg (Note: mean diameter of radial artery of a cohort of 50 infants under 6 months is 0.7mm).

3. Catheter to vessel ratio is high. There is no evidence for an ideal ratio but the risk is higher as size of catheter increases and vessel calibre decreases. (See table below for arterial catheter specifications).

4. Multiple attempts at cannulation. SMO to review the risk benefit assessment, alternatives, and consider assistance if it is technically difficult to cannulate after multiple attempts.

5. Absence of good collateral circulation. There are variabilities in radial and ulnar artery dimensions. Attempts in cannulation of ipsilateral radial and ulnar artery can lead to transient or irreversible ischaemia of distal limb. Ultrasound assessment of vessel patency and pulsation as well as guidance during cannulation is strongly recommended if there is a clinical need and benefit for ipsilateral attempts and cannulations.

6. Proximal artery catheterisation e.g. femoral artery

Risk mitigating strategies

1. For non-urgent placement, use aseptic non-touch technique; consider maximum barrier precaution (sterile glove, drapes, ultrasound probe cover and gown in some cases) for proximal arterial catheterisation, arterial lines that are expected to stay in for > 48 hours, real time ultrasound or when guide wire assisted techniques are used.

2. Insert the smallest gauge cannula clinically feasible.

3. Ultrasound to assess vessel anatomy and calibre prior to insertion is a useful exercise.

4. Real time ultrasound use by trained practitioners may reduce the number of attempts, damage to posterior vessel wall or adjacent structures.

5. Important note on guide wires – all wires must be counted on and off the working field by inserter and assistant (Anaesthetic technician or staff nurse) and clearly documented on the wire count board during procedure.

   1. Before connecting and flushing arterial catheter to transducer set, all guide wires should be removed and accounted for.

   2. Multiple wires are used in some cases to assist catheterisation and wire exchange of catheter.

   3. Inserter and assistant (anaesthetic technician or staff nurse) need to stop and confirm wire is intact and removed from arterial catheter before connecting and flushing.

   4. Please be vigilant when using Vygon leaderflex catheters making sure the external length of wire exceeds the length of catheter before advancing catheter over wire to skin. (22 G 4 cm catheter, total length 12cm, wire length 23 cm, 22 G 8 cm catheter, total length 16.5cm, wire length 26 cm.)

6. Continuous flushing is important, either by a syringe pump or a pressurised infusion bag flush system with a flow regulating device.

7. Do not force flush a blocked arterial catheter. It should be rewired or replaced.

8. Regular monitoring of skin perfusion distal to arterial line clinically. Consider displaying the digital photoplethysmogram signals of pulse oximetry as a surrogate with a second oximeter if clinical observation is not practical during surgery e.g. under surgical drapes.

9. Continuous display of waveform on monitor after insertion and during patient transportation.

10. Careful review with SMO consultation and arterial catheter removal if distal ischaemia is evident.

Choice of arterial access

In general peripheral sites are preferred as they have better collaterals, which reduces the risk of limb ischaemia.

However, it is not always feasible or practical during surgery e.g. the arterial catheter is in the surgical field, lack of site access during surgery, site choice limited by concomitant pathology.

Pre-ductal (right upper limb) arterial lines are clinically more useful than post-ductal in some patients e.g. coarctation of aorta, duct dependent cardiac lesions, congenital diaphragmatic hernia.

Peripheral site options:

1. Radial artery

2. Ulnar artery (Note: ulnar nerve is in close proximity to ulnar artery)

3. Posterior tibial artery

4. Dorsalis pedis is notably smaller in size compared to the above.

Proximal site options:

1. Femoral

2. Axillary (Note: brachial plexus is in close proximity to axillary artery)

3. Brachial

When cannulating proximal vessels, consider the following:

A. Size of vessel

These are end arteries without collaterals so risks of complications are higher than peripheral sites especially in premature neonates who weigh < 2 kg. Alternative monitoring e.g. NIBP, NIRS, mixed venous blood gas. Consider a multi-disciplinary discussion involving anaesthesia, ICU, surgical and medical SMOs, explicit consent and clear documentation of indication prior to insertion.

B. Retrograde cerebral embolization

Bolus flushing of arterial line at high pressure can lead to retrograde cerebral arterial flow and embolization.

To reduce the risk, flush manually with < 0.5 mL over a period of 5 seconds.

For the pressurised bag flush system, the pressure should be reduced to 150 mm Hg in neonates and infants. A shorter burst of flush by opening flow-regulating device for a short duration (≤ 1 second) is recommended.

The risk may be higher in vessels that are closer to cerebral circulation e.g. axillary vs femoral.

Insertion

• Position the patient to optimise success rate.

  • Wrist extension up to 45 degrees for radial artery

  • Dorsiflexion and foot eversion for posterior tibial artery

  • Plantar flexion for dorsalis pedis

  • Neutral hip position for femoral artery

• Perform hand hygiene and consider eye protection

  • Aseptic non-touch technique

  • Consider maximum barrier precaution (sterile glove, drapes, ultrasound probe cover and gown in some cases) for proximal arterial lines, arterial lines that are expected to stay in for > 48 hours, real time ultrasound or when guide wire assisted techniques are used.

• Ensure transducer set is flushed free of air before connected to arterial catheter.

• Before connecting and flushing arterial catheter to transducer set, all guide wires should be removed and accounted for.

• Ensure the connection between the cannula and transducer set is secured with no leak. Ensure there is no torque on the attached tubing.

• Secure the arterial line with sterile tape (or suture if indicated) and avoid kinking and twisting catheter. This is the most common cause of mechanical failure of arterial catheter.

• Cover the arterial line with transparent occlusive dressing so insertion site is visible.

• Confirm correct placement of arterial line with the presence of arterial waveform display on the monitor.

• Apply ‘arterial’ label over the occlusive dressing.

Patient transportation

• Turn off the roller clamp on the flush system prior to taking the pressure bag off the IV pole to avoid any air travelling down the system while transporting patients.

• Ensure that the transducer is secured appropriately prior to transportation - Leave it mounted on the transducer plate or tape to the patients arm.

• After transportation and before opening the system ensure that there is no air present within the line.

• Once this is done the system must be levelled, zeroed and flushed.

• NICU patients

  • If patient is going to NICU postoperatively and an arterial line is inserted in operating room, please handover to NICU SMO and discuss arterial line management. They will handover to the nursing team to set up a heparinised saline infusion syringe pump and ensure continuous infusion during transportation to NICU with 0.5units/mL heparinised saline at 0.5mL/hr for < 1 kg and 1 mL/hr for > 1kg.

  • Management and monitoring of umbilical artery catheter in operating room – continuous heparinised saline infusion from NICU decreases the likelihood of umbilical arterial catheters occlusion and should be maintained intraoperatively.

Management of limb ischaemia related to arterial line insertion

• Vasospasm is usually transient and reversible but thromboembolism can lead to complete occlusion of arterial supply to distal limb.

• Diagnosis in neonates is based on clinical signs which are poor capillary refill, pallor, cyanosis, weak or absent pulses.

• Prolonged ischaemia can lead to necrosis and loss of tissue so urgent investigation and intervention are required if suspected.

• Prompt removal of arterial catheter if ischaemia is evident.

• Warming of limb to encourage vasodilatation may be useful.

• Perform two-dimensional and Doppler ultrasound scan of artery early to facilitate early diagnosis and intervention of arterial occlusion.

• Early referral to paediatric cardiothoracic surgeon and/or vascular surgeon may be indicated for anticoagulation, sympathectomy or thrombectomy.

• There is limited evidence for pharmacological treatment. Injection of a small dose of lignocaine, nitroglycerin, papeverine vasospasm were reported in case reports.

Equipment and set up

Insertion equipment

Neonates and infants under 10 kg

• 24 G/22 G non-ported cannula (e.g. Insyte, Surflo, Vygon or 24G Arrow SAC)

• 0.015’/0.38mm wire for 24G, 0.018’/0.46mm wire for 22 G

• Alcohol and chlorhexidine skin preparation pads

• Clear dressing - Small Tegaderm

• Arterial labels

• Thin elastoplast 2 x strips or Tegaderm strips

• Soft tape to protect development of pressure area under cannula and connection

Children over 10 kg

• 22 G non-ported cannula (e.g. Insyte, Surflo, Vygon or 24G Arrow SAC)

• 0.018’/0.46mm wire for 22 G

• Alcohol and chlorhexidine skin preparation pads

• Clear dressing- Small Tegaderm

• Arterial labels

• Thin elastoplast 2 x strips or Tegaderm strips

Teenager and adults over 50 kg

• 20G non-ported cannula (e.g. Insyte, Surflo, Vygon or 24G Arrow SAC)

• 20G (0.025’/0.64mm wire available)

• Alcohol and chlorhexidine skin preparation pads

• Sterile gauze

• Clear dressing - Small Tegaderm

• Arterial labels

• Thin elastoplast 2 x strips or Tegaderm strips

Transducer set up

• Appropriate transducer set

• Extensions and extra red three way tap (double transducer sets only)

• 500 mL 0.9% sodium chloride bag

• 500 mL pressure bag

• Monitoring cable

• Transducer plate

Preparation of transducer set:

• Hand hygiene before opening the appropriate arterial transducer set, tighten connections - If using extensions attach these now.

• To eliminate air bubbles in the system: prime the transducer system, extension tubing and stopcock with normal saline by pulling the blue rubber toggle in the middle of the transducer upwards and observe that the system is flushing with normal saline. Ensure that all three way taps have been flushed.

• Non-injectable cap should be used in arterial line set.

• Hang normal saline bag in the pressure bag, place the transducer into the transducer plate and inflate the bag to the correct pressure.

• NOTE: pressure gauge setting

  • Neonate and infants ≤ 10 kg 150 mmHg (generates a flow rate of 1.5 mL/hr)

  • Paediatric > 10 kg 300 mmHg (generates a flow rate of 3 mL/hr)

• Look over the line set up and ensure the system has no air bubbles - flush again if necessary

• Attach the monitoring cable to the arterial set up.

• After zeroing and levelling the set up is ready to use.

Arterial line management

Zeroing Transducers

• Turn the three-way tap at the transducer off to the arterial tubing connected to patient.

• Take the cap off the sampling port so that it is open to air. Keep the cap sterile, otherwise replace with new sterile cap after zeroing.

• Zero on the monitor using the zeroing function on the M540 monitor. A flat line should appear on the screen at zero level.

• Wait until figures reach ‘0’ on the monitor.

• Recap the sampling port and turn the three-way tap to close off sampling port. This will reveal the arterial waveform on the monitor and display a numerical blood pressure.

• Zeroing the transducer enables the system to conform to atmospheric pressure, if not done the readings can be inaccurate.

• If you are unsure that the reading is accurate or not use the non invasive blood pressure to check how accurate the arterial reading is.

Levelling transducers

• Make sure that the patient and the transducer are appropriately positioned.

• The transducer can be levelled by determining the mid thoracic point of the chest and manipulate the transducer plate until it is level with this point.

• The mid thoracic point of the chest can be determined by counting down to the fourth intercostal space on the upper chest and following it around to the mid axillary line. This ensures that the reading will be taken from the level of the right atrium, which reflects filling pressure.

• When the patient of the bed changes position the transducer should be re-levelled.

Sampling arterial line

Assemble the following equipment:

• Arterial blood gas syringe

• Syringe of appropriate size for dead space fluid and sampling specimen

• Blood tubes needed for extra sampling

• Gauze and alcohol swab

• Sterile cap for three way tap

• Non sterile gloves

• Biohazard bag

• IV tray

STEPS:

• Place all equipment in an IV tray.

• Perform hand hygiene

• Select the three-way tap that is closest to the patient and place gauze under the sampling port.

• Remove sampling cap at the three-way tap and place into tray to discard.

• Swab the port with alcohol and chlorohexidine preparation pad. Attach a syringe to the sampling port.

• Turn three-way tap off to flush bag and withdraw 2 mL dead space fluid in the tubing. This amount will need to increase if sampling from a port that is further away from the patient (volume withdrawn should be at least 3 times the dead space). Blood sampling should be performed slowly to avoid collapsing the vessel and damaging its endothelium.

• Turn three-way tap back to a position half way between flush system and sample port before removing sampling syringes.

• After collecting blood specimen, turn the three-way tap off to the sample port.

• To flush the arterial line after use, turn the three-way tap off to patient and open to air, flush saline out the sampling port until it is clear of blood. Turn the three-way tap off to the sampling port, cap it off with a clean sterile cap.

• Flush the tubing connected to patient in short bursts (<1 second) until the tubing is clear of blood.

Removal of arterial line

• Equipment – Sterile gauze, round IV pressure pad dressing and/or stitch cutter.

• Perform hand hygiene and don gloves.

• Turn three-way tap off to the patient.

• Remove dressing, suture and tape as required.

• Place sterile gauze over the insertion site and apply firm pressure over the puncture site for at least 5 minutes and until there is no evidence of bleeding or haematoma development.

• Apply round IV pressure pad dressing and keep dressing intact for 24 hours

• Document the time and reason for removal in anaesthesia record, PACU record or clinical notes.

• Observe site and distal limb ½ hourly for 2 hours and then as required for signs of ongoing bleeding and distal limb perfusion.

Arterial catheter specifications

Other relevant clinical guidelines

1. Arterial line insertion and management in PICU

2. Peripheral arterial lines in the neonates

3. Arterial lines in the Operating rooms – Adults

4. Umbilical artery and vein catheterisation in the neonate