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Neonatal lines and tubes

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Lines and tubes are on every neonatal trainee’s wish list. This article is a guide to the size, location, and distance of insertion of neonatal lines and tubes.

ENDOTRACHEAL TUBES (ETT)

How big should they be?

Laryngoscope blade: Miller size 1 for full-term infant, Miller size 0 or 00 for preterm infants

Where do I go?

Between the vocal cords and into the trachea.

Where do I stop?

The ETT tip should be 1cm above the carina on X-ray (i.e. at T1-T2)

LESS INVASIVE SURFACTANT ADMINISTRATION (LISA) CATHETERS

How big should they be?

It comes in one size only (the lumen diameter is usually 1.7mm in diameter).

Where do I go?

The LISA catheter should be passed through the vocal cords on direct vision with a laryngoscope or video laryngoscope.

Where do I stop?

Some catheters have a black mark on the outside of the catheter – insert to the top end of this mark.

If there is no black mark, insert up to the desired length as below:

SURFACTANT CATHETERS

How big should they be?

Surfactant administration kits contain a 4Fr 20cm catheter. If the kit is not available, a size 4-6 Fr nasogastric tube (NGT) can be used.

Where do I go?

Measure the length of the ETT / LISA catheter and mark it on your surfactant catheter / NGT. Slowly thread the surfactant catheter / NGT through the ETT / LISA catheter.

Where do I stop?

Stop passing the catheter when the mark is 1cm above the tip of the ETT / LISA catheter to ensure it enters the main stem bronchus.

LUMBAR PUNCTURE NEEDLES

How big should they be?

22G (term) or 25G (preterm) atraumatic lumbar puncture needle.

Where do I go?

The neonate can be positioned either lying on their side or sitting up. A 2022 2 x 2 randomised controlled trial, NeoCLEAR (Neonatal Champagne Lumber puncture Every time) published in The Lancet Child and Adolescent Health aimed to identify the optimum position for LP. 1082 infants between 27+0 and 44+0 gestational age weighing 1000g or more were randomised. First-attempt success rates were highest in the sitting position (63.7% v 57.6%), with the fewest desaturations in the sitting position.

Regardless of the position of the neonate, use the index finger of your non-dominant hand to palpate the anterior superior iliac spine (ASIS) and use your thumb to find the vertebral space directly in line with the ASIS (L3 to 4 or L4 to 5). Use your dominant hand to take the spinal needle with the bevel pointing towards the ceiling. Then, advance the needle slowly into the midline of your intervertebral space, angled towards the umbilicus.

Where do I stop?

You may feel a ‘pop’ as the lumbar puncture needle passes through the meninges (tip: if you feel firm resistance and the needle doesn’t advance, bone may be obstructing the needle, requiring withdrawal and repositioning of the needle). If you feel the needle is in the meningeal space then remove the stylet and watch for CSF flow. If there’s no CSF flow, then gently rotate the needle clockwise and reassess for flow. If there’s just frank blood, replace the stylet and remove the needle.

UMBILICAL CATHETERS

How big should they be?

Umbilical venous catheter (UVC): double lumen 4Fr catheter

Umbilical arterial catheter (UAC): single lumen 3.5Fr (<1.5kg) or 5Fr (>1.5kg)

Where do I go?

A cross sectional view of the umbilical cord

Where do I stop?

Calculated position:

Final position:

UAC: a ‘looping’ catheter is seen on x-ray as it goes down the internal iliac arteries and up through the abdominal aorta. The tip can be in one of two positions:

  1. High: T6-T10 (in descending aorta) – optimal position
  2. Low: L3-L5 (at the aortic bifurcation and below major aortic branches) – suboptimal position

Never use a UAC between T10 and L3, as it poses a risk to the branches of the descending aorta.

UVC: a straight catheter is seen on an x-ray. The tip should be at the level of the diaphragm, just outside the cardiac silhouette (between T8-T10)

PERCUTANEOUS LONG LINES

How big should they be?

24G single lumen catheters (for those >1kg): 15, 30, or 50cm long and go through a peelable cannula as part of the set.

28G single lumen catheters (for those <1kg) (i.e. Premicaths): 20cm long and go through a peelable cannula as part of the set or the yellow 24G venous cannulas you’ll find on the wards.

Where do I go?

Select a straight and large vein, e.g. antecubital fossa or long saphenous vein. Axillary and scalp veins are occasionally used.

Where do I stop?

Measure the insertion length using sterile tape from the insertion site along the course of cannulation to the sternum (if coming superiorly to the heart) or to the xiphisternum (if coming inferiorly to the heart).

Upper limb and scalp long line tips should sit in the superior vena cava. If inserted into a left upper limb or scalp vein, they should cross the midline to the right.

Lower limb long-line tips should sit in the inferior vena cava. If inserted into a left lower limb vein, they should cross the midline to the right.

All long-line tips should lie outside the right atrium.

URINARY CATHETERS

How big should they be?

4Fr is for preterm and small for gestational age infants and 6-8Fr is for term infants.

Where do I go?

Through the urethra.

Where do I stop?

Until urinary flow is seen (tip: you may feel resistance at the bladder neck). Inflate the catheter balloon with sodium chloride 0.9% to secure it.

CEREBRAL FUNCTION MONITORS

How big should they be?

Cerebral function monitor (CFM) electrodes are usually one-size only. They are either subcutaneous needle electrodes or disc/cup electrodes. Before putting disc/cup electrodes on the skin, put skin prep gel to the convex aspect and conductive gel to the concave aspect.

Where do I go?

For single-channel CFM, the two active electrodes should be placed biparietally, and the third active electrode (noise suppression electrode) should be placed frontosuperiorly (as below).

Where do I stop?

Do not insert needle electrodes into the fontanelle. Once complete, secure with steristrips if required.


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