Paediatrics: Umbilical arterial catheter

2021-03-05 12:00 AM

An umbilical arterial catheter (UAC) can be used in newborns up to 48hr old for invasive BP monitoring, continuous blood gas monitoring, blood sampling, fluid infusion, and/or exchange transfusion.

Umbilical arterial catheter

An umbilical arterial catheter (UAC) can be used in newborns up to 48hr old for invasive BP monitoring, continuous blood gas monitoring, blood sampling, fluid infusion, and/or exchange transfusion.

Site

To avoid the origins of the coeliac, mesenteric, and renal arteries, the tip of the catheter should be positioned in the aorta above the diaphragm at the T8–T10 vertebral level or in the distal aorta at the L3–L4 level.

Equipment

  • Antiseptic solution, e.g. 0.5% chlorhexidine.
  • Sterile surgical instruments including fine forceps, blunt-ended dilator probe, scalpel, artery forceps, scissors, suture forceps, sutures.
  • Sterile drapes, gown, gauze swabs, and gloves.
  • Umbilical catheters: 3.5Fr if birth weight <1500g; 5.0Fr for newborns1500g. Catheters with a terminal electrode can be used for continuous measurement of arterial O2 and CO2 concentrations.
  • 3-way taps, IV extension sets, syringes, cord ligature.
  • 5–10mL syringes, one containing heparinized saline (1Ut/mL).
  • BP transducer if monitoring is intended.

Procedure

  • Monitor baby closely during the procedure, e.g. O2saturation monitoring.
  • An assistant should hold the baby’s legs down with the infant supine.
  • Calculate the distance (cm) to insert the catheter from the umbilicus to the aorta at T8–10 level using the formula:
  • Insertion distance = 3 × weight (kg) + 9 + umbilicus stump length.
  • To control bleeding, tie a cord ligature around the umbilicus stump.
  • Catheter insertion should be performed using a strict aseptic technique.
  • Wash hands and put on sterile gloves, gown, +/– surgical mask.
  • Connect a 3-way tap to catheter and prime with heparinized 0.9% saline (do not use heparinized saline if coagulation testing is required).
  • Clean cord and periumbilical area with an antiseptic solution.
  • Surround the periumbilical area with sterile towels to create a sterile field.
  • Clamp the umbilical cord horizontally with artery forceps 0.5–1cm above umbilical skin. Using the artery forceps as a guide, cut the umbilical cord horizontally and immediately below with the scalpel.
  • Identify the two umbilical arteries and umbilical vein (see Fig. 7.2).
  • Dilate the end of one of the arteries with fine forceps or a probe until wide enough for the catheter tip to be easily introduced.
  • Gently advance catheter the calculated distance (see formula). If resistance is met put gentle traction on the umbilicus using artery forceps as this often eases insertion down the spiral umbilical artery.
  • Aspirate blood to confirm the position and take the required samples. Note: arterial blood should pulsate and still bleed if the catheter hub is held above the infant (unlike blood from the umbilical vein).
  • Secure catheter by fixing a zinc oxide flag around the catheter and then suture it to the stump (see Fig. 7.2). Ligate remaining vessels with a separate purse-string suture. Remove cord ligature and check for bleeding.
  • Connect catheter to 3-way tap and IV infusion set. BP monitoring can be performed by connecting the appropriate pressure transducer.
  • Confirm correct placement with a combined CXR/AXR. The catheter should loop initially downwards to the pelvis as it traverses the iliac arteries before ascending up the aorta.
  • Check perfusion of the perineum and lower limbs. If ischaemia occurs, this usually may be corrected by an IV bolus of 0.9% saline or albumin. If ischaemia remains, remove the catheter immediately.
  • Following insertion, the abdomen should remain exposed to allow immediate observation of any haemorrhage, e.g. from accidental removal of the catheter.

As soon as the catheter is no longer required, it should be removed. Cut the surrounding suture, then slowly withdraw it, taking several minutes to remove the final few centimetres from the artery. Then apply pressure or suture to limit any bleeding.