Cord blood and neonatal capillary blood sampling
Cord blood is a sample of blood taken at birth from a baby’s umbilical cord. It is not a requirement to obtain cord blood routinely (NICE 2014) (Box 48.1). The umbilical cord consists of three closely adjacent blood vessels; two arteries, which carry deoxygenated blood from the fetus, and one vein, which carries oxygenated blood to the fetus (Figure 48.1). The single vein is usually the largest structure and hence easier to obtain a sample from. If only one sample is required then either the vein or artery may be used. Umbilical cord gas analysis will, however, require a sample from both the vein and artery.
- Do not clamp the cord earlier than 1 minute following the birth unless there is concern about the baby’s condition (NICE 2014). Samples need to be collected within 60 minutes of birth, having noted the time of cord clamping to ensure correct interpretation of results.
- Equipment: apron, sterile gloves, two heparinised syringes with needle, sharps box, labels to identify the sample to the baby and as arterial or venous.
- Wash hands. Don gloves, apron and eye protection. Refer to local infection control policies for further advice, particularly relating to maternal blood-born viruses.
- Double clamp the umbilical cord 10 cm apart. Clamp as close to the fetal end as possible to facilitate access to remaining cord in the event of repeat sampling.
- Identify an artery and vein within the umbilical cord.
- Insert the needle into the appropriate vessel at a 45 degree angle and withdraw the blood. Ensure the needle is well placed into the centre of the vessel to avoid contamination of blood with air (Figure 48.1). If air bubbles are seen in the sample, safely discard and repeat with a new syringe and needle.
- Withdraw the needle from the cord. Safely remove needle from syringe and discard in compliance with local policy.
- Place the bung on the end of the syringe. Gently agitate the syringe by rolling between thumb and forefinger to ensure that heparin is dispersed appropriately to prevent clotting of the sample. Label syringes (Figure 48.2).
- When samples are taken for umbilical cord gas the analysis should be performed within 30 minutes, as samples will deteriorate after this time.
- Inform doctors of the blood gas results and document findings appropriately.
- Discuss the findings with the parents.
Cord blood is rich in stem cells. The NHS national blood transfusion service collects, stores and supplies cord blood from voluntary contributions. Cord blood collected is then used to treat patients suffering from life-threatening diseases. Currently, some hospitals within the greater London area have subscribed to this service. For more information visit NHS Blood Transfusion at: www.nhsbt.nhs.uk/cordblood/about/
A heel puncture is a simple and convenient method of obtaining a blood sample from a baby. This technique is usually performed for tests including blood sugar monitoring, bilirubin levels, full blood count analysis and newborn blood spot screening. In the event that a capillary sample is required for newborn blood spot screening, it is essential that midwives adhere to current national guidance such as NHS newborn blood spot screening programme (Public Health England 2016). This will ensure that parents are provided with evidence-based information to enable them to give the required fully informed verbal consent. Puncturing the skin on the baby’s heel is associated with increased pain. Mothers should therefore be encouraged to be involved in the procedure by providing skin-to-skin contact, breastfeeding or use of a pacifier as this is known to minimise discomfort, and make the baby feel secure (Uga et al. 2008). Health professionals need to recognise the real anxiety and stress that parents may experience before and during blood sampling from their baby.
Procedure adapted from Public Health England (2016):
- Equipment – see Figure 48.3.
- Examine the baby’s heel to identify an appropriate puncture site. Ensure that baby and mother (if she is present) are in a comfortable and secure position.
- Clean the heel with cotton wool/gauze soaked in tepid tap water. It is not necessary to warm the baby’s foot first but it is useful to dress the baby warmly to facilitate a good blood flow.
- Wash hands and apply gloves.
- Hold the foot gently yet securely and puncture the heel using an automated device no deeper than 2 mm for a term baby. Use either the external or internal limits of the calcaneus (Figure 48.4). If repeated sampling is required then use an automated incision device of no more than 1 mm depth within the plantar area of the foot to reduce risk of trauma and infection.
- Allow the foot to hang to encourage blood to flow. Do not squeeze the foot.
- Collect the blood required into the capillary tube/blood bottle/screening card.
- When the sample is complete, wipe away excess blood with gauze/cotton wool and apply gentle pressure.
- Apply a hypoallergenic plaster if required and remind parents to remove 2 hours following the procedure.
- Remove gloves, wash hands and dispose of equipment according to local policy.
- Label samples immediately before leaving the bedside/cot-side/bedroom.
- Document the procedure according to local policy. Depending on rationale for sampling, inform doctors of result and discuss implications of findings with parents.