In neonates, blood samples obtained from an artery or vein are regarded as the ‘gold standard’ for laboratory specimens as they are perceived to reflect the body's true values. However, sampling from arteries and veins is not always feasible and the risks associated with indwelling catheters, such as thrombosis and infection, limit the duration for which they can be left in situ (Bruck, 1991). Furthermore, in hospitalised sick neonates, repeated venous sampling can limit the number of intravenous sites available for the administration of total parenteral nutrition or medications. Capillary blood sampling, therefore, remains the preferred method of obtaining small amounts of blood for laboratory analysis. Compared with venepuncture or arterial puncture, this procedure is easier and safer. Furthermore, the results of most laboratory tests of these samples have been found to be comparable to those from blood drawn from arterial catheters (Yang et al, 2002).
This article describes best practice for neonatal blood sampling. It also recounts health professionals' clinical experience of using the Neoheel Safety Lancet (Smiths Medical), which is designed to produce high-quality samples at the first attempt with minimal pain and discomfort.
Blood sampling in the heel
Following consent from their parent or guardian, all babies born in the UK undergo newborn screening on day 5 of life. This procedure consists of taking a blood sample from the heel to test for conditions including cystic fibrosis, sickle cell disease, congenital hypothyroidism and inherited metabolic diseases (phenylketonuria, medium-chain acyl-CoA dehydrogenase deficiency, maple syrup urine disease, isovaleric acidemia, glutaric aciduria type 1 and homocystinuria) (NHS, 2018).
If a neonate needs specialist intensive care, other point-of-care tests are required, which are also predominantly performed via a heel prick. These blood samples can be used for a variety of tests, including haematological analysis (e.g. complete blood cell count), biochemical analysis (e.g. electrolyte, glucose and bilirubin levels, as well as therapeutic drug monitoring) and glucose estimation.
Best practice
When extracting a blood sample, the main risks to the neonate are pain, local damage to the nerves and blood vessels, bleeding, infection and scarring (Meehan, 1998). A good technique will avoid placing the neonate at risk, ensure accurate and faster results, and limit distress for the baby.
A neonate's skin is integral to their wellbeing, as it provides a barrier against the ingress of bacteria, thereby protecting against infection. Precautionary measures must, therefore, be undertaken when invasive clinical procedures that involve breaking the skin's protective barrier are performed. This includes adequately cleansing the skin before taking each blood sample.
Anyone who takes blood from children and neonates, most commonly medical and nursing staff, must be assessed as competent and experienced in venepuncture techniques. A standardised, evidence-based, sampling technique will reduce pain and psychological trauma (World Health Organization (WHO), 2010). A heel prick is the most effective procedure for blood sampling in infants aged between birth and 6 months weighing approximately 3–10 kg.
In neonates, the recommended site for sampling is on the plantar surface laterally beyond an imaginary line drawn posteriorly from between the fourth and fifth toes to the heel and medially from the middle of the great toe to the heel (Figure 1) (Blumenfeld et al, 1979).
When using the whole plantar surface, an automated incision device with a penetrative depth of no more than 1 mm is recommended (Public Health England, 2016).
The following equipment is needed for neonatal heel blood sampling:
Preparing for the procedure
Capillary blood sampling is a painful procedure, as highlighted in a study that showed neonatal heel pricks and venepunctures administered without analgesia caused moderate to severe pain (Bellieni and Johnston, 2016). The authors recommended that analgesia be given to reduce the pain and discomfort, and that comfort measures, such as breastfeeding and/or placing the neonate skin-to-skin with either parent, should be implemented during the procedure. Skin-to-skin appears to be safe and effective, as measured both by composite physiological and behavioural pain indicators and, independently, using heart rate and crying time (Johnston et al, 2017).
Sucrose can be given as analgesia in accordance with local guidelines. Sucrose is effective in reducing procedural pain caused by procedures such as heel-prick sampling, with minimal to no reported adverse effects. Small doses of 24% sucrose (0.01–0.02 g) are efficacious in preterm infants, and larger doses (0.24–0.50 g) will reduce the amount of time term infants spend crying. There is moderate-quality evidence that sucrose in combination with other non-pharmacological interventions, such as non-nutritive sucking, is more effective than sucrose alone (Stevens et al, 2016).
An assessment of the baby's ability to tolerate handling must be made before obtaining the sample.
The procedure should be explained in full to the parents or guardians in advance, and informed consent gained.
The procedure
Types of lancet
The higher the gauge of a lancet, the smaller the needle diameter. A low-gauge needle can be quite uncomfortable for the neonate and a higher gauge may not provide sufficient blood for testing (NHS Clinical Evaluation Team, 2018).
In a randomised blinded study conducted by Vertanen et al in 2001, 100 preterm babies were subjected to heel stick sampling from either manual or automatic lancets. The results showed that, to obtain a sufficient volume of blood, an average of 2.6 times more punctures were needed for the conventional manual lancet compared with automatic incision. The manual lancet was associated with more bruising on the heels, leg and ankle, and more signs of inflammation than the automatic version. Finally, the skin healed more rapidly when the automatic lancet was used (Vertanen et al, 2001).
A randomised controlled trial published 4 years later showed that use of a safety lancet, which facilitated an arched incision 1 mm deep, was associated with less bruising, required fewer punctures to obtain sufficient volumes of blood, and achieved better quality samples when compared with the comparator, which produced a narrower guillotine incision 2 mm deep. The two devices were cost neutral when all aspects of the blood spot sample were taken into account (Glenesk et al, 2006).
The Neoheel Safety Lancet
The Neoheel Safety Lancet (Smiths Medical) collects blood samples from neonates, infants and toddlers for testing of all the conditions described above. It has an automated spring-loaded design, and the high-speed sweeping motion of its stainless steel microblade is limited to a depth of 1 mm, which is just above the location of most nerve fibres (Cavanagh, 2009). The lancet is available in four configurations, based on neonatal developmental levels (weight and age) (Table 1). In this way, the depth and length of the incision is determined by the neonate or infant's size, enabling the collection of a high-quality sample with less pain and less trauma to delicate tissues and nerve endings.
| Micro-Preemie: low birth weight <1 kg | Preemie: low birth weight 1–2.5 kg | Newborn: birth–6 months 2.5–9 kg | Toddler: 6–24 months >9 kg | |
|---|---|---|---|---|
| Incision depth | 0.65 mm | 0.85 mm | 1.00 mm | 2.00 mm |
| Incision length | 1.4 mm | 1.75 mm | 2.50 mm | 3.00 mm |
| Blood volume | Medium | Medium | Medium | Medium |
| Packaging | One case contains four shelf boxes of 50 units (200 units in total) | |||
Automated spring-loaded lancets allow for the collection of blood specimens with smaller levels of plasma haemoglobin (Kazmierczak et al, 2002). In addition, as demonstrated earlier by Glenesk et al (2006), the arc-shaped design reduces the number of heel puncture sites, the time taken to complete the test on babies and the time they spend crying (Figure 3). Its safety features include an integrated safety tab that prevents premature activation and the risk of potential contact with loose parts. The textured sides of the lancet are designed to provide a secure grip to help prevent the need for a second heel prick. The microblade instantly retracts to a permanently locked position to prevent accidental needle-stick injury to both the neonate and health professional.
The secured grip can prevent the need for further heel pricks, leading to potential to cost-savings as the health professional may only need to use one lancet per procedure.
Case studies
For years, neonatal blood samples taken at the laboratory services at St Elizabeth Medical Center, New York, US, for bilirubin testing were collected using a lancet that appears to have a punch-action blade. A variety of different techniques were used to obtain a sufficient sample. In general, babies tended to be fussy and move around; on occasion, multiple attempts were required. This made for unhappy babies and parents/guardians.
Four months ago, the facility switched to the Neoheel Safety Lancet. In contrast to the previous lancet, it uses a sweeping action when collecting a blood sample. With this lancet, the neonate's usual initial reaction is simply to jerk or pull their leg/foot away; only one baby has cried out after the lancet was discharged, but then quickly went back to sleep. The process is quicker and delivers a better blood flow. One additional feature of the lancet noticed during clinical practice was that its textured grip made it easier to hold and use, especially if the neonate was unsettled. The staff also appreciated its integrated safety tab: if adjustments were required, the tab could easily be engaged to avoid accidental discharge and the risk of needlestick injury.
Some case studies on the use of this lancet in 3-day old neonates are described below. In each case, a Neoheel lancet (1.0 mm depth, 2.5 mm length) was used. None of the cases required ‘re-pokes’ or ‘re-collects’.
Case studies
Patient 1
This male neonate was asleep when he arrived and woke when his socks were removed for the assessment. When the lancet was discharged, he let out a low squeak, but did not cry at any time during the process.
Patient 2
This male neonate remained asleep in his carrier during the procedure. When the lancet was discharged, he opened his eyes and cried out, trying to free his leg from our hold, but after a moment went back to sleep.
Patient 3
This female neonate arrived in our outpatient laboratory facility asleep in her mother's arms. During setup, she was laid down on the table and began to cry in protest at not being held. Her mother gave the infant a small nook/pacifier to soothe her. The neonate wriggled around during the assessment and procedure, but did not cry.
Patient 4
A young couple, who had had their first child, presented at the laboratory service. They had been to other outpatient services for bilirubin testing, only to have their newborn ‘stuck’ multiple times with lancets in unsuccessful blood-collection attempts. There were multiple lancet marks on the neonate's foot, which were hard and callused, most likely caused by the collector squeezing the location of the blood flow, instead of ‘milking’ it. The parents were very anxious about having their baby's foot punctured yet again.
The laboratory services inpatient supervisor explained that she was sampling a new lancet with much success. She eased the parents' worries at the words ‘trial’ and ‘new’ by explaining that, unlike other lancets, which have more of a punch action, this lancet ‘swoops’ and encourages blood flow. She said she was confident their baby would not be subjected to multiple attempts and discomfort. The parents appeared to relax.
The assessment and blood collection process took less than 5 minutes, during which time the parents continued to hold their baby's hands. After the procedure had been completed, both parents thanked the supervisor. The father shook her hand and the mother smiled, while holding her baby once again, thanking her over and over.
Following these experiences, it was decided to continue using this lancet in the laboratory service.
Conclusion
Obtaining a capillary sample and interpreting the results is a frequent and necessary practice in the care of newborn babies and sick neonates. An adept practical skill is needed to obtain a capillary blood sample, and knowledge of how to avoid causing unnecessary pain, trauma and distress to the neonate is also essential. The Neoheel Safety Lancet has proven features that enable health professionals to meet all of these essential requirements.