Collecting cord gases with an intact cord

The need to collect cord blood gases is a frequent barrier to a baby receiving delayed or optimal cord clamping within a hospital setting, despite guidelines here in the UK and across the world recommending delayed cord clamping (NICE, 2014; RCOG, 2015; WHO, 2014).

I am regularly contacted by individuals asking about this scenario. There is now strong evidence to suggest collection of umbilical cord gases from an intact cord is preferable since it is understood that delayed cord clamping alters several acid-based parameters and lactate values.

In this blog I explore the new commentary evidence 'Delayed cord clamping and cord gas analysis at birth' by Xodo, Xodo and Berghella (2018) and I collaborate with Jessica Rawlinson (Student Midwife Studygram) who has kindly drawn the visual steps I prepared (using the evidence) to performing umbilical cord gas analysis with an intact cord.

Why are cord gases important?

There are a number of reasons a practitioner may be keen to perform umbilical umbilical cord gas analysis at birth.

(i) to evaluate the status of the baby at birth

(ii) to evaluate labour and delivery events retrospectively

(iii) to evaluate the quality of clinical assistance

(iv) to assist in cases of a medico‐legal litigation (Xodo, Xodo and Berghella, 2018)

Whilst there is no universal agreement about when this should happen, most commonly it may be due to abnormal CTG , emergency caesarean delivery, Apgar score <7 at 5 min, intrauterine growth restriction/ small for gestational age and preterm births.

Xodo, Xodo and Berghella (2018) provide an excellent rationale for cord gas analysis and the biochemical process occurring in the blood during and after birth. For the purposes of this blog I won't go into detail on this, but instead highlight that there is evidence to suggest time dependant implications for the accuracy of umbilical cord gas samples taken from cords following delayed cord clamping (Valero et al., 2012), delayed sampling (Wiberg, Källén and Olofsson, 2008) and delayed analysis (Armstrong, 2006).

Changing practice; a new approach

Xodo, Xodo and Berghella (2018) and Mercer (2014) both champion the outcomes of Andersson's (2013) important randomised control trial of 382 healthy term infants. They successfully collected umbilical cord blood gas samples from:

- infants with DCC of 180 seconds (n= 130) and

- infants with ICC (n=139)

In the DCC group, arterial and venous umbilical cord gas samples were collected within 30 seconds after birth and in the ICC group, similar samples were drawn from a segment of the umbilical cord by 10 minutes after delivery. Each sample was analyzed within 20 minutes and no significant differences between the 2 groups were reported with the exception of a lower arterial oxygen tension level noted in the ICC group (Mercer, 2014).

The upshot is, blood can easily be collected from the intact umbilical cord in the same manner used for detached umbilical cords (Mercer, 2014). With collection of the arterial and venous umbilical cord gas samples within 30 seconds of birth preferable (Andersson et al, 2013). Without any effect on either the accuracy of umbilical artery gas analysis or the transfusion of blood through DCC (Xodo, Xodo and Berghella, 2018).

Steps for performing cord gas collection with an intact cord

Prepare

Cord blood taken for the purposes of gas analysis should be taken with pre-heparinised syringes - have these ready in the room, differentiated by blue (arterial) and red (venous) caps. Have a patient identity sticker ready to wrap around the samples once taken.

Baby is born, dried and stimulated and placed skin to skin with the mother.

1. Stabilise the cord near the perineum with as minimal manipulation as possible

2. Be careful to protect yourself and mum from any accidental needlestick injury (perhaps place a rolled towel on mums thigh or pelvis as a barrier)

3. Use a small 25 or 27 gauge needle to take two blood samples, one from the umbilical artery and the other from the umbilical vein

4. Leakage from the punctured umbilical cord is minimal, but gentle pressure can be applied for 30 seconds afterwards if necessary.

5. It is important that once the blood has been taken to replace the needle with the syringe cap, as this helps to delay clotting and preserves the gasses for analysis

6. Allow for delayed or optimal cord clamping before clamping and cutting of the umbilical cord.

For those visual learners, please see the diagram below.

Visual infographic by Jessica Rawlinson and Hannah Tizard

Hope this helps with practice change. Over and out Hannah x