Blood gas monitoring in the preterm neonate

Using transcutaneous monitoring (TCM) can help you protect and guide the treatment of the most fragile patients in the NICU [1,2]. TCM devices can be used in all stages of neonatal care — immediately after transition at birth, in the NICU, and during inter-hospital transfers [1,2].

Monitoring neonatal ventilation

Managing neonatal ventilation is a delicate balance: both too little and too much oxygen and carbon dioxide is harmful for the neonate, highlighting the importance of close ventilation monitoring and management.

Too high or low O₂ and CO₂ levels have been shown to be a risk factor for mortality, necrotising enterocolitis (NEC), retinopathy of prematurity (ROP), bronchopulmonal dysplasia (BPD), intraventricular hemorrhage (IVH), and cerebral injury among others (Table 1).

Table 1. Adverse effects of high and low O2 and CO2 levels in the neonate [3-7]

Managing neonatal ventilation can be achieved using invasive (blood gas) and non-invasive measurements (transcutaneous measurement, oxygen saturation measurement, end tidal measurement). Each method has its advantages and disadvantages and should optimally be used to supplement each other (Table 2)[3].

Table 2 – Advantages and disadvantages of different monitoring methods [8-11]

Blood gas analyses give the most precise measurement of O₂ and CO₂ values; however, they are invasive, can cause pain for the infant, induce blood loss, and may cause temporary disturbances in the cerebral blood flow [12]. Furthermore, the blood gas measurement only shows a single time point of the neonatal oxygenation and ventilation status and does not reflect the intermittent changes between two samples.

Oxygen saturation (SpO₂) monitoring is used as standard of care for monitoring of oxygenation of neonates. It is non-invasive, instantaneous, and shows continuous values. Though SpO₂ is good at detecting hypoxia, titration of ventilation can be difficult, with a risk of overlooking hyperoxia for SpO₂ values ≥95-98% [8].

End-tidal CO₂ (ETCO₂) monitoring can be used to confirm endotracheal tube placement in neonates and can give continuous values for infants on a ventilator or with respiratory support [2]. It is generally not as precise as tcpCO₂, especially for infants with respiratory disease and/or ventilation/perfusion mismatch, a situation commonly occurring in the NICU [2,10].

Transcutaneous measurement of oxygen (tcpO₂) and carbon dioxide (tcpCO₂) can be used as a supplement to blood gases to monitor oxygenation and ventilation status of neonates.

Using continuous tcpCO₂ values allows for proactive rather that reactive treatment, and might be used to diagnose adverse events like pneumothorax earlier [13]. The transcutaneous values of CO₂ has shown a good correlation with arterial values and can be used even for extremely premature (gestational age < 28 weeks) and extremely low birth weight (birth weight < 1000 grams) infants [14].

One study showed that tcpO₂ was superior to SpO₂ to guide titration of oxygen delivery to preterm neonates, with less time spent at high or low arterial oxygen tensions [15].

Reducing pain and blood loss

Research shows that the preterm infant may be subject to painful procedures several hundred times during the first weeks of life, with blood samples being the most common source of pain [16].

Using a non-invasive method to continuously evaluate the O₂ and CO₂ levels may reduce the number of painful procedures the preterm infant experiences. One center showed a 25% reduction in number of blood draws for ventilated preterm infants after introduction of transcutaneous CO₂ monitoring [17].

Summary

Transcutaneous monitoring of O₂ and CO₂ is painless and non-invasive, feasible for even the smallest and most premature neonates, has shown good correlation with arterial values, and can help guide the clinician in optimising ventilation settings within a large range of clinical settings.

References

1. Bresesti I, Bruckner M, Mattersberger C, Baik-Schneditz N, Schwaberger B, Mileder L et al. Feasibilty of Transcutaneous pCO₂ Monitoring During Immediate Transition After Birth-A Prospective Observational Study. Front Pediatr 2020; 8:11.
2. Hochwald O, Borenstein-Levin L, Dinur G, Jubran H, Ben-David S, Kugelman A. Continuous Noninvasive Carbon Dioxide Monitoring in Neonates: From Theory to Standard of Care. Pediatrics 2019; 144(1).
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