Aim:
End-tidal CO
2
(Et
CO2
) is the standard in operative care along with pulse oximetry for ventilation assessment. It is known to be less accurate in the infant population than in adults. Many neonatal intensive care units (NICU) have converted to utilizing transcutaneous CO
2
(tcP
CO2
) monitoring. This study aimed to compare perioperative Et
CO2
to tcP
CO2
in the pediatric perioperative population specifically below 10 kg, which encompasses neonates and some infants.
Methods:
After IRB approval and parental written informed consent, we enrolled neonates and infants weighing less than 10 kg, who were scheduled for elective surgery with endotracheal tube under general anesthesia. P
CO2
was monitored with Et
CO2
and with tcP
CO2
. Venous blood gas (Pv
CO2
) samples were drawn at the end of the anesthetic. We calculated a mean difference of Et
CO2
minus Pv
CO2
(Delta Et
CO2
), and tcP
CO2
minus Pv
CO2
(Delta tcP
CO2
) from end-of-case measurements. The mean differences in the NICU and non-NICU patients were compared by t-tests and Bland–Altman analysis.
Results:
Median age was 10.9 weeks, and median weight was 4.4 kg. NICU (n=6) and non-NICU (n=14) patients did not differ in Pv
CO2
. Relative to the Pv
CO2
, the Delta Et
CO2
was much greater in the NICU compared to the non-NICU patients (−28.1 versus −9.8, t=3.912, 18 df,
P
=0.001). Delta tcP
CO2
was close to zero in both groups. Although both measures obtained simultaneously in the same patients agreed moderately with each other (r =0.444, 18 df,
P
=0.05), Bland–Altman plots indicated that the mean difference (bias) in Et
CO2
measurements differed significantly from zero (
P
<0.05).
Conclusions:
Et
CO2
underestimates Pv
CO2
values in neonates and infants under general anesthesia. TcP
CO2
closely approximates venous blood gas values, in both the NICU and non-NICU samples. We, therefore, conclude that tcP
CO2
is a more accurate measure of operative Pv
CO2
in infants, especially in NICU patients.