Background The 2015 neonatal resuscitation guidelines added ECG as a recommended method of assessment of an infant’s heart rate (HR) when determining the need for resuscitation at birth. However, a recent case report raised concerns about this technique in the delivery room.
Objectives To compare accuracy of ECG with auscultation to assess asystole in asphyxiated piglets.
Methods Neonatal piglets had the right common carotid artery exposed and enclosed with a real-time ultrasonic flow probe and HR was continuously measured and recorded using ECG. This set-up allowed simultaneous monitoring of HR via ECG and carotid blood flow (CBF). The piglets were exposed to 30 min normocapnic alveolar hypoxia followed by asphyxia until asystole, achieved by disconnecting the ventilator and clamping the endotracheal tube. Asystole was defined as zero carotid blood flow and was compared with ECG traces and auscultation for heart sounds using a neonatal/infant stethoscope.
Results Overall, 54 piglets were studied with a median (IQR) duration of asphyxia of 325 (200-491) s. In 14 (26%) piglets, CBF, ECG and auscultation identified asystole. In 23 (43%) piglets, we observed no CBF and no audible heart sounds, while ECG displayed an HR ranging from 15 to 80/min. Sixteen (30%) piglets remained bradycardic (defined as HR of <100/min) after 10 min of asphyxia, identified by CBF, ECG and auscultation.
Conclusion Clinicians should be aware of the potential inaccuracy of ECG assessment during asphyxia in newborn infants and should rather rely on assessment using a combination of auscultation, palpation, pulse oximetry and ECG.
- heart rate
- neonatal resuscitation
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Contributors Conception and design: KJB, PGD and GMS. Data collection: SP, P-YC, ALS and GMS. Data analysis and interpretation, drafting of the article, critical revision of the article for important intellectual content and final approval of the manuscript: all authors.
Funding PGD is supported by an NHMRC Practitioner Fellowship #1059111. The study was supported by a Grant-in-Aid from the Heart and Stroke Foundation Canada (grant number: G-15-0009284).
Disclaimer The sponsors of the study had no role in study design, data collection, data analysis, data interpretation or writing of the report.
Competing interests None declared.
Patient consent Not required.
Ethics approval The original studies were conducted in accordance with Animal Research Reporting of In Vivo Experiments guidelines and approved by the Animal Care and Use Committee (Health Sciences) University of Alberta (AUP00001764, AUP00002151)
Provenance and peer review Not commissioned; externally peer reviewed.