Portal de Periódicos da CAPES

Assessing Heart Rate at Birth: Auscultation Is Still the Gold Standard

2016; Karger Publishers; Volume: 110; Issue: 3 Linguagem: Inglês

10.1159/000446527

1661-7819

Ola Didrik Saugstad, Roger F. Soll,

Neuroscience of respiration and sleep

According to the International Liaison Committee on Resuscitation (ILCOR), heart rate and respiration are the two most important vital signs to assess in the newborn during the so-called golden minute [1]. If the heart rate is less than 100 beats/min (bpm) and the newborn is not breathing adequately, positive pressure ventilation should be considered. If the heart rate is less than 60 bpm and not increasing in spite of adequate ventilation, chest compressions should be started. Although these limits are arbitrary and not evidence based, they are still important as guidance for the clinician as he or she applies the resuscitation algorithm. Because the assessment of heart rate is fundamental to these recommendations, the ILCOR recommendations should have indicated the expected rise in heart rate during appropriate ventilation. We believe our findings of a heart rate increase of 20 bpm during the first 30 s of appropriate ventilation could be a reasonable target [2]. Given the importance of detection of the heart rate of the newborn immediately after birth, it was concerning when Kamlin et al. [3] reported in 2006 that auscultation of the heart of vigorous low-risk term infants in the delivery room was inaccurate and underestimated the heart rate obtained by ECG [i.e. 154 (SD 22) vs. 167 (SD 19) bpm] [3]. It can be argued that it is not the auscultation by stethoscope that is inaccurate but rather the method of estimating the heart rate by counting for only 6 s and then multiplying by 10. By counting the heart rate for 10 instead of 6 s, much of this inaccuracy could be eliminated. The next step by Kamlin et al. [4] was to compare heart rates measured both by ECG and preductal pulse oximetry, finding a mean difference of -2 (SD 26) bpm. For 5 infants receiving advanced resuscitation (intubation and chest compressions), very good agreement was also found using these modalities, with a difference of less than 1 bpm. The authors concluded that heart rate by pulse oximetry 'is of sufficient accuracy to be of use to clinicians and researchers alike'. One significant challenge in using these modalities was that 40% of the infants were excluded due to technical problems, mainly failure to acquire a heart rate signal by ECG [4]. Several studies have recently confirmed that a reliable heart rate is obtained much earlier and more efficiently with ECG than with pulse oximetry [5,6,7,8,9,10]. In one study, the median difference in obtaining a reliable heart rate was 84 s [7]. In another study, it was shown that during the first minute of resuscitation 93% of the infants had a heart rate detected by ECG, compared to only 56% for pulse oximetry [6]. In a recent study, Van Vonderen et al. [9] showed that pulse oximetry measured a lower heart rate at birth compared to ECG, especially in the first 2 min before a stable pulse oximetry signal was obtained.Recently, Philippos et al. [11] summarized this topic and concluded that auscultation with a stethoscope over the precordium is superior to palpation of the umbilical cord. Both of these methods, however, represent intermittent (though frequent) sampling techniques. Although ECG is the current gold standard to continuously monitor an infant's heart rate in the NICU, there are several limitations that prevent ECG from being universally used for heart rate assessment in the delivery room. Philippos et al. [11] therefore suggest that pulse oximetry is an accurate method by which to measure heart rate routinely during neonatal resuscitation.Based on this recent background, the article by Linde et al. [12] in this issue of Neonatology is of great interest. A new dry electrode, developed by Laerdal Medical, which includes an arch-shaped ECG sensor that fits over the thorax or abdomen of the newborn, was tested in healthy newly born term infants. The median time from birth to successful placement of the ECG sensor was 3 s (25th and 75th percentile: 2.5 s), and they reported that ECG signals were obtained 7 s after the baby was born. This is approximately 20 s earlier than previously reported [6] and is so fast that video documentation would have been appreciated. The heart rate immediately after birth was approximately 120 bpm, which is higher than previously reported by Dawson et al. [13.]Although the electrode has only been studied in healthy full-term infants, the technique is highly promising. A caveat is, however, that only 62% of the signals were of sufficiently good quality. It is therefore difficult to understand how ILCOR at the present stage suggest that the heart rate immediately after birth should be determined by ECG. This is very unfortunate advice both because most birth places in the world do not have access to ECG and because ECG technology is not developed sufficiently at this time. There is some concern regarding a conflict of interests between Linde et al. [12] and the ILCOR recommendations. Two of the coauthors of the article of Linde et al. [12] had an active role in the ILCOR recommendations. These authors have close ties to Laerdal Medical and received research support from Laerdal Medical for that current research as well as other projects. This relationship is not well established in the research support stated in the ILCOR documents [1]. There is a lack of transparency regarding the relationship to the study sponsors and the recommendations and suggestions proposed in the ILCOR paper. This is especially important because it can be argued that the ILCOR suggestion of applying ECG for heart rate detection during newborn resuscitation is unfortunate and premature and therefore could cause harm.That is not to say that improved methods of heart rate assessment might not lead to clinical benefits in the golden minutes after delivery. The potential future direction for heart rate assessment at birth is exciting. In addition to ECG monitoring, Philippos et al. [11] noted that newer methods of heart rate assessment might include Doppler ultrasound and forehead reflectance photo plethysmography. Heart rate monitoring might also include wearable, low-power context-aware ECG monitoring systems with bluetooth capabilities for data transmission to a smartphone. A wireless ECG sensor can be worn around a finger and transmit heart rate data via Wi-Fi. Even techniques that measure heart rate without touching the skin could be a future option. Perhaps most convenient for clinicians will be a digital stethoscope that can transmit heart rates to a smartphone [11]. Future technology certainly will be different. However, until then, auscultation of the heart rate with a stethoscope should still be the method of choice for the initial heart rate assessment in the delivery room.O.D. Saugstad has received funding from the Laerdal Foundation for Acute Medicine and is a recipient of the Laerdal Honorary Award in Acute Medicine (1995). R.F. Soll is the president of the Vermont Oxford Network and coordinating editor of Cochrane Neonatal.