Neonatal sepsis refers to an infection involving the blood stream in newborn infants less than 28 days old (11).
The clinical manifestations range from subclinical infection to severe focal or systemic disease (12).
Many infants with sepsis develop cardiovascular instability; preterm infants are particularly vulnerable due to the unique features of their cardiovascular function and reserve (13).
The hemodynamic status of sick newborn infants is often assessed by clinical variables such as heart rate, blood pressure and capillary refill time which have been demonstrated to be misleading in their accuracy (14).
In the care of critically ill patients, hemodynamic assessment is crucial for both diagnosis and management; however, clinical assessment of cardiac output (CO) by the interpretation of indirect parameters such as blood pressure may be misleading. In addition, trend monitoring instead of spot measurements may be more informative (15).
Early recognition of cardiovascular compromise in sick infants enables the physician to take timely therapeutic decisions and monitor response to treatment more objectively (16).
Functional echocardiography can provide real time hemodynamic information by assessing cardiac function, loading conditions (preload and afterload) and CO. It is non-invasive, portable and can give real time analysis of physiological information, which in conjunction with clinical assessment, can help in guiding targeted specific therapy (17), but is technically demanding and can only be obtained intermittently (4)
Electrical cardiometry (EC) has been proposed as a safe, accurate and reproducible technique for hemodynamic measurement in children and infants (4). It is FDA approved and validated for use in neonates (18).
In this study, our aims were to assess the hemodynamic status and cardiac performance in healthy preterm neonates (control group) and in the sepsis group by electrical cardiometry in comparison to echocardiography.
It was conducted on all septic preterm neonates with gestational ages between (34 0/7 to 36 6/7) weeks who were admitted to the NICU and meeting the criteria for diagnosis of neonatal sepsis according to Haque, 2005 (7).
Studied populations included cases with sepsis (40 cases) according to criteria for diagnosis of neonatal sepsis. Healthy preterm neonates matched with the sepsis group in the gestational and the post-natal ages were enrolled to the study as a control group.
Hemodynamic status was assessed using electrical cardiometry in comparison to echocardiography at 1st, 2nd, 3rd days of the starting of sepsis manifestations and before discharge (last reading) for both studied groups.
As regard mean values of SV, CO and CI were significantly higher at 2nd readings compared to last readings in sepsis group in comparison to control group (P value < 0.001) recorded by both Echocardiography and Electrical cardiometry.
These findings can be explained by the anatomical structure of the premature heart that differs from adults. Structurally, the immature heart has lower mass, fewer and less organized myofibrils, fewer mitochondria, fewer L-type calcium channels, and shallower T-tubules, resulting in decreased ability to facilitate the release of calcium from sarcoplasmic, higher overall collagen content as well as a higher ratio of collagen rigidity-increasing type I to elasticity-increasing type, and less adrenergic innervation and adrenoreceptor density (19).
Functionally, these anatomic differences translate to lower functional reserve in response to altered loading conditions and stresses (20) lower diastolic performance, less ability to increase stroke volume in response to increases in preload, and a greater tendency for systolic dysfunction and lower stroke volume in face of acute increases in afterload (13).
These findings came in agreement with previous studies using functional echocardiography (21); (14); (22).
Index of contractility (ICON) was measured at 1st, 2nd, 3rd days of sepsis manifestations and last reading (before discharge). Comparison between cases and control was done at 2nd readings; in sepsis group there was no significant difference in ICON at 2nd readings in comparison to last readings and in comparison, to controls.
There is paucity of data about this item and to the best of our knowledge no previous research studied this item in neonates or pediatrics with sepsis.
One of current study aims was to compare EC to echocardiography in the measurement of SV, CO and CI in each one of the four readings of the same patient. So, tests of correlation were done to compare between both devices.
The Pearson coefficient test was used to evaluate the correlation between the EC measurements and the echocardiogram measurements. SV 2nd, CO 2nd, and CI 2nd measurements in EC showed significant positive correlation with echocardiography among sepsis group and control group.
This agreed with a prospective observational study by Song et al. (2014) on 40 preterm neonates who underwent 108-paired EC and ECHO measurements, they found there were positive correlations between EC-CO and left ventricular output b echo by Pearson coefficient with p value < 0.005 (statistically significant).
Bland–Altman plots were made to evaluate the agreement of SV, CO, CI at 2nd readings by echo an (23)d EC. Bias was defined as the mean difference between the EC and echo measurements.
In sepsis group, the mean bias of SV 2nd reading was 0.02 ± 0.098 (limits of agreement-0.17:0.21). The mean bias of CO 2nd reading was 0.000 ± 0.004 with (limit of agreement of -0.008: 0.008). The mean bias of CI 2nd reading was 0.000 ± 0.024 with (limit of agreement of -0.048:0.047).
In control group: The mean bias of SV 2nd reading was − 0.019 ± 0.018 with (limit of agreement of -0.054: 0.017). The mean bias of CO 2nd reading was − 0.002 ± 0.006 with (limit of agreement of -0.014: 0.010). The mean bias of CI 2nd reading was − 0.00 ± 0.058 with (limit of agreement of -0.12:0.11).
Hsu et al. (2016) found that EC and Echo have a wide but clinically acceptable agreement in measuring CO in preterm infants by Bland-Altman plot. Also, Song et al. (2014) reported that, in the preterm infant, EC correlates with LVO by echo, with limitations of detection at low output and with high-frequency ventilation using Bland-Altman plot.
On the opposite side Sanders et al. (2020) conducted a systematic review and meta-analysis study to assess the accuracy and precision of cardiac output measurement by electrical cardiometry compared to a reference method (thermodilution (TD) and transthoracic echocardiography (TTE)) in adults (included 13 studies), paediatrics (9 studies) and neonates (2 studies). This systematic review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) approach, they concluded that EC cannot replace TD and TTE for the measurement of absolute CO values, but they reported that EC might still be applicable as a trend monitor to measure acute changes in CO, which is relevant for clinical decision-making.
Limitations of the study:
This was a single-center study with limited number of patients, Small sized study; larger samples are needed to confirm our results, short duration of the study., Unblinded design as it was not possible to conduct it in a blinded manner for comparing electrical cardiometry and echocardiography in the same NICU, we didn’t use any invasive hemodynamic measurements techniques for assessment of some parameters e.g., blood pressure.