Methods
Observational study with a convenience sample, approved by the ethics
committee of the Hospital de Clínicas de Porto Alegre (CAE
20309619.0.0000.5327), with informed consent obtained from the
participants. Patients admitted to the Pediatric Intensive Care Unit
between May 2019 and June 2022 were included, while those who were
unstable from a respiratory or hemodynamic point of view, in whom
ventilatory and/or echocardiographic measurements were not possible, and
those with pre-existing cardiopathy with hemodynamic repercussions were
excluded. It was calculated that 128 patients would be necessary to
obtain a frequency of 25% of RV dysfunction, with a confidence level of
95%.
Echocardiograms were performed by experienced pediatric cardiologists in
the pediatric ICU using a Cx 50 - Philips device, with the following
windows used: apical 4-chamber, apical 5-chamber, longitudinal
parasternal, short-axis parasternal, and subcostal.
The reference values used to define alterations in the echocardiographic
parameters were as follows: for tissue Doppler S’ wave, values
< 10 cm/s were considered abnormal (6); for the right
ventricle to left ventricle (RV/LV) ratio, values below 1 were
considered abnormal (7). As for the tricuspid annular plane systolic
excursion (TAPSE), the criteria provided by Koestenberger et al. were
used, and values <-2 standard deviations (SD) for each age
were considered as altered (8).
Cardiac index (CI) was calculated from echocardiographic measurements of
the integral left ventricular outflow tract velocity-time integral (VTI)
and the cross-sectional area (CSA) of the VTI, using an electronic
calculator accessible through the linkhttps://www.omnicalculator.com/health/doppler-echo-cardiac-output.
All respiratory measurements were performed using the Servo i ventilator
resources. To evaluate pulmonary mechanics, the ventilator was set to
volume control, and an inspiratory pause was performed, registering the
following variables: peak pressure (Ppip), plateau pressure (Pplat),
dynamic compliance (Cdyn), static compliance (Cstat), and inspiratory
resistance (Rinsp). During the expiratory pause, autoPEEP and expiratory
resistance (Rexp). The driving pressure (DP) was calculated as DP =
Pplat - total PEEP. The saturation index (SI) was estimated for all
patients using the formula SI = 100 x MAP x FiO2 / SatO2.
The calculation of the VIS was performed as proposed by Gaies and
colleagues in 2010, by summing the doses of different vasoactive
medications using the following formula: VIS = Dopamine dose (μg/kg/min)
+ Dobutamine dose (μg/kg/min) + [10 x Milrinone dose (μg/kg/min)] +
[100 x Adrenaline dose (μg/kg/min)] + [100 x Noradrenaline dose
(μg/kg/min)] + [10,000 x Vasopressin dose (U/kg/min)].
Quantitative variables were described using mean and standard deviation
or median and interquartile range. Categorical variables were described
using absolute and relative frequencies. To compare means, the t-student
test or Analysis of Variance complemented by Tukey were applied. In
cases of asymmetry, the Mann-Whitney or Kruskal-Wallis tests
complemented by Dunn were used. To assess the association between
categorical variables, either Pearson’s chi-square test or Fisher’s
exact test was applied.. Pearson’s or Spearman’s correlation were used
to evaluate the association between numerical variables.
The significance level was set at 5% (p < 0.050), and the
analyses were performed using SPSS version 27.0 program.
Results
A total of 155 patients were included, and 9 were excluded due to
cardiac conditions, resulting in 146 patients. The main demographic and
clinical characteristics of the patients are presented in Table 1. The
median age was 7 months, with 64.4% (94) being infants, and 51.4% (75)
female. Of the patients studied, 66.4% (97) were classified as having
complex chronic diseases, and the main reasons for hospitalization were
bronchiolitis, pneumonia, and sepsis.
Regarding the evaluation of the right ventricle through isolated
echocardiographic parameters, it was observed that 24% (35) had TAPSE
alterations, 14% (20) had altered S’ wave, and 10.7% (15) had a RV/LV
ratio below 1. By grouping all patients who had any of these
alterations, it was found that 38.5% (55) of them presented right
ventricle dysfunction.
The majority of children with RV dysfunction were infants (60% - 33
patients). The median age in the group with altered TAPSE was 36 months,
compared to 5 months in those with normal TAPSE (p < 0.05).
In 38% (56) of the patients, it was possible to obtain measurements of
pulmonary mechanics, which were assessed as part of the routine care
when requested by the medical team.The echocardiographic parameters of
this patient population were analyzed, and no significant differences
were found between the groups classified as with or without RV
dysfunction (Table 4).
It was observed that PSAP was altered in 44% of clinically shocked
patients compared to 22% of non-shocked patients (p 0.012).
Patients with RV dysfunction had a higher median lactate level (1.74 vs.
1.3; p = 0.015) and a higher VIS score (7.5 vs. 3; p = 0.048), but
without statistically significant differences in mortality.
Echocardiographic parameters were compared among groups of patients with
obstructive lung disease, compliance issues, or without lung disease.
TAPSE had higher averages in patients with compliance issues, with p
< 0.001 (Table 2).
Correlations between echocardiographic parameters of the RV and
pulmonary ventilation parameters were identified, showing a weak
positive correlation of peak pressure with the RV/LV ratio (0.305).
TAPSE showed a moderate negative correlation with resistance and
autoPEEP measurements. S’ wave showed a negative correlation with
resistance (Table 3).
The mean cardiac index (CI) found was 3.8 ± 1.43, with 15% of the
evaluated patients having CI values below 2.5 L/min/m². The frequency of
RV dysfunction was higher in patients with altered CI (65% compared to
36% of patients with classified as normal CI - p0.029). Patients with
altered cardiac index had a mean TAPSE of 1.26 ± 0.49, with 50% having
values below -2SD for age (p 0.014). The S’ wave was also more altered
in the group with CI below 2.5 L/min/m², representing 40% of the total,
with p 0.002.
When evaluating ventilatory and pulmonary mechanical parameters between
groups with or without altered cardiac output, no significant
differences were observed (Table 4).
There was a weak positive correlation between TAPSE, S’ wave, and
autoPEEP with cardiac index (0.171 [p 0.048]; 0.221 [p 0.001];
and 0.289 [p 0.044], respectively) (Table 3).