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).