Studies that have evaluated the PICU admission impact on health-related QoL, and cognitive abilities in children without pre-existing or concurrent neurological disorders are scarce [16,17,18]. We observed no statistically significant difference in IQ between patients and controls. Conflicting previous studies report minimal, if any deficits, after PICU admission [10, 11, 13, 14] or a substantial negative impact on QoL, functional outcome, and cognition [17, 21,22,23]. One study reported persistently poor academic performances post-discharge from PICU [
The heterogeneous demographic and clinical characteristics of previous PICU cohorts could have caused this variability. Our cohorts had a mean age of 6.08 years, while it ranged from 1 to 10 years in other studies [1, 11, 13, 14, 16, 17, 22]. In one study, the age range was 2.5–31.6 years [14]. Different age groups with different admission diagnoses underwent different interventions. Thus, finding a unified assessment approach is difficult.
Different assessment tools, including the Multi-Attribute Health Status Classification System [10, 11], Health State Utilities Index [12, 13, 15], generic questionnaires [13], the Paediatric Cerebral Performance Category for cognitive morbidity, the Paediatric Overall Performance Category [22], and various neuropsychological batteries assessing multiple cognitive domains and academic performance, were used across the variable cohorts [16, 17]. This lack of assessment method standardisation makes outcome comparison difficult [9, 16].
School performance or the ability to live independently may not always be appropriate to assess very young children incapable of either [1, 10, 11]. Several current assessment methods have not been validated in infants, who constitute a substantial percentage of PICU admissions.
As in our cohort, a slight male preponderance was observed in most paediatric PICU studies (54–65%) [12, 13, 16, 18, 22]. Our medical patients constituted only 38% of the cohort, and the rest were surgical patients. In one study, surgical patients outnumbered medical patients [10]. In other studies, the opposite was observed [20].
Mechanical ventilation and inotropic support were needed in 38% and 12% of our patients, respectively. The need for both varied widely between studies (30–76% mechanical ventilation [1, 12,13,14] and 27–40.6% inotropic support [1, 13, 14]).
We observed a consistent, non-significant negative correlation between IQ values and the duration of mechanical ventilation, sedation, and inotropic support. Mechanical ventilation and sedation are independent risk factors for cognitive impairment post-PICU discharge [23]. While both have side effects, children requiring more aggressive intervention in the PICU probably had a pre-existing severe illness, and this is probably the more important determinant of functional outcome.
The mean length of PICU stay here was 5.9 ± 2.5 days. The range in similar studies was 4.24–5.7 days [10, 11, 13, 22]. We observed that the mean LOS negatively correlated with IQ values, though insignificantly. In one study, a prolonged paediatric PICU stay had unfavourable outcomes; however, these patients had more comorbidities or disabilities than did the short-stay patients [10]. Neither illness severity at admission nor PICU LOS were risk factors for subsequent cognitive morbidity in a recent meta-analysis [23].
We excluded children with pre-existing neurological diseases that were likely to impact functional outcomes. In most similar studies, 12–66% of patients had pre-existing, common neurological morbidities [1, 11, 14, 22] that were associated with worse long-term outcomes [1, 10].
We excluded children admitted with acute neurological illnesses like meningitis (an independent poor outcome predictor). Admissions for acute neurological illnesses constitute 6–18% of different PICU cohorts [1, 14, 16, 22] with poorer outcomes [10, 11]. Such studies have specified deficits in children with septic illness, including meningococcal disease [16, 17] and patients with pre-morbid conditions [17].
In one study, seizures during admission were also a predictor of worse outcomes. Although seizures could be due to hypoxia or electrolyte disturbance that led to PICU interventions [24], they could also be symptoms of primary neurological illnesses like meningitis or sepsis with central nervous system involvement. In another review, seizures were not a risk factor for cognitive impairment post-PICU admission [23].
PICU-related morbidities tend to resolve over time [9, 13]. Therefore, a problem with previous studies is the lack of standardisation about the time point for the assessment tests [1, 10, 12,13,14,15,16,17]. Tests were carried out at varied time points in one study [14]. One study that concluded a persistent cognitive deficit over time had a high case drop-out rate and included subsets of children with sepsis, meningitis, and chronic illness but did not specify the subsets suffering from persistent neuropsychological deficits. The trend was followed by the group as a whole [18].
More patients are eligible for any study than those who participate [12, 17] and differ in many factors, including the illness severity at admission [7], non-completion of questionnaires due to language barrier [8], and gender and ethnic characteristics [17].
Our study has some limitations: (1) Pre-PICU cognitive assessment data were unavailable; these were also missing in similar studies as cognitive testing is uncommon, especially for previously healthy children. To overcome this, we used healthy age- and gender-matched controls. (2) The small number of patients prevents us from generalising our conclusions. (3) It is important to repeat cognitive testing to assess permanent deficits. (4) Infants, constituting more than half of our PICU patients, were excluded due to the lack of a readily available validated cognition test, and this could have led to the loss of important data.
