Introduction
Post-anesthesia delirium is increasingly recognized as an important neurobehavioral complication in children. Importantly, postoperative delirium (POD) should not be confused with emergence delirium usually occurring within the first postoperative hour in the recovery room. Characterized by fluctuating disturbances in attention, awareness, cognition, and behavior, pediatric delirium may present as agitation, inconsolable crying, withdrawal, altered responsiveness, or sleep-wake disturbances.
Unlike delirium in older adults, which often develops in the setting of frailty and cognitive decline, pediatric delirium occurs in the rapidly developing brain, raising concerns about both immediate recovery and longer-term neurodevelopmental consequences.
The introduction of validated assessment tools such as the Cornell Assessment of Pediatric Delirium (CAPD) has improved recognition of this condition (1). However, identifying children at increased risk before surgery remains challenging. Many established risk factors, including young age, developmental delay, severe illness, prolonged ventilation, sedative exposure, and postoperative pain, are difficult to modify or become apparent only after surgery has been completed (2).
As a result, interest has grown in identifying objective and potentially modifiable biomarkers that may improve perioperative risk assessment.
In this context, Li and colleagues report a retrospective study of 320 children aged 3–6 years undergoing laparoscopic surgery under general anesthesia (3). As parents provided consent and preoperative blood samples were collected parts of this study must have been prospective. The authors report that preoperative vitamin D deficiency, defined as a serum 25-hydroxyvitamin D3 concentration below 30 ng/mL, was independently associated with a substantially increased risk of POD in children.
These findings are intriguing because vitamin D deficiency is common in children, easily measurable, and potentially correctable. If confirmed, vitamin D status could represent a practical biomarker of perioperative neurological vulnerability. However, the results also require careful interpretation, particularly given the limitations inherent in observational research.
Delirium and brain vulnerability
Current concepts increasingly view delirium as the clinical manifestation of an imbalance between perioperative stress and the brain’s ability to tolerate that stress. Surgery, anesthesia, inflammation, pain, sleep disruption, and metabolic disturbances all challenge cerebral homeostasis. Whether delirium develops depends not only on the intensity of these insults but also on baseline neurological resilience.
This vulnerability-stress model is well established in geriatric medicine and is equally relevant to children. During early childhood, the brain undergoes rapid maturation involving synaptogenesis, myelination, neurotransmitter remodeling, and immune development (4). Factors influencing neuroinflammatory responses or neuronal resilience may therefore have disproportionate effects on postoperative neurological outcomes.
Vitamin D is an attractive candidate within this framework as its biological role extends far beyond calcium metabolism and bone health. Vitamin D receptors are widely distributed throughout the central nervous system, including regions involved in cognition and behavior (5). Experimental evidence suggests that vitamin D regulates neurotrophic signaling, oxidative stress, mitochondrial function, endothelial integrity, and immune responses (6).
Furthermore, vitamin D appears capable of suppressing pro-inflammatory cytokines while enhancing anti-inflammatory pathways, mechanisms closely linked to contemporary theories of delirium pathophysiology.
The authors’ hypothesis that vitamin D deficiency reduces neurological reserve and increases vulnerability to perioperative neuroinflammation in children recovering from anesthesia is hence biologically plausible.
Important contributions of the study
Vitamin D deficiency has been associated with POD in adults, with only limited pediatric evidence available. The authors provide, therefore, some of the first pediatric clinical data in the perioperative context. The study included a homogeneous population of pre-school children, acknowledged to be at highest risk who underwent laparoscopic procedures under standardized sevoflurane anesthesia using the validated CAPD instrument with repeated postoperative assessments.
Pediatric delirium was assessed by serial evaluations by trained observers to improve detection. In addition, all children had their vitamin D status measured before surgery, supporting its role as a risk marker rather than a consequence of postoperative illness.
Interpreting the effect size
The most striking observation was the reported fourteen-fold increase in delirium risk among vitamin D-deficient children. While such a finding attracts attention, exceptionally large effect sizes in observational studies always warrant scrutiny.
The confidence interval surrounding this estimate was wide, reflecting substantial uncertainty regarding the true magnitude of risk. Although the association appears robust, the exact effect may be considerably different than the point estimate suggests.
Residual confounding remains another important concern. Vitamin D deficiency is closely associated with socioeconomic conditions, nutritional status, physical activity, obesity, chronic illness, sunlight exposure, and other health-related factors. Many of these variables may themselves influence recovery after surgery.
Consequently, vitamin D deficiency may function not only as a biological contributor but also as a marker of broader health characteristics that were incompletely measured.
The reported incidence of delirium, approximately 80%, was also remarkably high suggesting delirium being the expected rather than the ‘abnormal’ response following surgery and anesthesia. Repeated CAPD assessments likely improved case detection, and the young age of participants represents a higher-risk population. However, such event rates are near or above the upper range reported in this population and may affect interpretation of the calculated odds ratios.
Validation in other populations will therefore be essential.
Biomarker, therapeutic target or something else?
The key clinical question is whether vitamin D deficiency is merely a marker of vulnerability, a causal factor that can be modified to improve outcomes or simply an incidental finding. The distinction is important because many biomarkers predict adverse outcomes without directly causing them. Predictive ability alone does not guarantee that correcting the biomarker will improve the measured patient outcomes.
Vitamin D is particularly attractive because supplementation is inexpensive, widely available, and generally safe when appropriately prescribed. This naturally raises the possibility of preoperative correction. However, the present study did not establish that a preoperative supplementation reduces delirium incidence in this population.
Many biologically plausible observational associations have failed to translate into successful interventions when tested in randomized trials. This is the greatest unknown from this study, and the findings should be viewed as hypothesis generating rather than supporting routine vitamin D supplementation specifically for delirium prevention. Randomized clinical trials are required before such recommendations can be made.
While vitamin D concentrations may have limited impact on delirium risk, supplementation may be clinically useful and may also be useful as a marker of socioeconomic status for broader risk stratification models identifying patients who may benefit from enhanced monitoring, routine delirium screening, optimized sleep promotion, family-centered orientation strategies, and careful avoidance of unnecessary sedative exposure.
Perhaps it is time to also consider the ‘whole’ package: socioeconomics, impact of cognitions and intellect, emotional abilities, diurnal variations to name but a few potentially modifiable factors.
Limitations
There are several significant limitations that temper interpretation of these results. The retrospective single-center design leaves the study vulnerable to selection bias, information bias, and residual confounding. Although regression models can adjust for measured variables, they cannot account for factors that were not collected or only measured imperfectly.
Furthermore, postoperative pain is a potential important confounder when interpreting behavioral and delirium-like symptoms in children. Unfortunately, Li et al. did not provide detailed information regarding postoperative pain assessments and analgesic regimens, making it difficult to assess the extent to which pain may have influenced these finding.
In addition, vitamin D demonstrated only modest discriminatory performance as a standalone predictor, with an area under the receiver operating characteristic curve of 0.613. This finding highlights the multifactorial nature of delirium and suggests that vitamin D alone is unlikely to provide sufficient predictive accuracy for routine clinical use. Future studies should determine whether vitamin D adds meaningful predictive value when combined with established clinical risk factors.
Vitamin D concentrations were measured only once before surgery, despite known seasonal and environmental variation. Furthermore, other components of vitamin D biology, including genetic variation in receptors and downstream signaling pathways, were not evaluated. Differences in postoperative pain management may also have influenced delirium risk independently of vitamin D status and remain uncertain.
Clinical implications and future directions
Should practice change today? Probably not. The study demonstrates association rather than causation and does not establish that correcting vitamin D deficiency prevents delirium.
Accordingly, routine supplementation for the sole purpose of delirium prevention cannot currently be recommended based on the reported findings.
Nevertheless, the study highlights an important concept: delirium is influenced by baseline neurological resilience as well as perioperative events. Nutritional status, sleep quality, inflammation, family engagement, psychological preparation, and environmental factors may all contribute to postoperative brain health. Vitamin D may represent one measurable component of this broader network.
The next step is confirmation or rejection of the vitamin D hypothesis in prevention of post-anesthesia delirium. Multicenter prospective studies are needed to determine whether the observed association is reproducible across different surgical populations and healthcare systems. Future work should evaluate vitamin D within multivariable prediction models incorporating clinical, demographic, inflammatory, and perioperative variables.
Given that similar associations have been considered in adults, it would be interesting to explore whether vitamin D status also play a role in POD among adults. Mechanistic studies may clarify whether vitamin D actively modulates neuroinflammatory pathways or simply reflects broader physiological vulnerability. Ultimately, randomized controlled trials will be required to determine whether preoperative vitamin D supplementation reduces the incidence, severity and duration of post-anesthesia delirium in vulnerable children or indeed affects longer-term neurodevelopmental outcomes.
Conclusions
Li and colleagues provide timely evidence linking preoperative vitamin D deficiency with POD in young children undergoing laparoscopic surgery. The findings extend observations from adult populations and support the possibility that vitamin D status represents an important dimension of perioperative neurological vulnerability.
Despite its biological plausibility and potentially important clinical implications, the study should be regarded primarily as hypothesis-generating. The retrospective design, potential for residual confounding, unusually high delirium incidence, and limited predictive performance of vitamin D alone all support a cautious interpretation.
Nevertheless, this work advances the growing view that POD is not simply a consequence of anesthesia or surgery or a combination thereof, but rather the result of interactions among neuroinflammation, physiological reserve, and perioperative stress. Whether vitamin D ultimately proves to be a modifiable contributor remains uncertain. What is already clear is that the study broadens the discussion of perioperative brain health in children and identifies an important avenue for future research.
There is a need for future mechanistic and randomized trials evaluating potentially modifiable risk factors for pediatric delirium.
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