Patient positioning and its impact on perioperative outcomes in children: A narrative review

Patient positioning interacts with a number of body systems and can impact clinically important perioperative outcomes. In this educational review, we present the available evidence on the impact that patient positioning can have in the pediatric perioperative setting. A literature search was conducted using search terms that focused on pediatric perioperative outcomes prioritized by contemporary research in this area. Several key themes were identified: the effects of positioning on respiratory outcomes, cardiovascular outcomes, enteral function, patient and carer‐centered outcomes, and soft issue injuries. We encountered considerable heterogeneity in research in this area. There may be a role for lateral positioning to reduce respiratory adverse outcomes, head elevation for intubation and improved oxygenation, and upright positioning to reduce peri‐procedural anxiety.

they may require specific procedures, such as pneumoperitoneum, to facilitate surgery.6][7][8] When positioning cannot be modified (i.e., when it is a requirement for the surgery itself), an understanding of the effects of positioning allows appropriate action, to mitigate against adverse physiological effects.This understanding can also serve as impetus for discussion with the surgical team regarding balancing surgical requirements with physiological impact on a specific patient.There are also frequent occasions where the anesthesiologist may choose the patient's position, for example during induction, airway management, and during the recovery period.There is considerable variation in practice between anesthesiologists in this regard. 9ile there is a body of evidence describing the effects of positioning and specific perioperative outcomes in adults 5,6,10 this evidence appears to be more limited in the pediatric population.
Observational studies in adults have demonstrated various alterations to perioperative positioning that correlate with the incidence of postoperative hypoxemia, aspiration, and hospital length of stay. 5,6Additionally, positioning is known to impact airway management in adult patients, for example, head-elevated positioning can prolong safe apnea time 11 and improve glottic views and intubation times. 10Further, some intraoperative positions such as prone positioning can increase the risk of ocular, peripheral nerve, and pressure injuries.In this educational review, we sought to examine the current literature focusing on the interplay between perioperative positioning and outcomes in the pediatric population.
Whilst "perioperative outcomes" is a familiar term, there is yet to be a consensus on pediatric-specific outcomes, which presents a challenge for the standardization of quality improvement and research in this area.There is ongoing research by the multinational Pediatric Perioperative Outcomes Group (PPOG) seeking to address this issue. 12In addition, consumer-driven research priorities in pediatric anesthesia are being defined. 4From these sources, respiratory, cardiovascular, enteral and patient-centered outcomes were identified as high priority pediatric perioperative outcomes.We sought to focus on these themes in conducting this review.

| ME THODS
A comprehensive search strategy of the databases PubMed, Ovid Medline, Embase and Google Scholar was employed by two independent researchers (HP, JE) using agreed search terms and their derivatives (Appendix A).Pediatric perioperative outcomes identified from the preliminary published findings by the PPOG formed the basis for the search terms. 12These terms included respiratory and cardiovascular adverse events, enteral outcomes including nausea and vomiting, and patient and carer-centered outcomes including anxiety, pain patient and carer satisfaction, and intraoperative soft issue injuries. 12Results were limited to humans and publications in English with no date limits set.Research studies involving pediatric positioning and any of the pre-defined perioperative outcome measures were considered for inclusion in this review.Abstracts and titles were screened independently, and relevant papers reviewed in detail and grouped thematically for inclusion.

| P OS ITI ONING AND RE S PIR ATORY OUTCOME S
Perioperative respiratory adverse outcomes are of particular interest to the pediatric anesthesiologist, as this remains a leading cause of pediatric anesthetic morbidity and mortality. 13,144][15] This includes episodes of laryngospasm, bronchospasm, hypopnea or apnea, breath holding, hypoxemia, prolonged need for supplemental oxygen, pulmonary aspiration, airway obstruction, severe cough, stridor, or the need for reintubation. 137][18][19][20][21][22][23] However, this review only focuses on the impact of positioning.Table 1 summarizes the key findings of studies investigating the respiratory effects of positioning in children, discussed in more detail below.

| Positional changes in respiratory mechanics and physiology
There is a body of research demonstrating that the semi-sitting and lateral positions increase functional residual capacity in both spontaneously breathing and ventilated neonates and children. 25,31

TA B L E 1 (Continued)
Respiratory patterns in awake, spontaneously breathing neonates may also be affected by positioning, with a 20° head-up tilt shown to increase tidal volume but reduce respiratory rate, with a small net reduction in minute ventilation. 24More recently, infants' diaphragmatic work of breathing and inspiratory pressure was found to be significantly lower in both prone and supine 45° head up positions compared to supine. 30,42e effects of intraoperative positioning on respiratory physiology in children has also been investigated.Head-down ("Trendelenburg") positioning reduces respiratory compliance, tidal volume 35 and significantly reduces functional residual capacity and ventilation homogeneity in children under general anesthesia. 7

| Positioning and lung recruitment
Atelectasis is a common occurrence in anesthetized children, contributing to postoperative hypoxemia. 46Fortunately, atelectatic changes can be reversed with the use of recruitment maneuvers. 7,46,47Recent work by Acosta et al. demonstrated that lateral positioning may facilitate lung recruitment in healthy anesthetized children. 40Repositioning from supine to lateral positions combined with positive end expiratory pressure, resulted in the resolution of ultrasound-evidenced atelectasis. 40This was not demonstrated with positive end expiratory pressure alone. 40Children in the positional recruitment maneuver group demonstrated a small but statistically significant increase in peripheral oxygen saturations, although the mean saturations in both groups were high (above 98%). 40In contrast, lateral positioning appears to have no effect on lung recruitment in non-anesthetized children. 27It may be that a combination of both positive end expiratory pressure and repositioning are required for effective re-recruitment.

| Positioning and oxygenation
There are inconsistent findings relating to positioning and oxygenation.Positioning children head-up by 30° or 45° has not been shown to significantly reduce pre-oxygenation time. 38We found no studies evaluating the effect of positioning on safe apnea time in children.In the intensive care setting however, nursing spontaneously breathing infants in the head-up position increased peripheral oxygen saturations. 30This finding has also been demonstrated in very low birthweight neonates. 26The head elevated position has also been shown to decrease the number of desaturations in spontaneously breathing supine and nasal continuous positive airway pressure-supported preterm infants. 28,33 note, the effects of positive pressure ventilation may negate the effects of vertical tilt on oxygenation.Recently published data from a heterogeneous population of neonates (with regards to ventilatory support and post-conceptual age) did not demonstrate significant differences in mean peripheral oxygen saturation, heart rate, and desaturation time between positions. 43Further, the improved oxygenation in spontaneously breathing neonates at 30° head-up versus head-down position was not seen in those that were mechanically ventilated. 29ere are varying levels of evidence for prone positioning in improving oxygenation in children and neonates.A Cochrane systematic review concluded that there is a low to moderate level of evidence of improved oxygenation in mechanically ventilated neonates when nursed prone. 36A more recent review focusing on older children (aged 4 weeks-16 years) with established acute respiratory distress syndrome concluded that there was low certainty evidence of a benefit of prone positioning on improving oxygenation in this population. 44teral positioning has also been investigated in pediatric acute respiratory distress syndrome.Review of the existing studies concluded that lateral positioning does not confer benefit in oxygenation in this patient group. 44portantly, much of the research in this area has been conducted in the neonatal and pediatric intensive care setting, with significant differences in patient comorbidities, ventilatory support, level of sedation, and other interventions, all of which impact the interpretation of this research in the perioperative context.
Furthermore, there is inherent heterogeneity within the pediatric surgical population, from premature neonates to adult-sized teenagers, and it follows that the physiological effects of positioning amongst this diverse patient populations will be varied.

| Positioning and airway management
Lateral positioning influences airway patency in children under sedation and general anesthesia. 32,48Magnetic resonance imaging demonstrates that the non-cartilaginous cross-sectional area of the upper airway is greater in the lateral position compared with supine in sedated, spontaneously breathing children. 32This has implications in clinical practice for reducing the incidence of upper airway obstruction.
Positioning is an important consideration for tracheal intubation.
Positioning children aged 3-7 years head elevated to bring the sternal notch and external auditory meatus into alignment increases the percentage of glottic opening viewed using video laryngoscopy. 37sitioning in this manner can reduce the need for optimization maneuvers, and reduce the number of attempts and time to successful intubation. 37veral studies have investigated the optimal position for airway device removal in children.In a single-center randomized study, lateral positioning was associated with fewer respiratory complications during laryngeal mask airway removal, irrespective of the depth of anesthesia at the time. 34Similarly, there is evidence that children extubated in the lateral position have a lower incidence of respiratory complications including stridor, laryngospasm, and airway obstruction, and may better maintain oxygen saturations. 39,41Combining lateral positioning with elevation of the head may further reduce some PRAE, as demonstrated in children undergoing tonsillectomy for obstructive sleep apnea. 45These potential benefits of lateral positioning at the time of airway removal should be weighed against the challenge of airway management in this position as compared to supine.

| Cardiovascular changes with positioning
As with respiratory physiology, several cardiovascular effects occur with changes in body position.Research in this area has again largely been conducted in the adult population.The 45° sitting, head-up tilt ("reverse Trendelenburg") and prone positions are associated with a reduction in perfusion indices in healthy, non-anesthetized adults, as compared to the supine position. 49rfusion indices are increased by positioning head-down or with leg elevation. 49In the anesthetized patient, intraoperative positioning with head elevation, such as the "beach-chair" position for shoulder surgery, combined with the attenuation of vascular auto regulatory reflexes by general anesthesia, has the potential to reduce cerebral perfusion. 50Pneumoperitoneum during laparoscopic surgery can reduce cardiac output, stroke volume, and ejection fraction. 51trapolating adult data to the pediatric surgical population should be done with caution.The available literature in the pediatric population is more limited, with key findings summarized in breached the lower limits of normal or caused significant effects on blood pressure. 26Two subsequent studies on preterm neonates were unable to demonstrate a clinically significant change in the incidence of bradycardic episodes when the neonates were nursed in the head elevated position. 28,33Beşiktaş and Efe reported no positional difference in heart rate in preterm neonates receiving respiratory support. 54In older, healthy anesthetized children, a 20° head-down tilt did demonstrate a reduction in heart rate but had no effect on cardiac output. 52

| Adverse cardiovascular events
Overall, perioperative adverse cardiac events are uncommon in the pediatric population. 1 Cardiovascular instability was reported in 1.9% of episodes of pediatric anesthesia, with an immediate poor outcome in 5.4%. 1 There are some pediatric subgroups at increased risk including neonates, and those undergoing cardiac surgery and cardiac catheterization. 1 Given the relative rarity and varied etiology of these incidents, as well as the known interplay between cardiovascular and respiratory adverse events (notably bradycardia as a consequence of hypoxemia), a contributory role of perioperative positioning is difficult to demonstrate, though this may be an area for further research.
Venous air embolism has been studied in the pediatric neurosurgical population.In a retrospective observational study, one center reported a venous air embolism incidence of 9.3% in neurosurgical cases performed in the seated position. 55Of these, a fifth were associated with hypotension, however, there were no lasting adverse outcomes.

| Positioning and enteral outcomes
Return to normal enteral function, and the absence of postoperative nausea and vomiting are important postoperative outcomes in neonates and children. 12Table 3 summarizes findings from the publications on positioning and enteral outcomes.

| Positioning, reflux and aspiration of gastric contents
Micro-aspiration of gastric contents is a phenomenon associated with numerous adverse effects including neonatal apneas, 60 poor feeding and pulmonary sequelae such as ventilator acquired pneumonia, 61 aspiration pneumonitis and chronic lung disease. 60,62In adults, acute aspiration events in the context of both anesthesia and critical illness can be fatal. 63While pulmonary aspiration under anesthesia is rare in children, with no fatalities in recent reports, 63,64 significant morbidity, albeit infrequently, can occur. 64There is a plausible interaction between the effects of patient position, gravity, gastroesophageal reflux, and the rate of gastric emptying.There has therefore been interest in determining the optimal position to reduce both reflux and the aspiration of gastric contents.

| Positioning effects on aspiration in ventilated patients
In adults in the intensive care unit setting, positioning with the head elevated (30°-45°) reduces micro-aspiration of gastric contents and increases gastric emptying rates. 65,66This has been as an explanation for the observed reduction in incidence of ventilator associated pneumonia in the head-elevated position. 67Although head elevation is also recommended in the pediatric population to reduce ventilator associated pneumonia, 68 the evidence for positioning effects on micro-aspiration and gastroesophageal reflux in children and neonates are less clear.There is some evidence that in ventilated neonates, the right lateral position may reduce micro aspiration of gastric contents. 58,59Authors attributed this to reduced gastric compression with the stomach in the non-dependent position. 58The relevance of these findings for the fasted, elective surgical neonatal and pediatric population remains undetermined.

| Positioning effects on reflux in non-ventilated patients
In contrast, spontaneously breathing term and preterm infants in neonatal intensive care with established gastroesophageal reflux disease show a reduction in reflux episodes when in the prone and the left lateral positions as compared to the right lateral and supine positions. 8,57Interestingly, Tobin et al. reported that elevation of the bed to 30° had no significant effect on measured reflux parameters in this patient population, 8 and this finding has been replicated elsewhere. 56Although the head elevated position has been associated with increased rates of gastric emptying in a small subset of low birthweight neonates, 26 the causal link between rate of gastric emptying and gastroesophageal reflux disease in children has been questioned. 69

| Positioning and postoperative nausea and vomiting
Another perioperative outcome that may be impacted by patient positioning is nausea and vomiting.In the setting of anesthesia and surgery, changes in position, deceleration, and movement such as that occurring during patient transfer may be precipitants in at-risk patients, for example, those prone to motion sickness or receiving opioid analgesia. 70Intraoperative positioning may also have an impact, with one study reporting a lower incidence of postoperative nausea and vomiting in adult patients managed in the sitting position intraoperatively than those in the supine position. 71We found no studies investigating this interaction in children.

| P OS ITI ONING AND PATIENT-CENTRED OUTCOME S
Patient and family-centered outcomes have been identified as important metrics by which to assess the quality of perioperative care in children.These include, but are not limited to, perioperative anxiety, pain, and patient, and carer satisfaction. 12These outcomes have also been highlighted amongst the top 10 research priorities for consumers in a recent large research priorities-setting project. 4ere is limited and inconclusive evidence that patient positioning during the conduct of anesthesia impacts perioperative anxiety in children.One single-center study found no difference in anxiety scores between the supine and seated upright positions in children undergoing inhalational induction for elective surgery. 72Recovering children in the lateral with head elevated position after adenotonsillectomy resulted in a small reduction in agitation scores compared to the supine lateral position. 45Significantly lower patient distress scores have, however, been demonstrated with intravenous cannula insertion with children sat upright (and held by a parent), compared to lying supine with the carer adjacent to the child. 73Carer satisfaction in this study was also higher when children were positioned upright. 73The potential benefit of upright positioning to reduce periprocedural anxiety has also been demonstrated in children receiving immunizations, where both subjective and objective scores for anxiety and distress were lower in the sitting position. 74Although these studies were not conducted in the perioperative setting, the findings suggest that consideration of patient positioning can benefit children and their caregivers when performing anxiety provoking procedures related to anesthesia, including intravenous cannulation.
We identified no studies that specifically assessed pain related to positioning in children, however, there is a known correlation between a child's anxiety and their perception of pain. 75

| P OS ITI ONING AND SOF T TISSUE INJ U RY
Intraoperative positioning can also contribute to peripheral nerve, ocular and pressure injuries.In addition to risk factors such as duration of surgery, patient age, and intraoperative hemodynamics, intraoperative prone positioning is associated with pressure injuries in children. 76Additionally, there is evidence that intraocular pressure is increased when anesthetized children are placed prone, which may predispose to intraocular injury in prolonged surgeries. 77It is also well established that certain positions increase the risk of peripheral nerve injury such as brachial plexus injury secondary to excessive arm abduction.A modification of the traditional position for the Nuss procedure resulted in a reduction in transient brachial plexus injuries in children and adolescents undergoing this procedure. 78e full range of specific risks associated with certain positions is beyond the scope of this review, but it is important to take meticulous care to protect pressure areas and modify, where possible, positions likely to increase the risk of iatrogenic soft tissue injury.

| SUMMARY
The impact of patient positioning on clinically meaningful perioperative outcomes in children is worth considering in daily clinical practice.There is currently no consensus on optimal patient positioning, tilted or body tilt or sitting semi sitting or head elevation or Trendelenburg or reverse Trendelenburg; • An(a)esthesia or general an(a)esthesia or surgery or perioperative; • Pediatric or children or infants or newborn or babies or neonates; • Respiratory or pulmonary or lung or intubation and complications or adverse effects or events or laryngospasm or-pulmonary aspiration or aspiration or bronchospasm or desaturation or oxygenation or saturation or oxygen saturation; • Cardiac or cardiovascular or h(a)emodynamic and complications or instability or adverse effects or blood pressure or hypotension or hypertension or heart rate or bradycardia or tachycardia or arrhythmia or dysrhythmia or perfusion or hypoperfusion or cardiac output or venous return; • Nausea and vomiting, or nausea or vomiting or emesis or feeding or return to enteral feeding or feed tolerance or oral intake or gastrointestinal or gastric or reflux or gastroesophageal reflux; • Pain or analgesia or discomfort or distress or anxiety or perioperative anxiety or periprocedural anxiety.
• Carer satisfaction or parent satisfaction or parental satisfaction or patient satisfaction; • Intraoperative or iatrogenic and nerve injury or neuropraxia or nerve palsy; • Ocular or eye injury or visual loss; • Pressure injury or pressure area or pressure sore or pressure area.
Above limited to humans and English language.
No date limits set.

1 . 4 .
What is the current practice amongst pediatric anesthesiologists regarding patient positioning during induction, airway management and transfer to the post anesthesia care unit? 2. What are the physiological effects of patient positioning on major body systems? 3. Does lateral positioning during the conduct of anesthesia reduce the incidence of respiratory adverse events in children?Does head up positioning during the conduct of anesthesia reduce the incidence of respiratory adverse events in children? 5. What are the effects of various positions in children on gastric functioning and outcomes?TA B L E 1 Studies on positioning and respiratory physiology and outcomes in children.

Table 2 ,
and discussed below.There is some evidence of altered cardiovas- and the findings inconsistent.In one study of awake preterm low birthweight neonates, a decrease in heart rate was seen with an increase in vertical bed tilt from 0° to 45°, although none of theseTA B L E 2 Studies on cardiovascular effects of positioning in children.Abbreviations: ASA, American Society of Anaesthesiologists; GA, gestational age; HR, heart rate.
Studies on enteral effects of positioning in children.