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Introduction

The field of pediatric neurosurgery has made significant advances throughout the past several years, requiring a heightened awareness to neurosurgical technique and treatment management, all affecting pediatric neuroanesthesia practice. This review will focus on the implications of evolving technology and surgical approaches to pediatric neurosurgical lesions. An overview of recent advances in data-based studies on postoperative outcome, developmental cerebral circulation, blood sparing techniques, regional anesthesia and postoperative disposition will roundup this update on pediatric neuroanesthesia.

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Developmental cerebrovascular physiology

Since cerebral perfusion is dependent on blood pressure, much debate has ensued over the appropriate blood pressure ranges in infants and children undergoing general anesthesia. While normative blood pressure values differ in age [ , ], the hemodynamic impact of general anesthesia and surgical procedures on cerebral perfusion and central nervous system integrity is unknown. Without appropriate targets, inadequate cerebral perfusion can lead to significant postoperative neurological morbidity [ ]. Although it is known that cerebral blood flow (CBF) increases from age 7 months and peaks at 6 years, the lower limits of cerebral autoregulation in children and especially neonates are unclear [ ].

Cerebral autoregulation appears to be intact at birth in healthy patients [ ] and studied extensively in altered cerebrovascular conditions inherent in cardiac surgery [ ] and traumatic brain injury [ ]. However, these reports utilized invasive monitors that are not practical for routine anesthesia management and highlight the need for noninvasive modalities that are adaptable to the surgical suite. These include near-infrared spectroscopy (NIRS) technology [ , ], and electroencephalogram (EEG) algorithms. However, a recent multicenter study of standard NIRS to detect low cerebral saturation as a surrogate of cerebral perfusion was inconclusive in heralding subsequent neurocognitive deficits [ ]. Ongoing work in functional NIRS with diffuse correlation spectroscopy has the potential to monitor cerebral hemodynamics in pediatric patients with neurosurgical lesions [ ]. Furthermore, reports on intraoperative EEG provide some evidence that isoelectric patterns may be associated with hypotension, which may be a harbinger of cerebral ischemia [ ]. Additional investigations are underway to determine the suitability of these non-invasive monitors in the routine intraoperative management of pediatric patients [ ].

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Outcomes

American College of Surgeons National Surgical Quality Improvement Program-Pediatrics (NSQIP-Peds) provides risk-adjusted, comparative data regarding postoperative outcomes in a variety of pediatric surgery subspecialties [ ]. An analysis of the pediatric neurosurgical data set revealed relatively low mortality but high morbidity in pediatric neurosurgical patients [ ]. Subsequent interrogations of this large database will provide additional guidance for perioperative quality and process improvement initiatives in care of infants and children.

Neonates and infants are at highest risk than any other age group for morbidity and mortality during the perioperative period due to respiratory and cardiac-related events [ , ]. Pediatric neurosurgical patients have increased incidence of mortality and lower academic achievement in adolescence [ ]. A prospective review of 30-day morbidity and mortality in pediatric neurosurgical patients identified three predictive indicators, significant adverse event, unplanned reoperation and surgical site infection [ ]. An organ systems-based evaluation must be performed to rule-out congenital anomalies or co-existing pathology that may impact the conduct of anesthesia and outcome. The ongoing risk stratification of various pediatric surgical procedures should guide the allocation of perioperative resources and planning for these vulnerable patients.

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Minimally invasive pediatric neurosurgery techniques

Recent innovations in endoscopic and stereotactic techniques have increased the role of minimally invasive surgery in pediatric neurosurgery [ ]. These evolving techniques relinquish the need for open craniotomies leading to reduced intraoperative blood loss, surgical site infections, and postoperative pain, while maintaining favorable surgical outcomes. Despite these advances, pediatric anesthesiologists must be prepared for distinct nuances between endoscopic and open craniotomy approaches, including the potential for unrecognized blood loss and development of acute intracranial hypertension leading to Cushing’s triad [ ].

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Interventional magnetic resonance imaging

The routine use of intraoperative MRI (iMRI) has been adopted by major pediatric neurosurgical centers and allows neurosurgeons to better localize, guide the extent of resection and optimize gross total resection of the lesion/tumor [ ]. However, challenges inherent in iMRI suites include high powered magnet and MRI compatible anesthesia machines, monitors and infusion pumps. Furthermore, the fixed operating table places the patient’s head at 180° from the anesthesia equipment, leading to limited patient access and exceptionally long ventilator circuit and infusion tubing [ ]. The cool ambient temperature of the iMRI suite can lead to hypothermia, which can lead to vasoconstriction and difficulty in secure vascular access and can be prevented with focused quality improvement initiatives [ ]. Additional hazards in iMRI include radiofrequency induced burns, projectile injury, and occupational noise exposure. Finally, the MRI introduces equipment and monitoring issues. ECG monitoring is particularly challenging as electrical interference creates difficulty with arrhythmia and ST segment analysis, and the short wires on ECG necessary to minimize the risk of burns necessitate suboptimal lead placement [ , ].

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Functional pediatric neurosurgery

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Interventional neuroradiology

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Blood sparing techniques

There is still potential for significant blood loss with both minimally invasive and open craniotomy procedures. Although induced hypotension and acute normovolemic hemodilution has been proposed as adjuvants for blood sparing protocol, both places the patients at risk for hypovolemia resulting in hemodynamic instability and compromised end-organ perfusion.

Instead, the use of antifibrinolytics, specifically tranexamic acid and epsilon-aminocaproic acid, has emerged as a viable option as a lower risk blood sparing technique. Tranexamic acid is a synthetic derivative of lysine that blocks the lysine binding sites of plasminogen molecules, inhibiting the interaction of plasminogen with plasmin and fibrin. Clinical studies have demonstrated its effectiveness in reducing blood loss during surgery and anesthesia [ ], with single center studies demonstrating decreased blood loss and blood transfusions [ ].

The pediatric craniofacial collaborative group, a large consortium of multiple institutions that perform craniofacial surgery, has demonstrated effective use of antifibrinolytics in reducing the need for blood transfusion as well as a minimal complication rate, specifically with seizures and other perioperative events [ ].

Tranexamic acid has been associated with thrombotic events [ ] and postoperative seizures [ ]. While rare, these can potentially occur and should be examined in the context of the patients’ coexisting medical conditions and surgical procedure. One should weigh the risk and benefits of any drug in practice, and there seems to be more data supporting the use of antifibrinolytics in this surgical population.

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Regional techniques in pediatric neuroanesthesia

There is a historical belief that neurosurgical procedures, particularly in children, are not painful. Recent studies have demonstrated that moderate to severe pain is much more common than previously thought [ ]. While the administration of opioids can be effective in treating pain, the side effects of sedation and respiratory depression side effect may be particularly detrimental in the neurosurgical patient population. Poorly controlled pain can result in agitation and hyperventilation in children, which can result in postoperative morbidity. Non-steroidal anti-inflammatory drugs (NSAIDs) can be utilized, although likely not in the immediate postoperative period with the concern for potential bleeding. Acetaminophen can be given in various forms (intravenous, oral, rectally), and can be helpful, although it may provide inadequate pain relief.

Regional techniques have demonstrated some potential to help with pain control in neurosurgical procedures. There continues to be evidence supporting its use in many adult surgical populations. However, there is limited data in pediatric neurosurgery. Several case reports demonstrated their potential use in unique situations, such as ventriculoperitoneal shunt placement [ , ], and awake craniotomies [ ]. Recent studies have demonstrated improved quality of postoperative pain in children for posterior cranial surgery [ , ]. Given the distribution of superficial nerves in posterior cranial surgery, these are considered more painful procedures for children. Pediatric anesthesiologists should consider the use of nerve blocks in this specific patient population, as an adjunct to help with pain control and minimize the use of opioids.

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Postoperative disposition

Postoperative monitoring is very important for pediatric neurosurgical procedures. There is no consistent standard on the appropriate location for these procedures. Some instituions routinely send their postoperative pediatric craniotomies and craniofacial surgery to the pediatric intensive care unit, while others routinely send these patients to the ward. This is institution dependent. What is most important is that the postoperative location is able to provide adequate monitoring in order to detect and rapidly treat postoperative complications.

After intracranial surgery, it is important for patients to have serial postoperative neurological examinations performed at frequent intervals. Therefore, tracheal extubation should be expedited. A recent NSQIP-Peds examined factors that increased the odds of unplanned post-craniotomy re-intubation. These include, age ≤12 months, operative time ≥200 min, American Society of Anesthesiologist’s physical status score ≥3, emergent case status, malignancy or neuromuscular disorder, and posterior fossa surgery [ ]. These risk factors should provide guidance on the need for postoperative monitoring in an intensive care setting.

After craniofacial surgery in young children, the postoperative monitoring should not only focus on neurological examinations, but on hemodynamic parameters. Given the recognized and unrecognized blood loss in children with minimal reserve, postoperative volume status must be monitored as well as hemoglobin values to ensure adequate volume resuscitation in these patients. Some institutions send non-syndromic craniosynostosis patients to the ward while monitoring syndromic patients in their intensive care units. In a large series of non-syndromic undergoing craniosynostosis surgery, none required transfer to the intensive care unit [ ].

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Practice points

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  When caring for young children and infants, anesthesiology providers must be cognizant of maintaining cerebral perfusion, particularly when intact cerebral autoregulation mechanisms may be disrupted.

  
  
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  Given the recently developed minimally invasive techniques in pediatric neurosurgery practice, pediatric anesthesiology providers should be prepared for complications from a closed cranial vault, particularly acute intracranial hypertension and massive blood loss.

  
  
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  With improved medical imaging technologies, particularly MRI and interventional radiology, proceduralists have been using these modalities for neurosurgical procedures, including MRI guided laser ablations and embolization of intracranial tumors and vascular anomalies. In addition to concerns for a closed cranial vault, pediatric anesthesiologists must be aware of the logistical concerns of being in a medical imaging setting (MRI and ionizing radiation).

  
  
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  Much work has been performed in recent years to decrease blood transfusion administration as that has been associated with worsened outcomes. The use of antifibrinolytics during cases to help minimize blood loss and hence the need for blood transfusion has been adopted.

  
  
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  This fragile patient population requires close postoperative monitoring. Depending on the hospital’s practice parameters, these patients requiring inpatient admission can be monitored on the inpatient ward postoperatively if there are frequent neurological examinations, or the intensive care unit if this monitoring cannot be performed in the ward.

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Research agenda

Future research on targets for blood pressure limits in neonates and children is necessary to determine appropriate clinically relevant values to ensure cerebrovascular physiology.

More outcome data can help determine morbidity, mortality, and long-term outcome in this patient population, particularly with the new minimally invasive techniques. Given the small numbers of these patients compared to other diseases, to obtain appropriate analyses, multi-institutional or database studies would be most helpful in guiding these innovations.

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Conclusion

The field of pediatric neuroanesthesia has to adjust to the changes in pediatric neurosurgery. With significant advances in surgical procedures, particularly minimally invasive technique, pediatric anesthesiologists should be attuned to not only to the potential benefits, but the potential risks. While minimally invasive procedures have demonstrated lower blood loss in patients, there still can be the potential for significant blood loss, particularly because of the large vessels in the brain close to where neurosurgeons are operating.

Anesthesiologists must be vigilant during pediatric neurosurgical procedures, being aware of both the nuances of the surgical procedures, as well as the patient physiology and comorbidities. Knowledge of all of this will help providers give the most optimal care for patients and enhance patient safety and outcome. Further studies are needed to understand how anesthetic care can affect and improve outcomes in this fragile patient population.

CRediT authorship contribution statement

Hubert A. Benzon: Conceptualization, Writing – original draft, Writing – review & editing. Carolyn G. Butler: Conceptualization, Writing – original draft, Writing – review & editing. Sulpicio G. Soriano: Conceptualization, Writing – original draft, Writing – review & editing.