Isoflurane-induced Neuroinflammation in Children With Hydrocephalus

Background \& Significance. Each year, millions of children receive general anesthesia. Isoflurane, a GABA type A (GABAA) receptor agonist is an inhaled anesthetic commonly used in clinical anesthesia practice worldwide. Anesthetics traditionally have been assumed to be safe as long as severe hypotension and hypoxia are avoided. Interfering with the balance of excitatory and inhibitory neurotransmitters in the developing brain may interfere with the formation of synaptic connections and enhance the normal apoptotic processes that lead to neuronal pruning and may induce neuroinflammation. Such enhanced neuronal pruning and neuroinflammation could lead to excessive neuronal loss at critical times during brain development and consequently cause later learning disabilities. Recent reports of neurotoxicity induced with isoflurane have triggered significant concern about the safety of this agent.

Investigations into neuroinflammation and apoptosis after anesthetic exposure in human children have been limited due to ethical and methodological concerns. Studies that have been done have been largely retrospective, population-based studies. Results from these studies have been mixed, some showing a decline in neurocognitive performance, some showing no change. Further, the vast majority of prospective, hypothesis-driven research has been undertaken in animal models. Developing a clinically relevant animal model and testing resultant hypotheses in humans are critical steps in determining the underlying cause of these changes as well as identifying possible therapeutic targets. The investigators hypothesize that piglets exposed to commonly used anesthetics will exhibit increased neuroinflammation when compared with controls. It is further hypothesized children undergoing neurosurgery with isoflurane anesthesia will show evidence of increased central nervous system inflammation. Finally, the investigators hypothesize that significantly less robust inflammation will be seen in patients undergoing MRI with general anesthesia (no surgery), indicating a role of surgical stress in the modulation of isoflurane-induced neuroinflammation.

Clinical/Translational Investigation (NCH): Surgery Group. Patients aged 0-5 years undergoing general anesthesia for ventriculoperitoneal shunt (VPS) repair will have CSF and serum sampled at the beginning of surgery (after induction but before surgical incision) and at the end of surgery (after closure but before emergence). Each of these patients will be randomized to a standardized anesthetic. An additional CSF sample will be taken prior to post anesthesia care unit (PACU) discharge. These samples will be analyzed as described above. Control Group. Patients undergoing diagnostic MRI under general anesthesia for non-neurologic pathology will receive a standardized anesthetic. Serum will be collected at the beginning and end of the procedure and will be analyzed for inflammation as above.

Short term goals: Demonstrate that isoflurane has a role in modulation of neuroinflammation in humans. Determine if surgical stress also has a role in modulation of this inflammation. Develop a clinically relevant animal model for hypothesis-driven anesthetic neuroinflammation research.

Long term goals: Identify which anesthetic regimens, if any, are safe for use in the developing brain. Identify therapeutic targets for prevention or treatment of anesthetic-induced neuroinflammation. Obtain independent federal funding for future research and establish an experimental neuroscience program on the Nationwide Children's campus.