Children's brains are more affected by an inhaled anesthetic than an intravenous anesthetic with increased levels of brain lactate, according to a new study conducted by researchers at Stony Brook University School of Medicine (Anesthesiology, November 2012, Vol. 117:5, pp. 1062-1071).
Lactate increases brain activation and may lead to metabolic changes associated with anxiety and delirium. The findings provide new clues to metabolic changes within the brains of children undergoing anesthesia and could help researchers understand why general anesthesia may be potentially harmful to the developing brain, the researchers noted.
For the study, 59 children ages 2 to 7 were administered one of two routinely used anesthetics for an MRI procedure: sevoflurane (inhaled) and propofol (intravenous). The parietal cortex of the children's brains was imaged one hour after being administered anesthesia. The children involved in the study did not differ in age, weight, or gender between the two groups. Children with acute brain trauma and other conditions that increased intracranial pressure were excluded from the study. All were anesthetized for MRI procedures only, and therefore postsurgical pain did not contribute to the mental or emotional status of patients.
The team, led by Zvi Jacob, MD, and Helene Benveniste, MD, PhD, mapped the metabolic patterns of the children's brains by using proton MR spectroscopy, an imaging method that tracks metabolic processes and defines chemical fingerprints that cellular processes leave behind. The imaging revealed that approximately twice the amount of lactate and 20% more glucose were present in the parietal cortex of sevoflurane-anesthetized children compared with propofol-anesthetized children.
"Lactate increases when the brain is activated, and therefore the higher level of lactate in the brain of a child administered sevoflurane compared to propofol is likely the result, in part, of more neuronal firing during the unconscious state, which means more activity in the brain," said Dr. Benveniste, professor of anesthesiology and radiology and vice chair for research in the department of anesthesiology. "This activity resulting in lactate 'flooding' in the setting of anesthesia may be disadvantageous and increase the chance of children becoming anxious and/or delirious during emergence from anesthesia or in the immediate postoperative period."
Children who emerged from anesthesia with more agitation and dissociative behavior also had the highest levels of brain lactate, she and her colleagues noted. Additionally, the children who emerged with more agitation and cognitive disassociation -- regardless of the anesthetic form used -- had higher lactate and glucose concentrations but lower concentrations of creatine in the brain. All children recovered without complications from the anesthesia. The recovery time was shorter with propofol compared with sevoflurane.
"It is important to point out that the results do not suggest that either of the anesthetics cause long-term effects," Dr. Benveniste emphasized.
