Skip Navigation LinksHome > October 2008 - Volume 21 - Issue 5 > Understanding anesthesia through functional imaging
Current Opinion in Anaesthesiology:
doi: 10.1097/ACO.0b013e32830edbf3
Neuroanesthesia: Edited by Arthur Lam

Understanding anesthesia through functional imaging

Ramani, Ramachandran; Wardhan, Richa

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Abstract

Purpose of review: This review will highlight the recent functional magnetic resonance imaging, positron emission tomogram scan and connectivity studies in anesthesia and analgesia.

Recent findings: In regional cerebral blood flow (rCBF) studies with isoflurane and sevoflurane, there is a consistent pattern of rise in rCBF in the anterior cingulate cortex and insula while the thalamus, lingual cortex and cerebellum show a decrease in rCBF, in a dose range of 0.2–1 minimum alveolar concentration. Even 0.25 minimum alveolar concentration causes a predominant decrease of rCBF in the cortical regions and increase of rCBF in the subcortical regions. This minimum alveolar concentration level primarily affects the association cortices. Thalamus and thalamo-cortical pathways seem to be linked to the hypnotic effects of anesthesia and deep sedation. Connectivity studies also confirm this. The electroencephalogram equivalent of this appears to be a transition from ‘α’ wave activity to ‘δ’ wave activity. Anterior cingulate cortex, S1 and S2 are the regions consistently activated in acute pain. Remifentanil infusion in acute pain decreases the activation in pain perception regions while activating the pain modulation regions. In chronic pain states, prefrontal cortex and insula are activated whereas there is a decrease in activity in the thalamus.

Summary: Slowly, a pattern of neuronal activity reflecting hypnosis, analgesia, amnesia and reflex suppression seems to be emerging giving us a better insight into the central nervous system effects of anesthesia.

© 2008 Lippincott Williams & Wilkins, Inc.

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