Evidence from experimental animal studies convincingly argues for a role of pro-inflammatory
cytokines due to surgical
trauma in causing
postoperative cognitive dysfunction. However, other studies have shown exposure to 2-4h of
isoflurane anesthetic without surgical
trauma can also impair cognitive function. We aimed to determine
cytokine changes over time following
isoflurane exposure in the presence and absence of surgery and examine subsequent cognitive function. Male rats were exposed to
isoflurane (1.8%, 4h) with or without
laparotomy or control conditions and tested in a contextual fear conditioning paradigm 8 days later. On day 9 rats were perfused, serum and hippocampal samples were collected and 24
cytokines were analysed. Groups of rats exposed as above were killed 6 or 48h after
isoflurane exposure to examine early
cytokine changes.
Isoflurane exposure resulted in significantly less freezing in the contextual fear conditioning test (F(2,31)=6.11, P=0.006) and addition of
laparotomy caused no further deficits (P>0.05). At 6h post
isoflurane exposure an immunosuppressive response was observed in the serum while hippocampal
cytokines were largely unchanged. These finding suggest
isoflurane alone causes inflammatory changes and cognitive deficits. The addition of a
laparotomy had a negligible effect. Early after
isoflurane exposure changes in serum and hippocampal
cytokines were divergent but by 9 days were aligned. At this time
cytokines associated with
memory deficits and
brain injury processes were significantly elevated in serum and brain.