Neuroprotection
Although certain early studies suggested potentially adverse effects
of μ-opioid agonists on ischemic brain, other studies document that at least certain
opioid agents, such as the κ-agonists, can be neuroprotective at least in animal
models of focal ischemia.[112]
[113]
Animal studies of neurologic injury suggest that anesthesia with opioids improves
neurologic outcome compared with the awake state.[114]
It was also shown that activation of δ-opioid receptors increases survival
time of mice during lethal hypoxia.[115]
[116]
In addition, spinal cord protection by fentanyl-N2
O anesthesia is equal
to that provided by halothane or spinal lidocaine.[114]
On the other hand, Charchaflieh et colleagues demonstrated, using the rat hippocampal
slice model, that fentanyl is neither neurotoxic nor protective against anoxic injury
to neurons when used in concentrations comparable to those produced in clinical practice.
[117]
In the rat model of focal ischemia, in contrast
to isoflurane, fentanyl neither increased nor decreased brain injury compared with
awake unanesthetized rats.[118]
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