Step I subarachnoid inj

[tomtom1287]

hey guys,
can the anesthetics injected into the sub arachnoid space at l4/l5 cross the blood brain barrier?
can it get distributed all around in csf?
thank youinjec

 

[DrPicard]

If you're injecting an anesthetic into the sub-arachnoid space, you're injecting it into the CSF since that's where the CSF is. I think it should get distributed throughout the CSF.

The blood brain barrier shouldn't come into play here since we're not injecting the anesthetic into the blood. The barrier of concern here would be the blood CSF barrier. I'm not sure if anesthetics can cross this barrier and what the consequences of that would be.

 

[cde]

yes - anesthetics cross the blood brain barrier. Spinal anesthesia is usually isobaric - it stays where you put it or hyperbaric - it sinks lower. Occassionally hypobaric spinals are used which the drug rises in CSF column - when the patient is in an inverted position like jack knife. Very small volumes are used 0.3-3cc to limit spread. When the spinal rises to a level higher than desired we call it a high spinal. For example a midthoracic level spinal can cause bradycardia and hypotension. If enough volume is given (for example an epidural that is not longer epidural but intrathecal ) the volume of 20-30cc will anesthetize the brain causing loss of consciousness, seizures along with the bradycardia and hypotension. Hope this helps.