Spinal anesthesia

Spinal anesthesia injects medication into cerebrospinal fluid in the lower back to temporarily block sensation and movement below the injection site.

Subarachnoid space: The space between the arachnoid and pia mater that contains cerebrospinal fluid and spinal nerve roots. Spinal medication is deposited in this cerebrospinal-fluid-filled space.
Meninges: The three membranes—dura mater, arachnoid mater, and pia mater—that surround the brain and spinal cord. The needle crosses the spinal meninges before medication enters cerebrospinal fluid.
Cesarean section: Surgical delivery of a baby through incisions in the abdomen and uterus. Spinal anesthesia is commonly used to provide surgical anesthesia for planned and urgent cesarean delivery.
Hypotension: Blood pressure that is abnormally low for a person or clinical situation. Sympathetic blockade can dilate blood vessels and cause an abrupt blood-pressure decrease.
Local anesthetic: A drug that temporarily blocks voltage-gated sodium channels in nerves, preventing electrical signals from propagating. These drugs interrupt sensory and motor signals after entering cerebrospinal fluid.
Cerebrospinal fluid: A clear fluid that circulates around the brain and spinal cord, cushioning them and supporting chemical exchange. It carries injected medication through the space surrounding spinal nerve roots.
Transurethral resection of the prostate: An endoscopic operation that removes obstructing prostate tissue through the urethra. A spinal block can provide anesthesia while allowing clinical recognition of some symptoms of fluid absorption.
High spinal block: An unexpectedly extensive spinal anesthetic block that can impair breathing and cardiovascular function. Excessive upward spread can affect nerves needed for breathing and circulation.
Dermatome: An area of skin whose sensation is supplied mainly by one spinal nerve root. Testing dermatomes shows how far the sensory block has risen.
Spinal nerve: A nerve formed by the union of a dorsal sensory root and a ventral motor root. Medication in cerebrospinal fluid acts on spinal nerve roots to block sensation and movement.

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