Anesthesia Student Survival Guide.pdf - Index of

196 ● AnesthesiA student survivAl Guide
analgesia. Peripheral nerve blocks may also be used. Individual nerve blocks
can provide surgical anesthesia. It is more practical to perform a lumbar
plexus or three-in-one block (which will cover the femoral, lateral femoral
cutaneous, and obturator nerves with a single injection or catheter). A separate
sciatic block, or a spinal or general anesthetic is then added to complete
the anesthetic.
If you choose epidural analgesia, how will you locate the epidural space? What
precautions will you take to avoid toxicity?
Standard monitors are placed and an IV is inserted. The patient can be seated
or lying on his side; many find the sitting position easier to locate the midline.
The back is sterilely prepped and draped and local anesthetic is infiltrated
in a lumbar interspace, typically L3–L4 or L2–L3. The epidural needle
is advanced until it is seated in ligament. Then a loss-of-resistance syringe is
attached, containing either air or saline. The epidural needle is advanced in
slow increments, checking for resistance to injection, indicating the tip is still
in ligament. When the needle enters the epidural space, a loss of resistance to
injection will be felt. The epidural catheter is then inserted 3–5 cm and the
needle withdrawn. To avoid toxicity, it is important to exclude intravascular
or intrathecal (spinal) placement. A test dose of lidocaine with epinephrine
is given (typically 3–5 mL of a 2% concentration) and signs and symptoms of
intravascular injection are sought. The heart rate will increase if epinephrine
is injected IV, and the patient may experience symptoms such as tinnitus,
perioral numbness, or metallic taste. If 60–100 mg of lidocaine were injected
intrathecally, an immediate spinal anesthetic would be obtained.
After verifying proper position of the epidural catheter, what drugs will
you use?
Assuming neither intravascular nor intrathecal placement is detected,
an additional 10–15 mL of lidocaine can be injected in divided doses to
obtain a low thoracic dermatomal level and motor blockade of the legs.
Care should be taken not to inject too much drug without ensuring that
the block is symmetrical (or at least that the operative site is numb). The
case can be continued with lidocaine, or a longer-acting local anesthetic,
such as bupivacaine (0.5 or 0.75%) or ropivicaine (1%), can be given to
ensure a dense block for surgery.