Discuss the options for induction of anesthesia in a primary hip
arthroplasty.
General anesthesia or neuraxial anesthesia can
be per-formed for total hip arthroplasty. Neuraxial anesthesia includes spinal,
epidural, or combined spinal/epidural anesthesia. When deciding on an
anesthetic technique, the advantages and disadvantages need to be considered
for each patient.
For general anesthesia, some of the advantages
include a secured airway, excellent muscle relaxation, and the ability to
extend the anesthetic for as long as the surgery takes. Disadvantages include a
high incidence of postoperative nausea and vomiting, hemodynamic changes, and
poor postoperative pain control. The advantages of neuraxial anesthesia include
good postoperative pain control, decreased incidence of deep vein thrombosis,
less nausea and vomiting, and decreased blood loss. Disadvantages include
hemodynamic changes, possibility of postdural puncture headache, and possible
airway management diffi-culty if excessive sedation is used or if there is a
need to convert to general anesthesia in the middle of the procedure.
When planning any general anesthetic, options
for securing the airway must be carefully considered. If there is no history of
cervical arthritis, routine endotracheal intu-bation may be performed. However,
it may be prudent to use a depolarizing muscle relaxant because of the
possibil-ity of an unrecognized difficult intubation secondary to
cricoarytenoid arthritis. If there is a history of cervical arthritis,
endotracheal intubation with in-line cervical sta-bilization may be warranted. Fiberoptic
intubation, either with the patient awake or after induction of anesthesia, may
be the wisest option in selected patients. As in all potential difficult airway
situations, it is imperative that the anesthesiologist be prepared with
alternative methods of securing the airway should the initial plan fail.
Neuraxial anesthesia can also be performed
safely but there are several considerations that need to be addressed:
·
Duration of block: Spinal anesthesia, though quick and easy to perform, has a finite duration
of action deter-mined by the local anesthetic used. Since there is no
indwelling catheter, the duration of the block cannot be extended once the
effects begin to wear off. An epidural in this setting has the advantage of the
ability to prolong the effect of the block by the presence of a catheter that
enables subsequent dosing. Though a combined spinal/epidural anesthetic is
commonly used, it has the disadvantage that the epidural catheter’s efficacy
will not be tested until the spinal anesthetic has begun to wear off during the
procedure. If the catheter is not functioning, the anesthesiologist will be
faced with a patient in the lat-eral decubitus position requiring conversion to
a general anesthetic. In the patient with a difficult airway, it is probably
prudent to perform an epidural (without a spinal) from the onset to ensure its
efficacy. This is not completely fail-safe because despite initial success,
epidurals occasionally become non-functional.
·
Patient comfort: The lateral decubitus position is
uncom-fortable for most patients and it is usually necessary to provide
sedation. As the procedure progresses, patients tend to become restless despite
sedation and it may be necessary to increase the sedation to the point where
air-way obstruction may occur.
·
Thromboembolism prophylaxis: The placement of neu-raxial anesthesia and
removal of an epidural catheter needs to be coordinated with the surgeon’s plan
for thromboembolism prophylaxis (see below).
·
Length of procedure: Many anesthesiologists will have their own threshold for deciding
whether to do general versus neuraxial anesthesia. A reasonable plan would be
to do general anesthesia if the procedure is expected to last for more than 3–4
hours. This commonly occurs for revision hip arthroplasties as opposed to
primary hip replacements. The length of the procedure will also depend on the
surgeon.
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