POSTOPERATIVE ANALGESIA IN ORTHOPEDICS
Pain after orthopedic surgery depends on the site and extent of
surgery and the preoperative use of analgesics by the patient (see Chapter
72
). The techniques used are further defined by the facilities available
in the hospital. Without a postoperative pain service, systemic narcotics may be
the mainstay of therapy. If a postoperative pain service is available, a variety
of continuous infusions or patient-controlled analgesia modalities can be used to
optimize pain therapy and augment recovery.
Orthopedic surgery lends itself to regional anesthesia. Peripheral
blocks with bupivacaine or ropivacaine can provide 12 to 24 hours of significant
analgesia, which is often sufficient to eliminate the need for intramuscular or intravenous
narcotics. Alternatively, infusions of local anesthetic by means of catheters inserted
into the femoral,[177]
popliteal,[178]
or brachial plexus[179]
may provide significant
postoperative analgesia. Intra-articular injections of local anesthetic[180]
[181]
or narcotic[182]
[183]
can provide effective analgesia, facilitating
early discharge after ambulatory surgery.
Epidural analgesia with a combination of low-dose local anesthetic
(e.g., 0.05% to 0.1% bupivacaine) in combination with a narcotic (e.g., 2 to 5 µg/mL
of fentanyl or 10 µg/mL of Dilaudid) provides excellent analgesia after lower
extremity surgery. These can be administered as infusions (3 to 10 mL/hour) with
patient-controlled analgesia. The rates must be adjusted to accommodate for changing
pain patterns and accumulation of drugs. Nonsteroidal anti-inflammatory drugs can
be used to augment the analgesia,[184]
[185]
although their use is not routinely recommended.[186]
Higher doses are required after knee surgery than after hip surgery. The cyclooxygenase-2
inhibitors provide effective pain relief and reduce postoperative opioid requirements
after orthopedic procedures.[187]
They also have
decreased gastrointestinal and antiplatelet effects compared with traditional nonsteroidal
anti-inflammatory drugs.[188]
Intrathecal infusions
of bupivacaine are not recommended for postoperative pain control in orthopedic procedures.
[189]
Effective analgesia with epidural infusions or peripheral blockade
reduces narcotic requirements, provides better analgesia, reduces catabolism,[190]
and results in improved rates of rehabilitation after total-knee replacement.[120]
[191]
To optimize the potential advantage of the
analgesia, early rehabilitation should be encouraged.[192]
There are several limitations to the use of catheter techniques
for postoperative analgesia after orthopedic surgery. First, their use is contingent
on an effective pain service operating with the cooperation of the nurses and orthopedic
surgeons. Second, these modalities must be used in conjunction with the perioperative
management of thromboembolism. The risk of using epidural catheters is increased
when low-molecular-weight heparin (LMWH) is used,[193]
[194]
whereas there appears to be minimal risk with
aspirin or warfarin.[195]
At The Hospital for Special
Surgery, almost all patients undergoing total-hip or total-knee replacement receive
postoperative epidural analgesia for 24 to 72 hours postoperatively. Patients are
concurrently given aspirin or warfarin after surgery in combination with foot pumps,
foot exercises, and early ambulation. LMWH is not used in conjunction with epidural
analgesia. No clinical epidural hematomas have been identified among the more than
2000 cases performed annually at The Hospital for Special Surgery.
The final complicating factor is related to persistent lower extremity
nerve injury. Patients who are at risk for compartment syndrome should not have
epidural infusions of local anesthetic or lower extremity nerve blocks because they
may mask the early diagnostic signs (i.e., excessive pain, numbness, or muscle weakness).
[196]
[197]
This
applies particularly to patients with fractures of the tibia and fibula.[198]
A related problem concerns the use of epidural analgesia in patients who are at
risk for nerve injuries after surgery, particularly peroneal palsy after complicated
total-knee replacement.[195]
[199]
[200]
[201]
Patients
with
valgus deformities and those undergoing high tibial osteotomy are at risk for peroneal
palsy after surgery.[202]
If the palsy is diagnosed
early, the knee can be flexed, bandages changed, and other care instituted to limit
injury to the nerve. An epidural infusion can delay the diagnosis, increasing the
risk of permanent nerve damage. In these cases, it is preferable to avoid epidural
analgesia altogether to avoid confusion and focus on early detection of potential
neurologic deterioration. Epidural anesthesia and analgesia can be used to remove
an infected prosthesis because the risk of epidural abscess in this setting is negligible.
[203]
