Peripheral nerve block has been used with mixed success for post- cesarean analgesia.
Ilioinguinal Nerve Block
In patients who undergo cesarean delivery with a Pfannenstiel skin
•
incision, bilateral ilioinguinal nerve block with 10 ml 0.5 % bupi- vacaine has been shown to modestly reduce postoperative analge- sic requirements compared to those receiving no block.
When ilioinguinal block is combined with intrathecal morphine,
•
0.15 mg, postoperative analgesic requirements did not differ from patients not receiving the block.
Using ultrasound guidance, catheters may be introduced into the
•
plane between the transversus abdominus and internal oblique muscles anteriorly (the plane where the ilioinguinal nerves lie), allowing for continuous infusion of local anesthetics. When used in conjunction with oral ibuprofen on a fi xed dosage schedule, sup- plemental postoperative morphine requirements were decreased.
Ilioinguinal nerve block may be useful in patients who required gen-
•
eral anesthesia or who have contraindications to neuraxial analgesics.
Obstetric Anesthesia177 Transversus Abdominus Plane Block
As noted above, sensory innervation to the anterior abdominal wall runs between the transversus abdominus and internal oblique muscles. It is possible to introduce local anesthetics into this plane posteriorly, in the triangle of Petit via a loss of resistance technique, and block sensory innervation of the anterior abdominal wall.
Used as part of a multimodal analgesic regimen that included
•
oral acetaminophen, rectal diclofenac, and IV-PCA morphine (see below), supplemental morphine use was signifi cantly lower in patients receiving the block (with ropivacaine 0.75 % 1.5 mg/kg each side) than those who received sham injections. The majority of the benefi t was in the fi rst 12 hours after surgery.
Patient-Controlled Analgesia (PCA)
Intravenous PCA
Patient-controlled analgesia (PCA) is effective and has become popu- lar in some practices for post-cesarean analgesia. Both intravenous (IV-PCA) and epidural (PCEA) PCA have been used for post-cesarean analgesia.
While single injection epidural or intrathecal morphine analge-
•
sia was rated superior (by patients) to analgesia provided by IV-PCA morphine in one series, overall patient satisfaction with IV-PCA was equally high, probably because of the feeling of control that self-administered PCA provides parturients.
Both IV-PCA and neuraxial morphine are markedly more effective
•
than intramuscular injections.
The choice of opioid for use with IV-PCA does not make any
•
consistent difference in patient satisfaction or side effects, when equipotent doses are used.
Use of a basal infusion does not change 24-hour opioid usage, but
•
may decrease pain scores with movement. This minor advantage is offset by the fact that the incidence of nausea is higher when a basal infusion is used.
PCA is an excellent choice to use in combination with neuraxial
•
techniques (i.e., single-shot intrathecal or epidural morphine) for post-cesarean analgesia, and an effective way to titrate postopera- tive analgesia to individual requirements.
178Post-Cesarean Analgesia
Patient-Controlled Epidural Analgesia (PCEA)
Patient-controlled epidural analgesia (PCEA) has a number of advan- tages in the post-cesarean patient:
It gives the parturient a degree of control over her analgesia.
•
It allows the use of local anesthetics, opioids, and other adjuncts
•
(epinephrine) in multiple combinations.
It may decrease the need for physician interventions in the postop-
•
erative period.
Compared to single bolus epidural morphine, use of opioid-only PCEA with fentanyl or sufentanil provides comparable analgesia, but the high total doses of opioid used by parturients raise the question of whether the analgesic effects are mediated primarily by systemic uptake rather than a true spinal mechanism.
As with intravenous PCA, a basal (or “background”) infusion does
•
not signifi cantly improve the quality of pain relief with PCEA.
Background infusions
• do increase sedation.
Background infusions generally increase total drug delivery.
•
When meperidine is used for PCEA, parturients use approxi- mately 50 % less opioid via the PCEA route than the IV-PCA route, and sedation scores are predictably higher in the IV-PCA group (Figure 5.11 ).
Time (h) 12 8
4 0
VAS pain score (0–100)
10 0 20 30 40
16 20 24
Figure 5.11 A comparison of pain scores between patient-controlled analgesia (intravenous PCA) and patient-controlled epidural analgesia (PCEA) after cesarean delivery. The solid line represents the period parturients received PCEA and the dashed line represents the period they received PCA. Pain scores were consistently lower in the PCEA group. Reprinted with permission from Paech MJ et al. Meperidine for patient-controlled analgesia after cesarean section. Anesthesiology. 1994;80:1268–1276.
Obstetric Anesthesia179 Local anesthetics are frequently added to PCEA for post-cesarean analgesia.
The concentration of local anesthetic must be low to avoid signifi -
•
cant sensory or motor blockade, as many patients are ambulatory within hours of surgery.
A concentration of bupivacaine as low as 0.03
• % has been reported
to interfere with ambulation when used in combination with fentanyl or buprenorphine.
A concentration of bupivacaine 0.01
• % does not interfere with
ambulation, but epidural fentanyl consumption is comparable to PCEA fentanyl without added bupivacaine.
It is unclear what benefi t, if any, including dilute bupivacaine in a
•
PCEA solution provides.
Other Adjuncts for PCEA
Clonidine and epinephrine (which both presumably activate α -2 adrenergic receptors) and neostigmine (which prevents the break- down of synaptically released Ach) have also been used with PCEA.
When combined with sufentanil PCEA, both epinephrine and cloni-
•
dine signifi cantly reduce epidural opioid use.
Clonidine causes signifi cant decreases in blood pressure and heart
• rate.
Neostigmine, even at very low doses, signifi cantly increases nausea
•
and vomiting.
Neither clonidine or neostigmine can be recommended for routine
•
use with PCEA.
PCEA can be an effective technique for post-cesarean analgesia.
Whether it offers distinct advantages over epidural or intrathecal mor- phine is a matter of dispute. A disadvantage is the necessity to maintain a functioning epidural catheter in the postoperative period. Further, in many practices cesarean delivery is likely to performed with a single-shot spinal anesthetic technique, without an epidural catheter inserted. PCEA remains a useful technique for selected patients and populations.