Page 143 Guide to Pain Management in Low-Resource Settings

Pharmacological Management of Pain in Obstetrics 131

erences in the spread of local cell volume. Minimal preload of 200–500 mL is good ffFundamental di
anesthetic between a pregnant and nonpregnant woman enough in most situations in combination with a vaso-
must be respected, and an unacceptably high block can re- pressor. Th ere is some evidence that a combination of
sult in spinal (or epidural) anesthesia. Some medical con- colloid and crystalloid i.v. infusion can decrease the in-
ditions can cause additional problems, all related to poor cidence of hypotension. Vasopressin agents commonly
compensatory response to rapid change in afterload in low used to correct hypotension are ephedrine (6–10 mg
cardiac output states, e.g., aortic stenosis, cyanotic congen- i.v. bolus or as an infusion) and phenylephrine (25–100
ital heart disease, and worsening of venous shunting. μg i.v. intermittent boluses). Phenylephrine is a drug of
choice when tachycardia is undesirable.
What are the other pros and Th ere are certain situations when a general anes-
cons for regional anesthesia thetic will be more appropriate than a regional one. Th ese
in caesarian section? situations include maternal refusal of regional blockade,
coagulopathy, low platelet count, anticipated or actual
Regarding the risk of hemorrhage, it appears that there severe bleeding, local infection of the site of insertion of
is less bleeding to be expected in cesarian section under the spinal or epidural needle, anatomical problems, and
regional blocks. In contrast, general anesthesia, when certain medical conditions. Lack of time is the most com-
using inhalation agents, carries the risk of uterine relax- mon reason to choose general anesthesia, although for a
ation and increased venous bleeding from pelvic venous skilled clinician, time is not an issue. If there is an epidu-
plexuses. Although there is a traditionally held view that ral catheter in place, assessment and top-up should not
regional anesthesia should be avoided whenever hemor- take more than 10 minutes, which is usually more than
uence of enough time for the majority of circumstances. flrhage is expected in gestosis, the favorable in
regional blocks on this disease may on the contrary be Maternal hypotension is a common complica-
an argument for regional anesthesia. tion of blockade of sympathetic nerves, most character-
Postoperative pain is better managed after re- istically cardiac sympathetic nerves. Th is complication
gional anesthesia in both obstetric and nonobstetric can lead to a sudden drop in heart rate with low cardiac
patients, perhaps due to a reduction in centrally trans- output, and if aorto-caval compression is not avoided
mitted pain, as suggested in laboratory work. Postopera- there will be persistent hypotension that can compro-
tive recovery is improved, and mothers are able to bond mise the baby. Th e height of a sympathetic block can be
ects in the a few dermatomes higher than the measured sensory ffwith their babies sooner. Th e lack of drug e
newborn, seen when regional anesthesia is used, means level. Th is complication is seen more in women who
less intervention for the baby. Poor condition of the come for elective sections more often than in those who
u- flnewborn after a regional technique is related to a pro- are already in labor, because the reduced amount of
longed time from uterine incision to delivery and to ma- ids after the rupture of the membranes causes less aor-
ternal hypotension, fetal acidosis, and asphyxia, unlike to-caval compression, and because maternal physiologi-
after general anesthesia, where the baby’s low APGAR cal adjustments have already taken place.
score will probably be due to sedation. Supplementation of intraoperative analgesia can
Whenever the newborn is already distressed be used, when performed with vigilance for sedation.
and acidotic, attention must be paid to avoiding aorto- Fifty percent nitrous oxide in oxygen, i.v. ketamine 0.25
caval compression and maternal hypotension. Th e full mg/kg, and fentanyl 1 μg/kg have been shown to be safe
ective. Intravenous sedatives such as diazepam fflateral position must be adopted in all mothers expected and e
to develop severe hypotension. Traditionally used i.v. can help a very anxious mother.
crystalloid infusion preload has been shown to be un-
reliable in eliminating hypotension. Rapid infusion of a Is there a “cookbook”
uid can cause a sudden rise in central approach to spinal anesthesia fllarge volume of
venous pressure and lead to pulmonary edema in pre- for cesarian section?
disposed parturients. Intravenous crystalloid preload
will not reduce the need for vasopressors, and the in- With the smaller needles, with their atraumatic pencil-
fusion must consist of a very large quantity, e.g., 40–59 point tips, the rate of headache is less than 1% unless
ect maternal packed the mother is very short or very tall. Factors like patient ffcantly a fimL/kg, and must signi