Epidural analgesia is a form of regional analgesia, which can be used for relief
from the pain of labor and childbirth and also used in cesarean
delivery. In this procedure a local anesthetic agent is injected into
the epidural or peridural space.
The epidural space contains
areolar tissue, fat, lymphatics and the internal venous plexus. The
vessels of internal venous plexus become engorged during pregnancy because of this the volume of the epidural space becomes appreciably reduced.
To give obstetrical analgesia usually needle is passed through a
lumbar inter vertebral space, whereas to give caudal epidural analgesia
needle is passed through the sacral hiatus and sacral canal.
The advantage of epidural analgesia is, although normally one
injection may be used, but if necessary the injections can be repeated
by putting an indwelling catheter or can be given by continuous
infusion using a volumetric pump.
Continuous lumbar epidural block:
In case of vaginal delivery to achieve complete analgesia from the pain of labor a block from
the
T10 to the S5 dermatomes is needed. And in cesarean delivery, a block
extending from the T4 to the S1 dermatomes is desired.
The
spread of the anesthetic depends upon the location of the catheter tip,
the dose, concentration and volume of anesthetic agent used.
The anesthetic agents normally used are:
2-Chloroprocaine:
And
2 to 3% concentrated 300 to 750 mg dose in 15 to 25 ml solution used in
epidural block for caesarean delivery with average duration of action
for 30 to 60 min.
Lidocaine:
2
% concentrated 300 to 450 mg dose in 15 to 30 ml solution used in
epidural block for caesarean delivery with average duration of action
for 60 to 90 min.
Bupivacaine:
0.5
% concentrated 50 to 100 mg dose in 15 to 20 ml solution can be used in
epidural block for caesarean delivery with average duration of action
for 90 to 150 min.
0.25
% concentrated 50 to 100 mg dose in 8 to 10 ml solution used in
epidural block for vaginal delivery with average duration of action for
60 to 90 min.
Ropivacaine:
0.5
% concentrated 75 to 100 mg dose in 15 to 20 ml solution can be used in
epidural block for caesarean delivery with average duration of action
for 90 to 150 min.
0.25
% concentrated 20 to 25 mg dose in 8 to 10 ml solution used in epidural
block for vaginal delivery with average duration of action for 60 to 90
min.
The
spread of the anesthetic also depends on the position of the woman,
whether she is head-down, horizontal or head-up. The individual
variations in the epidural space anatomy also will affect the block, and
in some cases, synechiae may preclude a completely satisfactory block.
One
more thing to be cautious is that the catheter tip might move from its
original location during the course of labor as the woman moves because
of pain.
Technique of giving epidural analgesia:
· Before giving anesthesia informed and written consent to be taken from th patient and it to be informed to obstetrician.
· Vitals of the woman to be monitored and continuous fetal heart rate monitoring to be done.
· Preanesthetic hydration to be given to prevent hypotension with around 1 lit of crystalloids.
· By
putting the woman either in lateral decubitus or in sitting position,
epidural needle to be introduced into epidural space depends which type
of delivery is planned.
· The
epidural space is identified by loss of resistance and the epidural
catheter to be threaded 3 to 5 cm into the epidural space.
· To identify the tachycardia which may result from accidental intravenous injection of the drug, test dose
of 3 ml of 1.5% lidocaine with 1:200,000 epinephrine or 3 ml of 0.25%
bupivacaine with 1:200,000 epinephrine is injected after careful
aspiration and after uterine contraction. Signs of spinal blockade can
also be identified by test dose.
· If no reaction noted then one or two 5 ml doses of 0.25% of bupivacaine can e injected to get cephalad sensory level up to T10.
· After
15 to 20 min the block to be assessed by loss of sensation to prick or
cold. If no block occurred or block is inadequate catheter to be
replaced. In case of asymmetrical block the catheter to be withdrawn to
0.5 to 1 cm and additional 3 to 5 ml of 0.25% bupivacaine to be
injected.
· Analgesia
is maintained by intermittent boluses of similar volume, or small
volumes of the drug are delivered continuously by infusion pump.
· The
addition of small doses of a short-acting narcotic, either fentanyl or
sufentanil, has been shown to improve analgesic efficacy for labor or
cesarean delivery.
· The woman can be placed in lateral or in semi lateral position to avoid aortocaval compression.
· Vitals of the patient, fetal heart rate and level of analgesia and intensity of motor block to be monitored periodically.
· To
tackle any complications that may arise appropriate resuscitation
equipment and drugs must be available during administration of epidural
analgesia.
Complications of epidural analgesia:
Though epidural analgesia provides good relief for
most of the women from the pain of labor and delivery , some
complications can occur. So, close monitoring including the level of
analgesia to be performed by trained personnel.
The complication which can arise are:
Total spinal blockade:
Total spinal block can be caused by dural puncture with inadvertent subarachnoid injection.
In complete spinal block, hypotension and apnea promptly develop and must be immediately treated to prevent cardiac arrest.
Treatment:
In
the undelivered woman by positioning her laterally, there by uterus
immediately displaces to lateral side and aortocaval compression
decreases.
Effective ventilation to be established preferably by tracheal intubation.
And to correct hypotension intravenous fluids and ephedrine are to be given.
Personnel and facilities must be immediately available to manage this complication.
Ineffective analgesia:
For the establishment
of effective pain relief with maximum safety some time takes. With
continuous epidural infusion regimens such as 0.125-percent bupivacaine
with 2-µg/mL
fentanyl, 90 percent of women rate their pain relief as good to
excellent, and 95 percent express a desire for the same type of
analgesia during a future delivery.
But
in some studies few women complained that epidural analgesia is
inadequate and they experienced three or more episodes of pain or
pressure.
Risk factors for such breakthrough pain included nulliparity, heavier fetal weights,
and
epidural catheter placement at an earlier cervical dilatation. If the
epidural analgesia is allowed to dissipate before another injection of
anesthetic drug, subsequent pain relief may be delayed, incomplete, or
both.
Because
of some of these factors some women initially given epidural analgesia
may require a general anesthetic for caesarean delivery.
With
the lumbar epidural technique sometimes, perineal analgesia for
delivery is difficult to obtain, at that time a low spinal or pudendal
block or systemic analgesia can be added.
Hypotension :
Epidurally injected analgesic agents may cause hypotension and decreased
cardiac output by blocking sympathetic tracts.
In
normal pregnant women, hypotension induced by epidural analgesia
usually can be prevented by rapid infusion of 500 to 1000 mL of
crystalloid solution, or treated successfully as described for spinal
analgesia.
Maintaining a lateral position minimizes hypotension compared with the supine position by preventing aortocaval compression.
Despite
these precautions, hypotension is the most common side effect and is
severe enough to require treatment in one third of women.
Central nervous stimulation:
Convulsions
are an uncommon but serious complication.Immediate steps to be taken
are controlling the convulsions, establishing the airway and delivering
the oxygen.
To
abolish the peripheral manifestations of the convulsions and to allow
tracheal intubation succinylcholine is used. To inhibit convulsions
centrally thiopental or diazepam can be used. Magnesium sulphate may be
used in dosage used for eclampsia to control convulsions.
Maternal pyrexia:
It
is found that the mean temperature in laboring women given epidural
analgesia was significantly higher than in those given meperidine. Some
studies have confirmed an increase in intrapartum fever.
Some
other important risk factors for maternal pyrexia are length of labor,
duration of ruptured membranes and number of vaginal examinations.
The
frequency of intrapartum fever was found to be 10 to 15 but the
precise etiology of maternal hyperthermia with epidural use is unclear.
The occurrence of maternal pyrexia can be explained by two thoughts that either fever
results from maternal-fetal infection or is caused by dysregulation of body temperature. In these two infection was identified as a reasonable explanation after studying placental histopathology in these women.
In
some studies after labor with epidural analgesia, it was noted that
intrapartum fever occurred only with placental inflammation. This
suggests that fever is due to infection rather than to the analgesia
itself. But other studies contradicted that proposed mechanism is
alteration in the hypothalamic thermoregulatory set point, impairment
of peripheral thermoreceptor input to the central nervous system with
selective blockage of warm stimuli or imbalance between heat production
and heat loss.
Currently incomplete information is available regarding the underlying cause.
Back pain:
Although
an association between epidural analgesia and back pain has been
reported by some clinicians, others have not found such a relationship.
Some
studies are showing that postpartum back pain was common after epidural
analgesia, but persistent or chronic back pain was uncommon. Whereas
some other studies do not support an association between the use of
epidural analgesia and development of new, long-term backache.
Effect of epidural analgesia on Labor:
According to many studies, it is shown that epidural analgesia prolongs labor and increases the need for oxytocin stimulation.
Epidural
analgesia also shown to prolonge the active phase of labor by 1 hour
and also found to increase the need for instrumental delivery due to
prolonged second-stage labor. But no adverse neonatal effects are noted.
Effect of epidural analgesia on fetal heart rate:
With epidural analgesia no deleterious effects were identified.
Epidural analgesia was associated with improved neonatal acid-base status compared with that with meperidine.
Epidural analgesia leading to cesarean delivery:
According to several
studies it is shown that labor epidural analgesia is associated with
increased cesarean deliveries. But available evidence is insufficient
to establish such an association.
Many
investigators belief that the epidural administration of dilute
solutions of local anesthetic is less likely to increase cesarean
delivery rates than concentrated solutions.
described the effects of introduction of an on-demand labor epidural analgesia service at
The
only significant difference that was prominently shown is increased
duration of second-stage labor by approximately 25 minutes.
According
to above findings it can be concluded that all women should have access
to effective pain relief during labor and the fear of increasing the
risk of cesarean delivery should not preclude women from choosing
epidural analgesia during labor.
Timing of epidural placement: an
association between early epidural placement and a higher rate of
cesarean delivery was noted in some studies. Whereas others have shown
no difference in early versus late epidural placement in the rates of
cesarean birth, forceps delivery or fetal malposition.
At present there is insufficient evidence to justify that waiting until a certain degree of
cervical dilatation or fetal station is reached before instituting epidural analgesia is needed or not.
Safety of epidural analgesia:
The
relative safety of epidural analgesia is attested by many people with a
very low incidence of complications and maternal deaths in their
experience.
Other
complications are pruritis, failed regional block needing general
anesthesia, formation of epidural abscess or hematoma etc.
Contraindications of epidural analgesia:
The absolute contraindications to epidural analgesia are:
Refractory maternal hypotension:
Contraindication to epidural analgesia include actual or anticipated serious maternal hemorrhage, leading to maternal hypovolemia and hypotension.
Maternal coagulopathy:
Disorders of coagulation and defective hemostasis also preclude the use of
spinal analgesia. Advise against epidural analgesia is usually given if the platelet count is below 100,000/µL.
But no cases were found in which bleeding was caused by regional
analgesia in thrombocytopenic women. Actually this method is recommended
than general anesthesia as in the latter it may become difficult to
intubate or ventilate.
The conclusion is that women with platelet counts of 50,000 to 100,000/µL may be
considered as potential candidates for regional analgesia.
Women on anticoagulation:
If women
receiving anticoagulation therapy are given regional analgesia are at
increased risk for spinal cord hematoma and compression
Recommendations for the women taking anticoagulants:
· Women
receiving unfractionated heparin therapy with a normal activated
partial thromboplastin time (aPTT) and women receiving prophylactic
doses of unfractionated heparin or low-dose aspirin can be offered
regional analgesia.
· In women
receiving once-daily low-dose low-molecular-weight heparin, regional
analgesia can be given 12 hours after the last injection. And low-molecular-weight heparin should be withheld for at least 2 hours after the removal of an epidural catheter.
· No sufficient data is available regarding
the safety of regional analgesia in women receiving twice-daily
low-molecular-weight heparin and it is not known whether delaying
regional analgesia for 24 hours after the last injection is adequate.
Untreated bacteremia:
If patient having generalized bacterial infection better not to give epidural anesthesia.
Infection over the site of needle placement:
Epidural puncture is contraindicated when the skin or underlying tissue at the site of needle entry is infected.
Neurological disorders:
These disorders are considered to be contraindications as they may sometimes become
exacerbated because of anesthetic agent.
Presence of any mass lesion causing increased intracranial pressure is also contraindication for epidural anesthesia.
Also
if patient undergone any spinal surgery previously like laminectomy to
be enquired before proceeding as it may cause problem in giving
anesthesia.
Preeclampsia:
If patient is having severe preeclampsia if it become further complicated with significant hemorrhage there occurs markedly decreased blood pressure when subarachnoid analgesia is used.
The
conclusion is that with severe preeclampsia, epidural analgesia is
preferable than subarachnoid block and general anesthesia. The general
anesthesia especially is having inherent risks of difficult intubation
due to airway edema and cerebrovascular accidents due to increased blood
pressure.
Severe preeclampsia-eclampsia:
Choosing
ideal labor analgesia for women with severe preeclampsia is a
controversial issue. The problems to be considered are hypotension
induced by sympathetic blockade and the dangers from pressor agents
which are given to correct that hypotension and potential for pulmonary
edema following infusion of large volumes of crystalloid.
Problems
are there with general anesthesia also as, tracheal intubation may
result in severe, sudden hypertension further complicated by pulmonary
or cerebral edema or intracranial hemorrhage.
So, nowadays most obstetrical anesthesiologists are using epidural blockade for labor and
delivery
in women with severe preeclampsia. As , epidural analgesia for women
with severe preeclampsia-eclampsia can be safely used when specially
trained anesthesiologists and obstetricians are responsible for the
woman and her fetus.
The
conclusion is labor epidural analgesia can be given in women with
hypertensive disorders, but it should not to be considered as therapy.in many studies epidural analgesia provided superior pain relief without a significant increase in maternal or neonatal complications.
Intravenous fluid preload:
Aggressive
volume replacement for maintenance of blood pressure increases the
risk for pulmonary edema, especially in the first 72 hours postpartum,
because though women
with severe preeclampsia have remarkably diminished intravascular
volume total body water will be increased because of the capillary leak
caused by endothelial cell activation. With vigorous intravenous
crystalloid therapy cerebral edema and pharyngolaryngeal edema can also develop.
This
problem can be overcome by limiting the crystalloid preload
administration and slowly administering dilute solutions of local
anesthetic agents, so that vasodilation produced by epidural blockade
is less abrupt.
Epidural Opiate Analgesia:
Nowadays Injection
of opiates into the epidural space to relieve pain from labor has
become popular. They act by interacting with specific receptors in the
dorsal horn and dorsal roots. They will stimulate both cerebral and
spinal opioid receptors.
Normally
opiates are given with a local anesthetic agent such as bupivacaine as
alone opiates usually will not provide adequate analgesia.
The
major advantages of this combination are the rapid onset of pain
relief, a decrease in shivering and less dense motor blockade.
Side
effects of opiates are pruritus and urinary retention. Immediate or
delayed respiratory depression can occur which is worrisome.
To
abolish these symptoms naloxone intravenously can be given, without
affecting the analgesic action. To reduce pruritus, droperidol can be
given epidurally in doses of up to 5 mg.
Combined spinal-epidural techniques:
Nowadays using the
combination of spinal and epidural techniques becoming popular in
providing rapid and effective analgesia for labor as well as for
cesarean delivery.
In
this technique an introducer needle is first placed in the epidural
space. A small-gauge spinal needle is then introduced through the
epidural needle into the subarachnoid space. The above technique is
called needle-through-needle technique.
After
placing the needles a single bolus of an opioid, sometimes in
combination with a local anesthetic, is injected into the subarachnoid
space then the spinal needle is withdrawn and an epidural catheter is
placed.
The
subarachnoid opioid bolus gives rapid onset of profound pain relief
with virtually no motor blockade and the epidural catheter permits
repeated dosing of analgesia. So, the combined method produces excellent
immediate pain relief.
Side
effects were similar between the two groups. One of them is fetal
bradycardia without responding to changing maternal position, oxygen
administration or intravenous ephedrine which may not be associated
maternal hypotension. This side effect can be minimized by using
fentanyl or with a 2.5-µg dose of sufentanil.
Local infiltration for cesarean delivery:
Local block may be used as an adjuvant to regional block occasionally to augment an inadequate or patchy
regional block that was given in an emergency. Or it can be used in
emergency situations to perform a cesarean to save the life of the fetus
in the absence of any anesthesia support.
Technique of local infiltration:
According
to one technique, the skin along the line of the proposed incision is
infiltrated then the subcutaneous, muscle and posterior rectus sheath
layers are injected after opening the abdomen. In it a dilute solution
of lidocaine 30 mL of 2-percent with 1:200,000 epinephrine diluted with 60 mL of normal saline is prepared, and a total of 100 to 120 mL is infiltrated.
Better
to avoid injection of large volumes into the fatty layers as they are
relatively devoid of nerve supply. So, that the total dose of local
anesthetic can be limited. Intraperitoneal manipulations may cause
pain, nausea and hypotension, so each step should be done without
haste.
In
the second technique field block of the major branches supplying the
abdominal wall to be done including the 10th, 11th, and 12th
intercostal nerves and the ilioinguinal and genitofemoral nerves.
The
10th, 11th, and 12th intercostal nerves will be located at a point
midway between the costal margin and iliac crest in the midaxillary
line. The ilioinguinal and genitofemoral nerves will be found at the
level of the external inguinal ring. Only one skin puncture is made at
each of the four sites that is two right and two left sides.
To
block the intercostals nerves the needle is directed horizontally and
injection is carried down to the transversalis fascia, avoiding
injection of the subcutaneous fat. Approximately 5 to 8 mL of
0.5-percent lidocaine is injected. The procedure is repeated at a
45-degree angle cephalad and caudad at this site. The other side is then
injected.
And
to block the ilioinguinal and genitofemoral sites, the injection is
started at a site 2 to 3 cm from the pubic tubercle at a 45-degree
angle. Then the skin overlying the planned incision is injected.
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