Obstetrics
د. بان عامر موسى
Lec. 4
المرحلة الرابعة
Methods of labor analgesia
pain : defined as unpleasant sensation , subjective sensory and
emotional experience associated with real or potential tissue
damage , although pain may be considered the physiological
consequence of normal labor , it may be the harbinger of
pathological process such as obstructed labor , fetal malposition
, uterine hyper stimulation and uterine rupture .
Severe pain stimulate sympathetic autonomic response which is
exacerbated by dehydration and exhaustion , it is characterized
by hyperventilation , tachycardia , hypertension , increase O2
and glucose consumption ,vasoconstriction with decrease blood
flow across the placenta that lead to decrease fetal oxygenation
Non regional analgesia for labor
-Non pharmalogical method of pain relief include:-
Antenatal education , acupuncture , water immersion , massage
and other relaxation techniques .
-Pharmalogical methods include :-
Entonox (50% N2O in O2 )quick onset , short duration of effect
by inhalation
Systemic opioid : Diamorphin ,Pathedin ,Remifantanil
Complications :- nausea ,vomiting ,drowsiness and sedation ,
delayed gastric emptying , short term respiratory depression of
the neonate , possibility of interfering with breast feeding .
Regional analgesia
Epidural analgesia ( extradural ):- is the reliable mean of
providing effective analgesia in labor
Possible regional anesthesia techniques include epidural
analgesia, spinal analgesia (sometimes referred to as the
intrathecal or subarachnoid space), or a combination of epidural
and spinal analgesia.
Uterine contractions and cervical dilatation result in visceral
pain. These pain impulses are transmitted by afferent, slow
conducting sympathetic nerves and enter the spinal cord at the
T10 to L1 level. As labor progresses, the descent of fetal head
and subsequent pressure on the pelvic floor, vagina, and
perineum, generates somatic pain, which is transmitted by the
pudendal nerve (S2-4). These rapidly conducting somatic pain
fibers are relatively difficult to block
In obstetric patients, regional analgesia refers to partial or
complete loss of pain sensation below the T8 to T10 spinal
level. In addition, a varying degree of motor block may be
present, depending on the agents used. Advantages of regional
analgesia include the following
-Provides superior pain relief in first and second stages of labor
-Facilitates patient cooperation during labor and delivery
-Provides anesthesia for episiotomy and instrumental delivery
-Allows extension of anesthesia for cesarean delivery
-Avoids opioid-induced maternal and neonatal respiratory
depression from intravenous opioids
-Besides providing analgesia in labor, regional analgesia may
facilitate atraumatic vaginal delivery of twins, preterm neonates,
and neonates with breech presentation.
-It also helps control blood pressure in women with
preeclampsia by alleviating labor pain, and it blunts the
hemodynamic effects of uterine contractions and the associated
pain response in patients with other medical complications
Contraindications
Regional anesthesia is contraindicated in the
-presence of actual or anticipated serious maternal hemorrhage
and refractory maternal hypotension,
-coagulopathy and anticoagulant therapy
-untreated bacteremia,
-raised intracranial pressure,
-skin or soft tissue infection at the site of the epidural or spinal
placement
-Regional analgesia is also contraindicated in cases of patient
refusal or inadequate practitioner training and experience
-As exacerbation of neurological diseases might be attributed
without cause to the anesthetic agent, many clinicians avoid
regional anesthesia in its presence
-Other maternal conditions such as aortic stenosis, pulmonary
hypertension, or right-to-left shunts are also relative
contraindications to the use of regional analgesia. Only opioids
could be used for labor analgesia in these situations, as they do
not decrease systemic vascular resistance.
For patients with mitral stenosis, regional analgesia
(epidural) is the preferred method
, analgesia is controversial
severe preeclampsia
In women with
due to Obstetrical concerns that regional analgesia include
hypotension induced by sympathetic blockade, danger from
pressor agents given to correct hypotension, and potential for
pulmonary edema following infusion of large volumes of
crystalloid
Conversely, general anesthesia with tracheal intubation may
result in severe sudden hypertension, further complicated by
cerebral or pulmonary edema or intracranial hemorrhage
Over the past 2-3 decades, most obstetric anesthesiologists have
come to favor epidural blockade for labor analgesia in women
with severe preeclampsia.
Currently, practitioners routinely perform regional analgesia
with platelet counts below 100,000, although few will
instrument the spinal/epidural space if the platelet count is
below 50,000. Several studies have reported no complications in
women with platelet counts between 50,000-100,000
Special precautions are needed for patients taking anticoagulants
to avoid epidural or spinal hematoma
Anesthesia
Spinal anesthesia (or spinal anesthesia), also called spinal
block, subarachnoid block (SAB), intradural block and
intrathecal block, is a form of regional anesthesia involving
injection of a local anaesthetic into the subarachnoid space,
generally through a fine needle, usually 9 cm long (3.5 inches).
For extremely obese patients longer needles are available
(12.7 cm / 5 inches).
Spinal anesthesia is the technique of choice for Caesarean
section as it avoids a general anesthetic and the risk of failed
intubation (which is approximately 1 in 250 in pregnant
women). It also means the mother is conscious and the partner is
able to be present at the birth of the child. The post-operative
analgesia from intrathecal opioids in addition to non-steroidal
anti-inflammatory drugs is also good.
If surgery allows, spinal anaesthesia is very useful in patients
with severe respiratory disease e.g. COPD as it avoids
intubation and ventilation. It may also be useful in patients
where anatomical abnormalities may make
very difficult.
Contraindications
Non-availability of patient's consent
Local infection or sepsis at the site of lumbar puncture
or systemic
,
thrombocytopenia
Bleeding disorders
anticoagulation (secondary to an increased risk of a
spinal
Space occupying lesions of the brain
Anatomical disorders of the spine
Hypovolaemia e.g. following massive haemorrhage, including
in obstetric patients
Risks/Complications
Can be broadly classified as immediate (on the operating table)
or late (in the ward or in the P.A.C.U. post-anaesthesia care
unit):
Hypotension (Spinal shock) - Due to sympathetic nervous
system blockade. Common but usually easily treated with
intravenous fluid and sympathomimmetic drugs such as
Ephedrine, Phenylephrine
Post dural puncture head ache (PDPH) or post spinal head ache -
Associated with the size and type of spinal needle used
Cauda equina injury - very rare, due to the insertion site being
too high
Cardiac arrest - very rare, usually related to the underlying
medical condition of the patient
Spinal canal haematoma, with or without subsequent
neurological sequelae due to compression of the spinal nerves.
Urgent CT/MRI to confirm the diagnosis followed by urgent
surgical decompression to avoid permanent neurological
damage
Epidural abscess, again with potential permanent neurological
damage. May present as meningitis or an abscess with back
pain, fever, lower limb neurological impairment and loss of
bladder/bowel function. Urgent CT/MRI confirms the diagnosis
followed by antibiotics and urgent surgical drainage .