23. Obstetric analgesia and anesthesia. Flashcards
At what approximate spinal level do the dural space and the spinal cord, respectively, end
S2, L2
motor nerve supply of the uterus supplied by ?
sympathetic and parasympathetic nerve fibre arise from the lower thoracic and upper lumbar segment of spinal cord
parasympathetic - s2-4
what are the sensory pathway ?
uterine body - afferent nerve information goes to the t10-12
and 1st lumbar of spinal cord
cervix - the pelvic splanchnic nerves also provides parasympathetic - s2-s4
vagina - pundal nerve (s2-s4)
perineum - from the pudendal nerve (S2 to S4)
labia major -
ilioinguinal - 1st lumbar root
1 and second lumbar root
and genital branch of the genitofemoral nerve
what innervates the motor activity of pelvic floor muscles ?
pudendal nerve
. Total spinal block does not inhibit uterine activity, provided what?
blood pressure does not work
oxytocin for the posterior pituitary gland
what is the cause of pain in labour?
sensory pathways from T10 - L1
other cause of pain -
myometrial hypoxia ,
stretching of peritoneum over fundus ,
stretching of cervix during dilation
what are the methods of pain relief ?
psychoprophylaxis - lamaze method , emotional support
sedative and analgesics
regional analgesia epidural paracervical block spinal nerve block pudendnal nere bock perieal infiltration
general anesthesia
the amount of sedative and angesia depends on ?
multiparty - needs less analgesia
Minimal doses of drugs are indicated while the fetus is thought to be premature to avoid neonatal asphyxia.
analgesia modes are divided according to what
The first phase is controlled by sedatives and analgesics.
the first phase is up to 8cm dilatation of the cervix in primigravidae and 6 cm in case of multipara.
The second phase corresponds to dilatation of the cervix beyond the above limits up to delivery.
second phase is controlled by inhalation agents.
what are the opioid analgesics given during first phase ?
pethidine IM - strong sedative , less analgesia
side effects - vomitting, delayed gastric emptying = ranitidine, metoclopromaide
Meperidine IM or PCA pump (gives you a drug for pain when you press a button)
side effects -Repeated use infants may need naloxone at delivery. Maximum placental transfer and neonatal depression occur 2–3 hours of use.
fentanyl -less neonatal effects and less maternal nausea and vomiting. It needs frequent dosing. It can be used as PCA.
what are the inhalation analgesics?
50% nitrous oxide and 50% oxygen mixture
Hyperventilation, dizziness, hypocapnia (resp alkalosis) are the side effects.
taken before contraction occurs and stopped when contractions go
describe regional anesthesia in epidural anesthesia ?
lumbar epidural block:
below l2 (after that it is the caudal equina)
detect the l4 and l5 space give
local anesthesia
with an epidural needle tuohy needle enter the epidural space
a plastic catheter is passed through the epidural tuohy needle -owing to the upward tilt at the end of the needle the catheter is directed upwards 4-5cm
for continuous epidural analgesia
the tuohy needle is the removed and analgesics administered
blood pressure constantly checked and after 3-5 mins we see if they are able to move the lower limb if so indicated at the right space - if not then the catheter is between the dura and arachnid space = intrathecal
if positive bolus dose inserted
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For complete analgesia
a block from T10 to the S5 dermatomes is needed.
For cesarean
delivery a block from T4 to S1 is needed.
what agents are used for epidural anesthesia?
lidocaine for local anaesthetic
bupivacaine or in combination with fentanyl and morphine
when is epidural analgesia given ?
usually only have an epidural during the first stage of labour where contractions well established — but it can be given at any stage of labour
what is the clinical management when given regional analgesia / epidural anesthesia is given ?
crystalloid infusion prior commencing the blockade.
The patient’s blood pressure, pulse and the fetal heart rate should be recorded at 15 minutes interval following the induction of analgesia
hypotension, if occurs, should be treated immediately.
The woman is kept in semilateral position to avoid aortocaval compression.
what is the complication of epidural anesthesia?
hypotension - that’s why well hydrated before hand
no change in duration of first stage of labor. But second stage of labor appears to be prolonged by 15–30 minutes. This might lead to frequent need of instrumental delivery like forceps or ventouse
Postspinal headache due to leakage of cerebrospinal fluid through the needle hole
describe paracervical block in regional anesthesia
for pain relief during the first stage of labor , from 5cm dilation but most useful towards the end of first stage of labour
place a speculum
a long needle is passed into the vagina
inject Iidocaine submucousaly at 12 o clock int he anterioir lip of the cervix
then using a tenaculum at 12o clock grasp the cervix and inject lidocaine at 2 o clock , 4 o clock , 8 o clock and 10 o clock at the cervicovaginal ruction
wait 2 minutes and then pinch the cervix with forceps. If the woman feels the pinch
can only block the pain of uterine contractions
need pudendal nerve block for perineum pain
what is the contraindication of paracervical block ?
Bupivacaine is avoided due to its cardiotoxicity
placental insufficiency
complication of paracervical block ?
fetal bradycardia - due to decrease placental perfusion
when is the regional anesthesia pudendal nerve block used ?
mostly used for forceps and vaginal breech delivery.
or before epstiotomy
method of pudendal nerve block ?
A 20 mL syringe, one gauge spinal needle and lignocaine hydrochloride are required.
The index and middle fingers of one hand are introduced into the vagina, the middle finger lays on the ishial spine
The needle is passed along the groove of these two fingers
Place the end of the needle guard 1 cm anteriorly and medial to the ischial spine
guard can then be unhooked and the needle advanced a centimetre into the tissue
pierce the vaginal wall and pierce the sacrospinous ligament
aspiration is done to exclude blood, solution is injected. The similar procedure is adopted to block the nerve of the other side by changing the hands
when is local spinal anesthesia used ?
Most women cannot push effectively after a spinal block
so only
often used in emergency c section and assisted delivery such as c section venous and forcep use when no time for epidural
or alleviate the pain during the third stage of labor
spinal anesthesia clinical procedure
Spinal anesthesia is obtained by needle going into the subarachnoid space (past the dura mater and arachnoid matter, between the arachnoid matter and pia) containing cerebrospinal fluid which bathes the spinal cord
do it around the the third or fourth lumbar.
Because the spinal cord typically end at the L1 or L2 level of the spine, the needle should be inserted below this between two lumbar vertebrae ( L3 - L5 ) space in order to avoid injury to the spinal cord.
bupivacaine
blood pressure and respiratory rate should be recorded
side effects of spinal anesthesia ?
Hypotension
Postspinal headache—due to low or high CSF pressure and leakage of CSF
Meningitis due to faulty asepsis
Transient or permanent paralysis
Toxic reaction of local anesthetic drugs
Paralysis and nerve injury
when is perineal infiltration anesthesia used ?
used prior to episiotomy
ventouse and forceps use
describe perineal infiltration ?
for epstiotomy
topical anesthesia sprayed
long fine needle syringe with lignocaine hydrochloride is inserted subcutaneously
Two fingers enter the vagina and they are abducted and stretched away from the fetal head to protect it
the are stretched in a way to make to the midline of the fourchetter taut
insert the needle into the middle (downwards) of the fourchette.
aspiration to exclude blood is mandatory.
Release one third of the lidocaine as the syringe is partially withdrawn from the fourchette;
Before the needle is completely removed from the fourchette tilt it so it is at the position where the incision will be made and again inject a third of the lidocaine.
Finally, tilt the syringe to the other side of the proposed incision and give the final dose of lidocaine.
aspirating each time for injecting
wait 3 minutes after procedure
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For outlet forceps or ventouse—Perineal and labial infiltration
topical anestesia sprayed
a long fine needle syringe and about lignocaine hydrochloride are required.
same as epstiotomy and
The needle is then directed anteriorly along each side of the vulva as far as the anterior-third to block the genital branch of the genitofemoral and ilioinguinal nerve. in a fanwise manner
what are the preoperative conditions needed for general anesthesia in c section ?
if elective - 6hrs fasting
in high risk preferably not allowed to eat
h2 ranitidine blocker given night before if elective
antacid orally before to neutralise the existing gastric acid
if emergency - reyels tube aspiration of gastric content
metoclopromide IV after minimum of 3 mins preoxygenation to decrease gastric volume and tone of LES
then induction and intubation
left lateral tilt in theatre table with a wedge on back avoid autocaval compression
uterine incision to delivery - U-D =more than 3 mins = low apgar score and neonatal acidosis
describe the process of general anethseia in c section ?
Preoxygenation with 100% oxygen is administered by tight mask fit for more than 3 minutes.
Induction of anesthesia by thiopental sodium IV , propofol ,ketamine
Muscle relaxants: Succinylcholine is commonly used immediately after the induction drug to facilitate intubation.
intubation
Anesthesia is maintained with 50% nitrous oxide, 50% oxygen and a trace (0.5%) of halothane.
propofone IV
Relaxation is maintained with nondepolarizing muscle relaxant (vecuronium bromide 4 mg or atracurium 25 mg).
what is the complication of general anesthesia ?
gastric content aspiration
Delayed gastric emptying due to high level of serum progesterone, decreased motilin and maternal apprehension during labor is the predisposing factor.
what are the contraindications for epidural anaesthesia?
maternal coagulopathy or anticoagulant therapy
supine hypotension
hypovolema
regional anesthesia such as epidural than general anesthesia is preferred for c section why is that ?
maintain respiration
difference between spinal anesthesia and epidural?
compared to epidural
It has less procedure time and quicker onset
high success rate
last 3-4hrs hours because cannot be ‘topped up’ because there is no catheter put in
affects the spinal cord directly unlike in epidural the
main effect is on the nerve roots leaving the dura matter
An epidural may be given at a cervical, thoracic, or lumbar site,
while a spinal must be injected ONLY below L2 to avoid piercing the spinal cord
