anaesthesia for cesearean section a quick review

1. ANAESTHESIA FOR CESEAREAN
SECTION
By Dr. Gyanendra JR 3
MODERATOR
DR.YOGESH MANIK (MD,FIPM)
April 19 1

2. General Approach
to the Obstetric Patient
• All patients entering the obstetric suite potentially
require anesthesia services, whether planned or
emergent.
• Patients requiring anesthetic care for labor or
cesarean section should undergo a focused
preanesthetic evaluation as early as possible.
• This should consist of a maternal health history,
anesthesia and anesthesia-related obstetric history,
blood pressure measurement, airway assessment, and
back examination for regional anesthesia.April 19 2

3. April 19 3

4. How do you diagnose fetal distress and
what are the causes
The term fetal distress is too broad and vague and based on the
fetal heart rate patterns. Normal labor is a process of repeated
fetal hypoxic events, which results in acidemia.
• Normal parturition is an asphyxiating event for the fetus and
identification of fetal distress based upon fetal heart rate is
imprecise and controversial. The NICHD fetal monitoring
workshop classifies the fetal heart rate patterns as follows:
• ..Normal
• –Baseline 110–160 bpm
• –Variability 6–25 bpm
• –Accelerations present
• –No decelerations
April 19 4

5. CONT..
• Intermediate
• No consensus
• Severely abnormal
• –Recurrent late or variable decelerations with zero variability
• –Substantial bradycardia with zero variability.
There has been consensus about the definitions of fetal heart rate
at the extremes of normal and severely abnormal patterns.
• Causes of fetal distress
• Maternal hypotension
• Placental abruption
• Umbilical cord compression (secondary to cord prolapse/
oligohydramnios)
• Pregnancy-induced hypertension
• Uterine hypertonus. 5

6. Mendelson’s syndrome
• Mendelson was the first who described acute chemical aspiration
pneumonitis. Patients are considered at risk for aspiration
pneumonitis if gastric volume exceeds 25 mL (0.4 mL/kg) and pH
is less than 2.5.
• Early signs include:
• Cyanosis
• Tachycardia
• Massive pulmonary edema
• Bronchospasm occurs often (unlike with amniotic fluid
embolism)
• Hypotension
• Hypovolemia with hemoconcentration (the reactive transudation
of fluid into the lungs contributes to this).
April 19 6

7. CONT..
• Later cardiac failure may develop and accompanying this.
There may be:
• Increased pulmonary artery pressure
• Reduced static lung compliance
• Falling arterial oxygen
• Severe metabolic acidosis (usually develops later)
• Infection is not usually a feature
• Chest X-ray shows pulmonary edema and patchy atelectasis
(but there is often poor correlation between the extent of
pulmonary damage and the radiological appearance).
• Differential diagnosis
• Amniotic fluid embolism
• Pulmonary embolus
April 19 7

8. CONT..
• Prevention of Mendelson’s syndrome: Preventive measure may
be applied in labor (particularly in patients at risk of having a
cesarean section), before cesarean section and postpartum (for
example with anesthesia for retained placenta) and include
Avoidance of general anesthesia where possible, for example
by use of regional anesthesia, epidurals, etc.
• Oral alkali in labor to reduce pH of stomach contents.
Different drugs and preparations have been used alone or in
combination with the aim of raising pH above 2.5 and
reducing volume of gastric contents below 25 mL. It is
assumed that this will reduce the risk of aspiration.
April 19 8

9. Drugs used include:
• –Sodium citrate is effective at elevating gastric pH
but not at reducing gastric volume.
• Ranitidine, orally or intravenously. Used
intravenously at induction or as a pre-medication
orally is effective. It is also effectively used in
combination with sodium citrate.
• Cimetidine orally, intramuscularly or intravenously is
effective.(not popular)
• Metoclopramide used intravenously with oral sodium
citrate reduced volume of gastric contents and pH.
April 19 9

10. ANESTHETIC TECHNIQUE LSCS
• The choice depends on:
• Indications for the surgery
• The degree of urgency
• Maternal status
• Spinal Anesthesia
• Advantages:
• Rapid onset
• Provides dense block
• Small doses of local anesthetic is used, so there is minimal
transfer of drug to fetus
• Failures are very infrequent with block
• Decreased risk of failed intubation and aspiration of gastric
contents
April 19 10

11. Cont..
…Avoidance of depressant agents
• Ability of mother to remain awake and enjoy the birthing
experience
• it has been suggested that blood loss is reduced under regional
anesthesia.
• Disadvantages:
• Higher incidence of hypotension.
• Finite duration of anesthesia.
• Despite achieving an adequate (T4) block, some women under
spinal anesthesia will experience some degree of visceral
discomfort during section (particularly in situation in which
the obstetrician exteriorizes the uterus). The quality can be
improved by adding opioids.
April 19 11

12. Cont..
• PDPH with larger needles.
• Total spinal block—a rare and serious complication
that occurs after excessive cephalad spread of the
local anesthetic.
• Hematoma: The incidence of neurologic injury
resulting from hematoma associated with spinal is
very low with estimates of 1 in 220,000.
April 19 12

13. Cont..
• Epidural Anesthesia
• Advantages:
• It provides flexibility, when catheter is placed for labor
analgesia and can be used for section The volume of
local anesthetic drug can be titrated Incidence of
hypotension is less.
• All advantages of regional block as mentioned above.
April 19 13

14. Cont..
• Disadvantages:
• ƒƒTakes a little longer time for insertion and institution
of analgesia
• Large doses of local anesthetic are used to achieve
adequate levels
• Failures including incomplete or patchy block are
more frequent than spinal.
April 19 14

15. Walking epidural
• Also called minimal motor block epidural.
• OAA guidelines
• Does not advocate route use of CSE.
• Early in labor when local anaesthetics not
preffered.
• Late in labor when immediate analgesia is
required.
• initial profound analgesia when onging
analgesia not required eg.rupture of membrane
in an anxious mother.
April 19 15

16. Cont..
• When rapid analgesia required and epidural catheter
catheter may be useful for later intervention (trial for
forceps extraction where cesearean may follow.
• Technique:
• Epidural catheter at higher space,SABat an interspace
lower.
• Epidural catheter besides spinal needle in same place.
• Needle through needle technique.
April 19 16

17. Cont..
• Criteria for ambulation:
• No obs and medical contraindication.
• Maternal desire to ambulate.
• Presence of second person.
• Ambulate only when spinal anaesthesia with opiod.
• Ability to perform sustained straight leg test.
• <10% change in BP from supine to sitting position.
April 19 17

18. Dosages in walking epidural.
• For initial SAB:
• Fentanyl:10-15 mcg
• Sufentanyl:5-10 mcg
• Bupivacaine:1.25-2.5 mg
• For later epidural block
• 0.625-0.125 % bupivacaine at 8-15 ml/hr.
• 1-2 mcg of fentanyl or 0.03-0.05mcg of
sufentanyl used as an additive.
April 19 18

19. CONTINUOUS SPINAL ANESTHESIA
• To perform continuous spinal anesthesia, the
anesthesiologist pierces the dura with an epidural needle
and then threads the epidural catheter 3 to 4 cm within the
intrathecal space.
• Catheter placement can be tested by aspiration of CSF.
• Because a catheter is being used, smaller doses can be
given in an incremental fashion.
• Such administration is particularly advantageous in high-
risk parturients such as those with cardiac disease,
respiratory disease, morbid obesity, and neuromuscular
disease.
April 19 19

20. APGAR SCORE
April 19 20
Apgar score is a useful aid to evaluate the need for infant resuscitation applied at 1 and
5 minutes after birth.
The score was devised in 1952 by Dr Virginia Apgar. An Apgar score of
10 is in practice rarely assigned.
Most infants are in excellent condition at birth and have Apgar score of 7 to 10.
A low 1 minute Apgar score does not correlate with the infant’s future outcome. Change
in score between 1 and 5 minutes is a useful index of effectiveness of resuscitation
efforts.
Apgar scores at 1 and 5 minutes correlate poorly with either cause or outcome.
Correlation of the Apgar score with future neurological outcome increases when the
score remains 0 to 3 at 10, 15 and 20 minutes.

21. Cont..
• To reduce the risk of headache after this technique,
• The epidural needle should be turned so that it is
parallel to the dural fibers at the time of insertion.
• Leaving the epidural catheter in situ for more than 12
hours.
• Injecting a bolus of preservative-free normal saline
before removal of the catheter.
April 19 21

22. CSE Technique
• The classic technique required the use of large-bore
epidural needles; newer techniques use a 32-gauge
micro catheter inserted through a 26-gauge spinal
needle.
• Abandoned after withdrawal of these catheters by the
FDA.
• The advantages of continuous spinal anesthesia,
however, remain, and macrocatheters (e.g., placing an
epidural catheter intrathecally) can be used in high-
risk parturients.
April 19 22

23. General Anaesthesia
Advantages:
• It can be given very quickly,
• blood pressure is more easily controlled,
• breathing is more easily controlled once the
ability to breathe for the patient is obtained.
• On patients with bleeding and clotting
abnormalities, patients with neurological
problems, patients with infections that might be
spread to the spinal area if regional anesthesia is
done, etc
April 19 23

24. Cont..
• Disadvantages:
• the mother is unconscious and therefore unable to
participate in the process of birth or interact with the
baby once it is delivered.
• After the operation, general anesthesia wears off
relatively quickly and can result in greater
postoperative pain.
April 19 24

25. Pre operative preparation
• Caesarean sections are frequently performed as emergencies
in unprepared patients.
• The procedure may be complicated by an unfasted patient,
fetal distress, severe haemorrhage, pre-eclampsia etc.
• Prepare and check equipment for obstetric anesthesia in
advance, so that your apparatus and drugs are immediately to
hand.
• This saves valuable time in an urgent case.
• Particular attention should be paid to the function of the
laryngoscopes, the endotracheal tube and cuff, and the suction
apparatus.April 19 25

26. Suggested Technique of General
Anesthesia for Cesarean Section
1. Administer a nonparticulate antacid. Additional agents such as
metoclopramide or an H2 blocker should be considered in
patients at high risk for aspiration or failed intubation.
2. Apply routine monitors, including electrocardiography, pulse
oximetry, and capnography. Ensure that suction is functioning
and that equipment to correct failed intubation is readily
available.
3. Position the patient in a manner to achieve left uterine
displacement and optimal airway position.
4. De-nitrogenate with a high flow of oxygen for 3-5 minutes.April 19 26

27. Cont..
• After the drapes are applied and the surgeon is ready, initiate a
rapid-sequence induction with thiopental, 4.0-5.0 mg/kg, and
succinylcholine, 1.0-1.5 mg/kg.
• Apply cricoid pressure and continue until correct position of
the endotracheal tube is verified and the cuff is inflated
• Locate the most prominent protuberance on the front of the
neck in the midline (the thyroid prominence).
• Find this point then run your finger towards the patients feet
(staying in the midline) until you feel your finger drop into the
cricothyroid notch or membrane. The next horizontal bar is the
cricoid cartilage.
• Place the thumb and index finger on either side of the cricoid
cartilage and press directly backwards at a force of 20–30
newtons against the cervical vertebrae, which is about 2–3
kilograms (10 N = ~ 1 kg) .
April 19 27

28. Cont..
• 6. Ventilate with 50% oxygen and 50% nitrous oxide
and a volatile anesthetic as necessary.
• Maintain normocarbia and use muscle relaxation as
necessary with either a nondepolarizing muscle
relaxant.
• 7. After delivery, administer an opioid or a
benzodiazepine.
• Add oxytocin to intravenous fluids.
• 8. Insert an orogastric tube before completion of
surgery.
April 19 28

29. Cont..
• 9. Reverse neuromuscular blockade as necessary at
completion of surgery.
• 10. Extubate when the patient is awake, the
anesthesia is adequately reversed, and the patient is
following commands
April 19 29

30. If you had unexpectedly been unable to intubate the
patient, how would you manage the airway?
• Obstetrics is one of the few areas of medicine where
there is a “true” emergency. There are two lives at
risk, that of the mother and the baby.
• In the same manner as for the ASA difficult airway
algorithm, initial assessments are required and
subsequent decisions are made based on these
assessments.
• The initial assessments include evaluation of the
maternal airway and fetal status. The clinician needs
to decide whether the airway is difficult, as an
expected difficult airway is easier to manage than an
unexpected difficult airway.
April 19 30

31. Cont..
• Although “conventional wisdom” endorses a regional
technique in the expected difficult airway, complications
or failure of the regional technique may make it necessary
to intubate the trachea. Thus, a backup plan is necessary,
with the availability of appropriate equipment.
• The difficult and failed obstetric airway is a problem for
all involved in the care of the pregnant patient in the labor
and delivery room. All anesthesia providers must be
trained in the assessment and care of the obstetric airway.
• It is necessary to have a difficult airway chart, which
should include: proseal LMA, Intubating LMA,
combitube, fibreoptic flexible bronchoscope,
cricothyrotomy set with jet ventilation.
April 19 31

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33. THANKSFOR LISTENINGCAREFULLY
April 19 33