2020/4/15
Prof. Dr.Xia Rui
Head of Department
Presented by:- Dr. Pramee
Department of Anesthesia
The First Affiliated Hospital
Yangtze University
1


Anesthetic implications according to physiological changes in parturients
 Effects of anesthetic agents in uteroplacental circulation

Anesthesia for Cesarean section: Regional and GA

Side Effects of Epidural/Spinal Anesthesia

Anesthesia for Painless labor

Analgesia and anesthesia for abnormal obstetrics
2020/4/15 2


Analgesia denotes the state in which only modulation of pain perception is involved. It may be local and affect only a small area of the body; regional and affect a larger portion ; or systemic.

Anesthesia is a triad of hypnosis, analgesia and areflexia by the virtue of anesthetic agents.
2020/4/15 3


In obstetrics , regional anesthesia
 more commonly performed for cesarean delivery
 local anesthetics (spinal , epidural)
 general anesthesia
 systemic medication and endotracheal intubation

Difficulty with intubation , aspiration, and hypoxemia leading to cardiopulmonary arrest are the leading causes of anesthesia related maternal death.
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
There are considerable physiological changes in parturient which can affect the anesthesia technique

Cardiovascular system

Respiration and metabolism

Center nervous system

Gastrointestinal Tract

Hematology and coagulation
 Uterus
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
The anesthetic implication is that these patients due to hyperdynamic circulation can go in congestive heart failure.
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2020/4/15
2.
7


Due to increased minute ventilation, induction with inhalational agents is faster and dose requirement is less, making pregnant patients more susceptible to anesthetic overdose.

Due to decreased FRC,ERV and increased oxygen requirement these patients are vulnerable to go in hypoxia.So,preoxygenation of 5-6 min is required. This is the time required for maternal fetal equilibrium.

Due to capillary engorgement in upper airway chances of trauma and bleeding during intubation is high.

Laryngeal edema can be the prominent feature of PIH patients, making intubation difficult.
2020/4/15 8


Progesterone has got sedative effect decreasing the anesthetic requirement by 25-40%.

MAC ↓ by 20-40%
 ↓ Vasopressor response

There is decrease in local anesthetic requirement by
30-40% for spinal and epidural anesthesia.

More chances of high spinal and epidural in pregnancy.
2020/4/15 9

Parturients are very vulnerable for aspiration due to following reasons:

Gastric emptying is delayed due to progesterone.

Gravid uterus changes the angle of gastroesophageal junction making the lower esophageal sphincter (LES) incompetent.

Progesterone relaxes the LES.

Gastric contents are more acidic.
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
A pregnant patient should always be considered as full stomach even if she is fasting.

The minimum fasting period for elective CS is recommended to be 6 hrs for light meals and 8 hrs for heavy meals.

Preoperative antacids—H2-blockers (Ranitidine 100-
150mg orally or 50mg IV)

Metoclopramide 10mg orally or IV
 Sellick’s maneuver(cricoid pressure)while intubation.
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
Blood volume ↑ 50%, increase in plasma volume ＞ increase in RBC mass → relative anemia

Plasma cholinesterase level is decreased by 25% prolonging the effect of succinylcholine.

Hypercoagulable state in pregnancy:↑ platelet turnover, clotting and fibrinolysis
 ↑ 2,3-DPG→right shift of oxyhemoglobin curve →
↑O
2 delivery
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
In supine position the gravid uterus compresses the inferior vena cava and aorta, decreasing the cardiac output and blood pressure causing Supine hypotension syndrome(SHS) which can cause severe hypotension after spinal anesthesia.
To prevent this patient should be kept in left lateral position by:
 Putting a 15˚ wedge under the right hip
 Tilting the operation table by 15˚to left
 Manually displacing the uterus to left
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
Drugs with molecular weighs ﹤ 600 cross the placenta easily

By simple diffusion according to the principles of
Fick’s law:
A(C

C
F
)
D
Q/T: rate of diffusion
A: the surface area available for drug transfer
C
M
: maternal drug concentration
C
F
: fetal drug concentration
D: membrane thickness
K : the diffusion constant of the drug
At term, transfer of drugs across the placenta↑
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
The rate of drug transfer into the fetus is governed mainly by:

Lipid solubility of drug

Degree of drug ionization
 Molecular weight of the drug

Dose administered
 Placental blood flow

Placental metabolism
 Protein binding.
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
Uterine blood flow is 500-700 ml/min(10% of cardiac output)

Placental blood flow is directly dependent on maternal blood flow.
Effects of anesthetic agents in uteroplacental circulation

Hypotension and drugs causing vasoconstriction can severely compromise fetal well being.
- Ephedrine is drug of choice for treating spinal induced hypotension in pregnancy since it doesn’t decrease placental flow.
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Effects of anesthetic agents in uteroplacental circulation Contd..

Positive pressure ventilation cardiac output by venous return compromise placental flow.

Inhalational agents(higher conc.) hypotension , cardiac output compromise uterine flow

IV agents:

Sodium thiopentone and Propofol blood pressure uterine blood flow

Ketamine uterine hypertonicity uterine blood flow.

Spinal/epidural anesthesia hypotension compromise uterine blood flow.
2020/4/15 17


All anesthetic drugs except muscle relaxants and glycopyrrolate can be transferred to fetus from maternal circulation. So, all drugs should be used in minimum concentration and dosage.

A large fraction of drug coming from placenta to fetal liver(75% of umbilical vein blood flows through liver), so less drug reaches the fetal vital organs(brain, heart).
 Drugs like local anesthetics and opioids which are bases, crosses the placenta in non-ionized form and becomes ionized in the fetal circulation(low pH) and can’t come back to maternal circulation leading to accumulation of drugs in the fetus.
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Distribution of drugs between maternal and fetal compartments
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1. Regional

Spinal anesthesia For Cesarean section

Combined Spinal-Epidural
Anesthesia (CSEA)

Lumbar epidural block For painless labor

Caudal block
2 . Systemic

General anesthesia
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Procedure:
1) Preloading:- Ringer’s Lactate 10ml/kg
2) Patient positioning:- Sitting or left lateral
3) Painting and draping
4) Space: L
2
~L
3 or L
Whitacre, Sprotte
3
~L
4
5) Needle: 25 gauge Quincke or 22 gauge
6) Needle advanced to pierce dura. After free flow of
CSF,
7) Drug used: 0.25~0.5% bupivacaine 2-5mg, with or without narcotic (fentanyl 25μg)

Short onset time

Duration of action: 50~70mins
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Combined Spinal-Epidural Anesthesia(CSEA)

Immediate onset of analgesia by spinal anesthesia
 After giving spinal anesthesia , an epidural catheter is placed immediately prior the surgery

Drug can be re-injected according to the need during the surgery

Most common used in cesarean section delivery
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Puncture the spinal needle, fluid from the subarachnoid space
Inject 0.5%bupivacaine
Inject
1.5%lidocaine 23

General considerations:
1) Sensory level up to T
6 is required for cesarean section
2) Dose reduction is required due to decreased epidural and subarachnoid space.
3) Left lateral tilt should be maintained to prevent supine hypotension syndrome.
4) If there is significant fetal distress, general anesthesia must be opted since regional anesthesia takes time, esp. epidural anesthesia.
5) Onset of epidural takes time (15-20 mins) so reserved for elective cases only or for condition like PIH.
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
Risk of pulmonary aspiration is bypassed.

Effect of anesthetic drugs on fetus is not seen.

Awake mother can interact with her newborn immediately.
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
Hypotension :There can be significant hypotension with spinal(less with epidural) anesthesia.
Treatment for hypotension:-

Preloading the patient with 500ml-1000ml of Ringer’s lactate

Left lateral position

Oxygen given by face mask .

Ephedrine 5~10mg iv to sustain a mild vasopressor effect.
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
Nausea and vomiting
Due to rapid onset of hypotension and parasympathetic stimulation of the gastrointestinal tract
Treatment:-

Antiemetics: Inj Ondansetrone 4 mg iv

Fluid

Bradycardia
Treatment:-
Inj.Atropine or Inj.Glycopyrrolate
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
Postdural puncture headache(PDPH)
Due to leakage of cerebrospinal fluid through the needle hole in the Dura
Treatment:-

Use a small-caliber needles (25G)
 Recumbent position (bed sore)
 Hydration
 sedation
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
Time taken is more than General Anesthesia , so not ideal for fetal distress.

Difficulty in controlling sensory level with spinal anesthesia( chance of high spinal is more in parturient)

Cardiopulmonary arrest

Inadvertent intravascular injection of local anesthetic (toxic reaction) or intrathecal injection of anesthetic (total spinal)

The pregnant patient is more likely to have an intravascular drug injection because of the venous distention in the epidural space

Injection of the drug into a highly vascularized area will result in rapid systemic absorption
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
Cardiopulmonary arrest(contd..)
Full cardiopulmonary resuscitation (CRR) is indicated
(establish a patent airway, intubate the trachea, O
2 supply,give vasopressors, treat arrhythmias, provide external cardiac massage)
Then, immediate cesarean section delivery to savage fetus.
2020/4/15 30


Maximum doses of local anesthetics used in obstetrics
Lidocaine: 5 mg/kg
Bupivacaine: 1.5 mg/kg
Ropivacaine: 3.0 mg/kg

Add epinephrine (1:200,000) to produce local vasoconstriction: prevent too-rapid absorption and prolong the anesthetic effect.
2020/4/15 31


If manifested by central nerve system toxicity
(convulsion):
Recognize the prodromal sings: ringing in the ears, diplopia, perioral numbness, slurred speech

100 % Oxygen supply
 protect the patient’s airway

Inject: thiopental 50mg, midazolam 1~2mg
2020/4/15 32


Well suited to obstetric anesthesia: vaginal delivery, or cesarean surgery

After evaluation of patient, Epidural catheter is placed once labor is established.

The catheter can be used for surgery and postoperative analgesia

Satisfactory results of analgesia

The fetal outcome is not adversely affected
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Procedure: After putting the patient in sitting or left lateral position. puncture sites:L2~3, L3~4
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2020/4/15 35

i. Inject 3ml of a 1.5%
Lidocaine as a test dose . If spinal anesthesia dose not result after 5~10min, inject an additional 5ml .In total
10ml of anesthetic solution is given to accomplish an adequate level of anesthesia.
ii. Continuous infusion
0.125%~0.25% of
Bupivacaine
10~12ml/hr with
Fentanyl 2~5μg/ml in the epidural mixture
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
An epidural block approached through the caudal space

Seldom used
Hard to perform (the landmarks of the sacral hiatus is obscured , and the fetus might be injured by the needle )
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
Usually considered for fetal distress or if contraindication to regional anesthesia-Coagulopathy, infection (at site for spinal), hypovolemia, moderate to severe vulvular stenosis, progressive neurologic disease

Due to high chances to aspiration, prophylaxis should be taken.
 Intubation with Sellick’s maneuver (cricoid pressure).IPPV with bag and mask avoided
2020/4/15 38


Difficult intubation should be anticipated and ready for management.

Patient should be nursed in left tilt position.

All drugs should be given in minimal doses as all drugs crosses the placenta and attain equilibrium between mother and fetus in 10~15 mins.
2020/4/15 39


Be prepared with antacid

Preoxygenation: Give 100% oxygen with a close-fitting mask for 5~6min
 Patient’s abdomen is surgical scrubbed (disinfection) and draped for surgery (anesthetics act on the fetus ↓)
 Induction: Thiopental 2-5mg/kg iv or Ketamine 1-2mg/kg

Muscle relaxant: Succinylcholine 1.5 mg/kg
 Endotracheal intubation with Sellick’s maneuver
2020/4/15 40


Maintenance: 50% Nitrous oxide, 50% oxygen,
(0.5%)halothane or 0.75% isoflurane or 1% Sevoflurane.All inhalational agents relax the uterus and may cause Postpartum
Hemorrhage(PPH).So, low concentration to be used.
Induction to delivery time under 10 mins …..fast!!!

After delivery of the fetus ,the nitrous oxide concentration may be increase to 70%, intravenous narcotics and benzodiazepines injected for supplemental anesthesia
2020/4/15 41


If an epidural block is in place, no further analgesia will be required (forceps?)

General anesthesia is acceptable
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
Fetus development of bradycardia and appearance of meconium

Uterine perfusion is correlated with BP. Hypotension will aggravate fetal distress

Regional anesthesia can cause hypotension , so usually contraindicated if fetal distress exist.

GA might be required for speedy delivery.

Neonatal resuscitation is needed .
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
Composed of hypertension, generalized edema, and proteinuria.

The primary pathologic characteristics is generalized arterial spasm

Regional and general anesthesia are used

Contraindications to regional anesthesia include coagulopathy, urgency for fetal distress
2020/4/15 44


If coagulation profile is normal epidural anesthesia is anesthesia of choice because:

These patients can manifest severe, uncontrollable hypotension with Spinal anesthesia( hypertensives are more prone to hypotension after Spinal).
 Intubation may be very difficult due to laryngeal edema.
2020/4/15 45


If coagulation profile is abnormal GA should be administered.

Extra considerations besides the protocol for C/S to be taken in case of PIH which are:

Intubation to be done by expert hands with minimum trauma

Attenuation of cardiovascular response to intubation to be blunted, otherwise intracranial hemorrhage can occur.

These patients are on Magnesium which potentiates the action of non-depolarizing muscle relaxants(NDMR).so, dose of NDMR should be reduced.

Patients with PIH have decreased levels of cholinesterase, prolonging the effect of succinylcholine
2020/4/15 46


Patient presenting with hypertension, generalized edema, proteinuria and seizure.

Induction should be done with thiopentone(anticonvulsant activity) and followed by GA protocols same as PIH

Placenta previa and aruptio placenta are accompanied by serious maternal hemorrhage.
 Treatment of shock must be formulated.

Ketamine can support BP for induction

Regional block is contraindicated in the presence of hypovolemia
2020/4/15 47


Elective surgeries should be deferred until delivery

Urgent surgeries should be done during second trimester.

First trimester high chances of abortion and congenital abnormalities.

Third trimester high chance of preterm labor

Only Emergency surgeries should be taken in first and third trimester.
2020/4/15 48


If possible surgery to be performed under local/ regional anesthesia.

Avoid GA as much as possible.

If GA must be opted ,do not use nitrous oxide. minimum use of inhalational and intravenous agents.

If Spinal anesthesia is to be given, avoid hypotension.
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