ANESTHESIA FOR CESAREAN SECTION

Krzysztof M. Kuczkowski, M.D

Course : 4

Year : 2009

Language : English

Country : Moldova

City : Chisinau

Weight : 1351 kb

Related text : nohttp://www.euroviane.net

ANESTHESIA FOR

CESAREAN SECTION

Texas Tech University Health Sciences Center at El Paso, Paul L. Foster School of Medicine, El Paso, Texas, USA

Cesarean section

• Choice of anesthesia: spinal (SAB), epidural (CLE), combined spinal epidural (CSE), general endotracheal (GETA)

• When compared to regional techniques, general anesthesia can be administered with shorter induction-to-delivery time

• However, the literature suggests that a greater number of maternal deaths occur when general anesthesia is administered

Cesarean section

• The literature indicates that a larger proportion of

neonates in the GA groups, compared to those in

the RA groups, are assigned Apgar scores of less

than 7 at 1 and 5 min

• The decision to use a particular anesthetic

technique should be individualized

• Resources for the treatment of complications

should be available

Neuraxial blocks

Obstetric analgesia & anesthesia

Single dose spinal (SAB)

Obstetric analgesia & anesthesia

Epidural (CLE)

Obstetric analgesia & anesthesia

Combined spinal epidural (CSE)

The technique: CSE versus CLE

CSE: special needle design

Regional versus general anesthesia

General anesthesia

Monitoring

Monitoring

• The overall goal of anesthetic management of a pregnant woman undergoing Cesarean section is to maintain the mother and her fetus (until the umbilical cord is severed) in the best possible physiologic

condition J Clin Anesth 2006

• This requires that we effectively monitor the mother

and the fetus in the perioperative period J Clin Anesth 2006

Monitoring

1. Blood pressure (non-invasive & invasive)

2. Heart rate

3. Respiratory rate

4. Electrocardiogram

5. Oxygen saturation

6. End tidal carbon dioxide

7. Fetal heart rate

Monitoring

• The FHR monitoring is useful at identifying intraoperative conditions leading to impaired uteroplacental blood flow and fetal oxygenation prior to delivery

• A normal FHR is between 120 - 160 beats per minute with 3-7 beats variability

• Variability is decreased by hypoxia and by sedative

and other drugs of anesthesia

Premedication

Premedication

• The goals of “routine” preanesthetic medications

typically are as follows;

– first, to dry secretions

– second, to prevent vagal activity

– third, to provide anxiolysis

– fourth, to ensure analgesia for uncomfortable

anesthetic procedures (e.g., arterial line placement

prior to induction of anesthesia)

– and fifth, to provide a basal level of analgesia for

surgery

Premedication

• Sedative drugs are usually avoided in pregnancy, and

verbal reassurance may often suffice for the patient

undergoing Cesarean section under general

• In selected cases, it is not unreasonable to administer

an anticholinergic agent, which decreases secretions

and lessens the likelihood of bradycardia during

anesthesia

Premedication

• Atropine readily crosses the placenta and results in an

increased FHR, with decreased beat-to-beat

variability

• In contrast, glycopyrrolate does not readily cross the

placenta, and it is the anticholinergic agent of choice

• Unfortunately, the anticholinergic agents result in

decreased lower esophageal sphincter tone

Premedication

• When anticholinergic agent is indicated, glycopyrrolate

may be given intramuscularly 30-60 minutes before the

induction of anesthesia or intravenously just before the

administration of anesthesia

Premedication

• Metoclopramide is a procainamide derivative that is a cholinergic agonist peripherally and a dopamine receptor antagonist centrally

• A 10-mg intravenous dose of metoclopramide increases lower esophageal sphincter tone has an antiemetic effect and reduces gastric volume by increasing gastric peristalsis

Premedication

• Metoclopramide can have a significant effect on gastric volume in as little as 15 minutes

• Metoclopramide crosses the placenta, but studies have

reported no significant effects on the fetus Expert Opin Drug Saf 2006

Premedication

• The parturient should also receive 30 ml of sodium bicitrate orally prior to induction of general anesthesia for Cesarean section [to reduce gastric

acidity] Expert Opin Drug Saf 2006

Drugs of anesthesia

Drugs of anesthesia

• Although the overall use of general anesthesia has

been steadily declining in obstetric patients, in selected

cases [e.g., an emergent Cesarean section], it may still

be preferred, indicated and/or necessary Anesth Analg 1997/Expert

Opin Drug Saf 2006

• The following section reviews the drugs most

commonly employed for administration of general

anesthesia in pregnant women

Drugs of anesthesia

• Potent inhalational halogenated agents

• Nitrous oxide

• Opioid receptor agonists

• Intravenous induction agents

– Propofol

– Barbiturates

– Ketamine

– Etomidate

• Neuromuscular blocking drugs

– Succinylcholine

– Rocuronium

– Vecuronium

– Atracurium

Potent inhalational agents

• Potent inhalational halogenated agents in adults are

administered for the maintenance phase of general

anesthesia

• Those in use today include sevoflurane, isoflurane

and desflurane

• Potent inhalational halogenated agents affect the fetus

– indirectly by causing maternal hypotension and/or hypoxia

– directly by depressing the fetal CV or CNS Expert Opin Drug Saf 2006

Potent inhalational agents

• Studies in an animal model have shown minimal

maternal and fetal effects with administration of

moderate (e.g., 0.75-1.0 MAC) concentration of

volatile halogenated agents Expert Opin Drug Saf 2006

Nitrous oxide

• Uptake and elimination of nitrous oxide are rapid, as

a result of its low blood-gas partition coefficient

• It produces some analgesia, and in concentrations

greater than 60% may produce amnesia Expert Opin Drug Saf 2006

Nitrous oxide

• Because of its high solubility nitrous oxide may diffuse into the cuff of an endotracheal tube and lead to a marked increase in cuff pressure, which could result in significant airway management complications (e.g., high cuff pressure-related ischemia of the tracheal mucosa) Acta Anaesthesiol Scand 2004

• This may be particularly important in pregnant patients because of physiological changes of pregnancy, which include narrowing of the airway secondary to edema Expert Opin Drug Saf 2006

Opioid receptor agonists

• Fentanyl, sufentanil, alfentanil, remifentanil are the

most popular opioids used in the practice of obstetric

anesthesia when general anesthesia is necessary

• Their primary effect is analgesia Expert Opin Drug Saf 2006

• Opioids and induction agents decrease the FHR

variability and cause fetal depression; possibly to a

greater extent than the inhalational agents

Intravenous induction agents

• When choosing an induction agent for general

anesthesia, the primary goals are as follows:

– First, to preserve maternal BP, CO, and uterine blood flow;

– Second, to minimize fetal depression;

– Third, to ensure maternal hypnosis and amnesia Expert Opin Drug

Saf 2006

Intravenous induction agents

• Propofol

• Barbiturates

• Ketamine

• Etomidate

Propofol

• Propofol = rapid, smooth induction of anesthesia

• It has no analgesic properties

• The drug produces dose-dependent decreases in

cardiac output and arterial blood pressure

• Decreased BP results in decreased uteroplacental

perfusion Expert Opin Drug Saf 2006

Propofol

• Propofol is a lipophilic agent with a low

molecular weight, and it rapidly crosses the

placenta Expert Opin Drug Saf 2006

• Propofol blunts the hypertensive response to

laryngoscopy and intubation more effectively than

the other induction agents

Barbiturates

• Thiopental is the barbiturate commonly used for induction of anesthesia in obstetrics

• It is very short-acting and produces unconsciousness in one arm-to-brain circulation time (30 seconds)

• Thiopental decreases arterial BP and CO in a dose dependent manner Expert Opin Drug Saf 2006

Barbiturates

• Thiopental rapidly crosses the placenta, and it can

be detected in umbilical venous blood within 30

seconds of administration

• The umbilical venous blood concentration peaks

in 1 minute Expert Opin Drug Saf 2006

Ketamine

• Ketamine is a very useful induction agent in obstetric patients

• It produces unconsciousness in 30-60 seconds after intravenous induction dose, which may last for 15-20 minutes Expert Opin Drug Saf 2006

• Ketamine has a rapid onset of action, it provides both analgesia and hypnosis, and it reliably provides amnesia

Ketamine

• In addition, its sympathomimetic properties are

advantageous in patients with asthma or modest

hypovolemia Expert Opin Drug Saf 2006

• Ketamine rapidly crosses the placenta, and it

reaches a maximum concentration in the fetus

approximately 1-2 minutes after administration

Etomidate

• Etomidate is an intravenous induction agent that

has been used in obstetric anesthesia practice

since 1979

• Etomidate produces a rapid onset of anesthesia in

one arm-to-brain circulation time Expert Opin Drug Saf 2006

• It undergoes rapid hydrolysis, which results in a

rapid recovery period

Etomidate

• Etomidate causes little cardiovascular depression;

thus it is an excellent choice in patients with

hemodynamic instability

• Intravenous injection of etomidate may result in

pain and myoclonus Expert Opin Drug Saf 2006

Neuromuscular blocking drugs

• Succinylcholine

• Rocuronium

• Vecuronium

Neuromuscular blocking drugs

• A small dose of a nondepolarizing muscle relaxant may be given 3 to 5 minutes before induction of general anesthesia to prevent fasciculations after the administration of succinylcholine

• Alternatively, this small dose may serve as a priming dose if a nondepolarizing agent will be used to achieve muscle relaxation Expert Opin Drug Saf 2006

Succinylcholine

• The depolarizing agent succinylcholine remains

the muscle relaxant of choice for the obstetric

patient

• The standard intubating dose provides complete

muscle relaxation and optimal conditions for

laryngoscopy and intubation within approximately

45 seconds of i.v. administration Expert Opin Drug Saf 2006

Succinylcholine

• Succinylcholine is highly ionized and water

soluble and only small amounts cross the placenta

• Maternal administration of succinylcholine rarely

affects fetal neuromuscular function Expert Opin Drug Saf 2006

Rocuronium

• Rocuronium is a suitable alternative to

succinylcholine when a nondepolarizing agent is

preferred for rapid sequence induction of general

anesthesia

• What dose?

Rocuronium

• Only very small amounts of the nondepolarizing

muscle relaxants cross the placenta; thus the fetus

rarely is affected

Summary

Take home message

“The position of woman in any civilization is an index of the advancement of that civilization; the position of woman is gauged best by the care given her at the birth of her child.”

Haggard HW, New York, 1929.

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