General Anesthesia for
Cesarean Section
Husong Li, M.D., Ph.D.
Assistant Professor
Department of Anesthesiology
University of Texas Medical Branch at Galveston, Texas
Introduction

Cesarean-section (CS) deliveries have accounted for
nearly 1 million of approximately 4 million annual
deliveries in US.
 Approximately 15% of CS was performed under
general anesthesia in US (Anesthesiology Hawkins,
JL 1997). Majority of CS were done under urgent or
emergent situations.
 In 2000, CS rate is about 22% in US, and 31.8% in
UTMB.
Indications for General Anesthesia

Fetal distress
 Significant coagulopathy
 Acute maternal hypovolemia and
Homodynamic instability
 Sepsis or local skin infection
 failed regional anesthesia
 Maternal refusal of regional anesthesia
Preoperative Preparation for
General Anesthesia
 History
& Examination, LABs
 Airway evaluation
 Aspiration prophylaxis
 Basic machine and monitor preparation
Factors may complicate
endotracheal intubations

Weight gain
 Oropharynx edema
 Enlarged breasts
 Obesity with short neck
 Full dentition
 Mallampati IV and mamdibular recession
 History of difficult airway
Airway evaluation

Anticipation of difficult endotracheal
intubation (1 in 300 in OB and 1 in 2000 all
patients)
 Thorough examination of neck, mandible,
dentition, and Oropharynx
 Training and experience (Hawthorne L. Br
J. Anesth 1996; 76: 680-684)
 Sniffing position
Airway evaluation
sniffing position
Moderate head
elevation, extension of
atlanto-occipital, and
flexion of the lower
portion of the cervical
spine
Preparation and Prevention

2-3 different blades, ie MAC 3&4 Miller 2
 6 to 7 mm ETT tubes with stylets
 LMAs sizes 3 and 4
 Emergency airway cart ready in the OR
 Fiberoptic bronchoscope
 Possible surgical airway equipment
Aspiration prophylaxis

Pulmonary aspiration: 1 in 400-500 in OB
versus 1 in 2000 in all surgical patients
 No agent or combination of agents can
guarantee that a parturient will not aspirate
or develop pneumonitis following failed
intubations
Factors increase the risk of
aspiration

Decrease in gastric and intestinal motility
 delayed gastric emptying by anxiety and
pain
 Relaxation of lower esophageal sphincter
tone
 Increase in abdominal pressure
 Increase gastric acid secretion
 Patients not fasting
Prevention of AspirationPharmacological agents

PO 30 ml 0.3 M sodium citrate 15-30
minute prior to induction
 H2 blocker, ranitidine 50 mg IV
 Metoclopramide 10 mg IV, at least 5
minute prior to induction
 Omeprazole 40 mg the night before and the
AM of surgery for high risk patients
 Ondansetron 4-8 mg IV
Prevention of Aspiration
 Cricoid
pressure
 Adequate oxygenation of patient
 Treat hypotension promptly
 Efficient and timely intubation
 Orogastric or nasogastric tube
 Awake extubation
Basic Machine and Monitor
Preparation

Monitors: esp. capnograph
 Suction tubing functional
 Airway equipments ready and functional
 LMAs: 2nd line of defense of difficult
airway
 Others: ie. meds
Intraoperative Management of
Parturient

Positioning
 Oxygenation
 Monitors
 Induction of general anesthesia
 Maintenance of general anesthesia
 Emergence from general anesthesia
Intraoperative ManagementPositioning

OR bed should be allowing trendelenburg
and reversed positions
 Sniffing position
 Patients in supine position with a wedge
under the right hip
 Head and back up position if preparing
awake fiberoptic intubation
Intraoperative ManagementDenitrogenation
 Denitrogenation
with O2 as soon as
patient on OR bed
 Seal mask to achieve 100% O2
 3-5 minutes or 4 VC breaths of 100%
O2
 O2 saturation drops faster during apnea
(increase VO2 and decrease FRC)
Intraoperative ManagementMonitors
 Pulse
oximeter probe
 Right size BP cuff
 Electrocardiographic electrodes
 capnograph
 Temperature monitor readily available
 Urinary output
Intraoperative Management

Communicate with surgeons and nursing
staffs while pt is prepared and draped for
surgery

Final check for your READINESS FOR
INDUCTION of general anesthesia
Induction of general anesthesia
 Rapid
sequence induction
 Cricoid pressure maintained until
endotracheal tube cuff inflated and tube
placement confirmed
 Agents:Thiopental/Ketamine/Propofol/
Etomidate/Succinylcholine
Induction Agents-Thiopental

Thiopental (STP) 2-5 mg/kg IV
 Fast and reliable
 Negative inotrope and vasodilator
 Cross placenta; STP concentration rarely
exceed the threshold for fetal depression
with dose less than 4 mg/kg
 No evidence of adverse effect of STP on
fetus even the induction-to-delivery (ID)
interval is prolonged; keep incision to
delivery time less than 4-7 minutes
Induction Agents-Propofol






Propofol 1-2.5 mg/kg IV
Rapid induction and rapid awakening
Negative inotrope and vasodilator
May inhibit oxytocin induced uterine contraction
Can be rapidly cleared from neonatal circulation
Dose greater than 2.8 mg/kg may result in lower
apgar scores and lower neurobehavioral scores at
1 hour after delivery comparing with STP, but
similar neurobehavioral scores by 4 hours after
delivery (Celleno D. Br J Anesth 1989; 62:649-54)
Induction Agents-Ketamine







Ketamine 1-2.0 mg/kg IV
Modest hemorrhage or parturient asthma
Provide rapid analgesia, hypnosis, and amnesia
May depress myocardium and reduce CO and BP
in severe hypovolemic patients
Avoid in hypertensive patients
More than 2 mg/kg may associate with fetal
depression
Maternal psychotropic profiles: dreaming,
dysphoria, hallucination during emergence
(benzodiazepine reduce the side effects)
Induction Agents-Etomidate
 Etomidate
0.2-0.3 mg/kg IV
 Cause little CV depression-for HD
unstable parturient
 Neonatal adrenal suppression?
 pain at injection site
 Myoclonus
Induction Agents-Succinylcholine
 Succinylcholine
(SUX) 0.3 to 1.5
mg/kg IV
 Spontaneous ventilation may resume in
2-3 minutes with low dose SUX (0.30.5 mg/kg), but peak time delayed by
about 10-15 seconds
 3rd line of defense of difficult airway
 Recovery from intubation dose of SUX
is unchanged in the pregnant patients
Maintenance of General
Anesthesia

PREDELIVEY
 50% O2/50%N2O/0.5% Isoflurane
 100% O2/1-1.5% Isoflurane
 POSTDELIVERY
 50-70% N2O/30-50%O2/
 0.5% Isoflurane/Narcotics
 Minimize volatile agents to prevent
postpartum hemorrhage; 0.5 MAC does not
significantly increase maternal blood loss
Maintenance of General
Anesthesia
 Succinylcholine
bolus when needed
 Nondepolarizing agents accordingly ie.
Nimbex, Vecuronium, Rocutonium.
 *Oxytocin 10-40 U IV infusion
 *Antibiotics of choice
Emergence from General
Anesthesia

Stomach emptied via an OG tube
 Upper airway suctioned
 Nondepolarizing agents reversed adequately
 Opioids for pain relief
 Extubation when patients regain protective
reflexes; are able to maintain airway;
respond appropriately to verbal commands;
and are hemodynamically stable
Awareness during General
Anesthesia
 High
incidence between induction of
anesthesia and delivery of the fetus
 Administration
of only 50% N2O in
oxygen without other agents results in
maternal awareness in 12-26% of cases
(Warren TM Anesth Analg 1983; 62:516-20; Crawford JS Br J anesth 1971; 43:179-82 Abboud TK
et al Acta Anesthesiol Scand 1985; 29: 663-8)
Awareness during General
Anesthesia
 Ketamine
or combine ketamine and
thiopental for induction
 Minimize of induction to delivery
interval
 50%N2O/O2 with following AGENTS
reduce awareness to less than 1 %
0.6% isoflurane
 1% sevoflurane
 3% desflurane

Fetus Consideration during
Emergency Cesarean Section

Decision to Incision or interval: 30 minutes?
 Uterine Incision to Delivery (UD) interval
should be less than 3 minutes (Datta et al Obstet & Gynecol
1981; 58:331-335. Crawford JS. Et al. Br J. Anesth 1973; 45:726-732)

Neonates delivered after 3 minutes following
uterine incision had lower apgar and acidotic
blood gas
 Ultimate neonatal outcome? (Ong BY. Et al Anesth Analg 1998;
68:270-5)
Ong BY. et al Anesth Analg 1998;
68:270-5
 Increase
incidence of low 1 minute apgar
scores in elective under GA
 Increase incidence of low 1 and 5 minutes
apgar scores in emergency under GA
 No different in ultimate neonatal outcome
Factors Cause Uterine Artery
Spasm
 Uterine
incision
 Contraction of myometrial muscles
 Vasoconstrictors: prostaglandin
released from fetus and placenta
 Maternal catecholamine release
Post Anesthesia Care
 Transport
to PACU with O2
 Hypoxemia: airway obstruction and
hypoventilation
 Hypotension
 Pain control
 Nausea and Vomiting

Shivering and hypothermia