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General Anesthesia for Cesarean Section

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General Anesthesia for Cesarean Section Husong Li, M.D., Ph.D. Assistant Professor Department of Anesthesiology University of Texas Medical Branch at Galveston, Texas – PowerPoint PPT presentation

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Title: General Anesthesia for Cesarean Section


1
General Anesthesia for Cesarean Section
  • Husong Li, M.D., Ph.D.
  • Assistant Professor
  • Department of Anesthesiology
  • University of Texas Medical Branch at Galveston,
    Texas

2
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.

3
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

4
Preoperative Preparation for General Anesthesia
  • History Examination, LABs
  • Airway evaluation
  • Aspiration prophylaxis
  • Basic machine and monitor preparation

5
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

6
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

7
Airway evaluation
sniffing position
Moderate head elevation, extension of
atlanto-occipital, and flexion of the lower
portion of the cervical spine
8
Preparation and Prevention
  • 2-3 different blades, ie MAC 34 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

9
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

10
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

11
Prevention of Aspiration-Pharmacological 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

12
Prevention of Aspiration
  • Cricoid pressure
  • Adequate oxygenation of patient
  • Treat hypotension promptly
  • Efficient and timely intubation
  • Orogastric or nasogastric tube
  • Awake extubation

13
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

14
Intraoperative Management of Parturient
  • Positioning
  • Oxygenation
  • Monitors
  • Induction of general anesthesia
  • Maintenance of general anesthesia
  • Emergence from general anesthesia

15
Intraoperative Management-Positioning
  • 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

16
Intraoperative Management-Denitrogenation
  • 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)

17
Intraoperative Management-Monitors
  • Pulse oximeter probe
  • Right size BP cuff
  • Electrocardiographic electrodes
  • capnograph
  • Temperature monitor readily available
  • Urinary output

18
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

19
Induction of general anesthesia
  • Rapid sequence induction
  • Cricoid pressure maintained until endotracheal
    tube cuff inflated and tube placement confirmed
  • AgentsThiopental/Ketamine/Propofol/Etomidate/Succ
    inylcholine

20
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

21
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 62649-54)

22
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)

23
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

24
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 (0.3-0.5 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

25
Maintenance of General Anesthesia
  • PREDELIVEY
  • 50 O2/50N2O/0.5 Isoflurane
  • 100 O2/1-1.5 Isoflurane
  • POSTDELIVERY
  • 50-70 N2O/30-50O2/
  • 0.5 Isoflurane/Narcotics
  • Minimize volatile agents to prevent postpartum
    hemorrhage 0.5 MAC does not significantly
    increase maternal blood loss

26
Maintenance of General Anesthesia
  • Succinylcholine bolus when needed
  • Nondepolarizing agents accordingly ie. Nimbex,
    Vecuronium, Rocutonium.
  • Oxytocin 10-40 U IV infusion
  • Antibiotics of choice

27
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

28
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
    62516-20 Crawford JS Br J anesth 1971
    43179-82 Abboud TK et al Acta Anesthesiol Scand
    1985 29 663-8)

29
Awareness during General Anesthesia
  • Ketamine or combine ketamine and thiopental for
    induction
  • Minimize of induction to delivery interval
  • 50N2O/O2 with following AGENTS reduce awareness
    to less than 1
  • 0.6 isoflurane
  • 1 sevoflurane
  • 3 desflurane

30
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 58331-335. Crawford JS. Et al.
    Br J. Anesth 1973 45726-732)
  • 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 68270-5)

31
Ong BY. et al Anesth Analg 1998 68270-5
  • 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

32
Factors Cause Uterine Artery Spasm
  • Uterine incision
  • Contraction of myometrial muscles
  • Vasoconstrictors prostaglandin released from
    fetus and placenta
  • Maternal catecholamine release

33
Post Anesthesia Care
  • Transport to PACU with O2
  • Hypoxemia airway obstruction and
    hypoventilation
  • Hypotension
  • Pain control
  • Nausea and Vomiting
  • Shivering and hypothermia
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