General Anesthesia for Cesarean Section.ppt

7/30/2019 General Anesthesia for Cesarean Section.ppt

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General Anesthesia forCesarean Section

Husong Li, M.D., Ph.D.

Assistant Professor

Department of AnesthesiologyUniversity of Texas Medical Branch at Galveston, Texas


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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.


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Indications for General Anesthesia

Fetal distress

Significant coagulopathy

Acute maternal hypovolemia andHomodynamic instability

Sepsis or local skin infection

failed regional anesthesia

Maternal refusal of regional anesthesia


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Preoperative Preparation for

General Anesthesia

History & Examination, LABs

Airway evaluation

Aspiration prophylaxis

Basic machine and monitor preparation


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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


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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. BrJ. Anesth 1996; 76: 680-684)

Sniffing position


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Airway evaluation

Moderate head

elevation, extension of

atlanto-occipital, and

flexion of the lower

portion of the cervical

spine

sniffing position


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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


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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


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Factors increase the risk of

aspiration Decrease in gastric and intestinal motility

delayed gastric emptying by anxiety andpain

Relaxation of lower esophageal sphinctertone

Increase in abdominal pressure

Increase gastric acid secretion

Patients not fasting


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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


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Prevention of Aspiration

Cricoid pressure

Adequate oxygenation of patient

Treat hypotension promptly

Efficient and timely intubation

Orogastric or nasogastric tubeAwake extubation


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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


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IntraoperativeManagement of

Parturient

Positioning

Oxygenation Monitors

Induction of general anesthesia

Maintenance of general anesthesia Emergence from general anesthesia


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IntraoperativeManagement-

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


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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%

O2O2 saturation drops faster during apnea

(increase VO2 and decrease FRC)


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MonitorsPulse oximeter probe

Right size BP cuffElectrocardiographic electrodes

capnograph

Temperature monitor readily available

Urinary output


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IntraoperativeManagement

Communicate with surgeons and nursingstaffs while pt is prepared and draped for

surgery

Final check for your READINESS FOR

INDUCTION of general anesthesia


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Induction of general anesthesia

Rapid sequence induction

Cricoid pressure maintained untilendotracheal tube cuff inflated and tubeplacement confirmed

Agents:Thiopental/Ketamine/Propofol/Etomidate/Succinylcholine


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Induction Agents-Thiopental

Thiopental (STP) 2-5 mg/kg IV Fast and reliable

Negative inotrope and vasodilator

Cross placenta; STP concentration rarelyexceed the threshold for fetal depression

with dose less than 4 mg/kg

No evidence of adverse effect of STP onfetus even the induction-to-delivery (ID)

interval is prolonged; keep incision to

delivery time less than 4-7 minutes


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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 at1 hour after delivery comparing with STP, but

similar neurobehavioral scores by 4 hours after

delivery (Celleno D. Br J Anesth 1989; 62:649-54)


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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)


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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 siteMyoclonus


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Induction Agents-Succinylcholine

Succinylcholine (SUX) 0.3 to 1.5mg/kg IV

Spontaneous ventilation may resume in

2-3 minutes with low dose SUX (0.3-0.5 mg/kg), but peak time delayed byabout 10-15 seconds

3rd line of defense of difficult airwayRecovery from intubation dose of SUX

is unchanged in the pregnant patients


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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


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Maintenance of General

Anesthesia

Succinylcholine bolus when needed

Nondepolarizing agents accordingly ie.Nimbex, Vecuronium, Rocutonium.

*Oxytocin 10-40 U IV infusion

*Antibiotics of choice


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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


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Awareness during General

Anesthesia

High incidence between induction ofanesthesia and delivery of the fetus

Administration of only 50% N2O inoxygen 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)


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Awareness during General

Anesthesia

Ketamine or combine ketamine andthiopental for induction

Minimize of induction to deliveryinterval

50%N2O/O2 with following AGENTS

reduce awareness to less than 1 % 0.6% isoflurane

1% sevoflurane

3% desflurane


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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 & Gynecol1981; 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 acidoticblood gas

Ultimate neonatal outcome? (Ong BY. Et al Anesth Analg 1998;68:270-5)


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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


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Factors Cause Uterine Artery

SpasmUterine incision

Contraction of myometrial musclesVasoconstrictors: prostaglandin

released from fetus and placenta

Maternal catecholamine release


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Post Anesthesia Care

Transport to PACU with O2

Hypoxemia: airway obstruction and

hypoventilationHypotension

Pain control

Nausea and Vomiting

Shivering and hypothermia

General Anesthesia for Cesarean Section.ppt

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