8/8/2019 OB trans 11

1/2

Page 1 of2

S2 Lec 3 (1 of 2): Anesthesia by Dra. Alicia Bautista AAAuuuggguuusssttt 222333,,, 222000111000

ANESTHESIA

Physiological Changes during Pregnancy with Major Clinical

Anesthetic ImplicationA. Cardiovascular System

1. Increased Cardiac Output produces hyperdynamic state incworkloadpredisposes to functional murmur

Healthy female can tolerate the hyperdynamic state Gravid with heart disease inc workload precipitate

pulmonary congestion especially during labor toimmediately postpartum inc CO maximal

Provide effective analgesia continuous lumbar epiduralanalgesia

2. Increased blood volume Inc in plasma blood volume

40-50% inc plasma volume15-20% inc red cell volume

Physiologic anemiaDouble-edged sword Inc clotting factor protects patient from blood loss and

renders her hypercoagulable inc risk of thromboticevents

After delivery ask patient to ambulate

3. Aortocaval syndrome Supine position uterus is compressed against the

vertebral column impaired venous return bradycardia

and decrease BP SUPINE HYPOTENSIVE POSITION

Results from a drop in venous return for which CVScannot compensate

Sympathetic blockade due to spinal or epiduralanesthesia will interfere with the mechanism tocompensate for aortocaval compression profoundhypotension

At risk for aortocaval compression are those withlarge uterus (multiple gestation, polyhydramnios,DM)

B. Respiratory System1.

Upper airway

Generalized peripheral edema Increase vascularity of the respiratory tract mucosa Capillaries engorged In labor, airway is edematous with voluntary and

involuntary valsalva maneuver Preeclampsia

irway edematous + friable bleedingdifficulty intubation should be considered

2. Respiratory Mechanism Enlarging uterus produces upward displacement of diaphragm dec FRC 15% (thus induction of inhalation anesthesia is

faster) Dec inhalation anesthesia required Dec FRC + inc O2 consumption = predisposes the parturient to

limited o2 reserve rapid development of hypoxemia +hypercarbia during periods of apnea

C. Gastrointestinal Inc progesterone dec gastric motility, dec food absorption Inc gastrin level (of placental origin) more acidic gastric

content Enlarged uterus inc intragastric pressure dec normal

oblique angle in the gastroesophageal junction Pregnant patient should always be considered to have a full

stomach irrespective of time of last meal. Why? Gastric

emptying decreases so be very particular of last intake of yourpatient

General anesthesia should always be avoided when possibleas they are at risk for aspiration of gastric contents

Pain Mechanism in Labor

1. Pain during 1st stage laborArises from uterus and adnexae during contraction Mediated by T10-L1 spinal segment Visceral in nature Characteristics: dull, diffuse, periodic and build peaks

2. Pain during 2ndstage labor Results from distention of birth canal, vulva and perineum Mediated by afferent fibers of posterior roots ofS2-S4 nerve Somatic in character: well localized, sharp and definitive,

often constant*sabi ni docS.S.S. (Second stage, S2-S4)

Methods of Pain Relief

1. Non-pharmacologica. Childbirth education

i. Lamazeb. Mind-body intervention

i.

Hypnosisii. Biofeedbackiii. Music therapy

c. Bioelectromagneticsi. Transcutaneous nerve stimulation

d. Intracutaneous nerve stimulationi. Sterile water blocksii. Acupuncture

e. Manual healingi. Therapeutic pouchii. Massage therapyiii. Muscle tension release

I

J

IJ

J

J

J

l

i

l

li

.

J

i

8/8/2019 OB trans 11

2/2

Page 2 of2

iv. Reflexologyv. Acupressure systemsvi. hydrotherapy

f. Herbal medicinei. Herbal cocktailsii. Aromatherapy

2. Pharmacologic methodsa.Systemic

i. Opioidsthe more lipid soluble is, the more freely it can

pass through and are associated with risk ofneonatal respiratory depression andneurobehavioral changes

ii. Sedative and/or tranquilizersPhenothiazinesBenzodiazepins

iii. Dissociative medications - ketamineiv. Barbituratesv. Propofolvi. Inhalational

causes dose-dependent relaxation of uterinesmooth muscle

high dose relaxes the uterus

b.RegionalPeripheral Blocks for Labor Analgesia

i. Perineal InfiltrationMost common local anesthetic technique

for vaginal delivery, mainly for episiotomyand repair

Lidocaine 5-10cc

ii. Pudendal nerve blockInvolves injection of total 7-10 mL each local

anesthetic into the right and left pudendalnerve as it passes medially to and posterior tothe ischial spine in each side of the pelvis

Goal: to block the pudendal nerve distal to itsformation by the anterior division of S2-S4 butproximal to its division into its terminalbranches

Adequate for spontaneous delivery and outletforceps delivery

Lidocaine

iii. Paracervical block

Blocks impulses from uterine body and cervixAim: block transmission through the

paracervical ganglion (FrankenhausersGanglion) which lies immediately lateral andposterior to the cervicouterine junction

Lidocaine injected to the cervix laterally 3 and9 oclock position

Complication: fetal bradycardia

iv. Neuraxial

SpinalEpiduralCombined spinal-epidural

Saddle blockModified spinal blockAffects only the sacral segmentIdeal for completion of 2nd stage labor

ANESTHESIA FOR CAESARIAN SECTION

Regional Anesthesia

Preferred technique because mother remains awake and is able tobond with her newborn upon delivery

2 most common regional techniques:

Spinal or Subarachnoid anesthesia More commonly used in the Philippines during CSdelivery

Simpler, more reliable with lesser chances of failure,faster onset of action, requires lesser drug dosagethus minimizing the risks of local anesthetic toxicityand drug transfer to the fetus

Hypotension: most common side effect(Tx: uterine displacement, IV hydration, ephedrine)

Other complications: spinal headache, high spinalblock and failed regional block

Epidural anesthesia Less severity and incidence of hypotension It avoids dural puncture which may diminish the

incidence of spinal headache With epidural catheter in place duration of anesthesia

can be prolong Requires high drug doses, delayed onset of action

prone to patchy or incomplete blockade Gold Standard: for pain relief during ALL stage of

labor

Absolute contraindications: Refractory maternal hypotension Maternal coagulopathy Treatment with once daily dose of low molecular weight

heparin within 12 hrs Untreated bacteremia

Skin infection over site of needle placement Increased in the intracranial pressure caused by masslesion

The Choice of Anesthetic Technique

- depends on three important factors:1. indication of pain relief2. condition of mother and baby3. skill of the anesthesiologist

Brought to you by: OBwan-Kenobi(RPE-JCF-PF-SAH)

With OBwan-Kenobi, everyone can OB :D