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What the obstetrician needs to know about anesthesia

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Title: Obstetric Anesthesia What the obstetrician should know. Author: Tom Last modified by: tarcher Created Date: 2/14/2008 4:28:24 PM Document presentation format – PowerPoint PPT presentation

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Title: What the obstetrician needs to know about anesthesia


1
What the obstetrician needs to know about
anesthesia
  • Tom Archer, MD, MBA
  • Director, Obstetric Anesthesia UCSD
  • July 13, 2011

2
The black box of anesthesia Useful, but what
is it really all about?
ANESTHESIA
3
What ARE those men and women doing BEHIND THE
CURTAIN?
Pay no attention to the man behind the curtain
4
Anesthesia in one sentence
  • You can put the nervous system to sleep with all
    kinds of drugs, and the patient will do fine, as
    long as she keeps breathing.

5
Two more sentences
  • Most anesthesia drugs can interfere with
    breathing.
  • Anesthesia drugs can cause loss of consciousness,
    intended or unintended, and this can allow
    stomach contents to get into the lungs
    (aspiration).

6
Our drugs interfere with breathing
  • Narcotics decrease respiratory rate (to zero!)
  • Propofol, midazolam cause upper airway
    obstruction (tongue falls back and obstructs).
  • Severe hypotension causes medullary ischemia and
    apnea (commonest cause of respiratory arrest
    after spinal).
  • High spinal or epidural can paralyze phrenic
    nerve (less common).
  • Seizures due to local anesthetic toxicity
    interfere with breathing.

7
Our drugs allow aspiration
  • Loss of consciousness (LOC) is associated with
    loss of gag, swallow and cough
  • Any LOC can allow aspiration of regurgitated
    gastric contents

8
Now you understand what we do all day
  • Mess up nervous system
  • Keep patient breathing
  • Worry about stomach contents getting
  • into the lungs
  • The rest is details.

9
Two details
  • Anesthesia can make the blood pressure go down a
    lot. That is bad.
  • Sticking needles into the backs of people whose
    blood cant clot is not a good idea.

10
Anesthetic agents and uterus
  • Inhaled sevoflurane and desflurane relax uterus.
    This effect goes away fast (dont blame sevo for
    atony once patient is awake). N2O does not relax
    uterus.
  • IV and neuraxial anesthesia drugs (LA, narcotics,
    sedatives, hypnotics, propofol, etomidate,
    low-dose ketamine, etc.) have little to no direct
    effect on uterus.

11
Epidural test dose
  • Epidurals can cause seizures if local
    anesthetic goes into a vein.
  • This is one reason for the test dose.
  • Other reason is to detect intrathecal catheter
    and prevent high spinal.

12
Scenario 1 Elective Cesarean delivery a
uniquely social surgery
13
Lets teach our residents the proper approach to
a unique operation in a unique setting.
  • We are on stage (what we say, do, body
    language, staff interactions are closely observed
    and judged).
  • You know this. Our residents may not.
  • As anesthesiologists we may not be accustomed to
    awake patients, presence of family, etc. Help us
    when we forget.

14
Scenario 1 Elective C-section
  • Neuraxial anesthesia (NA, spinal or epidural) is
    good from multiple points of view
  • Mother experiences birth, protects her own
    airway, baby gets minimal drug exposure.
  • NA allows morphine to be given for post-op pain
    control.

15
Scenario 1 Elective C-section
  • NPO, famotidine (Pepcid), metoclopramide
    (Reglan), sodium citrate (Bicitra).
  • Despite attempts to empty stomach, we assume full
    stomach in pregnancy (decreased LES tone, delayed
    gastric emptying).

16
Routine after spinal/epidural
  • Left uterine displacement (how much is enough?).
  • Vasopressors to increase SVR and venous return
    (CO).
  • Decreased emphasis on IV fluid preloading than
    in the past.

17
One equation
  • (MAP - CVP) CO x SVR.
  • Remember Ohms Law? V IR.
  • Voltage Current x Resistance
  • CVP is small, so MAP CO x SVR, more or less.

18
Neuraxial anesthesia tends to decrease the MAP,
because it
  • Decreases tone of lt 0.1 mm diameter resistance
    arterioles (SVR), and
  • Dilates lower body capacitance veins which
    decreases venous return, and
  • Venous return Cardiac output.
  • And MAP SVR x CO!

19
Autonomic nervous system.
T1
L2
Sympathetics go to internal organs and to veins
and arterioles. Blocking sympathetics decreases
venous tone (CO) and arteriolar tone (SVR). Blood
pressure falls, vagal tone dominates and
bradycardia may occur, making situation even
worse.
20
Spinal / epidural causes sympathectomy dilation
of resistance arterioles and capacitance veins.
www.cvphysiology.com/Blood20Pressure/BP019.htm
21
38 y.o. female, repeat c/s, 420 , gestational
hypertension, continuous spinal fall in systemic
vascular resistance (SVR), rise in cardiac output
(CO) with onset of block. Increased SVR with
phenylephrine.
22
Neuraxial anesthesia is dangerous in OB because
  • Inferior vena cava compression by gravid uterus
    exacerbates decrease in venous return due to
    sympathectomy.
  • Hence, supine OB patient and fetus can crash
    after NA. Hence, routine LUD and pressor agents.

23
High or total spinal
  • Respiratory AND circulatory disaster.
  • Assist ventilation AND support CV system with
    vasopressors.
  • Getting baby out promptly will HELP with both
    breathing and venous return / cardiac output.

24
Colman-Brochu S 2004
25
When IVC is not compressed, venous return is
easy. Cardiac output stays high.
http//www.manbit.com/OA/f28-1.htm
Manbit images
26
When IVC is compressed, venous return occurs by
vertebral plexus and azygos system. CO falls and
uterine veins are engorged.
http//www.manbit.com/OA/f28-1.htm
27
Chestnut chap. 2
28
How much LUD is enough?
  • Now we judge by maternal BP and FHR.
  • Is there a better way?

29
Cardiac output (venous return) depends on
maternal position late in gestation. 34 y.o.
pregnant patient at 26 weeks 3 days estimated
gestational age. Hospitalized for preterm labor.
No contractions or medications at time of
measurement.
120
HR
80
80
SI
30
8
CI
3
Position S
R90 L90
R90 L90
S Minutes 0


33
Archer, Suresh and Ballas 2011
30
After epidural, BP and CO fall and dont respond
to phenylephrine or ephedrine. BP and CO increase
when patient is placed left side down.
Archer, Shapiro, Suresh 2011
31
Autotransfusion observed once patient is left
side down, blood squeezed out of contracting
uterus easily gets back to the heart, causing
increased CO, as seen here.
Archer, Shapiro, Suresh 2011
32
Basic CS monitoring
  • Talk with the patient!
  • Does her face display anxiety?
  • Take a deep breath!
  • Have her squeeze your fingers
  • What is her hand temperature?
  • Are the hand veins dilated?
  • Do your hands feel normal or do they feel a
    little numb?

33
CS red flags
  • I dont feel so goodI think Im going to throw
    up (Hypotension until proven otherwise).
  • Doc, I feel like Im not getting enough to
    breathe
  • The floppy arm sign.
  • The shaking head sign.
  • High spinal will need ventilatory help.

34
One more equation
  • Neuraxial anesthesia
  • Aortocaval compression
  • Unreplaced blood loss
  • Disaster

35
Intrathecal and epidural medications
  • Neuraxial local anesthetics cause sympathectomy
    and hypotension. Can cause motor block.
  • Fentanyl (rarely sufentanil) improves quality of
    block during CS, esp. visceral pain. No
    sympathectomy, no hypotension, no motor block.
    Can cause itching.
  • Morphine for post-CS pain relief. Itching?

36
Block level for CS
  • Need T4 (nipples) to block visceral pain
    (traction on peritoneum, exteriorize uterus).
    Numbness in hands is OK (C5-8).
  • Lower block will allow skin incision and you can
    probably get away with it but expect visceral
    discomfort. Leave uterus in for repair to
    decrease peritoneal traction?
  • Supplement with fentanyl, ketamine prn.

37
Neuraxial (NA) morphine
  • Delayed respiratory depression (up to 24 hrs
    later). With 0.1 mg, very rare (1 per several
    1000s). Rx with naloxone (Narcan).
  • ASA guidelines for post NA morphine monitoring
    RR q 1 hr x 12h then q 2h x 12h.
  • We do a post CS pain management visit.

38
Neuraxial morphine
  • Can cause itching, nausea, ileus, urinary
    retention. Itching Rxd with nalbuphine (nubain)
    or diphenhydramine (Benadryl).
  • We do pain orders 1st 24 hours. Caution with IV
    NA narcotics.
  • Multimodal analgesia NA morphine, NSAID, oral
    acetaminophen plus narcotic (Percocet), cautious
    IV opioid.

39
NSAIDs for post CS pain
  • Ketorolac commonly used around the country 30 mg
    IV q 6h x 4 doses. Maximum of 5 days.
  • NSAID contraindications renal problems (includes
    pre-eclampsia), GI ulcers, bleeding problems.
  • American Academy of Pediatrics says Ketorolac OK
    for breast feeding. Our NICU says yes. Package
    insert says no!

40
Slide courtesy of Alex Pue, MD
41
Spinal
Anesthetic is deposited inside the spinal sack
and quickly acts on the nerves
Slide courtesy of Alex Pue, MD
42
Slide courtesy of Alex Pue, MD
43
Combined spinal-epidural
Slide courtesy of Alex Pue, MD
44
Ultrasound for spinal block placement first,
midline is marked (shadow of spinous processes
in middle of probe).
http//www.usra.ca/sb_neuraxial
45
(No Transcript)
46
Then vertical level is marked between spinous
processes, where we can see reflection from
vertebral body.
http//www.usra.ca/sb_neuraxial
47
Ultrasound (US) can be useful in obese patients
or patients with scoliosis or other spine
pathology. We use the standard OB curved US
probe.
48
Needle insertion point is intersection of midline
(y-axis) and proper horizontal level (x-axis).
http//www.usra.ca/sb_neuraxial
49
Combined Spinal-Epidural
Slide courtesy of Alex Pue, MD
50
Anesthesia for CS Complications
  • Sympathectomy / hypotension
  • Nausea
  • Bradycardia
  • High spinal / respiratory paralysis
  • Aspiration
  • Difficult intubation
  • Local anesthetic toxicity (IV epidural)
  • Failed regional anesthesia? GA
  • Persistent neurological deficit

51
Uterine hypertonic syndrome
  • Rapid pain relief with CSE or epidural can cause
    fetal distress due to uterine hypertonus.
  • We must be aware to avoid unnecessary CS.
  • Dx is palpate uterus.
  • Rx is SC terbutaline or SL NTG.
  • Mechanism loss of epinephrine beta agonism?

52
Scenario 2 Examination for postpartum
hemorrhage (PPH)
  • Woman postpartum with hemorrhage.
  • You need to explore birth canal and repair
    laceration or remove retained placenta.
  • Epidural catheter in place.
  • How do we proceed?

53
Scenario 2 In PPH, we are worried about
  • Airway (GA is always Plan B)
  • Adequate IV access
  • Volume status (in shock RR?HR?BP).
  • Blood availability
  • Keep patient warm and warm all fluids (especially
    blood) prevent fatal triad of hypothermia,
    acidosis and coagulopathy.

54
Scenario 2 Examination for postpartum hemorrhage
  • Anesthesiologist should be reluctant to use
    epidural catheter in presence of uncorrected
    hypovolemia.
  • Even riskier with de novo spinal (faster onset).
  • Go to OR for exam / repair. Correct volume status
    and use neuraxial or GA.

55
Scenario 3 STAT CS for fetal distress
  • We are thinking Airway, airway, airway.
  • STAT CS is one reason we need advance knowledge
    of difficult airways. You tell us, or better, we
    take a peak at everybody.
  • Minimal History allergies, meds, heart and lung
    disease, other major med problems.

56
Scenario 3 STAT CS for fetal distress
  • If airway is sketchy and no neuraxial available,
    we all have a big problem.

57
Nervous anesthesiologist
  • If you want to make an anesthesiologist uptight
    and ornery, ask her to use her wonderful and
    dangerous drugs when the airway cannot be
    secured.
  • Dont put someone to sleep unless you are sure
    you can breathe for them.
  • For us, this is absolutely fundamental.

58
STAT CS
  • Often a flail.
  • Weve got to go. NOW!
  • Egos and emotions run high.
  • Does the patient know what is happening?
  • Talk to patient. Informed consent.
  • Dont endanger the mother to save the baby.
  • Anesthesia needs to know when and how to say no
    to the OB.
  • Stay calm.
  • Cover the basics (HP, IV access, airway,
    informed consent, patient asleep before incision.)

59
How do we kill patients in OB anesthesia?
  • Rush to the OR, pressure to put the patient
    down to save the baby.
  • IV induction, paralysis.
  • Panic, confusion, inexperience, bad luck?
  • Cant intubate, cant ventilate? death or brain
    damage.

60
The AIRWAY Anesthesias 1 concept
  • Just exactly what does it mean?
  • An anatomical and functional concept which means
    We can ensure that the patient will breathe on
    her own or we can breathe for her.
  • Protected airway means that stomach contents
    cant get into the lungs.

61
Intubating a dolphin would be very easy. They
have a blowhole. We would be out of a job.
62
Unlike dolphins, humans have a breathing orifice
that is hard to get to.
63
Cuffed endotracheal tube (ETT) gold standard of
airway maintenance and protection.
http//www.healthsystem.virginia.edu/Internet/Anes
thesiology-Elective/images/anesth0018.jpg
64
Laryngeal mask airway (LMA) gold standard of
airway rescue / maintenance device when ETT not
possible.
65
LMA sits behind larynx and epiglottis. Provides
limited airway protection. Can be a life-saving
device.
www.anecare.com/.../QED-spontaneous-brief.html
66
Oral airway plus lift mandible and tongue (jaw
thrust) basic airway maintenance maneuver.
Provides no airway protection but can be
life-saving. Do this in seizing patient, plus
turn her onto her side.
67
What are the threats to the airway?
  • You and I are the primary threats!
  • We want to help!
  • We want to save the baby!
  • Will we choose to induce anesthesia without
    ensuring the airway?

68
General anesthesia for CS
  • Recent anesthesia grads will have limited
    experience with GA for CS because of our success
    with neuraxial.
  • And we all get flustered.
  • A good topic for drills, practice.

69
Protocol for general anesthesia for CS
  • Abdomen is prepped, draped, OBs have knife in
    hand, ready to cut, prior to induction.
  • Clear, calm, specific communication.
  • Patient is awake, Patient is asleep, You can
    cut now.

70
Protocol for general anesthesia for CS
  • Two to three minutes of pre-oxygenation
    (patient breathes 100 O2 to fill lungs).
  • Pre-oxygenation provides a reserve of O2 for
    period of apnea after induction and paralysis and
    before ventilation.

71
Functional residual capacity (FRC) is our air
tank for apnea.
www.picture-newsletter.com/scuba-diving/scuba...
from Google images
72
Pregnant Mom has a smaller air tank.
Non-pregnant woman
www.pyramydair.com/blog/images/scuba-web.jpg
73
This is why we pre-oxygenate the patient.
It gives us more time to get the tube in before
she gets low on oxygen.
Wikipedia
74
Ramping up the obese patient to facilitate
intubation. Cephalad retraction of pannus can
interfere with breathing. Obese patient disaster
waiting to happen.
www.airpal.com/ramp.htm
75
Awake fiberoptic intubation can be lifesaving,
but it takes time and skill. We need to know
about difficult airways in advance, so we
evaluate patient and make plans.
76
Weight and Wellness Program (Dr. Lacoursiere)
  • Integrated approach to obese parturient
  • OB, Anesthesia, Nursing, equipment, training,
    patient buy-in, etc.
  • Protocols, bundles, etc.
  • In development

77
Scenario 4 Severe pre-eclampsia
  • Anesthesia worries
  • Platelets (also PT, PTT, fibrinogen?)
  • Airway swelling / pulmonary edema
  • Stroke / MI / CHF due to hypertension
  • Magnesium effects (uterine atony, potentiates
    neuromuscular blocking agents, patient on
    ventilator postop?).

78
Scenario 4 Severe pre-eclampsia
  • Our approach neuraxial unless platelets are low
    (50-100K is the number). Look at venipuncture
    sites for oozing, under BP cuff for bruising.
  • Neuraxial will help lower BP but dont let us
    overdo it!
  • Early epidural?

79
Scenario 4 Severe pre-eclampsia
  • Get epidural in before the platelets go down in
    HELLP?
  • Maybe, but then removal of catheter becomes a
    problem (same requirement for 50-100K).

80
Scenario 4 Severe pre-eclampsia
  • How recent does platelet count have to be in
    pre-eclampsia? Communicate with your
    anesthesiologist.
  • 2-6 hours in truly severe pre-eclampsia and
    florid HELLP? I have no firm answer.
  • 27 gauge spinal?

81
Scenario 4 Severe pre-eclampsia
  • We should NOT be more worried than usual about
    catastrophic hypotension with neuraxial
    anesthesia in pre-eclampsia.
  • This used to be taught but is less common in
    pre-eclampsia than in normal patients.

82
Scenario 4 Severe pre-eclampsia
  • If GA required (low platelets, abruption, severe
    fetal distress, DIC)
  • Prevent extreme hypertension with laryngoscopy by
    using IV fentanyl and / or labetalol before
    induction of GA.
  • Magnesium will potentiate non-depolarizing NMB
    agents (curare-like, vecuronium, rocuronium).

83
Scenario 4 Severe pre-eclampsia
  • Arterial line VERY useful in severe pre-eclampsia
    for
  • BP, but also mag levels, other blood draws, ABGs
    in case of pulmonary edema or ventilator care.
  • A little extra work (and nurses may be
    unfamiliar) but very helpful.

84
Summary
  • Neuraxial and general anesthesia are both threats
    to breathing.
  • Airway is the fundamental concept of anesthesia
    and our greatest obsession.
  • Prevention of aspiration of gastric contents is
    another of our obsessions.

85
Summary
  • Neuraxial anesthesia is best in OB, but GA is
    always the backup.
  • Neuraxial anesthesia blood loss IVC
    compression disaster.
  • In OB, we need to get the uterus off the IVC, but
    knowing how much LUD is enough may be difficult.
    EC may help with this.

86
Summary
  • OB anesthesiologist needs to communicate well
    with rest of OB team.
  • Obesity requires communication and planning
    (systems approach).
  • Spinal or epidural best in pre-eclampsia, but
    check platelets. GA in pre-E requires special
    care.

87
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