Transcript Obstetric Anesthesia Overview for Family Medicine Maternal and

Obstetric Anesthesia Overview
for Family Medicine Maternal
and Child Health
Éva Szabó, M.D.
June 3, 2015
Learning Objectives
Upon completion of the learning activity, participants should be
able to:
 1. Discuss the potential effects of labor analgesia on
obstetric outcome
 2. Compare the advantages and disadvantages of the most
common neuraxial labor analgesia techniques
 3. Identify those parturients who are at increased risk for
anesthetic complications
 4. Formulate a labor management plan for morbidly obese
parturients to include early initiation of labor analgesia
 Explain the risks and benefits of neuraxial morphine
administration for postcesarean analgesia
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Topics Covered Today
1. Epidural analgesia and obstetric outcomes:
progress of labor and method of delivery
2. Labor analgesia in the obese (especially
the morbidly obese) parturient
3. Neuraxial opioid for postcesarean
analgesia
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Pain Pathways of Labor
 During first stage, pain results from uterine contractions
and distention of lower uterine segment and cervix
 Visceral afferent nerve fibers travel with sympathetic
nerves
 Visceral pain impulses entering the spinal cord at T10 –L1
must be blocked
 Late first stage and second stage: stretching of vagina,
pelvic floor, and perineum
 Pain impulses travel via pudendal nerve
 Somatic impulses entering the spinal cord at S2-4 must
also be blocked
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Neuraxial Labor Analgesia
 Most effective method of intrapartum pain relief
 Only form of analgesia to provide complete analgesia for
both stages
 Additional benefits:
 reduced maternal catecholamine
 analgesia blunts hyperventilation-hypoventilation cycle
 catheter allows rapid conversion of analgesia to surgical
anesthesia: safer than general anesthesia for emergency
cesarean section
 Concerns about epidural’s effect on the progress of labor
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Indications of Neuraxial Analgesia – Patient
Selection
 Maternal request is sufficient indication
 For patients at risk of operative delivery (maternal or fetal)
 Early (prophylactic) insertion should be considered in
high-risk patients for either obstetric or anesthetic
indications to reduce the need for GA
 Preeclampsia
 Twins
 Difficult airway
 Obesity
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Contraindications to Neuraxial Analgesia
 Absolute
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Patient refusal or inability to cooperate
Infection at the site of needle insertion
Coagulopathy
Severe hypovolemia
Sepsis
 Relative
 Systemic infection
 Neurologic disease
 Back pathology or surgery
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Effects on Labor
 Concern about side-effects on the progress of labor
 Increased Cesarean rate??
 Increased rate of instrumental delivery??
 Prolongation of labor??
 Difficult to study
 Observational studies – not considered in systematic
reviews
 No studies where patients were randomly assigned to
receive epidural analgesia vs. no analgesia
 Randomized controlled trials: epidural vs. systemic opioid
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Cesarean Section Rate
 Early (1989) retrospective study of 711 consecutive
nulliparous women with a spontaneous onset of labor
showed 10% C-section rate for dystocia in the epidural
group vs. 4% in the non-epidural group
 Another retrospective study by same author in 1991: even
greater difference
 Retrospective studies suffer from selection bias
 Patients choose their analgesia
 Women with more pain/dysfunctional labor request epidural
 Greater labor pain in early labor may be a marker for increased
risk for obstetric complication and operative delivery
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Cesarean Section Rate: Prospective
Randomized Trials
 First prospective, randomized trial of 93 women in 1993 [1]
 C/S: 12 of the 48 in the epidural group and1 in 45 in the meperidine group
 Increased risk of C-section was limited to dilation<5cm
 Primary investigators made decisions regarding mode of delivery
 More randomized controlled trials
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Meta-analysis of 18 prospective randomized trials, 2004 [2]
6701 patients
No difference in the cesarean delivery rate
Increased incidence (13% vs. 7%) of instrumental vaginal delivery
Prolongation of first and second stage
 Limitations of randomized trials
 Cannot allocate patients to no analgesia: epidural compared to systemic
 Blinding is impossible
 Crossover is common
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Operative Vaginal Delivery
 Early retrospective studies reported association between epidural
analgesia and instrumental vaginal delivery
 Retrospective studies suffer from selection bias
 Studies in teaching institutions
 Series of randomized controlled trials 1987-90, Chestnut
 Dilute local anesthetic did not increase the incidence of instrumental
vaginal delivery
 Dilute local anesthetic did not provide satisfactory second stage
analgesia
 Maintenance of a dense block until delivery provided good analgesia
but lead to more instrumental vaginal deliveries
 Effective neuraxial analgesia also resulted in prolongation of the
second stage
 Dilute local anesthetic with opioid provided acceptable analgesia with
less intense motor block and did not significantly increase the
incidence of instrumental vaginal delivery
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Timing of Labor Epidural
 ACOG guideline 2002: delay until 4-5 cm (to reduce the risk
of C-section)
 2005 NEJM article by Wong (728 women) [3]
 Early CSE (2cm!) vs. IV/IM opioid followed by epidural later (4
cm)
 No significant difference between the groups in the rate of
Cesarean delivery and instrumental vaginal delivery
 Shorter first stage in the early group
 Meta-analyses
 Early epidural not associated with increased risk of C-section or
instrumental vaginal delivery
 Early systemic opioid associated with non-reassuring fetal
status
 Early systemic opioid associated with lower umbilical artery pH
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Key Points
 Administered with modern protocols, neuraxial labor
analgesia does not increase the risk of cesarean
delivery when compared with systemic opioid
 Early initiation does not increase the cesarean rate
 Severe pain in early labor may signal a higher risk for
operative delivery
 Early initiation does not prolong the first stage
 Effective analgesia does prolong the second stage
 Dense block increases the rate of instrumental vaginal
delivery
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Epidural Technique
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Types of Neuraxial Analgesia
 Epidural
 Caudal
 Spinal
 Single shot
 continuous
 Combined spinal-epidural
 Dural puncture epidural analgesia (DPEA)
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Continuous Lumbar Epidural Analgesia
 Most common technique
 Analgesia is initiated with bolus injection after test dose
 Analgesia can be maintained until after delivery
 Intermittent bolus, infusion, PCEA, programmable pumps
 Allows conversion to epidural anesthesia
 Local anesthetic spreads both cephalad and caudad
 T10-L1 has to be blocked during 1st stage
 S2-S4 added for 2nd stage
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Caudal Epidural Analgesia
 Approach through sacro-coccygeal ligament
 Older technique
 Technically more difficult
 Requires large volumes of LA solution
 Risk of fetal injury
 Double catheter technique
 Remains an option for patients with L-spine pathology,
surgery etc.
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Spinal Analgesia
 Single shot if delivery is imminent (or if no epidural
service available)
 Continuous spinal
 No FDA approved microcatheter
 Epidural catheter requires large-gauge introducer needle
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(epidural needle, 18 or 17 gauge)
High incidence of headache
Option after “wet tap” (preferred option at UNM)
Intentional spinal catheter controversial
Greatest advantage: easily converted to spinal
anesthesia if necessary
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Combined Spinal-Epidural
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Combined Spinal-Epidural
The needle-through-needle technique
1. Epidural space is identified with the LOR technique
2. Spinal needle through epidural needle; dural puncture
3. Intrathecal dose administered; spinal needle removed
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Combined Spinal-Epidural
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Combined Spinal-Epidural
 Increasing popularity
 Fast onset
 Complete analgesia in early labor with IT opioid ± LA
 “Walking epidural” – no motor block
 Higher success rate of epidural
 Optimal midline placement
 Increased incidence of fetal bradycardia
 Cannot initially confirm correct catheter placement
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Dural Puncture Epidural
 Needle-through-needle
 Without injecting anything into the intrathecal space
 Additional confirmation of epidural space
 Allows for testing the epidural catheter
 Hypothesis: transfer of medication across the dural
puncture hole
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Obesity: Definition
 Excessive body fat with adverse health implications
 Metabolic disease
 Ideal body weight: lowest mortality rate for given
height and gender
 Broca index: height(cm)-100, height(cm)-105 (women)
 BMI: weight/height2 (kg/m2)
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18-25 normal
25-30 overweight
>30 obesity (class I, II)
>40 morbid obesity (class III)
>50 (55) super obesity
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The Obesity Epidemic
 2011-12 National Health and Nutrition Examination Survey:
35% of adults were obese (BMI>30)
 8% of reproductive-aged women are morbidly obese
 Certain ethnic groups have higher incidence
 The prevalence of childhood obesity is 2.5 times higher in
offspring of obese women
 Majority of LGA babies are born to obese mothers
 Insulin resistance shunts nutrient excess to the fetus
 Metabolic disease is programmed in utero
 Increases risk for chronic diseases: OSA, HTN, CAD, DM,
gall bladder disease, DJD, DVT
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Respiratory Function in Obesity
 Increasing weight  increased O2 consumption, CO2
production
 Increased minute ventilation
 Decreased chest wall compliance (weight)
 Decreased FRC
 Increased work of breathing (rapid, shallow – more
efficient breathing pattern)
 Obstructive sleep apnea (OSA)
 Desaturation during sleep, snoring, daytime fatigue,
chronic hypoxemia, pulmonary HTN, RV failure
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Respiratory Function in Pregnancy
 Respiratory changes start early in pregnancy
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Progesteron is a respiratory stimulant
Increased O2 consumption, CO2 production
Increased minute ventilation
Increased respiratory rate and tidal volume
Decreased airway resistance
Increased work of breathing
Hyperventilation results in mild respiratory alkalosis
Arterial CO2 decreases from 40 to 30 mmHg
Arterial O2 increases (less increase in obese women)
 At 20 weeks, mechanical effects of the uterus
 Decreased FRC
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Cardiovascular System
Obesity Increases the Demands on the CV System
 Excess tissue needs additional oxygen
 Increased blood volume, increased cardiac output
 Increased incidence of mild to moderate HTN
 Arrhythmias: fatty infiltration of myocardium and
conduction system
 Left ventricular dilation, hypertrophy, dysfunction
 Patients may be asymptomatic despite CV disease due to
minimal physical activity, limited mobility
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Cardiovascular Changes in the Obese
Pregnant woman
 Physiologic effects of pregnancy and obesity are additive
 Blood volume and CO increases during pregnancy
 Obesity independently increases blood volume and CO
 Additional elevation of CO during labor, and postpartum; obese
parturients are at risk in the peripartum period
 BP is maintained during normal pregnancy
 Obesity increases risk of HTN, preeclampsia
 Risk of cardiomyopathy
 Supine hypotension syndrome more pronounced; may be
impossible to position properly on OR table
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Cardiovascular Changes in Pregnancy
and Obesity [6]
Pregnancy
Obesity
Combined
Blood volume
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Cardiac output
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Blood pressure
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HR
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Supine hypotension
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Anesthetic Implications of Morbid Obesity
 Providing anesthesia presents unique challenges
 Comorbidities increase anesthetic risk (ASA 3, severe
systemic disease
 Difficult access, line placement
 Difficulty moving and positioning the patient
 Difficulty monitoring (BP cuff may not fit)
 Technical difficulties when placing neuraxial block
 Potentially difficult airway management
 Neck circumference best predictor of difficult intubation
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Anesthetic Implications of Obesity in
Pregnancy
 Obesity increases maternal morbidity and mortality
 Comorbidities: HTN, preeclampsia, DM
 Long , difficult labor, induction, failed induction
 Obesity increases perioperative risk
 Cesarean delivery
 Surgical and anesthesia-related complications,
postoperative complications
 Care of the morbidly obese parturient is challenging for
everybody involved and requires planning and good
communication
 Obesity = high-risk pregnancy
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ACOG recommendation [4]:
“Because these patients are at increased risk of
emergent cesarean delivery and anesthetic
complications, anesthesiology consultation early in
labor should be considered”
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Why do we worry?
 Anesthesia-related complications are the seventh leading cause
of maternal mortality
 Maternal obesity increases the risk of maternal death
 Incidence of failed intubation 1:2200 in general surgical
population, 1:300 in obstetric patients, even higher in obese
patients
 Most morbidly obese parturients will require some sort of
anesthetic intervention
 General anesthesia carries higher risk in these patients
 Anesthesia consult allows for planning and decreases the risk
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Obesity, obstetric complications and cesarean
delivery rate – A population-based screening
study, Weiss et al., Am J Obstet Gynecol 2004; 190:1091
 Question: is obesity associated with obstetric complications?
 Prospective multicenter review of 16,102 patients
 13,752 control (BMI<30)
 1,473 obese (BMI 30-35)
 877 morbidly obese (BMI >35)
 Result: obesity had a statistically significant association with
GHTN, preeclampsia, GDM, macrosomia (OR 2.4 – 4)
 Cesarean rate 33.8% for obese, 47.4% morbidly obese
(control 20.7%) (nulliparous)
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Maternal superobesity and perinatal
outcomes, Marshall et al., Am J Obstet Gynecol 2012;206:417.e1-6
 Question: is there an increased risk of maternal and fetal
complications in maternal superobesity when compared with
maternal obesity and morbid obesity
 Retrospective cohort-study
 64,272 women with BMI≥30
 82.5% obese, 15.6% morbidly obese, 1.8% superobese
 Result: Increasing BMI was associated with increased risk of
cesarean delivery (49% in the superobese)
 Dose-response relationship between worsening obesity and
Cesarean delivery, macrosomia, neonatal hypoglycemia,
preeclampsia
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Anesthetic Management of Labor
 Obese parturients need good analgesia
 Effective pain relief improves respiratory function, decreases O2
consumption
 Effective pain relief attenuates cardiovascular response to
contraction pain (BP, HR, CO)
 Higher incidence of macrosomia, complicated labor, pain
 Higher incidence of induction, failed induction
 Cesarean rate increases with BMI
 Need a flexible plan for labor analgesia for vaginal delivery or
labor analgesia ending in Cesarean delivery
 Continuous technique can be extended for cesarean delivery
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Continuous Neuraxial Analgesia &
Anesthesia Techniques
 Can be extended when cesarean delivery becomes necessary
 Lumbar epidural labor analgesia
 Combined spinal-epidural analgesia
 Continuous spinal analgesia
 All of the above can be very challenging in obese patients
 Obscured landmarks
 Distance to epidural space - long needle available
 All require proper positioning and take time
 Nothing can be done STAT in a morbidly obese
parturient/patient [6]
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Technical Difficulties
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Continuous Lumbar Epidural Analgesia
 Placement can be difficult in the morbidly obese (multiple
attempts)
 Obscured landmarks; identification of midline may be
difficult
 Ultrasound imaging also difficult
 Distance to epidural space correlates with BMI
 High failure rate due to catheter migration during labor
 Block has to be PERFECT!
 If any doubt, epidural catheter has to be replaced [7]
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Tuohy Needles: 9 cm and 15 cm
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Cesarean Section in the Morbidly Obese
Parturient with Good Labor Analgesia
 Moving the patient to the operating room (heavy bed+ IV
pole with pumps) – need moving help
 Transfer to OR table
 Two pairs of extenders
 Careful attention to IV, epidural
 Left uterine displacement as soon as possible
 Long safety straps, monitors (consider A-line)
 Start dosing epidural
 Leave FHR monitor on as long as possible
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Case
 33-y-o G1 P0, EGA 39 weeks, 129kg, 163 cm (5’4”),
BMI 48.5 admitted for induction of labor
 Type II diabetes, macrosomia
 Saturday evening induction started; anesthesia
consult on Sunday
 Pt. requested epidural Monday morning; cervix 2 cm
 Epidural placement; loss of resistance at 9 cm
 20 hours later: no change in the last 6 hours
 Chorioamnionitis
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Case continued
 Patient consented for C-section (Tuesday
morning)
 Anesthetic plan discussed :
 Excellent labor analgesia  plan epidural anesthesia
 Pt. taken to OR at 0858
 Pt. moved herself (with some help) to OR table
(7 minutes)
 IV, epidural catheter intact
 Left uterine displacement
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Left Uterine Displacement
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Left Uterine Displacement
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Lidocaine 2% injected to establish surgical anesthesia.
0920 (22 minutes later): sensory level adequate to retract
the pannus.
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Case continued
 Incision at 0940
 Uterine incision 0951
 Delivery at 0953 (almost 1 hour after we started
moving the patient from her room to the operating
room)
 Apgars 9, 9, 4155g.
 Total operating time 1 hour 11 minutes, EBL 600 ml
 Discharged home on POD #4
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General Anesthesia for Cesarean Delivery
 GA is riskier than regional in the obstetric patient (relative risk 1.7).
Why?
 Intubation is more difficult in the obstetric patient
 GA is often chosen in emergencies
 GA is most commonly used in highest risk patients
 Combination of morbid obesity and pregnancy increases the risk of
GA
 GA cannot be avoided if it is an emergency and:
 The patient does not have an epidural catheter
 If there is no time for spinal anesthesia
 If there is a contraindication to any neuraxial technique
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Emergency Cesarean Section under General
Anesthesia in the Morbidly Obese Parturient
 Added complexity of providing care
 Additional staff to help move the patient
 All components are more time consuming
 Risk of losing IV access
 Technical issues to safely manage the morbidly obese
parturient
 Appropriate table, extenders, safety straps
 Ramp or wedge to position for intubation
 Safe positioning to avoid fall
 Safe positioning to avoid aortocaval compression
 All of the above are difficult to achieve in an emergency
situation
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Summary: How to Avoid a Catastrophe
Communication!
 Identify morbidly obese patients in prenatal clinic
 refer to a center where epidural analgesia is available
 Refer them to anesthesia preoperative evaluation
 Aggressive approach: recommend early epidural
placement
 Technical issues: OR table, extenders, ramp/wedge ready
 Proper positioning for intubation if GA required
 Full preoxygenation takes minutes but is extremely
important
 Nothing can be done STAT in a morbidly obese
patient
 Anticipate problems to avoid a crash section
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Other Medical Conditions Requiring Predelivery Anesthesia Evaluation
 Severe cardiac or pulmonary disease
 Coagulopathy or anticoagulation
 Prior anesthesia-related complication or family history
 Contraindication to regional anesthesia
 Back surgery/back pathology
 Spinal cord disease
 Facial deformity or limitation of neck mobility
 Neurologic/ neuromuscular disorders
 Placenta accreta/increta/percreta
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“Duramorph”
 Preservative-free morphine for neuraxial administration:
 Subarachnoid (spinal, intrathecal): very small dose required
 Epidural: dose similar to single IV dose (small fraction crosses
the dura)
 Opioid receptors in the spinal cord
 Intrathecal opioids do not cause motor block
 Mean duration of analgesia 20-23 hours
 Analgesic potency of morphine:
 IV
1
 Epidural
10
 Intrathecal 200
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Benefits and Problems
 Better pain control facilitates:
 Early ambulation (less DVT)
 Early maternal-infant bonding
 Lower doses: 0.1-0.2 mg IT, 2-3 mg epidurally
 Lower plasma (breast milk) opioid levels
 Better maternal satisfaction
 Side effects
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Pruritus
Nausea and vomiting
Respiratory depression
Herpes labialis (HSV-1) reactivation may be more likely
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Pruritus
 Incidence 40-80%
 Most frequent cause of dissatisfaction
 Most severe at 3-6 hours after IT Morphine
 Treatment:
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Nalbuphine 2.5-5 mg IV q 4h
Naloxone (0.4 mg/mL) 0.04-0.08 mg IV
Diphenhydramine 25-50 mg IV q 4h
Ondansetron
Propofol
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Nausea/Vomiting
 Incidence 10-60%
 Treatment:
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Nalbuphine 5-10 mg IV q 4 hours
Ondansetron 4 mg IV q 6 hours
Metoclopramide 10 mg IV
Intractable nausea: Naloxone 0.04-0.08 mg IV bolus then
0.05-0.1 mg/h infusion
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Respiratory Depression
 Definition?
 Failure to respond to PaO2<60 or PaCO2>50
 Not synonymous with RR
 Peak 3.5 - 12 hours after injection
 Always preceded by sedation
 Exacerbated by sedatives, morbid obesity
 Risk is very low with currently used doses
 Treatment: naloxone, O2
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Breakthrough Pain
 Should not be treated with opioids in the first 24 hours
without prior discussion with the anesthesia team
 “Anesthesia spinal morphine” order set allows for oxycodone
if pain not controlled or small doses of IV morphine if pain
not controlled with oxycodone
 Risk for of respiratory depression, hypoxemia
 Ketorolac and ibuprofen preferred; multimodal analgesia
 Morphine PCA rarely needed
 Small doses 0.5-1 mg
 No basal rate
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References
1.
Thorp et al. The effect of intrapartum epidural analgesia on nulliparous labor:
a randomized, controlled, prospective trial. Am J Obstet Gynecol
1993;169:851-8
2.
Leighton et al. Epidural analgesia and the progress of labor. In EvidenceBased Obstetric Anesthesia 2005. p 10-22
3.
Wong et al. The risk of cesarean delivery with neuraxial analgesia given early
vs. late in labor. NEJM 2005;352:655-665
4.
ACOG Committee Opinion Obesity in Pregnancy 2013
5.
Soens et al. Obstetric anesthesia for the obese and morbidly obese patient:
an ounce of prevention is worth more than a pound of treatment. Acta
Anaesthesiol Scand 2008; 52: 6-19
6.
Lucas. The 30 minute decision to delivery time is unrealistic in morbidly
obese women. Int J Obstet Anesth 2010; 19: 431-7
7.
Roofthooft. Anesthesia for the morbidly obese parturient. Curr Opin
Anaesthesiol 2009; 22:341-346
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