THE OBESE PARTURIENT

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THE OBESE PARTURIENT

• HARRY SINGH, MD
• DEPT. OF ANESTHESIOLOGY
• UTMB

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INDICES OF OBESITY AND THEIR PARAMETERS

• Index Definition Values
• __________________________________________________
  _____________
• Overweight 20 gt ideal
• Obesity gt 20 over ideal
• Morbid obesity Ideal weight x 2
• Broca index Ideal female weight Ht (cm) 105
• Body Mass Wt (kg) Normal 25, obese gt 30
• (Quetelet) index Ht (m)2
• 3 Ht (in)
• Ponderal index v Wt (lb) Obese lt 11.6
• __________________________________________________
  ____________
• From Dewan DM, The obese parturient. In James FM,
  Wheeler AS, Dewan DM, editors.
• Obsteric Anesthesia The Complicated Patient, 2nd
  ed. Philadelphia, FA Davis, 1988468.

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DEFINITIONS AND INCIDENCE

• Normal BMI 25
• Overweight up to 20 more than ideal body weight
  or BMI 25-29
• Obesity BMI gt 30
• Morbid Obesity twice the ideal body weight or
  BMI gt 40
• Recent data from National Center for Health
  Statistics suggests 54 Americans overweight and
  21 obese
• 6-10 parturients morbidly obese

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TYPES OF OBESITY

• Android Obesity Truncal distribution of fat
• Associated with high incidence of cardiovascular
  disorders
• Gynecoid Obesity Fat distributed to thighs and
  buttocks
• Associated with pregnancy

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PATHOPHYSIOLOGIC CHANGES

• PULMONARY
• ? O2 consumption and ? CO2 production
• Secondary to metabolic activity of adipose
  tissue
• ? Minute Ventilation
• Reduced chest wall compliance (Restrictive
  defect)
• ? Functional Residual Capacity and Residual
  Volume
• FRC may be less than closing capacity?airway
  closure during tidal ventilation?V/Q mismatch and
  shunting
• Accentuated in supine, trendelenberg or lithotomy
  position

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EFFECT OF POSITION ON LUNG VOLUMES
In obesity, decreased chest wall compliance
results in a functional residual capacity (FRC)
that decreases at the expense of expiratory
reserve volume (ERV). Closing capacity (CC)
stays normal. (From Vaughan RW. Pulmonary and
cardiovascular derangements in the obese patient.
In Brown BR, editor. Anesthesia and the Obese
Patient. Philadelphia, FA Davis 108226.)
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PICKWICKIAN SYNDROME or OHS

• 8 of obese patients
• Alveolar hypoventilation, somnolence and morbid
  obesity
• ? Soft tissue mass of oropharynx ?Intermittent
  obstruction of airway during sleep
• Hypoxemia, hypercarbia
• Polycythemia, pulmonary hypertension and right
  ventricular failure
• Pulmonary embolism and pneumonia

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PATHOPHYSIOLOGIC CHANGES

• CARDIOVASCULAR
• ? Blood Volume and ?Cardiac Output (? Stroke
  volume)
• Blood flow through adipose tissue-2 -3 ml/min/100
  g
• Morbid obesity 50 mild HTN, 5-10 severe HTN
• Doubling of incidence of CAD
• ? Afterload and preload (?BP and ?Blood Volume)
• ? Left ventricular end diastolic pressure and LV
  hypertrophy
• More vulnerable to pulmonary hypertension
• Airway obstruction or hypoxemia? ? PAP or PAOP

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PATHOPHYSIOLOGIC CHANGES

• ENDOCRINE AND METABOLIC
• ? Incidence of adult onset diabetes
• Impaired glucose tolerance
• Resistance to insulin
• Hypertrophy of Islets of Langerhans
• High serum triglycerides
• High serum cholesterol
• ? Incidence of IHD

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PATHOPHYSIOLOGIC CHANGES

• GASTROINTESTINAL
• ? Intragastric and intrabdominal pressures
• ? Lower esophageal sphincter tone
• ? Hiatus Hernia
• Strong correlation between BMI and reflux
  symptoms (Odds ratio 6.3 for women with BMIgt35)
• 80 obese patients have gastric pH lt 2.5
• 86 obese patients have gastric volumegt25mL
• 75 patients at risk of aspiration pneumonitis
• Combination of pregnancy and obesity increases
  the risk of aspiration pneumonitis

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CHANGES IN THE AIRWAY

• Short neck, ? chin to chest distance
• Limited flexion of cervical spine
• Nonexistent atlantooccipital gap
• Limited atlantooccipital extension and bowing of
  cervical spine and forward displacement of larynx
• Adiposity of the face, shoulders, neck and
  breasts
• Narrow pharyngeal opening due to enlarged tongue
  and fleshy pharyngeal and supralaryngeal tissues
• ? Incidence of failed or difficult intubation
• 33 incidence of difficult intubation in obese
  parturients
• Percutaneous cricothyrotomy may be difficult due
  to difficulty to palpate landmarks

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MATERNAL MORTALITY

• Obesity risk factor in 12 of 15 anesthesia
  related deaths in Michigan between 1972 to 1984
  Failed intubation leading cause of death
• 4 of 7 maternal deaths in Chicago Maternity
  Hospital in women gt 200 lbs
• 12 of all maternal deaths in obese women between
  1963 and 1997 in Minnesota Pulmonary embolus
  leading cause of death
• Anesthesia, surgery and pregnancy additively
  increase the mortality and morbidity in these
  patients.

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MATERNAL COMPLICATIONS

• 47 of obese parturients have antenatal disease
• Gestational diabetes (Odds ratio 4.00)
• Gestational hypertension (Odds ratio 3.20)
• Preeclampsia (Odds ratio8.20)
• Incidence of cesarean delivery (Odds ratio2.69)
• Shoulder dystocia (Odds ratio3.14) most common
  indication for emergency CS in these patients
• In one study of 117 patients, 62 CS rate in
  women gt 300 lbs
• Another study of 107 patients found 58 CS rate
  in women 200-504 lbs
• Blood loss gt1000 ml for cesarean delivery
• Prolonged duration of surgery
• Increased incidence of postpartum hemorrhage

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OBSTETRIC COMPLICATIONS

• Fetal macrosomia (Odds ratio3.82) Maternal
  obesity, diabetes and increased gestational age
  contributory factors
• Meconium aspiration (Odds ratio2.85)
• Late decelerations (Odds ratio2.52)
• Prolonged gestation
• Dysfunctional labor patterns
• Twins/breech presentation
• Fetal umbilical cord accidents
• Increased incidence of induction of labor due to
  prolonged gestation
• High incidence of failed inductions
• Increased incidence of FTP and prolonged second
  stage of labor

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PERINATAL OUTCOME

• Birth asphyxia and trauma due to shoulder
  dystocia
• Instrumental delivery (Odds ratio1.34)
• Neonatal death (Odds ratio3.41)
• Intrauterine fetal demise (Odds ratio2.79)
• Higher pregnancy weight associated with
• increased risk of late fetal death
• Increased neural tube defects and other
  congenital malformations
• Neonatal hypoglycemia more frequent
• Increased frequency of neonatal intensive care
  admissions

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EPIDURAL ANALGESIA (KEY POINTS)

• Early insertion of epidural desirable in obese
  parturients undergoing trial of labor
• Landmarks invariably difficult to palpate
• May consider ultrasound guidance for midline
  bony structures with assistance from obstetrician
• Small directional errors exaggerated with
  increasing depth of epidural space
• Patient can help guide to the midline by telling
  if she senses pressure from needle advancement to
  right or left
• Have extra long needles available if necessary
• Non functioning epidural should be replaced
  immediately
• Catheter should be inserted at least 5 cm in
  epidural space as risk of catheter displacement
  high in obese parturients

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EPIDURAL ANALGESIA (KEY POINTS)

• Higher incidence of failed epidural, unilateral
  block and more attempts to identify the space in
  morbidly obese
• 94 of obese parturients (gt300 lbs) achieved
  successful analgesia in one study
• Catheter had to be replaced once in 46 of these
  patients
• Two or more times in 21 of these patients
• May consider a planned wet tap with your epidural
  needle
• If one occurs unexpectedly, consider converting
  to a continuous spinal with dilute local
  anesthetic and opioid for labor analgesia
  (usually 2ml/hr of 0.125 bupivacaine with
  fentanyl optimal)
• More concentrated local anesthetic for cesarean
  delivery (1-2 ml of 0.75 bupivacaine with
  fentanyl and durmaorph)
• Postdural puncture headache rare in morbidly
  obese patients

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EPIDURAL ANALGESIA (KEY POINTS)

• Lateral sitting or semi recumbent position to
  minimize airway closure and aortocaval
  compression
• O2 administration throughout labor to prevent
  hypoxemia
• Epidural decreases O2 consumption and improves
  oxygenation and prevents increases in cardiac
  output by inhibiting catecholamine release during
  labor
• Optimal titration of local anesthetic can prevent
  hypotension and excess motor block
• Epidural advantageous due to frequent need for
  operative vaginal or cesarean delivery in these
  patients
• Can also be used for postoperative pain
  management
• CSE not the technique of choice for labor
  analgesia in obese parturients due to delayed
  assessment of functionality of the epidural

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SPINAL ANESTHESIA (KEY POINTS)

• Negative correlation between the degree of
  obesity and dose requirement of local anesthetic
• Higher block may be due to decreased CSF volume
  (engorged epidural venous plexus), exaggerated
  curvature of lumbar spine, pelvic fat and
  hormonal changes of pregnancy
• High incidence of hypotension following spinal
  due to higher and variable extension of autonomic
  blockade in obese patients
• High block may exaggerate hypoxemia in these
  patients
• Single shot spinal disadvantageous due to
  prolonged surgery in these patients
• Continuous spinal with epidural catheter may be
  advantageous in patients for emergent/urgent CS
  with anticipated difficult airway
• CSE technique of choice for scheduled/elective CS
• CSE set with Gertie Marx spinal needle (12.4 cm)
  may be necessary for some these patients

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GENERAL ANESTHESIA (KEY POINTS)

• Increased incidence of complications with GETA
• The operating room should be prepared with a bed
  of appropriate width and strength, and wider arm
  supports and pads
• Most operating room beds only rated for weights
  up to 300 lbs
• The patient should be interviewed early in course
  of labor or preferably during antepartum visit
• Consider additional tests during preop visit like
  CXR, EKG and PFT with ABGs
• Thorough airway evaluation mandatory
• Considerable proportion of maternal mortality
  associated with GETA during cesarean delivery
• GETA should only be confined to cases where it is
  indispensable to save mother or fetus
• Safety of mother of paramount importance and
  overrides fetal considerations

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GENERAL ANESTHESIA(KEY POINTS)

• Consider multimodal aspiration prophylaxis
• Difficult mask ventilation, laryngoscopy and
  intubation should be anticipated however,
  obesity alone doesnt predict difficult airway
• 13 obese patients pose difficulty with
  intubation
• 30 obese parturients pose difficulty with
  intubation
• Landmarks for block obscure, therefore, consider
  topical anesthesia of airway with 4 lidocaine
• Direct laryngoscopy following topical anesthesia
  can be considered for anticipated difficult
  airway
• ObesityMP IV Consider fiberoptic intubation
• Positioning for airway important the head, neck
  and shoulder should be raised, there should be
  straight line between sternal notch and the
  external auditory meatus and patient should be in
  reverse trendelenberg position

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GENERAL ANESTHESIA (KEY POINTS)

• Rapid sequence induction should not be performed
  in obese parturients with anticipated difficult
  airway
• Patient should be fully denitrogenated with 100
  O2 for 3-5 min before rapid sequence induction
• Additional experienced hands must be available
  for assistance during administration of GETA
• Have ancillary airway equipment such as
  fiberoptic bronchoscope, short handle
  laryngoscope and an assortment of laryngeal mask
  airways available
• Higher FiO2, tidal volumes and PEEP may be
  required to maintain adequate SaO2
• Effect of muscle relaxant during surgery may be
  overestimated, whereas, reversal effect may be
  underestimated

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GENERAL ANESTHESIA (KEY POINTS)

• Drug doses may be based on actual or ideal body
  weight
• Highly lipophilic drugs (barbiturates,
  benzodiazepines) have considerably increased
  volume of distribution with higher doses and
  longer elimination half-lives
• Non-lipophilic or weakly lipophilic drugs
  administered based on lean body mass
• Emergence faster after desflurane than
  sevoflurane or isoflurane anesthesia and their O2
  saturations higher with desflurane in PACU
• Extubate conservatively and in reverse
  trendelenburg position
• The incidence of dangerous postextubation
  obstruction is 5 in patients with OSA, so
  extubate with oral or nasal airway in place.
• If concerned about possible re-intubation,
  extubate over an airway exchanger

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POSTOPERATIVE MANAGEMENT

• Patient should be kept in semi-recumbent or
  reverse trendelenberg position
• Continue monitoring for hypoxia and
  hypoventilation and consider CPAP mask if OSA a
  problem
• A monitored or step down bed may be more
  appropriate location for recovery in the LD
• Hospitalization often prolonged
• Wound dehiscence and infection more common
• Increased incidence of postoperative pulmonary
  complications including hypoxemia, atelectasis
  and pneumonia
• Vertical abdominal incision more likely to cause
  hypoxemia
• Increased risk of deep venous thrombosis and
  pulmonary thromboembolism-consider
  anticoagulation soon after surgery with LMWH or
  unfractionated heparin
• Adequate postoperative analgesia essential to
  promote early ambulation and to decrease risk of
  pulmonary complications

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CONCLUSIONS

• Obesity increases the risk of anesthesia related
  maternal mortality. Airway complications
  represent the most common cause of
  anesthesia-related maternal mortality
• Unlike most parturients, associated
  co-morbidities complicate management of morbidly
  obese parturients
• The obese parturient is at increased risk for
  fetal macrosomia, shoulder dystocia and cesarean
  section
• Early administration of epidural is advisable in
  obese parturients undergoing trial of labor a
  non-functioning epidural should be replaced
  immediately
• The anesthetic management requires patience,
  planning and close collaboration amongst involved
  physicians

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SUGGESTED READINGS

• DAngelo R, Dewan DD. Obesity in Principles and
  Practice of Anesthesia, Editor David H Chestnut,
  Elsevier Mosby, PA.
• Hawkins JL. Labor and Delivery Management of the
  Morbidly Obese Parturient. 2005 IARS Meeting
  Review Course Lectures.
• Endler GC, Mariona FG, Solok RJ, Stevenson LB.
  Anesthesia related maternal mortality in
  Michigan. Am J Obstet Gynecol 1988 159187-93.

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HAVE A GOOD DAY!