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The Morbidly Obese Parturient: Comorbidities, Complications, and Considerations

This PBLD was peer-reviewed by a panel of experts from the Society of Obstetric Anesthesia and Perinatology (SOAP) and has been endorsed by the SOAP Education Committee.

Required Pre-work:

  1. Lamon AM, Habib A. Managing anesthesia for cesarean section in obese patients: current perspectives. Local and Regional Anesthesia. 2016; 9:45-57.
  2. Obesity in Pregnancy. Committee Opinion No. 549. American College of Obstetricians and Gynecologists. Obstet Gynecol. 2013; 121:213-7.
  3. Tonidandel A, Booth J, D’Angelo R, Harris L, Tonidandel S. Anesthetic and obstetric outcomes in morbidly obese parturients: a 20-year follow-up retrospective cohort study. Int J Obstet Anesth. 2014;23(4):357-64.

Learning Objectives:

Upon conclusion of this session, the fellow will be able to:

  1. Discuss the classification system of obesity and the common comorbidities associated with obesity in pregnancy.
  2. Describe the anticipated anesthetic challenges of the obese parturient.
  3. Discuss the current literature regarding the incidence of failed intubation in the parturient and how obesity may impact intubation difficulty.
  4. Describe current timing and dosing recommendations for antibiotic prophylaxis for cesarean delivery and strategies to minimize wound infections.

CASE: A 25-year-old morbidly obese (body mass index (BMI) = 52 kg/m2) G1 P0 patient at 37 + 3 days gestational age, with no previous prenatal care, is being admitted to the labor and delivery floor for spontaneous rupture of membranes.

The patient’s vital signs are:

Pulse = 88 bpm
BP = 145/97
O2 saturation on room air = 97%
Temperature = 37 degrees Celsius.

The patient has told the nurse that she is otherwise healthy, other than “I am just big, that is all.”

According to the World Health Organization (WHO) classification of obesity, a pre-pregnancy BMI of 34.5 kg/m2 would be considered which of the following categories:

With a BMI of 52kg/m2, this patient is at risk of all of the following labor complications EXCEPT:

Considering the patient received no prenatal care, what information would you deem most important to know about this patient in order to properly assess her? (Try to list 5-10 maternal/obstetric history, physical exam, or laboratory findings)

  1. Maternal vitals
  2. Fetal heart tracings
  3. Airway exam
  4. Fetal presentation
  5. Anesthetic history (including previous intubation)
  6. Obstetric history
  7. Medical history (including allergies)
  8. Preeclampsia labs (platelets, LFTs)
  9. Vascular access
  10. Blood glucose level

The American Society of Anesthesiologists and the American College of Obstetricians and Gynecologists both recommend preoperative anesthetic assessment of morbidly obese patients prior to their delivery for anesthetic planning.12,13 Unfortunately, this patient did not receive prenatal care.

Presuming the glucose has been poorly controlled during her pregnancy, this patient’s fetus is at an increased risk of which of the following conditions:

According to ACOG recommendations, at what estimated fetal weight should a patient with gestational diabetes be given the option for a scheduled cesarean delivery compared to a vaginal delivery?

You would like to examine the patient. What are the key components of your exam?

  1. Airway (Mallampati classification, thyromental distance, cervical range of motion, mouth opening, circumference of neck, ability to prognathate)
  2. Back examination
  3. Cardiac exam
  4. Lung exam
  5. Edema in lower extremities
  6. IV check (what gauge and flow)

 

Which one of the following items most predicts difficulty in epidural placement for obese patients?

What difficulties and complications are more common during epidural placement in an obese patient relative to a non-obese parturient?

According to the literature, morbidly obese patients can have the following problems when neuraxial anesthesia is performed(17)

Difficulties:

  1. More difficulty determining midline or palpating landmarks (require more passes and longer placement times)
  2. Subcutaneous fat pockets can produce “false loss”
  3. May require longer Tuohy needle or spinal needle due to depth of epidural space (11-15cm needles)
  4. Replacement rate may be higher due to catheter migration due to excess movement of skin and subcutaneous tissue
  5. Increased epidural failure rate
  6. More difficult to position the patient due to habitus
  7. Sitting position for epidural placement may increase difficulty of externally monitoring fetal heart rate

Complications:

  1. Increased risk of accidental dural puncture
  2. Increased risk of accidental epidural venous puncture
  3. Failed analgesia requiring a repeat procedure

In order to set proper expectations with patients and be realistic, it is necessary to discuss how her obesity puts her at increased risk for complications and may require extra monitoring.  It should be explained that early epidural placement is recommended as it may take longer to achieve, and she and her baby may be at higher risk of complication if general anesthesia with endotracheal intubation is necessary.18

 

What special equipment should or might you have available to take care of a morbidly obese parturient in the operating room (OR)?

  1. OR bed that accommodates bariatric patients
  2. Longer spinal and/or epidural needle
  3. Advanced airway equipment
  4. Positioning ramp or blankets
  5. Large Blood Pressure cuffs
  6. Ultrasound for neuraxial placement or IV access
  7. Arterial line if unable to get accurate noninvasive BP readings

The patient is positioned in the operating room, and after 40 minutes and the use of ultrasound, the obstetric anesthesia providers are unable to successfully place an epidural catheter.  The patient is frustrated and states, “Enough, I just want to be put to sleep.” At the same time, the fetal heart tones become concerning with multiple late decelerations. You make the decision to proceed with general anesthesia.

What physiological and anatomical factors make pregnant airways more challenging than nonpregnant peers?

Many factors make the pregnant airway more challenging.19-20

  1. Increased weight gain during pregnancy
  2. Increased anterior-posterior diameter of the chest due to progesterone relaxation of the intercostal ligaments – results in misalignment of the oral, pharyngeal, and tracheal axes
  3. Increased oxygen consumption leads to more rapid oxygen desaturation
  4. Increased breast mass – may impede placement of laryngoscope (necessitating use of short handle laryngoscope)
  5. Edema of the upper airway due to pregnancy– narrowing upper airway
  6. More friable tissues and blood vessels due to progesterone influence
  7. Progressive swelling during labor21

In addition, her morbid obesity increases her likelihood of undiagnosed obstructive sleep apnea, which may make emergency mask ventilation as well as intubation more difficult.

Historically, general anesthesia has been considered to be much more dangerous than regional anesthesia. Overall, general anesthesia is relatively safe for the parturient.  In a review of anesthesia-related 1985-2003 maternal deaths in Michigan, Mhyre et al. demonstrated that maternal deaths in the peripartum period were more associated with airway obstruction and hypoventilation in obese patients following extubation and general anesthesia emergence rather than during intubation. This may indicate that postoperative monitoring of immediately postpartum patients who received general anesthesia is an important part of safe care.5. Some evidence suggests that video laryngoscopes may have a role in obstetric intubations and improve outcomes.20

How would you anticipate that the patient’s obesity would impact her planned intubation?

  1. Obesity has been associated with increasing difficulty with laryngoscopy
  2. Obesity, like pregnancy, decreases the overall FRC (both RV and ERV are decreased), and therefore, the patient will have less oxygen reserve than non-obese peers due to the upward pressure on the diaphragm due to the panniculus.
  3. Increasing tissue mass increases oxygen consumption, which will result in faster desaturation with apnea
  4. Arterial blood gas demonstrates more hypoxemia in obese patients when compared to non-obese
  5. Obesity is associated with OSA and may result in difficult mask ventilation.

 

Which one of the following statements is TRUE regarding antibiotic administration for cesarean deliveries?

This patient is at high risk for subsequent development of wound infection. Which of the following strategies is effective in reducing wound infections for obese patients?

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