Anesthesiology

Difficult Airway in Pregnancy

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What the Anesthesiologist Should Know before the Operative Procedure

Because of the dynamic nature of the labor floor, managing the difficult airway in pregnancy is a fluid concept. Strategies range from avoidance of airway instrumentation (and maintenance of native respiration) to securing the airway in an awake, highly controlled fashion. In all circumstances, multiple back-up plans must be formulated and able to be rapidly instituted.

Involved anesthesia practitioners should be well versed in the American Society of Anesthesiology (ASA) Practice Guidelines for Management of the Difficult Airway, the available airway equipment and skilled personnel, and the mechanism for securing a surgical airway. All members of the multidisciplinary team should be made aware of patients on the labor floor with difficult airways. A clearly articulated plan, ideally developed in advance, will improve clinical outcomes.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

The American Congress of Obstetricians and Gynecologists (ACOG) Guidelines state that delivery should (ideally) begin within 30 minutes of the decision to proceed with a cesarean delivery. However, caution should be exercised in parturients with difficulty airways as maternal health takes precedence over fetal well-being.

The following algorithm may be used to guide anesthetic decision-making:

I. If the mother already has an epidural catheter in situ, labor analgesia can be converted to surgical anesthesia by titrating additional local anesthetic (e.g., 10-20 mLs of 3% 2-chloroprocaine or 2% lidocaine with epinephrine and bicarbonate). In the case of the patient with a known difficult airway:

a) Every effort should be made to place the epidural catheter and test it early in labor.

b) The dosing of an epidural in a patient should be done in an incremental, monitored fashion with rescue airway devices nearby EVEN IN THE EVENT OF FETAL DISTRESS.

II. If no epidural catheter is in place, the following should be considered:

a) Awake direct laryngoscopy (i.e., the "awake look") with minimal topicalization and sedation to assess whether the Grade view is favorable enough for a rapid sequence induction (RSI) versus an awake fiberoptic (FOB) intubation. This technique can also be done with video laryngoscopy (both the “awake look” and the eventually intubation). If there is a Grade I or II view, then proceed with rapid sequence induction. If not, then proceed with awake FOB or video laryngoscope intubation.

b) Awake FOB intubation from the outset. (Note: adequate topicalization will likely delay the start of surgery and, therefore, must be communicated to the obstetricians.)

III. If the unexpected difficult airway is encountered, then follow the principles of the ASA Difficult Airway Algorithm:

a) If the patient is desaturating, consider mask ventilation or LMA insertion while either preparing for the next intubation attempt or planning to awaken the parturient and delay surgery.

b) If the goal is to proceed with surgery, then consider using video laryngoscopy if not already employed.

c) If LMA or other supraglottic airways are used during the surgery, be sure to clearly communicate to the obstetricians that the patient is at increased risk for aspiration and would benefit from rapid delivery with a minimum of visceral stimulation, (i.e. no exteriorization of the uterus after hysterotomy, if feasible). Note: The use of cricoid pressure with an LMA may limit ventilation and remains controversial.

1) Consider using a fiberoptic scope or anitree exchange catheter (Cook Medical) to intubate through the LMA. If not using an "intubating LMA" it may be difficult to remove the LMA without dislodging the ETT, so consider leaving both in place (but deflated) until the case is over.

Alert the emergency surgical airway back-up personnel BEFORE they are needed. If you wait until they are actually needed, it will be too late.

Elective: These patients should be NPO for solids for at least 6-8 hours and for clear liquids a minimum of 2 hours prior to planned surgery. It may be acceptable to delay elective surgery on patients with difficult airways (after appropriate discussion with the obstetric providers), if additional preoperative information, such as prior anesthetic records or pertinent airway assessments by other providers, is needed.

2. Preoperative evaluation

The most common preoperative issues that are concerning for difficult airway in pregnancy, include:

  • History of difficult intubation per anesthetic record or patient report. Physical evidence of broken teeth, oral trauma, or prolonged hoarseness after prior intubation.

  • Physical exam findings consistent with difficult intubation or mask ventilation, including short thick neck (short thyromental distance), protruding upper teeth, poor neck extension, small mouth opening, high Mallampati score, or inability to sublux mandible over maxilla (“upper lip bite test”).

  • History of head or neck pathology, radiation therapy, or cosmetic surgery.

  • Obesity: not all obese patients have difficult airways with an unfavorable Mallampati classification. However it is important to ascertain if they have sleep apnea or a short thick neck.

Any pregnant patient with significant comorbid disease limiting activities of daily living should undergo pre-delivery anesthesia consultation. A multidisciplinary conversation that includes the anesthesia, obstetric, nursing, and neonatal team members should occur to outline the challenges and plans for her delivery.

Delaying surgery may be indicated if patients with or without known difficult airway demonstrate these symptoms:

  1. new or worsening difficulty breathing

  2. hoarseness or other change in voice

  3. trismus

  4. swallowing difficulties

  5. inability to lay flat

Remember, a decompensating mother puts the fetus at risk; in some cases, securing the airway prior to delivery (even if it means surgical airway intervention) may be prudent.

3. What are the implications of co-existing disease on perioperative care?

Safe management of the difficult airway in patients with acute and unstable cardiac disease can be complicated. Work-up should include:

a) Assessment of baseline maternal oxygenation via pulse oximetry, and if < 95%, consider arterial blood gas.

b) Evaluation of the underlying cardiovascular pathology. This can include:

  • 12 lead EKG (arrhythmia, ischemia, signs of right heart strain)

  • ± Holter monitor, if symptomatic arrhythmia

  • Echocardiography, if valvular abnormalities are suspected

  • Cardiac catheterization is rarely indicated

Routine cardiac testing (e.g., EKG, echocardiogram) of pregnant patients with or without difficult airway is not recommended.

Monitoring goals

In general, for patients with symptomatic cardiac disease, the goal of perioperative management is to minimize cardiac demand and maximize oxygenation throughout intubation and ventilation.

Maximize pre-oxygenation prior to induction (e.g., 3 minutes of normal respiration using 100% oxygen or 8 vital capacity breaths of 100% oxygen). During fiberoptic intubation, consider passive oxygenation via the fiberoptic bronchoscope port.

Consider arterial line to facilitate tight control of blood pressure and blood gas measurements.

For specific recommendations see chapter on Cardiac Disease During Pregnancy.

b. Cardiovascular system:

See above.

c. Pulmonary:

Pulmonary/airway anomalies

The normal physiologic changes of pregnancy include increased oxygen consumption and decreased oxygen reserve. This puts the parturient at potential risk for respiratory compromise during hypoventilation or apnea. The most recent published investigations of maternal mortality both in the United States and the United Kingdom reveal that unrecognized, post-delivery respiratory arrest, particularly in obese parturients, is a leading cause of anesthesia-related morbidity and mortality.

Patients with pulmonary disease or airway abnormalities can be particularly challenging in the peripartum environment, and these patients are at increased risk for pulmonary dysfunction after general anesthesia.

Pulmonary or airway pathology that may impact the management of the difficult airway in pregnancy include:

  • Craniofacial dysmorphisms (e.g., acromegaly)

  • Obstructive sleep apnea

  • Oropharyngeal and neck tumors (±associated surgical resection or radiation)

  • Tracheal disease (stenosis or compressive goiter)

  • Vocal cord pathology (arthritis, paralyzed cord[s])

  • Other musculoskeletal jaw/neck pathology (e.g., TMJ or cervical spine disease)

  • Bronchospastic disease (e.g., asthma)

  • COPD

  • Restrictive (e.g., thoracic scoliosis)

  • Parenchymal disease (granulomatous—Wegener’s, TB)

It is crucial to understand the impact of the underlying disease on the ability to:

a) obtain a satisfactory mask airway

b) visualize the vocal cords

c) pass an endotracheal tube

d) oxygenate and/or ventilate

Preoperative evaluation of each patient’s airway should include:

a) a history of previous intubations, including review of prior anesthesia records, when feasible

b) determination of Mallampati/Samsoon Classification (I-IV)

c) anatomical characteristics consistent with difficult intubation/mask airway, such as:

  • Short, thick neck

  • Receding mandible

  • Protruding maxillary incisors

d) review of relevant scans, previous laryngoscopies, consultations with pulmonologists and otolaryngologists if indicated.

Be aware that during labor, the oropharyngeal volume is decreased due to soft tissue swelling, potentially creating less ideal intubating conditions.

Depending on the underlying pathology, perioperative risk reduction strategies include:

a) neuraxial rather than general anesthesia to avoid airway instrumentation.

b) the use of neuraxial rather than intravenous narcotics postpartum to decrease the risk of respiratory depression. High-risk patients, particularly those with sleep apnea, should be closely monitored.

c) the continuation of maintenance medications such as bronchodilators, antibiotics, and steroid therapy. If the patient has an acute exacerbation of pulmonary disease, and the delivery can be delayed, then her pulmonary status should first be optimized.

d) coordination with relevant subspecialists.

d. Renal-GI:

GI

All pregnant patients are considered to have a "full stomach" (i.e., they are theoretically at increased risk for aspiration). Therefore, it is preferable to allow native respiration under neuraxial anesthesia which should avoid depressing the patient’s airway reflexes.

Perioperative evaluation

Asking patients about symptomatic reflux and assessing their NPO status can help to identify who should receive additional aspiration prophylaxis. Patients with obstructive gastrointestinal pathology are particularly concerning for potential aspiration of gastric contents.

Peripartum risk reduction strategy

Prophylaxis:

a) All parturients typically receive a nonparticulate antacid (e.g., sodium citrate) prior to receiving analgesia or anesthesia. Patients with symptomatic reflux may also be given metoclopramide (promotility) or an H2-receptor blocker (e.g., ranitidine).

b) Oral intake is restricted during labor to clear liquids.

c) In pregnant patients with additional obstructive gastrointestinal pathology, consider decompressing the stomach prior to induction of general anesthesia.

e. Neurologic:

Acute neurologic issues that compromise the health of the mother (e.g., subarachnoid hemorrhage, eclampsia, stroke) may also affect the fetus. If possible, stabilize the mother first. If cesarean delivery is necessary, the parturient should be assessed for contraindications to neuraxial anesthesia such as:

a) compromised level of consciousness and/or loss of airway reflexes

b) significant risk of herniation from dural puncture.

Preoperative brain scans and consultation with a neurologist or neurosurgeon are indicated in these cases.

If such a patient possesses a difficulty airway, then neuraxial anesthesia should be considered if feasible. The airway should be secured in a manner that minimizes hypoventilation or valsalva. A smooth transition from native respiration to intubation (e.g., topicalization, mild sedation, and awake fiberoptic intubation) is ideal.

f. Endocrine:

Two common endocrine pathologic conditions that are concerning for difficult airway are diabetes mellitus (DM) and obesity. Obesity and DM also result in multiple medical comorbidities. DM may increase the risk of aspiration due to gastroparesis. Obesity can increase the difficulty of securing the airway because redundant supraglottic tissue can obscure the view of the glottis. Both the BMI and the distribution of adipose tissue (central vs peripheral) contribute to airway concerns. Video laryngoscopy can optimize the view of critical structures in situations involving increased soft tissue. Both obesity and pregnancy reduce functional residual capacity and increase oxygen demand, so even with excellent pre-oxygenation the patient will desaturate rapidly (i.e., less than 1 minute). Some providers would recommend considering using a video laryngoscope for the first attempt at intubation.

Pregnant patients with diabetes should be asked about:

a) peripheral neuropathy

b) cardiovascular disease (e.g., history of chest pain with exertion, hypertension)

c) symptomatic gastric reflux

d) retinopathy

e) joint stiffness, especially in the cervical spine and jaw

Pregnant patients with obesity should be asked about:

a) obstructive sleep apnea

b) symptomatic gastric reflux

c) cardiovascular disease (e.g., history of chest pain with exertion, hypertension)

d) respiratory function

e) overall functional status

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Musculoskeletal disease

Acute head or neck trauma can cause a straight forward airway to become difficult, or a known difficult airway to become even more challenging. If trauma has occurred, the patient’s head and neck should be imaged for the presence of facial fractures, neck instability or intracranial trauma. Ligamentous injury should be ruled out via clinical exam. If imaging is not available, then oral intubation with neck immobilization is indicated. In rare cases, if the spine and the airway are intact and coagulopathy is not suspected, then neuraxial anesthesia may be feasible.

Hematologic disorders

Thrombocytopenia

There are no randomized controlled trials to determine the minimum platelet count required for the safe conduct of neuraxial anesthesia (in terms of minimizing the risk of epidural hematoma). Many obstetric anesthesia practitioners place spinals and epidurals in patients with ≥75- 80K platelets (e.g., gestational thrombocytopenia, idiopathic thrombocytopenia, preeclampsia) in the absence of other contraindications. Ultimately, the risk of losing the airway must be balanced against the risk of epidural hematoma in these patients.

Coagulopathy

See the published American Society of Regional Anesthesia (ASRA) Guidelines regarding appropriateness of neuraxial anesthesia in the setting of anticoagulants.

Since coagulation factors are acute phase reactants which increase during pregnancy, most patients with Type 1 Von Willebrand’s disease correct during pregnancy and can therefore have neuraxial anesthesia without increased risk of epidural hematoma.

Patients who are anticoagulated with low molecular heparin are often switched to unfractionated heparin at 36 weeks to facilitate peridelivery monitoring of coagulation status and neuraxial anesthesia. In most cases, the anticoagulant is held prior to admission for delivery, and depending on the dose and time window, an aPTT may be indicated prior to administration of neuraxial anesthesia. Consult a hematologist for management of specific coagulopathies.

4. What are the patient’s medications and how should they be managed in the perioperative period?

In general, patients should continue their chronic medications as prescribed, assuming they are safe in pregnancy.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Insulin should be managed per obstetric protocol. Particulate or chalky liquid medications (e.g., Milk of Magnesia or Tums) are typically replaced with clear liquid preparations (e.g., sodium citrate) or pills.

i. What should be recommended with regard to continuation of medications taken chronically?

N/A

j. How to modify care for patients with known allergies

N/A

k. Latex allergy - If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

Patients should be on standard latex precautions. Modern airway equipment is typically latex-free but providers should verify with their equipment manufacturers prior to use.

l. Does the patient have any antibiotic allergies - Common antibiotic allergies and alternative antibiotics

N/A

m. Does the patient have a history of allergy to anesthesia?

Patients with known difficult airway and allergies to anesthetics should be identified prior to delivery.

i. Malignant hyperthermia

Documented: If malignant hyperthermia (MH) is documented in the patient or her first degree relative, then it is necessary to avoid triggering agents such as succinylcholine and volatile anesthetics.

a) Designate a dedicated operating room with a "clean machine" (without traces of triggering agents) while the patient is on the labor floor. (Commercially available charcoal filters have been shown to reduce the levels of volatile anesthetic agents to trace levels [<5ppm] after 90 sec of 10 L/min flow [to flush the machine] and the placement of commercially available activated charcoal filters.)

b) In the setting of a difficult airway, consider an awake FOB intubation with IV sedation. If rapid sequence induction is deemed appropriate, use a non-depolarizing muscle relaxant (e.g., rocuronium) with appropriate induction agent for intubation, or intubate using an induction agent and remifentil (4-5 mcg/kg) because of its shorter duration of action.

c) Ensure an MH cart is available (with adequate amounts of dantrolene for obese parturients).

d) Consider early labor epidural catheter placement to avoid general anesthesia, if possible.

ii. Muscle relaxants

If patient has allergy to muscle relaxants, then consider:

a) Placement of an epidural catheter early in labor

b) Utilization of a different class of muscle relaxants (e.g., amino steroid vs benzylisoquinoline)

iii. Local anesthetics

If patient has allergy to local anesthetics:

A) If ester local anesthetic allergy:

1) If allergy to preservative, use preservative-free (most modern formulations)

2) If PABA allergy, use amide local anesthetic (e.g., lidocaine or bupivacaine)

B) If amide local anesthetic allergy:

1) Use ester local anesthetic (e.g., 2-chloroprocaine)

Preservative-free Demerol (1 mg/kg) may be used for spinal anesthesia for cesarean delivery in the rare patient with allergy to amide and ester local anesthetics.

5. What laboratory tests should be obtained and has everything been reviewed?

Healthy patients without significant co-morbidities typically do not require routine blood testing. A platelet count is usually checked in patients with suspected ITP, gestational thrombocytopenia, or severe preeclampsia/ HELLP syndrome before a neuraxial anesthetic is initiated, or an epidural catheter is removed. Coagulation tests may also be indicated in some patients with thrombocytopenia or who are prescribed unfractionated heparin, but these tests are not part of routine screening for all obstetric patients. A baseline pregnancy vWD screen in patients with known von Willebrand’s disease is usually obtained in the third trimester. Patients with preeclampsia, diabetes, or metabolic disorders will also have electrolytes drawn.

Hemoglobin levels: Normal value in pregnancy at term is approximately 11.6 g/dL

Electrolytes: Of note, upper limit of normal for Cr at term pregnancy is 0.6 mg/dL

Coagulation panel: Expect normal PT, PTT, INR.

Imaging: As above. If there are pulmonary symptoms such as acute or chronic persistent cough, consider chest CT and pulmonary consultation. If glottic or subglottic pathology, consider bronchoscopy, ENT consultation, and possible neck CT.

Other tests: Thyroid function tests (rule out Grave’s disease). Note: Thyroid-binding globulin increases during first trimester but free T3 and T4 do not change.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

While neuraxial anesthesia is the preferred anesthetic type, even if neuraxial anesthesia is used, the patient should be optimally positioned for a general anesthetic during cesarean delivery, should the need arise. Techniques that offload breast tissue from the neck are particularly helpful; these include reverse Trendelenberg, our preferred technique in which the patient is supported on the bed through the use of a removable footboard, and ramping with blankets or rolls underneath the patient’s shoulders to facilitate the "sniff position".

a. Regional anesthesia

If not contraindicated, neuraxial anesthesia is considered the anesthetic of choice for pregnant patients, especially those with a difficult airway.

Potential benefits:

a. Provides anesthesia while maintaining patient’s airway reflexes and native respiration.

b. The risk of failed intubation in obstetric general anesthesia is 1:390, roughly 50 times that of the general population. Per the most recent UK national audit project, the incidence of airway complications was one per 22,000 general anesthetics.

c. These techniques allow the use of long-acting neuraxial opioids that result in superior post-operative pain relief. However, if general anesthesia is used, consider a transversus abdominis plane (TAP) block to augment post-operative pain relief.

d. Several studies on obstetric patients have shown less blood loss during surgery with neuraxial versus general anesthesia.

e. Neuraxial anesthesia allows the mother to be awake during the operative delivery facilitating maternal / neonatal bonding and minimizes exposure of the fetus to anesthesia.

Potential disadvantages:

a. The airway is not secured prior to the start of surgery; if a problem arises and the airway needs to be controlled, the circumstances will be less optimal.

b. Attaining adequate regional anesthesia can delay the start of surgery.

c. There is a higher likelihood of breakthrough surgical pain with neuraxial than with general anesthesia.

d. Patients may refuse or not tolerate being awake during surgery.

e. Neuraxial anesthesia may be technically challenging, and requires adequate coagulation parameters.

Specific neuraxial techniques explored

Spinal

Potential advantages:

a. Quick onset of a dense block.

b. Relatively reliable block distribution, especially if hyperbaric medication is used.

c. Low risk of postdural puncture headache (PDPH) with small gauge, pencil-point needles.

Potential disadvantages:

a. No readily available route for re-dosing if "single-shot".

b. Risk of high or total spinal exists but is unlikely in the setting of no preexisting block and use of usual doses of hyperbaric medication.

Epidural

Early epidural catheter placement for labor analgesia and possible surgical anesthesia is recommended for patients with a potential difficult airway.

Potential advantages:

a. Is flexible and re-dosable.

b. Generally has less impact on maternal blood pressure than spinal anesthesia.

Potential disadvantages:

a. May have less dense visceral and sacral segment block.

b. Takes longer to achieve desired analgesia/anesthesia.

c. Higher likelihood of being unilateral or “patchy” than spinal anesthetic.

Combined spinal/epidural

Potential advantages:

a. Quick onset.

b. Dense, spinal block (see above).

c. Less likely to result in unilateral block.

d. Can augment sensory level with epidural medication if anesthesia insufficient.

Potential disadvantages:

a. Can be associated with fetal bradycardia (although not with increase in need for cesarean delivery), and/or maternal itching.

b. Can be more technically difficult to perform than "single shot" spinal or conventional epidural.

Continuous spinal

Advantages and disadvantages as articulated for spinal, except:

a. Advantage of being titratable and re-dosable.

b. Disadvantage of having a significantly increased risk of PDPH. If a 17G needle is used, risk may be 55-80%.

Peripheral nerve block

Peripheral nerve blocks will not provide adequate analgesia for labor or anesthesia for cesarean delivery.

Transversus abdomininus plane (TAP) block is becoming increasingly popular as an adjunct for post cesarean delivery pain management in patients who can or do not receive neuraxial opioid.

Potential benefits:

This is an easily performed ultrasound-guided block with low risk of complications.

Potential disadvantages:

This technique is not as effective for pain relief as long-acting neuraxial narcotics; block only lasts 6 to 12 hours, unless a catheter is placed. There does not appear to be significant, incremental benefit beyond the first few hours if TAP block is used in conjunction with neuraxial opioids in healthy patients after cesarean delivery.

General anesthesia

There are several additional factors that contribute to the challenge of the pregnant airway.

1. The initial Mallampati/Samsoon Classification and the pharyngeal volume of a pregnant patient changes in a nonfavorable direction during pregnancy and labor (Mallampati score increases and pharyngeal volume decreases).

2. There is a strong correlation between structures seen on oropharyngeal assessment (in addition to Mallampati-Samsoon classification, such as: short neck, receding mandible, protruding maxillary incisors) and the Grade view on intubation. Of 1500 patients in one study, there were two failed intubations (both survived).

a) In the absence of additional risk factors, Mallampati-Samsoon Class I and II had a low incidence of difficult intubation.

b) In general, patients with additional anatomic challenges (e.g., short, thick neck, receding mandible) had a higher probability of difficulty intubation than those with increased Mallampati-Samsoon score alone.

3. Gastric emptying decreases during labor, thus increasing the chance that the pregnant woman will have food in her stomach at the time of presentation for unscheduled cesarean delivery.

4. Increased intragastric pressure and decreased esophageal sphincter tone (theoretically) increases the chance of maternal aspiration.

5. Parturients often present for general anesthesia when their most sensitive end-organ, the fetus, is already compromised. Therefore, they have a high oxygen demand and a minimal oxygen reserve.

General endotracheal anesthesia

Potential benefits:

1. Provides secure airway, the best protection against aspiration although not 100%.

2. Rapid onset of anesthesia once the airway is secure.

3. Respiratory function can be optimized with ventilatory parameters and PEEP.

Potential disadvantages:

1. May have to delay case to secure airway in case of difficult intubation.

2. May "lose the airway," leading to maternal hypoxia and morbidity/mortality.

3. Lower 1-minute Apgar scores due to trans-placental passage of anesthetic agents.

4. Cesarean deliveries are high risk cases for maternal awareness under general anesthesia.

5. Increased bleeding due to uterine atony (especially if MAC of volatile anesthetic >0.5-0.75 vol %).

6. Decreased initial maternal/fetal bonding because of the mother’s sedation.

7. Potentially less adequate post-operative pain management (consider TAP block before extubation).

Airway issues:

1. Optimize pre-oxygenation. Ideally, 8 vital capacity breaths of 100% FIO2 produce better denitrogenation than 3 minutes of regular tidal volume breathing.

2. Cricoid pressure: As there is no conclusive evidence that this maneuver prevents clinically significant aspiration, it can be eliminated if laryngeal view is obstructed.

3. A difficult airway cart should be immediately available in all anesthetizing locations.

Potential strategies:

1. Awake direct laryngoscopy or video laryngoscopy may be performed to ascertain if posterior arytenoids or vocal cords can be visualized. If the structures can be visualized, proceed with asleep rapid sequence induction. If not, proceed with an awake FOB or video laryngoscopic oral intubation. Avoid nares due to risk of mucosal bleeding.

2. Awake FOB or video laryngoscopy can be done using a variety of different sedation and topicalization techniques. Note: since there is no need to align axes visually, the video laryngoscopes improve the view in patients with an anterior larynx. They are especially useful in pregnant patients where the difficulty is mainly due to swollen or floppy soft tissue.

3. Intubating LMA: Useful if unexpected difficult airway and failed intubation. Suggest confirming ETT placement with FOB before removing LMA. May also leave the deflated LMA in place to have a way to ventilate the patient if needed after extubation.

4. Asleep fiberoptic intubation; may consider using a laryngoscope to improve view.

If going to the OR with a known difficult airway, strongly consider notifying your emergency surgical airway back-up team in case of difficulty.

Failed intubation

It is critical to institute the ASA Difficult Airway algorithm in the event of an unanticipated difficult airway, or failed attempt at securing a known difficult airway. If you are unsuccessful at intubating the patient but are able to mask ventilate or place an LMA, do you proceed with the surgery?

A single published study of elective cesarean deliveries under LMA reported no complications, including aspiration. Patients with BMI >30 and symptomatic reflux were excluded. The patients were also NPO and not in labor.

In this situation, the choice is either to allow the surgeons to proceed with the LMA in place, or wake the patient up and risk fetal injury or death. If the patient is awakened, the case can proceed after either an awake surgical airway, awake fiberoptic intubation, or regional anesthesia. If the decision is to proceed with the case under a mask or LMA, consider:

a) Clear communication with surgeons and nurses.

b) Asking the most experienced surgeon to operate to facilitate the shortest surgical time.

c) Request the obstetricians avoid exteriorization of uterus in an attempt to minimize nausea and vomiting.

The decision to proceed or not with surgery after being unable to intubate but able to ventilate (using either a supraglottic device or face mask) is very difficult and is situation specific. It will be based on a balancing of: the maternal condition, fetal condition, urgency of the case, experience of the anesthesia and surgical provider, aspiration risk, and quality of the airway obtained.

6. What is the author’s preferred method of anesthesia technique and why?

We prefer regional anesthesia as the technique of choice in almost all situations on OB. As mentioned above regional allows for: avoidance of the pregnancy airway (increased incidence of difficult intubation compared with the general population), less blood loss compared with general anesthesia, less fetal effects of anesthesia, and increased maternal bonding with the infant.

What are the most common intraoperative complications and how can they be avoided/treated?

Prompt identification and robust planning for control of the difficult airway in a parturient can minimize the following potential intraoperative airway complications:

  1. Hypoxemia with end-organ damage (e.g., anoxic encephalopathy)

  2. Aspiration

  3. Airway trauma (e.g., missing teeth, soft tissue or vocal cord damage, esophageal perforation)

  4. If there is a need for emergency tracheostomy, then additional damage is possible (e.g., thyroid injury, tracheal stenosis, recurrent laryngeal nerve)

  5. Pneumothorax

  6. Subcutaneous emphysema

  7. Postoperative airway edema and respiratory insufficiency

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

Patients with known difficult airways should, at minimum, meet the usual criteria for extubation, including:

a) Return of adequate neuromuscular function and airway reflexes,

b) The ability to follow commands, and

c) Return of adequate respiratory function and pain control.

Additional considerations for these patients include availability of airway equipment (including video laryngoscopes, fiberoptic scopes, and laryngeal mask airways) and skilled personnel should the patient need to be reintubated. Patients with known airway trauma or multiple attempts at intubation have a high likelihood of glottic and supraglottic edema. This should be investigated before attempting to extubate, using a direct or video laryngoscopic view or a "leak" test where the cuff of the endotracheal tube is deflated to assess whether there is adequate airway caliber around the in-situ endotracheal tube. An alternative to the leak test, used by the authors, is to use direct or video laryngoscopy to assess the glotic opening and evaluate for swelling. Some practitioners will extubate with an airway exchange catheter in place in the trachea to facilitate reintubation if needed. If airway edema or trauma is suspected, consultation with an otolaryngologist and treatment with perioperative steroids may be indicated. Finally, these patients should be recovered in a closely monitored setting for several hours after extubation as they may be at increased risk for respiratory compromise. If the patient is deemed unfit for extubation, then she should remain intubated, with the head of the bed elevated to facilitate reduction of airway edema, and transferred to an acute care setting where she can be closely monitored. The patient can then be extubated in a controlled fashion after confirmation that the airway is more favorable.

c. Postoperative management

N/A

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