Airway problems in pregnancy

Uma Munnur, MD; Ben de Boisblanc, MD; Maya S. Suresh, MD

T he management of a difficultairway in an obstetrical pa-tient is especially challengingduring an acute obstetrical

emergency and can be an anesthesiolo-gist’s worst nightmare (1). Failure to ap-propriately manage a difficult or failedintubation increases the risk of hypox-emic cardiopulmonary arrest and/or pul-monary aspiration, resulting in a highprobability of maternal morbidity andmortality. A timely preoperative airwayevaluation, recognition of factors associ-ated with or predisposing to difficult air-way, and appropriate preparation fordealing with both anticipated and unan-ticipated difficulties of airway manage-ment are essential to reduce anesthesia-related maternal and fetal morbidity andmortality (2).

Several factors tend to evoke appre-hension in even the most competent an-esthesiologist when dealing with a preg-nant woman. The most important factorsare pregnancy-related altered anatomyand physiology impacting anestheticmanagement, the urgent nature of theobstetrical practice, leading to limitedtime for adequate anesthetic preparation,and the potential risk of impacting bothmother and baby (3).

Anesthesia-Related MaternalMortality

Even though anesthesia-related ma-ternal mortality rates have improved inthe United States, anesthesia still re-mains prominent amongst the leadingcauses of maternal mortality; it is theseventh leading cause of maternal mor-tality in the United States. The other sixleading causes of maternal mortality areembolism, hypertensive disorders, hem-orrhage, infection, cardiomyopathy, andcerebrovascular accident (4). General an-esthesia is more likely to be associatedwith maternal mortality than is regionalanesthesia in the obstetrical patient, forthe following reasons: airway manage-ment tends to be more difficult in preg-nant patients; general anesthesia is cho-sen in emergency surgeries, particularly

when there is minimum time allowed foradequate preoperative evaluation; in con-version of regional anesthetic to generalanesthesia, secondary to failed regionalanesthesia, hemorrhage, or prolongedsurgery, the patient is not usually placedin an optimal position for intubation;there is increased usage of regional anes-thesia in obstetrics; residents lack expe-rience because of minimal exposure togeneral anesthesia for cesarean sections,resulting in decreased airway manage-ment skills for obstetrical patients.

The Closed Claims Analysis of theAmerican Society of Anesthesiologists(ASA) revealed that respiratory events ac-counted for the single largest class ofinjury (5). The case studies included bothgeneral anesthesia and regional anesthe-sia. Three mechanisms accounted fornearly three-quarters of the cases: inade-quate ventilation (38%), esophageal intu-bation (17%), and difficult intubation(18%). Care was judged substandard in76% of the claims for adverse respiratoryevents (6). According to the closed claimsstudy by Chadwick and colleagues, diffi-cult tracheal intubation and esophagealintubation comprised 23% of damagingevents associated with obstetrical generalanesthesia (7). Complications of anesthe-sia-related deaths due to airway manage-

From the Department of Anesthesiology (UM)(BdeB) and Division of Obstetric & Gynecology Anes-thesia (BdeB), Baylor College of Medicine, Houston, TX;and Departments of Medicine and Physiology, Louisi-ana State University Health Sciences Center (MSS),New Orleans, LA

Address requests for reprints to: Uma Munnur, MD,Department of Anesthesiology, Baylor College of Med-icine, Houston, TX 77030. E-mail: umunnur@bcm.tmc

Copyright © 2005 by the Society of Critical CareMedicine and Lippincott Williams & Wilkins

DOI: 10.1097/01.CCM.0000183502.45419.C9

Objectives: To provide a current review of the literature re-garding airway problems in pregnancy and management.

Background: Obstetrical anesthesia is considered to be a high-risk practice that exposes the anesthesiologist to increased med-icolegal liability. Anesthetic management of a parturient is achallenge because it involves simultaneous care of both motherand baby. Failure to appropriately manage a difficult or failedintubation increases the risk of hypoxemic cardiopulmonary ar-rest and/or pulmonary aspiration, resulting in a high probability ofmaternal morbidity and mortality.

Data: Anesthesia is the seventh leading cause of maternalmortality in the United States. Anatomic and physiologic changesduring pregnancy place the parturient at increased risk for airwaymanagement problems. It is essential to perform a thoroughpreanesthetic evaluation and identify the factors predictive ofdifficult intubation. Airway devices such as the laryngeal mask

airway, ProSeal, intubating laryngeal mask airway, Combitube,and laryngeal tube are described and have been used duringfailed intubation in pregnant patients.

Conclusion: Teamwork between an anesthesiologist and anobstetrician is absolutely essential for the safety of both themother and baby. Most of us tend to agree that airway emergen-cies have a way of occurring at the worst possible times. It isessential that all anesthesia care practitioners must have apreconceived and well thought-out algorithm and emergencyairway equipment to deal with airway emergencies duringdifficult or failed intubation of a parturient. (Crit Care Med2005; 33[Suppl.]:S259 –S268)

KEY WORDS: Pregnancy; difficult intubation; preeclampsia; ma-ternal mortality; difficult airway algorithm; general anesthesia;regional anesthesia; failed intubation; cesarean section; labor

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ment problems included aspiration ofgastric contents, intubation problems,esophageal intubation, inadequate venti-lation, and respiratory failure.

Anatomic and PhysiologicChanges During Pregnancy

There are a number of anatomic andphysiologic changes during pregnancythat result in difficult airway and pose athreat to difficult or failed intubation (Ta-ble 1). Capillary engorgement of the mu-cosa throughout the respiratory tractcauses swelling of the nasal and oralpharynx, larynx, and trachea, resulting indifficulty with nasal breathing, epistaxis,and voice changes (8, 9). Elevated estro-gen levels and an increase in blood vol-ume associated with pregnancy may con-tribute to the mucosal edema (10). Thesechanges may be markedly exacerbated bya mild upper respiratory tract infection,fluid overload, or the edema associatedwith preeclampsia, which can lead to aseverely compromised airway (11–13).

Pregnancy is associated with a shift inthe position of the stomach caused by thegravid uterus, which also changes theangle of the gastroesophageal junction,resulting in incompetence of the gastro-esophageal pinchcock mechanism (14).The progesterone-mediated smooth-muscle relaxant effect on the gastrointes-tinal mucosa, along with the anatomicchanges secondary to the gravid uterus,places the parturient at risk for regurgi-tation and pulmonary aspiration. Loweresophageal sphincter tone is decreased,allowing gastric reflux and heartburnduring pregnancy (15). Studies haveshown that gastric emptying is prolongedduring labor (16, 17). Therefore, the par-turient is prone to silent regurgitation,active vomiting, and aspiration duringgeneral anesthesia or impaired con-sciousness (18). All parturients undergo-ing an anesthetic for cesarean section areconsidered at risk for pulmonary aspira-tion and should receive aspiration pro-phylaxis preoperatively.

A parturient gains 20 kg or more dur-ing pregnancy. The weight gain resultsfrom the increasing size of the uterus and

fetus, increased volumes of blood and in-terstitial fluid, and deposition of fat.There is also a significant increase inbreast size during pregnancy. Increasedweight gain during pregnancy and largebreast size can cause difficulty with intu-bation. Proper positioning, with blanketsunder the shoulders, and use of a short-handled laryngoscope can minimize thehazards of difficult laryngoscopy.

Airway Assessment

Most airway catastrophes occur whenairway difficulty is not recognized beforeinduction of anesthesia. Timely evalua-tion of the parturient’s airway and ade-quate preparation to deal with the airwayin the nonemergent setting are helpful inavoiding airway catastrophes. Eighty-seven percent of emergency or urgentcesarean deliveries can be anticipated byregular evaluation of patients who areadmitted to the labor and delivery suite,thus allowing for early placement of afunctioning epidural and avoiding instru-mentation of the airway when the cesar-ean section is called or when the patientis committed to having a cesarean section(19).

There are a few simple preoperativebedside determinations that can be per-formed quickly to evaluate the airway in apregnant patient. These include but arenot limited to mouth opening, Mallam-pati class, thyromental distance, atlanto-occipital extension, and ability to pro-trude the mandible.

Mallampati Class

The relationship of the base of thetongue to the oropharyngeal struc-tures—uvula, tonsillar pillars, and fau-cial pillars—forms the basis of the Mal-lampati classification. Mallampatihypothesized that when the base of thetongue is disproportionately large in re-lation to the oropharyngeal cavity, theenlarged base of the tongue can obscurethe visibility of the tonsillar pillars anduvula (20) and result in difficulty withlaryngoscopy and intubation. Based onthe original Mallampati classification and

the modification by Samsoon and Young,there are four classes (21): class I, visu-alization of soft palate, uvula, and tonsil-lar pillars; class II, visualization of softpalate and base of uvula; class III, visual-ization of soft palate only; and class IV,visualization of only hard palate. Sam-soon and Young demonstrated that thereis significant correlation between theability to visualize pharyngeal structuresand ease of laryngoscopy (Fig. 1).

Cormack and Lehane evaluated the la-ryngoscopic view of the glottis and di-vided it into four grades (22) (Fig. 2):grade I � most of the glottis visible;grade II � only posterior portion of glot-tis visible; grade III � only epiglottis vis-ible; grade IV � epiglottis not visible.

A significant correlation has beennoted between Mallampati class and la-ryngoscopic view grade. Patients withclass I and II airways are almost alwayseasy to intubate and are associated withlaryngoscopic grade I and II views,whereas patients with Mallampati classIII and IV airways are associated withlaryngoscopic grade III and IV views (21).

Atlanto-Occipital Joint Extension

This extension is important in align-ing the oral, pharyngeal, and laryngealaxes during laryngoscopy. Normally theatlanto-occipital joint allows a 35-degreeextension of the head over the neck. Areduction in the extension of the jointcan cause difficulty with intubation.Complete atlanto-occipital joint immo-bility can compromise the view of glottisduring laryngoscopy. Sniffing position isachieved by moderate flexion of the neckon the chest and extension of the atlanto-occipital joint. With the patient in propersniffing position, the view of the larynx isless obscured by the tongue.

Thyromental Distance

This is defined as the distance fromthe chin to the notch of the thyroid car-tilage. The thyromental distance gives anestimate of the mandibular space and iseasy to measure either by a ruler or bynumber of finger-breadths. A measure-ment of �6.5 cm with no other anatomicabnormalities indicates easy intubation.A measurement of 6–6.5 cm indicatesthat laryngoscopy and intubation may bedifficult but most likely possible. If thedistance is �6 cm, laryngoscopy and in-tubation may be difficult or impossible.Mandibular space is an important predic-

Table 1. Anatomic and physiological factors affecting the obstetric airway

Upper airway edema Decreased functional residual capacityBreast enlargement Increased oxygen consumptionExcessive weight gain Increased risk of aspirationCephalad displacement of diaphragm Preeclampsia

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tor of difficult intubation because thetongue is displaced into this space duringlaryngoscopy.

Data suggest that the Mallampatiscore changes during gestation, with anincrease to class IV airway between 12and 38 wks of gestation. The increase inthe Mallampati score is secondary toweight gain during pregnancy (23). Thetrend toward a worsening Mallampatiscore is also thought to be due to in-creased pharyngeal edema and fatty infil-tration of pharyngeal tissue. During la-bor, parturients are susceptible todeveloping airway tissue edema as a re-sult of excessive intravenous infusion offluids, resulting in a lowering of the al-

ready decreased colloid osmotic pressure(24). The shift in the Starling forces re-sults in an exacerbation of airway edema,thus increasing the Mallampati class. Thebearing down efforts and Valsalva maneu-ver during labor also exacerbate the wors-ening of the Mallampati score (8), and itis recommended that the airway be reas-sessed before induction of general anes-thesia (25).

It is clear that no single airway assess-ment can reliably predict a difficult air-way. Nevertheless, preoperative predic-tors of difficult airway are essential tofacilitate the management of the airwayand to reduce the likelihood of adverseoutcomes. Predicting difficult airway en-

ables the anesthesia practitioner to im-plement proper care and thus avoid air-way catastrophes. Every pregnant patientwho will undergo an operative deliveryshould have a preanesthetic evaluationthat emphasizes the airway examinationas outlined by the ASA practice guidelines(26).

Rocke and colleagues conducted a pre-operative airway assessment and recordedthe potential risk factors for difficult in-tubation in 1,500 pregnant females un-dergoing elective and emergency cesar-ean sections under general anesthesia(27). The authors found a strong correla-tion between difficulty in visualizing oro-pharyngeal structures and subsequentdifficulty with tracheal intubation. Theassociated risk factors included shortneck (SN), protruding maxillary incisors(PMI), receding mandible (RM), and Mal-lampati class III and IV airways. The rel-ative risk of experiencing a difficult intu-bation in comparison with anuncomplicated class I airway assessmentwas as follows: class II, 3.23; class III,7.58; class IV, 11.3; SN, 5.01; RM, 9.71;and PMI, 8.0 (Fig. 3). Using the probabil-ity index and/or combination of risk fac-tors showed that with a combination ofeither class III or IV plus PMI, SN, andRM, the probability of difficult laryngos-copy was �90% (Fig. 4).

Occipito-atlanto-axial disease is asso-ciated with poor mandibular protrusion.Calder and colleagues (28) examined 253patients preoperatively before surgery forcervical spine disease. Mandibular pro-trusion was assessed by asking the patientto protrude the mandible as far as possi-ble. The degree of protrusion was classi-fied as follows: class A � the lower inci-sors can be protruded anterior to theupper incisors; class B � the lower inci-sors can be brought edge to edge with theupper incisors but not anterior to them;class C � the lower incisors cannot bebrought edge to edge.

The grade of glottic visibility was de-termined at direct laryngoscopy with useof the Cormack and Lehane classification.Class C protrusion was the only findingalways associated with difficult mask ven-tilation and intubation. Patients withclass A mandibular protrusion rarelyposed difficulty (28).(Fig. 5)

Preeclampsia and Airway-Related Changes

Patients with preeclampsia have nar-rower upper airways than normal preg-

Figure 2. Airway classification in relation to laryngoscopic view grading system. Adapted fromAnesthesia 1984; 39:1105; Anaesthesia 1987; 42:487; and Can J Anaesth 1985; 32:429.

Figure 1. Difficulty of intubation based on Mallampati classification. Adapted from Mallampati SR: Aclinical sign to predict difficult tracheal intubation: A prospective study. Can J Anaesth 1985; 32:429.

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nant women, secondary to significant tis-sue edema along with soft-tissuedeposition in the neck. Data show upperairway narrowing in preeclamptic pa-tients during sleep (29). Reduced plasmaproteins due to proteinuria and markedfluid retention (especially in the head andneck region) make the tongue larger andless mobile, causing more difficult iden-tification of landmarks in preeclampticparturients. In severe preeclampsia,edema of the face and neck should alertthe anesthesiologist to the possibility of adifficult intubation, whereas edema of thetongue may be an indication for immedi-ate airway compromise (8, 11, 30–32).

Preeclampsia, accompanied by soft-tissue edema and coagulopathy, compli-cates repeated attempts at direct laryn-goscopy, causing laceration and bleedingin the upper airway, thus complicatingthe management of a difficult airway(33). Upper respiratory infection can fur-

ther compromise the edematous airwayin preeclampsia (11. Marked upper airwayedema and swelling of the tongue andsoft tissues can be severe enough to causetotal airway obstruction (34). Laryngealedema, facial edema, enlarged tongue,voice change, or stridor can rapidly de-velop in a preeclamptic patient withoutany warning signs; therefore, cautionshould be exercised even during extuba-tion (35). Dysphonia due to uvular edemahas also been reported (36).

Morbid Obesity and DifficultAirway

Morbid obesity in pregnancy is associ-ated with increased risk for diabetes, hy-pertension, preeclampsia, and primarycesarean section (37, 38). There is also ahigher incidence of difficult labor in mor-bidly obese parturients, with increasedlikelihood of instrumental delivery and

postpartum hemorrhage in these pa-tients, conditions all requiring an anes-thetic intervention (39, 40).

The incidence of partially obliteratedoropharyngeal anatomy among obeseparturients is double that among nonobese parturients (27, 41). There is notonly an increased risk of difficult intuba-tion but also increased difficulty in main-taining adequate mask ventilation. Maskventilation tends to be difficult because oflow chest wall compliance and increasedintra-abdominal pressure (30). Hood etal. (37) showed that in morbidly obeseparturients (�130 kg), difficult intuba-tion was encountered more frequently.

Morbidly obese parturients are at in-creased risk for anesthesia-related mor-bidity and mortality during cesarean sec-tion and, in particular, increased risk offailed intubation and gastric aspirationduring procedures under general anes-thesia (41, 42). A review by investigatorsin Michigan of anesthesia-related mater-nal mortality showed that obesity was amajor risk factor for maternal mortality(41). The obstetrical closed-claims filesindicate that damaging events related tothe respiratory system were significantlymore common in obese parturients(32%) than in nonobese parturients(7%). Death was also more commonamong the obese parturients. The prob-lems highlight the increased need to haveairway algorithms and equipment readilyavailable when caring for these obese par-turients (43).

Obstetricians’ Role inManagement of Difficult Airway

A collegial and collaborative approachbetween obstetricians and anesthesiolo-gists when dealing with high-risk partu-rients facilitates optimum patient care.According to the American College of Ob-stetricians and Gynecologists (ACOG)Committee Opinion (1992), the obstetri-cal care team should be alert to the pres-ence of risk factors that place the partu-rient at increased risk for complicationsfrom general anesthesia (44). The anes-thesiologist should be alerted when suchrisk factors are identified. Considerationshould be given to early placement of afunctioning labor epidural in these pa-tients.

Training of obstetrical residents im-proves patient safety and educates themregarding risks of failed intubation. Asmore anesthesiologists become aware ofand receive training in advanced airway

Figure 4. Probability of experiencing difficult intubation with varying combinations of risk factors.Adapted from Anesthesiology 1992; 77:67.

Figure 3. Relative risk factors associated with difficult intubation (DI) in comparison with class Iairway. Adapted from Anesthesiology 1992; 77:67.

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management, it will in turn lead to thetraining of other physicians, thus result-ing in a decrease in airway disasters (45).Gaiser and colleagues conducted a studyof 160 parturients to evaluate obstetri-cians’ ability to assess the airway beforeand after instruction in airway examina-tion. The authors concluded that al-though instruction in airway examina-tion did not affect obstetricians’ ability topredict difficult airway, it changed theirapproach to labor analgesia. The attend-ing obstetricians requested prophylacticplacement of early epidural catheters inpatients who were thought to have diffi-cult airways (46).

If the anesthesia care team recognizesa difficult airway in a parturient, the ob-stetrician and anesthesiologist shoulddiscuss placement of a continuous epi-dural or spinal catheter as soon as it isdetermined to commit the patient to la-bor and delivery. Early intervention andplacement of a functioning regional an-esthetic will minimize emergency induc-tion of general anesthesia in parturientswith difficult airways. The obstetriciansshould also recognize that in the event ofan urgent/emergent cesarean section, es-tablishing a surgical block is quicker thanestablishing adequate anesthesia, as com-pared with an awake intubation or, evenworse, securing an airway after failed in-tubation under suboptimal conditions.

Management of Difficult Airwayin Obstetrics

Incidence of Failed Intubation. Failedintubation occurs in the general surgical

population at a rate of 1 in 2,330 (21).Theincidence of failed intubation is approxi-mately eight times higher in the obstet-rical population than among nonobstet-rical patients, where the estimatedincidence is found to be 1 in 280 (47).Furthermore, the incidence of fatal failedintubation is 13 times higher in the ob-stetrical population (48).

Labor. After a thorough preanestheticevaluation is done and difficult airway issuspected, communication with the ob-stetrical colleagues becomes essential.Early labor analgesia is initiated, and hav-ing a functional epidural catheter helpsestablish surgical anesthesia for a cesar-ean section if needed. It is essential for ananesthesiologist to get involved earlierrather than later, especially for high-riskparturients, such as obese or preeclamp-tic parturients with difficult airway. Afunctioning epidural block avoids theneed for general anesthesia and airwayinstrumentation, thus reducing the po-tential for airway disasters.

The ACOG bulletin (2002) recom-mends that “when feasible, obstetricalpractitioners should delay the adminis-tration of epidural anesthesia in nullipa-rous women until the cervical dilationreaches at least 4–5 cm and that otherforms of analgesia should be used untilthat time” (49). This recommendation isbased on studies that identified an asso-ciation between the epidural analgesiainitiated early in labor and an increasedrate of cesarean section (50, 51). How-ever, a recent landmark study publishedin the New England Journal of Medicine

(52), involving 750 nulliparous women,demonstrated that the incidence of cesar-ean section rate was not increased whenneuraxial analgesia was initiated early inlabor. In contrast, early neuraxial analge-sia provided better analgesia and resultedin a shorter duration of labor than didsystemic analgesia.

For patients in whom technical diffi-culties are encountered during epiduralplacement or in cases of accidental duralpuncture, the epidural catheter can bethreaded into the epidural space and con-tinuous spinal analgesia can be used as analternate technique during labor. Cau-tion should be used when dosing a con-tinuous spinal catheter for a cesareansection, particularly in a patient with adifficult airway, in order to avoid a highor total spinal anesthesia (53).

Cesarean Section: Anticipated Diffi-cult Airway. Under controlled circum-stances, anesthesiologists should haveadequate time to evaluate an airway andadminister aspiration prophylaxis. Whena difficult airway is suspected and surgeryis nonurgent, three options are available:awake intubation, regional anesthesia,and local anesthesia. Regional anesthesiaand local anesthesia may not always be asolution because of the chance of conver-sion to general anesthesia, especially dur-ing massive hemorrhage or failed local/regional anesthesia. Emergent inductionof general anesthesia under suboptimalconditions can result in significant mor-bidity and mortality.

Manipulation of the upper airway in aparturient requires special attention.Placement of oral/nasal airways, suction-ing, and careless laryngoscopy can resultin airway trauma and bleeding. Manipu-lation of the nasal airway can lead toepistaxis. Smaller endotracheal tubes arerecommended for parturients because ofthe mucosal swelling, which decreasesthe area of the glottic opening. Breastengorgement can hinder laryngoscopy;thus, proper positioning is necessaryalong with the availability of a short-handled blade.

The most important criterion for en-suring successful direct laryngoscopy andtracheal intubation, particularly in theobese parturient, is proper patient posi-tion. It is essential that the morbidlyobese parturient be placed with head, up-per body, and shoulders significantly ele-vated above the chest. In order to accom-plish the same, one must create a ramp,using folded towels or blankets under theshoulders and head. The Elevation Pillow

Figure 5. Mandibular protrusion test. Adapted from Anaesthesia 1995; 50:756.

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(Mercury Medical, Clearwater, FL) isshaped like a ramp and is designed foroptimizing the sniff position.

Awake Fiberoptic Intubation. Whenan anesthesiologist anticipates difficultairway and predicts difficult mask venti-lation and intubation, a very safe optionis to secure the airway with a trachealtube while the patient remains awake—although awake intubation can be time-consuming. There are several compellingreasons to perform an awake intubationat the very outset in a patient with arecognized difficult airway: the naturalairway will be better preserved in mostpatients when they are awake; adequatemuscle tone is maintained to keep therelevant upper airway structures (base oftongue, vallecula, epiglottis, larynx,esophagus, and posterior pharyngealwall) separated from one another andmuch easier to identify (54).

Full aspiration prophylaxis should beinstituted before intubation. An anticho-linergic drying agent such as glycopyrro-late allows better application and absorp-tion of local anesthetics to the airwaymucosa and thus improves visualizationof the oropharyngeal structures.

The route of fiberscopic intubation isimportant in pregnant patients. The nasalmucosa is engorged in pregnancy, anddespite vasoconstriction this can precipi-tate epistaxis, leading to a compromisedairway. The oral route is commonly usedand preferred. Topical anesthesia is theprimary anesthetic for an awake intuba-tion. It can be achieved with a spray oflidocaine at the base of the tongue andlateral pharyngeal walls, along with ap-plication of lidocaine jelly to the base ofthe tongue via a tongue blade. Sufficienttime must be allowed to anesthetize allportions of the airway. This helps to min-imize the swallowing and gag reflexes.The larynx and trachea can be topicallyanesthetized by injection of lidocainethrough the cricothyroid membrane orvia the suction port of the fiberscope (55).The patient is at risk for aspiration ifregurgitation or vomiting takes place af-ter topical anesthesia and before the air-way is secured. A shorter interval be-tween application of topical anesthesiaand tracheal intubation lessens the po-tential of aspiration (56).

Once the upper airway is properlyanesthetized, there are other, differenttechniques for intubating the trachea. Ei-ther direct or fiberscope-guided laryngos-copy or a combined technique of directlaryngoscopy and fiberscopy can be used.

The choice of technique depends on theskill and experience of the anesthesiolo-gist. With adequate psychological andpharmacologic preparation, patients cantolerate either direct laryngoscopy or fi-berscopically guided intubation (57).

Regional Anesthesia. Regional anes-thesia is the best possible choice in mostcases of anticipated difficult airway (9).Either spinal or epidural anesthesia isacceptable, provided no contraindicationsexist in the absence of fetal compromise.Drugs for aspiration prophylaxis shouldbe given before either anesthetic, alongwith an intravenous fluid bolus. When acesarean section is nonemergent, epi-dural anesthesia can be used. The advan-tages of epidural anesthesia are slow ti-tration of the block and avoidance ofmajor hemodynamic and respiratorycompromise. When time is limited, spinalanesthesia is the choice. With adequatefluid bolus and appropriate dosing of lo-cal anesthetic, surgical anesthesia can beestablished very quickly. After regionalanesthesia is in place, supplemental oxy-gen should be provided to the motheralong with left uterine displacement toavoid aortocaval compression.

The advantages of regional anesthesiainclude the following: the mother isawake and can protect her airway; airwaymanipulation is not necessary; the inci-dence of acid aspiration is decreased.

If regional anesthesia is administeredto a patient with difficult airway, thenclose monitoring, an experienced anes-thesiologist, and equipment should beimmediately available to establish an air-way in case a need arises.

Local Anesthesia. In patients with adifficult airway undergoing urgent cesar-ean section, regional anesthesia is con-tradicted; one can choose local anesthesiaas the primary anesthetic technique. It isused frequently in developing countriesbut rarely developed ones today. In mostteaching institutions, an obstetrics resi-dent may complete training without everhaving seen or done a cesarean sectionunder local anesthesia. In our institution,the obstetricians are trying to propose aprotocol in which every senior residentshould perform at least one cesarean sec-tion under local anesthesia before com-pletion of the residency. There have beena few case reports with very good descrip-tion of the technique for cesarean section(58). The advantages of local anesthesiaare as follows: the obstetrician can per-form the technique without waiting foran anesthesiologist; airway manipulation

is not necessary; hemodynamic stabilityis maintained if a safe dose of local anes-thetic is used; the awake mother has pro-tective airway.

Cesarean Section: Unanticipated Dif-ficult Airway. In a patient requiring anemergency cesarean section for fetal dis-tress, the urgency may limit the anesthe-siologist’s opportunity to perform a com-plete assessment of the airway. The headposition should be optimized for antici-pated tracheal intubation by aligning theoral, pharyngeal, and laryngeal axes. Theideal position (sniffing position) isachieved by elevating the head, flexingthe neck, and extending the head at theatlanto-occipital joint. No matter howemergent the need for delivery, timeshould be taken before induction of gen-eral anesthesia to ensure proper position-ing (33). After initial attempts at intuba-tion fail, management goals includematernal oxygenation, airway protection,and prompt delivery of the baby. If possi-ble, consider returning to spontaneousventilation, awakening the mother, andcalling for help. In most of the situationsother than maternal hemorrhage and fe-tal distress, the mother can be awakenedand fetal status reassessed. If the fetalstatus is reassuring, either regional anes-thetic or an awake intubation is consid-ered.

When the first attempt at intubationfails, a different blade may be used, and amore experienced anesthesia practitionershould attempt intubation. More thanthree attempts at laryngoscopy can causeedema and trauma of the oropharyngealtissues, leading to an unmanageable air-way. If intubation fails after a maximumof three attempts, a failed-intubationplan, with the aim of maintaining oxy-genation and awakening the mother,should be initiated immediately (59).

Failed Initial Attempts at Intubation.The recommendation in the case of agrade III laryngoscopic view is that nomore than three attempts at laryngos-copy and intubation should be made. Re-peated intubation attempts increase thedamage and lead to edema of the larynxand other airway structures. Useful aidsin such a situation include an Eschmanngum elastic bougie, smaller endotrachealtube, or a hockey-stick bend on the distalend of a smaller (6.0-mm) endotrachealtube. In a grade IV laryngoscopic view,the Difficult Airway Algorithm should befollowed without delay (60).

Nonemergent Pathway: Can Venti-late, Cannot Intubate. If surgery needs to

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proceed after initial attempts at failed in-tubation, mask ventilation with cricoidpressure is attempted. Call for help im-mediately. If the patient cannot be intu-bated, gas exchange is totally dependenton mask ventilation. The optimal attemptat conventional mask ventilation shouldbe a two-person effort. Better mask sealand jaw thrust and greater tidal volumeare achieved with two people than oneperson (61). Appropriate-size oral airwayshould be used for successful mask ven-tilation. If mask ventilation is easy andsteps are taken to minimize aspiration,patient should be awakened in the ab-sence of fetal distress. Mask ventilation iscontinued with cricoid pressure until thepatient is fully able to protect her airway(62). Adequate oxygenation without aspi-ration is the goal at this juncture.

In 2003, practice guidelines for man-agement of the difficult airway were up-dated. Under these new guidelines, laryn-geal mask airway (LMA) is the tool ofchoice in a “cannot ventilate, cannot in-tubate” (CVCI) situation. If the LMAproves to be successful, a nonemergencysituation arises and a nonemergencypathway of the Difficult Airway Algorithmcan be followed. When placing the LMA,cricoid pressure needs to be releasedtransiently. Data from all studies assess-ing the efficacy of LMA insertion with orwithout cricoid pressure show that LMAinsertion is more successful without cri-coid pressure (94%) than with cricoidpressure (79%) (63–66). If the LMA fails,an emergency pathway with the Combi-tube, transtracheal jet ventilation (TTJV),and a surgical airway are the reasonableoptions.

Airway Devices. When recognized be-fore attempts at tracheal intubation, vir-tually all difficult airways can be securedby the selected use of specialized trachealintubation techniques. LMA, ProSealLMA, and Combitube are supraglottic air-way devices and can be successfully usedif there is no airway obstruction at orbelow the glottis. Recently the use of alaryngeal tube has also been found to beuseful in a difficult airway–failed intuba-tion situation.

Laryngeal Mask Airway. The inven-tion of LMA has revolutionized the man-agement of difficult airway. It has beenused extensively all over the world toprovide a safe airway in patients who arenot at risk for aspiration of gastric con-tents. LMA is not routinely used in preg-nant patients because they are at highrisk for aspiration. If intubation and mask

ventilation of the patient prove impossi-ble, the use of LMA may be life-saving,however. The unanticipated arm of theDifficult Airway Algorithm has changedso that the LMA is no longer in neitherthe emergency pathway nor the non-emergency pathway but in fact is amongthe routine airway techniques. Thischange is probably due to familiarity withthe LMA, its availability, and the highsuccess rate for both experienced andnew users. It was introduced into the ASADifficult Airway Algorithm in the mid1990s. It can be used as a ventilatorydevice or an intubating conduit and fitsinto the Difficult Airway Algorithm inseveral places as both recognized and un-recognized difficult airway. LMA shouldbe used earlier rather than later followingfailed endotracheal intubation. Han andcolleagues reported the successful use ofthe LMA as a ventilatory device in 1,060of 1,067 patients for elective cesarean de-livery (67).

The ASA Task Force on the manage-ment of a difficult airway states that avail-ability of equipment for the management ofa difficult airway is associated with reducedmaternal complications and also recom-mends that labor and delivery units shouldhave equipment readily available to manageairway emergencies (26, 56). In a Germansurvey, LMAs were available in 91% of theobstetrics departments, similar to figuresfrom the United Kingdom (91.4%). Accord-ing to the same survey, 72% of anesthesi-ologists favored LMA as the first treatmentoption for the CVCI situation (68). In asurvey in the United Kingdom, 71.8% ofobstetrical anesthesiologists advocated useof LMA in a CVCI situation. Eight anesthe-siologists stated that LMA proved to be a‘lifesaver’ (69). Recently, 18 obstetrics unitsin Ireland were surveyed for difficult airwayequipment. All of the units had LMA as analternative device for ventilation and intu-bation. Fifty percent of the units also hadan intubating laryngeal mask airway(ILMA) among their airway equipment(70). Ezri and colleagues conducted a sur-vey in Israel to evaluate the practices ofIsraeli anesthetists regarding familiaritywith airway devices. Ninety-six percent ofthe anesthetists were skilled with LMAs and73% with fiberoptics. Of the obstetricalrooms surveyed in this study, only 36%were equipped with laryngeal masks, 24%with fiberscopes, and 22% with equipmentfor tracheal puncture (71).

ProSeal-LMA (PLMA). PLMA was in-troduced into clinical practice in 2000.This device is a modification of the classic

LMA and provides a better seal and betterairway protection. It has a second lumen,arising from the tip of the laryngeal maskand terminating outside of the patientairway. This lumen, which is called thegastric drain, has been demonstrated toeffectively vent passively or actively re-gurgitated esophageal contents. An oro-gastric tube can be placed through thislumen to empty the stomach. The designof the PLMA reliably allows positive pres-sure ventilation up to 30–40 cm H2O.Thus, the seal is 10 cm H2O higher, giv-ing it greater ventilatory capability thanthe classic LMA.

The PLMA has been successfully usedin parturients after failed intubation dur-ing rapid-sequence induction (56, 72, 73)and in postoperative respiratory support(56, 72). It has also been used duringeight sessions of electroconvulsive ther-apy in a pregnant woman at 20–22 wks ofgestation with a known difficult airway(74). Recently, a study was approved for acohort-controlled study using PLMA in100 elective cesarean section patients(75).

Intubating Laryngeal Mask Airway.The major difference between the ILMAand the classic LMA lies in the design andthe function of the shaft. In the classicLMA, the primary function of the shaft isto serve as a gas conduit. In the ILMA, theshaft is rigid and serves two additionalpurposes: it acts as an insertion tool thatensures the alignment of the mask withthe glottic opening, and it provides a con-duit for a smooth and atraumatic intuba-tion when the mask aperture is in align-ment with the glottic opening. ILMA hasalso been used in parturients after failedintubation (76, 77).

Laryngeal Tube. Laryngeal tube is anew supraglottic airway device. It is amultiple-use silicon tube with an oropha-ryngeal and esophageal low-pressure cuffand a ventilation outlet between thesecuffs. While the head is kept in neutralposition, the tube is placed into the oro-pharynx until resistance is felt. Both thecuffs are then inflated and the ventilationoutlet is placed in front of the vocal cords(78). Laryngeal tube-S (LTS) is a newer-generation laryngeal tube that is fittedwith a second lumen for suctioning andgastric drainage. LTS has been recentlyused in a parturient having an urgentcesarean section in a CVCI situation (79).

The LTS may be a good choice foremergency airway management. It pro-vides a higher airway seal than the classicLMA and insertion time is comparable.

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An airway pressure of 40 cm H2O can beachieved without gastric inflation (79). Itmay have a role in obstetrical emergencyairway management.

Combitube. The Esophageal TrachealCombitube is another airway device thatcan be used to establish an airway whenmask ventilation and intubation havefailed. It is a disposable, double-lumentube with an esophageal and large pha-ryngeal cuff. It received approval in 1988from the U.S. Food and Drug Administra-tion. It can be placed blindly or with thehelp of a laryngoscope. The Combitubeprovides an option for blind intubation ofeither the esophagus or trachea. In eitherposition, the patient can be oxygenatedand ventilated, and the airway is pro-tected against aspiration of gastric con-tents. Combitube has been successfullyused for management of failed intubationin cesarean delivery (80). It has a goodsafety record, as inexperienced personnelwithout any formal training can place itpromptly and quickly.

If mask ventilation cannot be achievedand a CVCI situation exists, it is critical toimplement immediate life- saving ma-neuvers, such as TTJV, cricothyroid-otomy, or surgical tracheostomy.

Emergent Pathway: CVCI. When maskventilation is not possible and the patientcannot be intubated, a CVCI exists andgas exchange must be restored as quicklyas possible. If airway obstruction occurs,cricothyroidotomy or surgical airway isthe technique of choice in the event of alife-threatening situation. TTJV in a pa-tient with airway obstruction can be haz-ardous if there is no route for air escape.

Transtracheal Jet Ventilation. Percu-taneous insertion of a large-gauge intra-venous catheter through the cricothyroidmembrane is simple, quick, and relativelysafe in most patients. Cricothyroidotomyis faster than conventional tracheostomy.It is probably the fastest route to oxygen-ation in a desaturating patient. Whenperforming jet ventilation, it is essentialto allow for adequate exhalation to avoidbarotrauma. The recommendation is touse two nasal trumpets and allow enoughtime for exhalation. To achieve adequateoxygenation and ventilation, the TTJVsystem must have a sufficient high- pres-sure oxygen source (50 psi) that can driveoxygen through noncompliant tubingand the small TTJV catheter.

TTJV is not a very popular techniquebecause it is a surgical procedure and canproduce complications such as pneumo-

mediastinum, pneumothorax, and subcu-taneous emphysema. Oxygenation viaTTJV is only a temporary measure, andone person is dedicated solely to holdingthe catheter in place at the patient’s neck(61). All anesthesia care practitionersshould be familiar with the technical as-pects of TTJV, but experience with thistechnique in obstetrics is limited and notreported in the literature. Experiencegained with LMAs and Combitubes inelective surgeries makes the use of non-surgical devices preferable to TTJV.

Cricothyroidotomy and Surgical Tra-cheostomy. Performance of an emergent,hurried cricothyroidotomy or tracheos-tomy can be dangerous. Percutaneoussurgical cricothyrotomy or tracheostomyis probably a better option than opencricothyrotomy or tracheostomy. Percu-taneous cricothyrotomy is safe, quick,and as easy to perform as TTJV (9). Sur-gical assistance should be summonedearlier in the event of a difficult intuba-tion so that help will be available at theappropriate time.

Aspiration of Gastric Contents. Aspi-ration remains the number one cause ofdeath in obstetrical anesthesia, and it isfrequently associated with difficult/failedintubation or esophageal intubation (4).The patient at greatest risk for aspirationis the obese parturient who has eatenafter the onset of labor or within 6 to 8hrs of delivery. After 28 wks of gestation,all appropriate precautions should betaken to prevent aspiration. The tech-nique of rapid-sequence induction withcricoid pressure and endotracheal intuba-tion was introduced in obstetrical anes-thesia practice to protect the airway frompulmonary aspiration. Improper applica-tion of cricoid pressure can lead to prob-lems with difficulty during intubation.

The obstetrical patient is particularlyvulnerable to pulmonary aspiration dueto gastrointestinal changes, hormonalchanges, parenteral analgesics, and labor-induction agents. Pressure on the abdo-men during delivery and the loss of gagreflex during anesthesia may be contrib-uting factors to the aspiration of liquidgastric contents. Loss of consciousnessdue to local anesthetic toxicity, total spi-nal anesthesia, and eclampsia can alsopredispose a parturient to aspiration. As-piration can also occur during a highspinal or epidural block when the patientcannot cough or clear her airway effec-tively (4).

CONCLUSION

The inability to maintain a patent air-way after attempts at failed intubationremains a major concern with regard toanesthesia-related maternal morbidityand mortality and is also a significantsource of malpractice claims in obstetrics(6, 30). Teamwork between an anesthesi-ologist and an obstetrician is absolutelyessential for the safety of both the motherand baby. Most of us tend to agree thatairway emergencies have a way of occur-ring at the worst possible times. It isessential that all anesthesia care practi-tioners have a preconceived and wellthought-out algorithm and equipmentavailable to deal with airway emergenciesduring difficult or failed intubation in aparturient. Even if intubation is not pos-sible, every effort should be made tomaintain adequate ventilation and, moreimportant, oxygenation of mother and fe-tus.

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