Airway management for the pregnant patient

INTRODUCTION — Pregnant patients may require general anesthesia for non-obstetric or nondelivery obstetric procedures during pregnancy, or for delivery-related procedures. Airway management for pregnant patients may be complicated by the physiologic and anatomic changes of pregnancy, increased risk of gastroesophageal reflux and aspiration, and the need to consider both maternal and fetal consequences during airway management. Airway management for more broad patient populations, and other aspects of anesthetic management for obstetric patients are discussed separately.

●(See "Airway management for induction of general anesthesia".)

●(See "Management of the difficult airway for general anesthesia in adults".)

●(See "Anesthesia for cesarean delivery".)

●(See "Anesthesia for nonobstetric surgery during pregnancy".)

INCIDENCE AND CONSEQUENCES OF AIRWAY PROBLEMS

Incidence of difficult airway — Difficult intubation has been reported in 0.45 to 5.7 percent of intubations in pregnant women [1-6]. Although a similar proportion of the general surgical population (5.8 percent) has difficult intubations [7], the consequences of difficult intubation can be greater in the obstetric population.

While pregnancy is associated with established risk factors for difficult and failed intubation (eg, obesity, airway edema, emergency procedures), a systematic review of the literature suggested that difficult intubation rates are similar in obstetric and non-obstetric populations [8,9].

Failed intubation rates may be higher in obstetric patients. Several observational studies of obstetric patients have reported failed intubation rates of 0.18 to 0.56 percent [4-6,10-18]. In contrast, in a retrospective study of 13,380 surgical patients, only 0.045 percent had failed intubation [13].

A two year prospective survey of cases from 2008 to 2010 from the United Kingdom Obstetric Surveillance System (UKOSS) reported a failed obstetric intubation rate of 1 in 224 (0.45 percent; 95% CI 0.36-0.56 percent) in obstetric patients over 20 weeks gestation who required general anesthesia [4]. In a case control study of patients from this survey, index cases had a higher incidence of hypoxemia (SpO₂ <90 percent) compared with controls (71 versus 2 percent), and a lower nadir SpO₂ (40 versus 84 percent). The absolute rate of aspiration was higher in patients with failed intubation, but the difference was not statistically significant and numbers were small. A second UKOSS survey of cases from 2016 to 2019 reported a very low rate of gastric aspiration in patients who received general anesthesia (1.9 per 10,000 cases [95% CI 0.9-3.6]) [19].

A more contemporary multicenter analysis of more than 14,000 general anesthetics for cesarean delivery at 45 centers from 2004 to 2019 yielded difficult and failed intubation rates of 2.0 (1 in 49) and 0.12 (1 in 808) percent, respectively [20]. Risk factors for difficult intubation included increased body mass index, Mallampati score III or IV, short thyromental distance, limited mouth opening or jaw protrusion, and limited cervical spine mobility. A diminishing rate of difficult intubation and relatively low failure rate over the study period may reflect increased use of video laryngoscopy and prioritization of neuraxial techniques.

Risk factors for difficult airway — Pregnancy-specific risk factors for difficulty with airway management are unclear. Whereas Mallampati scores have been shown to increase over the course of pregnancy and during labor, it is not clear that the incidence of difficult intubation increases as well.

At the very least, predictors of difficulty with airway management in general patient populations likely apply to pregnant patients as well. Importantly, obesity and emergency surgery are risk factors for difficulty with all aspects of airway management. Compared with normal-weight women, the parturient with severe obesity is at increased risk of cesarean delivery, emergency cesarean delivery, failed epidural, and difficult intubation (see "Obesity in pregnancy: Complications and maternal management"). In a prospective study of parturients over 300 pounds (136.4 kg), 6 of 17 women who required general anesthesia had difficult intubations, four of which were unanticipated [21].

Maternal mortality — Anesthesia-related mortality in obstetric patients is most often due to respiratory events. Respiratory problems occur not just during induction of general anesthesia, but also at emergence and recovery, or in relation to regional anesthetic complications (eg, high spinal anesthesia) [22-24].

●In an analysis comparing anesthesia-related maternal deaths related to delivery in the United States from 1991 to 1996 with those from 1997 to 2002, while cesarean fatality rates under general anesthesia fell (from 16.8 to 6.5 per million) and those under regional anesthesia rose (from 2.5 to 3.8 per million), respiratory issues remained prominent [22]. Overall, the leading causes of anesthesia-related pregnancy deaths for 1991 to 2002 were induction problems or intubation failure (23 percent), respiratory failure (20 percent), and high spinal or epidural block (16 percent).

●In the state of Michigan from 1985 to 2003, 8 of 855 pregnancy-associated deaths were anesthesia-related, and seven were anesthesia-contributing; none of these occurred at induction of general anesthesia, but five resulted from hypoventilation or airway obstruction during emergence, extubation, or recovery [23].

●The Confidential Enquiries into Maternal Deaths and Morbidity in the United Kingdom publishes reports on a triennial basis. The report for 2006 to 2008 attributed seven deaths directly to anesthesia; of these, two deaths were from failure to ventilate the lungs upon induction of anesthesia, and two resulted from postoperative airway complications: opioid-induced respiratory arrest during patient-controlled analgesia and aspiration following extubation [24]. In the Confidential Enquiries review for 2009 to 2012, one of the four anesthesia-related deaths was from intraoperative bronchospasm and another was from post-extubation hypoventilation [25]. In the Confidential Enquiries review for 2013 to 2015, one of the two anesthesia-related deaths was due to aspiration during induction of anesthesia in a patient with a small bowel obstruction who was to undergo a combined cesarean delivery and general surgical procedure [26].

●A review of the literature on obstetric-failed intubations from 1970 to 2015 found that the incidence of failed intubation at cesarean delivery remained the same over the time period studied, at 0.23 percent, with one death per 90 failed intubations [14]. Maternal deaths were the result of aspiration, hypoxemia due to airway obstruction, or esophageal intubation.

Malpractice claims — Difficult or failed airway management is a source of liability for anesthesia clinicians. The incidence of malpractice claims related to airway difficulty is unknown. The Anesthesia Closed Claims Project provides information about maternal injury claims, but the data are limited by lack of a uniform definition of standard of care among experts who participate in the claim settlement and by the absence of a denominator population for evaluating the incidence of complications.

A 2005 Closed Claims Analysis identified 179 claims for difficult airway management between 1985 and 1999, 9 of which occurred during cesarean delivery [27]. No specific information about those 9 patients was provided.

A subsequent study of closed claims related to difficult airway management from 2000 to 2012 reported 97 claims, including 4 from obstetric patients who were difficult to intubate at induction of anesthesia [28]. All four patients were obese and two had preeclampsia; the study did not report whether difficulty with airway management was anticipated.

ANATOMIC AND PHYSIOLOGIC CHANGES OF PREGNANCY — Ante- and intrapartum anatomic and physiologic changes of the airway, gastrointestinal system, and respiratory function can increase the risk for a difficult intubation, as well as the risk of complications when airway difficulty occurs.

●Airway changes – Pregnancy weight gain and increased breast size can make optimal head and neck positioning difficult and can decrease the space available to open the mandible and place the laryngoscope blade. The use of a short laryngoscope handle can be helpful. The need to maintain a tilted body position for left uterine displacement may also impede optimal positioning for airway management.

As gestation advances, the oropharyngeal diameter appears to narrow, possibly due to oropharyngeal edema from fluid retention [29]. In a study that used the modified Mallampati classification (figure 1) to evaluate maternal airways, the number of patients with Mallampati class 4 airways increased by 34 percent between 12 and 38 weeks of gestation, and the increase correlated significantly with weight gain [30]. However, it is unclear whether the increase in Mallampati scores with advancing gestation also increases the risk of difficult intubation. In a single center review of over 100,000 deliveries of ≥20 weeks gestation over approximately 20 years, advancing gestational age was not a predictor of airway difficulty, though the number of reported events was small [1].

Hyperemia and growth of nasal polyps increase the risk of bleeding with placement of nasal airways or nasal fiberoptic intubation. (See "Airway management for induction of general anesthesia", section on 'Airway examination' and "Maternal adaptations to pregnancy: Dyspnea and other physiologic respiratory changes", section on 'Physiologic pulmonary changes in pregnancy'.)

Labor and delivery itself can also have adverse effects on the airway (picture 1). In studies evaluating airway changes between the onset and the end of labor, significant decreases in oral volume and pharyngeal area and volume were observed, and the modified Mallampati classification increased by one grade in 33 percent of parturients and by two grades in 5 percent of parturients [31]. The airway changes that occur during labor persist into the postpartum period, and should be considered when general anesthesia is used for surgery after delivery. In one study, worsening Mallampati class occurred during labor, was not predicted by longer duration of labor or greater volume of fluids administered, and had not fully returned to baseline at 48 hours postpartum [32]. In a single center review of difficult and failed intubation during anesthesia for over 100,000 deliveries, the two failed intubations occurred in patients who underwent postpartum tubal ligation [1].

Airway changes during labor may be more severe in patients with preeclampsia. In one single center prospective cohort study, sonographic airway measurements and Mallampati scoring were used to evaluate airway changes in preeclamptic and non-preeclamptic parturients during and after labor [33]. The Mallampati score increased from prelabor to post-labor in women with and without preeclampsia, and those with preeclampsia had more prominent tissue thickness at the hyoid level throughout labor. Even when not in labor, patients with preeclampsia may have greater upper airway narrowing and heightened airway reactivity compared with non-preeclamptic parturients [34,35]. In a registry study of more than 400 cases of general anesthesia for cesarean delivery, induction hypoxemia (SpO2 <90%) occurred twice as often (19 versus 9%) in women with hypertension, likely reflecting increased airway and pulmonary edema [36].

●Gastrointestinal changes – The obstetric patient is at increased risk of aspiration of gastric contents due to hormonal and anatomic changes in pregnancy, including lower esophageal sphincter incompetence with associated gastroesophageal reflux, low gastric pH, and distortion of the gastric anatomy due to the enlarging uterus [37] (see "Maternal adaptations to pregnancy: Gastrointestinal tract"). Gastric emptying is normal during pregnancy [38], but is delayed by labor and by administration of parenteral or neuraxial opioids for labor analgesia [39-41]. In a patient with a full stomach without protective airway reflexes (ie, after induction of anesthesia), difficulties in airway management prolong the period of risk for aspiration.

●Respiratory changes – Increased metabolic oxygen consumption combined with a progressive decrease in functional residual capacity (FRC) during gestation render pregnant patients less tolerant of apnea; there is a shorter time between onset of apnea and development of hypoxemia when general anesthesia is induced. This shortens the available time to respond to airway difficulty. (See "Maternal adaptations to pregnancy: Dyspnea and other physiologic respiratory changes", section on 'Physiologic pulmonary changes in pregnancy' and 'Preoxygenation and apneic oxygenation' below.)

PLANNING THE APPROACH TO AIRWAY MANAGEMENT — For elective surgery, similar to nonpregnant patients, airway management in pregnant patients is part of the overall plan for anesthesia. However, general anesthesia in the peripartum period is often performed for emergency surgery. Whenever possible, pregnant patients with risk factors for difficulty with airway management should have antenatal anesthesia consultation, to allow advance planning for labor analgesia and airway management for possible cesarean delivery, even if vaginal delivery is expected. (See "Anesthesia for cesarean delivery", section on 'Preoperative assessment'.)

Ideally, the airway of every patient on the labor floor should be evaluated soon after admission. If a patient has a potentially difficult airway, specific plans should be formulated for airway management, should it become necessary, and the entire care team (anesthesiologist, obstetrician, nursing staff) made aware. For most patients with predicted difficulty with airway management, neuraxial analgesia should be established early to avoid the need for general anesthesia and airway management for possible cesarean delivery. (See 'Use regional anesthesia' below.)

The widespread use of neuraxial techniques during labor and cesarean deliveries has significantly reduced the use of general anesthesia for delivery [42]. Due to the infrequent occurrence of difficult and failed airway, all personnel working on obstetric units should regularly review the difficult airway algorithms (see 'Management of the difficult airway' below); simulator training and drills can serve to improve and maintain skills [43].

Recognition of the difficult airway — Bedside tests to predict difficulty with airway management in the general population are shown in tables, and are discussed separately (table 1 and table 2 and table 3 and table 4). (See "Airway management for induction of general anesthesia", section on 'Prediction of the difficult airway' and "Management of the difficult airway for general anesthesia in adults", section on 'Recognition of the difficult airway'.)

Similar to non-pregnant patients, the ability to predict airway difficulty is limited in pregnant patients. As an example, in a prospective study of airway evaluation using five predictors of difficult intubation prior to emergency cesarean delivery, the majority (79 percent) of difficult intubations were missed [44]. Similarly, in a review of failed obstetric intubations over 45 years, two-thirds were not predicted to be difficult [14]. Despite the lack of sensitivity, at the very least, preoperative airway assessment forces the clinician to think about potential difficulty with airway management.

The airway can worsen during the course of labor, so patients should be re-examined prior to airway management if significant time has elapsed since the initial airway evaluation. In particular, the size of the tongue and uvula should be noted for women in prolonged labor or who are pre-eclamptic (picture 1).

Use regional anesthesia — For both elective and emergency cesarean delivery, one reason that neuraxial anesthesia may be preferred is to avoid the need to manage the airway. (See "Anesthesia for cesarean delivery", section on 'General versus neuraxial anesthesia'.)

Patients at high risk of a cesarean delivery may benefit from having a functional epidural in place in the event an anesthetic is required urgently. Particularly for patients with possible difficult airways, or those in whom rapid neuraxial placement may be difficult (eg, obesity), it is prudent to place an epidural, and verify that it is functional, before there is urgent need for it. (See "Neuraxial analgesia for labor and delivery (including instrumental delivery)", section on 'Preparation for surgical anesthesia'.)

Most urgent cesarean deliveries may be performed under neuraxial anesthesia; when a labor epidural is in place, it can be quickly dosed for surgical delivery. For patients without an epidural in place, spinal anesthesia can usually be initiated quickly, even when urgent cesarean delivery is indicated. In patients with an anticipated difficult airway, this is often quicker than performing an awake intubation. Factors to consider when choosing an anesthetic technique for urgent cesarean delivery are discussed separately. (See "Anesthesia for cesarean delivery", section on 'Failed or inadequate neuraxial block'.)

For nondelivery surgery in pregnant patients, the choice of anesthetic technique (ie, general, regional, or local anesthesia) should be based on the planned procedure and patient factors, including the airway assessment.

PREPARATION FOR AIRWAY MANAGEMENT

Equipment preparation — For all patients, immediately prior to anesthesia, both routine and emergency airway equipment should be checked for availability and functionality. Suggested routine and emergency airway supplies and equipment are discussed separately (see "Management of the difficult airway for general anesthesia in adults", section on 'Equipment preparation'). For obstetric patients, a short laryngoscope handle should be available. A short handle may facilitate insertion of the laryngoscope in patients with large breasts or patients with obesity, whose chest wall tissue may prevent insertion of a conventional handle.

On the labor and delivery unit, where general anesthesia is rarely used, it is prudent to have a system in place to regularly check availability and function of airway equipment. There is not time to assemble resources when an emergency intubation is needed. A formal system for summoning assistance can be useful.

Patient preparation

Fasting and aspiration prophylaxis — The obstetric patient is at increased risk of aspiration of gastric contents, especially in cases of difficult or failed intubation, when mask ventilation may be required (see 'Anatomic and physiologic changes of pregnancy' above). The risk may be reduced by fasting and use of pharmacologic prophylaxis.

●Preanesthesia fasting – Preoperative fasting for elective surgery is the same in pregnant patients not in labor as it is for nonpregnant patients (table 5). (See "Preoperative fasting in adults", section on 'Pregnant patients'.)

●Fasting guidelines for laboring patients

•Solid food – Gastric emptying of solid foods during labor is delayed, and intake should be avoided, especially when parenteral or neuraxial opioids are given.

Whether epidural analgesia changes gastric emptying during labor is unclear. A theoretical but unproven mechanism for enhanced gastric emptying in parturients with epidurals is reversal of the pain-related decrease in gastric motility.

In an observational study including 40 patients, 10 each of nonpregnant controls, third trimester nonlaboring patients, laboring term parturients without analgesia, and term parturients with labor epidural analgesia (ropivacaine with sufentanil), gastric emptying of a light meal (125 g of yogurt) was assessed by gastric ultrasound [45]. Gastric emptying was delayed in pregnant patients compared with nonpregnant controls and was further delayed in parturients in labor. However, gastric emptying was faster in patients with epidural analgesia than in laboring patients without analgesia (median gastric emptying fraction at 90 minutes 31 versus 7 percent). Of note, rates of emptying varied significantly among patients; at 120 minutes, there was food in the stomach in one nonpregnant patient, two pregnant nonlaboring patients, four patients with epidural analgesia, and nine laboring parturients without analgesia. Conclusions from this study are limited by the small study size, and may not be generalizable due to the low body mass index (BMI) of the studied patients (21 to 23 kg/m²), and exclusion of patients who did not have an empty stomach at the time of recruitment. In addition, the effects of epidural opioids may not have been apparent with the limited study duration.

The utility of gastric ultrasound for assessing stomach emptying in pregnant patients has not been established and may be limited by lack of expertise and difficulty obtaining adequate visualization in pregnant patients with higher BMIs.

•Clear liquids – Oral intake of clear liquids in labor has been liberalized and the 2016 American Society of Anesthesiology (ASA) practice guidelines for obstetric anesthesia and the American College of Obstetricians and Gynecologists (ACOG) committee opinion endorse a moderate amount of clear liquid intake for uncomplicated laboring patients [46,47]. In the authors' practice, we limit parturients to eight ounces of clear liquids per hour after the placement of an epidural; further restrictions, based on an individual patient's aspiration risk, are left to the discretion of the managing clinician. Patients with increased risk factors for aspiration (eg, severe obesity, diabetes, difficult airway) or patients at increased risk for operative delivery (eg, pre-eclampsia, multiple gestations) may require further restrictions of oral intake, which is determined on an individual basis.

In one study, 125 parturients who had epidural labor analgesia were randomly assigned to either fasting, or to drink up to 400 mL of apple juice over 90 minutes, after which stomach emptying was assessed with gastric antral cross section using ultrasound. Gastric cross sectional area was similar in the two groups [48]. However, caution must be exercised in applying the study findings to the general patient population, as it excluded women with diabetes mellitus, hypertension, prior gastric surgery, or active labor, and the average body mass index was 27 kg/m².

●Pharmacologic aspiration prophylaxis – Practice varies with respect to administration of pharmacologic aspiration prophylaxis prior to elective or emergency surgery in pregnant patients; ASA practice guidelines recommend considering administration of nonparticulate antacids, H2 receptor antagonists, and/or metoclopramide. Pharmacologic aspiration prophylaxis is discussed separately. (See "Anesthesia for cesarean delivery", section on 'Preparation for anesthesia' and "Anesthesia for nondelivery obstetric procedures" and "Anesthesia for nonobstetric surgery during pregnancy", section on 'Preoperative aspiration mitigation'.)

Patient positioning — Optimal patient positioning for airway management maximizes the chance of successful intubation and may be the most important determinant of successful direct laryngoscopy (DL) in pregnant patients, especially for patients with severe obesity. The starting position for airway management should be the sniffing position (to align laryngeal and pharyngeal axes), and for patients with obesity, a ramped position (to open the space between the chin and chest) (figure 2). (See "Airway management for induction of general anesthesia", section on 'Patient positioning' and "Anesthesia for the patient with obesity", section on 'Preoxygenation and apneic oxygenation'.)

Left uterine displacement should be maintained during airway management with at least 15 degrees of tilt to minimize aortocaval compression [49]; this can be achieved by either tilting the operating table or placing a wedge beneath the patient's right hip. (See "Anesthesia for cesarean delivery", section on 'Intraoperative positioning'.)

Preoxygenation and apneic oxygenation — Preoxygenation is used prior to induction of anesthesia for all patients, to prolong the time to oxygen desaturation during apnea associated with attempts at airway management. Preoxygenation is particularly important for pregnant patients, in whom the progressive decrease in functional residual capacity (FRC) and increase in oxygen consumption through pregnancy shorten the time to desaturation during apnea. (See "Maternal adaptations to pregnancy: Dyspnea and other physiologic respiratory changes", section on 'Physiologic pulmonary changes in pregnancy' and 'Anatomic and physiologic changes of pregnancy' above.).

We routinely preoxygenate parturients in a 30 degree head-up position, to increase FRC and therefore the efficacy of preoxygenation. In a randomized crossover trial study of 22 healthy term parturients, mean FRC increased by a mean difference of 188 mL compared with the supine position, though the degree of increase varied widely among patients (95% CI 18-358 mL) [50].

In acute emergencies, when there is limited time for preoxygenation, having the patient take eight deep breaths over 60 seconds provides optimal, time-effective protection against O₂ desaturation, in both pregnant and nonpregnant patients (see "Preoxygenation and apneic oxygenation for airway management for anesthesia", section on 'Breathing technique for routine preoxygenation'). A study comparing preoxygenation techniques in third trimester pregnant patients found that taking eight deep breaths of 100 percent O₂ over one minute was as effective in reaching 90 percent end-tidal O₂ (ETO₂) as three minutes of tidal-volume breathing in pregnant women at term; taking four deep breaths over 30 seconds was less effective [51].

Apneic oxygenation using standard nasal cannulae at 10 to 15 L/minute during laryngoscopy, or if available, transnasal humidified high flow nasal oxygen (HFNO), may also delay desaturation. For pregnant patients with risk factors for difficulty with airway management, we suggest administration of oxygen at 10 L per minute via nasal cannulae during preoxygenation and until the airway is secured. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia", section on 'Apneic oxygenation'.)

The use of high flow nasal oxygen (HFNO) for preoxygenation and apneic oxygenation during intubation for anesthesia has been shown to prolong safe apnea time, compared with facemask preoxygenation in both nonpregnant and pregnant patients [52]. High flow nasal oxygen is discussed in detail separately. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia", section on 'HFNO for preoxygenation and apneic oxygenation'.)

In a randomized trial including 34 healthy normal weight parturients who had general anesthesia for cesarean delivery (CD), the use of HFNO (50 L/minute) for preoxygenation and apneic oxygenation resulted in higher PaO₂ and end tidal O₂ immediately after intubation, compared with face mask preoxygenation at 10 L/minute (441.4±46.7 versus 328.7 ± 72.8 mmHg, and 86.7±4.1 versus 76.9±7.7 percent, respectively) [52]. PaCO₂ after intubation, lowest oxygen saturation, duration of apnea, and fetal outcomes were similar between groups.

The efficacy of HFNO in parturients with higher BMI, who may have associated ventilation/perfusion differences, is less clear, as patients with high BMI were excluded from the previously cited study and others. Two computer modelling studies suggest that HFNO is of less benefit compared to face mask preoxygenation for patients with obesity [53], and low-flow nasal oxygen (LFNO) may prolong safe apnea time more than HFNO in patients with obesity (BMI ≥40 kg m^-2) at term gestation [54]. Furthermore, for emergency CD, utility of HFNO compared to LFNO may be limited by the time it takes to set up and initiate the device (picture 2). (See "Preoxygenation and apneic oxygenation for airway management for anesthesia", section on 'Heated humidified high flow nasal oxygen'.)

CHOICE OF AIRWAY DEVICES

●Endotracheal tube versus supraglottic airway – We typically avoid the use of supraglottic airways (SGAs) after the second trimester even in fasted parturients, because pregnant patients may be at increased risk of aspiration from the second trimester onward. (See 'Anatomic and physiologic changes of pregnancy' above.)

SGA devices can be used in first and second trimester for non-obstetric, non-abdominal surgeries in carefully selected parturients. There are no data demonstrating increased aspiration risk in this patient population. However, for abdominal and laparoscopic surgeries in the pregnant patient, our preference is to use endotracheal intubation.

Endotracheal intubation during general anesthesia for cesarean delivery remains the primary and preferred mode of securing the airway in our practice. Smaller endotracheal tubes (ETTs) may be required for pregnant patients [55]. Use of an ETT smaller than 7 mm may be warranted for those with increased airway edema, history of difficult airway, or difficult view upon first laryngoscopy attempt.

For cesarean delivery, SGAs are primarily intended as rescue devices if there is unexpected difficult intubation with inadequate ventilation. There are numerous case reports documenting effective SGA rescue after failed intubation for cesarean deliveries, with rapid improvement of hypoxia and no evidence of pulmonary aspiration [56-58]. Elective use of two types of SGA (classic laryngeal mask airway [LMA], ProSeal LMA) has been reported in three prospective studies including nearly 5000 patients in undergoing elective cesarean delivery [59-61]. There was one case of regurgitation, but no aspiration or other serious adverse events. These studies should be interpreted cautiously, as they were conducted under controlled circumstances in nonobese patients without symptomatic gastroesophageal reflux. Thus SGAs should not be used indiscriminately for a broader group of parturients, nor should use of SGAs replace endotracheal intubation for cesarean delivery until further evidence of safety is established [62].

SGAs are a reasonable alternative to endotracheal intubation when intubation fails, and their use may avoid repeated intubation attempts that can result in airway trauma and ultimate inability to ventilate. For pregnant patients, we suggest the use of second-generation SGAs (eg, ProSeal, Supreme) rather than first-generation SGAs when used for rescue ventilation after difficult airway management. Second-generation SGAs are designed to facilitate controlled ventilation with a better seal and contain drain tubes allowing the passage of 14 French orogastric tubes for suction or passive drainage of gastric contents. (See "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults", section on 'Choice of supraglottic airway'.)

●Nasopharyngeal airways – Nasopharyngeal airways should generally be avoided or used cautiously in conjunction with a vasoconstricting agent during late gestation, when hyperemic nasal passages may increase the risk of epistaxis with instrumentation. Topical nasal vasoconstricting agents can reduce the risk of epistaxis if nasal mucosal manipulation is required for airway management [63]. The available topical vasoconstrictors have varying effects on uterine blood flow if absorbed systemically. Phenylephrine and epinephrine are effective vasoconstrictors but are also known to impair uteroplacental blood flow. Oxymetazoline, a non-selective alpha agonist, is the most effective vasoconstrictor for the prevention of epistaxis in non-pregnant patients [64], but its impact on uteroplacental perfusion is not known. Preclinical studies of the effects of the alpha-2 adrenergic agonist clonidine suggest that it may be ideal for both nasal mucosal vasoconstriction and uteroplacental arterial relaxation [65], but further study is required before suggesting its use.

Basic airway management techniques are discussed separately. (See "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults" and "Direct laryngoscopy and endotracheal intubation in adults" and "Video laryngoscopes and optical stylets for airway management for anesthesia in adults" and "Basic airway management in adults".)

CHOICE OF INTUBATION TECHNIQUE

Videolaryngoscopy versus direct laryngoscopy — The authors use videolaryngoscopy rather than direct laryngoscopy (DL) for the first attempt at intubation for all obstetric patients. Video laryngoscopes (VLs) improve visualization of the glottis, and may increase first pass success, particularly for patients with a difficult airway (see "Video laryngoscopes and optical stylets for airway management for anesthesia in adults", section on 'VL versus DL'). Repeat attempts at intubation can result in airway edema and trauma, oxygen desaturation, and aspiration.

The literature on the use of VLs in obstetric patients is limited. VLs are consistently shown to improve visualization of the glottis, but placement of the endotracheal tube may take longer with VL. Literature on the time to intubation, compared with DL, is conflicting, and has included patients with normal airways.

●In a single institution retrospective study of intubations in an obstetric unit over a 36 month period, all 18 patients who were intubated with a GlideScope VL were intubated on the first attempt, compared with 157 or 163 patient who were intubated with DL [66]. One case of failed intubation with DL was successfully rescued with VL.

●In a randomized trial including 100 patients who were intubated for general anesthesia for elective cesarean delivery, use of the McGrath VL improved glottic visualization, measured with Cormack Lehane and Percentage of Glottic Opening (POGO) scores [67]. Mean time to endotracheal tube placement was slightly shorter with the use of VL (29.8 versus 32.6 seconds), a difference that is likely clinically inconsequential. First pass success (a primary advantage of VL) was not reported.

●In another trial, 80 patients who underwent general anesthesia for elective CD were randomly assigned to intubation with a McGrath VL or DL with a Macintosh blade [68]. Intubation time was longer with the VL (mean 47.25 versus 32.2 seconds). POGO scores were higher in the VL group, whereas Cormack Lehane grades were similar. All patients were intubated successfully on the first attempt.

RSII versus routine intubation — For pregnant patients who undergo general anesthesia for surgery beyond 18 to 20 weeks of gestation, and for patients with symptoms of gastroesophageal reflux, the authors routinely perform rapid sequence induction and intubation (RSII). Although the Sellick Maneuver (application of cricoid pressure) was once considered a mandatory component of RSII, evidence of its efficacy in clinical practice is lacking, and cricoid pressure can make intubation and ventilation more difficult. Thus the use of cricoid pressure during RSII in obstetric patients should be individualized. (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Cricoid pressure controversies'.)

RSII is routinely performed without mask ventilation after induction to avoid inflating the stomach and thereby increasing the chance of regurgitation. However, we perform mask ventilation using low inspiratory pressures (<20 cm H₂O) with cricoid pressure during RSII if difficult intubation is expected, or if desaturation occurs prior to laryngoscopy [69]. (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Modified RSII'.)

MANAGEMENT OF THE DIFFICULT AIRWAY

Algorithmic approach — Management of the difficult airway for anesthesia for any patient requires an algorithmic approach, based on known or predicted difficulty with airway management and mitigating patient factors. (See "Management of the difficult airway for general anesthesia in adults".)

The algorithms we use for anticipated and unanticipated difficult intubation for cesarean delivery are provided (algorithm 1 and algorithm 2). Other algorithms have been created for difficult airway management, including the American Society of Anesthesiologists Difficult Airway Algorithm (which is meant for general patient populations) (algorithm 3) and the airway algorithms from the Obstetric Anaesthetists' Association and Difficult Airway Society (OAA/DAS; which were created for pregnant patients). The OAA/DAS algorithms focus on management of the unanticipated difficult airway, and include a table that may be particularly useful for deciding whether to continue with cesarean delivery after a failed intubation (figure 3) [70].

Differences between pregnant patients and other patient populations include pregnancy-related changes in maternal physiology (eg, rapid oxygen desaturation), increased risk of aspiration, and the need to consider both the maternal and fetal status.

Since neuraxial anesthesia is used most often for cesarean delivery, the need to manage the airway is rare, and encountering difficulty with airway management is even rarer. In addition, general anesthesia is often used in an emergency with associated time pressure. Thus, personnel working on obstetric units should regularly review the difficult airway algorithms and have cognitive aids available. Obstetric decision-making can be enhanced with simulation training, critical skills performance checklists [43] and use of validated algorithms that incorporate maternal and fetal status [71]. (See "Patient safety in the operating room", section on 'Institutional and systems approaches to safety improvement' and "Cognitive aids for perioperative emergencies", section on 'Potential benefits of cognitive aids'.)

Anticipated difficult intubation — In patients with anticipated difficulty with airway management, scheduled delivery should be considered based on immediate availability of necessary personnel and equipment for airway management. If these resources are not available 24 hours per day, elective CD may be warranted for airway management, separate from any obstetric indications [72].

When difficulty with the airway is anticipated in a parturient prior to cesarean delivery, we use the following algorithm (algorithm 1).

For patients with predicted difficult intubation, neuraxial anesthesia is preferred over general anesthesia for cesarean delivery; even when there is an urgent need for delivery, a spinal anesthetic may often be performed more quickly than an awake intubation. General anesthesia with endotracheal intubation may be required in situations such as massive hemorrhage, local anesthetic systemic toxicity (LAST), high spinal anesthetic, failed regional anesthesia, or maternal cardiac arrest. A study comparing risk/benefit ratio of various anesthetic options for emergency cesarean delivery reported time to induction of 100 seconds for rapid sequence induction and intubation with video laryngoscopy (VL), 9 minutes for awake flexible scope intubation, an 6.3 minutes for rapid spinal anesthesia [73]. The benefit of expedience with rapid sequence VL likely outweighs the calculated risk of failed airway of 21 (0 to 53) per 10,000 cases, to facilitate delivery and minimize potential fetal harm. (See "Anesthesia for cesarean delivery", section on 'Choice of anesthetic technique'.)

When general anesthesia is required in a patient with a difficult airway, we suggest securing the airway prior to the induction of general anesthesia. Although awake intubation may be time-consuming, it ensures continued oxygenation and ventilation during the intubation while maintaining normal protective airway reflexes to minimize chances of aspiration.

Awake intubation is discussed in detail separately (see "Management of the difficult airway for general anesthesia in adults", section on 'Awake intubation'). Importantly, pregnant patients may be at increased risk of LAST during airway topicalization for awake intubation, due to increased vascularity of the oropharyngeal mucosa and hormonal and physiologic changes. Local anesthetic doses and LAST are discussed separately. (See "Local anesthetic systemic toxicity", section on 'Local anesthetic dose' and "Local anesthetic systemic toxicity", section on 'Patient risk factors'.)

Unanticipated difficult or failed intubation — When difficulty with the airway occurs unexpectedly in a parturient, we use the following algorithm (algorithm 2). Management of the unanticipated difficult airway is discussed in detail separately (see "Management of the difficult airway for general anesthesia in adults", section on 'Mask or supraglottic airway ventilation'). Issues of particular importance for pregnant patients are discussed here.

●When intubation of an anesthetized patient is difficult, mask ventilation should be performed with cricoid pressure. Cricoid pressure should be released if ventilation is difficult.

●Nasopharyngeal airways should be avoided if possible, due to risk of epistaxis in an already difficult airway. An oral airway may be used as an alternative. If the nasopharynx is manipulated for oxygenation or intubation, application of vasoconstrictor such as phenylephrine or oxymetazoline can help to prevent epistaxis [63].

●Repeated attempts at intubation should be avoided, as repeated laryngoscopy can cause trauma, bleeding, or edema, and can result in the inability to ventilate. Data suggest that complications increase when more than two attempts at direct laryngoscopy (DL) are made. Intubating conditions should be optimized between attempts. (See "Management of the difficult airway for general anesthesia in adults", section on 'Unanticipated difficult intubation'.)

●Assistance should be requested immediately after a failed intubation, and maternal and fetal status should be immediately reevaluated in conjunction with the surgical and/or obstetric team.

●If ventilation is possible by facemask or supraglottic airway (SGA) after failed intubation in a parturient who requires immediate surgery (eg, for trauma or hemorrhage), proceeding with surgery is a reasonable option and may optimize the outcome for both the mother and for the fetus.

Unanticipated failed intubation for cesarean delivery — If intubation fails during anesthesia for cesarean delivery, mask ventilation should be attempted. Two-person mask ventilation may achieve better mask seal and tidal volume than one-person mask ventilation (see "Basic airway management in adults", section on 'Two-hand technique for bag-mask ventilation'). If ventilation remains inadequate, an SGA is the rescue tool of choice, preferably a second-generation or intubating SGA; there are several case reports of laryngeal mask airways (LMAs) relieving hypoxia after failed intubation in parturients [74-76].

Once ventilation is established by facemask or SGA, the decision to continue surgery or awaken the patient represents a balance between the clinician's confidence in the ability to ventilate and the maternal or fetal condition, as follows (figure 3 and algorithm 2):

●If the parturient is in immediate jeopardy (eg, from hemorrhage) proceeding with cesarean delivery is a reasonable option and may optimize the outcome for both the mother and for the fetus [77].

●If the maternal condition is stable in the setting of life-threatening fetal compromise, the maternal risk of pulmonary aspiration by proceeding with surgery with an unsecured airway (facemask or SGA) must be weighed against risk to the fetus of delaying delivery. In this setting, many anesthesiologists would proceed with cesarean delivery [78,79].

●If the mother and fetus are both stable, the decision to proceed with delivery or awaken the patient should be made by the anesthesiologist in consultation with the obstetric team. It is reasonable to place an SGA, maintain cricoid pressure (unless it prevents SGA insertion or prevents ventilation) and proceed with surgery.

If the patient is awakened, airway management should then proceed as it would be for anticipated difficulty with airway management. (See 'Anticipated difficult intubation' above.)

If surgery is continued without endotracheal intubation, it is reasonable to place an SGA, which provides a more secure airway. If available, a second generation SGA allows gastric drainage and may increase protection against aspiration. (See 'Choice of airway devices' above.)

A 2015 review of the literature on obstetric airway management found that in contemporary practice, facemask ventilation was used only after failed attempts at SGA placement, and that there were no reported cases of aspiration during facemask ventilation after failed intubation for cesarean delivery [14].

Cannot intubate, cannot ventilate — If ventilation is impossible, an emergency invasive airway technique should be used, such as cricothyrotomy, transtracheal jet ventilation, or tracheostomy. (See "Management of the failed airway during anesthesia".)

Cricothyroidotomy may be performed by anesthesiologists or surgeons using the percutaneous technique if the anatomy can be identified, or the open technique if it cannot. At the authors' institution, a "code airway" system is in place to urgently summon a general surgery team and emergency airway supplies to the bedside; anesthesia clinicians refresh skills for cricothyrotomy annually, but emergency invasive airway procedures are usually performed by surgeons.

Once attempts to ventilate are successful, the risks and benefits of proceeding with surgery should be discussed with the surgical and/or obstetric team. At any time during failed intubation and ventilation, maternal cardiac arrest may occur. For patients 20 weeks gestation, perimortem cesarean delivery may be required. Maternal cardiac arrest and perimortem cesarean delivery are discussed separately. (See "Sudden cardiac arrest and death in pregnancy", section on 'Delivery as part of the resuscitation process'.)

EXTUBATION — Pregnant patients should be extubated awake at the end of surgery to ensure that protective airway reflexes are intact. Importantly, for patients who have had massive hemorrhage, extubation should only occur after adequate resuscitation, without ongoing bleeding, and if the risk of further bleeding is felt to be low [26].

Airway complications are at least as likely to occur during emergence and extubation as during induction of anesthesia. In an analysis of pregnancy-associated deaths in Michigan over 18 years, four of the eight anesthesia-related deaths were the result of airway obstruction or hypoventilation during emergence, extubation, or shortly after arrival in the post-anesthesia care unit (PACU); there were no deaths during induction [23].

Risk assessment for extubation and extubation strategies are discussed in detail separately. (See "Extubation following anesthesia".)

POSTOPERATIVE MONITORING — Postoperative monitoring, availability of anesthesia clinicians, and post-anesthesia care unit (PACU) discharge criteria for pregnant or postpartum patients should be the same as they are for non-obstetric postoperative patients, whether they recover in the PACU or a labor room. (See "Overview of post-anesthetic care for adult patients", section on 'Assessment, monitoring, and care'.)

Importance of postoperative monitoring for obstetric patients is illustrated by a report of eight anesthesia-related maternal deaths in Michigan from 1985 to 2003, three of which were thought to have been preventable with standard postoperative monitoring, including pulse oximetry. [23].

Patients with risk factors for postoperative respiratory problems (eg, severe obesity, obstructive sleep apnea), and patients who are at increased risk for postpartum hemorrhage may require more intensive or prolonged postoperative monitoring.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Airway management in adults" and "Society guideline links: COVID-19 – Index of guideline topics" and "Society guideline links: Obstetric anesthesia".)

SUMMARY AND RECOMMENDATIONS

●Risk factors for airway difficulty

•Pregnancy is associated with a number of factors that increase the risk of difficulty with airway management and/or failed endotracheal intubation (eg, obesity, gastroesophageal reflux, upper airway edema, need for emergency surgery). (See 'Incidence and consequences of airway problems' above.)

•Respiratory problems are important causes of maternal mortality, and are at least as likely to occur on emergence or in the postoperative period as during induction. (See 'Incidence and consequences of airway problems' above.)

•Increased metabolic oxygen consumption combined with a progressive decrease in functional residual capacity (FRC) during gestation render pregnant patients less tolerant of apnea during attempts at airway management. (See 'Anatomic and physiologic changes of pregnancy' above.)

●Airway assessment

•Patients with risk factors for difficult intubation should have antenatal anesthesia consultation.

•The airway of every patient on the labor floor should ideally be evaluated soon after admission.

•For laboring patients, the airway should be reassessed before anesthesia, as the airway may worsen during labor. (See 'Recognition of the difficult airway' above.)

●Choice of anesthetic technique

•Using regional anesthesia rather than general anesthesia avoids the need to manage the airway. In laboring patients with increased likelihood of cesarean delivery or with anticipated difficult airway, we suggest early placement of an epidural catheter and dosing once labor is well established in order to minimize the need for general anesthesia, should urgent cesarean delivery be needed (Grade 2C).

•For nondelivery surgery during pregnancy, the choice of anesthetic technique should be based on the planned procedure and patient factors, including the airway assessment. (See 'Use regional anesthesia' above and "Anesthesia for nonobstetric surgery during pregnancy", section on 'Choice of anesthetic technique'.)

●Airway management

•Preparation for obstetric airway management includes preoxygenation, optimum patient positioning, and aspiration prophylaxis. For pregnant patients with risk factors for difficulty with airway management, we suggest administration of oxygen at 10 L per minute via nasal cannulae during preoxygenation and until the airway (Grade 2C). Alternatively, high flow nasal oxygen can be used for preoxygenation and apneic oxygenation if time permits. (See 'Preparation for airway management' above.)

•For pregnant patients beyond 18 to 20 weeks of gestation, and for patients with symptoms of gastroesophageal reflux, the authors avoid routine use of supraglottic airways (SGAs); we perform rapid sequence induction and intubation (RSII) in patients without risk factors for difficult intubation, and awake intubation in patients with predicted difficulty with intubation. (See 'Choice of airway devices' above and 'RSII versus routine intubation' above.)

•We suggest using second generation rather than first generation SGAs routinely early in pregnancy and for rescue ventilation after difficult airway management (Grade 2C). (See 'Choice of airway devices' above.)

•For cesarean delivery in a patient with an anticipated difficult airway who is not a candidate for regional anesthesia, we suggest awake intubation (Grade 2C). We use flexible scope intubation if the airway has not been traumatized; in a blood-obscured airway, other options include direct laryngoscopy, video laryngoscopy, intubating laryngeal mask airway, or retrograde intubation, depending on clinical experience and equipment availability (algorithm 1) . (See 'Anticipated difficult intubation' above.)

•In an obstetric patient with unanticipated difficult laryngoscopy, emergency airway equipment and skilled assistance should be immediately requested. Further management is shown in an algorithm (algorithm 2).

●Postoperative airway problems — Airway compromise during emergence and in the post-anesthesia period is an important cause of airway tragedies in the obstetric population. (See 'Postoperative monitoring' above and 'Extubation' above.)