Induction, maintenance, and recovery

Preoperative fasting

Appropriate preoperative fasting allows for adequate gastric emptying and reduction of aspiration risk when anesthetics abolish protective airway reflexes. Clinical observation, studies of residual gastric volumes and MRI studies of fasting gastric volumes have resulted in current American Society of Anesthesiologists recommendations for NPO times before anesthetic induction of 2 hours for clear liquids, 4 hours for breast milk, 6 hours for infant formula and nonhuman milk, 6 hours for light meals and 8 hours for heavy meals ( Table 21.1 ) ( ; ; ; ; ; ). have reported that even in overweight and obese children undergoing elective surgery, the 2-hour minimum preoperative clear-liquid fasting guideline is adequate.

Conversely, prolonged fasting can result in negative intravascular volume status, hypoglycemia, patient discomfort, and poor patient and parent satisfaction levels. The fluctuations that can occur around scheduled versus actual procedure times can result in unnecessarily long fasting times. Liberalization of pediatric fasting guidelines has occurred due to rapid gastric emptying in infants and children and the low incidence of pulmonary aspiration in the pediatric population ( ; ; ). European and UK pediatric anesthesia guidelines allow intake of clear liquids until 1 hour prior to anesthesia ( ). Parents should be encouraged to promote intake of clear liquids closer to the time of surgery. It is extremely important that those giving and receiving instructions on preoperative fasting clearly understand the terminology (i.e., what constitutes a clear liquid), timing, and importance of adhering to the guidelines. A clear liquid is a solution that contains no particulate matter. Examples of clear liquids include water, Pedialyte, carbonated beverages, clear tea, plain gelatin, and fruit juices without pulp ( ; ).

Children with gastrointestinal or systemic disorders that may interfere with gastric emptying should have individualized treatment decisions made regarding appropriate and safe fasting times. The use of point-of-care ultrasound (POCUS) to measure gastric antral cross-sectional area can be used to estimate residual gastric contents, thus providing additional risk assessment in patients where accurate NPO status is unclear or there is concern for delayed gastric emptying ( ; ).

Psychological considerations

During the preoperative period, it is extremely important to identify the children and families who are likely to develop pronounced fear and anxiety before and during the induction of anesthesia (see Chapter 15 : Psychological Aspects of Pediatric Anesthesia). Because the level of stress and underlying temperament that predispose individuals to extreme anxiety may not be overtly apparent, it is essential that the pediatric anesthesiologist carefully evaluate each patient. Indicative behaviors, beyond the obvious crying and uncooperative child, include the absence of social interaction or withdrawal, lack of age-appropriate independence from parents, and intensity of reactions ( ; ). It is also helpful to assess family members’ levels of anxiety and coping styles. The temperament of the parent also can play a significant role in the behavior of the child. The ability to identify these patients provides a valuable opportunity to improve the experience of both patient and family and to affect outcomes. In the immediate postoperative period, preoperative anxiety has been associated with emergence delirium, higher pain scores, and increased analgesic requirement ( ). Postoperative maladaptive behaviors including general anxiety, enuresis, nightmares, separation anxiety, and temper tantrums persisting beyond the day of surgery have been associated with preoperative anxiety ( ). Identification of patients at risk for preoperative anxiety allows for appropriate interventions to decrease the stress of induction, whether it be premedication, distraction techniques, or parental presence.

Medical considerations

Most children and infants scheduled for elective surgery procedures are in good health with an ASA physical status of I and II, but common disorders such as upper respiratory tract infection, reactive airway disease, gastroesophageal reflux (GERD), obesity, and hemodynamically stable congenital heart lesions can pose anesthetic management challenges for the pediatric anesthesiologist. All patients should undergo a thorough preoperative interview and examination. If general anesthesia is to be induced, appropriate precautions and interventions should be taken (see Chapter 16 : Preoperative Preparation).

Upper respiratory tract infection

Upper respiratory tract infection (URI) is one of the most common problems the pediatric anesthesiologist encounters, especially in the ambulatory surgery setting (see Chapter 47 : Respiratory Disorders). Young children on average may experience six to eight URIs a year, and it may be difficult to find a symptom-free period to undergo surgery. URI and the accompanying airway inflammation increase upper and lower airway reactivity and increase airway secretions. There is an increased incidence of severe coughing, breath holding, laryngospasm, bronchospasm, airway obstruction, and perioperative hypoxemia in patients with recent URI symptoms ( ; ; ; ; ). Airway reactivity, even in patients without a history of asthma, can develop with a URI and last for up to 6 to 8 weeks ( ; ). Risk factors for perioperative respiratory adverse events include nasal congestion, copious secretions, reactive airway disease, history of prematurity, secondhand smoke, airway surgery, endotracheal intubation, and laryngeal mask insertion ( ; ; ). The decision to postpone the procedure depends on the urgency and type of surgery, the patient’s age and presenting symptoms, the presence of comorbid conditions, and the need to instrument the airway ( ). Although the risk of perioperative respiratory adverse events is higher in the setting of a recent or resolving URI, these events are often self-limiting or easily treated. Therefore the decision to postpone or cancel a procedure relies on the anesthesiologist evaluating the patient and determining who is at highest risk for the more serious complications. The COLDS (Current signs; Onset; Lung disease; Device for airway; Surgery) score, developed by and validated by , provides a risk assessment tool for patients with an active or recent URI, based on information easily obtained on the day of surgery, to help guide the decision-making process ( Fig. 21.1 ). Patients with a score greater than 19 may benefit from having their procedure rescheduled due to the risk of perioperative adverse respiratory events.

In patients with recent URI symptoms, prophylactic bronchodilator treatment should be considered before induction and before emergence to reduce the risk of perioperative respiratory adverse events (PRAE) ( ). Intravenous induction with propofol is associated with a significantly lower risk of respiratory complications than inhalation induction with sevoflurane ( ), and preoperative intravenous (IV) cannulation should be considered. Pretreatment with glycopyrrolate has not been shown to reduce the risk of perioperative adverse respiratory events ( ).

Preanesthetic preparations

The preoperative interview is often the only opportunity for the anesthesiologist to assess the child and establish a relationship of trust and confidence with both the patient and family. Some surgical centers have presurgical tours and/or short movies to prepare children and families for the perioperative experience, although it is more common for families to have their orientation to the surgical center and anesthetic plan on the day of surgery ( ). Most pediatric waiting areas are designed as playrooms containing toys, busy boxes, video games, and movies/television programming ( Fig. 21.2 ). Children may be encouraged to bring a familiar object or favorite toy that they may keep with them throughout the preoperative and induction process.

During their initial interaction with a child, the anesthesiologist should utilize age-appropriate language and communication skills. They should make attempts to sit at the child’s eye level and initiate communication with the child as well as the parent. The anesthesiologist should express genuine interest or play with the child. This may help gain the child’s confidence and divert or reduce fear and anxiety. Good humor and empathy will go a long way to alleviate patient and family stress and anxiety.

Most children can be well managed in this friendly environment. An anesthesia mask may be given to the child to play with in the waiting area before induction. Allowing children to choose a flavor for their mask can provide them with a sense of control. The additional support of pacifiers, toys, and music boxes is often helpful. Children should keep the objects brought from home, particularly security blankets or other transitional objects, during the induction of anesthesia. Clowns have also been found to be helpful for the alleviation of preoperative anxiety in children, and some hospitals will have this available in their pediatric units ( ; ).

It can be beneficial to use child-life services to assist in orienting patients and families to the surgical environment and to prepare patients for what to expect during the perioperative experience. Whereas the anesthesiologist may have limited time to interact with the patient and family, a child-life specialist can devote more time to creating a bond with the patient and may even be able to stay with them through the induction process. They can help the patient and family with coping skills and discuss what to expect throughout the procedure (see Fig. 21.3 ) (see Chapter 15 : Psychological Aspects of Pediatric Anesthesia).

Portable audiovisual aids such as tablets and handheld devices have been shown to be effective at reducing perioperative anxiety of both patient and parent ( ; ). Video-based devices for distraction during induction are at least equivalent to oral premedication with midazolam and parental presence induction at reducing perioperative anxiety, postoperative pain, and emergence agitation ( ; ). The use of these devices, or any distraction device, beginning in the preoperative setting can help decrease anxiety, ease parental separation, and smooth the induction process. With even young patients being facile in the use of technological devices, distraction techniques with these devices may continue to be helpful to assist with the smooth induction of anesthesia (see Fig. 21.4 ).

It is important for the pediatric anesthesiologist to include patients and families in decisions regarding anesthetic induction and care. Together they should agree upon the needs for premedication, parental presence, and the type of induction technique (inhalation vs. intravenous) to ensure the smoothest and safest induction possible. Unfortunately, even the best of plans can fail, and backup measures such as additional premedicant, induction room, or another strategy for induction, must be readily at hand. For older, combative children scheduled for elective procedures, postponing the procedure until the child is properly prepared should be considered. Inhalation induction by force should be a measure of last resort.

Premedication

Premedication with anxiolytics has been shown to be a consistently reliable method for facilitating induction and reducing postoperative complications in anxious patients ( ; ; ). Contemporary administration of sedatives typically utilizes short, fast-acting agents that are typically administered by mouth or transmucosally. Adequate time for onset of sedation should be considered when determining appropriate time of administration. They are typically administered before induction to facilitate child-parent separation, anesthetic mask acceptance, and/or patient cooperation. Intramuscular (IM) administration is almost solely reserved for extremely agitated, uncooperative children.

Topical anesthesia

For children who require or prefer an IV induction, there are multiple approaches to achieve topical anesthesia. Local anesthetics can be delivered without needles through the skin’s protective stratum corneum into the innervated dermal layers. Commonly used creams that are absorbed through the skin include eutectic mixtures of lidocaine and prilocaine (EMLA) and liposomal lidocaine (LMX 4) ( ; ; ). Other mechanisms such as heat (Synera) and pressurized carbon dioxide (J-tip) or helium (Zingo) can be used to drive local anesthetic into the dermis ( ; ; ). Nonlocal anesthetic techniques such as vapocoolant spray (Pain Ease) and vibration therapy (Buzzy) can reduce the pain associated with venipuncture ( ). These techniques, each with limitations, can provide analgesia within 1 to 60 minutes (see Fig. 21.5 ). Mode of administration should be chosen based on time of administration in relation to time of venipuncture. Reported satisfactory anesthesia varies with technique and patient age. Children younger than 6 or 7 years of age tend to report pain, secondary to fear and anticipation of needle sticks, even with apparent anesthesia ( ; ).

Parental presence during induction

Parental presence during induction of anesthesia (PPIA), in the operating room or a separate area such as an induction room, has become a frequent part of the preoperative process at many hospitals in an effort to promote a family-centered approach to pediatric care ( Fig. 21.6 ) (see Chapter 15 : Psychological Aspects of Pediatric Anesthesia; Chapter 16 : Preoperative Preparation). Although the practice avoids separating children from their parents, it has not been shown to decrease patient anxiety or increase cooperation during induction ( ; ; ). One benefit, which is important in a family-centered environment, is an increase in parental satisfaction scores as parents perceive their presence as helpful to the child ( ; ). confirmed the previous findings of , that PPIA had a measurable benefit when a calm parent accompanied an anxious child and a worsening effect when an anxious parent accompanied a calm child. There was no measurable benefit when both child and parent were calm. Subsequently they have determined that parental preparation to reduce anxiety (e.g., learning distraction techniques, preoperative preparatory audiovisual aids) can significantly improve the outcome of PPIA ( ; ). Certain children with significant developmental delay, behavioral disorders, or combative behavior may benefit from parental presence as the parent may be very adept at managing and calming the child.

The logistical disadvantages of PPIA in the operating room include limited space, noise, unfamiliar equipment, and the need for parents to wear gowns and masks. Induction rooms can help anesthesiologists avoid some of these logistical problems, but there is no difference in behavioral compliance, parental satisfaction, or respiratory complications between the use of induction rooms and induction in the OR ( ). In both settings the parents must be prepared for the changes that can occur during induction, especially rapid loss of consciousness, uncoordinated movements, increased respiratory rate, and signs of upper airway obstruction. The anesthesiologist should be prepared to reassure the parents and respond quickly, especially if something goes wrong during induction. Additional OR personnel should be responsible for escorting parents to the waiting room as soon as their child loses consciousness.

Preparation for induction

Whether an operating room or a separate room is to be used for induction, anesthetic and monitoring equipment and supplies must be confirmed and readily available. The preinduction checklist for equipment should be completed, including a checked anesthesia machine, confirmation of gas pressures of accessory oxygen and nitrous oxide cylinders, an airtight breathing circuit, the availability of a self-inflating bag, working suction, size-appropriate airway supplies (predicted size and one size larger and smaller of face masks, oral and nasal airways, laryngoscope blades, and endotracheal tubes). Medications for induction and maintenance of anesthesia as well as emergency medications should be prepared and easily available. Except for patients with risk of malignant hyperthermia, emergency drugs for all pediatric inductions should include atropine and succinylcholine, which should be drawn into syringes of appropriate size for the patient’s age and weight and clearly labeled in case of severe laryngospasm. Supplies for starting and securing peripheral IV access should be prepared. Additional ancillary equipment such as tongue blades, adhesive tape, and soft suction catheters should also be at hand. If laryngeal mask airway (LMA) use is planned, appropriate size LMAs should also be included. Monitoring devices, such as an in-flow oxygen analyzer, pulse oximeter, capnograph, electrocardiograph (ECG), and automated blood pressure cuff should be available and ready to use. The temperature of the operating room should be properly adjusted and warming devices (e.g., forced air warming mattress or a radiant heat lamp) should be available for use.

Monitoring during induction

At a minimum, monitoring during induction should include pulse oximetry and capnography. If the child is anxious or combative, it is probably best to place additional monitors like ECG leads and a blood pressure cuff after induction instead of losing the opportunity for a calm induction. However, certain medical conditions such as congenital heart disease or extremes of age such as a premature neonate may necessitate full monitoring before and during induction. Baseline measurements should be obtained before the patient is exposed to any anesthetic agent. Reference values for noninvasive blood pressure in over 116,000 cases obtained 20 minutes after the start of anesthetic and before the start of the procedure well as values between 15 and 35 minutes after the start of the procedure were reported by ( Fig. 21.7 AB, Fig. 21.e1 and Fig. 21.e2 ).

Inhalation induction

Inhalation of sevoflurane with or without nitrous oxide through a mask is the most commonly used induction technique in pediatric anesthesia in the United States ( Fig. 21.8 ). It is a reliable method for induction that can be achieved with relative ease, speed, and safety, while avoiding the fear and pain of intravenous catheter insertion. The child can be awake or sedated, sitting up, lying down, or on the lap of a parent, and a mask can be easily applied. Sevoflurane can be administered incrementally and is easily reversed when discontinued. An inhalation induction allows general anesthesia to be obtained in patients with known difficult peripheral venous access without having to obtain an IV, and it is often the preferred induction method for potential difficult airways in order to maintain spontaneous ventilation. There are a few absolute contraindications to an inhalation induction with sevoflurane including malignant hyperthermia, certain muscular dystrophies, and central core disease.

When transitioning a child from the preoperative area to the site of induction, it is paramount that the well-sedated or asleep child is minimally stimulated and that the awake or lightly sedated child is kept occupied and distracted. One person, either the anesthesiologist or the accompanying family member, should do all of the talking, which should be reassuring and continuous. Giving patients and families the choice to have the child carried, walked, or wheeled to the induction location is another way to encourage participation and give them a sense of control. Perioperative staff in the room need to remain quiet immediately before and during the induction, or they should be asked to step away. Regardless of location, age of the patient, or intended procedure, induction of anesthesia should be completely focused on the child and uninterrupted by other activities or last-minute preparations.

Once in the operating room or induction room, the child may be given the choice to lie down or sit up. If sitting is elected and parents are present, the child can be offered the option to sit in a parent’s lap or next to them. The anesthetic mask should be shown to the child before proceeding. Putting artificial fruit or candy flavors in the mask may help disguise the odor of the anesthetic and increase acceptance of the mask. One should never place the mask on the child’s face without warning. Even with preparation, some children, especially those with previous experience with inhalation inductions, may strongly reject the anesthesia mask ( ). The mask may become more acceptable if a family or staff member initially tries it on, or if the anesthesiologist applies it to one of the child’s toys before placing it near their face. Other methods to promote acceptance of the mask include having the child watch the insufflation of the anesthetic bag, hold the mask themselves as they begin to breathe into the circuit or making a game out of watching the end-tidal CO ₂ tracing. Distraction techniques such as storytelling, singing, counting, or just talking nonsense are strongly encouraged. If the child objects to the smell of the inhaled anesthetic, breathing through the mouth to reduce the smell can be suggested. In cases of continued mask aversion, some have allowed the child to breath directly from the circuit, using it as a “snorkel” ( ). If the child still emphatically objects to the mask, other approaches such as supplemental sedation or an IV or IM induction should be considered. Inhalation induction by force should be avoided.

Sevoflurane is currently the only appropriate volatile anesthetic for inhalation induction; however the smell associated with it can often produce a negative reaction from the child. One way to avoid a negative reaction is to begin with a high flow of nitrous oxide and oxygen at a 7:3 ratio. During inhalation induction, use of nitrous oxide can increase mask acceptance as it is odorless and provides rapid onset of anxiolysis and sedation due to its low solubility. Nitrous oxide is commonly used in combination with sevoflurane to speed the rate of inhalation induction and decrease the incidence of excitement ( ). The mask should be loosely applied to the child’s face until sedation is evident. The full sedative effect of nitrous oxide will occur within 2 minutes and be observable as the respiratory rate slows. Sevoflurane can then be added and increased rapidly to 6% or 8%. Except in young infants, short exposure to high concentrations of sevoflurane does not cause significant hemodynamic changes. Timing of the introduction of sevoflurane, the rapidity of increase, and the distraction techniques employed should vary with the child’s mood, level of anxiety, and degree of cooperation. Hyperventilation should be discouraged to avoid apnea during the induction.

If a child has fallen asleep or is well sedated in a parent’s arms or on a stretcher, anesthesia can be induced by the “steal technique,” as originally described by Guedel in 1921 (Calverley 1986). While avoiding moving or awakening the child, 70% nitrous oxide at high flows via an anesthesia mask is held closely over the child’s face. At first the mask should not touch the skin, but as sedation deepens it is placed gently on the face while incrementally increasing the concentration of sevoflurane. Monitoring devices should be attached as soon as possible. Once adequately anesthetized, the child can be transferred to the stretcher or operating room bed if needed ( Fig. 21.6 ).

Once the patient has accepted the mask and is breathing the inhalation agent, it is extremely important to closely follow the progress of induction in order to identify the stages of anesthesia ( Table 21.2 ). The first sign is usually nystagmus, especially if nitrous oxide is being used. The eyes then usually close; the limbs and head may relax; and respiration becomes slower, regular and deeper, and then more shallow and rapid. Often children will have uncoordinated movements during Stage 2 of anesthesia and develop “snoring” or noisy breathing as the anesthetic depth deepens and the patient develops partial upper airway obstruction. Although prepared for this preoperatively, parents should be reminded and reassured that this is normal during the induction of anesthesia. Until the eyelash reflex is gone, nothing should be done to move or stimulate the patient unless airway obstruction significant enough to warrant intervention arises. Nurses and surgeons should not touch the patient until instructed by the anesthesiologist. After induction of anesthesia and the loss of eyelash reflex, a minimum of 2 minutes should pass before IV insertion should be attempted to avoid movement, coughing, or laryngospasm ( ; ).

While traditional technique has been to secure IV access after an inhalation induction, it is not an uncommon practice to proceed with very minor surgical procedures, such as myringotomy tubes, frenulectomy, dressing change, or ophthalmologic exam without IV access ( ; ; ; ). In cases of very short duration and in patients who may have difficult intravenous access, the time attempting IV placement may far exceed surgical time. In appropriate patients without significant comorbidities and with a suspected normal airway, a simple mask anesthetic may be safe and appropriate in these circumstances. Analgesics, if needed for these procedures, can be administered via the rectal, intramuscular, or intranasal route.

For routine elective procedures where excessive fluid or blood loss is not anticipated, a 20- or 22-gauge catheter for children and a 22- or a 24-gauge catheter for infants and smaller children provides sufficient intravenous access. When undergoing minor procedures, it is much better to have a working 22-gauge IV rather than a nonfunctioning 20-gauge IV or multiple infiltrated IVs in an attempt to get larger venous access. If a scalp vein is used, caution is advised. Inadvertent subcutaneous injection of certain drugs, such as calcium, can cause tissue destruction and sloughing of the scalp. If adequate percutaneous sites are not available, use of ultrasound guided access, a central venous catheter, or surgical cut-down may be indicated.

Traditionally, airway manipulation does not occur until secure IV access is obtained. However, with the addition of LMAs for pediatric airway management, an alternative approach of securing an airway prior to IV placement may be undertaken. LMA insertion is much less stimulating than direct laryngoscopy and endotracheal tube placement. Once an adequate depth of anesthesia has been obtained via inhalation induction, an LMA may be safely inserted prior to IV placement ( ; ). This practice may prove beneficial for practitioners working alone or when IV placement may be difficult or prolonged.

Intravenous induction

Induction via the intravenous route has the advantage of speed and avoids the unpleasant odors and sensations of an inhalation induction. The major disadvantage is the difficulty and fear associated with venipuncture in young children. Topical anesthesia, as discussed previously, can significantly reduce pain associated with catheter insertion if used appropriately. Children younger than 6 or 7 years of age have shown less overall benefit from the use of topical anesthetics than older children, probably because young children, although numb, continue to associate needles with pain ( ). Children 8 to 10 years of age and older may prefer an IV induction to a mask, as they may have unpleasant memories from a previous experience. Dorsal hand, forearm, and if needed, antecubital veins are typically the most visible, accessible, and acceptable sites for IV catheter insertion. Wrist, foot, and saphenous veins are other possibilities, but they are difficult to access unless the extremity is immobilized and are painful unless the skin is anesthetized.

The anesthesiologist should always be honest with children, explaining each step of the procedure without frightening them. Using distraction techniques during the placement of the catheter is superior for reducing pain and agitation, compared with using encouragement and complements on good behavior or courage. Before the delivery of any medication, the IV catheter should be flushed to ensure patency and avoid inadvertent subcutaneous injections.

There are certain situations in which intravenous access prior to induction of anesthesia may be considered mandatory. These include patients deemed a “full stomach” who necessitate a rapid sequence induction (pyloromyotomy, bowel obstruction, inappropriate/unknown NPO status), risk for malignant hyperthermia, a suspected difficult airway, and when hemodynamic instability is a concern. have demonstrated that in children with at least two clinically relevant risk factors for perioperative respiratory adverse events, intravenous propofol inductions were significantly less likely to experience perioperative respiratory adverse events at induction compared with those who received inhalational sevoflurane [11% vs. 32%], RR: 3.06, 95% CI: 1.8 to 5.2, P < 0.001).

Rapid sequence induction

Rapid sequence induction (RSI) and intubation is undertaken to reduce the risk of aspiration of gastric contents in patients that may be deemed a “full stomach,” such as those with bowel obstruction, pyloric stenosis, significant gastroparesis, or trauma patients in whom NPO status may be unknown or inadequate. Overall, the risk of pulmonary aspiration in pediatric patients is very low ( ; ). “Classic” RSI involves thorough preoxygenation (denitrogenation), application of cricoid pressure, administration of a hypnotic agent and a rapid acting muscle relaxant in rapid succession, and intubation without positive pressure ventilation. Infants and small children have a reduced apnea tolerance due to increased oxygen demand and poor adherence with preoxygenation, making them high risk for hypoxemia during even brief periods of apnea. A retrospective analysis by revealed a 3.6% risk of transient oxygen desaturation and a 1.7% risk of difficult intubation when classic RSI was performed in children. The technique may be particularly difficult in patients with a history of difficult intubation. The use of cricoid pressure in infants and children can significantly distort the airway at forces well below what is traditionally taught to effectively occlude the upper esophageal sphincter ( ). The recommended pressure to prevent gastric reflux is between 30 and 40 N (newtons, equivalent to 3 to 4 kg), but pressures greater than 20 N cause pain and retching in awake patients, and a pressure of 40 N can distort the larynx and complicate intubation. Performing a modified or controlled rapid sequence induction that avoids cricoid pressure and utilizes gentle mask ventilation (insufflating pressures <10 to 12 cm H ₂ O) until adequate muscle relaxation for intubation is achieved can reduce the risk of hypoxemia without increasing the risk of pulmonary aspiration events ( ; ). Succinylcholine (1.5 mg/kg) or rocuronium (1.2 mg/kg) can be used in conjunction with any of the intravenous induction agents to facilitate a rapid sequence induction, achieving muscle relaxation within 90 seconds.

Maintenance of upper airway patency

Upper airway obstruction can arise during inhalation or intravenous induction of anesthesia, even in healthy infants and children. Tongue displacement, excess soft tissue, velopharyngeal collapse, and laryngospasm can all contribute to upper airway obstruction. Applying pressure to the soft tissue between the rami of the mandible when holding a mask to a patient’s face can push the tongue against the hard and soft palate or displace it posteriorly, leading to occlusion of the oropharynx. Even minimal relaxation of the pharyngeal and laryngeal muscles during induction can significantly reduce oral and nasal passages already compromised by enlarged or increased amounts of lymphoid tissue. Relaxation of the pharyngeal and laryngeal muscles accompanied by a marked increase in respiratory effort and excessive generation of negative pressure, which can occur in response to pain and other stimulation, may result in collapse of the velopharynx. To prevent upper airway obstruction, the pediatric anesthesiologist must hold the anesthesia mask snugly to the patient’s face and perform the triple airway maneuver—neck extension, jaw thrust, and mouth opening—without applying pressure to the soft tissue or causing pain. In addition, a moderate amount of continuous positive airway pressure (CPAP; 10 to 15 cm H ₂ O) can counteract the collapsing force on the relaxed upper airway ( ; ). Continuous monitoring of chest rise and the presence of end-tidal CO ₂ is essential to maximize the effectiveness of maintaining upper-airway patency.

When the patient is sufficiently anesthetized, an oropharyngeal airway may be inserted to further aid in maintaining airway patency. Insertion of an oral airway in an inadequately anesthetized patient risks triggering laryngospasm. The proper size of the oral airway can be estimated by holding the airway to the side of the child’s face extending from the corner of the mouth to the angle of the mandible. See fig17–9 ? CH 17 Equipment Appropriate sizing will optimize placement with the tip of the oral airway just behind the base of the tongue. The preferred method for inserting an oral airway is to slide it gently forward and downward over the tongue while retracting the tongue with a tongue depressor. The technique of inserting the airway upside down and then rotating it into the correct orientation should be avoided in children as it tends to push the tongue posteriorly and obstruct the oral pharynx, especially in infants. When anesthesia is too light for insertion of an oropharyngeal airway, a nasopharyngeal airway is better tolerated. Appropriate size of the nasopharyngeal airway can be estimated by extending the airway from the side of the nare to the tragus of the ear. This type of airway should be well lubricated and inserted gently to avoid mucosal injury and bleeding.

If obstruction is not relieved by these airway maneuvers, the patient may have developed laryngospasm, which can result from laryngeal mucosal irritation during light anesthesia and is often initiated by the aspiration of saliva. Vigorous positive pressure ventilation may push the secretions down into the larynx, which intensifies the spasm and can inflate the stomach, compromising pulmonary gas exchange. The risk of regurgitation and aspiration of gastric contents also increases. A healthy child can tolerate a few moments of laryngospasm. A more successful approach is to maintain moderate continuous positive pressure and synchronous ventilation with the “expiratory” phase of laryngospasm, which is when the vocal cords momentarily relax. By using 100% oxygen and intermittent positive pressure, one can ventilate enough through the glottis to avoid serious hypoxemia. If IV access has already been established, a small dose of propofol (0.5 to 0.8 mg/kg) has been shown to be effective to relieve laryngospasm ( ; ). If rapid oxygen desaturation and bradycardia ensue, IV succinylcholine (2 mg/kg) and atropine (0.02 mg/kg) or IM succinylcholine (4 mg/kg) should be administered without delay to reestablish airway patency ( ; ).

Muscle relaxation

A number of surgical procedures requiring general anesthesia can be performed with an LMA, mask airway, or natural airway with supplemental oxygen. Spontaneous ventilation is maintained and therefore muscle relaxation is not indicated. When an endotracheal tube is indicated, the decision to administer a muscle relaxant to facilitate intubation requires consideration of patient-specific factors such as fasting status, presence of significant reflux, or concern for a difficult airway, along with consideration of surgical needs such as a relaxed surgical field or the need for controlled ventilation. In adult patients, muscle relaxation is routinely used to facilitate intubation, but in pediatric patients tracheal intubation can often be successfully performed without the use of a muscle relaxant. The depth of anesthesia achieved by at least 4% end-tidal concentration of sevoflurane provides satisfactory intubating conditions in most infants and children ( ). Propofol 3 to 4 mg/kg and a short-acting opioid can be used for intubation without a muscle relaxant, but it is not as consistent in providing adequate conditions ( ). A survey of pediatric anesthesiologists in the United States in 1999 revealed that approximately 40% used an inhalation anesthetic without muscle relaxant as their most frequent technique for tracheal intubation in healthy infants and children ( ).

Nondepolarizing muscle relaxants such as rocuronium and vecuronium are the most commonly administered muscle relaxants to facilitate tracheal intubation. When administering a muscle relaxant, a lower dose of intravenous or inhalation anesthetic is required to achieve adequate intubating conditions. The depolarizing muscle relaxant succinylcholine has been associated with hyperkalemic cardiac arrest in patients with undiagnosed muscular dystrophy. Because of this, its use is reserved for situations where rapid securement of the airway is necessary or when IV access is not readily available, as it can be administered IM. With the availability of sugammadex to rapidly reverse even large doses of rocuronium, the indication for the use of succinylcholine continues to decline.

Airway management is discussed in detail in Chapter 4 (Airway Physiology and Development) and Chapter 19 (Normal and Difficult Airway Management).