It is an important task for every pediatric anesthesiologist to conduct a smooth anesthesia induction when a pediatric patient needs to undergo lens surgery. And it is most important to interact with the child in a calm reassuring voice when he or she is unable to cooperate, crying, or difficult to communicate with. Pediatric anesthesiologists can also engage the child’s attention by telling stories or performing magic tricks. In addition, the presence of parents at the time of anesthesia induction may strengthen or replace premedication. If the above management does not work, intranasal dexmedetomidine or intravenous midazolam can be ultimately administered. Inhaled induction of anesthesia with sevoflurane can be performed after the child is sedated.

For a pediatric patient who is cooperative, mask inhalation of 8 % sevoflurane in oxygen at the rate of 6–8 L/min is used for anesthesia induction. The moment the child loses consciousness, the parents (if present) should be asked to leave and the focus should be on the respiratory tract (Fig.10.2).

During the course of inhaled induction with sevoflurane, most children experience “excitation,” including airway obstruction, autonomic movement of the limbs, rigidity, tachypnea, and tachycardia. As the anesthesia deepens, these symptoms usually go away within a few minutes. After the “excitation period,” intravenous access can be established. Previous study has reported that there is no response to intravenous cannulation in 3–4 min following mask inhalation of sevoflurane.

As there is slight surgical trauma and no muscle relaxant is needed, an appropriate depth of anesthesia can be maintained via the inhalation of roughly 3 % sevoflurane during anesthesia. Additional intravenous injection of 10–20 mg propofol is administered intermittently to reduce any emerging agitation in the child, and the ventilation can be maintained by spontaneous respiration or synchronized intermittent mandatory ventilation (SIMV) when the child shows respiratory depression. The perioperative liquid supplement is administered on physiological demand given the short duration, slight surgical trauma, and minimal blood loss of lens surgery.

In lens surgery, stabilization of the eye at primary position may facilitate surgical procedures. But in clinical practice, an upward movement of the eye, also known as Bell’s phenomenon, often occurs. This phenomenon is mainly associated with insufficient depth of anesthesia; therefore, the treatment lies in increasing the depth of anesthesia by additional intravenous administration of anesthetic agents or increasing concentration of inhaled anesthetics. It is worth mentioning that special attention should be paid to changes in respiratory rhythms and amplitude in children with spontaneous ventilation, and assisted mechanical ventilation should be used if necessary. However, in a child inhaling sevoflurane with an LMA with spontaneous ventilation, the increased concentration of sevoflurane can inhibit the respiratory system. As a result, patients display a lower tidal volume and an accumulation of carbon dioxide, which may lead to a downward movement of the eye that interferes with surgical procedures. Little is known of the underlying mechanism at present, but the treatment is not difficult since the eye will return to the primary position via assisted ventilation with end-expiratory carbon dioxide concentration decreased to the normal range.

Different from endotracheal intubation, which can completely isolate the respiratory tract, the LMA forms an unpressurized sealing loop in the throat by separating from the surrounding tissue. Hence, the pressure should not exceed 20cmH₂O through mechanical ventilation, and if the pressure is too high, air leakage will occur, and the air may leak into the stomach.

The selection of LMA size depends on the child’s body weight. Based on the experience of ZOC’s anesthetic team, the 1.5-size LMA should be applied for infants less than 6 months of age (even though their weight is less than 5 kg). Moreover, due to the soft tissue and structure of the infant, the median method can be adopted when the LMA is inserted, with the success rate over 95 %. Before the insertion of LMA, it is not necessary to have released all the air from the cuff because it can be inserted more easily with the cuff inflated. After the location is confirmed, there is no need to inject air into the cuff of LMA. If resistance occurs while the median method is being used for LMA insertion, a rotation method should be adopted to insert the LMA. Due to the narrow pharyngeal cavity of the infant in addition to the loose connective tissue, avoid any violent insertion that may induce hemorrhage in the oropharynx mucosa.

When an LMA is used, special attention should be paid to the following issues: (1) It is contraindicated for patients with full stomach and residual gastric contents. (2) Due to the higher airway pressure (>20cmH₂O), this can easily lead to air leakage into the stomach, which may induce vomiting. Patients with severe obesity or low lung compliance are recommended to undergo assisted or controlled breathing with LMA. (3) It is contraindicated in patients with potential airway obstruction, such as tracheal compression, tracheomalacia, pharyngolaryngeal neoplasm, abscess, and hematoma. (4) Laryngospasm can easily occur when LMA is inserted under insufficient anesthesia, and this should be avoided. (5) Jaw lift is not allowed after the LMA is inserted; otherwise, laryngospasm or location shift will occur. (6) In the case of patients with abundant respiratory secretions, it is not easy to clear them using LMA.

This is commonly used in pediatric lens surgery, with drug use mode of anesthesia induction as follows: intravenous general anesthetics + narcotic analgesics + muscle relaxants (see Table 10.2). Intravenous general anesthetics consist of etomidate, imidazole, diazepam, and propofol. Narcotic analgesics include ketamine and fentanyl. Muscle relaxants are made up of atracurium, vecuronium, and cisatracurium.

Due to age-associated anatomical differences, there are some technical differences between laryngoscopy in infants and young children and that in adults. Since an infant’s glottis is higher, it is “more forward” under laryngoscope observation; besides, it is difficult to control the epiglottis with a laryngoscopic blade since the infant’s epiglottis is longer than that of an adult and it is hard and slippery in a U shaped. Thus, in the case of children under 2 years old, a straight laryngoscope blade is more commonly used. Since the narrowest portion of the pediatric airway is beneath the glottis, be sure not to insert the catheter too violently if resistance is felt, even if it has been passed through the glottis without difficulty.

It is necessary to maintain sufficient depth of anesthesia during the course of surgery to avoid the cough reflex induced by tracheal tube stimulation. Apart from the use of muscle relaxants at the time of tracheal intubation, there is no need for additional muscle relaxant during the process of surgery. The pattern of controlled respiration is adopted during anesthesia, with an intermittent assisted intravenous injection of 10–20 mg propofol to reduce emergence agitation in the child.