Induction of anesthesia is usually via an inhalational or intravenous route, though intramuscular ketamine (Hannallah and Patel 1989) and rectal methohexital (Forbes et al. 1989) could also be used. Inhalation induction is the most common method and allows for a more rapid, less stressful induction for a younger child (Kotiniemi and Ryhanen 1996; Kain et al. 1999). In children, the higher minute ventilation to functional residual capacity ratio and the increased blood flow to the vessel-rich organs, like the brain, allow for more rapid equilibration of volatile anesthetic in neonates, infants, and small children. Halothane has been replaced by sevoflurane as the agent of choice for inhalation induction. The minimal alveolar concentrations, solubility, and side effects of different volatile anesthetics are provided in Table 2. Sevoflurane is less pungent than isoflurane and desflurane and causes less myocardial depression and sensitivity to arrhythmias compared to halothane (Navarro et al. 1994; Holzman et al. 1996). Emergence delirium, however, has been more of a problem with sevoflurane than compared with other volatile agents.

Intravenous induction is preferred in older children and those with full stomachs, severe sleep apnea, a propensity to obstruct airway on induction, and medical conditions such as aortic stenosis. Nitrous oxide in oxygen is commonly used in older children to facilitate intravenous access. The topical use of a eutectic mixture of local anesthetics like EMLA, composed of 2.5 % prilocaine and 2.5 % lidocaine, produces anesthesia of the skin after application with an occlusive dressing for about 60 min. The time delay, need for preparation of multiple potential sites, and discomfort related to an approaching needle may, nevertheless, act as drawbacks with this method. Induction agents commonly used are propofol, thiopental, etomidate, and ketamine. Doses of these agents and their effects on the various systems are presented in Table 3. Lidocaine is often used before or along with propofol and etomidate due to pain on injection, although it is not always successful (Mirakhur 1988). Propofol has the advantages of more rapid awakening, less emergence delirium, and less nausea but does cause more hypotension if given in large doses. Etomidate is more cardiac stable but causes myoclonus and adrenal suppression, which may not be a problem with induction doses (Bergen and Smith 1997). Ketamine is a dissociative anesthetic and an NMDA blocker, with analgesic effects that maintain respiration but increase secretions, intracranial pressure, blood pressure, heart rate, and occurrence of emergence delirium (Reich and Silvay 1989).

Airway management is crucial for general anesthesia. An infant airway is different from that of older pediatric and adult airways in a number of ways; the most important of which are larger occiput, larger tongue relative to size of the oral cavity, more cephaled larynx (C3–4), narrower epiglottis, and the cricoid cartilage being the narrowest portion of the larynx and not the vocal cords. The practical implications are that for intubation, the infant head does not require to be extended (maintain in neutral position) for the laryngeal/pharyngeal and oral axes to line up; straight laryngoscope blades (Miller/Phillips) may be preferable to curved ones (Macintosh); and, it may be preferred to use uncuffed endotracheal tubes compared to cuffed ones (Marraro 2002). Recent practice has changed the use of cuffed endotracheal tubes with very short high-volume low-pressure (HVLP) cuffs made from polyurethane, with improved sealing characteristics (Weiss et al. 2004). There are myriads of intubation assist devices available in the difficult airway armamentarium (e.g., Glidescope® (Saturn Biomedical System Inc., Burnbaby, Canada), intubating laryngeal mask airway, and fibreoptic bronchoscopy) (Sunder et al. 2012).

Airway management is usually accomplished either by use of mask anesthesia, use of laryngeal mask airways, or use of endotracheal tubes. Mask anesthesia using appropriate size mask (5), oral or nasal airways, and chin-lift/head-tilt and jaw-thrust maneuvers as required are usually used for shorter procedures such as closed fracture reduction, excision of extra digits, etc. The laryngeal mask (LMA) is a supraglottic airway device that was designed by British anesthesiologist Dr. Brain. It is placed such that the aperture in the mask is positioned at the laryngeal inlet. It is often used instead of the mask as it helps free the anesthesiologists’ hands. While it is less invasive than an endotracheal tube, is relatively easy to insert, and has an important role in the difficult airway algorithm, both mask and LMA are contraindicated in patients with full stomachs as they do not protect against risk of pulmonary aspiration of gastric contents. Also, these may not be the ideal methods for patients with low lung compliance who require controlled ventilation as gastric insufflation with air may occur with use of higher airway pressures for ventilation.

Endotracheal tubes (ETT) used today are made of polyvinylchloride and are disposable. They are calibrated according to internal diameter (ID) in mm, are beveled, and usually have an aperture opposite to the bevel and just above the distal tip (Murphy’s eye), which allows for alternate path of airflow in case of distal tube occlusion. The appropriate size recommended is 2–2.5 mm ID for a premature baby, 3.0–3.5 mm ID for term to 3-month-old, 3.5–4.0 mm ID for 3–9-month-old, and 4.0 for a 9–18-month-old and for >2-year-old children. The formula for the ID of uncuffed ATT is given by ID (mm) = (age (year) +16)/4 and that for microcuffed ETT is determined by age (year)/4 + 3.5 (mm) (Duracher et al. 2008). Common methods of ETT placement include deliberate main stem intubation with subsequent withdrawal of the ETT 2 cm above the carina (“main stem” method), alignment of the double black line marker near the ETT tip at the vocal cords (“marker” method), or placement of the ETT at a depth determined by the formula: ETT depth (cm) = 3 times ETT size (mm ID) or ETT depth (cm) = age (year)/2 + 12 (“formula” method). The formula method only placed the ETT at the appropriate depth 42 % of the time, according to a study that compared these methods (Mariano et al. 2005). The preferred technique is via auscultation. Confirmation of appropriate ETT placement is done by auscultation, confirming chest rise, capnography, and condensation in the ETT. Air leak at an inspiratory pressure of 20–25 cm H₂O is thought to prevent excessive mucosal pressure. For microcuffed ETT, a cuffed tracheal tube with a smaller diameter is selected, which does not wedge within the susceptible cricoid, and the airway is sealed within the trachea using a cuff (Weiss et al. 2006). In contrast to cricoidal sealing, tracheal sealing with an HVLP cuff allows precise estimation and adjustment of the pressure exerted by the cuff on the tracheal mucosa. Down syndrome patients should be intubated with manual in-line cervical stabilization technique until atlantoaxial instability is ruled out.

Maintenance of anesthesia can be done in various ways including inhalation and intravenous anesthetic agents. Inhalational agents used typically may be sevoflurane, isoflurane, or desflurane (Table 2), and common parenteral intravenous (IV) agents are benzodiazepines, propofol, muscle relaxants, and opioids. Balanced anesthesia is a triad of narcosis (analgesia), amnesia (anesthetics), and relaxation (volatile anesthetics or muscle relaxants). Analgesia can be achieved with opioids, nonsteroidal anti-inflammatory agents like IV ketorolac, and IV acetaminophen (doses and salient considerations are discussed under acute postoperative pain management at the end of the chapter). The amount of any medication is typically weight based and tailored also to patient conditions and surgery. Neuromuscular-blocking agents (NMBA) are used to facilitate tracheal intubation, prevent movement, and provide muscle flaccidity for certain procedures. In general, nerve signals cause release of neurotransmitter acetylcholine at synaptic clefts, which binds to postjunctional acetylcholine receptors, which then activates ion channels ultimately causing muscle contraction. NMBA act at the neuromuscular junction by either competing with acetylcholine for the receptor (non-depolarizing) or by activating both receptive sites and maintaining a depolarized muscle membrane so that acetylcholine cannot act on it (depolarization). The different muscle relaxants commonly used, doses, site(s) of metabolism, and duration of action are presented in Table 4. Importantly, neuromuscular transmission is immature in neonates and infants below the age of 2 months (Goudsouzian and Standaert 1986). Moreover, the organs for metabolizing and eliminating these agents (kidneys/liver) may also not be mature. Reversal of muscle relaxation is generally required after use of non-depolarizing NMBA, which is done by use of acetylcholinesterases. Typically, neostigmine and edrophonium are used – these drugs inhibit the enzyme that metabolizes acetylcholine (acetylcholinesterase) and thereby increase the available concentration of acetylcholine in order to overcome the competitive inhibition at the receptor. These “reversal” agents are used with anticholinergic agents to counter unwarranted muscarinic effects of acetylcholine.

Emergence from anesthesia is akin to flight landing and ideally should be smooth and safe. During emergence, the anesthetic is discontinued, neuromuscular block is reversed, and when the patient meets certain criteria (responding to commands, acceptable minute ventilation, normoxic, and good headlift/hand grasp), the trachea is extubated. In patients with easy airways and not at risk for aspiration, the trachea may be extubated under deep anesthesia. Postoperative care includes continued monitoring of vital signs, maintaining an open airway, pain management, and dealing with possible postoperative complications including hypoxia, hypercarbia, hypo- or hypertension, agitation, and weakness. Emergence delirium (ED) also referred to as emergence agitation (EA) is a well-documented phenomenon with an incidence in all postoperative patients of 5.3 % with a more frequent incidence in children (12–13 %) (Mason 2004). The incidence of emergence delirium after halothane, isoflurane, sevoflurane, and desflurane ranges from 2 % to 55 %, with a higher incidence noted for the newer inhalation agents, desflurane and sevoflurane. Emergence delirium is defined as a dissociated state of consciousness in which the child is inconsolable, irritable, uncooperative, typically thrashing, crying, moaning, or incoherent (Wells and Rasch 1999). Characteristically these children do not recognize or identify familiar and known objects or people. Generally, these episodes are self-limiting (5–15 min) but are unnerving to parents and can result in physical harm to the child. Ten factors were associated with ED including: (1) younger age (4.8 vs. 5.9 years), (2) no previous surgery, (3) poor adaptability and anxiety (Kain et al. 1996), (4) ophthalmology and (5) otorhinolaryngology procedures, (6) sevoflurane, (7) isoflurane, (8) sevoflurane/isoflurane, (9) analgesics, and (10) short time to awakening (Voepel-Lewis et al. 2003).

Weakness from a residual neuromuscular block is another postoperative complication, with an incidence between 4 % and 50 %, depending on the diagnostic criteria, the type of NMBA, the administration of a reversal agent, and the use of neuromuscular monitoring (Plaud et al. 2010).

After minor procedures, when no regional anesthesia is used, the use of these systemic analgesic drugs is indicated to provide analgesia postoperatively or to supplement local analgesia. Non-opioids, such as acetaminophen and NSAIDs, play an increasing role as components of multimodal analgesia in children.