46 The Postanesthesia Care Unit and Beyond
CHILDREN’S RECOVERY FROM ANESTHESIA is substantively different from that of adults. Although both age groups share the key elements of regaining consciousness, controlling pain, and maintaining a patent airway, the nature and timing of these elements are different. In young children, emergence from inhalational agents can be quite rapid because of the increased minute ventilation, increased blood flow to the vessel-rich group (see Chapter 6), and decreased total body muscle and fat stores, whereas emergence from intravenous agents in infants may be delayed because of decreased clearance as a result of reduced liver blood flow and enzyme activity. The quality of the emergence is different in children and adults because agitation (i.e., emergence delirium) after sevoflurane and desflurane is more common in young children than in adults. The criteria used to evaluate emergence from anesthesia or sedation must be consistent with the developmental level of the child. The nature and rapidity of complications that can occur during emergence require careful planning and anticipation of problems. Parents should be considered partners and active participants in effective postoperative management.
Perioperative Environment
Equipment (Table 46-1) and available medications (Tables 46-2 and 46-3) should be standardized throughout the unit and be compatible with transport monitors and other devices used in corresponding high care facilities (e.g., PICU). An important safety precaution is the use of preprinted weight-based emergency drug doses for each child; these rapid reference sheets can be attached to each child’s bed or chart on admission so that a quick dose recommendation is readily available. Alternatively, the electronic record should have precalculated emergency drug doses for each child. This practice may also reduce the risk of drug errors in an emergency situation.
Oxygen supply with regulated flows
Oxygen facemasks and face tents for spontaneous ventilation (various sizes)
Resuscitation bags, self-inflating (Ambu)
Anesthesia facemasks for positive-pressure ventilation (pediatric sizes: 0, 1, 2, 3; adult sizes: small, medium, large)
Oral airways (sizes 00, 0, 1 to 5)
Nasal airways (sizes 12F to 36F)
Suction and appropriate suction catheters (sizes 6.5F to 14F); tonsil-type (Yankauer) attachment
Needles, syringes, alcohol wipes, Betadine solution, gauze pads
Pulse oximeter and sensors (size appropriate, stick-on type preferred to clip-on type)
Electrocardiograph, monitor and pads
Laryngoscopes with blades: Miller 0, 1, 2, 3; Macintosh 2, 3, 4; extra laryngoscope bulbs and batteries
Endotracheal tubes, sizes 2.0-mm internal diameter (ID) through 8-mm ID; cuffed and uncuffed tubes for all sizes when available
Laryngeal mask airways, sizes 1, 1.5, 2, 2.5, 3, 4, 5
ProSeal laryngeal mask airway, sizes 1.5, 2, 2.5, 3, 3.5, 4, 5
Fast-track intubating laryngeal mask airway
Stylet appropriate for each endotracheal tube size
Syringe for endotracheal cuff inflation
Tape and liquid adhesive for endotracheal tube fixation
Intravenous catheter (14 gauge) with 3-mm ID endotracheal tube adapter for emergency cricothyroidotomy (see Fig. 12-25)
Cricothyrotomy kits appropriate for age (see Figs. 12-25 and 12-26; see also E-Figs. 12-5 through 12-10)
Backup resuscitation bags and masks and oral airways for each bedside
Intravenous infusion solutions, tubing, drip chambers
Supplies for intravenous cannulation, catheter sizes 24 to 14 gauge
Cutdown tray, tracheostomy, and suture sets
Central venous catheter insertion sets (3F to 7F single and multiple lumen)
Tube thoracotomy set and system for suction and underwater seal
Defibrillator (adult, child paddles)
Pressure transducer system and oscilloscope monitor
Sterile gowns, gloves, masks, towels, drapes
Hydrocortisone, dexamethasone, methylprednisolone
Lidocaine (intravenous and topical)
Propranolol, atenolol, esmolol, labetalol
Succinylcholine and rocuronium
For inhalation: racemic epinephrine (2.2% at 0.05 mL/kg, common in the United States) or epinephrine 1 : 1000 (0.1%), 0.5 mL/kg, maximum of 5 mL
*Alternative or additional medications may be needed.
Nurses, residents, fellows, attending physicians, and other personnel working in the perioperative area should be competent in the provision of neonatal and pediatric advanced life support. The team should participate in mock codes and simulations to train for an emergency. Patient sign outs should be standardized, include checklists, and follow an institution-specific protocol.1 All personnel should be familiar with resuscitative equipment and be able to use it instantaneously. We recommend instituting equipment and policies according to the guidelines for the pediatric perioperative anesthesia environment published by the American Academy of Pediatrics.2
Central Nervous System
Pharmacodynamics of Emergence
Emergence from anesthesia is faster after a relatively insoluble inhalational anesthetic agent such as sevoflurane or desflurane than it is after a more soluble agent such as halothane.3 However, the clinical importance of these differences may be minimal and vary with the duration of anesthesia and the coadministered medications. Differences in the times to discharge from the PACU and the hospital between inhalational agents are even more difficult to detect when specific comparisons are made because so many other factors, such as pain management, agitation, availability of hospital beds, and family circumstances, affect discharge readiness.
The age of the child exerts a minimal influence on the wash-out of inhalational anesthetic agents and has little impact on the rapidity of emergence, although age may be a factor for infants younger than 1 year of age.4 However, the overall clinical implications of age-related differences in emergence are exceedingly difficult to detect.5 The speed of emergence correlates more closely with the duration of anesthesia. The greater the duration of anesthesia, the more the tissue compartments become filled with these anesthetics and the more time it takes to eliminate these anesthetics and for the child to recover. For example, emergence from 30 minutes of sevoflurane anesthesia is significantly faster than emergence from 2 hours of anesthesia, which is more rapid than from 8 hours of anesthesia.6 This relationship between emergence time and the duration of anesthesia has less relevance as inhalational anesthetics have become less soluble (e.g., desflurane).
Emergence from intravenous agents can vary significantly from that of inhalational agents. Several studies have evaluated the quality and rapidity of emergence after intravenous anesthetic agents compared with that after inhalational agents. For outpatient surgery, emergence after propofol anesthesia is as rapid as that after sevoflurane but with far less agitation and pain behaviors.7,8 The recovery characteristics of propofol with remifentanil total intravenous anesthesia have been compared with those after desflurane inhalational anesthesia. Recovery is as rapid as that after desflurane with nitrous oxide, with a similar incidence of nausea and vomiting but with much less agitation.9
Midazolam is rarely used for maintenance of anesthesia but is often used as an oral or intravenous premedication for anxiolysis and amnesia in the preinduction period. There is evidence that the addition of midazolam in the preinduction period to an inhalational or propofol anesthetic may delay early emergence after brief anesthesia. However, this effect of midazolam is attenuated after anesthesia of greater duration, or when considering late emergence, this effect is minimal.10 Midazolam does not affect the incidence of postoperative agitation.11,12
Emergence Agitation or Delirium
Emergence agitation (i.e., emergence delirium [Videos 46-1 and 46-2]) was first described in a large cohort of postsurgical patients almost 40 years ago.13 From a clinical perspective, it is often impossible to differentiate pure agitation from delirium. Delirium implies a specific set of thought disorders and hallucinations based on the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV). Despite numerous investigations, differentiating emergence delirium from postoperative pain has also proved difficult. Emergence delirium usually manifests as thrashing, disorientation, crying, and screaming. The child is unable to recognize parents, familiar objects, or surroundings; is inconsolable; and talks irrationally during early emergence from anesthesia. Emergence delirium occurs more often in children (rate of 10% to 20%) than in adults, particularly in those younger than 6 years of age.14,15 It may in part reflect differences in clearance of insoluble inhalational agents from the central nervous system.
An emergence delirium scale has been developed and validated that may provide clinicians and investigators with a tool to differentiate emergence delirium from pain.16 Tables 46-4 and 46-5 show two scoring systems used to evaluate emergence behaviors in children. In evaluating emergence delirium with the Pediatric Anesthesia Emergence Delirium (PAED) scale after anesthesia, preliminary evidence suggested that values greater than 10 were consistent with emergence delirium in 37% of patients,17 although that cutoff value has not been useful for others.18 Later evidence suggested that values greater than 12 provided greater sensitivity and specificity.17 In the PICU, evidence suggests that a PAED score greater than 8 predicts emergence delirium.19
*A higher postanesthesia behavior assessment (PABA) score is associated with a greater degree of postanesthetic distress.
From Przybylo HJ, Martini DR, Mazurek AJ, et al. Assessing behavior in children emerging form anaesthesia: can we apply psychiatric diagnostic techniques? Pediatr Anesth 2003;13:609-16.
Our understanding of emergence delirium or agitation continues to evolve, but it is clear that it occurs after surgical procedures and after procedures that are free from pain, such as magnetic resonance imaging.14,20,21 Emergence delirium appears to occur more frequently after use of less-soluble inhalational anesthetics such as sevoflurane and desflurane than after more-soluble inhalational anesthetics such as halothane and isoflurane,22,23 even though some data suggest otherwise.24 There may be a greater incidence of emergence delirium after painful procedures; emphasizing the difficulty separating agitation due to pain from agitation due to the direct effects of the inhalational agents on the sensorium.25 Emergence delirium occurs more commonly in children younger than 6 years of age than in older children, usually lasts 5 to 15 minutes, and resolves spontaneously if the children are left undisturbed or they are held by their parents.14
Several strategies have been used to decrease the duration and intensity of emergence delirium. Effective regional analgesia, opioids, ketamine, α2-agonists, and propofol can prevent or treat emergence delirium. Low-dose fentanyl (2 µg/kg intranasally or 1 to 2 µg/kg intravenously) decreases the duration and intensity of emergence delirium,26 even in the absence of significant painful stimuli.20 Other adjunctive agents used to treat this phenomenon include ketorolac and acetaminophen (for myringotomy with ventilation tube placement) and midazolam; the effectiveness of midazolam, however, has been mixed.27,28 Dexmedetomidine can decrease the incidence of emergence delirium,29,30 but the cost-effectiveness of this treatment compared with others requires evaluation. Administration of propofol by continuous infusion or by bolus at the end of surgery appears to be preventative,31,32 although these findings have not been consistent.18 The induction dose of propofol administered at the start of the case does not appear to prevent postoperative emergence delirium.33 Regional analgesia in the form of caudal blocks can reduce the incidence of emergence delirium, although this effect is probably related to improved pain control, which eliminates pain as a source of agitation.34,35
Although there is no evidence of long-term consequences, in the current era of fast-tracking anesthesia, emergence delirium can represent a significant time expenditure for nurses in the PACU. Discharge from the PACU may be delayed while waiting for the delirium to wane or for the effects of the interventional drugs to dissipate. Injury to the child who is extremely agitated is a concern. Parental satisfaction decreases when severe emergence delirium occurs. Although the impact of extreme delirium is not fully known, evidence suggests that the incidence of postoperative maladaptive behaviors increases among children who experience marked emergence delirium.36
Respiratory System
Extubation in the Operating Room or Postanesthesia Care Unit
For children who are extubated in the PACU, respiratory insufficiency is the most worrisome and most frequent complication. It comprises approximately two thirds of critical perioperative events when it is associated with emergence from anesthesia.37 Respiratory insufficiency may manifest in the form of difficulty breathing, or it may be more subtle as anxiety, unresponsiveness, tachycardia, bradycardia, hypertension, arrhythmia, or seizures. Cardiac arrest is a late manifestation. When any of these conditions are present, respiratory insufficiency must be considered as the root cause. Hypoxemia, hypoventilation, and upper airway obstruction are the three most common adverse respiratory events that occur in children in the PACU, and this is particularly true for children after tonsillectomy complicated by obesity and possible obstructive sleep apnea and for those who have undergone diagnostic bronchoscopy.
Hypoxemia
Hypoxemia may result from hypoventilation, diffusion hypoxia, upper airway obstruction, bronchospasm, aspiration, pulmonary edema, pneumothorax, atelectasis, or rarely from postobstructive pulmonary edema or pulmonary embolism. Hypoxia occurs more rapidly and may be more profound during emergence from general anesthesia because general anesthesia inhibits the hypoxic and hypercapnic ventilatory drive, reduces functional residual capacity, and alters hypoxic pulmonary vasoconstriction. Shivering may further increase oxygen consumption by a factor of two to five38,39 and exacerbate hemoglobin desaturation.
Postoperative hemoglobin desaturation is more common in children with or recovering from an active upper respiratory tract infection due to increased airway reactivity, atelectasis, and increased secretions than in children without a history of upper respiratory tract infection.40,41 In neonates, hypoxia increases ventilation for approximately 1 minute but then depresses the respiratory drive (i.e., respiratory rate and tidal volume).42 The ventilatory response to hypoxia in formerly preterm infants with severe bronchopulmonary dysplasia who sustained an hypoxic injury is delayed for several months, placing them at particular risk for desaturation in the perioperative period.43