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.
The environment in the pediatric postanesthesia care unit (PACU) is unique and challenging. The staff and facility of any institution in which children recover after surgery must understand these challenges and be prepared to manage children through the difficult process of emerging from the anesthetized state to the new reality of postoperative consciousness. Early admission of parents to PACU and use of rocking chairs to permit parents to comfort their children is a common means of facilitating recovery.
The ideal perioperative environment is one that combines aspects of safety, ergonomics, and comfort for the child, family, and caregivers. The environment should be child specific and staffed by experts in child care. This should start with the admission process and conclude with the discharge to home or the hospital ward. Ideally, a child should be under the care of the same team throughout his or her hospital stay. For example, the child can be admitted by the nurse who will later take care of the child and the family in the PACU. In some hospitals, this is achieved by creating an integrated perioperative environment, in which children are admitted, prepared, and allowed to recover in the same space, with the same nurses and child life specialist. Familiarity with personnel and surroundings is a great stress reliever for children and families; it also fosters trust and comfort.
Privacy and shelter from noise is an important aspect of the setup. The ability to spend time with the child without being disturbed is something that many families appreciate, and this helps the child to deal with the stress of a strange environment. Most modern PACUs have moved to individual patient rooms or cubicles for preoperative and postoperative care, similar to a typical pediatric intensive care unit (PICU).
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.
Cricothyrotomy kits appropriate for age (see Figs. 12-25 and 12-26; see also E-Figs. 12-5 through 12-10)
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
Transport from the operating room to the PACU should be carried out under the direct supervision of a trained expert. The security and patency of the airway, intravenous and arterial lines, drains, and urinary catheters should be checked before transport. The security and patency of the tracheal tube (if the airway remains intubated) or laryngeal mask airway, all intravenous lines, the arterial line, chest tubes, drains, and the urinary catheter should be checked before transport. Children should be in presentable condition (e.g., removal of blood and secretions) before and kept normothermic during transport to the PACU or PICU.
Unless children are awake, with protective airway reflexes intact, or unless there is a specific contraindication, it is sensible to transport extubated children in the lateral position (i.e., tonsillectomy recovery position) so that the tongue lies away from the larynx, and secretions and vomitus leave the mouth rather than enter the larynx, causing aspiration or airway obstruction. To assess ventilation and maintain a patent airway with the child in the decubitus position, we recommend applying the thumb to the forehead to extend the neck and holding the fingers (the finger tips are the most sensitive part of the hand) over the mouth (or nose) to feel for exhalation. A precordial stethoscope may also be used to auscultate respirations. If the child is breathing room air, a pulse oximeter can indicate oxygenation and serve as a crude measure of ventilation because desaturation will occur quickly if hypopnea develops. However, if oxygen is provided to the child, the oximeter can no longer serve as a guide to ventilation, because desaturation will not occur until a sustained apnea occurs. For sleepy children, the precordial stethoscope and portable oxygen saturation monitor can trend ventilation, oxygenation, and the heart rate within the previously described provisos. We recommend that children in a potentially unstable condition be transported with a pulse oximeter, capnogram, an electrocardiographic (ECG) monitor, and a blood pressure cuff or a transduced arterial line. The monitoring lines, intravenous drips, infusion pumps, and other equipment should be clearly labeled and simplified before transport. For sick children, those with intubated tracheas, and children with potentially difficult airways, an appropriate resuscitation bag, facemask, oral airway, oxygen tanks (oxygen levels should be checked), functioning laryngoscopes, tracheal tube, and medications (including atropine and succinylcholine) should be carried en route to the PACU or PICU. A tackle box containing all of this equipment is helpful, especially when children are transported to the PICU in an elevator. Children receiving vasoactive drugs require infusion pumps so that these agents can be continuously administered at precise titrated rates.
Transport to the PACU or PICU is a time of potential danger. Distance and duration of travel should be minimized. When designing pediatric perioperative areas or reallocating space, strong emphasis should be placed on ergonomics.
A child often appears awake after the stimulation of tracheal extubation and transfer to the stretcher but may subsequently become obtunded and obstruct the airway during transit to the PACU or PICU. Just as frequently, children may become restless during transit. Although restless behavior has many causes, hypoxia should never be overlooked. The guard rails on the stretcher should always be raised when the child is in it. Most importantly, the anesthesiologist must remain vigilant throughout the transfer.
On arrival in the PACU, attention should first be directed to the airway, ensuring it is patent and not obstructed; to the color of the lips and mucous membranes; to the oxygen saturation; and to the adequacy of ventilation, perfusion, and central nervous system function. Admission heart rate, blood pressure, oxygen saturation, respiratory rate, and temperature should be recorded on arrival. The nurse-to-patient ratio should be 1 to 1 for sick children and 1 to 2 or 1 to 3 for routine cases. Supplemental oxygen is administered as indicated, recognizing the limitations of the monitors to detect ventilation in such cases. Many children object to having an oxygen mask fixed to their faces; a funnel-type mask or open hose with large flow rates may be less objectionable (although less optimal). Thereafter, report should be given to the nurses and physicians in attendance. Ideally, the nurses taking care of the child postoperatively are already familiar with the child and family from the preoperative setting.
The standardized transfer of care report should include, at a minimum, the child’s name, institutional identification code, age and gender, preoperative vital signs, and specific circumstances, such as a language barrier or developmental delay. The size and location of catheters, a description of the child’s current problem, medical history, medications, allergies, operative procedure, and pertinent surgical problems should be outlined. The anesthetic should be summarized and include the premedication and anesthetic agents used at induction and for maintenance, techniques used, reversal of neuromuscular blockade (i.e., adequacy of the train-of-four response), estimated blood loss, fluid replacement (including amount and type of solution), urine output, and vasoactive drugs, bronchodilators, and intraoperative medications (e.g., antibiotics) used. Regional anesthesia issues, such as epidural use and location, drug choice and concentration, use of adjuvants, effective level of analgesia, and drug infusion rate should be clearly communicated. Administration of analgesics (time and dose), local blocks and wound infiltration with local anesthetics, problems with surgery or anesthesia (e.g., difficult intravenous access, difficult intubation, intraoperative hemodynamic instability, cardiac changes), and potential problems in the PACU should be listed.
The anesthesia team must remain with the child until he or she has stable vital signs and the PACU team is comfortable and ready to assume responsibility for the child. Physicians who will be in charge of taking care of the child in the PACU after the anesthesia team leaves must be clearly identified by name, and ways to reach them (e.g., pager number) must be given to surgeons, anesthesiologists, and regional block and pain services.
All children should be monitored continuously in the PACU. At the very least, this should include continuous pulse oximetry and intermittent noninvasive blood pressure and temperature monitoring. Most PACUs also monitor the electrocardiogram continuously, although some limit this to children with cardiac disease or complex multiple-organ disease. During emergence, many children are so active that it is impossible to maintain the monitoring devices in place. If the child is not hypoxic and is sufficiently awake to remove the monitors, he or she probably does not require the monitors any longer. If the child falls back to sleep, then a pulse oximeter probe should be reapplied, particularly for at-risk children such as those with obstructive sleep apnea. For a child who is physically or mentally challenged, it may be necessary to apply light restraints until he or she is oriented and awake.
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 (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
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
In most cases, extubation may be safely performed in the operating room. However, a child’s condition may necessitate delayed extubation at a more appropriate time in the PACU or PICU. There is widespread agreement that children who have been anesthetized with a full stomach, children at risk for airway obstruction, those with difficult airways, premature infants, and other infants predisposed to apnea should be awake before extubation of the trachea is attempted. Beyond this, the timing of extubation is a matter of individual judgment. For example, the practice at some institutions is to extubate the trachea when a child is awake and demonstrating eye opening and other purposeful movements; the practice at others is to extubate while the child is under a deep plane of inhalational anesthesia. Clinicians report only rare problems with either approach. Most clinicians agree that either approach is preferable to extubating the trachea during a very light plane of anesthesia, when laryngospasm is more likely and vomiting may occur while protective reflexes are impaired.
Immediately after extubation, oxygen should be administered, and the child should be observed for adequate ventilation, satisfactory oxygen saturation, color of the mucous membranes, and laryngospasm or vomiting. Transport of children should not be undertaken until the patency of the airway and the adequacy of oxygenation and ventilation have been confirmed in the form of stable and satisfactory oxygen saturation and adequate respiratory effort. Our criterion for transporting the child from the operating room to the PACU without oxygen is a stable oxygen saturation of 95% or greater while breathing room air. If the child cannot sustain this level of oxygen saturation, more time for recovery in the operating room is taken, or the child is transported with supplemental oxygen and a means for providing positive-pressure ventilation.
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 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
Minute ventilation is the product of tidal volume and respiratory rate. It decreases when tidal volume, respiratory rate, or both values decrease. Hypoventilation leads to hypercarbia and promotes alveolar collapse, known as atelectasis