The Postanesthesia Care Unit and Beyond

Transport to the Care Unit

The PACU should be located near the operating room to decrease the amount of time spent in transport of a sedated and/or critically ill patient. If transporting a sedated patient from a remote location, the patient's vital signs and a metric of respiration should be monitored along the route. Appropriate airway equipment and drugs should be immediately available. 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, IV and arterial lines, drains, and urinary catheters should be checked before transport. Children should be covered during transport to maintain normothermia and appear presentable (e.g., remove garments and sheets that contain blood and secretions).

Unless children are awake, with protective airway reflexes intact, or unless there is a specific contraindication, it is appropriate 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, possibly leading to airway obstruction or pulmonary aspiration. 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 serve as a crude metric of ventilation because desaturation will occur quickly if hypopnea develops. However, if oxygen is provided to the child, desaturation may not occur for a considerable time in the setting of apnea, and ventilation should be monitored by close observation, a precordial stethoscope, capnography, or ideally, by a combination of these. 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, IV drips, infusion pumps, and other equipment should be clearly labeled and simplified before transport. A tackle box containing airway equipment and emergency medications is useful, especially when children are transported to or from remote locations.

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, a child may become restless during transit. Although restless behavior has many causes, hypoxia should be ruled out first. The guard rails on the stretcher should always be raised when the child is in it and padding with pillows may prevent injury to the child. Most importantly, the anesthesiologist should remain at the head of the stretcher during transport maintaining vigilance of the child and the monitors throughout the transfer.

Arrival in the Care Unit

The transfer of care from the operating room personnel to the PACU or PICU is a crucial element of quality patient care that deserves considerable focus and the importance of this process cannot be overemphasized. Ideally, it is a stepwise process following an institutional protocol that begins in the operating room with communication to the receiving unit before the end of the procedure that provides pertinent patient information as well as required nonstandard equipment and medication to the receiving care team. On arrival in the PACU, a rapid assessment of the child should be undertaken to ensure that the child has a patent airway and that the vital signs are stable. Once the child has been properly assessed, an admission heart rate, oxygen saturation, respiratory rate, blood pressure, and temperature should be recorded. Supplemental oxygen is administered as indicated, recognizing the limitations of the monitors to detect hypoventilation 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). In the healthy child, if the child is awake enough to object to a mask with oxygen, the child does not require supplemental oxygen (although the combative, hypoxic child will require not only oxygen but establishment of a patent airway as well).

Numerous patient safety organizations and health care institutions have devoted considerable time and resources to improve patient transfer processes with the primary objective to improve safety, increase the quality of care, and decrease health care costs. Education of health care personnel about the importance of this endeavor is the first step to implementing effective transfers of care; several methods have been suggested. Standardized handoffs containing validated checklists and protocols are considered essential components of this process. Institutions with effective and organized handoff systems have reported a decrease in the number of medical errors and improved patient outcomes.

Surgeons, anesthesia providers, and intensive care physicians involved in the care of the child should be present and actively participate during the transfer of care from the operating room to the PACU or PICU. Specific circumstances such as language barriers, developmental delay, or family concerns should be conveyed to members of the team accepting care of the child. Since cultures vary within and among different institutions, we recommend developing a formalized transfer of care process that focuses of critical aspects of patient care, including pertinent patient information and history, surgical procedures, type of anesthesia administered, airway management, medications (especially antibiotics and analgesics), fluids administered, hemodynamics, estimated blood loss, unexpected events, anticipated patient progress, and information that needs to be relayed to parents or hospital staff in the event the patient is being admitted. Any unanticipated or serious events, such as unanticipated difficult airway, hemodynamic instability, or surgical complications, should be clearly communicated. If continuous infusions of local anesthetics are administered (e.g., epidural catheter infusion), the dose, concentration, rate, and maximum infusion rate should be conveyed. Tasks that need to be completed in the near future should be discussed with the team accepting the care of the patient. All stakeholders should have the opportunity to ask questions and confirm the transfer information at the conclusion of the handoff.

The anesthesia team must remain with the child until he or she has stable vital signs and the PACU or PICU 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 or PICU after the anesthesia team leaves must be clearly identified by name, and methods to contact them (e.g., pager number) must be given to surgeons, anesthesiologists, and regional block and pain services. It is important to understand that barriers may exist at several levels and preclude the effective transfer of care. Such circumstances frequently implicated include external distractions, noisy environments, shift changes, and differences in culture and priorities between individuals providing and accepting care of the child.

Ideally, the nurses taking care of the child postoperatively are already familiar with the child and family from the preoperative setting. The nurse/patient ratio should be 1 : 1 for sick children and 1 : 2 or 1 : 3 for routine cases. It has been reported that staffing ratios, nursing surveillance techniques, and vigilant monitoring of patients in the PACU by pediatric-trained nursing staff improve patient outcomes. Available staffing and resources in the PACU or PICU should be in place before transporting the child from the operating room.

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 (OSA). 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.

Pharmacodynamics of Emergence

Emergence from anesthesia is a complex process dependent on the dose and types of medications administered, the age, and the physiologic status of the patient. 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. However, the overall clinical implications of age-related differences in emergence are exceedingly difficult to detect. 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 anesthetics and the more time it takes to eliminate the anesthetics for recovery. 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. 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 IV agents can vary significantly from that of inhalational agents. Several studies have evaluated the quality and rapidity of emergence after IV 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. The recovery characteristics of propofol with remifentanil (total IV anesthesia [TIVA]; see Chapter 8 ) have been compared with those after desflurane inhalational anesthesia. Recovery is as rapid as that after desflurane with nitrous oxide, with a similar or reduced incidence of nausea and vomiting but with much less agitation.

Although rarely used for maintenance of anesthesia, midazolam is often used as an oral or IV premedication for anxiolysis and amnesia in the preinduction period in children. There is evidence that the addition of midazolam before an inhalational or propofol anesthetic may delay early emergence after brief anesthesia. However, this delay is attenuated as the duration of anesthesia increases and when only late emergence is considered. Midazolam premedication does not affect the incidence of postoperative delirium but has been reported to decrease postoperative nausea and vomiting (PONV). IV midazolam at the end of surgery does decrease the incidence of emergence delirium (see later text).

Emergence Agitation or Delirium

Emergence agitation refers to an umbrella of signs and symptoms that includes delirium ( Videos 47.1 and 47.2 ), postoperative pain, and behavior disorders. Emergence delirium was first described in a large cohort of postsurgical patients over 50 years ago. From a clinical perspective, it is often impossible to differentiate pure agitation from delirium, although the latter implies a disturbance in attention and represents an acute change from baseline. Despite numerous investigations, differentiating emergence delirium from postoperative pain has proved difficult, although it has been suggested that children who do not make any eye contact or who are unaware of their surroundings are more likely to be experiencing emergence delirium. Emergence delirium typically 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 (frequency of 30%–50%) than in adults, particularly in those 2 to 6 years of age. The mechanism of emergence delirium in children has not been completely elucidated, but differences in the frontal lobe electroencephalogram and in the locus coeruleus compared with children without delirium may highlight the source of the delirium. Evidence also points to differences in central nervous system (CNS) metabolites in the parietal cortex that may contribute to delirium; lactic acid concentrations and other metabolites after sevoflurane in children correlated with greater Pediatric Anesthesia Emergence Delirium (PAED) scale values than those after propofol.

Several scales have been developed to measure emergence delirium, although only one, the PAED scale, has been validated for this purpose in the postoperative period. Tables 47.4 and 47.5 present two scoring systems that have been used to evaluate emergence behaviors in children. In evaluating emergence delirium with the PAED scale after anesthesia, preliminary evidence suggested that values greater than 10 or possibly greater than 12 were consistent with emergence delirium. In the PICU, evidence suggests that a PAED score greater than 8 predicts emergence delirium. The literature regarding postoperative delirium in children is quite confusing in part, because many studies used nonvalidated, unproven scales in children whose pain was not controlled, leaving the cause of the behavior attributable to delirium, pain, or both.

Our understanding of emergence delirium continues to evolve. Delirium occurs after surgical procedures and after procedures that are free from pain, such as magnetic resonance imaging. Factors that have been associated with the development of emergence delirium include age 2 to 6 years, the use of less-soluble inhalational anesthetics (e.g., incidence after sevoflurane, desflurane and isoflurane ≫ TIVA > halothane) and the preoperative mental state. Although some claim that there is a greater incidence of emergence delirium after certain painful surgeries, in most of these instances this cannot be proven as pain was not controlled and a nonvalidated metric of delirium was used. A number of other plausible factors that do not predispose to delirium include a rapid emergence from anesthesia, a greater depth of anesthesia, and preoperative anxiety, although the last factor is contentious. Emergence delirium usually lasts less than 15 to 20 minutes, resolves spontaneously if the children are left undisturbed or they are held by their parents, and does not recur.

Several strategies have been used to prevent emergence delirium ( Table 47.6 ). Effective regional analgesia, dexmedetomidine, opioids, ketamine, melatonin, midazolam, magnesium, and propofol have been used with success. Fentanyl (2–2.5 µg/kg intranasally or 1–2 µ/kg IV) decreases the duration and intensity of emergence delirium, even in the absence of painful stimuli, most likely because of its sedating effect. Administration of propofol by continuous infusion or by bolus (1–3 mg/kg) at the end of surgery appears to be preventative, although these findings have not been consistent. A dose of propofol at induction of anesthesia does not prevent postoperative emergence delirium. Administration of TIVA has been reported to be superior to inhalational agents in the prevention of emergence delirium. Some clinicians cannot justify prophylactic treatment to prevent delirium when the local incidence is small.

When emergence delirium does occur, it is important to explain its self-limiting nature to the parents who quickly become frustrated trying to comfort their child. Whether to terminate the delirium pharmacologically or let it take a natural course needs to be discussed with the parents. Many parents prefer to avoid administering additional medications, knowing that the delirium will abate spontaneously after several minutes and that their child will recover to his or her normal disposition soon. Treatment of ongoing delirium has not been widely studied, but current strategies include propofol 1 to 3 mg/kg IV, fentanyl 1 to 2 µg/kg, or dexmedetomidine 0.3 µg/kg. Most use an initial small dose and titrate to effect.

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 delirious, to the site of surgery, or to a parent is a concern, as is pulling out a drain or dressing on a wound or self-extubation. 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 is greater among children who experience marked emergence delirium.

Criteria for Extubation

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 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, whereas the practice at others is to extubate while the child is deeply anesthetized. 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 (stage 2), when laryngospasm is more likely and vomiting may occur while protective reflexes are impaired.

Extubation in the Operating Room or Postanesthesia Care Unit

Immediately after extubation, oxygen should be administered, and the child should be observed closely to ensure that ventilation, oxygen saturation, and the color of the mucous membranes are adequate and whether airway obstruction, laryngospasm, or vomiting occur. Transport of children out of the anesthetizing location should not begin until the patency of the airway and the adequacy of oxygenation and ventilation have been confirmed.

For children whose tracheas are extubated in the PACU, respiratory insufficiency is the most worrisome and most frequent complication. Respiratory insufficiency represents approximately two-thirds of critical perioperative events when it occurs during emergence from anesthesia. Respiratory insufficiency may manifest in the form of difficulty breathing, or it may present 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. This is particularly true for children after tonsillectomy complicated by obesity and possible OSA and for those who have undergone diagnostic bronchoscopy.

Hypoxemia

Hypoxemia may result from hypoventilation, upper airway obstruction, bronchospasm, aspiration, pulmonary edema, pneumothorax, atelectasis, or rarely from postobstructive pulmonary edema, cardiac shunting, 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 five and exacerbate hemoglobin desaturation.

Postoperative hemoglobin desaturation is more common in children with or recovering from an active upper respiratory tract infection owing to increased airway reactivity, atelectasis, and increased secretions than in children without a history of upper respiratory tract infection. In neonates, hypoxia increases ventilation for approximately 1 minute but then depresses the respiratory drive (i.e., respiratory rate and tidal volume). The normal ventilatory response to hypoxia is delayed for several months in ex-premature nursery graduates with severe bronchopulmonary dysplasia, placing them at particular risk for desaturation in the perioperative period.

Hypoventilation

Severe hypoventilation causes respiratory acidosis, hypoxemia, carbon dioxide narcosis, and apnea. Hypoventilation may result from a decrease in ventilatory drive, muscle weakness, or mechanical effects. Inhalational anesthetics, opioids, benzodiazepines, and other sedating medications (except α ₂ -agonists) decrease the ventilatory drive in children in a dose-dependent manner. At particular risk for postoperative hypoventilation are children with underlying disturbances in respiration, such as infants with apnea of prematurity (formerly preterm infants of less than 60 weeks postconception age [PCA]); those with CNS injury such as head injury, strokes, and intracranial surgery; obese children; and those with OSA. These children may require prolonged observation in a setting with continuous monitoring capabilities.

Muscular weakness may contribute to respiratory insufficiency. Preexisting muscular disease (e.g., muscular dystrophy) and inadequate reversal of neuromuscular blockade, electrolyte abnormalities, neurologic disorders, drugs, infection, and endocrine disease may impair the respiratory effort sufficiently to cause hypoventilation and respiratory insufficiency. Inadequate analgesia can lead to splinting and hypoventilation, which may in turn increase ventilation-perfusion mismatch and decrease the oxygen saturation.