4 Preoperative Evaluation, Premedication, and Induction of Anesthesia
Preparation of Children for Anesthesia
Fasting
Infants and children are fasted before sedation and anesthesia to minimize the risk of pulmonary aspiration of gastric contents. In a fasted child, only the basal secretions of gastric juice should be present in the stomach. In 1948, Digby Leigh recommended a 1-hour preoperative fast after clear fluids. Subsequently, Mendelson reported a number of maternal deaths that were attributed to aspiration at induction of anesthesia.1 During the intervening 20 years, the fasting interval before elective surgery increased to 8 hours after all solids and fluids. In the late 1980s and early 1990s, an evidence-based approach to the effects of fasting intervals on gastric fluid pH and volume concluded that fasting more than 2 hours after clear fluids neither increased nor decreased the risk of pneumonitis should aspiration occur.2–10 In the past, the risk for pneumonitis was reported to be based on two parameters: gastric fluid volume greater than 0.4 mL/kg and pH less than 2.5; however, these data were never published in a peer-reviewed journal.1,11 In a monkey, 0.4 mL/kg of acid instilled endobronchially, equivalent to 0.8 mL/kg aspirated tracheally, resulted in pneumonitis.12 Using these corrected criteria for acute pneumonitis (gastric residual fluid volume greater than 0.8 mL/kg and pH less than 2.5), studies in children demonstrated no additional risk for pneumonitis when children were fasted for only 2 hours after clear fluids.2–9
The incidence of pulmonary aspiration in modern routine elective pediatric or adult cases without known risk factors is small.13–16 This small risk is the result of a number of factors including the preoperative fasting schedule. The half-life to empty clear fluids from the stomach is approximately 15 minutes (Fig. 4-1); as a result, 98% of clear fluids exit the stomach in children by 1 hour. Clear liquids include water, fruit juices without pulp, carbonated beverages, clear tea, and black coffee. Although fasting for 2 hours after clear fluids ensures nearly complete emptying of the residual volume, extending the fasting interval to 3 hours introduces flexibility in the operative schedule. The potential benefits of a 2-hour fasting interval after clear fluids include a reduced risk of hypoglycemia, which is a real possibility in children who are debilitated, have chronic disease, are poorly nourished, have metabolic dysfunction, or are preterm or formerly preterm infants.17–20 Additional benefits include decreased thirst, decreased hunger (and thus reduced temptation that the fasting child will “steal” another child’s food), decreased risk for hypotension during induction, and improved child cooperation.2,11,21
Breast milk, which can cause significant pulmonary injury if aspirated,22 has a very high and variable fat content (determined by maternal diet), which will delay gastric emptying.21 Breast milk should not be considered a clear liquid.23 Two studies estimated the gastric emptying times after clear fluids, breast milk, or formula in full-term and preterm neonates.24,25 The emptying times for breast milk in both age groups were substantively greater than for clear fluids, and the gastric emptying times for formula were even greater than those for breast milk. With half-life emptying times for breast milk of 50 minutes and for formula of 75 minutes, fasting intervals of at least 3.3 hours for breast milk and 5 hours for formula are required. More importantly, perhaps, was the large (15%) variability in gastric emptying times for breast milk and formula in full-term infants (E-Fig. 4-1). Based in part on these data, the Task Force on Fasting of the American Society of Anesthesiologists (ASA) issued the following guidelines: for breast milk, 4 hours; and for formula, 6 hours (Table 4-1).10
TABLE 4-1 Preoperative Fasting Recommendations in Infants and Children
| Clear liquids* | 2 hours |
| Breast milk | 4 hours |
| Infant formula | 6 hours† |
| Solids (fatty or fried foods) | 8 hours |
*Include only fluids without pulp, clear tea, or coffee without milk products.
†Some centers allow plain toast (no dairy products) up to 6 hours prior to induction.
From Warner MA, Caplan RA, Epstein B. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures. A report by the American Society of Anesthesiologists Task Force on Preoperative Fasting. Anesthesiology 1999;90:896-905.
Children who have been chewing gum must dispose of the gum by expectorating it, not swallowing it. Chewing gum increases both gastric fluid volume and gastric pH in children, leaving no clear evidence that it affects the risk of pneumonitis should aspiration occur.26 Consequently, we recommend that if the gum is discarded, then elective anesthesia can proceed without additional delay. If, however, the child swallows the gum, then surgery should be cancelled, because aspirated gum at body temperature may be very difficult to extract from a bronchus or trachea.
When the anesthesiologist suspects that the child has a full stomach, induction of anesthesia should be adjusted appropriately. The incidence of pulmonary aspiration of gastric contents during elective surgery in children ranges from 1 : 1163 to 1 : 10,000, depending on the study.13–1527 In contrast, the frequency of pulmonary aspiration in children undergoing emergency procedures is several times greater, 1 : 373 to 1 : 4544.27 Risk factors for perianesthetic aspiration included neurologic or esophagogastric abnormality, emergency surgery (especially at night), ASA physical status 3 to 5, intestinal obstruction, increased intracranial pressure, increased abdominal pressure, obesity, and the skill and experience of the anesthesiologist.14
The majority of aspirations in children occur during induction of anesthesia, with only 13% occurring during emergence and extubation. In contrast, 30% of the aspirations in adults occur during emergence. Bowel obstruction or ileus was present in the majority of infants and children who aspirated during the perioperative period in one study, with the risk increasing in children younger than 3 years of age.27 A combination of factors predispose the infant and young child to regurgitation and aspiration, including decreased competence of the lower esophageal sphincter, excessive air swallowing while crying during the preinduction period, strenuous diaphragmatic breathing, and a shorter esophagus. In one study, almost all cases of pulmonary aspiration occurred either when the child gagged or coughed during airway manipulation or during induction of anesthesia when neuromuscular blocking drugs were not provided or before the child was completely paralyzed.27
When children do aspirate, the morbidity and mortality are exceedingly small for elective surgical procedures and generally reflect their ASA physical status. In general, most ASA 1 or 2 patients who aspirate clear gastric contents have minimal to no sequelae.13,27 If clinical signs of sequelae from an aspiration in a child are going to occur, they will be apparent within 2 hours after the regurgitation.27 The mortality rate from aspiration in children is exceedingly low, between zero and 1 : 50,000.13,14,27
Piercings
Body piercing is common practice in adolescents and young adults. Single or multiple piercings may appear anywhere on the body. To minimize the liability and risk of complications from metal piercings, they must be removed before surgery. Complications that may occur if they are left in situ during anesthesia are listed in E-Table 4-1.28–30
E-TABLE 4-1 Complications from Metal Piercings
Modified from Rosenberg AD, Young M, Bernstein RL, Albert DB. Tongue rings: just say no. Anesthesiology 1998;89:1279-80; Wise H. Hypoxia caused by body piercing. Anaesthesia 1999;54:1129.
Primary and Secondary Smoking
Primary Smoking
Unfortunately, cigarette smoking is not only limited to adults. Each day, about 6000 American adolescents smoke their first cigarette. Of these, 50% will become regular smokers. Even though two thirds of these adolescents will regret taking up the habit and will want to quit, three quarters of them will not succeed because they are addicted to the nicotine. Sadly, about one third of those who cannot quit will die prematurely due to smoking.31 Even though the rate of new smokers in North America has waned in the past 2 decades, this has been offset by the increasing rate of new smokers in other continents. Media, peer influence, and secondhand smoke exposure play a significant role in influencing initiation of smokers in this age group.32
Smoking is known to increase blood carboxyhemoglobin concentrations, decrease ciliary function, decrease functional vital capacity (FVC) and the forced expiratory flow in midphase (FEF25%-75%), and increase sputum production. There is extensive evidence that smokers undergoing surgery are more likely to develop wound infections and postoperative respiratory complications.33 Although stopping smoking for 2 days decreases carboxyhemoglobin levels and shifts the oxyhemoglobin dissociation curve to the right, stopping for at least 6 to 8 weeks is necessary to reduce the rate of postoperative pulmonary complications.34,35
We seldom interview our patients 8 weeks before surgery, but because the perioperative period is the ideal time to abandon the smoking habit permanently, anesthesiologists can perhaps play a more active role in facilitating this process. Physician communication with adolescents regarding smoking cessation has been shown to positively impact their attitudes, knowledge, intentions to smoke, and quitting behaviors.36 In summary, during the preoperative visit with adolescents, anesthesiologists should inquire about cigarette smoking and emphasize the need to stop the habit by offering measures to ameliorate the withdrawal (e.g., nictoine patch).
Secondary Smoking
The World Health Organization has estimated that approximately 700 million children, or almost half of the children in the world, are exposed to environmental tobacco smoke (ETS).37 Children exposed to ETS are more likely to have asthma, otitis media,38 atopic eczema, hay fever,39 and dental caries.40 There is also an increased rate of lower respiratory tract illness in infants with ETS exposure.41,42
Several authors have demonstrated that ETS results in increased perioperative airway complications in children. In one study43 of children receiving general anesthesia, urinary cotinine, the major metabolite of nicotine, was used as a surrogate of ETS. A strong association was found between passive inhalation of tobacco smoke and airway complications on induction and emergence from anesthesia. Other investigators confirmed that ETS exposure was associated with an increased frequency of respiratory complications during emergence and recovery from anesthesia.44
Psychological Preparation of Children for Surgery
Although the preoperative evaluation and preparation of children are similar to those of adults from a physiologic standpoint, the psychological preparation of infants and children is very different (see also Chapter 3). Many hospitals have an open house or a brochure to describe the preoperative programs available to parents before the day of admission.45 However, printed material should not replace verbal communication with nursing and medical staff.46 Anesthesiologists are encouraged to participate in the design of these programs so that they accurately reflect the anesthetic practice of the institution. The preoperative anesthetic experience begins at the time parents are first informed that the child is to have surgery or a procedure that requires general anesthesia. Parental satisfaction correlates with the comfort of the environment and the trust established between the anesthesiologist, the child, and the parents.47 If parental presence during induction is deemed to be in the child’s best interest, a parental educational program that describes what the parent can expect to happen if he or she accompanies the child to the operating room can significantly decrease parents’ anxiety and increase their satisfaction.48 The greater the understanding and amount of information the parents have, the less anxious they will be, and this attitude, in turn, will be reflected in the child.49,50
It has been shown that parents desire comprehensive perioperative information, and that discussion of highly detailed anesthetic risk information does not increase parent’s anxiety level.51 Inadequate preparation of children and their families may lead to a traumatic anesthetic induction and difficulty for both the child and the anesthesiologist, with the possibility of postoperative psychological disturbances.52 Numerous preoperative educational programs for children and adults have evolved to alleviate some of these fears and anxiety. They include preoperative tours of the operating rooms, educational videos, play therapy, magical distractions, puppet shows, anesthesia consultations, and child life preparation.53 The timing of the preoperative preparation has been found to be an important determinant of whether the intervention will be effective. For example, children older than 6 years of age who participated in a preparation program more than 5 to 7 days before surgery were least anxious during separation from their parents, those who participated in no preoperative preparation were moderately anxious, and those who received the information 1 day before surgery were the most anxious. The predictors of anxiety correlated also with the child’s baseline temperament and history of previous hospitalizations.54 Children of different ages vary in their response to the anesthetic experience (see also Chapter 3).55 Even more important may be the child’s trait anxiety when confronted with a stressful medical procedure.56
Child Development and Behavior
Understanding age-appropriate behavior in response to external situations is essential (E-Table 4-2). Infants younger than 10 months of age tolerate short periods of separation from their parents. Many do not object to an inhalation induction and frequently respond to the smell of the inhalation agents by sucking or licking the mask. These infants usually do not need a sedative premedication.
| Age | Specific Type of Perioperative Anxiety |
|---|---|
| 0-6 months |
Modified with permission from Cruickshank BM, Cooper LJ. Common behavioral problems. In: Greydanus DE, Wolraich ML, editors: Behavioral pediatrics. New York: Springer; 1992.
Children between 11 months and 6 years of age frequently cling to their parents. In an unfamiliar environment such as a hospital, preschool children tend to become very anxious, especially if the situation appears threatening. Their anxiety may be exacerbated if they sense that their parents are anxious. Efforts to educate the parents to allay their anxiety can also reduce the child’s anxiety.45,57,58 A heightened anxiety response may lead to immediate postoperative maladaptive behavior, such as nightmares, eating disturbances, and new-onset enuresis. Compared with other patients, children 2 to 6 years of age are more likely to exhibit problematic behavior when separated from their parents (see also Chapter 3).55 Children who display one or more of the predictive risk factors would probably benefit from a sedative premedication.59–62 They are generally more content if their parents accompany them during induction or if they are sedated in the presence of their parents in a nonthreatening environment before entering the operating room (see later discussion).
Children ages 4 to 10 years may exhibit psychological factors that are predictive of postoperative behavior (e.g., abnormal sleep patterns, parental anxiety, aggressive behavior).63,64 In addition, children who have pain on the day of the operation have behavioral problems that continue well after the pain has been relieved.65 Therefore, preventing postoperative pain decreases and limits the duration of postoperative behavioral problems.
The importance of proper psychological preparation for surgery should not be underestimated. Often, little has been explained to both patient and parents before the day of surgery. Anesthesiologists have a key role in defusing fear of the unknown if they understand a child’s age-related perception of anesthesia and surgery (see Chapter 3). They can convey their understanding by presenting a calm and friendly face (smiling, looking at the child and making eye contact), offering a warm introduction, touching the patient in a reassuring manner (holding a child’s or parent’s hand), and being completely honest. Children respond positively to an honest description of exactly what they can anticipate. This includes informing them of the slight discomfort of starting an intravenous line or giving an intramuscular premedication, the possible bitter taste of an oral premedication, or breathing our magic laughing gas through the flavored mask.
The postoperative process, from the operating room to the recovery room, and the onset of postoperative pain should be described. Encourage the child and family to ask questions. Strategies to maintain analgesia should be discussed, including the use of long-acting local anesthetics; nerve blocks; neuraxial blocks; patient-controlled, nurse-controlled, or parent-controlled analgesia or epidural analgesia; or intermittent opioids (see also Chapters 41, 42, and 43).
It is important to observe the family dynamics to better understand the child and determine who is in control, the parent or the child. Families many times are in a state of stress, particularly if the child has a chronic illness; these parents are often angry, guilt ridden, or simply exhausted. Ultimately, the manner in which a family copes with an illness largely determines how the child will cope.66 The well-organized, open, and communicative family tends to be supportive and resourceful, whereas the disorganized, noncommunicative, and dysfunctional family tends to be angry and frustrated. Dealing with a family and child from the latter category can be challenging. There is the occasional parent who is overbearing and demands total control of the situation. It is important to be empathetic and understanding but to set limits and clearly define the parent’s role. He or she must be told that the anesthesiologist determines when the parent must leave the operating room; this is particularly true if an unexpected development occurs during the induction.
Parental Presence during Induction
One controversial area in pediatric anesthesia is parental presence during induction. Some anesthesiologists encourage parents to be present at induction, whereas others are uncomfortable with the process and do not allow parents to be present. Inviting a parent to accompany the child to the operating room has been interpreted by some courts as an implicit contract on the part of the caregiver who invited the parent to participate in the child’s care; in one case, the institution was found to have assumed responsibility for a mother who suffered an injury when she fainted.67 Each child and family must be evaluated individually; what is good for one child and family may not be good for the next.68–71 (See Chapter 3 for a full discussion of this and other anxiolytic strategies in children.)
Parents must be informed about what to anticipate in terms of the operating room itself (e.g., equipment, surgical devices), in terms of what they may observe during induction (e.g., eyes rolling back, laryngeal noises, anesthetic monitor alarms, excitation), and when they will be asked to leave. They must also be instructed regarding their ability to assist during the induction process, such as by comforting the child, encouraging the child to trust the anesthesiologist, distracting the child, and consoling the child (Video 4-1)
. Personnel should be immediately available to escort parents back to the waiting area at the appropriate time. Someone should also be available to care for a parent who wishes to leave the induction area or who becomes lightheaded or faints. An anesthesiologist’s anxiety about parents’ presence during induction decreases significantly with experience.72
Explaining what parents might see or hear is essential. We generally tell parents the following:
History of Present Illness
A review of all organ systems (Table 4-2) with special emphasis on the organ system involved in the surgery
Previous surgical and hospital experiences, including those related to the current problem
| System | Factors to Assess | Possible Anesthetic Implications |
|---|---|---|
| Respiratory |
In the case of a neonate, problems that may have been present during gestation and birth may still be relevant in the neonatal period and beyond (E-Table 4-3). The maternal medical and pharmacologic history (both therapeutic and drug abuse) may also provide valuable information for the management of a neonate requiring surgery.
E-TABLE 4-3 Maternal History with Commonly Associated Neonatal Problems
| Maternal History | Commonly Expected Problems with Neonate |
|---|---|
| Rh-ABO incompatibility | |
| Toxemia |
• SGA and its associated problems,* muscle relaxant interaction with magnesium therapy |
| Hypertension | |
| Drug addiction | |
| Infection | |
| Hemorrhage | |
| Diabetes | |
| Polyhydramnios | |
| Oligohydramnios | |
| Cephalopelvic disproportion | |
| Alcoholism |
SGA, Small for gestational age; LGA, large for gestational age.
Past/Other Medical History
Herbal Remedies
Increasing numbers of children are ingesting herbal medicine products. During the preoperative interview, anesthesiologists should include specific inquiries regarding the use of these medications because of their potential adverse effects and drug interactions. Hospital surveys suggest that the use of herbal remedies ranges from 17% to 32%73–75 of presurgical patients, and 70% of these patients do not inform their anesthesiologist of such use.
In Hong Kong, 80% of patients undergoing major elective surgery use prepacked over-the-counter traditional Chinese herbal medicines, and 8% use medicines prescribed by traditional Chinese medicine practitioners.76 The prescription users of traditional Chinese medicines experienced a greater incidence of adverse perioperative events. In particular, this group was twice as likely to have hypokalemia or impaired hemostasis (i.e., prolonged international normalized prothrombin ratio [INR] and activated partial thromboplastin time [aPTT]) than nonusers, although there was no significant difference in the incidence of perioperative events between self-prescribed users and nonusers. To further complicate this subject, there is an important difference between Chinese and Western herbs. Traditional Chinese herbal medicines consist of multiple herbs that are combined for their effects, whereas Western herbs are usually ingested as a single substance.77
Herbal medicines are associated with cardiovascular instability, coagulation disturbances, prolongation of anesthesia, and immunosuppression.78 The most commonly used herbal medications reported are garlic, ginseng, Ginkgo biloba, St. John’s wort, and echinacea.79 The three “g” herbals, together with feverfew (Tanacetum parthenium), potentially increase the risk of bleeding during surgery. The amount of active ingredient in each preparation may vary, the dose taken by a child may also vary, and detection of a change in platelet function and other subtle coagulation disturbances may be difficult. St. John’s wort is the herb that most commonly interacts with anesthetics and other medications, usually via a change in drug metabolism, because it is a potent induction of the cytochrome P-450 enzymes (e.g., CYP3A4) and P-glycoprotein. A potentially fatal interaction between cyclosporine and St. John’s wort has been well documented.80–83 Heart, kidney, or liver transplant recipients who were stabilized on a dose of cyclosporine experienced decreased plasma concentrations of cyclosporine and, in some cases, acute rejection episodes after taking St. John’s wort. A summary of the most commonly used herbal remedies and their potential perioperative complications is shown in E-Table 4-4.
E-TABLE 4-4 Pharmacologic Effects and Potential Perioperative Complications of Eight Commonly Used Herbal Remedies
To avoid potential perioperative complications, the ASA has encouraged the discontinuation of all herbal medicines 2 weeks before surgery,84 although this recommendation is not evidence based. Indeed, some herbs such as valerian, a treatment for insomnia (Valeriana officinalis), should not be discontinued abruptly but tapered; otherwise, abrupt discontinuation may result in a paradoxical and severe reaction.85 Each herb should be carefully evaluated using standard resource texts, and a decision should be made regarding the timing of or need for discontinuation as determined on a case-by-case basis.86
