Preoperative Evaluation

The objective of the preoperative evaluation of the pediatric surgical patient is to assess current clinical status and alleviate fear and anxiety of the child and family. The process of anesthetizing an infant or child and the associated risks must be demystified during the preoperative visit since parents often have more anxiety about their child undergoing anesthesia than they do for themselves. The preoperative visit is an opportunity for the anesthesiologist to evaluate the child’s psychological status and family interactions. It has been demonstrated that parental anxiety surrounding anesthesia is highest when surgery is scheduled for infants less than one year of age and is the child’s first surgical experience [1].

Psychosocial Preparations of the Family

Anesthesiologists and other healthcare professionals who treat children face the unique challenge of caring for two patients at once. As a result of the child’s dependence, the child and parent become the patient–parent dyad. The psychological differences between children and adults are well known, and in recent years it has also been well documented that differences are seen in the emotional and cognitive development of the child as compared to that of an adult. Since reasoning skills have not yet matured in children, the understanding of and response to illness is affected. Communication skills are not highly developed either, therefore the medical practitioner is required to anticipate the child’s needs and concerns and be able to interpret nonverbal expressions and actions [2].

The anesthesiologist must offer advice, support, and reassurance on two levels and must not only be aware and sensitive to the child’s needs, but must also be able to support the parent’s need for information that will enable them to remain a strong advocate for their child throughout the medical system. For most parents, the prospect of their child’s impending hospitalization is more frightening than almost anything else. Perioperative anxiety is greatest for parents of infants between the ages of 0–6 months. Factors that influence parental anxiety include the age of the child, previous surgery in the patient or a sibling, parental gender, highest level of education obtained by the parent and preoperative discussion. Interestingly, these factors were more significant for mothers when parents were assessed by gender [3].

As infants begin to differentiate their primary caregivers from others, they develop a previously absent wariness of strangers. This change begins to occur at approximately eight months of age, whereas infants younger than this will usually separate easily from their primary caregiver. A discussion of the infant’s behavior and the presence of stranger anxiety should be included in the preoperative interview so that the anesthesiologist may obtain a sense of how easily the infant will separate from the parent and how anxious the parent is. Prior to the onset of stranger anxiety in an infant, parental presence is not required or advisable during the induction of anesthesia; therefore parents of young infants should not be invited into the operating room. An explanation of what will occur after the infant is taken from the parents is usually sufficient. If stranger anxiety is already present in an older infant, then a parent may be invited into the operating room until the child is unaware of his or her presence if the anesthesiologist feels it would be safe. An explanation of the induction process should occur, including what the parent will observe, the operating room configuration, and the personnel that will be present. They should also be instructed on when they will be asked to leave and how they will be escorted from the operating room to avoid any distress regarding leaving their child with the operating room team.

Premedication

Infants under one year of age have varying degrees of separation anxiety. Stranger anxiety develops slowly; it does not just appear suddenly. As cognitive skills in a child develop and improve, typically around 12 months of age, their stranger anxiety can become more intense. The nature of anxiety in children is dependent on many factors, including age, temperament, past experience, and family background. Parental presence, distraction, and premedication have all been used successfully, but no single strategy is effective for all children [4]. When the need for premedication arises, the standard agent of choice has been midazolam, which has been shown to be effective in infants not only for premedication but to decrease anxiety during interventional procedures performed without general anesthesia [5]. The recent introduction of dexmedetomidine as an intranasal as well as oral agent for premedication has provided an alternative choice [6]. The most recent meta-analysis demonstrated that dexmedetomidine premedication is superior to midazolam with respect to satisfactory separation from parents and mask acceptance, and has an additional clinical advantage of reducing the requirement for rescue analgesia during the postoperative period. There are, however, increased risks of decreased heart rate and blood pressure compared to midazolam when dexmedetomidine is used for premedication [7]. Ketamine has been a longstanding choice for premedication in older infants, but it should be noted that children premedicated with ketamine require close observation in a quiet environment where resuscitation equipment is readily available. Studies have shown midazolam to be a more effective and safer premedication than ketamine [8].

Informed Consent About Short- and Long-Term Morbidity

The process of informed consent for anesthesia is carried out during the preoperative discussion. An assessment of risk that is specific to each patient with regard to the planned procedure and each patient’s current state of health as compared to the usual state of health should be discussed. The overall incidence of cardiac arrest during anesthesia in children under 18 years of age has been reported to be 2.9–4.95/10 000 and 18.28/10 000 below one year of age, making cardiac arrest in infants 3–6 times more common than in older children. The greatest risk occurs in patients with an American Society of Anesthesiologists risk stratification of III and IV, as well as those undergoing emergency surgery [9].

The most common surgical procedures associated with highest risk of cardiac arrest in children include airway procedures, followed by abdominal, thoracic, and cardiovascular procedures. The vast majority of neonatal cardiac arrest occurs in patients who have congenital heart disease [10]. The most frequent noncardiac causes of anesthesia-related cardiac arrests are medication and airway related [11,12]. Any medical comorbidities that exist which increase anesthetic risk should be described in detail and the measures that the anesthesia team will take to safely care for patients with regard to these risks should be explained. An explanation of the monitoring equipment in place in each operating room and the specific physiologic parameter that it measures is useful information to parents. In addition, a description of the number of personnel in the operating room as well as those available in case of an emergency is a reassuring piece of information for parents.

Ambulatory Surgery

The greatest risk for infants undergoing ambulatory surgery is post-anesthetic apnea. There is controversy regarding the lowest age at which both full-term babies and former premature babies may be discharged home after surgery. Former preterm infants born prior to 37 weeks’ gestational age as well as full-term infants less than 28 days of life are at increased risk for respiratory depression and apnea after general anesthesia. It is therefore recommended that the period of postoperative respiratory monitoring be extended for these patients. In former preterm infants without additional comorbidities, six hours of post-anesthesia respiratory monitoring is satisfactory since the first apneic episode usually occurs within the first four hours postoperatively [13]. In the presence of additional risk factors, including chronic lung disease, anemia (as defined by hematocrit <30 percent), recurrent apnea at home, or neurologic disease, the period of observation should be extended to 12 hours [14,15]. Whenever possible, elective surgery should be postponed until a postconceptual age of 60 weeks has been achieved.

Within the pediatric population, perioperative cardiac arrest under general anesthesia is more frequent in infants than in older children and beyond the first year of life age does not noticeably affect incidence of cardiac arrest [16,17]. Most cardiac arrests in the operating room are not a direct result of the anesthetic, and intraoperative cardiac arrests occur more frequently in children with congenital cardiac disease. Although there are no data to support discouraging elective ambulatory anesthesia in children less than one year of age, many institutions do not discharge children to home after general anesthesia until they are older than six months of age.

Smoking in the House

Exposure to environmental tobacco smoke is associated with detrimental effects on pulmonary function in infants and children. There is a strong association between passive inhalation of tobacco smoke and airway complications in children receiving general anesthesia. Interestingly, studies indicate that this relationship is greatest for girls and for those whose mothers have a lower level of education. Significant physiologic effects may be documented as a result of passive tobacco smoke exposure. Cotinine is an alkaloid found in tobacco and is also a measurable metabolite of nicotine. The level of cotinine in the blood is proportionate to the amount of exposure to tobacco smoke, thus it is a valuable indicator of tobacco smoke exposure, including secondary (passive) smoke. In recent reports, perioperative airway complications occurred in 42 percent of patients with urinary concentrations of cotinine >40 ng ml^–1, in 33 percent of patients with concentrations of cotinine between 10.0 and 39.9 ng ml^–1, and in 24 percent of patients with concentrations of cotinine <10 ng ml^–1 (the three groups) [18]. The presence of a smoking caregiver is a significant independent risk factor for upper respiratory infection during the first three years of life. An increased risk of lower respiratory infections of two-fold or more occurs in infants and children from four months of age to three years. The risk of wheezing as a result of lower respiratory infections in the presence of a smoking caregiver was more than three-fold in this patient age group [19]. The exposure of infants to passive tobacco smoke should be investigated and, if present, minimized to decrease the risk of adverse respiratory events during the perioperative period.

Fasting Requirements

It is no longer advisable or safe to restrict children to “NPO after midnight” [20]. This severe restriction routinely increases each child’s chance of undergoing the induction of anesthesia when dehydrated, hypoglycemic, and irritable, all of which lead to increased risk under anesthesia. The risk of pulmonary aspiration of gastric contents in healthy children undergoing elective surgery is only 0.04 percent [21]. The American Society of Anesthesiologists (ASA) has proposed practice guidelines that may be followed when determining the NPO restrictions in children [22]. The ASA and others recommend fasting from clear fluids for two hours prior to anesthesia. Clear liquids consist of water, non-particulate juices (apple, white grape, etc.), Pedialyte®, and Popsicles®. Fasting from breast milk for four hours and formula for six hours is recommended. The composition of human milk varies among mothers and is dependent on the mother’s diet, but in general is composed of 50 percent lipids, 40 percent carbohydrate in the form of lactose, and 10 percent protein divided into casein and whey [23]. Breast milk may cause significant pulmonary injury if aspirated due to a high fat content as determined by the maternal diet. The suggested fasting period for solid food is six hours for regular meals and eight hours for fat-containing meals; however, a large survey of pediatric institutions recommends fasting from all solids for at least eight hours in all children [24]. It is best to check with each surgical facility for specific practice guidelines.

Immunization

There is no direct evidence of any major interaction between immunization and commonly used anesthetic agents and techniques in children, but it is possible that immunosuppression caused by anesthesia and surgery may lead to decreased vaccine effectiveness. In addition, diagnostic difficulty may arise if a recently immunized child suffers from postoperative temperature elevation or malaise [25]. From a risk management perspective, a review of the available evidence suggests that it would be prudent to adopt a cautious approach where the timing of elective surgery is discretionary. It is therefore recommended that elective surgery and anesthesia should be postponed for one week after inactive vaccination and three weeks after live attenuated vaccination in children.

Anesthesia and surgery exert immunomodulatory effects and some authors argue that they may exert additive or synergistic influences on vaccine efficacy and safety. Alternatively, inflammatory responses and fever elicited by vaccines may interfere with the postoperative course. There is a lack of consensus approach among anesthesiologists regarding the theoretical risk of anesthesia and vaccination. The immunomodulatory influence of anesthesia during elective surgery is both minor and transient (around 48 hours) and the current evidence does not provide any contraindication to the immunization of healthy children scheduled for elective surgery. Respecting a minimal delay of two days for inactivated vaccines or 14–21 days for live attenuated viral vaccines between immunization and anesthesia may be useful to avoid the risk of misinterpretation of vaccine-driven adverse events as postoperative complications [26].

Prematurity

Preterm births as defined by completion of 37 weeks’ gestation or 260 postmenstrual days are estimated to occur in 12.7 percent of live births [27,28]. This group of infants has a unique subset of perioperative comorbidities that the anesthesiologist should be alert to and investigate preoperatively to avoid any unexpected untoward events related to the anesthesia or perioperative episode of care.

Thorough preoperative assessment of the former preterm infant is essential and allows time for optimization of medical conditions. These infants present for a variety of surgical procedures and some, like hernia repair, may seem minor, but the anesthetic management remains challenging. Two major areas of concern for professionals and family alike are the extent of chronic lung disease and the possibility for postoperative apnea. Concise delineation of other coexisting conditions is also extremely important to anesthesiologists.

Infants born prematurely may range from having no residual lung disease to significant bronchopulmonary dysplasia (BPD). The latter condition is extremely variable in its manifestations from mild radiographic changes in an asymptomatic patient to pulmonary fibrosis, emphysema, reactive airway disease, chronic hypoxemia and hypercarbia, tracheomalacia or bronchomalacia, and increased pulmonary vascular resistance with cor pulmonale. If pulmonary hypertension and cor pulmonale are suspected, a pre-anesthetic echocardiogram is useful not only to confirm the diagnosis, but also to guide optimization of medical therapy. Diuretics, bronchodilators, and corticosteroids are medications that many of these patients require to optimize the child’s respiratory function, and should be continued up to and including the day of surgery. Measurement of serum electrolytes to evaluate the degree of hypokalemia and compensatory metabolic alkalosis may be valuable, especially if therapy has recently been altered. Consideration of pharmacological “stress” doses of steroids should be considered in infants receiving steroid treatment.

Postoperative apnea has been reported following anesthesia in former preterm and term infants alike. The incidence of post-anesthetic apnea is inversely related to the postconceptual age and gestational age. Infants younger than 56 weeks postconceptual are at greatest risk since the risk of post-anesthetic apnea does not fall to less than 1 percent until 55 weeks postconceptual age. This risk is present in full-term infants under 28 days of life. The concurrent presence of anemia is a confounding factor that further increases the risk of post-anesthetic apnea. Hematocrit should be targeted at a minimum of 30 percent in this patient population [29–31]. There is no consensus about the patient profile of at-risk infants. Reports are not consistent in identifying the postconceptional age or gestational age of at-risk patients, the methods used to detect apnea or periodic breathing, the surgical procedure, other confounding medical conditions, or even the definition of apnea [14].

A combined analysis of eight prospective studies investigated postoperative apnea in former preterm infants following inguinal herniorrhaphy. A uniform definition of apnea was cessation of breathing or no detection of air flow for ≥15 seconds or ≤15 seconds with bradycardia defined as heart rate <80 bpm. Examination of the data revealed that hematocrit <30 percent, apnea at home, postconceptional age, and gestational age are all important risk factors for postoperative apnea [32]. This supports claims that the risk of postoperative apnea is inversely related to postconceptional age and that infants as old as 60 weeks postconceptional age may be susceptible. Also, some authors suggest that infants with a prior history of apnea and bradycardia, respiratory distress, intubation, and mechanical ventilation may be at further increased risk [33–35]. Any child considered to be at risk for postoperative apnea should have arrangements made for overnight observation and monitoring. The former preterm infant should also have a recent hematocrit available since a value of <30 percent is associated with an increased incidence of post-anesthesia apnea irrespective of postconceptional age [36,37].

Intraventricular hemorrhage is a frequent finding in premature infants and is categorized as Grade 1–4 depending on the extent of hemorrhage beyond the germinal matrix, into the ventricular system, and finally penetration into the brain parenchyma. Grade 1 hemorrhage will usually not result in significant concern for the anesthesiologist, however more extensive blood pressure control is warranted for higher grade hemorrhage.

Retinopathy of prematurity is inversely related to gestational age. It occurs in up to 50 percent of premature infants [38,39]. The presence of retinopathy of prematurity should be noted in the preoperative review since the goal of the anesthetic plan should be to maintain oxygen saturation between 90 and 95 percent with the minimal concentration inspired oxygen [40].

The incidence of hypoglycemia, defined as less than 45 mg dl^–1, is three-fold higher in preterm infants as a result of decreased glycogen stores and feeding challenges. It is essential that this be identified so that a perioperative plan for glucose supplementation be made. Sepsis as a result of perinatal or postnatal acquired organisms is not an uncommon finding in the premature infant. A treatment plan for the infection as well as for hemodynamic support if the surgical procedure cannot be postponed should be identified. Because of their relatively smaller size, preterm infants are susceptible to periods of hypothermia and cold stress. Physiologic immaturity of thermoregulation, the lack of brown adipose tissue, and the lack of non-shivering thermogenesis predispose to the inability to generate heat in the same way that full-term and older infants do. A perioperative plan for temperature regulation and heat conservation is essential during the preoperative period.

Review of Systems

Physical Examination

A full physical examination of the neonate and infant is an essential component of the preoperative review. As assessment of gestation age as well as chronologic age should be made. The examination should begin with an observation of the infant in an undisturbed state, since a great deal may be learned about relevant physical findings without touching the child. The entire skin surface should be inspected for temperature, moisture, elasticity, and fragility. The color of the skin and the presence of pallor, cyanosis, rash, jaundice, unusual markings, birthmarks, and scars from previous operations should be noted. When examining a newborn, the head should be examined by inspection and palpation to determine if there is any bruising as a result of delivery, as well as the fullness of the fontanels to determine alterations in intracranial pressure. Abnormal facies might be an indication of a syndrome or constellation of congenital abnormalities. One congenital anomaly is often associated with others.

Inspection of the oral cavity may reveal normal variants such as small cysts, Epstein’s pearls, Bohn’s nodules, and dental lamina cysts. These are of no consequence and should not cause difficulty with laryngoscopy or endotracheal intubation. A gloved finger may be inserted into the oral cavity to determine the shape and integrity as well as to identify any abnormalities such as cleft palate. The neck should be observed for range of motion to detect spine abnormalities such as Klippel–Feil syndrome, congenital torticollis, and any anterior midline abnormalities such as branchial cleft or thyroglossal duct cyst. Short or webbed neck may be an indication of chromosomal abnormalities such as Down or Turner syndrome.

The shape of the chest and mechanics of respiration should be observed even before the lungs are auscultated. A normal infant is observed to be centrally acyanotic, resting comfortably, breathing easily with clear breath sounds when the lungs are auscultated. The color, viscosity, and quantity of nasal discharge should be documented. Respiratory rate may be irregular and pauses up to 20 seconds are normal in the infant. Common causes of mild respiratory distress in the newborn include transient tachypnea of the newborn due to retained fetal lung fluid, spontaneous pneumothorax, neonatal sepsis, pneumonia, meconium aspiration, or congenital heart disease. The respiratory system should be evaluated by noting the rate and quality of respirations, the presence of noisy breathing, coughing, purulent nasal discharge, stridor, and wheezing. Retractions, nasal flaring, grunting, and paradoxical respiration may be signs of increased work of breathing and respiratory distress in the infant. Noisy or labored breathing may indicate nasal or upper respiratory obstruction. If the child is coughing, the origin of the cough (upper versus lower airway) and the quality (dry or wet) can be evaluated even before auscultation of the lungs. Signs of an acute upper respiratory infection should be documented if present. The ease of mouth opening should be determined and the airway should be evaluated for ease of intubation. If the child will not open his or her mouth, a manual estimation of the thyrohyoid distance should be made. Children with micrognathia, as in Pierre Robin syndrome or Goldenhar’s syndrome, may be especially difficult to intubate.

The goal of the cardiovascular examination in the infant is two-fold; to assess the status of the circulatory system and to detect congenital heart disease. The rate, rhythm, volume, and character of the pulses in all four extremities should be evaluated. The resting heart rate of the healthy newborn averages 120–130 bpm. The precordium is examined by inspection, palpation, and auscultation. Clicks, murmurs, or other abnormal heart sounds should be sought. If a heart murmur is detected on the cardiovascular examination, there are specific concerns that must be addressed. An innocent murmur may be due to turbulent blood flow, whereas a pathological murmur is usually due to a structural abnormality; this distinction must be made. Lesions in which bacterial endocarditis prophylaxis or protection from paradoxical air embolism are required must be documented so that the anesthesia team is made aware. The child with a heart murmur or a history of a murmur warrants special consideration. The determination of an innocent versus pathologic murmur as well as the presence of hemodynamic compromise should be made. Innocent or non-pathologic heart murmurs can be identified by four characteristics: the murmur is early systolic to mid-systolic; it is softer than grade 3 of 4; the pitch is low to medium; and the sound has a musical, not harsh, quality. The infant should be evaluated for risk of paradoxical air embolus and evaluated for the need for prophylaxis for subacute bacterial endocarditis [48].

The abdomen should be observed for configuration, fullness, and movement with respiration. Major abdominal wall abnormalities such as gastroschisis, omphalocele, prune belly, or bladder extrophy will be obvious on inspection. A scaphoid abdomen may be an indication of abdominal contents that are displaced into the chest, as occurs in diaphragmatic hernia. A distended abdomen may be a sign of intestinal obstruction, ascites, or an abdominal mass. Palpation of the abdomen should include examination of the liver, and bowel sounds should be present on auscultation. Risk for aspiration of gastric contents should be determined.

The physical examination should include an evaluation of the level of consciousness, ability to swallow, intactness of the gag reflex, and an adequate cervical spine range of motion, hypotonia, spasticity, or flaccidity. General muscle tone and the presence of signs of an increase in intracranial pressure should also be noted.

Laboratory Testing

It is important to remember that phlebotomy is often traumatic for infants and their families, and an event that is not easily forgotten. For this reason, it is best to limit the number of invasive tests performed. The diagnostic studies should be selected based on the general medical health and the procedure being performed. In general, measurement of hematocrit in a healthy older infant undergoing elective surgery is unnecessary [49]. A hematocrit should be measured if significant blood loss is anticipated, if the child is less than six months of age or was born prematurely. Neither the routine measurement of the coagulation profile nor a history of “easy bruising” is reliable in predicting surgical bleeding [50]. The presence of prior hematoma, bleeding from circumcision or large bruises should prompt an investigation; however, a negative history for bruising in an otherwise healthy child would require no further testing. Routine preoperative urinalysis is not indicated in children, and serum chemistries should only be performed when an abnormality is suspected. Infants who are treated with anticonvulsants should have these medication levels checked and an electrocardiogram or chest radiograph should only be ordered if the general medical condition warrants.