The Medical Management of Infants and Children





Children are usually healthy when they come to the operating room for a surgical procedure. As a tertiary care center, however, we see a disproportionate number of children with chronic disease. These superimposed processes will affect the conduct of the surgical procedure and the anesthetic management of the child including the way that the child views you as a provider, the amount of stress that the parents feel, and sometimes even the developmental level of the child. An understanding of the natural history of some of the common diseases that affect infants and children is important for the practitioner that sees children as a part of their practice.
             As a general rule, if a child is not growing they are ill. Growth along a standard curve will determine whether caloric expenditure is being met by intake. Chronic, untreated illness increases work and thus caloric expenditure.  As examples, if a child has congenital heart disease, diabetes or asthma and if the child is not following some growth curve, then the therapy is not completely effective. (EG. For children with congenital heart disease, a lack of growth usually relates to cardiac failure or profound hypoxemia) Thus, an early signal to the practitioner that a child is ill is the lack of linear growth.
I would like for you to consider a few of the most common childhood diseases that we encounter. I will briefly discuss the natural history of these processes and the part that the disease plays in the perioperative management of an individual patient.


The child with congenital heart disease
Consider a child with Tetralogy of Fallot. These children present with an over riding aorta, VSD, RVH and infundibular hyperplasia. Because of these anatomic abnormalities any increase in pulmonary vascular resistance may lead to decreased pulmonary blood flow and increased cyanosis. For these children, control of the flow of blood back and forth through the VSD is an important determinant of general health. In these children any hypoxemia will produce an increase in pulmonary vascular resistance. Concomitant increased autonomic tone can lead to infundibular spasm, further reducing pulmonary blood flow – a so-called “tet spell”. Tet spells represent episodes of profound hypoxemia and can be treated by increasing the systemic vascular resistance so that blood is preferentially shunted left to right through the VSD increasing blood flow to the lungs. Neosynephrine is the drug of choice to increase systemic vascular resistance.
Growth of infants with TOF reflects the balance of hypoxemia and myocardial failure. Pulmonary blood flow that is luxuriant will increase lung water and the work of breathing. Unusual restriction of pulmonary flow will produce profound hypoxemia.
Current practice is to band the pulmonary artery soon after birth to restrict blood flow from the VSD and diminish the risk of failure. An infant that comes to the operating room before a definitive repair can be evaluated by determining the resting respiratory rate and whether the child is meeting growth goals.
The child that has had a Fontan procedure for palliation of hypoplastic left heart or other congenital cardiac anomalies represents a special case for the pediatric anesthesia practitioner. These children are dependent on the passive filling of the right heart in order to maintain cardiac output. Reduction of the filling pressure whether by dehydration or by an increase in pressure in the abdomen, such as during laparoscopy, will reduce the cardiac output dramatically. Most of these infants utilize the right ventricle for systemic and pulmonary blood flow.
The child that has pulmonary artery hypertension also represents a significant management problem for the anesthesiologist. PAH is common in children with untreated congenital heart disease in which the flow of blood left to right across an intracardiac defect is allowed to proceed unabated over time. Progressive remodeling of pulmonary artery vasculature with increases in the number and size of arteriolar smooth muscle results in increases in the pressure required to push blood through the pulmonary circuit. In these children, hypotension during induction or during the surgical procedure can


Apnea of Prematurity
            Apnea, defined as cessation of respiratory airflow, is common in premature infants prior to 36 weeks post conceptual age.  For a variety of reasons, infants that undergo surgery and anesthesia are at increased risk. Apnea associated with desaturation and/or bradycardia may be life threatening to these infants.
            Risk factors for apnea include hypothermia, use of narcotics, airway obstruction and hypoxemia. Anemia, GE reflux and hypoglycemia have also been associated with an increased incidence. Chronically ill infants may be chronically treated with theophylline or caffeine to prevent apnea
            The anesthetic for a premature infant should, ideally, be designed around their immature respiratory center and the probability of postoperative apnea. Short acting inhalational anesthetic agents, regional anesthesia rather than narcotics and increased attention to maintenance of normothermia, normoglycemia and a normal hematocrit reduce the probability of apnea. Treatment of at risk infants with methyl-xanthines such as caffeine or theophylline is extremely effective in reducing the incidence of apnea. Caffeine is available as a sodium benzoate derivative. Administration of 20 mg/kg as a slow bolus will provide several days of protection against apnea. 
The infant that has a history of severe apnea and has undergone a substantial operative procedure requiring blood replacement should probably remain ventilated postoperatively until homeostasis is attained. Likewise, neonates less than 2500 grams that are cold or metabolically unstable should remain intubated after the surgical procedure.
Infants less than 52 weeks post conceptual age should be monitored after general anesthesia for at least 12 hours.
             
Asthma
 Fifteen percent of children in the US will wheeze at some point during their development. Children from families that smoke and children that have been infected with the respiratory syncitial virus as infants are at increased risk. Usually mild and treatable with beta-adrenergic inhalers asthma may be significant, especially if the family fails to reduce the load of bronchial irritants in the home. Children from homes in which cigarettes or other tobacco products are used are at an especially high risk. Inhaled steroids and combination therapy – inhaled bronchodilators and steroids -  for children with chronic rather than episodic disease is considered a standard. Systemic steroids are contraindicated unless bronchospasm is very severe because of the impact on bone growth.
The child with significant asthma represents a problem for the anesthesiologist because of the irritability of their airways and the dramatic bronchospastic response to foreign body placement or the use of irritating gases such as desflurane. Sevoflurane has profound bronchodilatory properties and is the mainstay for maintenance of anesthesia. For children that are unresponsive to more conservative measures aminophylline is still available as is epinephrine.


Obstructive sleep apnea
OSA presents in obese children and may be ameliorated by airway surgery, including tonsillectomy. Many of these children are hypoxemic at night and the worst will have elevated pulmonary artery pressures leading to right heart failure. These children are very sensitive to narcotics after surgical procedures. It is important to note that, given the widespread obesity that is now seen in the pediatric population, the number of children that have OSA greatly exceeds the number that have been diagnosed. Children with a BMI over 35 are at high risk. If the same child has hypertension it really clinches the diagnosis.
Obstructive sleep apnea is a problem because of the sensitivity of these patients to narcotics and other sedatives. A common, and sometimes lethal, combination of a fentanyl patch for postoperative pain control and promethazine to control nausea will produce excessive somnolence. For this reason, the ambulatory treatment of these patients must be reserved for patients with home support that is impeccable.


Retrolental Fibroplasia
 RLF continues to be a common clinical entity despite our knowledge of the pathophysiology, because of the large number of very premature infants that are resuscitated. It is a response of the native vasculature of the retina to extreme changes in arterial oxygen levels. Hypoxia followed by relative hyperoxia produces neovascularization of the retina and may produce subsequent blindness. Untreated neovascularization will produce retinal detachment if untreated. This entity can be treated with cold probe and laser. The utilization of high levels of oxygen during anesthetics and surgical procedures in the premature is contraindicated if it can be avoided.

Bronchopulmonary Dysplasia
The resuscitation of infants less than 25 weeks of gestation, despite the use of prenatal steroid compounds to mature the lungs of the fetus and exogenous surfactant for postnatal use, has produced a whole new generation of infants with chronic lung disease. Because the final development of alveoli off of terminal bronchioles doesn’t begin until after thirty weeks, the effect of chronic ventilation and high levels of inhaled oxygen used in the treatment of respiratory distress syndrome is a serious inflammatory response, which resolves with fibrosis – Bronchopulmonary Dysplasia (BPD).
Many of these infants have well-established pulmonary hypertension that is exacerbated by events that surround a surgical procedure. Pain, hypoxemia, cold stress, or acidosis will aggravate the already increased pulmonary artery pressures and escalate V/Q mismatch producing profound hypoxemia. Because the right heart is under continuous stress, situations such as this with low levels of arterial oxygen and high PA pressures, produce right heart failure, which is, of course, the most common cause of left heart failure.
Infants with BPD vary in the amount of support that they require after the acute insult. Some go home on nasal cannula oxygen and diuretics. Many will leave the hospital accommodated to arterial carbon dioxide levels significantly above the norm; some greater than 60. For these infants, the balance of intravascular volume sufficient to support the cardiac output and grow but not so much that pulmonary interstitial water is increased is critical. For some the balance is so tenuous that postoperative ventilation is the only appropriate method of management for any surgical procedure more extensive that PE tubes.


Seizure disorders
 Children that have chronic seizure disorders are routinely placed on anticonvulsants and most are monitored for the therapeutic level of the drug. Efficacy of the regimen can be assessed by asking about the most recent level and the last time that the child had a seizure. For children that have seizures, which are particularly difficult to control, some provision for assuring the administration of the drug during the NPO period must be made.
 Most of the anticonvulsants have an impact on the metabolism of anesthetic drugs. Many will accelerate metabolism via cytochrome P450 reducing the beta half-life of action. Muscle relaxants are especially prone to this activity.
Valproic acid is commonly used for control of complex partial seizures. Massive bleeding associated with the inhibition of platelet function has been reported.

Sickle Cell Anemia
            Sickle cell anemia is still common in the United States. Predominately present in African Americans, it is also seen in Asians, Hispanics and people from the Indian subcontinent. It is the most common inherited genetic disorder in African Americans and the prevalence is about 1 in 400 live births in that population. An understanding of the pathophysiology over the last twenty years has reduced the number of children that present with severe sequelae such as stroke, pulmonary infarction and septic shock. The use of hydroxurea to produce myelosuppression and increase the production of Hgb F has been effective in cutting the number of painful crises in most children by one-half. 
            Red blood cells sickle in affected children when they are subjected to acidosis, hypoxia, or cold stress. Even the placement of a tourniquet for the surgical procedure can put the child at risk. Red blood cells that have an abnormal configuration do not carry oxygen efficiently and will be rapidly eliminated from the circulation by the microvasculature, or the spleen. Most children that are homozygous for S hemoglobin will have infarcted their spleen by the time that they are four years old. After this they are at increased risk for bacteremia and septic shock. Currently children that have good pediatric care receive pneumococcal vaccine early in their lives. Many of these children are also on prophylactic antibiotics.
            Children with sickle cell disease may present with a history of stroke or multiple episodes of lung infarction. These children may be on a hypertransfusion protocol in order to reduce their risk of a crisis. Those children that have not had any of these events and have been followed closely by knowledgeable clinicians have been shown to tolerate surgical procedures that are of short or intermediate duration, without tourniquets, with simple transfusion to a hematocrit of ten. For complicated patients, in addition to making every effort to avoid a sickle crisis, the level of Hgb S should be reduced to a level below 20% by exchange transfusion.
Sickle cell disease and the other hemoglobinopathies that afflict children and adolescents produce acute and chronic pain and represent a management dilemma for pediatricians and hematologists. Issues related to narcotic addiction, pseudo-addiction and tolerance are often encountered. Acute, severe pain, the presence of chronic disease, inevitable disagreements about the need for narcotics between patient and practitioners, and the lack of available resources for psychological and social support interact to reduce the possibility of successful long-term management.
Painful crises in patients with SS disease begin early in life, sometimes in infancy. The inability of a preverbal infant or child to communicate pain should not be taken as evidence that pain is not present. On the other hand, the natural history of painful crisis in children with sickle cell is variable. A substantial number of patients will have few hospitalizations for painful crisis while a few will require intensive medical therapy to prevent painful crisis and remain functional.
Frequently, patients with sickle cell refer themselves to an emergency room for treatment of a painful crisis. Because these healthcare providers do not know them, they may question the need for aggressive treatment. The anxiety that surrounds the possibility of lack of treatment accelerates the desire to be treated. In adolescents, faced with the possibility of not being treated at some point in the future, drug-seeking behavior – pseudo addiction  - becomes a part of their life. In part because of this circumstance, ER treatment of painful crisis should be discouraged or an accepted method for tracking the patient (database demonstrating history of past hospitalizations) should be established. Many states now track narcotic compounds that are prescribed. This too will assist as it provides some reassurance to the health care provider.  A comprehensive program to provide psychological and social support for these patients and their families will provide them a measure of  confidence that they are being heard.
Commonly, when care is not coordinated, or when the patient doesn’t avail themselves of comprehensive services, no health care provider can feel that they understand the patterns of illness for a given patient. When this happens, and the patient presents with painful crisis, physicians may believe that the patient falls within a group of chronic drug seeking individuals that may divert narcotics. Subsequently, the desire for narcotics increases and the cycle of pseudo addiction begins.
If the patterns of pain are known and if there is ongoing support, there is the opportunity to reduce drug-seeking behavior and decrease or shorten hospitalizations for painful crises. This should be one goal of a comprehensive program and, to some extent, the ongoing treatment of the patient may need to be contingent on close follow up and involvement with all of the resources that are available for support.


Cystic Fibrosis
            CF is the most common heritable disease in the Caucasian population with an incidence of 1: 3500 live births. It is an autosomal recessive trait that produces abnormalities in the CFTR gene. Though there are many permutations of this abnormality, in patients with the classic form of the disease, the abnormality affects the protein that acts as a chloride channel at mucosal surfaces.  Under normal conditions, as chloride exits a mucosal cell, water follows and mucous is thinned. In the patient with CF, mucous is thick and reduces mucociliary transport – a primary method for carrying debris out of the lungs. In addition, though it is thought of as primarily a pulmonary disease, evidence of the disorder can be found in the gut, liver, the exocrine pancreas and the skin. For the anesthesiologist, however, it is the pulmonary complications that are most problematic. Current therapy for pulmonary CF includes bronchodilators, inhaled antibiotics and adjuvants used to break up the tenacious secretions that inhabit the airway. Of note, many adolescents with CF are substantially underweight and this affects their ability to mount a substantial stress response.
Patients with cystic fibrosis may have pulmonary hypertension and heart failure, diabetes, anemia, GE reflux, malabsorption as well as abnormalities of the sweat glands. It is important to determine the severity of these secondary processes, as they will play a large role in morbidity and mortality associated with a surgical procedure.  






 All an eagle would really like, is a teapot























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