evaluation of the difficult pediatric patient

AMBULATORY ANESTHESIA 0889-8537/96 $0.00 + .20

EVALUATION OF THE DIFFICULT PEDIATRIC PATIENT

Ramesh Patel, MD, Phoebe Leith, MD, and Raafat Hannallah, MD

A decade ago only American Society of Anesthesiologists physical status (ASA PS) I or I1 patients undergoing short procedures were considered appropriate candidates for outpatient surgery. Today, duration of surgery is no longer a major determining factor, and procedures that last 4 to 6 hours are routinely performed on an ambulatory basis. Moreover, ambulatory surgery has been expanded to include patients who have chronic medical conditions.” Benefits of ambulatory surgery to children with chronic disease include maximizing time spent outside the hospital, minimizing the child’s separation from their family, reduced disruption of their schedule, and decreased exposure to other sick children in the hospital. The trend toward performing more complex surgeries on sicker patients in an ambulatory setting has created new challenges in performing rapid yet thorough evaluations and making expeditious decisions.” Selec- tion criteria for outpatients are continuously changing, such that rigid guidelines seem impractical. It seems most prudent to approach each patient individually.

The surgeon is the first physician to evaluate the patient for surgery. He or she has to decide the appropriateness of outpatient versus inpatient surgery. The surgeon also arranges for notification and consultation with various specialists, including the anesthesiologist. A preoperative visit with the anesthesiologist may be scheduled, if necessary. The anesthesiologist may also obtain information via a routine preoperative telephone screening call to the parents.‘* Reviewing pertinent information preoperatively will help avoid cancellations and delays. In chronically ill patients, such as children with cancer, complex congenital heart disease, chronic renal disease, severe asthma, cystic fibrosis (CF), and diabetes, the patient’s medical history is documented and then reviewed well in advance of the day of surgery. Occasionally, the anesthesiologist will confront an unex- pected problem, such as a previously undetected heart murmur or a patient

From the Departments of Anesthesiology, Children’s National Medical Center, and George Washington University Medical Center, Washington, DC

ANESTHESIOLOGY CLINICS OF NORTH AMERICA

VOLUME 14 * NUMBER 4 DECEMBER 1996 753

754 PATEL et a1

with a history suggestive of malignant hyperthermia susceptibility. In such cases no documentation may be available and the decision whether to proceed must be made promptly. Before performing ambulatory surgery in a child with a chronic disease three specific questions should be addressed:

1. Should surgery be performed on an ambulatory basis? This is decided in consultation with the surgeon, primary physician, and the family. The primary considerations are whether the patient will benefit from preoperative admission for therapy or postoperative admission for observation or therapy. Social issues, such as distance to hospital from home, parental skills and education, need for special equipment, and multidrug therapy during the immediate postoperative period, must be included in decision making.

2. Should the surgery be performed on the date scheduled? To determine the timing of surgery it must be decided if the patient is currently at his or her baseline level of health or whether additional therapy will be required to optimize the condition.

3. What laboratory tests need to be performed and where? Most children do not require any laboratory tests, but those with systemic diseases may require pertinent radiologic and laboratory studies before surgery.

Although a majority of children are healthy and undergo ambulatory surgery uneventfully, some pose special challenges for anesthesiologists. This article reviews these disease processes, treatment regimens, anesthetic implications, and considerations regarding perioperative disposition.

PREOPERATIVE FEAR AND ANXIETY

Children with chronic disease and their parents are often very anxious and demanding during hospitalization. Children have different causes of anxiety at various ages, and age-appropriate approaches must be undertaken to decrease their anxiety. For example, infants have nonspecific reactions to a new environ- ment and stress; they are comforted by holding and cuddling. Children up to 4 years of age are especially susceptible to the stress of parental separation. They should be reassured that their parents will be with them for as long as possible. Inducing anesthesia in the presence of the parents is most suitable for children between 18 months and 6 years to eliminate parental separation. Older children with chronic diseases may also benefit from parental presence. Adolescents have concerns about disfigurement, pain, and death. They may need a pharmacologic premedication. Many practitioners, however, hesitate to use narcotic premedicants because of potential problems of sedation, vomiting, and a consequent prolonged stay in the post-anesthesia care unit (PACU). Presently, midazolam is the most frequently used premedicant in ambulatory surgery.

ASTHMA

Asthma is the most common chronic disease of childhood, affecting 5% to 10% of children in the United state^.^ The hallmark of asthma is episodic increased airway resistance. The lability of the disease makes its management difficult for anesthesiologist^.'^ Conditions such as being emotionally upset, acute exposure to allergens, or manipulation of the airway can quickly provoke wheezing in a child who was previously asymptomatic. Sometimes children are

EVALUATION OF THE DIFFICULT PEDIATRIC PATIENT 755

asymptomatic when they arrive at the ambulatory surgery center but develop wheezing during the admission process. Stress of surgery is a major cause of such wheezing.

Preoperative Evaluation

Questioning the parents about medication regimen, severity and frequency of exacerbation, and need for emergency room treatments, hospital admissions, or ICU stay will give the clinician an indication of the severity of the child’s disease as well as the parents’ role in treating the disease and their level of education about the disease. Evaluation of a child with asthma begins by determining the type and severity of asthma.

Types of Asthma

Asthma may be classified into five types:

1. Allergic, extrinsic, or atopic asthma. Allergy accounts for most childhood asthma. It has a strong seasonal influence, with spring and fall being the worst seasons for many children with asthma.

2. Exercise-induced asthma. This may occur in older children and adolescents. The stimulus for bronchospasm appears to be rapid cooling of the airway. Therefore, warm, humidified anesthetic gases should be used to prevent onset of intraoperative wheezing in children with exercise-induced asthma.

3. Wheezing associated with respiratory illness. Respiratory infections sometimes provoke wheezing in infants and children, many of whom have mild underlying hyperactivity of the airways that manifests as wheezing only with the additional stimulus of a viral infection. Viral respiratory infection increases bronchial reactivity, even in normal individuals; therefore, it is not surprising that children with asthma are particularly af- fected by the swelling and hypersecretion caused by a viral respiratory infection. For these reasons, particular attention should be given to children with asthma who have upper respiratory infection (URI) symptoms. Careful evaluation is necessary before proceeding with anesthesia in these children.

4. Psychosomatic asthma. Emotional factors may precipitate or exacerbate psychosomatic asthma in a predisposed child. These children have been described as overly anxious, dependent, and insecure; therefore, pharmacologic premedication is strongly considered in such children to decrease preoperative anxiety. Anxiolytic agents, such as midazolam, may prevent asthmatic episodes by relieving anxiety.

5. Intrinsic asfhma. Intrinsic asthma is more common in adults than in children and is a diagnosis made by excluding other causes.

The anesthesiologist may not be as concerned with the cause of the asthma as with its severity. Asthma may be mild, moderate, or severe. Patients with mild asthma have only infrequent exacerbations and do not require continuous medication. Their symptoms are frequently seasonal or associated only with viral infections. They are treated with oral or inhaled beta agonists or oral theophylline. These patients are excellent candidates for ambulatory surgery.

756 PATEL et a1

Prophylactic inhalant beta agonist therapy may be administered in the holding area prior to surgery.

Patients with moderate asthma require daily medication to control symptoms. Besides daily beta agonist and theophylline, they may also require occa- sional steroid therapy. With proper treatment they remain symptom-free. It is important to communicate directly with their primary physician before scheduling such children for ambulatory surgery. They should continue to receive all their medications until the morning of surgery, and a beta agonist should be administered in the holding area by a nebulizer to young children or by an inhaler if the patient is older. Oral premedication may be considered for patients with stress-induced asthma. If the child has wheezing, persistent cough, or tachypnea on the day of surgery, it is best to reschedule surgery.

Patients with severe asthma have frequent exacerbations despite continuous medical therapy, and may be steroid dependent. When surgery is needed they frequently require preoperative hospital admission to optimize medical management of asthma. Following surgery, inpatient admission is often required to treat bronchospasm. These children are inappropriate candidates for ambulatory surgery.

Anesthetic Management

Intraoperative management of children with asthma should include sufficient depth of anesthesia and adequate hydration. Tracheal intubation should be avoided whenever possible. Histamine-releasing drugs are also avoided. If an endotracheal tube is inserted, beta agonist inhalant may be administered just before extubation. Deep extubation or intravenous lidocaine before extubation of the trachea should be considered. Children should not have any signs of wheezing before discharge from the facility.

DIABETES

Diabetes mellitus is the most common endocrine disease in children, oc- curring in 1.8 per 1000 school-age children.’ The basic defect is an absolute or functional deficiency of insulin, which causes impairment of glucose transport, decrease in lipid and protein synthesis, and hyperglycemia. The long-term effects are mainly due to changes in organ microvasculature, resulting in neurop- athy, nephropathy, ischemic heart disease, and vessel obstruction.

The terms juvenile diabetes and adult-onset diabetes are no longer used. In- stead, patients are categorized as type 1 (insulin-dependent diabetes mellitus [IDDM]) and type I1 (non-insulin-dependent diabetes mellitus [NIDDM]). Juve- nile diabetes is of the IDDM variety; the adult-onset diabetes may be either IDDM or NIDDM. Type I diabetes is characterized by insulin deficiency and is associated with disorders of the adrenal and thyroid glands whereas patients with type I1 diabetes have normal or high plasma insulin levels.

Preoperative Management

A careful history of the child’s age at the onset of diabetes, insulin require- ments, dietary habits, and frequency of hypoglycemic or hyperglycemic episodes must be obtained. It is best to consult the child’s endocrinologist or pediatrician


early to formulate a plan for the perioperative management of diabetes, including insulin administration. Patients whose diabetes is well controlled are appropriate candidates for ambulatory surgery.

It is best to schedule surgery as the first case of the day. Most patients can easily tolerate the present-day NPO guidelines. Recent less restrictive policies that allow sugar-containing clear liquid intake up to 2 hours prior to surgery have made it easier for diabetic patients to follow fasting guidelines. When the child arrives at the surgical center an intravenous catheter is inserted, a blood sample is drawn for glucose measurement, and dextrose-containing solution is administered at the maintenance rate. There are many formulas to manage the insulin administration. A common approach is to administer one-half to two- thirds of the child’s usual morning dose of intermediate or long-acting insulin. The authors usually request the parents to bring insulin and supplies from home and administer the insulin in the holding area after the intravenous access has been established.


Premedicants, such as barbiturates, midazolam, narcotics, and anticholiner- gics, do not alter glucose metabolism and may be administered in the usual manner. Anesthesia is induced through the previously inserted intravascular catheter. Blood glucose determinations are usually necessary at 2-hour intervals. Hyperglycemia occurs during surgery because of increases in cortisol level and sympathetic stimulation. If the surgical procedure is short, a sample of blood may be drawn just prior to extubation, thereby eliminating the need of blood drawing in the PACU. For short surgical procedures blood glucose is determined two to four times during the perioperative period; the last blood glucose deter- mination is done prior to discharge from the ambulatory center. Blood glucose is maintained between 80 and 200 mg per 100 mL. Although either a sliding scale or a continuous infusion method may be used to maintain this range, most pediatric anesthesiologists prefer the former method. For hyperglycemia, 0.1 unit per kg may be given intravenously. Alternatively, an infusion at a rate of units per hour equal to plasma glucose in mg/150 may be administered. Follow- ing insulin administration, glucose levels need to be monitored every hour.

The effects of anesthetic drugs on blood glucose concentration and insulin release are clinically insignificant in the total management of anesthesia in diabetic patients. It is advisable to use agents that minimize chances of postoperative vomiting. Prophylactic antiemetics should also be administered. Discharge planning is made with the parents in consultation with the pediatrician. Children need close monitoring until they are able to resume their normal oral intake. Diabetic children who are vomiting in the postoperative period are at great risk of developing hypoglycemia; therefore a low threshold for inpatient admission is necessary.

CHILDREN WITH CANCER

Common cancers in children are leukemia, osteogenic sarcoma, brain tumor, Wilms’ tumor, and neuroblastoma. Many children with cancer are scheduled as ambulatory patients for repeated biopsies, insertion or removal of central line catheters, and other minor procedures. Although the psychological and medical status of these patients are complicated, they benefit greatly from ambulatory

758 PATEL et a1

surgery because of reduced exposure to hospital-borne pathogens. They also benefit psychologically because the hospital or clinic stay is minimized.


These patients have problems related to the cancer (e.g., anemia, weight loss, loss of organ function), chemotherapeutic agents (e.g., cardiotoxicity), or psychological problems (depression, anger). Psychological problems are due to the stress of the chronic debilitating or life-threatening disease. The ability to cope with stress varies from patient to patient and family to family. Many patients are anxious, demanding, and fearful. A calm and reasonable, yet consis- tent, approach tempered with sensitivity and flexibility is necessary.

The chemotherapeutic agents frequently have more anesthetic implications than does the primary disease. It is important to be familiar with the side effects of all the anticancer drugs, but this is difficult because cancer treatment is often given according to protocols, and at least one new agent is included in each protocol. For this reason, communication between the oncologist and the anesthesiologist is vital. To facilitate this the authors have developed a simple, one- page form that is filled out by the oncologist when surgery is scheduled for children with cancer. The information requested includes type of cancer, names of the chemotherapy drugs, steroid treatment, total dose of doxorubicin (Adria- mycin), and results of recent echocardiogram studies. All chemotherapeutic agents have common side effects, such as anemia, thrombocytopenia, leukopenia, alopecia, nausea, vomiting, and stomatitis. Other specific side-effects of frequently used chemotherapeutic agents are listed in Table 1. Special attention is directed to two chemotherapeutic agents: Adriamycin and bleomycin. Adria- mycin is a cardiotoxic drug that may lead to cardiomyopathy, arrhythmias, and heart failure. Because of this risk, ejection fraction of the ventricle is periodically evaluated by the cardiologist with echocardiography. In general, the dose of Adriamycin is limited to 450 mg/m2. The other drug, bleomycin, causes damage to the pulmonary parenchyma. Supplemental oxygen administered to patients receiving bleomycin may damage the lung parenchyma, leading to respiratory failure. It is questionable whether the short period of perioperative exposure to higher oxygen concentration increases the risk of pulmonary parenchymal damage. The best approach is to maintain adequate oxygenation with the lowest possible inspired concentration of oxygen.

Appropriate laboratory tests should be obtained before surgery. A complete blood count with platelet count is necessary; but hepatic and renal function tests

Table 1. SIDE EFFECTS AND TOXICITY OF CHEMOTHERAPEUTIC AGENTS ~~~~~~~~~~

General Anemia, thombocytopenia, leukopenia, nausea,

Asparaginase Hepatic damage Bleomycin Pulmonary fibrosis Cisplatin Renal damage Daunorubicin Cardiomyopathy, arrhythmias Doxoru bicin Cardiomyopathy, arrhythmias Mercaptopurine Hepatic damage Streptozocin Renal and hepatic Thioguanine Hepatic damage

vomiting, alopecia, stomatitis


also may be essential to evaluate the patient. Patients who are receiving steroids need a stress dose during the intraoperative period. Corticosteroid 1.5 mg/kg up to a maximum of 100 mg is generally sufficient to cover intraoperative period. An additional dose is required during the postoperative period.


Vigilance regarding aseptic techniques is essential throughout the perioperative period because of immunosuppression. Induction of anesthesia may be challenging because these patients are anxious and fearful and the presence of a parent or an oncology nurse is useful. Most children are anesthetized in the usual manner; however, children who are treated with cardiotoxic drugs are very sensitive to potent inhalant anesthetics. If a venous access is already established, carefully titrated doses of ketamine may be used for induction of anesthesia, followed by a nitrous-narcotic and low-dose inhalation agent for maintenance of anesthesia. Children who have experienced emesis due to chemotherapeutic agents should receive intraoperative prophylaxis against vomiting. It is important to remember that parents of children with cancer are often very knowledgeable and should be involved in discharge planning.

CYSTIC FIBROSIS

CF is an autosomal recessive disease affecting infants, children, and adults. It is the most common lethal genetic disease among whites, in whom the incidence is 1 in 2000.2 It is a multisystem disease caused by widespread dysfunction of exocrine glands. The major pathologic features are abnormally high production of thick mucus, blockage of exocrine ducts, and obstruction of outflow of the exocrine glands. The major clinical manifestations include ob- structive pulmonary disease, pancreatic insufficiency, abnormally high sweat electrolyte concentrations, nasal polyps, and opacification of sinuses. Patients with CF have elevated sweat sodium, chloride, and potassium. Because the adrenal and renal functions are normal, serum electrolyte levels are not altered, despite increased sweat electrolytes.


CF may affect one or more systems in any combination. Furthermore, the severity of the disease in each system is quite variable. As a consequence, a child with CF may have minimal physiologic involvement or may be almost crippled by the disease. Their health status ranges from ASA PS class I1 to IV.

Chronic pulmonary disease is present in most patients and causes most of the mortality. Bronchial and bronchiolar obstruction by abnormally tenacious secretions is the cardinal manifestation of pulmonary involvement. Such obstruction leads to atelectasis, empyema, abscesses, and eventually to pulmonary hypertension and cor pulmonale. Patients with ASA PS I1 and 111 are generally appropriate candidates for ambulatory surgery, but pulmonary consultation should be obtained for patients with ASA PS 111 to specify the extent of pulmonary disease and to determine the plans for postoperative management.

Gastrointestinal tract involvement includes pancreatic insufficiency and deficiency of amylase, lipase, and pancreatic proteolytic enzymes from the duode-

760 PATEL et a1

num. As a result, ingested fat and nitrogen are lost through the stools. Meconium ileus and intestinal obstruction may occur because of the viscid, tenacious secretions in patients with CF, and malnutrition may be severe in infants.

Nasal polyps and opacification of the sinuses require surgical intervention in many patients. Nasal polypectomy, sinus endoscopy, and sinus lavage are probably the most common surgical procedures in patients with CF and are often performed on an ambulatory basis.

Some patients with CF take no routine medication whereas others may be taking as many as 10 drugs per day. Among the most common medications are beta agonist bronchodilators, aminoglycoside antibiotics, cephalosporins, pancreatase enzyme replacement, steroids, and mucolytic agents.


The extent of the pulmonary dysfunction is of most interest to anesthesiologists. All medications, particularly bronchodilator and steroid therapy, should be continued until the morning of surgery. Adequate hydration and humidifica- tion of anesthetic gases are essential during surgery. Excessive use of narcotics should be avoided to ensure rapid return of the cough reflex. Regional or topical anesthesia is often indicated to minimize the need for postoperative sedation.

CHRONIC RENAL FAILURE

Chronic renal failure occurs in 2.4 children per 1,000,000 population each year. The most common causes of isolated chronic renal failure in children are glomerulonephritis, pyelonephritis, and renal dysplasia. Renal failure may be associated with diseases of other organ systems, as in children with Alport syndrome, cystinosis, systemic lupus erythematosus, and hemolytic-uremic syndrome. Generally, children with renal failure take many medications that have important anesthetic implications; therefore, these children should be carefully evaluated before proceeding with ambulatory surgery.


A careful history documenting the cause and severity of renal failure, systemic manifestations, and medications should be obtained. Severity of illness may be difficult to assess in the early stages of disease because symptoms do not appear until 80% of the nephrons are destroyed. If the patient is on dialysis, the time of the last dialysis should be noted and results of electrolyte and coagulation studies following dialysis reviewed. In renal transplant patients the function of the graft and any transplant-related problems should be noted. Examination of mucous membranes and skin turgor is helpful in assessing hydration. Vital signs, including heart rate and blood pressure, should be checked. Metabolic, cardiac, pulmonary, neurologic, hematologic, and gastrointestinal problems may be consequences of renal failure and are important anesthetic considerations. Patients with renal failure have anemia and platelet dysfunction. They may have hypertension, congestive heart failure, or pericarditis. Metabolic derangements, such as hyperkalemia, metabolic acidosis, and hypocal- cemia, are common. Many patients have low gastric pH and gastroparesis, thereby increasing the risk of aspiration pneumonia. The patient should be


examined for signs of platelet dysfunction, such as petechiae, purpura, and ecchymoses. Presence of ascites and edema should also be noted.

Patients with chronic renal insufficiency usually take vitamin D and calcium supplements and receive calcitonin injections to ameliorate renal osteodystro- phy. Steroids and immunosuppressants are often used to control the primary disease. Multiple drug therapy is frequently required to treat hypertension. They may also take a combination of diuretics, beta blockers, calcium antagonists, or angiotensin converting enzyme (ACE) inhibitors to control hypertension. All regular medications should be continued until the morning of surgery. A minimal preoperative laboratory examination should include complete blood count, urinalysis, electrolytes, prothrombine time, partial thromboplastin time, blood urea nitrogen, and creatinine. Anemia, which is chronic, is not a contraindication to general anesthesia in these patients.


Patients may have intravascular volume depletion from dialysis or polyuria and may not tolerate prolonged NPO times. Intravascular volume depletion, in combination with antihypertensive medications, makes the child prone to hypotension during inhalation induction. If gastric paresis or severe ascites is present, an intravenous rapid sequence induction may be required; however, succinylcholine is avoided because it causes an increase in serum potassium. Alternatively, atracurium, vecuronium, or rocuronium may be used in a patient with renal failure. Medications that rely primarily on renal excretion for elimina- tion should be avoided. Because of the potential for oversedation due to benzodi- azepines and narcotics and residual muscle weakness from neuromuscular blocking agents, these agents should be carefully titrated. For hydration and fluid replacement, potassium-containing solutions are avoided. Generally, normal saline is used instead of lactated Ringer’s solution for fluid replacement. Knowledge of the pharmacology of various antihypertension medications is necessary for prudent anesthetic management. Clonidine decreases the level of minimum alveolar concentration (MAC) of inhaled anesthetics, beta-blockers in combination with rapid doses of narcotic may cause bradycardia, halothane can prolong the conduction block caused by verapamil, and the combination of nifedipine and isoflurane can lead to hypotension. None of these interactions, however, constitutes absolute contraindication to the use of these anesthetic techniques in children taking the antihypertensive medication^.^

The decision to employ a regional technique should be based on the degree of impairment of hemostasis. Renal failure patients are at increased risk of bleeding because of decreased platelet adhesiveness secondary to uremia and residual heparinization from the dialysis. Therefore, risks and benefits must be carefully evaluated before proceeding with a regional technique. Postoperatively, pain, nausea, and vomiting should be controlled and blood pressure should be at the preoperative level. The patient must be able to take all medications before or soon after discharge.

MALIGNANT HYPERTHERMIA SUSCEPTIBILITY

Malignant hyperthermia (MH) is a life-threatening, autosomal dominant disorder involving fulminant hypermetabolic activity of skeletal muscles trig- gered by volatile inhalation anesthetics, succinylcholine, and in some individuals, stress and exercise.6 The incidence of MH is 1:15,000 in children and 1:50,000

762 PATEL et a1

in adults. The incidence is as low as 1:220,000 when succinylcholine is avoided.6 Exposure to triggering agents may result in a hypermetabolic state manifested as tachycardia, tachypnea, fever, generalized rigidity, dysrhythmias, acidosis, hypercarbia, and increased oxygen consumption. Yentis et al,I4 who conducted a retrospective analysis of 303 children who were malignant hyperthermia- susceptible (MHS) and underwent surgery, concluded that postoperative admission solely on the basis of MHS label is not warranted.


MH is a genetic disease with autosomal dominant pattern with incomplete penetrance; therefore, all patients should be questioned about a family history of a high fever or unexplained death during anesthesia. Questions should also be asked about presence of any myopathy. Many patients will give a history of a "problem" with anesthesia, so further careful questioning may help the clinician determine the relevance of this disclosure; however, most patients who have intraoperative MH have no history of prior MH episode. Another complicating factor in children is that disorders known to be associated with MH may not yet be diagnosed in young pediatric patients presenting for their first surgery.

Patients are categorized into the following four groups on the basis of their history, physical examination, and laboratory tests:

Group 1-Healthy patient Group 2-Patients with diseases that mimic MH but are not associated

with MH (i.e., neuroleptic malignant syndrome, osteogenesis irnperfecta, glycogen storage disease)

Group 3-Muscular diseases capable of causing MH, such as central core disease, Duchenne muscular dystropy, King-Denborough syndrome, nemaline rod myopathy, and mitochondria1 myopathy. A history of unexplained muscle weakness or hypotonia influences the anesthesiologist to use a nontriggering anesthetic technique. If a nitrous-narcotic technique is chosen, the dose of muscle relaxants must be titrated and a nerve stimulator must be used in a hypotonic child to prevent prolonged postoperative paralysis.

Group 4-Known or suspected MHS. A patient with MHS is defined as one with a history of previous MH episode, history of MH in the immediate family, or history of previous masseter rigidity or positive muscle biopsy. Individuals with MHS may not have any physical findings suggesting the diagnosis.

Dantrolene prophylaxis in patients with MHS is controversial. Most patients with MHS do not need dantrolene prophylaxis. The current recommendations are to administer prophylactic dantrolene preoperatively to patients with stress- induced MH and to patients with severe coexisting cardiac, cerebrovascular, or renal disease who may not tolerate even a mild hypermetabolic state. Potential side effects of dantrolene administration include muscle weakness, lethargy, nausea, and vomiting. Those who need dantrolene prophylaxis are often unsuit- able candidates for ambulatory surgery.

A clear plan of action in an MH emergency should be available. An MH cart with dantrolene, sterile water to reconstitute dantrolene, sodium bicarbonate, mannitol, dextrose, furosemide, anti-arrhythmic drugs, and nasogastric and fo- ley catheters along with blood collection tubes should be readily available.



Premedication with an anxiolytic oral medication, such as midazolam or diazepam, reduces the stress associated with preoperative waiting. The anesthetic machine must be flushed with a high flow of air or oxygen for at least 10 minutes prior to its use in patients with MHS. MH-triggering agents, such as potent inhaled anesthetics and succinylcholine, are contraindicated. Intravenous agents, including narcotics, barbiturates, and propofol, are used. Regional blocks with bupivacaine are extremely useful adjuvants.

An elevation of end-tidal CO, is the most sensitive sign of MH; however, the beginning of some MH episodes may not be associated with end tidal CO, greater than 40 mm Hg. This is due to hyperventilation, inaccuracies in CO, measurement in children, or large gradients between end tidal CO, and arterial CO?. Tachypnea, tachycardia, arrhythmias, or sudden temperature elevation should prompt the anesthesiologist to obtain results of arterial blood gas (ABG) analysis. An ABG analysis is performed to determine the presence of acidosis and hypercarbia. Children who have not manifested any signs of MH during the intraoperative course are observed in the recovery area for signs of fever, tachycardia, myoglobinuria, and acidosis for at least 4 hours prior to discharge.

Time is of essence when managing a fulminant crisis. A nontriggering anesthetic agent must be substituted. Changing circuits, tubings, and absorbent is no longer recommended because it wastes too much time. Dantrolene is life- saving. An initial dose of 2 to 20 mg/kg may be needed. Cardiac arrest and dysrhythmias are caused by hyperkalemia and acidosis. Prompt aggressive treatment of hyperkalemia is recommended. Lidocaine or procainamide is used to treat dysrythmias. Calcium channel blockers are avoided because they cause cardiovascular collapse in the presence of dantrolene. Administer enough dantrolene to normalize all signs of MH and then transport the patient to an inpatient facility. The MH Hotline is open 24 hours per day and should be used. The new MH Hotline number is 1-800-MH-HYPER.

CONGENITAL HEART DISEASE

Congenital heart disease occurs in approximately 1% of all live births. Many children who previously would not have survived a complex cardiac defect are now undergoing palliative, staged, or total repair at younger ages, allowing them to survive into adulthood.10 Many such children are scheduled for noncardiac surgery. A good example is a child with Down’s syndrome who has a ventricular septal defect or endocardia1 cushion defect and is often scheduled for myringotomy and adenoidectomy. An organized plan with input from the cardiologist, surgeon, and the patient’s parents is essential to optimize perioperative care.

The following four questions should be answered when planning an anesthetic course:

1. Is pulmonary flow increased or decreased? Many congenital heart defects affect pulmonary blood flow. For example, atrial septal defect, ventricular septal defect, patent ductus arteriosus, and atrioventricular canal all increase pulmonary blood flow whereas tetrology of Fallot, pulmonary stenosis, pulmonary atresia, and tricuspid atresia decrease pulmonary blood flow.

2. Is there a predominant left-to-right or a right-to-left shunt?

764 PATEL et a1

3. Is there a stenosis? Is it at the valvular level (e.g., aortic stenosis) or at

4. What are the pathophysiologic effects of the anatomic defect? Cyanosis,

It is also essential to understand the anatomic connections made during palliative or definitive repairs to formulate an appropriate anesthetic plan. The following list outlines the most frequently encountered procedures. Children with cyanotic heart disease may have a systemic arterial or venous to pulmonary artery shunt to improve pulmonary blood flow?

1. The Blalock-Taussig shunt creates a shunt from the subclavian artery to pulmonary artery.

2. The Glenn procedure shunts blood from superior vena cava to right pulmonary artery.

3. The Waterston shunt anastomoses the ascending aorta to right pulmonary artery; the aorta-pulmonary graft is a similar procedure.

4. The Potts shunt takes blood from the descending aorta to the left pulmonary artery.

5. The Fontan procedure performed in children with single ventricle physi- ology creates a right atrium to pulmonary artery shunt. As pressure in the systemic and pulmonary curcuits will be similar, blood will only flow to the pulmonary artery if systemic venous pressure is maintained (i.e., by avoiding hypovolemia) and pulmonary vascular resistance is

A child with any of the above shunts must not be subjected to a long NPO time, should have early IV placement, and measures must be taken to prevent postoperative vomiting.

the vascular level (coarctation of the aorta)?

hypoxemia, or congestive heart failure?

10w.7


The preoperative preparation starts by notifying the cardiologist of the planned surgical procedure. The cardiologist’s description of the nature of the lesion, severity of shunt or stenosis, and its pathophysiologic effects, along with the list of current medications and recommendations for the perioperative period, is invaluable. The child’s exercise tolerance reflects the cardiopulmonary reserve. An active, acyanotic child is acceptable for ambulatory surgery. A history of increased fatigue, decreased activity, cyanotic spells, or dyspnea indicates that the child cannot fully cope with the cardiac lesion. Such a child needs to be carefully re-evaluated before scheduling ambulatory surgery.

Aside from usual components of physical examination, focus on the weight of the child, skin color, airway evaluation, respirations, peripheral arterial pulse, and venous access is essential. For example, a child with a left Blalock-Taussig shunt will have a decreased or absent left brachial and radial pulse because the left subclavian has been used to create the shunt. A blood pressure cuff should not be used on this arm.

All children with congenital heart disease who are scheduled for surgery must have had a recent hemoglobin/hematocrit to evaluate anemia or polycythemia. Polycythemia is an indication of elevated erythropoietin due to cyanosis. Children with moderate to severe polycythemia may not be suitable candidates for ambulatory surgery because hyperviscosity increases the risk of metabolic acidosis and sudden cardiac decompensation.



Adequate hydration is important in children with cyanotic congenital heart disease. NPO guidelines should be liberal enough to allow adequate hydration. Premedication is generally not necessary in all children. It is mainly used to decrease crying, fear, and anxiety associated with perioperative period. Subacute bacterial endocarditis (SBE) prophylaxis is generally recommended for any child who has a palliative, repaired, or unrepaired congenital heart lesion and who is scheduled for a surgical procedure that may seed the vascular system with bacteria.' Decisions for specific circumstances must be made in consultation with the cardiologist.' The recommendations of the American Heart Association " regarding SBE prophylaxis for pediatric patients at risk are summarized in Table 2.4

The anesthetic management plan is individualized on the basis of the patient's psychological outlook, physiologic condition, and the anesthesiologist's expertise. A variety of anesthetic induction regimens have been noted to maintain oxygen saturation and hemodynamic stability in infants and children with

Table 2. AMERICAN HEART ASSOCIATION RECOMMENDED PROPHYLAXIS FOR PEDIATRIC PATIENTS WHO ARE AT RISK

~~~~~~~~~~~~~~~~~~~ ~ ~ ~ ~

DENTAL, ORAL OR UPPER RESPIRATORY TRACT PROCEDURES Standard regimen

Amoxicillin 50 mglkg PO (rnax 3.0 g) 1 hour before procedure followed by half that

In amoxicillinlpenicillin-allergic patients: Erythromycin 20 mglkg (max 1 g) or dose 6 hours later

clindamycin 10 mglkg (rnax 300 mg)

that dose 6 hours latert

may be substituted

minutes before procedures' followed by amoxicillin 25 mglkg (max 1.5 g) PO 6 hours later

Alternate regimen (for patients unable to take oral medications) Ampicillin 50 mgikg (max 2 g) IV or IM 30 minutes before procedure* followed by half

In ampicillin/amoxicillin/penicillin-allergic patients: Clindamycin 10 mg/kg (max 300 mg)

Patients considered high-risk (and not candidates for standard regimen) Ampicillin 50 mg/kg (max 2.0 g) plus gentamicin 2.0 mg/kg (max 80 mg) IV or IM 30

If allergic use vancomycin 20 mg/kg IV (over 1 hour). No repeated dose necessary. GENlTOURlNARYlGASTROlNTESTlNAL PROCEDURES Standard regimen

Ampicillin 50 mg/kg (max 2.0 g) plus gentamicin 2.0 mg/kg (max 80 mg) IV or IM 30 minutes before procedure* followed by amoxicillin 25 mglkg (max 1.5 g) orally 6 hours later$

In ampicillin/amoxicillin/penicillin-allergic patients, vancomycin 20 rnglkg IV (over 1 hour) plus gentamicin 2.0 rng/kg IV or IM 1 hour before procedure; repeat 8 hours later

Alternate low-risk patient regimen Amoxicillin 50 mglkg PO (max 3.0 g) 1 hour before procedure followed by half that

dose 6 hours later

*At Children's National Medical Center the drugs are given intravenously (IV) as soon as an IV catheter is inserted after induction but prior to airway or surgical manipulation.

tAlternatively, oral amoxicillin 25 mglkg (max 1.5 g) may be administered if PO intake is tolerated. $Alternatively, the parenteral regimen may be repeated 8 hours later. PO = orally; IM = intramuscularly. From Hannallah RS: The pediatric patient. In Estafanous FG, Barash PG, Reves JG (eds): Cardiac

Anesthesia. Philadelphia, JB Lippincott, 1994; with permission.

766 PATEL et a1

complex congenital heart disease even though any one agent may have specific advantages? Extra care should be taken to remove air bubbles from the intravenous fluid administration line, particularly in a child with an arteriovenous shunt. Careful titration of anesthetic agents, judicious fluid administration, and hemodynamic and respiratory (oxygen-saturation and end-tidal COz) monitoring are keys to a successful outcome.

Discharge planning should be based on adequacy of hydration, absence of vomiting, and ability to resume medications. The second dose of SBE prophylaxis antibiotic is given 6 hours following the first dose. Although providing anesthesia to pediatric ambulatory surgical patients with congenital heart disease is not easy, it can be a very satisfying endeavor.

References

1. Dajani AS, Bisno AL, Chung KJ, et al: Prevention of bacterial endocarditis. Circulation

2. DiSant-Agenese PA: Cystic fibrosis. In Vaughan VC, McKay RJ, Behrman RE (eds): Nelson’s Textbook of Pediatrics. Philadelphia, WB Saunders Company, 1981, pp 1988- 2001

3. Dodge RR, Burrows B: The prevalence and incidence of asthma and asthma-life symptoms in a general population sample. Am Rev Respir Dis 122:567-575, 1980

4. Hannallah RS The pediatric patient. In Estafanous FG, Barash PG, Reves JG (eds): Cardiac Anesthesia. Philadelphia, JB Lippincott, 1994, pp 779-790

5. Kambam J: Principles of anesthesia for children with congenital heart disease. In Kambam J (ed): Cardiac Anesthesia for Infants and Children. St. Louis, Mosby, 1994,

6. Kaplan RF: Malignant Hyperthermia. Annual Refresher Course Lecture 522:l-7, 1993 7. Keon TP, Templeton JJ: Disease of the endocrine system. In Katz J, Steward DJ

(eds): Anesthesia and Uncommon Pediatric Disease. Philadelphia, WB Saunders, 1987,

8. Laishley RS, Burrows FA, Lerman J, et a1 Effect of anesthetic induction regimens on oxygen saturation in cyanotic congenital heart disease. Anesthesiology 65673-677,1986

9. Mathews DM, Miller ED. Mechanisms and treatment of perioperative hypertension. Refresher Courses in Anesthesiology 18237-249, 1990

10. Moore RA: Anesthetizing the child with congenital heart disease for noncardiac surgery. Refresher Courses in Anesthesiology 22:211-226, 1994

11. Patel RI, Hannallah RS: Complications following pediatric ambulatory surgery. Ambu- latory Anesthesia 3:83-86, 1995

12. Patel RI, Hannallah RS Preoperative screening for pediatric ambulatory surgery: Evaluation of a telephone questionnaire method. Anesth Analg 75:258-261, 1992

13. Wilson DF The child with asthma. In Berry FA (ed): Anesthetic Management of Difficult and Routine Pediatric Patient. New York, Churchill Livingstone, 1986, pp 273- 313

14. Yentis SM, Levine MF, Hartley EJ: Should all children with suspected or confirmed malignant hyperthermia susceptibility be admitted after surgery? A 10-year review. Anesth Analg 75345-50, 1992

83~1174-1178, 1991

pp 119-134

pp 311-344

Address reprint requests to Ramesh Patel, MD

Department of Anesthesiology Children’s National Medical Center

111 Michigan Avenue, N.W. Washington, D.C. 20010

evaluation of the difficult pediatric patient

Documents