Medical Conditions Influencing Anesthetic Management




Upper Respiratory Tract Infection


Infants and children often have or are recovering from a runny nose or other manifestations of upper respiratory tract infection (URTI) when they are seen for evaluation before general anesthesia. Indiscriminate cancellation of children with any symptom of URTI is unwarranted and causes emotional and financial problems for children and their families; each case needs to be carefully evaluated. Some children seem to have a runny nose most of the time, possibly because of allergies or a chronic nasal infection; these children should be distinguished from those with an acute URTI.


Children with an uncomplicated URTI who are otherwise healthy have a greater incidence of intraoperative desaturation, bronchospasm, and laryngospasm. Although these complications can be disturbing, most are easily managed (see Laryngospasm, Chapter 4 ). It should be noted that airway irritability after a URTI may last for 6 to 8 weeks, thus delaying the procedure 2 weeks will not reduce the incidence of these complications. Infants less than 1 year of age, infants who were born premature, children exposed to second-hand smoke, and children with reactive airways disease with a concomitant URTI may have more serious airway problems during and after anesthesia. Children with any history of URTI should be carefully monitored en route to the PACU; postoperative desaturation is more common. Pulmonary complications in children having major (i.e., cardiac) surgery may be more common if there has been a recent (within 2 weeks) history of URTI. This may result from the fact that viral infections alter the reactivity of the airway for such a period and may also predispose to other infections.


Recent evidence suggests anticholinergics do not affect the incidence of perioperative airway complications in children with URTI. Children with chronic rhinorrhea may receive one to two drops of either Neo-Synephrine (0.25%) or oxymetazoline per nostril to dry up secretions during anesthesia.


Children with bronchospasm (i.e., asthma) that complicates a URTI may benefit from their usual dose of bronchodilators in the preoperative period. Preoperative bronchodilators and a vital capacity cough may resolve bronchospasm and airways plugged with mucus. Intraoperatively, albuterol or the more recent, levoalbuterol, may be delivered through an ETT by first agitating the canister for 30 seconds, and then second, inserting it stem down into a 60 ml syringe (after the barrel is removed) and then reinserting the barrel. The syringe should be screwed onto the capnography port of the elbow of the breathing circuit and the barrel compressed. Evidence indicates that 3% to 8% of the aerosol delivered into the ETT using this technique reaches the trachea. The remainder layers out on the wall of the tracheal tube. To deliver most of the content of each puff to the tip of the tube, a long narrow gauge (e.g., 19 gauge) catheter may be inserted to the distal third of the tracheal tube. In this manner, the majority of the aerosol reaches the tracheal mucosa. Most avoid tracheal intubation in these children if the airway can be managed with an LMA; this reduces the incidence of bronchospasm. However, evidence also suggests that the incidence of laryngospasm increases when LMAs are used in children with recent URTIs.


The following plan of action is suggested ( Figure 6-1 ):



  • 1.

    Elective surgery



    • a.

      The child should be carefully assessed. A history of the URTI should be obtained along with a detailed history of any other illnesses. A careful physical examination should be performed, looking particularly for any evidence of systemic illness, purulent nasal secretions, or lower respiratory tract disease.


    • b.

      Children with mild URTI but without pyrexia or any other evidence of disease may be accepted for minor surgical procedures because evidence indicates little increased risk of complications. The decision to proceed should be discussed with the parents and the surgeon. Anesthesia via a facemask or LMA, avoidance of endotracheal intubation when practical, administration of atropine, and the use of sevoflurane may reduce airway complications.


    • c.

      Children who present for elective surgery with any one of the following should be rescheduled after 4 weeks: 1. Pyrexia greater than 38.5 °C; 2. Change in behavior/diet/activity; 3. Purulent secretions; or 4. Signs of lower respiratory tract involvement (e.g., wheezing) that do not clear with a forced cough.


    • d.

      Children with a history of asthma and a URTI demand special attention; nonurgent surgery should be deferred for 4 weeks whenever possible.



  • 2.

    Emergency or urgent surgery: Children who require emergency surgery cannot be deferred because of a URTI. The anesthetic prescription should account for the presence of a full stomach and the type of surgery but the presence of a URTI requires no special modifications. Sevoflurane is an acceptable anesthetic for children with mild URTI. Airway problems and laryngospasm must be anticipated, and all necessities for their treatment should be immediately at hand. When suitable, the laryngeal mask airway (LMA) should be used as an alternative to tracheal intubation; it may result in fewer airway complications. Postoperatively, the child should be carefully observed.




Figure 6-1


Algorithm for management of upper respiratory tract infection. (Fever is > 38.5C)


Suggested Reading


  • Tait A.R., Malviya S.: Anesthesia for the child with upper respiratory tract infection: still a dilemma?. Anesth Analg 2005; 100: pp. 59-65.



  • Asthma


    Asthma affects 4% to 13% of children in various parts of North America. The disease is characterized by variable cough, wheezing, and breathlessness and is episodic and seasonal in many. The symptoms result from bronchoconstriction, mucosal edema, and tenacious secretions in the small airways. Severe attacks may occur throughout childhood and may be life threatening. Acute exacerbations may be associated with URTIs, allergens, irritants, exercise, or emotional stress. The treatment for mild asthma is inhaled β-adrenergics for bronchodilation and improved mucociliary clearance. For more severe asthma, inhaled corticosteroids may be added to control inflammation. Theophylline, which has been relegated to third-line asthma therapy, is sometimes used to prevent nocturnal bronchospasm. Severe asthmatic attacks may require systemic corticosteroid therapy and ICU admission. The disease often improves as the child ages. The severity of the disease is usually judged by the therapy, which is required to control the symptoms; mild asthma is controlled by inhaled β-adrenergics with increasing severity suggested by the addition of inhaled corticosteroids. Rarely, oral steroids are prescribed for asthma but if they are, it suggests a recent exacerbation.


    When a child with asthma presents for elective surgery, it is most important to determine whether the child’s current status is optimal. The following are important considerations.



    • 1.

      If possible, surgery should be delayed for at least 1 month after the last acute attack; during this period, airway reactivity may be increased and residual mucosal edema and secretions may impair pulmonary function.


    • 2.

      Elective surgery should be deferred if there is any evidence of an active viral URTI. A URTI can precipitate an exacerbation of symptoms.


    • 3.

      The frequency of the asthma attacks, and the symptoms between attacks should be documented. Has admission to an intensive care unit or ventilator therapy ever been needed? If so, repeat severe attacks are likely.


    • 4.

      What medications is the child taking, and are they controlling the child’s symptoms? Have systemic corticosteroids been necessary? If so, in what dose? Has the child taken any of the usual asthma medications today? If the child is receiving theophylline therapy, the blood level of the drug should be measured preoperatively.


    • 5.

      Physical examination of the chest is important to detect bronchospasm and exclude any other current pulmonary pathology. If wheezing is present, the child should be encouraged to cough deeply. If the wheezing is unresolved, a trial of bronchodilator therapy should be administered. If the signs do not resolve, then elective surgery should be deferred.


    • 6.

      The results of recent pulmonary function tests and especially any response to bronchodilator therapy should be noted.


    • 7.

      A chest radiograph should be ordered for any child with significant symptoms.



    Anesthesia Management


    Preoperative




    • 1.

      Ensure that the child receives routine asthma medications up to the time of surgery. Oral medications can be taken with a sip of water; inhalations may be repeated, if necessary, just before transfer to the operating room.


    • 2.

      A stress-dose of steroids (IV hydrocortisone [1 to 1.5 mg/kg]) should be administered at induction of anesthesia to those taking the equivalent of greater than 5 mg prednisone per day (adult dose), oral steroids within 3 months or high-dose inhaled steroids. Nonetheless, testing for adrenal suppression is uncommon, which leads prevailing opinion to suggest that a single dose of steroids is unlikely to do harm and may prevent an adrenal crisis in the perioperative period.


    • 3.

      Order appropriate sedation to calm the child. Oral midazolam is the most widely used premedication for children in North America. Atropine, if considered necessary, may be given orally or intravenously at induction; it decreases secretions and causes some bronchodilation.



    Perioperative




    • 1.

      For intravenous induction, propofol is the preferred induction agent as thiopental may release histamine and possibly cause bronchoconstriction. Alternatively, ketamine may be used since it is a bronchodilator and may protect against bronchospasm; however, atropine should be given to limit secretions.


    • 2.

      Inhalation induction with sevoflurane is preferred. Halothane may precipitate arrhythmias in children also receiving theophylline.


    • 3.

      Avoid agents known to release histamine and cause bronchospasm (e.g., atracurium, morphine). Desflurane increases airway resistance in asthmatic children. Nitrous oxide, halothane, sevoflurane, fentanyl, pancuronium, rocuronium, and vecuronium are preferred drugs.


    • 4.

      If tracheal intubation is necessary, it should be performed gently when the child is deeply anesthetized; otherwise, the procedure may trigger bronchospasm. Alternatively, lidocaine 1.5 mg/kg IV may be administered 3 to 4 minutes before intubation. If possible, avoid tracheal intubation for minor or brief procedures. The LMA may be a very useful alternative.


    • 5.

      The anesthetic gases should be warmed and humidified—this is less essential if a circle circuit is used.


    • 6.

      Intraoperative wheezing should be treated by deepening the level of anesthesia and by giving bronchodilator aerosols via the endotracheal tube (e.g., albuterol) (see URTI). Be careful to exclude nonasthmatic causes for wheezing (e.g., a partially obstructed endotracheal tube, endobronchial intubation, pneumothorax, etc.).


    • 7.

      At the end of surgery, atropine and neostigmine may be administered to antagonize the muscle relaxants as necessary. Neostigmine may increase bronchomotor tone, but this effect is counteracted by the atropine. Extubation is preferably performed with the child deeply anesthetized and breathing spontaneously so as to minimize the risk of precipitating bronchospasm. If awake extubation is planned, intravenous lidocaine or propofol may be administered beforehand to reduce laryngeal reflexes.



    Postoperative




    • 1.

      Humidified oxygen should be administered.


    • 2.

      When practical, regional analgesia is ideal for pain relief; for major surgery, continuous regional analgesia may be planned. Otherwise, use intravenous fentanyl or PCA morphine (see Chapter 7 ).


    • 3.

      Postoperative wheezing may require additional doses of an aerosol bronchodilator and appropriate adjustment of other medications.



    Suggested Reading


  • Doherty G.M., Chisakuta A., Crean P., et. al.: Anesthesia and the child with asthma. Paediatr Anaesth 2005; 15: pp. 446-454.



  • Cystic Fibrosis


    Cystic fibrosis (CF) is an inherited disorder that results from a genetic defect on chromosome 9. Abnormal chloride and sodium transport result in increased electrolyte content and increased viscosity of secretions. This disorder affects many body systems and may present in the neonate as meconium ileus. During childhood, malabsorption due to pancreatic insufficiency predominates. In the second decade, however, malabsorption is superseded by increasing pulmonary problems because of abnormally viscous secretions. Respiratory failure usually develops by the second or third decade of life, secondary to retained secretions and chronic infection. Even if they appear fairly well, many of these children have severe pulmonary ventilation-perfusion ( <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='V./Q.’>V./Q.V./Q.
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    ) inequality. However with intensive therapy many children are now surviving to adulthood.


    Surgery for children with this condition is most commonly for nasal polypectomy (in many cases repeated), functional endoscopic sinus surgery (FESS), antral lavage, or bronchoscopy for removal of retained secretions and treatment of atelectasis. Some children with advanced disease may present for lung transplantation. Transplanted lungs do not appear to be affected by this otherwise generalized disease.


    Special Anesthesia Problems




    • 1.

      Copious, extremely viscous secretions are present in the respiratory tract. Violent coughing and laryngospasm may occur during induction.


    • 2.

      Because of the <SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='V./Q.’>V./Q.V./Q.
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      disturbances:



      • a.

        Hypoxia may develop rapidly during anesthesia.


      • b.

        Induction of anesthesia with inhalational agents is prolonged because of <SPAN role=presentation tabIndex=0 id=MathJax-Element-3-Frame class=MathJax style="POSITION: relative" data-mathml='V./Q.’>V./Q.V./Q.
        V . / Q .
        mismatch; this is exacerbated with less soluble anesthetics such as sevoflurane.



    • 3.

      Lung compliance is reduced. In severe late cases, very high airway pressures may be required to adequately ventilate the lungs and prevent hypoxemia. Therefore a cuffed endotracheal tube should always be used.


    • 4.

      Malnutrition and underweight for age is a result of malabsorption and chronic infection. Liver function may be reduced in older children. In such cases, drug dosages should be adjusted accordingly. (In younger children metabolism of some drugs is enhanced.)


    • 5.

      Many children with advanced CF suffer all the emotional upset of those with chronic disease; all of them require very careful and considerate handling and much reassurance.



    Anesthesia Management


    Preoperative




    • 1.

      Assess the child’s condition carefully; ensure that the pulmonary status is optimized before surgery by means of postural drainage, physiotherapy, and inhalation therapy. These should be continued until the immediate preoperative period.


    • 2.

      Pulmonary function is usually at its worst early in the morning. If possible, schedule the surgery at a time that allows for chest physiotherapy and clearing of secretions preoperatively.


    • 3.

      Do not give opioid premedication as oxygenation may be compromised. Give midazolam for anxiolysis.


    • 4.

      Ensure optimal hydration; fluids must not be withheld for prolonged periods. The child should be offered clear fluids until 2 hours preoperatively.



    Perioperative


    N.B. Whenever possible, use local or regional analgesia.



    • 1.

      Establish intravenous access for hydration and emergency drug administration.


      If general anesthesia is required:


    • 2.

      Give 100% O 2 by mask for at least 5 minutes in children with pulmonary involvement; these children are very used to having IV access, so if indwelling IV is not present, start an IV and induce anesthesia intravenously with propofol and a muscle relaxant. Inhalational inductions in children with serious <SPAN role=presentation tabIndex=0 id=MathJax-Element-4-Frame class=MathJax style="POSITION: relative" data-mathml='V./Q.’>V./Q.V./Q.
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      mismatch will be protracted and delayed.


    • 3.

      Intubate the trachea using a cuffed endotracheal tube.


    • 4.

      Suction the trachea and remove secretions frequently.


    • 5.

      Use humidified gases with sufficient oxygen added to maintain an adequate SaO 2 (100% O 2 may be necessary for children with severe CF).


    • 6.

      Do not give long-acting medications; use a technique that ensures the child’s rapid recovery.



    Postoperative




    • 1.

      Give fluids intravenously until the child is drinking well.


    • 2.

      Nurse the child with humidified oxygen. Whenever possible place the child in a semirecumbant position that increases respiratory comfort.


    • 3.

      Provide optimal analgesia. Use regional analgesia and NSAIDs for postoperative pain whenever possible.


    • 4.

      Encourage early chest physiotherapy and ambulation.



    Suggested Reading


  • Della Rocca G.: Anaesthesia in patients with cystic fibrosis. Curr Opin Anaesthesiol 2002; 15: pp. 95-101.



  • Hematologic Disorders


    Anemia


    Children requiring surgery may be anemic. Remember that the hemoglobin (Hb) concentration, normally 18 to 20 g/dl at birth, decreases to a nidus of about 10 to 11 g/dl by 3 months of age and thereafter increases gradually to 12 to 14 g/dl by 6 years of age ( see Table 4-10 ).


    In the preterm infant, the Hb often decreases to lower concentrations because of a reduced red blood cell mass at birth, brief survival time of fetal red blood cells, and poor erythropoietin response. Frequent blood sampling may exacerbate the anemia. In children, Hb levels below normal for age are most frequently caused by poor diet. Anemia discovered before elective surgery should be fully investigated and corrected before surgery. Most children with a chronic Hb level of 7 to 9 g/dl (i.e., renal failure) can be safely anesthetized provided no further blood loss takes place. If, however, the Hb is less than 7 g/dl, the physiologic consequences of anemia may significantly compromise the margin of safety during anesthesia, particularly if substantial surgical bleeding is expected.


    The following considerations are relevant for children with anemia:



    • 1.

      Transport of oxygen to the tissues can be maintained only by increased cardiac output or increased oxygen extraction from the blood. The major compensation is the increase in cardiac output; shift of the Hb-O 2 dissociation curve, caused by increased 2,3-diphosphoglycerate (2,3-DPG), contributes relatively little. At a Hb level less than 8 g/dl, the cardiac output must increase to compensate for the decreased oxygen-carrying capacity.


    • 2.

      Coronary sinus blood is normally very desaturated; therefore, in anemia, oxygen transport to the heart muscle can be maintained only by increased coronary blood flow. At Hb levels less than 5 g/dl, the ability of the myocardium to meet its own needs is compromised resulting in subendocardial ischemia and high-output congestive cardiac failure may occur.


    • 3.

      Anemic children may be at increased risk for cardiac arrest during anesthesia. The factual data to support this hypothesis are scant, but it seems reasonable to suppose that children with severe anemia have a reduced margin of safety.


    • 4.

      Children with significant cardiac or respiratory disease require a greater concentration of Hb than normal children: 14 g/dl should be considered the minimum acceptable, and some children need greater concentrations.


    • 5.

      Preterm infants who are anemic are more prone to perioperative apnea.



    The following plan of action is suggested for routine elective surgery:



    • 1.

      If a significant anemia is discovered, delay elective surgery until the anemia has been diagnosed and corrected. In children with iron-deficiency anemia, the Hb level increases significantly after 3 to 4 weeks of oral iron therapy.


    • 2.

      If surgery cannot be delayed, a decision must be made whether to proceed despite the anemic state or to transfuse packed cells to correct the severe anemia. This decision depends on many factors, such as the age and health of the child and the expected surgical blood loss.


    • 3.

      For the anemic child, use an anesthetic technique that is optimal for the anemic state:



      • a.

        Avoid excessive preoperative sedation.


      • b.

        Oxygenate the child before induction.


      • c.

        Use increased concentrations of inspired oxygen during anesthesia.


      • d.

        Always use an endotracheal tube.


      • e.

        Use controlled ventilation and maintain normocapnia.


      • f.

        Be cautious with myocardial depressant drugs.


      • g.

        Carefully replace fluids to maintain the intravascular volume; hypovolemia must be avoided if the cardiac output is to be maintained.


      • h.

        Do not extubate until the child is fully awake.


      • i.

        Give additional oxygen continuously during transport to and in the postanesthesia care unit (PACU).


      • j.

        Keep the child normothermic throughout.




    Suggested Reading


  • Gunawardana R.H., Gunasekara S.W., Weerasinghe J.U.: Anesthesia and surgery in pediatric patients with low hemoglobin values. Ind J Ped 1999; 66: pp. 523-526.
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    Mar 27, 2019 | Posted by in ANESTHESIA | Comments Off on Medical Conditions Influencing Anesthetic Management
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