Dr abdollahi

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Anesthesia and pulmonary diseases

• Dr abdollahi

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• Thoracic and upper abdominal operations are a
  particular risk for patients with chronic
  pulmonary disease.

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Obstructive airway diseases

• Asthma and chronic obstructive pulmonary disease
  (COPD), the two major categories of obstructive
  airway disease, affect millions of Americans and
  cause significant morbidity and mortality
  worldwide.

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• Asthma is a chronic inflammatory disorder of the
  airways characterized by variable airflow
  obstruction, airway inflammation, and bronchial
  hyperresponsiveness.

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• In contrast, the airflow obstruction in COPD is
  defined as progressive and not fully reversible.
  The chronic inflammation of the airways and lung
  parenchyma in COPD is most often secondary to
  cigarette smoke exposure.

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• Together, asthma and COPD constitute a major
  public health concern, and a basic understanding
  of these diseases is important when caring for
  patients who receive anesthesia.

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ASTHMA

• Asthma is a disease that is defined by the
  presence of
• (1) Chronic inflammatory changes in the
  submucosa of the airways
• (2) Airway hyperresponsiveness
• (3) Reversible expiratory airflow obstruction.

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• Airway hyperresponsiveness characterizes this
  disease, even in asymptomatic patients, and is
  demonstrated by the development of
  bronchoconstriction in response to stimuli
  (allergens, exercise, mechanical airway
  stimulation) that have little or no effect on
  normal airways. Airway hyper responsiveness
  elicited during methacholine bronchoprovocation
  and airway bronchodilation in response to inhaled
  albuterol help diagnose asthma.

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Clinical Symptoms

• The classic symptoms associated with asthma are
  cough, shortness of breath, and wheezing.
  However, symptoms of asthma may vary and range
  from cough with or without sputum production to
  chest pain or tightness. Chronic,
• nonproductive cough may be the sole initial
  complaint.

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• Some asthmatics also experience symptoms
  exclusively
• with exertion ("exercise-induced asthma"), and
  this diagnosis
• is a consideration in the pediatric and young
  adult population.

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• The presence or absence of wheezing on physical
  examination is a poor predictor of the severity
  of airflow obstruction. Thus, the presence of
  wheezing suggests airway narrowing, which should
  be confirmed and quantified by spirometry.

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• Degrees of obstraction are defined according to
  the FEV1 predicted .
• Reversibility of obstruction after the
  administration of a
• bronchodilator suggests a diagnosis of asthma.

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• An increase in FEV1 predicted of more than 12
  and an increase in FEVl of greater than 0.2 L
  suggest acute bronchodilator responsiveness and
  variability in airflow obstruction.
• In contrast, the airways of patients with COPD do
  not demonstrate reversibility of airflow
  obstruction to the same degree as do those with
  asthma, a characteristic that can help
  distinguish these two causes of airflow
  obstraction.

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• During severe asthma exacerbations, intravenous
  therapy
• with glucocorticoids is the mainstay of therapy.
  In rare
• circumstances, when life-threatening status
  asthmaticus
• persists despite aggressive pharmacologic
  therapy, it may
• be necessary to consider general anesthesia
  (isoflurane or
• sevoflurane) in an attempt to produce
  bronchodilation.

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Management of Anesthesia

• Pulmonary function studies (especially FEV1)
  obtained
• before and after bronchodilator therapy may be
  indicated
• in a patient with asthma who is scheduled for a
  thoracic
• or abdominal operation. Measurement of arterial
  blood
• gases before proceeding with elective surgery is
  a consideration
• if there are questions about the adequacy of
  ventilation or arterial oxygenation.

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• All asthmatics who have persistent symptoms
  should be treated with either inhaled or systemic
  corticosteroids (depending on the severity of
  their airflow obstruction), in addition to
  scheduled dose of inhaled beta agonists. Therapy
  should be continued throughout the perioperative
  period. Supplementation with cortisol may be
  indicated before major surgery for
  corticosteroid-dependent asthmatics because of
  suppression of the hypothalamic-pituitary-adrenal
  axis.

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REGIONAL ANESTHESIA

• Regional anesthesia may be preferred when the
  surgery is
• superficial or involves the extremities. Notably,
  however,
• bronchospasm has been reported in asthmatics who
  have received spinal anesthesia, although it is
  generally accepted that regional anesthesia is
  associated with lower complication rates related
  to bronchospasm in the asthmatic population.

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GENERAL ANESTHESIA

• The goal during induction and maintenance of
  general anesthesia in patients with asthma is to
  depress airway reflexes in order to avoid
  bronchoconstriction in response to mechanical
  stimulation of the airway. Before tracheal
  intubation, a sufficient depth of anesthesia
  should be
• established to minimize bronchoconstriction with
  subsequent
• stimulation of the airway. Rapid intravenous
  induction of anesthesia is most often
  accomplished with the administration of propofol
  or thiopental. Propofol
• may blunt tracheal intubation-induced
  bronchospasm in
• patients with asthma.

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• ketamine (1 to 2 mg/kg IV) is an alternative
  selection for rapid induction of anesthesia
  because its sympathomimetic effects on bronchial
  smooth muscle may decrease airway resistance. The
  increased secretions associated with the
  administration of ketamine, however, may limit
  the use of this drug in patients with asthma.
• Sevoflurane and isoflurane are potent volatile
  anesthetics that depress airway reflexes and do
  not sensitize the heart to the cardiac effects of
  the sympathetic nervous system stimulation
  produced by beta-agonists and aminophylline.

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• Bronchodilation with sevoflurane and isoflurane
  depends on the ability of the normal airway
  epithelium to produce nitric oxide and
  prostanoids. Halothane is also an effective
  bronchodilator but may be associated with cardiac
  dysrhythmias in the presence of sympathetic
  nervous system stimulation.
• Desflurane may be accompanied by increased
  secretions,
• coughing, laryngospasm, and bronchospasm as a
  result of
• in vivo airway irritation.

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• Although case reports suggest that
  bronchodilation follows the intravenous
  administration of lidocaine, the clinical
  significance of this response is unclear and the
  data are equivocal.

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• In asthmatic patients undergoing tracheal
  intubation, premedication with inhaled albuterol
  should be the first choice of therapy to prevent
  intubation-induced bronchoconstriction.
• Neuromuscular blocking drugs that are not
  associated with endogenous histamine release may
  also be used in patients with asthma .

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• Although histamine release has been attributed to
  succinylcholine,there is no evidence that this
  drug is associated with increased airway
  resistance in patients with asthma.

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• Intraoperatively, Pao2 and Paco2 can be
  maintained at
• normal levels by mechanical ventilation of the
  lungs at
• a slow breathing rate (6 to 10 breaths/min) to
  allow
• adequate time for exhalation, an important
  maneuver
• in patients with increased airway resistance.
  This slow
• breathing rate can usually be facilitated by the
  use of a
• high inspiratory flow rate to allow the longest
  possible
• time for exhalation. Positive end-expiratory
  pressure
• (PEEP) should be used cautiously because of the
  inherent,
• impaired exhalation in the presence of narrowed
  airways.

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• At the conclusion of elective surgery, the
  trachea may be extubated while the depth of
  anesthesia is still sufficient to suppress airway
  reflexes. After the administration of
  anticholinesterase drugs to reverse the effects
  of nondepolarizing neuromuscular blocking drugs,
  bronchospasm may occur but is not usual, which
  may reflect the protective effects (decreased
  airway resistance) of simultaneously administered
  anticholinergics. When extubation is delayed for
  reasons of safety until the patient is awake
  (possible presence of gastric contents),
  intravenous administration of lidocaine may
  decrease the likelihood of airway stimulation as
  a result of the endotracheal tube in an awake
  patient.

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Intraoperative Bronchospasm

• Airway instmmentation can cause severe reflex
  bronchoconstriction and bronchospasm, especially
  in asthmatic patients with hyperactive airways.
  The bronchospasm that occurs intraoperatively is
  usually due to factors other than acute
  exacerbation of asthma. The frequency of
  perioperative bronchospasm in patients with
  asthma is low, especially if their asthma is
  asymptomatic at the time of surgery.

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• It is important to first consider mechanical
  causes of obstruction and inadequate levels of
  anesthesia before initiating treatment of
  intraoperative bronchospasm.
• Fiberoptic bronchoscopy may be useful to rule out
  mechanical obstraction in the tracheal tube.
  Asthma related
• bronchospasm may respond to deepening of
  anesthesia with a volatile anesthetic.

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• If the bronchospasm is due to asthma and persists
  despite an increase in the concentration of
  delivered anesthetic drug, albuterol should be
  administered by attaching a metered-dose inhaler
  to the anesthetic delivery system. When
  bronchospasm persists despite B2- agonist
  therapy, it may be necessary to add intravenous
  corticosteroids.

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CHRONIC OBSTRUCTIVE PULMONARY DISEASE
EMPHYSEMA AND CHRONIC BRONCHITIS

• COPD consists of two entities, emphysema and
  chronic
• bronchitis. The Global Initiative for Chronic
  Obstructive
• Lung Disease (GOLD) guidelines provide criteria
• for diagnosis and classification of severity in
  patients with
• symptoms of chronic cough, sputum production, or
  exposure
• to cigarette smoke .

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• Emphysema is characterized by loss of elastic
  recoil of the lungs, which results in collapse of
  the airways during exhalation and increased
  airway resistance.

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• Chronic bronchitis is defined by the presence of
  cough and sputum production for 3 months in each
  of 2 successive years in a patient with risk
  factors, most commonly cigarette smoking. It has
  been estimated that 25 of surgical patients
  smoke and a further 25 are ex-smokers, thus
  making COPD an important diagnosis to consider in
  any patient undergoing anesthesia.

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Prediction of Postoperative Outcome

• The need for preoperative pulmonary function
  studies
• in patients with COPD is controversial because of
  the
• questionable correlation of these tests with
  postoperative
• outcome. Although the FEV! predicted has been
  used
• to grade the severity of airflow obstraction,
  data have
• shown that using a multidimensional grading
  system to
• assess the respiratory and systemic extent of
  COPD is a
• better predictor of mortality than using FEV,
  alone.

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BODE index.

• This grading system is based on four variables-
• 1Body mass index (B)
• 2Severity of airflow obstraction (0)
• 3Functional dyspnea (D)
• 4Exercise capacity as assessed by the 6-minute
  walk test (E)

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• Patients with higher BODE scores were at higher
  risk for death. Hypercapnia and hypoxemia, as
  detected by arterial blood gas analysis, may also
  characterize patients with moderate to severe
  airflow obstmction. Chronic hypoxemia may lead to
• pulmonary hypertension and cor pulmonale.
  Preoperative
• detection plus treatment of hypoxemia-induced cor
• pulmonale with supplemental oxygen is an
  important
• part of preoperative management.

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Management of Anesthesia

• The presence of COPD does not dictate the use of
  specific
• management of anesthesia. If general anesthesia
  is selected, a volatile anesthetic with
  humidified inhaled gases and mechanical
  ventilation of the lungs is useful. drugs or
  techniques (regional or general) for the
  management of anesthesia.

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• Nitrous oxide may be used, but potential
  disadvantages include
• limitation of the inhaled concentrations of
  oxygen and passage of nitrous oxide into
  emphysematous bullae.
• Nitrous oxide could lead to enlargement and
  rupture of these bullae and result in the
  development of tension pneumothorax.

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• Opioids are acceptable but are less ideal for
  maintenance of anesthesia because of the frequent
  need for high inhaled concentrations of nitrous
  oxide to ensure amnesia and associated decreases
  in inhaled concentrations of oxygen. To avoid
  this problem, administration of a volatile
  anesthetic at a low concentration may be
  substituted for nitrous oxide. Postoperative
  depression of ventilation may also reflect the
  residual effects of opioids administered
  intraoperatively.

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MANAGEMENTOF VENTILATION

• Patients with COPD are ventilated in a manner
  similar to
• those with asthma. Small tidal volumes may be
  delivered
• to decrease the likelihood of gas trapping and
  barotrauma.
• Slow breathing rates are used to permit maximal
  time for
• exhalation. Continued tracheal intubation and
  mechanical
• ventilation of the lungs in the postoperative
  period are
• often necessary after major surgery in patients
  with severe
• emphysema. Postoperative depression of
  ventilation may
• also reflect the residual effects of opioids
  administered.

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• Hypercapnia secondary to chronic hypoventilation
  should not be corrected intraoperatively because
  it may then be difficult to wean the patient from
  mechanical ventilation as a result of the
  decreased respiratory drive in patients who
  chronically hypoventilate.

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Pulmonary HYPERTENSION

• Pulmonary hypertension is defined as an elevation
  in
• mean pulmonary artery pressure to levels higher
  than
• 25 mm Hg at rest or higher than 30 mm Hg with
  exercise.
• Most cases of pulmonary hypertension are
  secondary to
• cardiac or pulmonary disease in a minority of
  cases, the
• etiology is unknown and the pulmonary
  hypertension is
• considered primary.

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Classification

• The World Health Organization has proposed a
  classification
• of pulmonary hypertension that includes pulmonary
• hypertension secondary to left heart disease,
  pulmonary
• disease, vascular disease, and primary pulmonary
  hypertension.
• Indicators of disease severity include dyspnea
  at rest, hypoxemia, syncope, metabolic acidosis
  indicating
• low cardiac output, and signs of right heart
  failure on
• physical examination (elevated jugular venous
  pressure,
• hepatomegaly, and peripheral edema).

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Diagnostic Evaluation

• Diagnostic evaluation for pulmonary hypertension
  includes
• the electrocardiogram echocardiogram chest
  roentgenogram
• assessment for secondary causes such as pulmonary
• embolism (computed tomographic angiography or
• ventilation/perfusion scanning), underlying
  pulmonary
• disease (pulmonary function testing), collagen
  vascular
• disease, or liver failure and right heart
  catheterization.

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• Right heart catheterization is the gold standard
  for diagnosis
• because it provides data on the severity of
  pulmonary
• artery hypertension, as well as pulmonary venous
  pressure
• and cardiac output, which have prognostic
  significance.
• In addition, right heart catheterization is a
  necessary part
• of testing for vasodilator response, the first
  step in the
• algorithm to determine appropriate therapy for
  pulmonary
• artery hypertension.

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Pathophysiology

• Chronic elevation of pulmonary artery pressure
  leads to
• elevated right ventricular systolic pressure,
  hypertrophy
• and dilatation of the right ventricle, and
  resultant right
• ventricular failure. Right ventricular preload
  and pulmonary
• blood flow are dependent on venous return in this
  setting.

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Management of Anesthesia

• Intraoperative considerations for a patient with
  severe pulmonary hypertension include maintaining
  adequate preload, minimizing tachycardia and
  cardiac dysrhythmias that may decrease cardiac
  output, and avoiding arterial hypoxemia and
  hypercapnia, which can increase pulmonary
  vascular resistance (PVR). Cardiac output from a
  failing right ventricle is critically dependent
  on filling pressure from venous return and
  pulmonary pressure.

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• Options for treatment of pulmonary hypertension
  during surgery include inhaled nitric oxide (10
  ppm), inhaled prostacyclin (either intermittent
  or continuous), and phosphodiesterase inhibitors
  such as milrinone. Pulmonary artery catheters
  have been used for intraoperative monitoring.

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PARTURIENTS

• Mortality in pregnant patients undergoing vaginal
  delivery
• is near 50 and may be even higher when cesarean
  delivery
• is performed. Most often, vaginal deliveries are
  preferred,
• although regional anesthesia may be used
  successfully during
• cesarean sections. The danger of decreased venous
  return
• secondary to the sympathetic nervous system
  blockade
• produced by regional anesthesia should be
  considered.

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POSTOPERATIVE PERIOD

• In the postoperative period, care must be taken
  to avoid
• large-volume fluid shifts, arterial hypoxemia,
  systemic
• hypotension, and hypovolemia in patients with
  pulmonary
• hypertension. Morbidity and mortality in the
  postoperative
• period are significant concerns, with possible
  causes
• including pulmonary vasospasm, increases in
  pulmonary
• artery pressure, fluid shifts, cardiac
  dysrhythmias, and
• heightened sympathetic nervous system tone.

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OBSTRUCTIVE SLEEP APNEA

• Patients with obstructive sleep apnea (OSA) are
  at high risk for postoperative complications when
  undergoing general anesthesia. OSA is reported to
  occur in 2 of middle-aged women and 4 of
  middle-aged men. It is suspected, however, that
  up to 80 of cases of OSA are undiagnosed, thus
  suggesting that those with this disorder may be a
  significant portion of the surgical population.

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• Obesity is the most significant risk factor for
  the development
• of OSA, with a body mass index greater than 30
  and a large neck circumference (gt44 cm) being
  positively correlated with severe OSA. Obese
  patients with OSA or suspected OSA are at risk
  for complications during tracheal intubation and
  extubation, as well as during the postoperative
  period.,

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• Comorbid medical illnesses such as hypertension
  cardiovascular disease, and congestive heart
  failure are also more prevalent in patients with
  OSA than in the general population, a fact that
  contributes to their postoperative morbidity.
  Systemic hypertension has been reported in up to
  50 of patients with OSA and is independent of
  obesity, age, and gender.

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• Treatment of OSA by noninvasive ventilation
  results in better control of systemic
  hypertension. In addition to systemic
  hypertension, pulmonary hypertension is more
  prevalent in these patients than in the general
  population, One common
• mechanism that may explain both the systemic and
  pulmonary
• hypertension in patients with OSA is the chronic
  decrease
• in Pa02 during apneic episodes.

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Management of Anesthesia

• Evaluation of the oral cavity in patients with
  OSA may not reveal the true nature of their
  pharyngeal space because increased fat deposition
  in the lateral pharyngeal walls has been
  demonstrated in these patients and shown to
  correlate with the severity of OSA. Neck
  circumference reflects pharyngeal fat deposition
  and correlates more strongly with the incidence
  and severity of OSA than general obesity dose.

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IMPACT OF SEDATIVE DRUGS

• Relaxation of the upper airway musculature in
  response to benzodiazepines may significantly
  reduce the pharyngeal
• space and result in longer periods of hypopnea,
  arterial hypoxemia, and hypercapnia in patients
  with OSA than in the general population.

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• Any medications that depress the central nervous
  system must be administered carefully because
  airway patency and skeletal muscle tone,
  maintained in the awake state, may be lost at the
• onset of sleep. In addition, opioid analgesics
  may decrease
• the central respiratory drive and thus further
  add to the
• possible complications of sedation.

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ANTICIPATION OF DIFFICULT AIRWAY MANAGEMENT

• Full preparation for difficult airway management,
  including
• the availability of orotracheal tubes of various
  size, a
• Fastrach laryngeal mask, and a fiberoptic
  bronchoscope,
• should be made before initiating direct
  laryngoscopy for
• tracheal intubation.

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• Adequate preoxygenation is necessary in obese
  patients with OSA because of their reduced
  functional residual capacity and risk for
  arterial hypoxemia with induction of anesthesia.
  Tracheal extubation should be performed only when
  the patient is breathing spontaneously with
  adequate tidal volumes, oxygenation, and
  ventilation.

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MANAGEMENTIN THE POSTOPERATIVE PERIOD

• Respiratory depression and repetitive apnea in
  the postoperative period can occur in patients
  with OSA,
• especially in the setting of opioid
  administration for pain
• control. It should also be noted that in patients
  with OSAwho hypoventilate (obesity-hypoventilation
  syndrome),
• careful documentation of preoperative arterial
  blood gases is necessary to establish the
  baselinc set point for ventilation, an important
  factor whcn considering the patient's respiratory
  drive after extubation.

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• Relativc hyperventilation intraoperatively to
  maintain a norma Paco2 in subjects who
  chronically hypoventilate may result in prolonged
  apnea when attempting extubation.

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Smoking Cessation

• The risk for postoperative pulmonary
  complications among smokers as opposed to
  nonsmokers is greatly increased.The length of
  preoperative smoking cessation necessary to
  decrease this risk is not clear. It is generally
  accepted that the increased incidence of
  postoperative pulmonary complications in smokers
  can be reduced significantly by persuading the
  patient to stop smoking before surgery, although
  there is no consensus on the minimal or optimal
  duration of preoperative abstinence.

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DISCONTINUATION OF SMOKING

• Smoking increases airway irritability and
  secretions, decreases mucociliary transport, and
  increases the incidence of postoperative
  pulmonary complications. Cessation of smoking for
  12 to 24 hours before surgery decreases the level
  of carboxyhemoglobin, shifts the oxyhemoglobin
• dissociation curve to the right, and increases
  the oxygen available to tissues.

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• In contrast to these short-term effects,
  improvement in mucociliary transport and small
  airway function and decreases in sputum
  production require prolonged abstinence (8 to 12
  weeks) from smoking. The incidence of
  postoperative pulmonary complications decreases
  with abstinence from cigarette smoking for

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• Nevertheless, it is useful to encourage smoking
  abstinence in the perioperative
• period, especially because smoking shortly before
  surgery may be associated with an increased
  incidence of ST-segment depression on the
  electrocardiogram.

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Tuberculosis
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Tuberculosis

• Mycobacterium tuberculosis is an obligate aerobe
  responsible for TB. This organism survives most
  successfully in tissues with high oxygen
  concentrations, which is consistent with the
  increased presentation of TB in the apices of the
  lungs.

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• Almost all M. tuberculosis infections result from
  aerosol (droplet) inhalation. It has been
  estimated that up to 600,000 droplet nuclei are
  expelled with each cough and remain viable for
  several days. Although a single infectious unit
  is capable of causing infection in susceptible
  individuals, prolonged exposure in closed
  environments is optimal for transmission of
  infection.

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• It is estimated that 90 of patients infected
  with M. tuberculosis never become symptomatic and
  are identified only by conversion of the
  tuberculin skin test. Often patients who acquire
  the infection early in life do not become
  symptomatic until much later. Patients who are
  HIV seropositive or immunocompromised are at much
  higher risk of becoming symptomatic

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• Sputum smears and cultures are also used to
  diagnose TB. Smears are examined for the presence
  of acid-fast bacilli. This test is based on the
  ability of mycobacteria to take up and retain
  neutral red stains after an acid wash. It is
  estimated that 50 to 80 of individuals with
  active TB have positive sputum smears. Although
  the absence of acid-fast bacilli does not rule
  out TB, a positive sputum culture containing M.
  tuberculosis provides a definitive diagnosis.

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• Health care workers are at increased risk of
  occupational acquisition of TB. For example, TB
  is twice as prevalent in physicians as in the
  general population. Persons involved with
  autopsies are uniquely at risk.

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Diagnosis

• The diagnosis of TB is based on the presence of
  clinical symptoms, the epidemiologic likelihood
  of infection, and the results of diagnostic
  tests. Symptoms of pulmonary TB often include
  persistent nonproductive cough, anorexia, weight
  loss, chest pain, hemoptysis, and night sweats.
  The most common test for TB is the tuberculin
  skin (Mantoux) test. The skin reaction is read in
  48 to 72 hours, and a positive reading is
  generally defined as an induration of more than
  10 mm.

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• For patients with AIDS, a reaction of 5 mm or
  more is considered positive. The skin test is
  limited, and alternative screening and diagnostic
  tests are undergoing evaluation. The skin test is
  nonspecific and may be positive if people have
  received a bacille Calmette-Guérin vaccine or if
  they have been exposed to TB, or perhaps even
  other mycobacteria, even if there are no viable
  mycobacteria present at the time of the skin test.

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• Chest radiographs are important for the diagnosis
  of TB. Apical or subapical infiltrates are highly
  suggestive of infection. Bilateral upper lobe
  infiltration with the presence of cavitation is
  also common. Patients with AIDS may demonstrate a
  less classic picture on chest radiography, which
  may be further confounded by the presence of PCP.
  Tuberculous vertebral osteomyelitis (Pott's
  disease) is a common manifestation of
  extrapulmonary TB.

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• Anesthesiologists are at increased risk of
  nosocomial TB by virtue of events surrounding the
  induction and maintenance of anesthesia that may
  induce coughing (tracheal intubation, tracheal
  suctioning, mechanical ventilation).Bronchoscopy
  is a high-risk procedure associated with
  conversion of the tuberculin skin test in
  anesthesiologists. As a first step in preventing
  occupational acquisition of TB, anesthesia
  personnel should participate in annual tuberculin
  screening such that those who develop a positive
  skin test may be offered chemotherapy. The
  decision to take chemotherapy is not trivial as
  treatment for TB carries the serious toxicity. A
  baseline chest radiograph is indicated when a
  positive tuberculin skin test first manifests

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Treatment

• Anti-TB chemotherapy has decreased mortality from
  TB by more than 90.With adequate treatment, more
  than 90 of patients who have susceptible strains
  of TB have bacteriologically negative sputum
  smears within 3 months. In the United States,
  vaccination with bacille Calmette-Guérin is not
  recommended, as it may not confer immunity and
  confounds the diagnosis of TB.

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• Some argue that, for protection of the community,
  people who have positive skin tests should
  receive chemotherapy with isoniazid. However, the
  flipside is that isoniazid is a toxic drug and
  treatment is only strictly indicated if there are
  radiographic features of pulmonary TB or if there
  are suggestive symptoms. The toxicity of
  isoniazid manifests in the peripheral nervous
  system, liver, and possibly the kidneys.
  Neurotoxicity may be prevented by daily
  administration of pyridoxine. Hepatotoxicity is
  most likely to be related to metabolism of
  isoniazid by hepatic acetylation. Depending on
  the genetically determined traits, patients may
  be characterized as slow or rapid acetylators.
  Hepatitis appears to be more common in rapid
  acetylators, consistent with the greater
  production of hydrazine, a potentially
  hepatotoxic metabolite of isoniazid. Persistent
  elevations of serum transaminase concentrations
  mandate that isoniazid be discontinued, but mild,
  transient increases do not.

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• Other drugs used to treat TB include
  pyrazinamide, rifampicin, and ethambutol. Adverse
  effects of rifampicin include thrombocytopenia,
  leukopenia, anemia, and renal failure. Hepatitis
  associated with increases in serum
  aminotransaminase concentrations occur in
  approximately 10 of patients being treated with
  rifampicin. In order to be curative, treatment
  for pulmonary TB is recommended for 6 months.
  Extrapulmonary TB usually requires a longer
  course. Noncompliance with therapy contributes to
  the emergence of resistant TB strains.

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Management of Anesthesia

• The preoperative assessment of patients
  considered to be at risk of TB includes a
  detailed history, including the presence of a
  persistent cough and the tuberculin
  status.Elective surgical procedures should be
  postponed until patients are no longer considered
  infectious. Patients are considered noninfectious
  if they have received antituberculous
  chemotherapy, are improving clinically, and have
  had three consecutive negative sputum smears.

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• If surgery cannot be delayed, it is important to
  limit the number of involved personnel, and high
  risk procedures (bronchoscopy, tracheal
  intubation, and suctioning) should be performed
  in a negative-pressure environment whenever
  possible. Patients should be transported to the
  operating room wearing a tight-fitting N-95 face
  mask to prevent casual exposure of others to
  airborne bacilli. Staff should also wear N-95
  masks.

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• If patients have TB of the cervical spine,
  special precautions should be taken not to injure
  the spine during airway manipulation. A high
  efficiency particulate air filter should be
  placed in the anesthesia delivery circuit between
  the Y connector and the mask, laryngeal mask
  airway, or tracheal tube. Bacterial filters
  should be placed on the exhalation limb of the
  anesthesia delivery circuit to decrease the
  discharge of tubercle bacilli into the ambient
  air. Sterilization of anesthesia equipment
  (laryngoscope blades) is with standard methods
  using a disinfectant that destroys tubercle
  bacilli.

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• Use of a dedicated anesthesia machine and
  ventilator is recommended. Positive-pressure
  ventilation has been associated with massive
  hemoptysis in a patient with old pulmonary TB
  leading to the recommendation that maintenance of
  spontaneous breathing may be indicated in
  selected patients. Postoperative care should, if
  possible, take place in an isolation room,
  preferably with negative pressure.

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lists important considerations in regard to
tuberculosis.

1. With the acquired immunodeficiency syndrome
   epidemic, tuberculosis is reemerging worldwide.
2.    Multidrug resistant and extensively
   drug-resistant strains are resistant to therapy
   and have increased virulence.   
3. Symptoms include persistent cough, anorexia,
   weight loss, chest pain, hemoptysis, and night
   sweats.  
4.   Anesthesiologists are at increased risk of
   nosocomial tuberculosis.   
5. Treatment for pulmonary tuberculosis is
   recommended for 6 months.   

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• 6. Noncompliance with therapy contributes to the
  emergence of resistant tuberculosis strains.   
• 7. Staff and patients should wear N-95 masks.  
•  8. A dedicated anesthesia machine and
  ventilator should ideally be used.   
• 9. Postoperative care should take place in an
  isolation room with negative pressure.

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UPPER RESPIRATORY TRACT INFECTIONS

• Patients may arrive at the hospital for elective
  tonsillectomy and adenoidectomy with an acute
  upper respiratory tract infection. Surgery for
  these patients is usually postponed until
  resolution of the upper respiratory tract
  infection, which is typically 7 to 14 days.
  Laryngospasm with airway manipulation may be more
  likely to occur in the presence of an upper
  respiratory tract infection.

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• URI has diffuse effects on the respiratory
  epithelium, mucociliary function, and airway
  reactivity. These effects combine to provide the
  potential for an increased risk for anesthesia in
  specific clinical settings. If the planned
  surgical
• procedure is short and airway support is
  restricted to the use of a facemask, the risk for
  an adverse respiratory event is minimal.

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• If an endotracheal tube is required, the risk for
  an adverse respiratory event is increased (up to
  10- fold) over that in an infant without a URI
  whose trachea
• is not intubated. An LMA seems to be associated
  with risks midway between those associated with a
  facemask and those with an endotracheal tube.
  Younger age plus a ORI seems to be associated
  with an increased risk from anesthesia. URIs
  develop recurrently in 1- to 6-year-olds, and if
  reactive airways accompany the infection, the
  effect on the airway persists for 2 to 6 weeks.

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• Ultimately, the preoperative evaluation must
  weigh the inconvenience of rescheduling
• against ignoring possible risks. If the decision
  is to
• proceed with elective surgery, the infant should
  be
• considered to have reactive airways.

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• The decision to cancel surgery on a child with an
  uncomplicated ORI always requires assessment from
  the viewpoint of a specific patient and family, a
  specific procedure, and a specific surgeon. A
  strict protocol for when to
• cancel surgery is impractical. The patient's age,
  medical and anesthetic history, current physical
  examination, planned surgery (placement of
  tympanostomy tubes versus surgery for
  craniofacial repair), and anticipated
  postoperative care (need for mechanical
  ventilatory support) must be analyzed.

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• Ultimately, the preoperative evaluation must
  weigh the inconvenience of rescheduling against
  ignoring possible risks. If the decision is to
  proceed with elective surgery, the infant should
  be considered to have reactive airways.

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Epiglottitis

• Acute epiglottitis is an infectious disease
  caused by Haernopbilus infiuenzae type B. It can
  progress rapidly from a sore throat, to airway
  obstruction, to respiratory
• failure and death if proper diagnosis and
  treatment are delayed. Patients are usually
  between 2 and 7 years of age, although
  epiglottitis has been reported in younger
• children and adults.

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• Characteristic signs and symptoms of acute
  epiglottitis include
• (1) a sudden onset of fever, dysphagia,
  drooling, thick muffled voice, and preference for
  the sitting position with the head extended and
  leaning forward (2) retractions, labored
  breathing, and cyanosis when respiratory
  obstruction is present.

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Treatment

• Direct visualization of the epiglottis should not
  be attempted in an awake patient because it could
  lead to airway compromise and death. Interactions
  with the patient should be kept to a minimum.
  Stimulation of the patient or the onset
• of struggling during attempted treatment
  procedures may result in exacerbation of the
  airway obstruction. Induction of anesthesia is
  often accomplished with the
• inhalation of sevoflurane (alternatively,
  halothane) while maintaining spontaneous
  ventilation.

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• It is important to secure the airway without
  stimulating the reactive airway.
• An emergency airway cart and tracheostomy tray
  should be available and open, with appropriate
  personnel present should an emergency surgical
  airway be needed.

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• Postoperative management takes place in the
  intensive care unit and consists of continued
  observation and radiographic confirmation of
  tracheal tube placement. Tracheal extubation is
  usually attempted 48 to 72 hours
• later when a significant leak around the
  endotracheal tube is present and visual
  inspection of the larynx by flexible fiberoptic
  bronchoscopy confirms a reduction in swelling of
  the epiglottis and surrounding tissue.

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