Transcript Anesthesia and pulmonary diseases

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 variables1=Body mass index (B)
2=Severity of airflow obstraction (0)
3=Functional dyspnea (D)
4=Exercise 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
(>44 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 negativepressure 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.
2.
3.
4.
5.
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With the acquired immunodeficiency syndrome epidemic,
tuberculosis is reemerging worldwide.
Multidrug resistant and extensively drug-resistant strains are
resistant to therapy and have increased virulence.
Symptoms include persistent cough, anorexia, weight loss, chest
pain, hemoptysis, and night sweats.
Anesthesiologists are at increased risk of nosocomial
tuberculosis.
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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