The document discusses asthma as an inflammatory disorder causing airway obstruction and details its prevalence and medical implications, particularly in relation to anesthesia. It outlines classifications of asthma severity based on forced expiratory volume (FEV1) and provides guidelines for preoperative evaluation, drug therapy, and anesthetic management to minimize complications. Key treatment strategies include avoiding certain risk factors, using inhaled bronchodilators, and ensuring smooth anesthetic induction and emergence to prevent bronchospasm.

1. ASTHMA
KRNA PROGRAM 2006
Block 3
Tom Dainty, CRNA

2. ASTHMA
 Asthma is an inflammatory, hyperreactivity disorder
of the airways which results in bronchial constriction
and airway obstruction during an attack.
 Asthma is experienced by about 5-7% of the U.S.
population.
 There is a worldwide increase in the incidence of
asthma with resulting morbidity and mortality.

3. ASTHMA
 The hyperreactive tendency of asthmatic
airways may complicate the delivery of
general anesthesia.
 A patient presenting with airway obstruction
as a result of asthma will experience
wheezing, cough, and dyspnea which is
usually reversible.

4. ASTHMA
 The potential for the reversibility of
respiratory obstruction with asthma is what
differentiates asthma from the fixed
obstructive causes of chronic obstructive
pulmonary disease.

5. ASTHMA
 The manifestation of airway obstruction with
an asthma attack is the result of bronchial
smooth muscle constriction, airway mucosal
edema and increased secretions.
 Prevention and treatment of an asthma
attack will focus on these causative factors.

6. ASTHMA
 Mild forms of asthma may have minimal
effects on anesthetic outcome if managed
with care.
 Severe forms of asthma may develop into life
threatening events during episodes of
asthmatic crisis.

7. FORCED EXPIRATORY VOLUME
 Forced expiratory volume is the volume of air which
is expired over a period of time during the forced vital
capacity maneuver.
 Healthy patients can expire ¾ of their FVC within the
first second of the forced expiratory maneuver.
 The forced expiratory volume in 1 sec. (FEV1) is the
most reproducible test measurement for determining
asthma severity.

8. FEV1 IN RELATION TO THE SEVERITY
OF AN ASTHMA ATTACK
 FEV1 equal to or greater than 80% of the
FVC = no abnormalities
 FEV1 = or > than 70% = mild asthma
 FEV1 45-70% = moderate asthma
 FEV1 less than 50% = severe asthma
 FEV1 < 35% = status asthmaticus

9. CLINICAL CLASSIFICATIONS OF
ASTHMA
 Mild intermittent asthma – signs and
symptoms less than twice per week,
generally asymptomatic with normal
respiratory function between episodes,
exacerbations are usually brief but intensity
may vary, nighttime symptoms occur less
than twice per month, FEV1 is greater than or
equal to 80%

10. CLINICAL CLASSIFICATIONS OF
ASTHMA
 Mild persistent asthma – signs and
symptoms more than twice per week but less
than once per day, episodes may affect
activity, nighttime symptoms occur more than
twice per month, FEV1 greater than or equal
to 80%

11. CLINICAL CLASSIFICATIONS OF
ASTHMA
 Moderate persistent asthma – daily
symptoms, daily use of short acting beta 2
agonist inhaler, episodes affect activity twice
a week and may last for days, nighttime
symptoms occur more than once per week,
FEV1 60-80%

12. CLINICAL CLASSIFICATIONS OF
ASTHMA
 Severe persistent asthma – continuous signs
and symptoms, frequent episodes, frequent
nighttime symptoms, limited physical activity,
FEV1 less than 60%

13. ASTHMA
 It will be very helpful to identify the exacerbating
circumstances of asthmatic symptoms during a
preoperative interview.
 Many patients are unable to identify exact causative
factors but others may relate attacks to upper
respiratory infections, environmental sources, or
psychological events which should be ruled out or
eliminated prior to the delivery of an anesthetic.

15. ASTHMA
 Preoperative evaluation of asthma characteristics should
include :
 Age of onset
 Known triggering agents or events
 Hospitalization history for asthma
 Known allergies
 Cough
 Sputum production
 Previous anesthetic history
 Current medications

16. ASTHMA
Avoiding elective surgery during
episodes of upper respiratory
infection in an asthmatic patient may
prevent intraoperative and
postoperative respiratory complications.

17. ASTHMA
Hyperreactivity of the airway may exist for
three to six weeks following an upper
respiratory infection in an asthmatic patient.
The use of histamine releasing drugs
should be avoided in asthmatic patients.

18. ASTHMA
 Diphenhydramine may be coadministered
with H2 blockers to help prevent H1 mediated
bronchoconstriction.
 Anticholinergics, inhaled, will prevent vagally
stimulated bronchospasm but parenteral(IV)
administration will cause an increased
viscosity of secretions(dry mouth).

19. ASTHMA DRUG THERAPY
 Inhaled beta2 agonists, by metered-dose
inhaler, are the first line selection
bronchodilators. (albuterol, salmeterol)
 Beta2 agonist should be administered
preoperatively and be available for
intraoperative administration.

20. ASTHMA DRUG THERAPY
 Vagal stimulation causes an increase in
intracellular cyclic guanosine
monophosphate (cGMP) which is responsible
for bronchoconstriction.
 Anticholinergics block formation of cGMP,
therefore promote bronchodilation.

21. ASTHMA DRUG THERAPY
 Ipratropium bromide (Atrovent) inhaler,
blocks cGMP without the undesirable drying
effect which parenteral anticholinergics
produce.
 Glycopyrrolate or atropine 0.2-0.8mg may be
administered by nebulizer.

22. ASTHMA DRUG THERAPY
Inhaled anti-inflammatory drugs are
often used as a component of chronic
therapy.
Inhaled metered-dose
corticosteroids help decrease airway
inflammation.

23. STATUS ASTHMATICUS
 Status asthmaticus is defined as unresolving
bronchospasm that, despite initial treatment,
is considered life threatening.
 PaCO2 which is high indicates poor
exchange of carbon dioxide and indicates
that respiratory failure is worsening.

24. STATUS ASMATICUS
 Lung function is greatly reduced. If
measured, FEV1 will be less than 25% of
normal.
 Impending respiratory failure will require
tracheal intubation and mechanical
ventilation.

25. TREATMENT OF STATUS ASMATICUS
 Metered-dose beta2 agonist Q 15-20 min.
 Intravenous corticosteroids – may take up to 12 hr.
for effect.
 Supplemental oxygen
 Consider intubation and mechanical ventilation if
PaCO2 is greater than 50mmHg
 General anesthesia with volatile anesthetic as last
resort.

26. ANESTHETIC MANAGEMENT OF
ASTHMATIC PATIENT
 Airway manipulation can be avoided by
implementing regional anesthesia.
 If general anesthesia is required, stimulation of the
airway should be minimized to avoid bronchospasm.
 The patient should continue asthma drug therapy
preoperatively.
 Avoid the use of any histamine releasing drugs
such as curare, atracurium, mivacurium,
morphine and meperidine.

27. ANESTHETIC MANAGEMENT
 Propofol is a good choice for intravenous induction.
The bronchodilating effect of ketamine makes it an
acceptable alternative.
 Intravenous lidocaine 1.5mg/kg is helpful in blunting
laryngeal reflexes.
 Increased depth of anesthesia should be achieved
with an inhalation agent, to further reduce airway
reflexes, before laryngoscopy.

28. ANESTHETIC MANAGEMENT
 Mechanical ventilation should be provided with a
slow rate at tidal volumes of 10ml/kg or less to allow
optimal gas exchange.
 A relatively fast inspiratory flow rate with a
prolonged expiratory phase will help prevent air
trapping.
 Adequate hydration with intravenous fluids will
reduce secretion viscosity.

29. ANESTHETIC MANAGEMENT
 Intraoperative bronchospasm, indicated by
wheezing and increased peak airway
pressures, should be treated with metered-
dose inhaled beta2 agonist and by increasing
inhalation agent concentration.
 Other causes of increased peak pressures
should also be considered.

30. ANESTHETIC MANAGEMENT
 Other potential causes of increased peak airway
pressure include :
- Inadequate depth of anesthesia
- Obstruction of ET tube by secretions, kinking of the
tube or overinflation of the tube cuff.
- Endobronchial intubation
- Aspiration
- Pulmonary edema or embolus
- Pneumothorax

31. ANESTHETIC MANAGEMENT
 Emergence should also involve minimal airway
manipulation.
 Intravenous lidocaine will blunt reflexes. Some
clinicians incorporate a lidocaine infusion (1-2
mg/min) during emergence to blunt reflexes.
 If possible, extubation while the patient is deeply
anesthetized may reduce the incidence of
bronchospasm.

32. ANESTHETIC MANAGEMENT
 Metered-dose beta2 agonist may be delivered
via the endotracheal tube before emergence.
(carrier gas used in inhalers may interfere
with mass spectrometer readings)
 Reversal of nodepolarizing neuromuscular
blocking agents with an anticholinesterase will
not induce bronchospasm if preceded by the
appropriate dose of anticholinergic.

33. ANESTHETIC MANAGEMENT
 Management of general anesthesia for an
asthmatic patient should focus on smooth
induction and emergence to avoid triggering
bronchospasm.