Asthma Flashcards
What are the asthma stats?
What is it attributed to?
- One of the most common chronic conditions worldwide
- 300 million people globally
- Increasing in developing countries
- attributed to air polution
- genetic and environmental components
- strongly influenced by genetics
What does asthma do to the airways?
- Chronic inflammatory disorder of the airways characterized by increase responsieness of the tracheobronchial tree to a variety of stimuli
- Airways are enflamed, edemetous, and hypersensitive to irritants
- Severe cases will have airway wall thickening
- increased epithelium, submucosa, and smooth muscle tone
-
Reversible expiratory flow obstruction
- from hyperactivity and constriction
- degree varies over time; dynamic disease
What are the symptoms of Asthma?
- Wheezing
- breathlessness
- chest tightness
- cough (night and early am)
- tachypnea
- prolonged expiration phase
- fatigue
- variable airflow obstruction that is reversible
What are asthma triggers?
- allergens
- drugs
- aspirin
- NSAIDS
- infections
- exercise
- emotional stress
What is the pathophysiology of asthma?
What are the inflammatory mediators?
- Activation of inflammatory cascade releases mediators from mast cells that interact with receptors in bronchial wall and the autonomic nervous system to cause bronchoconstriction
- Inflammatory mediators:
- histamine
- leukotrienes
- prostaglandins
- substance P
What cells infiltrate the airway mucosa?
What does this cause?
- Cells:
- eosinophils
- neutrophils
- mast cells
- T lymphocytes
- leukotrienes
- basophils
- Causes bronchial edema and thickening of the airway
How is Asthma diagnosed?
- By looking at physical symptoms and pulmonary function tests
- baseline compared to after bronchodilator therapy
- if improvement is seen, asthma is indicated
What would you expect to see on the PFT of a pt with asthma?
- Decreased FEV1 and FEF25-75% (Maximum mid expiratory flow rate (MMEF))
- direct measurement of expiratory flow rate obstruction
- extent of decrease reflects the severity of expiratory obstruction
- During asthma attach FEV1 <35% and MMEF <20%
- Flow volume loop show a characteristic downward scooping of the expiratory limb
What is considered mild to moderate asthma?
what would an ABG look like?
- FEV1 <80%
- PaO2 and PaCO2 normal
What does severe asthma look like on PFTs?
ABG?
- FEV2 < 25%
- PaO2 may be < 60 mmHg and hypercarbia may develop
- respiratory muscle fatigue
What does PaCO2 usually do with a pt with asthma?
- PaCO2 often decreases as a result of hyperventilation, a neural reflex to bronchoconstriction
What would you expect a CXR to look like for a pt with asthma?
- hyperinflation of the lungs
- hilar vascular congestion from mucous plugging and pulm hypertension if disease is severe
What is the pharmacologic approach for pts with asthma?
How is this done?
- prophylactic approach; treat underlying inflammation
- as opposed to just treating bronchospasm
- Inhaled or systemic corticosteroids
- decreased bronchial mucosa inflammation and hyper-responsiveness
- advair
- Cromolyn
- Leukotriene inhibitors
- Methylxanthines- phosphodiesterase inhibitors
What are the rescue medications used for a severe asthma attack?
- Beta-2 adrenergic agonists- albuterol, terbutaline
- B2 receptor activation of adenylate cyclase with increased cAMP concentrations and bronchodilation
- SNS side effects: tachycardia, dysrhythmias, potassium shits
- Anticholinergic drugs- ipratropium
- blocks muscarinic recepors = bronchodilation
- less effective than B2 in asthmatics
- can prolong effects of B2 inhalors
What should we assess pre-induction for a patient with asthma?
- H&P
- breath sounds
- PFTs before and after bronchodilator therapy for major surgery
- FEV1/FVC should be > 70-80% expected or personal best prior to surgery
- FEV1/FVC <60% - risk for pulmonary morbidity
- CXR- looking for changes over time
- ABG- non necessary unless questionable oxygenation/ventilation prior to elective surgery
- Continue current asthma medications into peri-op period
Benzos vs opioids in a pt with asthma?
- benzos are a good choice b/c anxiety can precipitate bronchospasm
- opioids- consider resp depressant effect
How can you prevent bronchoconstriction perioperatively?
- Pre-op bronchodilators- albuterol before induction
- pre-op steroids
- If starting inhaled staroids, should start 48 hrs prior to surgery
- hydrocortisone 100 mg q 8 hours on day of surgery if FEV1 <80%
- may need stress dose steroids
What are the goals for GA?
Regional?
- General should be designed to:
- depress airway reflexes
- LMAs are better tolerated, less airway manipulations
- IV lidocaine 1-1.5 mg/kg, and opioids
- LTA- topical lidocaine
- propofol (no metabisulfites) and ketamine best
- avoid hyperactivity
- treat bronchoconstriction
- avoid histamine release
- depress airway reflexes
- consider regional, to avoid airway issues, but remember to avoid stressing them
What VA and NMB would you use for pts with asthma?
-
Sevo and halothane are less pungent; less coughing to trigger bronchospasm
- use high concentration >1.5 MAC for dilation and bronchial reflex inhibition
- need strong CV system for this
- Avoid NDMRs that release histamine
- atracurium
- mivacurium
- d-tubo
- Anticholinesterase:
- neostigmine ok if given with anticholinergic
Why would you not want to use thiopental (if it was available) in an asthmatic pt?
Whats the concern with propofol?
- releases histamine
- Propofol- generic has sulfites that can cause reaction
What is the induction drug of choice for the asthmatic pt?
- Ketamine for bronchodilator effects
- stimulates secretions, so give with anticholinergic
Which opioids should be avoided in asthmatics?
non opioid pain meds?
morphine
meperidine
nsaids
asa
Which VA can irritate the airway?
Isoflurane
Desflurane- really bad
How should you emerge a pt with asthma?
- goal for a smooth emergence
- Possibly extubate deep if appropriate
how can you treat intraoperative bronchospasm?
- attach albuterol to T-piece of ETT and give dose
How do you want to manage fluids in a pt with asthma?
liberal hydration to decrease viscosity of secretions
How do you want to ventilate an asthmatic patient?
- decreased RR 8-10 bpm
- need adequate exhalation times
- Prolong I:E ratio
- Increase TV to maintain normal PaCO2
- Avoid excessive peak airway pressures (>40 cmH2O)
What is the differential diagnosis of intraoperative wheezing?
- foreign body (gastric tube in lung)
- partially blocked/kinked ETT
- light anesthesia
- aspiration
- endobronchial intubation
- pneumothorax
- pulmonary embolus
- pulmonary edema
- acute exacerbation of asthma
What do you do if your pt bronchospasms during anesthesia?
- Administer 100% O2
- deepen the level of anesthesia with a VA or IV drug
- administer B2 agonist
- in severe cases administer epi IV
- infusion 2-8 mcg/min
- SQ 0.3-0.5 mg q 20-30 min
- consider IV corticosteroids
- 1-2 mg/kg of cortisol
- consider IV aminophylline
Would you take a pt who is actively wheezing to the OR?
NO!! You should avoid this at all costs!! Especially if the procedure is elective
