ASTHMA Flashcards
what is asthma
chronic disease consisting of:
- chronic airway inflammation characterized by increased responsiveness of the tracheobronchial tree to a variety of stimuli
- airway wall thickening (increased epithelium, increased submucosa, increased smooth muscle)
- reversible expiratory flow obstruction (bronchial hyperactivity)
- degree of expiratory airflow obstruction is dynamic
s/s of asthma
episodic recurrent episodes of:
- wheezing
- breathlessness
- chest tightness
- cough (night & early am)
- variable, REVERSIBLE outflow obstruction
- tachypnea
- prolonged expiratory phase
- fatigue
pathophysiology of asthma
chemical mediators released from mast cells interact w/ ANS to cause bronchoconstriction
- eosinophils
- mast cells
- neutrophils
- macrophages
- basophils
- T lymphocytes
- other probable: cytokines, interleukins, arachidonic acid metabolites, kinins, histamine, adenosine, PAF
PFT & lung volume alterations w/ asthma
- decreased FEV1 & FEF25-75 (aka MMEF)
- during acute attack: FEV1 <35% & MMEF <20%
- flow-volume loop = downward scooping of expiratory limb
ABG alterations w/ asthma
- mild-moderate (FEV>50%) = PaO2 & PaCO2 normal
- PaCO2 is actually often decreased 2/2 hyperventilation as a neural reflex to bronchoconstriction
- severe (FEV1 <25%) & resp muscle fatigue = PaO2<60 & hypercarbia may develop
CXR findings in asthma
hyperinflation of the lungs (outflow obstruction)
prophylactic management of asthma
- inhaled/systemic corticosteroids
- cromolyn
- leukotriene inhibitors
- methylxanthines (phosphodiesterase inhibitors)
rescue management of asthma
BRONCHODILATORS B2 agonists (albuterol, terbutaline) - B2 activation = increased cAMP = bronchodilation - AE = tachycardia, dysrhythmias, K+ shifts
anticholinergic drugs (ipratropium)
- mAChR blockage = bronchodilation
- less effective than B2
preinduction assessment & management of the asthma patient
assess
- breath sounds
- PFTs before & after bronchodilator therapy for major elective operations (FEV1/FVC should be >70-80%; <50% = severe)
- CXR
- ABG if questionable oxygenation/ventilation
tx
- benzos (anxiety can precipitate bronchospasm)
- opioids (consider resp depressant effect)
- H2 antagonist +/- (unopposed H1 receptors = bronchoconstriction)
- continue current asthma meds
periop prophylaxis of bronchoconstriction in the asthma patient
preop bronchodilators (albuterol prior to induction)
preop steroids
- inhaled start 48hrs preop
- IV: hydrocort 100mg Q8hrs if FEV1<80%
general considerations of anesthetic management of the asthma patient
- consider regional
- if GA: depress airway reflexes, avoid hyperactivity, treat bronchoconstriction, avoid histamine release
- adequately hydrate to decrease secretion viscosity
how to blunt airway reflexes & bronchoconstriction during airway instrumentation?
avoid it = regional
- propofol & ketamine for induction (ketamine increases secretions though)
- avoid drugs w/ metabisulfites
- opioid
- consider lidocaine 1.5mg/kg IV
- consider intratracheal lidocaine (LTA)
good choices for induction & maintenence in the asthmatic patient
induction:
- ketamine bronchodilates, but increases secretions
- etomidate, propofol (avoid generic propofol containing sulfites)
maintenance:
high [ ] volatile >1.5MAC (bronchodilation)
- sevo, halothane (less pungent = no iso/des!)
avoid NDNMB that release histamine (atra, miva, D-tubo)
anticholinesterase drugs
- ok if given w/ anticholinergic
emergence & extubation of asthmatic patients
smooth! ETT promotes reflex bronchoconstriction & airway resistance
- deep extubation (as appropriate) and/or lidocaine 1-3mg/kg IV
vent management of asthmatic patients
- decrease rr 8-10
- prolong I:E ratio
- increase Tv to maintain normal PaCO2
- keep PIP<40cmH2O
