Respiratory diseases and anesthesia Flashcards
What factors increase anesthesia risk with a respiratory tract infection?
- underlying resp disease
- smokers/second hand
- manipulation of airway (intubation vs lma)
- within 6 weeks of active infection
Intraoperative management of acute repirtory infection
- hydrate
- reduce secretions
- limit manulation
*prophylactic bronchodilators? Not established
Asthma is characterized by
REVERSIBLE expiratory airway obstruction
chronic airway inflammation increases resistance
bronchial hyperractiviity = bronchospasm
asthma anesthesia considerations
- deep anesthesia
- steroids before extubation
1 astham pathogenesis/cause
Atopy (allergies)
asthma diagnosis flow-volume loop
Flow volume loops show characteristic downward scooping of expiratory limb
Asthma diagnosis FEV1 (forced expiratory volume in 1 second) and MMEF (mid-expiratory flow rate)
direct measure of airflow obstruction
What helps determine asthma vs airway obstruction
where loop is flat helps determine where the obstruction is (inhaled or exhaled portion)
FRC in asthma
moderate - severe increased
TLC in asthma
remains unchanged
Diffusing capacity for CO and asthma
does not change
PaO2 and astham
mild asthma PaO2 is normal
Drug classes for asthma
- anti-inflammatory drugs (corticosteroids)
- Bronchodilators (beta agonsits and antocholinergics)
- Methylxanthines
In asthma, what indicates intubation?
PaCO2 > 50 despite aggressive anti-inflammatory and bronchodilator therapy - respiratory fatigue
Prior to surgery in asthmatic, what does optimization look like
- peak expiratory flow > 80% predicted
- absence of wehezes
Asthma PFTs prior to surgery: what predicts risk for perioperative complications?
- FEVV1 < 70% predicted
- FEV1/FVC ration less than 65%
Asthma induction
Propofol > etomidate
Ketamine = bronchodilation (but increases secretions, consider glycopyrolate)
Ventilator strategies in asthma
- LMA > ETT
- decrease inspiratory flow rate, longer exhalation
- humidification
- avoid histamine
- deep extubation/ lidocaine
Bronchospasm presentation
rapid increase in peak airway pressure and inability to ventilate (but consider other possibilities as cause)
bronchospasm treatment
- deepen anesthetic
- bronchodilator (albuterol)
- corticosteroid administration (hours)
FEV1 range
forced expiratory volume in one second
based on age and gender
normal is within 80% of predicted values
What is useful in distinguishing between restrictive and obstructive disesase
FEV1/FVC
should be greater than 0.7
less than 0.7 = obstruction
What is best for assessing small airway disease?
FEF 25-75
rate of flow occurring in forced expiration between 25-75% of flow
what is the most effort independent and reliable measurement of early obstruction?
FEF 25-75
FEV1 and FEV1/FVC - what indicates more sophisticated split lung function tests?
FEV1 less than 2 L and
FEV1/FVC less than 50%
In intrathoracic obstruction, the problem is
expiration
In extrathoracic obstructoin, the problem is
inpiration
Examples of intrathoracic obstruction
Tumors of lower trachea
tracheal malacia
tracheal strictures
examples of extrathoracic obstruction
tracheal tumors
subglottic stenosis
goiter
vocal cord paralysis
Dominant feature of COPD
progressive airflow obstruction, nonreversible
COPD diagnosis
chronic productive cough (predominantly chronic bronchitis)
progressive exercise limitations (dyspnea predominantly emphysema)
expiratory flow obstruction
RV and FRC in COPD
increased (gas is trapped)
COPD treatment
cessation of smoking and oxygen (if PaO2 < 55 mmHg) supplementation
COPD goal PaO2
60-80 mmhg
Predictors of postoperative pulmonary complications in COPD
-current smoker
-advanced pulmonary disease
-Poor nutritional status (low albumin <3.5 mg/dL)
Smoking cessation guidelines pre-op
6 week pre-op
GA irritation bronchi
Des most irritating
emergence in COPD
prolonged d/t secondary air trapping
FEV1/FVC and PaCO2 in COPD that may require postoperative ventilatory support
- FEV1/FVC less than 0.5
- PaCO2 > 50
Restrictive lung disease is characterized by
- decrease in ALL lung volumes
- decrease in lung compliance
- preservation of respiratory flow rates
Tidal volumes and respiratory rate in acute intrinsic restrictive
Low TV, increased RR
acute intrinsic restrictive plateau pressure
< 30 cm H2O
VC that indicates severe pulmonary dysfuntion
<15 mL/kg
most common complication of mediastinoscopy
hemorrhage followed by pnuemothorax
Pleural effusion
accumulation of fluid in the pleural space
Respiratory failure
RR
PaO2
PaCO2
A-a gradient
RR > 35 or <8
PaO2 <60% at 50% FiO2 or more (in absense of respiratory shunt)
PaCO2 > 55 at 50% FiO2 or more (in absence of respiratory compensation)
A-a gradient >450
Nitrous and closed pneumothorax
no (OK with functioning chest tube)
Pulmonary HTN diagnosis
PAP increased by 5-10 mmhg
PA systolic > 30 mmhg and PAP > 20
Agents and PVR
Ketamine increases PVR
anesthetic techniques for pulmonary hypertension
Nitric (NO) or IV prostacylcin therapy
factors that increase pul htn
- hypoxemia
- hypercapnia
- acidosis
- hypothermia
- hypervolemia
Cor pulmonale
PAH that has resulted in RV hypertrophy, dilation and cardiac decompression
leading cause: COPD
First sign of ARDS
arterial hypoxemia resistant to treatment with O2
ARDS diagnosis
PaO2/FiO2 ration < 200
normal is >500
ARDS ventilation
Add PEEP to keep PaO2 at least 60 with FiO2 less than 0.5
PaO2 in pulmonary embolism
decreased
Diagnosis of pulmonary embolism
Doppler- wheel mill murmer