Resp anes Flashcards
Preparation for anaesthesia for patints with resp problems
Identify problems preop
Stabilize the patient’s condition prior to anaesthesia and improve pulmonary function
Understand pathophysiology and chose anaesthetic protocol for the individual patient
Peri and intraop monitoring (SpO2, capnography)
Supportive care
Peri op supplemental O2
Positive pressure ventilation (PPV) during anaesthesia
Anti anxiety med
Pulse oximeter: how saturation relates to arterial PaO2
Saturation of 100% PaO2 100mmHg or more
Saturation of 95% PaO2 80mmHg
Saturation of 90% PaO2 60mmHg HYPOXEMIA !!
Saturation of 75% PaO2 40mmHg
Saturation of 50% PaO2 27mmHg
Normal SpO2: 95-100% (97-100% acceptable in surgery)
Normal paO2:80-100mmHg
Gums turn blue at 85-80%
What is preoxygenation
Administration of oxygen before induction of anaesthesia
Replaces alveolar nitrogen (79%) with oxygen
Create an intrapulmonary O2 reserve (FRC)
Hb fully saturated, dissolved O2 increases
Why preoxygenate dogs
DELAYS onset of hypoxemia during apnea/hypoventiatlion
Preoxygenation for 3 min
Without preoxygenation: hypoxemia occurs in <70 sec
With preoxygenation: apnea tolerance <298 sec
Ideally with a tight fitting mask
Avoid stress (agitation, struggling) → increase oxygen consumption
is flow by O2 helpful
Delays onset of hypoxemia??
Flow by pre oxygenation: hypoxemia occurs in <66sec
Mask pre oxygenation: apnea tolerance <187 sec
Preoxygenation tips
Size of mask - avoid superfluous dead space
Oxygen flow rate – avoid rebreathing
How long
3 min
FEO2 > 90% (fraction of expired oxygen)
Don’t stop during induction
Who benefits from preoxygenation
Important when difficult airway is anticipated - brachycephalics
Pregnant patients
Patients with increased intraabdominal pressure
Patients with cardio disease
Patients with resp disease
Critical ill patients
Obese patients
Use of anticholinergics in the preop period? Atropine, glycopyrrolate?
Use controversial
Laryngeal manipulation?
Can cause profound vagally mediated bradycardia
Brachycephalics: elevated vagal tone
Use as antisialogoues or to decrease respiratory tract secretions?
Generally not recommended
Change secretory composition: from watery fluid to thick mucous
Bronchodilation?
Tachycardia increases myocardial work and O2 demand
Sedation for patients with resp compromise
Sedation may adversely affect ability to breath but:
Clinical signs: aggravated by hyperventilation
Avoid: anxiety, excitement, physical exertion, hyperthermia
Increase in patient’s work of breathing will exacerbate negative pressure in upper airway
Pronounced negative pressure promotes inward collapse of airway
What is the bernoulli effect
Physical principle to explain airway collapse during hyperventilation
“Increase in gas velocity, which occurs when gasses traverse a constriction, lowers pressure at that point and promotes collapse”
Sedation for dyspneic patients
Low dose of sedatives/analgesic drugs will allow patient to breathe slowly and deeply
- Reduction in airflow turbulence and work of breathing
-Continuous monitoring during sedation
- Avoid drugs that induce vomiting and panting
Anxiolysis (pre or in hospital, slow onset time)
- Trazodone: 2-10 mg/kg (administered ideally prior to leaving home, continued during hospitalisation)
- Gabapentin 10-20 mg/kg
Sedation (in hospital)
- Butorphanol: 0.1-0.4mg/kg
- Acepromazine: 0.005-0.02mg/kg
- Dexmedetomidine: 1-2μg/kg
Avoid excessive sedation: may produce airway muscle relaxation and airway obstruction
Brachycephalic dogs
Risk of anesthesia related complications in brachycephalic dogs
Retrospective cohort study
Brachycephalic dogs more likely to have complications:
2.06 x perianesthetic period
1.57x intra-anesthetic period
4.33x post-anesthetic period
Brachycephalic obstructive airway syndrome (BOAS) is and caused by
Upper airway gas flow is restricted by:
- Stenotic nares
Hyperplastic soft tissue
Elongated, thick soft palate
Hypoplastic trachea
Everted laryngeal saccules
Oversized, elongated tongue
Prolonged obstruction
Excessive oropharyngeal soft tissue weakness → laryngeal collapse
Pulmonary hypertension (due chronic hypoxia)
Esophageal and gastrointestinal abnormalities:
Increased risks of Gastroesophageal reflux (GER) and regurgitation → aspiration, esophagitis and stricture formations
Prevalence for regurgitation: French bulldogs 93%, English bulldogs 58% and pugs 16%
BOAS–clinical signs worsen with:
Heat
Exercise
Stress/Anxiety
Panting
Reduce risk of GER and aspiration
Appropriate fasting
Pre-anesthetic treatment:
Omeprazole (1mg/kg): 4-24 h before induction
Maropitant prior to premedication (1 hour SC, 2 hours PO)
Prokinetics: Cisapride, metoclopramide?
If GER is observed:
Gently suction and lavage esophagus with water
Instill diluted bicarbonate
Recheck esophagus and oral cavity before recovery
Anticipated anesthetic complications with brachychephalics
Upper airway obstruction in perioperative period
Time between premedication and tracheal intubation
Tracheal extubation and full recovery
Prone to hyperthermia-panting is difficult and ineffective
Ocular care: higher incidence of corneal ulceration
BOAS premed/sedation
Sedation
Reduce anxiety
Facilitate IV catheter placement
Reduce dose of induction agent
Anesthetic sparing
Analgesia
No ”perfect” premedication/sedation protocol exists
Drug selection depends on temperament, severity of concurrent disease and procedure
What are hte effects of sedation
Improve ventilation by slowing inspiratory flows
Relaxation of oropharyngeal muscles → aggravation of obstruction
Panting
Vomiting
Excitement
Avoid drugs that induce profound sedation, vomiting panting and marked resp. depression
Continuous monitoring during sedation!
How do you induce a brachycephalic
Ensure IV access
Pre-oxygenate
Induction: Loss of protective airway reflexes → in total airway obstruction
Rapid acting induction protocol: to quickly establish airway
Have wide range of ET tube sizes ready
Gentle intubation with appropriately sized ET tube
Sometimes need to entrap epiglottis from soft palate
Recovering brachycephalics
High risk period
Position in sternal
Continuous O2 provision
Leave IV cath in place until fully recovered
Late extubation
In patients with laryngeal collapse- anticipate upper airway obstruction and have a plan ready before extubation
Have equipment/drugs available for reintubation
Problems in recovery for resp issues
Minor post extubation obstruction
Extend head and neck top open airway
Pull tongue rostrally
Open mouth: use gag if necessary, open jaw with bandage strips
Major obstruction
Re-Anesthetized and intubate of necessary
Place temp tracheostomy
Recovery: upper airway obstruction in cats
Position in sternal and extend neck and head
Gently pull tongue forward (if tolerated)
Administer O2
Try to inspect oral cavity
Mucus plug: suction
Laryngeal edema: corticosteroids (dexamethasone(0.2mg/kg))
What is a laryngeal spasm
Larynx must not be stimulated further
Avoid multiple attempts of intubation
Keep patient oxygented: facemask, supraglottic airway device (V-gel)
Optimize head and neck position
how do you treat a laryngeal spasm
Lidocaine spray?
Deppend anesthesia
Muscle relaxant: rocuronium (0.5-1mg/kg)
Consider tracheostomy
Dogs with laryngeal paralysis is and caused by
Anesthesia for diagnosis of laryngeal function
Anaesthetic drugs
Affect laryngeal activity
Can complicate diagnosis
Goal of anesthesia induction
Adequate anesthetic depth allow
Jaw relaxation to position laryngoscope and
Maitina intact laryngeal reflexes
Anesthesia for diagnosis for laryngeal function
Premed improves quality of laryngeal exam
Alfaxalone or propofol alpine are not reliable
Either alfaxalone or propofol can be used after ace/but or dexmed/but
Doxapram (0.5-2mg/kg IV)
- Resp stimulant
- Increases laryngeal motion in healthy dogs
- Produces passive paradoxical arytenoid motion in dogs with laryngeal paralysis
