Respiratory Complications Flashcards by Giselle Carter

when can respiratory complications occur

at any stage in the anesthesia process:
- sedation
- induction/intubation
- maintenance
- recovery
- post-anesthetic period

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what is the best thing do to to prevent respiratory complications

be prepared! know common species/breeds, procedures, conditions, medications and positioning that leads to respiratory complications

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what is the most common cause of respiratory complications in anesthesia and why

hypoventilation - because of the drugs we use

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what are the 6 common respiratory complications during anesthesia

airway obstruction
tension pneumothorax
hypoxemia
hypoventilation
hyperventilation
apnea

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what does an oxygen saturation curve look at (x axis and y axis)

x: PaO2 (mmHg O2 in blood)

y: SpO2/SaO2 (% of Hb with O2)

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what is relative (mild), absolute (moderate) and absolute (severe) hypoxemia (give both SpO2 and PaO2)

Relative: <80 mmHg / SpO2 <95%

Absolute:
Moderate <60 mmHg / SpO2 <90%
Severe <40-45 mmHg / SpO2 <80%

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what delineates cyanosis

5.0 g/dL of deoxyhemoglobin or more (lower if anemic)

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what SpO2 does cyanosis correspond to if the Hb is normal

<85%

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what is the FiO2 of room air vs the FiO2 of inspired air during anesthesia? what are the implications?

FiO2 room air: 21%
FiO2 during anesthesia: 100%

During anesthesia, the PaO2 is 663 mmHg (HUGE O2 reserve)

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T/F SpO2 is a limited value when FiO2 = 0.21

F; SpO2 a limited value when FiO2 = 1 (i.e during anesthesia)

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what animal is the exception to the rule that most animals will not get hypoxemic during anesthesia

horses (due to their weight)

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what are 5 causes of hypoxemia during anesthesia

V/Q mismatch: atelectasis, pulmonary edema, thromboembolism, asthma…
R-L shunt: intracardiac or intrapulmonary
diffusion impairment (pneumonia, interstitial lung disease)
severe hypoventilation
decreased FiO2

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how do we treat hypoxemia (6)

Treat the underlying problem
- increase FiO2, check O2 source
- lung re-expansion, reposition
- bronchodilators
- support and optimize ventilation
- diuretics
- surgical correction if needed

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when do we want to pay special attention for hypoxemia

1) induction (pre-oxygenate)
2) recovery (switching back to room air)

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what is the definition of apnea

> 1 min without spontaneous breathing

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what are some causes of apnea (6)

after induction (rapid high doses of propofol, alfaxalone, thiopental)
excessive depth (1.5-3x MAC) or additional drug administration (opioids)
hypocarbia
airway obstruction
inability to ventilate
cardiopulmonary arrest

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what is the best prevention for apnea

pre-oxygenate the animal: increases the O2 reserve and therefore gives more time for you to correct the apnea without the patient becoming hypoxemic

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what MUST you have to diagnose hypoventilation

a CO2 monitor

by definition, what is hypoventilation

insufficient ventilation leading to hypercapnia (PaCO2 > 50-55 mmHg)

what is normal ETCO2 relative to PaCO2

ETCO2 usually 3-5 mmHg less than PaCO2

what causes hypoventilation

decrease in tidal volume
decrease in respiratory rate
increase in dead space
combination of the above

what are the physiological effects of hypoventilation (hypercapnia) (6)

stimulates respiratory drive
respiratory acidosis
increase cerebral blood flow
CNS depression
sympathetic stimulation (increase HR and BP)
hypoxemia

why does severe hypercapnia lead to hypoxemia

space-occupying (displacement of O2)

what are some causes of hypoventilation/hypercapnia during anesthesia

anesthetic drugs
pre-existing conditions
positioning
equipment

what are some pre-existing conditions that can cause hypoventilation/hypercapnia during anesthesia

- age - hyperthermia - obesity - neurologic disorders - pathologies of thoracic wall or lungs

what are equipment related causes of hypoventilation/hypercapnia

- increased dead space - increased work of breathing (tube too small) - CO2 rebreathing (low FGF, exhausted soda lime, unidirectional valves faulty)

why might laparoscopy be a risk for hypercapnia

absorption of the CO2 used to distend the abdomen for the procedure

how do we treat hypoventilation/hypercapnia

Treat the underlying cause! - be aware of conditions - monitor ETCO2 or PaCO2 - check the patient for depth - correct body temperature - check equipment - support ventilation as needed

what is hyperventilation and the consequences

increased respiratory rate leading to hypocapnia and respiratory alkalosis

what are some causes of hyperventilation

- light plane of anesthesia/nocicipetion - hypercapnia - hypoxemia - metabolic acidosis (respiratory compensation)

when does airway obstruction most commonly occur

premedication and recovery

what is the difference between partial and total airway obstruction

partial: increased work of breathing total: inability to move air

what are some causes of airway obstruction

- anatomy (brachycephalics) - underlying upper/lower airway disease - airway swelling - aspiration of foreign material - external pressure - equipment problems or errors

what are the ways to diagnose airway obstruction

- paradoxic breathing - generating high pressure when trying to ventilate - rebreathing bag not moving - capnograph wave abnormal or gone - prolonged inspiratory time - hypoxemia and/or cyanosis

what is paradoxic breathing characterized by

- thoracic wall sucks inward - abdominal wall expands - neck flexed - stridor - open mouth breathing - nostril flare

why are brachycephalic breeds predisposed to airway obstruction (what are the anatomical features)

- stenotic nares - elongated soft palate - everted saccules - hypoplastic trachea

what indicates lower airway obstruction on a capnograph

shark fin: tells you increased effort at start of expiration

how should you treat bronchospasm to prevent airway obstruction

bronchodilators, epinephrine, antihistamines

how should you treat upper airway obstruction (prevention)

- topical anesthetic - small tube size - be ready to intubate - pre-oxygenate

how do you prevent airway collapse from airway inflammation

- corticosteroids - vasoconstrictors - dextrose 50% locally

how do you treat airway obstruction: - at induction - intra-op - recovery

At induction: - suction - tracheostomy - get airway Intra-op: - check patient and equipment quickly - manually ventilate to assess - suction tube, change if needed Recovery: - extend head, pull out tongue - re-intubate if necessary

what is a tension pneumothorax

life-threatening emergency in which air accumulates under pressure, compressing the lungs and venous return

how do we diagnose tension pneumothorax

- increased respiratory effort - lack of lung sounds - resistance to ventilation - capnograph dissapears - cardiac arrest

how do we treat tension pneumothorax

- tap chest - chest tube - suction