Post-Anesthesia Care Flashcards
Why is post-anesthetic care important?
About 50% of the anesthesia-related mortality happens in the post-anesthetic period
What are common post-operative respiratory complications?
Hypoxemia Hypoventilation Airway obstruction Regurgitation aspiration Pneumothorax
What are common post-operative complications resulting in poor recovery?
Dysphoria
Pain
Catastrophic injuries during recovery (+++ horses)
What are post-operative complications that can result in prolonged recovery?
Hypothermia
Residual effect of anesthetic drugs
What are some common post-operative complications?
Hyperthermia
CV complications
Myopathy/neuropathy
Worsening pre-existing conditions
Define hypoxia
Hypoxemia = PaO2 <80 mmHG
Mild 60-80 mmHg
Moderate 40-60 mmHg
Severe <40 mmHg
T or F: all hypoxic patients are also cyanotic
F; not always! - use pulse ox and/or ABG to rule out
Define cyanosis
Visible when concentration of deoxyHb > 5 g/dL
Reflects absolute concentration!
Cyanosis is more apparent in patients with high Hb vs those with anemia
Subjective, unreliable late indicator of hypoxemia
What is the difference b/t hypoxemia and hypoxia?
Hypoxemia = reduction below normal levels of oxygen in blood = low PaO2
Hypoxia = reduction below normal levels of oxygen in the tissues - leads to organ damage
*Hypoxemia can lead to hypoxia, but it is not the only cause of hypoxia?
What are the causes of hypoxemia?
Low FiO2
Hypoventilation
Ventilation to perfusion mismatch
AV shunt (anatomical)
What is the cause of hypoxia?
Insufficient DO2 = CO x CaO2
Related to the Hb concentration and saturated O2 concentration and the PaO2
Can I be hypoxic without being hypoxemic?
Yes, in cases that you have normal levels of O2 in the blood but for whatever reason it cannot reach your tissues e.g. thrombosis, ischemia
Why is it easy to become hypoxemic during the recovery period?
Most of our patients breath 100% FiO2 during anesthesia, but will only breathe 21% O2 in the recovery room air
Most drugs used during anesthesia or as analgesics/sedatives post operatively cause hypoventilation
What is atelectasis and what are some common causes?
Deflated alveoli
Common causes:
General anesthesia
Absorption - high FiO2
Compression - MM relaxation, external compression
Decreased surfactant - more relevant for long term ventilation
What is a situation you would have a V/Q mismatch?
High V/Q - alveolus is ventilated but not perfused - hypotension
Low V/Q - alveolus is perfused but not ventilated - atelectasis
Ideal situation - alveolus is ventilated AND perfused
Who has a higher risk of becoming hypoxemic?
Obese patients Intra-thoracic, abdominal sx Dorsal recumbency Pre-existing resp dz Long anesthetic procedures P requiring higher doses of opioids/sedative Painful animals Dysphoric animals
What are potential causes of airway obstruction post-operatively and where can it occur?
Edema and swelling caused by recumbency/irritation due to ET Obstruction can occur in: Nostril - phenylephrine spray Larynx Trachea Bronchi - mucus plug
Who is more at risk for a post-operative airway obstruction?
Obligate nasal breathers - horses, camelids, rabbits
Brachycephalics
Pre-existing resp conditions - tracheal collapse/bronchial dz
Tight bandage around neck
What are ways of detecting airway obstruction prior to extubation?
Incr resp effort
Thorax doesn’t expand
High PIP alarm on ventilator
Capnography - exclude disconnection or equipment dysfunction
Try to ventilate - feels like trying to ventilate a brick
Advanced resp monitors
*usually due to kinking or mucus plug obstructing lumen of ET
What are ways of detecting airway obstruction after extubation?
Increased insp effort Strider Thorax doesn’t expand Cannot feel air passing through nose *ALWAYS check that your patient is breathing normally after extubation
How do we deal with airway obstruction?
Early recognition
Try to establish cause
Can dog breath if you open its mouth —> nose
What happens if you try pulling tongue out and extending neck?
Is there a bandage? Too tight?
If in doubt, re-induce GA and incubate again
What are conditions that predispose brachycephalics to airway obstruction?
Stenotic nostrils Elongated soft palate Exerted saccules and tonsils Hypoplastic trachea Laryngeal collapse
What are tips to minimize risk of airway obstruction in brachycephalics?
Only extubation when they don’t tolerate tube anymore
Some need emergency BAS surgery after GA for a different procedure
Make sure you have drugs and airway equipment available before trying to extubate
Why is it especially bad if a horse gets an airway obstruction?
Horses can generate such a substantial negative pressure when trying to breath against an obstructed airway that they can get fulminating pulmonary edema
What predisposes horses to airway obstructions post-operatively?
They can only breathe through nose
If nostrils are edematous, they can obstruct
Can obstruct if they push nose against the wall as they wake up
Laryngeal paralysis is frequent
When they obstruct, they panic = risk for personnel!
How do you deal with an airway obstruction in a horse?
Can leave ET tube in during recovery - may kink or be bitten
Nasopharyngeal tubes can be placed if the obstruction is due to edematous nostrils
*regardless of timing of extubation, ALWAYS have drugs to induce GA readily available, ET tubes/mouth gag, tracheostomy kit ready
T or F: airway obstruction in alpacas is often “silent”
True; make sure to watch for movements of the thorax!
What are ways to monitor for airway obstruction in alpacas?
Use in phenylephrine prior to recovery
Nasopharyngeal tubes can be used
Extubate only when they are reactive and don’t tolerate it
Have drugs for induction/airways equipment ready
What is a special way to incubate nasal breathers like rabbits that are difficult to intubate?
Laryngeal masks (V-gel)
What mechanical error can potentially cause a pneumothorax?
Having a closed pop off valve during anesthesia can cause pneumothorax hours after the anesthesia is over
Why does regurgitation/aspiration occur peri-operatively?
Many anesthetic drugs cause nausea, vomiting, delayed gastric emptying, also impair swallowing reflexes - these can still be impaired even after extubating
Who is more at risk for regurgitation/aspiration?
GI surgery - foreign body, GDV Septic abdomen Hx of vomiting Megaesophagus Laryngeal paralysis Airway sx requiring unprotected airway Ruminants
How do you treat regurgitation/aspiration?
Expect it and be prepared
Admin gastro Protestants/antacids
Suction
Late extubation of patients at risk
What is dysphoria and what are some signs of it?
Profound state of unease or dissatisfaction accompanied by anxiety or agitation
Signs: whining, screaming, uncoordinated movements
*difficult to differentiate from pain
How do you differentiate painful patients from dysphoric patients?
Painful P:
Responds to palpation of sx site, seems aware, responds to admin of an opioid
Dysphoric P:
Doesn’t respond to anything in particular, seems out of it, often caused by opioid admin, can be tx with opioid antagonists - THESE REVERSE ANALGESIA TOO or sedatives/tranqs - ace/dexmedetomidine
T or F: dysphoria is a good reason to withhold administration of analgesics
False
Who is more prone to catastrophic injury during recovery?
Horses, large animals, wild animals
What 4 things can cause prolonged recovery?
Residual drug effect
Acid base/electrolyte abnormalities
Hypoxemia, hypercapnia
Hypothermia
What do you do when an animal is taking too long to recover?
Check the temp - use heating devices to tx hypothermia
Eval ventilation status- capnography (if still intubated), venous/arterial blood gas
Eval oxygenation - Pulse Ox/ arterial BG
Eval acid base/electrolyte status
What can we do to promote a smooth recovery in a horse?
Sedation - alpha2 agonists, ace
Good analgesia
Should lie down for at least 30-40 min after discontinuation of halogenate
Quiet recovery box - limit noises, low lighting/cover eyes
Assist recovery - ropes/pool, risk for personnel
What are some causes of peri-anesthetic hyperthermia?
Iatrogenic - overzealous use of heating devices Opioid-related Capture-related Exhausted CO2 adsorbent Malignant hyperthermia
How to treat peri-operative hyperthermia?
Turn off heating devices Incr fresh gas flow Check CO2 canister Is it cat/ferret that received opioids? Discontinue/reverse Initiate cooling process If you suspect MH - cooling + dantrolene
How do CV complications occur post operatively?
Effects of anesthetic drugs persist for hours after anesthesia
Patients are monitored thoroughly during anesthesia but not after
What can we do about CV complications?
If possible, maintain monitors connected until the patient is extubate/awake
Critically ill animals, or those that were unstable during anesthesia in post-anesthetic period - transfer to ICU
What are causes of myopathy/neuropathy post operatively?
Malposition during anesthesia
Compression of nerves
Hypoperfusion of mm
More at risk with large, heavy animals
How can we treat post operative myopathy/neuropathy?
Position animal carefully, use paddle surfaces
