1. ANESTHETIC PROBLEMS AND EMERGENCIES
CHAPTER 12
Every anesthetic procedure has the potential to cause death of the animal

2. Emergencies are uncommon and the overwhelming majority of patients recover from anesthesia with no ill lasting effects

3. WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?
1. HUMAN ERROR!

4. HUMAN ERROR
FAILURE TO OBTAIN AN ADEQUATE HISTORY OR PHYSICAL EXAMINATION ON THE PATIENT.
*Ideally, every patient scheduled for anesthesia should have a complete physical examination, and a thorough history should be obtained with the owner present.
Less than ideal circumstances are common:
Owner drops patient off in a hurry
Patient brought in by neighbor or friend
Receptionist takes the history
Physical exam is cursory or omitted
HISTORY?
PHYSICAL?

5. HUMAN ERROR
LACK OF FAMILIARITY WITH THE ANESTHETIC MACHINE OR DRUGS USED
The confident, knowledgeable, experienced
RVT!
The not so confident kennel worker who was
asked to assist in surgery today.

6. HUMAN ERROR INCORRECT ADMINISTRATION OF DRUGS INACCURATE WEIGHT
MATHEMATICAL ERRORS
USE OF WRONG MEDICATION
*Be aware of medications that come in different concentrations
ADMINISTRATION OF MEDS BY INCORRECT ROUTE
*knowledge of pharmacology
*drugs with narrow margin of safety
CONFUSION BETWEEN SYRINGES
*ALWAYS LABEL SYRINGES
USE OF INAPPROPRIATE SYRINGE SIZE

7. HUMAN ERROR PRESSURES AND DISTRACTIONS Feeling hurried or rushed
Distraction because of ineffective multi-tasking
Fatigue
Inattentiveness
Be proactive, rather than reactive!
Recognize early signs of trouble
Pay attention to patient and machines

8. WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?
2. EQUIPMENT FAILURE
*In many cases the failure of the machine is in fact a failure of the operator.

9. EQUIPMENT FAILURE CO2 ABSORBER EXHAUSTION
*In re-breathing systems, if CO2 is not removed from the circuit, the patient will experience hypercapnia.
* In a non re-breathing system, if the gas flow is too low, there may also be a significant re-breathing of expired gases.
↑ CO2 = Tachypnea, tachycardia, brick red mucous membranes, cardiac arrhythmias, respiratory acidosis
Human error!

10. EQUIPMENT FAILURE INSUFFICIENT O2 FLOW
You will need to check both the flowmeter and the oxygen tank pressure gauge.
Oxygen tank runs out
Hose becomes disconnected
Obstruction or leak occurs
*If the oxygen flow stops while the patient is hooked up to a non re-breathing system, the anesthetist should disconnect the hose from the Endotracheal tube, allowing the patient to breathe room air.
If a re-breathing (circle) system is being used, the patient can remain connected for a short period of time, provided the reservoir bag remains inflated.
Human Error

11. EQUIPMENT FAILURE ANESTHETIC MACHINE MISASSEMBLED
Take time to learn and follow the direction and path of gas flow within the machine. Every time a connection is added or removed, the anesthetist should ensure that the correct pattern of flow is maintained and that all connections are secure.
**Soda-Lyme container main leak

12. EQUIPMENT FAILURE ENDOTRACHEAL TUBE PROBLEMS BLOCKED TUBES
Twisting or kinking of the tube (inappropriate positioning)
Accumulation of material such as blood, saliva, excess lubricant
Tube advanced too far into a bronchus
CHECK TUBE FUNCTION:
BAG the patient – watch for chest rising
Disconnect the patient – feel for air coming out of the tube when the patient’s chest is compressed
If an accumulation of material is causing the obstruction, it may be helpful to suction with a syringe through a red-rubber catheter or feeding tube.

13. EQUIPMENT FAILURE VAPORIZER PROBLEMS Wrong anesthetic in the vaporizer
Vaporizer is empty
Do not tip the vaporizer – could result in leakage into the oxygen bypass
Vaporizer dial may be jammed
Don’t overfill the vaporizer

14. EQUIPMENT FAILURE POP-OFF VALVE PROBLEMS
The pop-off valve is inadvertently left closed
Closed pop-off valve →pressure rises in the circuit →reservoir bag expands, as well as the patient’s lungs →exhalation is prevented
*This can lead to decreased cardiac output, low blood pressure, and death.
If pressure rises in the circuit and the bag is full and tight, the anesthetist should attempt to open the pop-off valve and/or decrease the oxygen flow rate.

15. WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?
3. ANESTHETIC AGENTS
Every injectable or inhalation agent has the potential to harm a patient and, in some cases, cause death. Review the description of the pharmacologic and physiologic effects of pre-anesthetic and general anesthetic agents in chapters 1 and 3.

16. WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?
4. PATIENT FACTORS
pre-operative status
age
concurrent disease
breed

17. PATIENT FACTORS GERIATRIC PATIENTS (75% of life expectancy)
POTENTIAL PROBLEMS
Reduced organ function- liver, kidney, heart
Poor response to stress
At risk for degenerative disorders- diabetes, CHF, cancer
Increased risk for hypothermia and overhydration
Prolonged recovery

18. Geriatric Patients solutions
POTENTIAL SOLUTIONS
Reduce anesthetic dosages
Increase preanesthetic blood work from mini to a general profile, include u/a, x-rays, ECG if needed
Allow a longer time for response to drugs
Reduce fluid rate
Keep patient warm
Choose anesthetic agents with minimal CV effects
Pre-oxygenate

19. PATIENT FACTORS PEDIATRIC PATIENTS (<3 months) POTENTIAL PROBLEMS
Increased risk for hypothermia and overhydration
Increased risk of hypoglycemia, hypotension, Bradycardia
Inefficient excretion of drugs-reduced kidney and liver function
Difficult intubation
Difficult IV cath placement
POTENTIAL SOLUTIONS
Be proactive about heat preservation
Avoid prolonged fasting (+/- 5% dextrose administration)
Reduce anesthetic dosages
Use a gram scale to weigh
Use inhalant anesthetics

20. PATIENT FACTORS BRACHYCEPHALIC DOGS POTENTIAL PROBLEMS
Conformational tendency toward airway obstruction
Elongated soft palate
Small nasal openings
Hypoplastic trachea
Difficult to intubate
Abnormally high vagal tone
Bradycardia
POTENTIAL SOLUTIONS
Use an anticholinergic
Pre-oxygenate
Induce rapidly with IV agents
Delay extubation
Close monitoring during recovery- recover in a excitement free area

21. PATIENT FACTORS SIGHTHOUNDS POTENTIAL PROBLEMS POTENTIAL SOLUTIONS
Increased sensitivity to barbiturates
Lack of body fat for redistribution/elimination
of the drug
POTENTIAL SOLUTIONS
Use alternative agents

22. PATIENT FACTORS OBESE PATIENTS POTENTIAL PROBLEMS POTENTIAL SOLUTIONS
Accurate dosing is difficult- lower dose /kg
Poor distribution of drugs
Respiratory difficulty- shallow rapid respirations during anesthesia
POTENTIAL SOLUTIONS
Dose according to ideal weight
Pre-oxygenate
Induce rapidly
Delay extubation
Close monitoring during recovery

23. PATIENT FACTORS CESAREAN PATIENTS- normally an emergency
POTENTIAL PROBLEMS
DAM: increased workload to heart
Respiration compromised
Increased risk of hemorrhage- shock/hypotension
Increased risk of vomiting/regurgitation- not normally fasted
Hypoxemia
Hypercarbia
Acid/base imbalance
Tissue trauma
Cardiac arrhythmias
OFFSPRING: susceptibility to the effects of the anesthetic agents (reduced Cardio and Respiratory function)

24. Cesarean patients POTENTIAL SOLUTIONS DAM: IV fluids
Clip patient before induction, in lateral recumbency
Pre-oxygenate
Reduce anesthetic dosages
OFFSPRING: use doxapram and/or atropine
aspirate fluids from mouth
Administer oxygen via face mask, intubate with 18 or 16g IVC
Keep warm
Encourage nursing

25. Patient Factors TRAUMA PATIENTS POTENTIAL PROBLEMS POTENTIAL SOLUTIONS
Respiratory distress common- decrease in tidal volume, increase in CO2
Cardiac arrhythmias
Shock and hemorrhage- hypotension
Internal injuries
POTENTIAL SOLUTIONS
Stabilize patient if possible
Obtain chest rads, ECG
Check for other concurrent injuries

26. Anesthetic Problems and Emergencies: Patient Factors
Change in blood pressure
Resulting from a change in cardiac output or vascular tone
Anesthetic depth will affect both parameters
Hypotension → decreased tissue perfusion → tissue hypoxia/anoxia → anaerobic glycolysis → lactic acid production → acid/base imbalance
Monitor blood pressure closely
Doppler or oscillometric methods
Digital pulse palpation
Capillary refill time

27. TREATMENT OF HYPOTENSION
REDUCE ANESTHETIC DEPTH
PRESERVE WARMTH
FLUID THERAPY- SHOCK RATE
ADMINISTRATION OF EMERGENCY DRUGS:
Corticosteroids
Sodium bicarbonate
Cardiac inotropes (dopamine, dobutamine, ephedrine)

28. Fluid Therapy for Hypotension
Crystalloid fluid administration
May have to deliver small boluses for rapid therapy
Crystalloid fluids stay in intravascular space <2 hours
Watch for fluid overload, especially in cats
Monitor heart rate, blood pressure, mucous membrane color, and capillary refill time

29. Fluid Therapy for Hypotension (Cont’d)
Colloid fluid administration
Helpful if blood pressure can’t be maintained
Remain in the intravascular space longer than crystalloids
Will increase colloidal osmotic pressure and help stabilize blood pressure
Given in smaller volume in conjunction with crystalloids
Hetastarch, Dextran 40 or 70, 10% Pentastarch, plasma, whole blood

30. Respiratory problems in the trauma patient
Direct trauma to the chest leading to lung collapse or failure of alveolar gas exchange
Must remove air/fluid from chest cavity prior to anesthesia
Deliver supplemental oxygen
Oxygen delivery methods
Flow-by-oxygen
Nasal catheters
Oxygen collars

32. Thoracocentesis (Chest Tap)
To relieve pneumothorax or pleural effusion from chest cavity
Performed by veterinarian Prepped by veterinary technician
Temporary bandage over chest wound
Place animal in sternal recumbency or standing position
Shave lateral chest wall between the 7th and 9th intercostal spaces caudal to point of the elbow
Aseptically prepare 4 cm × 4 cm area
Prepare a 20- to 22-gauge, 1- to 1½-inch catheter with a three-way stopcock and large syringe
video

33. PATIENT FACTORS CARDIOVASCULAR DISEASE POTENTIAL PROBLEMS
Circulation compromised
Pulmonary edema common
Increased tendency to develop arrhythmias and tachycardia
POTENTIAL SOLUTIONS
Alleviate pulmonary edema (diuretics)
Pre-oxygenate
Avoid agents that may cause arrhythmias
Prevent overhydration- cut fluids in 1/2

34. Preexisting cardiovascular disease
Anemia
Shock
Cardiomyopathy (primary or secondary)
Congestive heart disease (mitral valve insufficiency)
Heartworm disease
Coexisting imbalances (e.g., hypoxia, hypercapnia, electrolyte imbalances)

35. Bradycardia Most common cardiac anesthetic problem
Caused by preanesthetic or anesthetic drugs
Force of cardiac contraction may also be decreased
Blood return to the heart may be decreased (preload)
Treat with drugs or adjustment of anesthetic depth

36. Cardiac arrhythmias
Caused by anoxia/hypercarbia, poor tissue perfusion, acid/base imbalance, myocardial damage
Difficult to detect on physical examination; may find dropped beats
Diagnose with ECG and report immediately to veterinarian who will determine the treatment required
Concurrent pulmonary disease is sometimes seen

37. PATIENT FACTORS RESPIRATORY DISEASE POTENTIAL PROBLEMS
Poor oxygenation of tissues
Patient may be anxious and difficult to restrain
Increased risk of respiratory arrest
POTENTIAL SOLUTIONS
Avoid unnecessary handling
Pre-oxygenate
Induce with injectable agents
Intubate rapidly; control ventilation
Monitory closely during recovery

38. Respiratory disease Caused by: Clinical signs Tachypnea Dyspnea
Pleural effusion Diaphragmatic hernia
Pneumothorax Pneumonia
Tracheal collapse Pulmonary edema
Clinical signs
Tachypnea
Dyspnea
Cyanosis

39. Anesthetic considerations
VT is reduced and respiratory rate is decreased in most anesthetized animals
A decrease in VT will result in a decreased alveolar gas exchange
Lighten anesthesia as much as possible in a patient with respiratory disease
Provide intermittent ventilation
Evaluate oxygen-carrying capacity with PCV or pulse oximeter
Preoxygenation is necessary prior to induction

40. Diaphragmatic Hernia Dysnpnea- pre oxygenate Avoid head down positions
Intubate rapidly
“bagging” patient
Pay close attention to pulse ox, capnograph, and do a arterial blood gas if available.

42. PATIENT FACTORS HEPATIC DISEASE POTENTIAL PROBLEMS
Liver necessary for drug metabolism, blood clotting factors, plasma proteins, carbohydrate metabolism
Decreased synthesis of clotting factors
Possibly hypoproteinemic
Dehydration common
Anemic and/or icteric
Prolonged recovery
POTENTIAL SOLUTIONS
Pre-anesthetic blood work
Preanesthetic agents must be chosen with care
Use inhalant anesthetics
Close monitoring during recovery

43. PATIENT FACTORS RENAL DISEASE POTENTIAL PROBLEMS POTENTIAL SOLUTIONS
Delayed excretion of anesthetic agents
Electrolyte imbalances common
Dehydration may be present
POTENTIAL SOLUTIONS
Pre-anesthetic blood work
Rehydrate before surgery
Reduce anesthetic dosages
IV fluids

44. Renal disease
Kidneys maintain volume and electrolyte composition of body fluids
Renal excretion removes anesthetic agents and metabolites from the body
General anesthesia is associated with decreased blood flow to the kidneys
Diagnosis: urine specific gravity, BUN, creatinine
Offer water up to 1 hour prior to premedication
Correct dehydration prior to anesthesia

45. Anesthetic Problems and Emergencies: Patient Factors (Cont’d)
Urinary blockage
Clinical signs
Depression
Dehydration
Uremia
Acidosis
Hyperkalemia (can lead to cardiac arrest)
Inhalation agents are less hazardous for the patient

46. ANESTHETIC PROBLEMS AND EMERGENCIES
Anesthetic problems will inevitably occur at some
point in your career. No anesthetic experience is
the same, so beware of the false sense of security!

47. ANESTHETIC PROBLEMS AND EMERGENCIES
The Role of the Veterinary Technician in Emergency Care

48. ANIMALS THAT WILL NOT STAY ANESTHETIZED
Animals won’t stay anesthetized
Check vaporizer setting
Check level of anesthetic in the vaporizer
Proper ET tube placement or air leakage around it
Patient apnea
Shallow respirations
Proper assembly of anesthetic machine with tight connections
Adequate oxygen flow
Anesthetic machine/vaporizer is working properly
Agonal breathing vs. light plane breathing

49. ANIMALS THAT ARE TOO DEEPLY ANESTHETIZED
Animals are too deeply anesthetized
<6 bpm; shallow respirations, dyspnea
Pale/cyanotic mucous membranes
Capillary refill time >2 seconds
Bradycardia
Weak pulse; systolic blood pressure <80 mm Hg
Cardiac arrhythmias; irregular QRS complexes or VPCs
Hypothermia
Absent reflexes
Flaccid muscle tone
Dilated pupils

50. TREATING EXCESSIVE ANESTHETIC DEPTH
ADJUST THE VAPORIZER:
NOTIFY THE VETERINARIAN:
BAG THE ANIMAL
1. Close the pop-off valve
2. fill the reservoir bag with oxygen
3. gently squeeze the bag until the patient’s chest rises slightly (15-20 cm H2O)
4. Repeat until animal shows signs of recovery

51. PALE MUCOUS MEMBRANES Pale mucous membranes Preexisting conditions
Blood loss during surgery
Anesthetic agent that causes vasodilation and hypotension
Hypothermia
Pain

52. TREATMENT OF PALE MUCOUS MEMBRANES
Ascertain the animal’s anesthetic depth:
HR, RR, pulse quality, CRT
Consult the veterinarian
Fluids, blood transfusion

53. Anesthetic Problems and Emergencies (Cont’d)
Prolonged capillary refill time (>2 seconds)
Blood pressure cannot adequately perfuse superficial tissues
May result from conditions present prior to induction
May be secondary to blood loss during surgery
May be seen in animals in deep anesthesia

54. DYSPNEA AND/OR CYANOSIS
DYSPNEA: respiratory difficulty
CYANOSIS: bluish coloration of the mucous membranes indicating inadequate tissue oxygenation
Assessment
Respiratory character and volume
Depth of anesthesia
Associated with pain
Proper ET tube placement
ET tube blockage
Oxygen saturation
Arterial or end-tidal CO2

55. Treatment of cyanosis/dyspnea
1. Check O2 flow meter
2. Turn off vaporizer and begin to bag the patient (IPPV)
If the anesthetic machine is unavailable, an Ambu bag can be used to deliver room air
3. Reintubate if necessary
4. Continue until patient improves
5. Close monitoring to ensure that cardiac arrest does not occur
Radiographs and thoracocentesis might be needed

56. TACHYPNEA TACHYPNEA: rapid respirations CAUSES: Surgical stimulation
Commonly seen with opioid use
Associated with light anesthesia accompanied by tachycardia and spontaneous movement
May be seen in hyperthermic animals

57. TREATMENT OF TACHYPNEA
CHECK ANESTHETIC DEPTH
Is the animal too light?
CAPNOGRAPH READING
Obese patients
Assist or control ventilation

58. RESPIRATORY ARREST
Not all cases require immediate action by the anesthetist:
Cessation of respiratory efforts
Can lead to cardiac arrest
Temporary arrest
May follow injection of respiratory depressants or following a period of prolonged bagging
Evaluate other vital signs
HR/pulse quality:
MM:
ECG
Pulse oximeter reading:

59. Respiratory arrest (Cont’d)
True arrest
Requires immediate action
Can result from anesthetic overdose, cessation of oxygen flow, or preexisting respiratory disease
May be preceded by dyspnea or cyanosis and abnormal vital signs
May use Ambu bag, mouth-to-ET tube, or mouth-to-muzzle resuscitation

60. Use of an Ambu Bag

61. TREATMENT OF TRUE RESPIRATORY ARREST
1. NOTIFY THE VETERINARIAN
2. Turn off the vaporizer
3. Place ET tube if not already done
Emergency tracheotomy?
4.Monitor for cardiac arrest
5.Restore oxygen flow and begin bagging the patient
6. Continue bagging every 5 seconds until vital signs improve
7. Administer shock fluids
8. Preserve warmth

62. CARDIAC ARREST Cardiac arrest Some prior warning is usually present
No heartbeat is auscultated or palpated
Normal QRS complexes are absent
No arterial pulse and blood pressure <25 mm Hg
Gray or cyanotic mucous membranes
Widely dilated pupils, no corneal reflex
Agonal breathing
Some prior warning is usually present
Respiratory distress or arrest, cyanosis/dyspnea, prolonged capillary refill time, arrhythmia

63. CARDIAC ARREST - ABCDEF
There is a critical 4 MIN window to restore oxygen delivery to the brain!
Five people (ideal) involved
1 performs chest compressions
2 bags the animal
3 assesses the pulse during compressions and checks the pulse or ECG when compressions are stopped
4 draws up and administers drugs as per the veterinarian’s instructions
5 maintains a record of the patient’s status and resuscitative treatment

64. Anesthetic Problems and Emergencies
Cardiac arrest with CPCR
A = airway
B = breathing
C = circulation
D = drugs
E = ECG
Circulation is the most important step so the correct order is CABDE

65. CARDIAC ARREST - ABCDEF
AIRWAY and BREATHING;
IMMEDIATELY CALL FOR HELP, NOTE THE TIME!
An Endotracheal tube must be placed!
Begin bagging at 1 breath every seconds
Do not overinflate

66. CARDIAC ARREST - ABCDEF
CIRCULATION – cardiac compressions should be initiated
POSITIONING: right side down with feet toward the compressor
LARGE DOGS: The heel of the compressor’s hand should compress the chest against a firm object placed under the dog’s chest just behind the elbow. Also, dog can be placed in dorsal recumbency and compression applied to the caudal 1/3 of the sternum

67. CARDIAC ARREST - ABCDEF
Medium sized dogs: The chest is compressed between two hands, one underneath the chest and the other at the 5th intercostal space over the heart itself.
Small dogs or cats: compression applied using the thumb to compress the chest against the fingers of the same hand.

68. Circulation
Most important factor is return of spontaneous circulation (ROSC)
Cardiac compressions
Method depends on the size of the animal
Compress chest about 1/3 the diameter of the chest wall
1-2 compressions/second generates 100 bpm heart rate
Compressions manually force blood through the heart and into tissues
Each compression should produce a palpable femoral pulse

69. Circulation (Cont’d)
Bag the patient every seconds
Simultaneously with compressions
Some results should be seen within 2 minutes
Internal compressions may be necessary
Resuscitation is unlikely to be successful after 15 minutes
Once spontaneous cardiac contractions are established, continue bagging until spontaneous breathing is established (several hours)

70. These patients are not on their right side- boooo

71. CARDIAC ARREST - ABCDEF
Drugs
Veterinarian authorizes dosage, route, and nature of drugs
Catheterized animals
Drugs administered IV followed by rapid fluid administration
Be careful of overhydration
Injections into the base of the tongue or by the intratracheal route are the second choice
Intracardiac injections should be avoided

72. Commonly used drugs Epinephrine Vasopressin Atropine
Cardiac arrest
Vasopressin
In place of or alternated with epinephrine
Atropine
Anesthesia-related cardiac arrest
Dopamine or dobutamine
Increase force and rate of cardiac contractions

73. Monitor cardiovascular and respiratory function
Blood pressure, blood gases, pulse oximetry, ECG, capnography
Drug and fluid therapy varies
Assess brain function
Repeat arrest within 24 hours is common
Following successful ROSC, other conditions may arise
Pulmonary or cerebral edema

74. CARDIAC ARREST - ABCDEF
ECG
Periodically check for spontaneous contractions by discontinuing external compression and either palpating for a pulse or looking for QRS complexes on the ECG.
Differentiate between different forms of cardiac arrest to more effectively pick the treatment

75. ECG Don’t use alcohol if a defibrillator is present Asystole
No electrical activity
Ventricular fibrillation
Coarse vertical zig-zag lines resulting from disorganized muscular heart activity
Pulseless electrical activity (electromechanical dissociation, EMD)
Normal or near-normal complexes

76. Regurgitation during anesthesia
A passive process under anesthesia
No retching, just fluid draining from animal’s mouth or nose
Stomach contents may be aspirated into respiratory tract
Most common occurrence in head-down surgical positions and in ruminants
Treatment
Immediate placement of cuffed ET tube
Clean out regurgitated material with suction

77. Vomiting during or after anesthesia
Common in brachycephalic dogs or nonfasted animals
An active process usually accompanied by retching
Usually occurs as the animal is losing or regaining consciousness
Signs
Airway obstruction leading to dyspnea/cyanosis, bronchospasm
Treatment
Intubation and suction if unconscious
Lower head and clean oral cavity if conscious

78. Seizures
Seen with ketamine administration, after diagnostic procedures (myelography), or preexisting conditions
Signs
Spontaneous twitching; uncontrolled movements of head, neck, and limbs; opisthotonus; triggered by a stimulus
Treatment
Reduce stimuli, postoperative analgesia, diazepam or propofol, monitor for hyperthermia

79. Seizures should be differentiated from excitement
Seen after barbiturate anesthesia or high opioid doses, as spontaneous paddling and vocalization
Treatment may not be necessary
Sedatives may help
Naloxone can reverse opioids
Seizures should be differentiated from excitement

80. Dyspnea in cats
Dyspnea is usually caused by laryngospasm sometimes triggered by removal of the ET tube
Laryngeal edema may result from repeated intubation attempts
May breathe with an audible stertor (wheeze) during inspiration
Differentiate from growling during expiration
May resolve itself or may need oxygen administration via facemask, intubation, or a tracheotomy
Is easier to prevent than treat

81. Dyspnea in dogs Breed-related Airway obstruction
Brachycephalic dogs
Airway obstruction
Anatomy, foreign objects, postsurgical tissue swelling
Humidified oxygen can be delivered to an awake animal
By facemask, nasal cannula, E-collar, or oxygen cage/tent