What to do when things aren't going to plan during anaesthesia?

Question 1

1. Normal SpO2 in anaesthetised dog/cat breathing 100% O2.
2. What to do when SpO2 falls below this as first step?
3. What contributes to SpO2?

Answer 1

1. 98-100%.
2. Check pulse oximeter for damage.
   Test pulse ox on own finger.
   Dampen tongue / massage tongue.
   Reposition pulse ox on tongue.
3. O2 delivery to patient.
   O2 transported into the lungs.
   O2 delivered to the tissues.
   Reposition pulse ox to completely new location.

Question 2

Next steps of what to do if SpO2 falls…
If patient not intubated.

Answer 2

Is O2 supplied via mask?
–> If no, straighten neck, pull tongue forward, check mouth and pharynx and suction if required, then supply O2 by mask or intubation.
–> If yes, check mask for leaks, straighten neck, check mouth and pharynx and suction if required, may need to intubate.

Question 3

1. Why would the intubation be difficult?
2. How can we overcome this?

Answer 3

1. Laryngeal mass or anatomical issues e.g. brachycephalic dogs.
2. Pre-oxygenation w/ mask prior to attempting to intubate.
   Have all equipment to hand before attempting intubation.
   Administration of corticosteroids (hydrocortisone) may be needed.

Question 4

What needs to be checked if SpO2 low and patient intubated and attached to anaesthetic machine?

Answer 4

Pressure gauges on the GA machine.
- If not ok, check if cylinder turned on, question if cylinder empty, check pipeline plugged in.
- If ok, check flow rate adequate for patient and circuit used is appropriate.
– If not, adjust as appropriate.
–> If flow rate is adequate and system is appropriate, check anaesthetic machine over (this should not be needed because this should have bee checked prior to inducing anaesthesia).

Question 5

1. What to do when breathing system not attached correctly to the patient and machine?
2. What to do if breathing system is correctly attached to the patient and machine?

Answer 5

1. Ensure all connections are correct.
2. Check breathing system for leaks.
   - If leaks, fix or replace.
   Check ETT for leaks.
   - If leaks, fix or replace.

Question 6

What if the breathing system and ETT are not leaking?

Answer 6

Check that the cuff is still adequately inflated as this can become less so when the patient is moved. Also check for a slow leak around the cuff valve.

Question 7

1. What to do if patient is breathing spontaneously.
2. What to do if patient on ventilator?

Answer 7

1. Check if normal or abnormal respiratory pattern.
   - Abnormal breathing pattern is if they are panting (often result of inadequate anaesthesia) or paradoxical ventilation where abdomen rises and thorax falls on inspiration and vice versa on expiration (often associated w/ respiratory tract obstruction).
2. Check ventilator settings and connections.

Question 7

What if patient not breathing at all?

Answer 7

• Post induction apnoea can be common.
• Check depth of anaesthesia – too light or deep?
  – Too light may mean breath holding.
  – Too deep may result in loss of respiratory drive due to depression of respiratory centre in the brain.
• Some drugs are known to affect respiratory drive, esp. opioids like fentanyl (decrease brain sensitivity to CO2 so will see hypercapnia).
• Are you using a neuromuscular blocking agent?

Question 8

What to look for when squeezing the reservoir bag?

Answer 8

Manual ventilation.
Chest rising?
Can you hear gas leaks? (Go back to ETT checks).

Question 9

What if you don’t see thoracic cage expanding when squeezing the reservoir bag?

Answer 9

• Check if there is an external mechanical issue like a sandbag or surgeon pressing on the chest.
  – If no, is the chest open, losing pressure to allow breathing? Is there fluid or air in the thoracic cavity? Could ETT or airway be blocked?

Question 10

What is the lungs are able to expand when you squeeze the reservoir bag?

Answer 10

• Check if lungs able to contract after expansion.
  – If no, there is a blockage in the expiratory gas pathway preventing this.
  –> If T-piece, check bag is not twisted.
  –> Is the APL valve closed?
  –> Check for kinks in breathing system tubing or heavy items compressing it.
  –> Consider if ETT or airway could be blocked.
  —» Could be due to ETT being too long, so end sitting against bronchus and occluding.
  —» Could be due to neck in severe flexion.
  —» Could be due to debris in ETT or RT e.g. blood, mucus, tissue.
  —» Could be due to FB somewhere in RT.

Question 11

What if you have resolved all issues w/ oxygen supply and are sure there are no obstructions to flow and the patient still not breathing well/at all.

Answer 11

Need to ventilate the patient.
- Manually w/ care not to over-inflate the lungs and for a short period.
- On a ventilator which gives more control and is better if ventilation needed for longer duration.

Question 12

1. What are other causes of hypoxaemia seen in compromised patients? (ASA 3-5).
2. What can be do to better help these patients?

Answer 12

1. Ventilation-perfusion mismatch.
   Shunt or venous admixture.
   Diffusion barrier.
2. Identify potential issues prior to anaesthesia.
   May be prudent to plan to use IPPV during the anaesthesia.

Question 13

What can bradycardia and tachycardia affect?

Answer 13

CO. As heart may not be filling or emptying properly.

Question 14

1. How do you determine tachycardia during anaesthesia?
2. What could be causing the tachycardia during anaesthesia.

Answer 14

1. Via basic monitoring the pulse or cardiac auscultation.
2. Inadequate anaesthesia depth/ inadequate analgesia.
   Hypercapnia.
   Hypoxia.
   Hypovolaemia / hypotension.
   Secondary to some drugs.
   Electrolyte abnormalities (e.g. hypokalaemia).
   Hyperthermia.
   Underlying condition.

Question 15

Tachycardia due to inadequate anaesthetic depth.

Answer 15

• Common in ASA 1 and 2 patients undergoing routine procedures.
• Depth will need to be adjusted in response to noxious and non-noxious stimuli.
• If associated w/ increase muscle tone, increased RR and BP – patient too lightly anaesthetised.
• May also get patient movement if anaesthesia too light.
• Adjust anaesthesia appropriately +/- additional analgesia (like fentanyl bolus).

Question 16

Tachycardia due to hypercapnia.

Answer 16

• Common reason in ASA1 and 2 patients undergoing routing procedures.
• Measured w/ capnograph.
• Mostly will be caused by inadequate respiration.
• Follow same steps as for SpO2 falling.

Question 17

Tachycardia due to hypotension/hypovolaemia.

Answer 17

• Hypovolaemia means that the patient is either dehydrated or haemorrhaging.
• Should stabilise patient before anaesthesia, and only skip this if in an emergency.
• Will need to manage fluid deficit.

Question 18

Tachycardia due to drug action.

Answer 18

• Secondary to drugs – can be direct or indirect.
• Direct: alfaxolone, ketamine, atropine, dopamine.
• Indirect: anaphylaxis.
• Rule out other causes first.

Question 19

Tachycardia due to electrolyte abnormalities and underlying conditions.

Answer 19

• Unusual not to be aware of this prior to induction of anaesthesia.
• Should be picked up on pre-anaesthetic examination.
• Ideally stabilise patient prior to anaesthesia.
• Anaesthetic planning for high risk cases (ASA 3-5).

Question 20

1. How to detect bradycardia during anaesthesia?
2. What could be done to further investigate?

Answer 20

1. Via basic pulse monitoring or cardiac auscultation.
2. ECG to help determine the underlying electrical activity in the heart.

Question 21

Bradycardia during anaesthesia.

Answer 21

• Various causes – may need other info to determine cause.
• Patient too deeply anaesthetised.
• Drug effects.
• Increased vagal tone or vagal stimulation.
• Hypothermia.
• Severe hypoxia.
• Hypertension (reflex bradycardia).
• Hyperkalaemia.
• Severe metabolic abnormalities (e.g. hypoglycaemia or acidaemia).

Question 22

Bradycardia due to deep anaesthesia.

Answer 22

• Check indicators of anaesthetic depth i.e. muscle tone, eye position, reflexes.
• Will be associated w/ decreased RR and BP.
• Depth will need to be adjusted in response to noxious and non-noxious stimuli.

Question 23

Bradycardia due to drug action.

Answer 23

• Opioids and a2-agonists.
• Vagally mediated.
• Can be treated w/ atropine (anti-cholinergic).
• Would generally not do this unless worried hypotension / reduced perfusion or arrhythmias.

Question 24

Bradycardia due to high vagal tone / vagal reflex stimulation.

Answer 24

- Some patients (e.g. brachycephalic dogs) may have high vagal tone. - Stimulated by occulocardiac reflex. - Can use anticholinergics to treat either pre-emptively or when occurs.

Question 25

Bradycardia due to hypoxia, hypothermia, hyperkalaemia, hypertension, severe metabolic abnormalities.

Answer 25

- Prevention better than cure. - Hypoxia: will be severe if w/ bradycardia. - Hypothermia: Preserve body temp. during anaesthesia (warming, prevent heat loss) and monitor body temp. - Hyperkalaemia: Pre-anaesthetic check and screen potentially hyperkalaemic patients before anaesthesia (renal failure, urethral obstruction, diabetes) and stabilise before anaesthesia. - Others: need to treat underlying cause / stabilise before anaesthesia.

Question 26

1. What will BP read as if patient hypotensive? 2. What can hypotension be down to?

Answer 26

1. MAP 60mmHg or sys 80mmHg on doppler. 2. Reduced inflow to the heart. Reduced pumping function of the heart. Reduced vascular resistance.

Question 27

Causes of hypotension during anaesthesia.

Answer 27

- Anaesthetic drugs. - Blood loss during surgery. - Pre-existing conditions -- hypovolaemia, shock, cardiomyopathy, valvular heart disease, arrhythmias, hypothyroidism, hypoxaemia, Addisonian crisis. - Anaphylactic reaction to drugs, blood or blood products administered during anaesthesia.

Question 28

How do we manage hypotension during anaesthesia?

Answer 28

- If likely to be due to anaesthesia (ASA 1 AND 2). -- Turn down anaesthetic. -- If severe, turn off for 1-2 mins. -- IV crystalloid bolus. -- If hypotension persists, administer positive inotrope like dopamine or ephedrine. - If cause known, treat primary problem (i.e. replace blood loss). - Ensure adequate oxygenation and ventilation.

Question 29

What can accidents and emergencies in anaesthesia be caused by?

Answer 29

-- Multifactorial. - Sick animal. - Human error. - Equipment failure. - Inadequate preparation. - Inadequate monitoring.

Question 30

How do we prevent accidents and emergencies occurring during anaesthesia?

Answer 30

- Preferably stabilise before procedure/ postpone procedure/ plan and have all equipment and drugs to hand. - Check lists, communication during procedure, HALT (hungry, angry, late/lonely, tired). - Check all equipment before use. - Do not skimp time on preparation. - Even if you don't have extensive monitoring equipment, you have eyes, ears and fingertips.

Question 31

Common human errors in anaesthesia?

Answer 31

- Leaving APL valves closed. - Drug administration errors. - Airway management errors. - Errors with positioning. - Inadequate eye protection for patient.

Question 32

What could be observed if the APL valve left closed?

Answer 32

- Reservoir bag distends. - Reduced thoracic movements. - Possibly leaking round ETT cuff. - Tachycardia, hypoxia. - Potential for pneumothorax / pneumomediastinum due to rupture of lung tissue or trachea. - Potentially fatal.

Question 33

What aspects of drug administration may be done w/ error.

Answer 33

Incorrect calculation. Incorrect route. Wrong drug. Perivascular administration.

Question 34

Airway management errors.

Answer 34

Failed intubation. Traumatic intubation. Tracheal rupture.

Question 35

Positioning errors.

Answer 35

EPAM (Equine post anaesthetic myopathy). Pain. Compromised ventilation. Compromised CV function. Tourniquet effect (ischaemia).

Question 36

Inadequate eye protection for the patient.

Answer 36

- Anaesthesia / sedation reduces tear formation. - Eyes often open during anaesthesia and no blinking. - Bland ophthalmic ointment. - Avoid trauma. - Corneal ulceration will result from not protecting the eyes.

Question 37

Mechanisms of respiratory failure in anaesthesia.

Answer 37

- Depression of respiratory centre in brain. - Interruption of nervous/neuromuscular transmission. - Impaired movement of the thoracic cage e.g. sandbags, increased intra-abdominal pressure. - Impaired lung movement e.g. pleural effusion. - Airway obstruction.

Question 38

Cardiac arrest during anaesthesia.

Answer 38

- Cessation of an effective circulation. -- Pre-existing cv disease. -- Anaesthetic overdose. -- Arrhythmias, catecholamine release. -- Hypovolaemia. -- Electrolyte/acid base abnormalities. -- Vagal reflexes. -- Hypoxia/hypercapnia/respiratory arrest.

Question 39

What would be seen on ECG if patient having a cardiac arrest?

Answer 39

- Ventricular asystole. - Ventricular fibrillation. - Electromechanical dissociation / pulseless idioventricular rhythm. (no pulse or cardiac sounds).

Question 40

1. What would MAP be if patient hypertensive? 2. What would cause hypertension in anaesthesia?

Answer 40

1. >120mmHg. 2. Inadequate analgesia. Inadequate anaesthesia. Hypercapnia. Hypoxia. Drugs.

Question 41

Vomiting and regurgitation in anaesthesia.

Answer 41

- Spp. and pain dependent. - Drug induced. - Reduce risk by pre-anaesthetic fasting. - Danger periods are induction and recovery. - Head elevated until ETT placed and cuff inflated. If patient does vomit or regurgitate: - Put their head down. - Suction/swab out pharynx. - Consider omeprazole IV in animals known to be at risk of regurgitation. - Record incident on anaesthetic record.

Question 42

1. Risk factors for oesophageal reflux. 2. What may be seen in recovery w/ oesophageal reflux? 3. What do we worry about in patients that get oesophageal reflux?

Answer 42

1. - Excessive/inadequate fasting. - Drugs. - Abdominal pressure. - Abdominal surgery / long ops. 2. Blood tinged fluid vomited / appear unable to swallow / appear distressed. 3. Reflux oesophagitis or oesophageal stricture.