Intraoperative and postoperative care

Question 1

Define sleep

Answer 1

Recurring lowered LOC associated with decreased response to external stimuli, but from which a person can be readily awakened

Question 2

Define unconsciousness

Answer 2

State of unawareness where the patient is incapable of responding to sensory stimuli or of having subjective experiences

Somatic and autonomic reflexes to pain and noxious stimuli may still occur

Question 3

Define anaesthesia

Answer 3

A state of drug-induced hypnosis, which is distinct from unconsciousness.

It is accompanied by a loss of motor response to noxious stimuli, which for the inhalational agents is measured as MAC

During anaesthesia there is a lack of explicit awareness

BUT

There is evidence to suggest that the state of drug induced anaesthesia is often associated with some level of consciousness = implicit awareness.

Question 4

Describe the phases / stages and planes of anaesthesia

Answer 4

Phase 1 - Induction
Phase 2 - Maintenance
Phase 3 - Emergence

Stage 1: Analgaesia
Induction –> LOC

Stage 2: Excitement (Reduced autonomic stability)
LOC --> Regain Autonomic Stability (Airway reflexes | Regular breathing | BP regulation)
- Breath-holding
- vomiting
- coughing
- swallowing
- gagging
- struggling

Stage 3: Surgical (autonomic stability regained)
Automatic breathing –> respiratory paralysis

Plane I: Eye rolling to fixed
Plane II: Loss of corneal / laryngeal reflexes
Plane III: Pupils dilate / loss of accommodation
Plane IV: Intercostal paralysis (shallow abdo breathing)

Stage 4: Overdose (loss of autonomic stability)
Decreased breathing and re-emergence of autonomic instability with deteriorating cardiac output and tissue perfusion.

Stage 5: Cardiac arrest

Question 5

Describe important patient responses to surgical stimulation if the patient is not deep enough

Answer 5

Somatic

• laryngospasm
• Movement of extremties

Autonomic

• Hypertension
• Tachycardia
• Sweating
• lacrimation

Question 6

Describe the order in which reflexes disappear with deepening anaesthesia

Answer 6

1. Eye movement (voluntary)
2. Eye movement (involuntary)
3. Eyelash reflex
4. Eyelid reflex
5. Swallowing | retching | vomiting
6. Conjunctival reflex
7. Airway muscle tone
8. Corneal
9. Glottic reflex
10. Pupillary light reflex

Question 7

Why is urine production reduced in the perioperative and emergency setting

Answer 7

Stress response

• SNS RAAS activation and reduced GFR (decreased RBF)
• ADH release

Conservation of Na and fluid in stressful scenario to optimise blood flow to heart, lungs and skeletal muscle whilst maintaining perfusion of the brain (diverted away from kidney/GIT/Liver/Skin

Question 8

Why is it important to confirm a diminishing level in recovery after neuraxial anaesthesia

Answer 8

If there is inadequate sensory or motor recovery from spinal anaesthesia this could be due to a epidural hematoma and requires prompt neurosurgery - within 6 hours

Question 9

Describe the score used to assess patient readiness for discharge from 1. Recovery (PACU)

Answer 9

ALDRETE SCORE to determine readiness for PACU/Recovery discharge

The following is repeated every 15 minutes

Score of 9 or more out of 10 required prior to discharge to ward

AIRWAY AND BREATHING
2 Breath and cough normally
1 Dyspnoeic with limited breathing
0 Apnoeic

CIRCULATION
2 BP < 20% baseline
1 BP 20 - 50 % baseline
0 BP > 50 % from baseline

DISABILITY
2 Fully awake
1 Arousable on calling
0 Not responding

EXPOSURE
2 Four limbs moving voluntarily or on command
1 Two limbs moving voluntarily or on command
0 Unable

COLOUR/SaO2
2 Pink / SaO2 > 90% on FiO2 0.21
1 Pale/dusky/blotchy/jaundiced or SaO2 > 90% on FiO 0.4
0 Cyanosed or SaO2<90 on FiO2 < 0.4

Question 10

Give two examples of processed EEG monitors and how these work

Answer 10

BIS and Entropy

Measures and interprets EEG ways via an algorithm to determine a score on a scale of 0 - 100.

0 - Flat line EEG
20 - Burst suppression (Coma/Hypothermia/Extremely deep GA)
40 - 60: Target for general anaesthesia
60 - 80: Deep - Mild Sedation
80 - 100: Drowsy - Awake

Question 11

List 4 potential reasons why the processed EEG monitors (BIS and Entropy) are not 100% effective in preventing awareness under general anaesthesia

Answer 11

1. Does not measure depth of anaesthesia directly. BIS/Entropy measure brains response to stimulation and is therefore affected by analgaesics and other drugs.
2. The anaesthetic effects of ketamine and N2O are not detected.
3. EMG noise from muscles near scalp electrodes may interfere with DOA processed EEG algorithms