Week 4: Anaesthesia

Question 1

How do local anaesthetics work and what are some care considerations?

Answer 1

Electrical currents carried by ions
LA block channel for sodium ions –> blocks messages for pain, temperature, feeling
Wears off and sensation returns
Not typically reversible, have to wait for it to be absorbed and distributed in blood stream
Toxicity risk
Lipid soluble, so can administer intralipid to dilute

Question 2

What are the types of LA administration?

Answer 2

Topical
Spray
Injection: locally or around nerve fibre to provide regional block
Brachial plexus
Femoral
Spinal
Epidural

Question 3

What is anaesthesia?

Answer 3

The condition of having the feeling of pain and other sensations blocked, allowing patients to undergo surgery and other procedures without the distress and pain they would experience otherwise

Question 4

What is the history of anaesthesia?

Answer 4

Robert Liston – surgeon; butcher; showman.
Ether
1799 – Humphrey Davey – Nitrous Oxide
1846 – William Morton dental anaesthesia
Mid 1800’s - Nitrous Oxide for anaesthesia
1847 – Simpson (obstetrician) Chlorophorm; 1st death: 1848
1860 – Cocaine used for spinals; addiction destroyed lives & limited research
1905: Novocaine
Early – mid 1900’s – Curare
Mid 1900’s – Thiopentone
1986 - Propofol

Question 5

What does the Greek word, ‘anaesthesia’ mean?

Answer 5

Without feeling

Question 6

What does the Greek word ‘analgesia’ mean?

Answer 6

Without pain

Question 7

What are the determinants of anaesthesia?

Answer 7

Patient preference
Surgeon preference
Demands of surgery: type, site, access
Patient condition: medical, surgical, anaesthetic history

Question 8

What is the American Society if Anaesthesiologists physical status classification system?

Answer 8

ASA 1: normal healthy patient
ASA 2: mild systemic disease
ASA 3: severe systemic disease
ASA 4: severe systemic disease which is a constant threat to life
ASA 5: moribund patient, not expected to survive without operation
ASA 6: brain-dead, organs being removed for donation

Question 9

What is ASA 1?

Answer 9

Able to walk up a flight of stairs or down the street

Question 10

What is ASA 2?

Answer 10

Can walk up a flight of stairs or down the road, but may need to stop for a rest

Question 11

What is ASA 3?

Answer 11

Limited activity, but not completely debilitating

Question 12

What are examples of ASA 2 conditions?

Answer 12

Respiratory disease, anxiety, diabetes

Question 13

What are examples of ASA 3 conditions?

Answer 13

Angina, COPD, insulin dependence

Question 14

What is ASA 4?

Answer 14

Distressed at rest

Question 15

What are examples of ASA 4 conditions?

Answer 15

Unstable angina, CHF, uncontrolled diabetes, HTN

Question 16

What is Mallampati 1?

Answer 16

Soft palate, fauces, uvula, pillars entire glottic opening

Question 17

What is Mallampati 2?

Answer 17

Soft palate, fauces, uvula, posterior commissure

Question 18

What is Mallampati 3?

Answer 18

Soft palate, uvular, base, tip of epiglottis

Question 19

What is Mallampati 4?

Answer 19

Hard palate only, no glottal structures

Question 20

What is the triad of anaesthesia?

Answer 20

Hypnosis: unconsciousness
Analgesia: to prevent physiological responses to pain
Paralysis: muscle relaxation

Question 21

What are the steps on hypnosis?

Answer 21

Awake
Amnesia
Sedation
Hypnosis
Coma
Death

Question 22

What are the types of anaesthesia?

Answer 22

Local +- sedation
Regional block: brachail plexus, femoral nerve
Epidural
Spinal 
General

Question 23

What is local anaesthetic?

Answer 23

Drugs that block conduction when applied locally to nerve tissue. The block is entirely reversible

Question 24

What are the differences between a spinal and a epidural?

Answer 24

Intradural vs extradural
In CSF vs fat, blood vessels, nerve fibre endings
Single shot of 3-5 mL vs 15-20 Ml + infusion
Lasts 2-4 hours vs 2-4- hours + 2-3 days
Motor + sensory vs Sensory only

Spinal:
Complete blockage
Blocks SNS –> peripheral vasodilation –> decrease VR –> decrease CO –> decrease BP
Instant

Epidural:
Patchy, along dermatomes
Can move but feel weak

Question 25

What are different local anaesthetic medications?

Answer 25

Lignocaine: quick/short acting
Bupivacaine +- adrenaline (vasoconstriction for prolonged effect): slow and long action, regional
Ropivacaine: ""
Amethocaine: topical spray
Prilocaine: IV
Cocaine

Question 26

What are the advantages of LA?

Answer 26

Effective alternative to GA
Avoids polypharmacy
Allergic reactions
Extended analgesia
Patient can remain awake
Early drink/feed
Low level allergic reactions
Analgesia after surgery
Cheap

Question 27

What are the disadvantages?

Answer 27

Limited scope
Higher failure rate
Time constraints: waiting for LA to take effect
Anticoagulants/bleeding predisposition
Risk of neural injury

Question 28

What is general anaesthesia?

Answer 28

Drug induced loss of consciousness during which patients are nonresponsive, even to painful stimulation

Question 29

What determines spontaneous breathing or paralysed and ventilated GA?

Answer 29

Depends on demands of surgery and general well being of patient
Abdo surgery: paralysed and ventilated to control organs
Cardiothoracic: need heart and lungs paralysed
Less complex surgery which does not require organs can be spontaneous, e.g. knee arthroscopy

Question 30

What are the benefits of GA?

Answer 30

No absolute contraindications;
Quick to establish;
Never fails to work;
Often the only option available for major operations;
Can provide the best operating conditions for the surgeon;
The patient is completely unconscious and unaware

Question 31

What are the complications of GA?

Answer 31

Polypharmacy;
Effects on various systems;
Allergic reactions;
Recovery profile;
PONV;
'Awareness' during surgery

Question 32

What are the phases of GA?

Answer 32

Induction
Maintenance
Reversal
Recovery

Question 33

How do the stages of anaesthesia compare to stages of alcohol intoxication?

Answer 33

1. Amnesia and analgesia vs dizzy and delightful
2. Uninhibited response to stimuli vs drunk and disorderly
3. Surgical anaesthesia vs unconscious drunk
4. Vital centre depression vs alcohol poisoning

Question 34

What is involved in the induction stage of GA?

Answer 34

IV or inhaled
Monitoring
Preoxygenation
Hypnotic/analgesia and/or relaxant
Mack/LMA/ETT

Question 35

What is involved in the maintenance stage of GA?

Answer 35

IV or inhaled
O2 40-100%
Nitrous oxide: anaesthetic machines automatically increase O2 to ensure more O2 than nitrous oxide always given
Muscle relaxant
Analgesia

Question 36

What is involved in the recovery stage of GA?

Answer 36

Turn off agent
Reverse relaxant
Cough reflex returns: throat movement as tries to swallow, HR increases as LMA/ETT irritated 
Extubate upon waking
Recovery position
Monitor until discharge

Question 37

What is a depolarising NMB agent and how does it work?

Answer 37

Suxamethonium
Small % of people develop sux apnoea

Motor neurons release neurotransmitters called acetylcholine at their nerve axon terminals to jump synaptic cleft and continue nerve impulse to next neuron
ACh changes permeability of cells to allow Na+ in and K+ out, creating an action potential which leads to depolarisation and muscle contraction
Mimics ACh, causing vesculations (fine motor twitching)
No reversal agent, must be able to maintain airway
Short duration

Question 38

What is a non-depolarising NMB agent and how does it work?

Answer 38

Actracurium
Cisactracurium
Mivacurium
Pancurium
Rocuronium
Vecuronium
Produces histamine release: rask, swelling

Motor neurons release neurotransmitters called acetylcholine at their nerve axon terminals to jump synaptic cleft and continue nerve impulse to next neuron
ACh changes permeability of cells to allow Na+ in and K+ out, creating an action potential which leads to depolarisation and muscle contraction
Competes with ACh and blocks it from reaching receptor site
Broken down over time, quicker with anticholinergics
Administered with atropine (cause bradycardia)

Question 39

What medication is used as a reversal agent for non-depolarising NMB agents and how does it work?

Answer 39

Neostigmine

Cholinesterase which breaks down ACh

Question 40

What are the requirements for Rapid Sequence Induction?

Answer 40

Good IV access
O2
Suction
Introducer loaded with ETT
Air syringe
2 working laryngoscopes
Stethoscope
Trachy tape
Monitoring: NIBP, PSAO2, ECG, ETCO2

Question 41

When is RSI used?

Answer 41

Patients at risk of aspiration:
Short fasting times, e.g. emergency surgery
Pregnany: added weight on gut may force aspirate out of sphincter when relaxes
Obese: “”
GORD
Oesophageal pouch surgery

Question 42

What is the sequence for RSI?

Answer 42

Preoxygenation 100% O2 for 3 minutes
Thiopentone followed rapidly by suxamethonium
Rocuronium 
Cricoid pressure applied
Fasciculations
Laryngoscopy and intubation
ETT inflated, test ventilation and check for ETCO2
Confirm position with stethoscope
ETT secured
Cricoid pressure released

Question 43

What is the reversal agent for rocuronium?

Answer 43

Sugammadex

Question 44

What is malignant hyperthermia?

Answer 44

Rare, life threatening
Triggered by volatile anaesthetic agents, e.g. suxamethonium
Inherited autosomal dominant disorder

Question 45

What are the signs of malignant hyperthermia?

Answer 45

Early signs: rise in CO2, temp and RR, desaturation
Drastic, uncontrolled increase in skeletal muscle metabolism –> increase in waste production –> lactic acidosis –> disturbs ability for gas exchange

Question 46

What is the prevention for malignant hyperthermia?

Answer 46

Designated machine for patients which family hx of MHT, not contaminated with gas

Question 47

What is the management for malignant hyperthermia?

Answer 47

Adrantoline sodium, 1mL per kg
May need 25 bottles
Active cooling (irrigation with catheter, packing body cavity with cold slush

Question 48

What is the action, onset, duration, indication, reversal and precautions of suxamethonium?

Answer 48

Depolarising muscle relaxant. IV administration.
Action: mimics Acetylcholine, occupies receptor sites at the Neuromuscular Junction, lasting longer than Ach. Depolarised membranes remain depolarised and unresponsive to additional stimuli.
Onset: rapid – (1 circulation time)
Duration of Action: ½ life estimated at 2 mins. Ultra short acting
Indication: profound but brief muscle relaxation (paralysis) for intubation. Always used for intubation when patient has unknown fasting details or a full stomach, as action is rapid and complete.
Reversal: no pharmacological antidote or reversal agent. Broken down by enzymes (pseudocholinesterase).
Precautions & Side Effects: Apnoea - may have extended duration of action on specific population group – congenital abnormal pseudocholinesterase required to metabolise drug. Artificial respiration required until effects wear off.
Muscle pain resulting from fasciculations (rapid muscle twitches as drug occupies receptor sites and depolarisation occurs.)

Question 49

What is the action, onset, duration, indication, reversal and precautions of actracurium?

Answer 49

Non-depolarising muscle relaxant. IV administration.
Indication: used as an adjunct to general anaesthesia to enable endotracheal intubation, and to relax skeletal muscles during surgery, or controlled ventilation, and to facilitate mechanical ventilation in ICU pts. Has no effect on consciousness.
Action: competes with Acetylcholine binding competitively with cholinergic receptor sites on the motor end plate at the Neuromuscular Junction.
Onset: suitable intubation conditions 2-2 ½ mins. 3-5 minutes following admin.
Duration of Action: 20-35 mins (depending on dose)
Reversal: reversed by acetylcholinesterase inhibitors such as Neostigmine (side effect bradycardia, hence added with anticholinergic – Atropine)
Precautions & Side Effects :Administer only with adequate anaesthesia or sedation/ analgesia; facilities for endotracheal intubation and ventilation, including administration of O2 under positive pressure and elimination of CO2. Reversal agents should be immediately available.

Question 50

What is the action, onset, duration, indication, reversal and precautions of thiopentone?

Answer 50

Indication: IV anaesthetic for short duration operations; induction of anaesthesia prior to administration of other anaesthetic agents.
Action: hypnotic; anaesthetic; Ultra short acting depressant of the CNS which induces hypnosis & anaesthesia, but not analgesia.
Onset: unconsciousness 30-40 secs following IV injection.
Duration of Action: consciousness returns 20-30 mins after a single induction dose. ½ life of elimination 3-8hrs.
Reversal: nil. treat symptoms as they arise until drug is metabolised.
Precautions & Side Effects:. Thiopentone may decrease LOS tone. Avoid intra-arterial injection (causes necrosis). Respiratory depression. Hepatic & renal disease may prolong effect.
CI: status asthmaticus; lack of adequate airway; complete absence of suitable vein

Question 51

What is the action, onset, duration, indication, reversal and precautions of diprivan?

Answer 51

Indication: Short acting IV anaesthetic agent suitable for both induction and maintenance of general anaesthesia in adults and children.
Ideal anaesthetic agent for the outpatient, day only, shorter procedures. As infusion – total IV Propofol results in a more rapid recovery and less PONV than comparison drugs. Suitable for use as sedation for ventilated ICU patients; conscious sedation for surgical & diagnostic procedures.

Onset: 60 - 120 secs. (dose dependant)
Duration of Action: 5-10 minutes following induction dose.
Reversal: Unlike other sedation agents (Midazolam, Morphine) there is no reversal agent; Adverse effects must be treated until the drugs is metabolised.
Precautions & Side Effects: reduces cerebral blood flow; pain on injection; all general anaesthetics cross the placenta with the potential to cause CNS & respiratory depression in the newborn infant

Question 52

What is the action, onset, duration, indication, reversal and precautions of sevoflurane?

Answer 52

Indication: induction and maintenance of anaesthetic in adults and paediatric patients undergoing surgery. Fast acting non-irritating agent; rapid loss of consciousness during inhalation induction; rapid recovery following discontinuation.
Action: inhalation anaesthetic agent.
Onset: administered at 5% - surgical anaesthesia produced in <2 mins. A short acting barbiturate or other intravenous induction agent should be administered followed by inhalation of Sevoflurane.
Duration of Action: emergence times short; pts may require pain relief earlier than others.
Reversal: there is no reversal agent, although 100% O2 would assist in the dilution and elimination of drug from the alveoli. Assisted or controlled ventilation required.
Precautions & Side Effects: Caution in patients with severe renal or hepatic impairment; .
CI: Malignant Hyperthermia

Question 53

What is the action, onset, duration, indication, reversal and precautions of isoflurane?

Answer 53

Indication: inhalation anaesthetic agent; induction and maintenance of general anaesthetic.
Onset: inspired concentrations of 1.5-3% may produce surgical anaesthesia in 7-10 mins.
Reversal: 100% O2 with assisted or controlled ventilation.
Precautions & Side Effects:. Mild pungency which limits rates of admin during inhalation induction; Respiratory depression; hypotension. Potentiates the effects of all muscle relaxants – notably all non-depolarising muscle relaxants.
CI: known or suspected Malignant Hyperthermia

Question 54

What is the action, onset, duration, indication, reversal and precautions of bupivacaine?

Answer 54

Indication: local anaesthetic; production of spinal anaesthetic.
Action:.causes a reversible blockade of impulse along nerve fibres by preventing the inward movement of sodium ions through the nerve membrane.
Onset: slower than lignocaine;
Duration of Action: up to 4X potent as lignocaine; motor blockade 3-4hrs in spinal application, shorter than sensory blockade.
Reversal: lipid reversal for toxicity
Precautions & Side Effects:. monitor cardiovascular & respiratory function. Slow injections with frequent aspirations to avoid intravascular administration. Restlessness, anxiety, tinnitus, dizziness + early signs of toxicity
Adverse reactions: hypotension; bradycardia; cardiovascular toxicity; high / total spinal blockade.
CI: IV administration; epidural & spinal anaesthesia in pts with uncorrected hypotension, coagulation disorders & on anticoagulation therapy

Question 55

What is the action, onset, duration, indication, reversal and precautions of ropivacaine?

Answer 55

Indication: local anaesthetic; epidural block inc. for caesarian; minor & major nerve block; infiltration. Continuous epidural infusion or intermittent bolus administration for analgesia in postoperative pain; continuous peripheral nerve block infusion for intra & post-operative pain management.
Action: Causes a reversible blockade of impulse along nerve fibres by preventing the inward movement of sodium ions through the nerve membrane.
Anaesthetic and analgesic effects; at higher doses produces surgical anaesthesia with motor block, lower doses produces sensory block (inc. analgesia) with little motor block.

Onset:
Duration of Action:.
Reversal:
Precautions & Side Effects: Monitor cardiovascular & respiratory function.
Adverse reactions:. Total spinal block may occur if an epidural dose is inadvertently administered into the subarachnoid. may lead to CNS depression, cardiovascular collapse, and respiratory arrest. Toxicity symptoms include visual or auditory disturbances, dizziness, to convulsions.
CI: IV administration; uncorrected hypotension; local inflammation, sepsis; Bier’s block

Question 56

What is the action, onset, duration, indication, reversal and precautions of droperidol?

Answer 56

Indication: Anaesthesia: General anaesthesia adjunct (to reduce PONV); premedication; regional anaesthesia adjunct.
Neuroleptanalgesia : when given concurrently with narcotic analgesic - produce tranquillity and decreasing anxiety and pain. Psychiatry: severe agitation, hyperactivity & agitation. Mania.
Onset: 3-10 mins.
Duration of action: 2-4 hrs. Altered consciousness up to 12hrs.
Reversal: No specific antidote – treatment is primarily supportive; severe extrapyramidal reactions, hypotension, drowsiness.
Precautions: High dose, prolonged use; spinal anaesthesia; a history of significant cardiac disease, serious ventricular arrhythmia. May cause drowsiness. Hypotension. Respiratory depression.
CI: severe CNS depression; clinically significant bradycardia. Drugs prolonging QT interval eg amiodarone, sotalol; some antihistamines

Question 57

What is the action, onset, duration, indication, reversal and precautions of rocoronium?

Answer 57

non-depolarising muscle relaxant; IV bolus or infusion.
Indication: adjunct to general anaesthesia to facilitate endotracheal intubation during routine induction; to facilitate mechanical ventilation. Adjunct to GA when suxamethonium is CI.
Action: competes with acetycholine blocking receptor sites at the motor end plate
Onset:.fast onset; intubating conditions achieved within 60 secs. General muscle paralysis achieved within 2 mins.
Duration of action: intermittent duration. 14-20 mins
Reversal: administration of acetylcholinesterase inhibitors, such as neostigmine., should not commence until definite signs of spontaneous recovery are present.
Precautions & Side Effects:. Injection site pain; profound prolonged paralysis; tacchycardia; Administer only with adequate anaesthesia or sedation/ analgesia; facilities for endotracheal intubation and ventilation, including administration of O2 under positive pressure and elimination of CO2. Reversal agents should be immediately available.
CI: Bromide ion hypersensitivity

Question 58

What is the action, onset, duration, indication, reversal and precautions of fenanyl?

Answer 58

Synthetic opioid. Analgesic (related to morphine, 80x potent).
Indications: short duration analgesia during premedication, induction and maintenance of anaesthesia & immediate postoperative periods. Opioid analgesic supplement in general and regional anaesthesia.
Duration of action: 30-60 mins.
Onset: mins
Reversal: Opioid antagonists such as naloxone, consider duration of respiratory depression vs duration of action of Naloxone. Assist or control adequate ventilation.
Precautions & side effects: Respiratory depressant; may cause respiratory depression in newborn infant.
CI: bronchial asthma; respiratory depression;
Fentanyl may be used in combination with neuroleptic agents such as droperidol as an anaesthetic premedication, for the induction of anaesthesia, and as an adjunct in the maintenance of general and regional anaesthesia.
The state of neuroleptanalgesia may be converted to neuroleptanaesthesia by the concurrent administration of 65% nitrous oxide in oxygen

Question 59

What is the action, onset, duration, indication, reversal and precautions of epidural anaesthetic?

Answer 59

Injection of local anaesthetic (+/- narcotic – Fentanyl) into the posterior lumbar epidural space.
Indications: postoperative pain relief; lower abdominal procedures; normal & high risk obstetric procedures.
Advantages: Slower onset compared to spinal, of sympathetic blockade – allows for compensation through vasoconstriction.
Ability to administer via continuous epidural infusion or intermittent bolus administration for analgesia in postoperative pain.
Disadvantages: relative difficulty of technique; can be an incomplete block - following dermatomes.
CI: absolute: anticoagulant therapy; hypovoleamia; systemic or localised infectin near needle puncture site; raised ICP; relative: inexperience; CNS disease; previous spinal surgery

Question 60

What is spinal anaesthetic?

Answer 60

Consists of injecting local anaesthetic into the subarachnoid space with the resultant blockade of the spinal nerve roots. cerebro-spinal fluid (CSF). Usually occurs in the lumbar spine below L2 (spinal cord ends).
Spinal anaesthesia is best reserved for operations below the umbilicus e.g. hernia repairs, gynaecological and urological operations and any operation on the perineum or genitalia.

Spinal anaesthesia is especially indicated for older patients and those with systemic disease such as chronic respiratory disease, hepatic, renal and endocrine disorders such as diabetes. Most patients with mild cardiac disease benefit from the vasodilation that accompanies spinal anaesthesia except those with stenotic valvular disease or uncontrolled hypertension.

Question 61

What are the advantages of spinal anaesthetic?

Answer 61

Produces few adverse effects on the respiratory system as long as unduly high blocks are avoided.
Airway not compromised; there is a reduced risk of airway obstruction or the aspiration of gastric contents. This advantage may be lost with excessive sedation.
Spinal anaesthesia provides excellent muscle relaxation for lower abdominal and lower limb surgery. Complete blockade (motor & sensory).

Question 62

What are the disadvantages of spinal anaesthetic?

Answer 62

Some patients are not psychologically suited to be awake, even if sedated, during an operation. Post spinal headache.
Even if a long-acting local anaesthetic is used, a spinal is not suitable for surgery lasting longer than approximately 2 hours. If an operation unexpectedly lasts longer than this, it may be necessary to convert to a general anaesthetic.

Question 63

What is the role of the anaesthetic nurse?

Answer 63

Be fully engaged
Preempt decisions
Plan care
Be highly involved with technology
Check anaesthetic equipment and support anaesthetist

Question 64

What needs to be checked on the anaesthetic machine?

Answer 64

Gas supplies
Ventilator function
Suction and scavenging systems
Inhalation agents
Anaesthetic circuit
CO2 absorber: soda lime
Gas analyser: ETCO2
Monitoring: BP, PSAO2, ECG