2.2 Adjuvants

Question 1

Adjuncts used in regional anaesthesia

Spinal

Answer 1

Opioids
Adrenalin and phenylephrine
Clonidine

Have been used but not favoured
Ketorolac
Neostigmine
Midazolam

Question 2

Adjuncts used in regional anaesthesia

Epidural

Answer 2

Opioids
Vasoconstrictors
Clonidine
Sodium bicarbonate

Have been used but not favoured

Ketamine
Neostigmine

Question 3

How do opioids act when given spinally / epidural

Answer 3

When Given Spinally or epidurally,

opioids reduce the afferent nociception input,

providing analgesia

Thus, they act synergistically with
local analgesics.

Question 4

Affect on CVS when opioids are given centrally

Answer 4

Because they help
reduce the amount of LA needed,

they confer cardiovascular stability;

however,

owing to action on
sympathetic ganglia,
they may reduce sympathetic outflow,
resulting in hypotension.

Question 5

What are side effects of intrathecal opioids

What is the proposed mechanism

Answer 5

Intrathecal opioids help reduce
the amount of local anaesthetic required,

offer added analgesia and
may prolong the total
duration of analgesia.

However,

morphine through this route may
increase the risk of

delayed respiratory depression
due to rostral migration
through cerebrospinal fluid.

Question 6

What are the different opioid options

How do these differ

Answer 6

Lipophilic opioids like
fentanyl and sufentanil
hasten the onset but offer limited duration.

Sufentanil probably acts systemically
rather than spinally,
as it is highly lipophilic.

Remifentanil is not used via this route
as it contains glycine.

When used with chlorprocaine, opioids may actually delay discharge in ambulatory
settings.

Question 7

How epidural fentanyl act

Bolus vs infusion

Answer 7

Epidural fentanyl
reduces volatile requirements
when compared with
its use intravenously.

As a bolus, it acts spinally,
while as an infusion
it is said to exert a systemic effect.

Question 8

Side effects of neuraxial opioids

Answer 8

Side effects of neuraxial opioids include 
pruritis, 
urinary retention,
nausea
 and delayed respiratory depression

Question 9

Doses epidural / spinal

fentanyl morphine

Answer 9

Spinal:
morphine 100–200 μg,
fentanyl 10–25 μg

Epidural:
morphine 40 μg/kg,
fentanyl 1–2 μg/k

Question 10

What is the effect of adding vasoconstrictors

How is this mediated

How are the analgesic affects mediated

Answer 10

Addition of vasoconstrictors 
helps in reducing total dose, 
hastens onset
and 
prolongs duration of action of LAs. 

Although this is mediated post synaptically

(via α1 and α2 receptors),

the intrinsic analgesic effect is
mediated through presynaptic α2 receptors.

Question 11

What is the effect of adding vasoconstrictors

How is this mediated

How are the analgesic affects mediated

Answer 11

Addition of vasoconstrictors 
helps in reducing total dose, 
hastens onset
and 
prolongs duration of action of LAs. 

Although this is mediated post synaptically

(via α1 and α2 receptors),

the intrinsic analgesic effect is
mediated through presynaptic α2 receptors.

Question 12

Epidurally administered adrenaline differs how

Answer 12

produces mild vasodilatation
in typical doses. Mean

arterial pressure (MAP) is decreased, 
while the cardiac output (CO) rises. 

Higher doses result in increased MAP and a fall in CO.

Question 13

Why not suitable for Ambulatory

Answer 13

In ambulatory settings,
return of bladder function and discharge is
delayed, limiting its usefulness.

Question 14

Addition of adrenaline to
bupivacaine or ropivacaine

How does it affect

Answer 14

Addition of adrenaline to
bupivacaine or ropivacaine

does not prolong action
to the extent that it prolongs
the action of lignocaine.

Question 15

Adrenaline to chloroproacine

Answer 15

Addition of adrenaline to
chloroprocaine causes flu-like symptoms.
Hence this is not advocated.

Question 16

Dose of

Adrenaline added to regional

Phenylephrine

Answer 16

Doses:
1 : 200,000 or 5 μg/mL of adrenaline

or 0.2 mg phenylephrine

Question 17

What class of drug is clonidine

How does Clonidine mainly

Answer 17

Alpha-2 adrenergic agonists like clonidine

act pre-synaptically to reduce
the nociceptive input at spinal level.

Question 18

where else does clonidine act

What adverse effects does this cause

Answer 18

In addition, 
they reduce central sympathetic drive 
by action on 
locus ceruleus and
nucleus tractus solitarius. 

Hence they produce sedation,
dry mouth,
hypotension
and bradycardia as main adverse effects.

Question 19

Clonidine lipophilic or hyrdophilic

where does it act

synergistic or antagonistic to opioids

Answer 19

Though highly lipophilic,

they act spinally,

acting synergistically with opioids.

Question 20

How does clonidine affect GA dose

Is it suitable for Ambulatory settings
Why

Answer 20

They may reduce anaesthetic
requirements when combined
with general anaesthesia.

Because they lack
respiratory depression
pruritis
and cause less urinary retention,

they may be better for
ambulatory settings.

Question 21

Neuraxial dose clonidine

Answer 21

Doses:
Spinal: usual dose 2 μg/kg
Low dose: 1.5 μg/kg

Question 22

How are LAs prepared

What is the pH of LA

Answer 22

Because local anaesthetics are
available as solutions of
hydrochloride salts

the resultant pH falls to 3.5–4

Question 23

How does adding Bic to LA affect

Answer 23

Addition of bicarbonate to
such solutions results in

increasing pH toward pKa
and
increases the fraction of free base present.

Question 24

What does addition of Bic do to epidural anaesthesia

Is this seen with all LA

Answer 24

This hastens the onset
and
may intensify epidural anaesthesia.

This has not been seen
with ropivacaine.

Question 25

How does addition of Bic affect adrenaline

What side effects can this cause

Answer 25

Restoration of pH towards pKa 
improves adrenaline action, 
and
alkalinisation of adrenaline 
containing LA solutions 

may result in hypotension
(secondary to higher concentration
of LA produced by adrenaline).

Question 26

How much Bic should be added

why can this be a problem

Answer 26

Doses:
Lignocaine: 1 mL of NaHCO3 per 10 mL of solution.
Bupivacaine: 0.1 mL of NaHCO3 per 10 mL of solution

Excessive carbonation may precipitate LAs; hence the following limits are prescribed.

Question 27

Liposomal morphine effect

Answer 27

Liposomal morphine can produce

long-lasting analgesia (2 days)
when given epidurally.

Question 28

effect when Liposomal morphine added to LA

Answer 28

However, it should not be given
along with local anaesthetics,

as this may cause early and
uncontrolled release of morphine,

causing loss of advantage and
occurrence of adverse effects.

Question 29

Intrathecal neostigmine effect

Answer 29

Intrathecal neostigmine
produces analgesia by

reducing acetylcholine breakdown
(it is an analgesia at spinal level),

but is limited by

hypotension and nausea.

Question 30

Epidural ketamine

Intrathecal Ketorolac

What are their effects
are they above safe
are they used

Answer 30

Epidural ketamine
and
intrathecal ketorolac

have not shown neurotoxicity in animal studies.

Question 31

Intrathecal midaz

What are their effects
are they above safe
are they used

Answer 31

Intrathecal midazolam
is effective analgesia,

but again,

neurotoxicity profile has
yet to be evaluated

Question 32

Which agents are known to effective as LA Adjuncts in

PNB

Answer 32

The agents shown to be effective as adjuncts
with local anaesthetics in
peripheral nerve blocks include

clonidine, 
dexamethasone,
buprenorphine
and 
tramadol.

Question 33

What have been show to be effective in IVRA

Answer 33

Magnesium,
ketorolac and
clonidine are effective in
intravenous regional anaesthesia.

Question 34

What is effective when infiltrated @ donor bone graft site

Answer 34

Morphine
reduces donor-site bone pain
when infiltrated at the donor
bone graft site.

Question 35

What agents are affective intra articular

Answer 35

Intra-articluar
morphine,
clonidine,
neostigmine and ketorolac

have produced prolonged analgesia.