فارماکولوژی در مداخلات توسط پزشک درد - PowerPoint Presentation

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فارماکولوژی در مداخلات توسط پزشک درد

علیرضا احمدی

متخصص بیهوشی، فلوشیپ درد

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Categories

Radiographic contrast agents

Local anesthetics

Corticosteroids

Topical antiseptics

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RADIOGRAPHIC CONTRAST AGENTS

Iodinated

contrast media (

ICM

)

Clinically used agents have between 180 to 400 mg/ml of

iodine

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Side Effects

Osmotoxic reactions including:

Pain on injection

Hemolysis

Endothelial damage (capillary leak and edema)

Vasodilation (flushing, warmth, hypotension cardiovascular collapse)

Hypervolemia

Direct cardiodepressive effects

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PHARMACOLOGY

Ionic ICM:

are strictly

contraindicated

for all applications involving the central nervous system (

CNS

) and may cause severe or fatal neurotoxic reactions following intrathecal administration

.

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PHARMACOLOGY

Non-ionic

ICM:

are the agents of choice for interventional pain procedures due to their

lower osmolality

and

toxicity

.

Elimination

is by glomerular filtration without reabsorption and there is virtually no metabolism.

(normal 2

hr

)

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ADVERSE REACTIONS

Anaphylactic

or

anaphylactoid

symptoms of severe

bronchospasm,

laryngeal

edema, angioedema, pulmonary

edema,

hypotension

, convulsions, cardiac dysrhythmias, or

arrest occur

with an incidence of

0.2% to 0.06%

for

high osmolar

agents and at 5 times lower incidence for

low osmolar

agents.

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ADVERSE REACTIONS

Risks:

prior

reaction to ICM

, and with underlying disease including

asthmatics

, history of

atopy

, and

advanced heart disease

) If suspected these reactions need to be treated with

oxygen, intravenous fluids, antihistamines -H1 and H2 blockers-, adrenergic drugs –epinephrine-, and corticosteroids

, and full cardiopulmonary resuscitation as needed.

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PREVENTION STRATEGIES FOR

ADVERSE REACTIONS

Ionic

ICM

have 4

times the incidence of these reactions compared to

nonionic agents

.

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LOCAL ANESTHETICS

Mechanism

of effects: blocking sodium

channels

located

Esters

: there is relatively rapid breakdown by plasma cholinesterase to a common metabolite, para-amino-benzoic acid (PABA) with the exception of cocaine, which has an alternate metabolic pathway.

Amides

: LAs are metabolized by the cytochrome P450 system and conjugation as a route to elimination.

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CHEMICAL

COMPOSITION AND

CLASSIFICATION

The factors

influencing the speed of onset include

:

The

addition of

bicarbonate

Epinephrine-containing

The

concentration

of LA

Amount

of LA

The

anatomic

location

of

injection

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Ropivacaine,

is

stated to

be

1.

More motor

sparing

than bupivacaine and

2. Less cardiotoxicity

at equipotent

doses

.

CHEMICAL COMPOSITION AND CLASSIFICATION

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Mixtures

of LAs to produce quick onset and/or a

prolonged duration

have been intermittently

advocated:

bupivacaine/lidocaine

or

ropivacaine/lidocaine

vs bupivacaine

or ropivacaine alone

provides a quicker onset

but shorter

duration of

action.

CHEMICAL COMPOSITION AND CLASSIFICATION

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Studies

on

epidural

use

suggest

no

significant difference

when used in combination

in terms

of speed of onset or change in duration of

action.

CHEMICAL COMPOSITION AND CLASSIFICATION

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Local toxicity

can also occur with

intraneural

injections

even with

normal concentrations.

Systemic

toxicity

(

7

to

20/10,000)

for

peripheral nerve

blocks and 4/10,000 for epidural

blocks.

1

. CNS symptoms

consist

of

metallic taste, perioral numbness,

dizziness, muscle

twitching, and ultimately generalized

seizures.

2. Toxic

cardiovascular

effects include

arrhythmias,

cardiac depression

, vasodilation, hypotension, and cardiac

arrest/ collapse.

ADVERSE REACTIONS

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The

potent

lipophilic LAs are more

cardiotoxic

(20

%

intralipid

has

been shown to be effective for resuscitation

from bupivacaine-induced

cardiac toxicity

.)

20% intralipid

with a bolus of 1.2 to 2.0 ml/kg followed by

infusion of

0.25 to 0.5 ml/kg.

ADVERSE REACTIONS

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CORTICOSTEROIDS

Classified into

three functional

groups:

Mineralocorticoids,

Glucocorticoids

Adrenal androgens

.

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Inhibit the production of local

inflammatory

mediators.

Reduced spontaneous

ectopic discharge

rates seen following nerve injury, including in

neuromas

.

Reversible

inhibition of nociceptive C-fiber

transmission, but not A-B fiber transmission, has been shown following corticosteroid

application

.

Glucocorticoid

receptor sites have been located on noradrenergic and 5-hydroxytryptamine

neurons within the dorsal horn substantia

gelatinosa

—known pathways of pain transmission.

Mechanisms

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Serious adverse

events:

1.

Transforaminal epidural

injections with

particulate corticosteroid solutions. An

inadvertent injection

of a steroid particulate into the

artery of

Adamkiewicz

during

thoracic or lumbar transforaminal

epidural steroid

injection could result in

spinal cord ischemia

leading to

profound lower extremity motor deficits

,

even

paraplegia

.

CORTICOSTEROIDS

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2

.

Cervical

level

transforaminal

steroid

injection

(injection

of a particulate corticosteroid into

a

radicular

artery or vertebral artery

.)

3.

Similar but lower

rates of

infarction have been reported with

lumbar

transforaminal injection

or particulate corticosteroid.

Anecdotally, no serious adverse event has been reported following injection of a

nonparticulate

steroid.

CORTICOSTEROIDS

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Sterile meningitis

and

arachnoiditis

have been reported

following intrathecal

injection of methylprednisolone,

although these

may possibly be related to the polyethylene

additive of

the preparation

.

Brief

euphoric or manic

reactions

have

been reported following high-dose

conticosteroid therapy.

Although

rare,

analphylactoid

reactions

have been reported following intravenous,

intramuscular, and

soft-tissue

conrticosteroid

injections. (supportive

therapies (i.e

.,

airway

, breathing, circulation, supplemental oxygen

), including

advanced cardiac life support guidelines

when indicated)

ADVERSE REACTIONS

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Infections

relatively rare:

epidural abscess

,

discitis, osteomyelitis

, and

meningitis

.

Infection control:

selection of

the skin antiseptic agent

.

meticulous

hand washing

,

skin

preparation

,

instrument

sterilization

,

strict aseptic technique

,

and

timely

antibiotic prophylaxis

when indicated.

SKIN ANTISEPTIC AGENTS

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Products containing

iodophors and

chlorhexidine gluconate

. Additionally, agents are further classified as

either

aqueous-based

or

alcohol-based

solutions.

Aqueous-based iodophors

, such as povidone-iodine, can be safely used

on mucous

membrane surfaces.

Alcohol-based

solutions offer

a quicker

onset and often more sustained antimicrobial

activity.

SKIN ANTISEPTIC AGENTS

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