Transcript Autonomic Nervous System

Autonomic Nervous System
Part Dieu
Atropine
Anticholinergic,
Parasympatholytic
comes from ”belladonna” plant
Figure 1a Schematization of the Nervous
System
PNSPN
S
Nervous
System
PNS
How autonomic drugs work
ANS transmits nerve impulses from the CNS
to the effector organs over efferent neurons
(preganglionic or postganglionic)
Effector organs are the heart, smooth muscle
and exocrine glands.
Neurotransmittor at effector organ
determines type of neuron
norepinephrine or epinephrine=adrenergic
(sympathetic)
acethylcholine = cholinergic (parasympathetic)
Receptors
NOREPI
ACH
EPI
If receptor responds
to acethylcholine
= muscarinic or
nicotinic
If receptor responds
to norephinephrine
or epinephrine
= adrenergic
muscarinic
nicotinic
adrenergic
Sympathetic
Preganglionic
Acetylcholine
Nicotinic receptor
Postganglionic
Norepinephrine
Adrenergic receptor
Parasympathetic
Preganglionic
Acetylcholine
Nicotinic receptor
Postganglionic
Acetylcholine
Muscarinic receptor
Competitive Actions of
Atropine
Atropine competes and binds the muscarinic receptor sites thus preventing
ACH from binding to that site.
Acetylcholine
Atropine
Muscarinic Receptor Site
Theraputic Uses of Atropine
to increase the heart rate in
symptomatic bradycardia
reduce hyperactivity and spasms of the
GI tract and bladder
used in ophthalmology to cause
mydriasis (pupil dilation)
Atropine is used to treat
organophosphate overdoses
Atrovent (Impratropium) which is a
mixture of atropine and Ventolin
(blocks muscarinic effects)
Anticholinergic Overdose
Mnemonic
red as a beet
dry as a bone
blind as a bat
mad as a
hatter
hot as a hare
Rationale
Peripheral ganglionic blockade of nicotinic receptors
Cholinergic nerves supply the sweat glands, anticholinergics can
decrease or abate their activity.
The sphincter muscle of the iris and the ciliary muscle are
innervated by cholinergic nerve fibers. The sphincter muscle is not
able to contract normally, the radial muscle causes the pupil to
dilate. The patient is unable to focus (accommodate).
Anticholinergics block cholinergic pathways and receptors in the
CNS. This results in manic behavior and excitement.
The inhibition of sweat glands causes the patients body temperature
to rise.
Special Prehospital Concerns
Atropine should be given in
doses of 0.5mg except in
cases of bradyasystolic arrest
Atropine should be used with
extreme caution in the setting
of myocardial infarct
second-degree type II and 3
degree heart block with wide
QRS complexes,
transcutaneous pacing is a
preferred method of therapy
Epinephrine
Adrenergic Agonist
Sympathomimetic
Drug Profile
naturally occurring catecholamine that is produced in
the body and released by the adrenal gland
Epinephrine can be considered the emergency
hormone and norepinephrine is mainly the
transmitter hormone
stimulates adrenergic neurons to bring about the
various effects on the body
Epinephrine
Pharmacokinetics
Both Alpha and Beta-receptors are stimulated by
epinephrine.
Epinephrine is a “direct acting” adrenergic agonist
It is metabolized primarily by enzymes in the
synaptic cleft
Pharmacokinetics of Epi
Cardiovascular Effects
  SVR
 B/P
 Electrical activity in the
heart
 cerebral and coronary blood
flow
 strength of myocardial
contraction
 MVO2
 automaticity
Adrenergic Receptor
Response to Epi
Alpha Receptor
Vasoconstriction
Iris Dilatation
Intestinal relaxation
Intestinal sphincter contraction
Pilomotor contration
Bladder sphincter contraction
Beta Receptor
Vasodilatation (B2)
Cardioacceleration (B1)
Increased myocardial strength (B1)
Intestinal relaxation (B2)
Uterus relaxation (B2)
Bronchodilatation (B2)
Calorigenesis (B2)
Glycogenolysis (B2)
Lipolysis(B2)
Bladder wall relaxation(B2)
Therapeutic Uses
Most widely used drug in cardiac
arrest setting
refractory asthma
anaphylaxis
severe hypotension unresponsive to
dopamine
Epinephrine is used extensively in
the resuscitation of children (210mcg)
an additive in local anaesthetic
agents to help cause
vasoconstriction
Adverse Effects
Overdose is unlikely as the
drug is quickly metabolized
Increased HR/BP,Sweating
increase MVO2 demands
and have to given with
caution to those patients
with ischemic heart disease
Dosage/Supplied
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Adult- For anaphylactic reactions
(1:1,000) 0.3mg subcutaneous.
For Cardiac arrest 1:10,000 1mg IV
q 3-5 mins. 2mgs ETT q 3-5 mins.
Pediatric- For anaphylactic
reactions (1:1,000) 0.01mg/kg
max 0.3mg
For severe hypotension (shock) 210mcg/min IV
Special Prehospital Concerns
Epinephrine can be
administered in via IV,
ETT, SC, bolus or infusion
ideal dose of epinephrine
epinephrine infusion,. and
titrate to effect
Epinephrine is light
sensitive
Salbutamol
Adrenergic agonist (beta-2)
Bronchodilator
Drug Profile (FYI – Do not
memorize!)
beta agonists are thought to
work is by increasing the
intracellular concentrations of
cAMP
causes epithelial chloride
channels to open
As the chloride ions move they
draw sodium ions along with
them. The  in sodium ions
create a gradient to draw water
along with them. This  in water
acts to lubricate the mucous
How it works
#1
Ventolin
#2
Increase in cAMP
#4
H2O follows
sodium
#3
Activates chloride channels. As
channels open Chloride ions enter.
Sodium is drawn in to maintain ionic
balance.
Therapeutic Uses
Therapeutic Uses
Ventolin is used to treat bronchospasm
brought about from a number of factors.
The fact that Ventolin is predominantly a
beta 2 receptor stimulator, the effects on the
beta 1 receptors of the heart are minimal.
Adverse Effects
•nervousness
• tremors
• agitation
• dizziness
• palpitations
• headache
• tachycardia
•nausea.
•allergic reactions include angioedema, urticaria,
bronchospasm, hypotension, rash and anaphylaxis
•Overdosage may cause tachycardia, cardiac
arrhythmias, hypertension, hypokalemia and in extreme
cases, sudden death
Dosage -Adult and Pediatric
Dose: Salbutamol via Nebulizer:
<10kg – 1.25 mg
10 – 30 kg – 2.5 mg
>30 kg – 5.0 mg
Salbutamol via MDI
0-2 years: 1 puff followed by 4 breaths, repeat this 3 times
2-5 years: 1 puff followed by 4 breaths, repeat this 4 times
5-8 years: 1 puff followed by 4 breaths, repeat this 6 times
> 8 years: 1 puff followed by 4 breaths, repeat this 8 times
Special PreHospital Concerns
administered by MDI
(metered dose inhaler)
or by nebulizer mask
driven by oxygen or air.
Aerochamber is better
To test how full an MDI
container is -see figure
Drug Profile
Barbituates act by suppressing impulses
to the limbic system and the RAS
Also act by augmenting GABA inhibitory
effect throughout the entire brain
Result can be a profound depression in
consciousness
Adverse Effects
Low doses –euphoria,
Respiratory depression
Diminished reflexes and motor response
Unconsiousness
Death
Hypotension
Other CNS Depressants
Alcohols – common use

Methanol, ethanol, choral hydrate
Paraldehyde – older use, ETOH withdrawal
Antihistamines – Benadryl, Gravol (side
effects)
Side effects of many non-CNS drugs
Prehospital Administration
Versed
Phenobarb
Ativan
Gravol
Valium
Narcotics
For Next Class
Please read Chapter 7 pages 82-95
Stimulants (antidepressants)
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Chapter 9 – 114-131
Common prescription Drugs
 Do YOU know your drugs?