Autonomic Nervous System Part Dieu
Jan 16, 2016
Autonomic Nervous System
Part Dieu
Atropine
Anticholinergic,
Parasympatholytic
comes from ”belladonna” plant
Figure 1a Schematization of the Nervous System
Nervous System
PNSPNS
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
If receptor responds to acethylcholine
= muscarinic or nicotinic
If receptor responds to norephinephrine or epinephrine
= adrenergic
ACHNOREPI
EPI
adrenergic
muscarinic
nicotinic
Sympathetic Parasympathetic
Preganglionic Preganglionic
Acetylcholine Acetylcholine
Nicotinic receptor Nicotinic receptor
Postganglionic Postganglionic
Norepinephrine Acetylcholine
Adrenergic receptor Muscarinic receptor
Competitive Actions of Atropine
Atropine competes and binds the muscarinic receptor sites thus preventing ACH from binding to that site.
Atropine Acetylcholine
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 overdosesAtrovent (Impratropium) which is a mixture of atropine and Ventolin
(blocks muscarinic effects)
Anticholinergic Overdose
Mnemonic Rationalered as a beet Peripheral ganglionic blockade of nicotinic receptorsdry as a bone Cholinergic nerves supply the sweat glands, anticholinergics can
decrease or abate their activity.blind as a bat The sphincter muscle of the iris and the ciliary muscle are
innervated by cholinergic nerve fibers. The sphincter muscle is notable to contract normally, the radial muscle causes the pupil todilate. The patient is unable to focus (accommodate).
mad as ahatter
Anticholinergics block cholinergic pathways and receptors in theCNS. This results in manic behavior and excitement.
hot as a hare The inhibition of sweat glands causes the patients body temperatureto 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
Epinephrine
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
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 Beta Receptor Vasoconstriction Vasodilatation (B2) Iris Dilatation Cardioacceleration (B1) Intestinal relaxation Increased myocardial strength (B1) Intestinal sphincter contraction Intestinal relaxation (B2) Pilomotor contration Uterus relaxation (B2) Bladder sphincter contraction Bronchodilatation (B2) Calorigenesis (B2) Glycogenolysis (B2) Lipolysis(B2) Bladder wall relaxation(B2)
Therapeutic Uses
Most widely used drug in cardiac arrest setting refractory asthmaanaphylaxissevere hypotension unresponsive to dopamineEpinephrine is used extensively in the resuscitation of children (2-10mcg)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
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) 2-10mcg/min IV
Special Prehospital Concerns
Epinephrine can be administered in via IV, ETT, SC, bolus or infusionideal 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 cAMPcauses 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
#2Increase in cAMP
#3Activates chloride channels. Aschannels open Chloride ions enter.Sodium is drawn in to maintain ionicbalance.
#1Ventolin
#4H2O followssodium
Therapeutic Uses
Therapeutic UsesVentolin 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 EffectsAdverse Effects•nervousnessnervousness• tremorstremors• agitationagitation• dizzinessdizziness• palpitationspalpitations• headacheheadache• tachycardia tachycardia •nauseanausea.•allergic reactions include angioedema, allergic reactions include angioedema, urticaria, bronchospasm, hypotension, rash urticaria, bronchospasm, hypotension, rash and anaphylaxisand anaphylaxis•Overdosage may cause tachycardia, cardiac Overdosage may cause tachycardia, cardiac arrhythmias, hypertension, hypokalemia and arrhythmias, hypertension, hypokalemia and in extreme cases, sudden deathin extreme cases, sudden death
Dose: Salbutamol via Nebulizer: <10kg – 1.25 mg 10 – 30 kg – 2.5 mg >30 kg – 5.0 mg
Salbutamol via MDI0-2 years: 1 puff followed by 4 breaths, repeat this 3 times2-5 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
Dosage -Adult and Pediatric
Special PreHospital Concerns
administered by MDI (metered dose inhaler) or by nebulizer mask driven by oxygen or air. Aerochamber is betterTo test how full an MDI container is -see figure
Drug Profile
Barbituates act by suppressing impulses to the limbic system and the RASAlso act by augmenting GABA inhibitory effect throughout the entire brainResult can be a profound depression in consciousness
Adverse Effects
Low doses –euphoria, Respiratory depressionDiminished reflexes and motor responseUnconsiousnessDeathHypotension
Other CNS Depressants
Alcohols – common use Methanol, ethanol, choral hydrate
Paraldehyde – older use, ETOH withdrawalAntihistamines – 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 82-95Stimulants (antidepressants) Chapter 9 – 114-131
Common prescription Drugs Do YOU know your drugs?