Autonomic Nervous System Part Dieu Atropine Anticholinergic, Parasympatholytic comes from ”belladonna” plant.

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?