Opiods in Anesthesia

7/30/2019 Opiods in Anesthesia

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Opioids in anesthesiaOpium derived from dried juice of

poppy plant which contains over 20

plant alkaloids.including morphineand codiene.


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NARCOTIC AGONISTS

Site of Action *Opioid receptors are predominantly located

in the:

1-Brain stem (amygdala,corpus

striatum,periaqueductal gray matter and

medulla)

2-spinal cord (substantia gelatinosa).

3- GIT


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They act on 3 types of receptors: *

1. Mu receptors:analgesia,respiratorydepression,euophoria,and physical

dependence. 2.Kappa

receptors:analgesia,sedation,respiratorydepression,miosis.

3.Segma :dysphoria,hallucination,tachypnea,tachycardia.


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PHARMACOKINETICS -Rapied distribution through the body

following IV injection.

-It is metabolised by the liver and the majority

of the inactive metabolites are excreted

unchanged in the urine.


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PHARMACODYNAMICS

CNS: Opioids sedate through interfering with

sensory perception of painful stimuli.

**large doses produce unconsciousness but

they are generally incapable of producinganesthesia and it can not guarantee totalamnesia.

It may produce nausia & emesis throughstimulation of the chemoreceptor triggerzone.


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RESPIRATORY They result in dose related depression of

respiratory rate and minute volume.but

increase the tidal volume which will lead to a

slow deep respiration.Reversed by Naloxone

adminstration.


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CVS Opioids have litle myocardial depressant effect even

when adminstrated in high doses.

Supplementation with either N2O or Benzodiazepinesmy depress cardiac output.

They decrease systemic vascular resistance either bydecreasing sympathetic outflow or by releasinghistamine ( as Morphine) which producesvasodilatation & decrease SVR.

Synthetic opioids are less likely to release histamine.

They lead to bradycardia by stimulation vagal nucleusin the brain stem.


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GIT *Narcotics slow GI mobility and may result in

constipation or post operative ileus.

**increases biliary tract tone which may lead

to biliary colic eith patients with bile stones.


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OTHERS ***Increases the bladder sphincters tone.

And urine retention

***Anaphylactic

reactions,bronchospasm,chest wall regidity

and pruritis.


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FENTANYL & MORPHINE Fentanyl is the most commonly used during

induction of anesthesia due to its rapied

onset(highly lipid solubility)and predictable

duration of action about 30 minutes

**Morphine is used in the preioperative

period to provide long lasting analgesia.and it

should be adminstrated slowlyat a rate< 5mg/min to avoid excessive histamine release.


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Low doseAnalgesic

dose

Potency

Ratio

0.05-0.2mg/kg10 mg1Morphine

0.5-3 mic

g/kg

100

mcg

100Fentanyl


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NARCOTIC ANTAGONISTS NALOXONE:

It competes at the mu,delta,kappa andsigma receptors.

Peak effect 1-2 minutes. Duration of action 30-60 min.

Indicated in perioperative surgical

patientsnwith excessive sedation orrespiratory sedationnsecondary toopioids.


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Given in small incremental doses.

High doses of naloxone will result in sudden

reversal of analgesiac effects leading to abrupt

tachycardia,pulmonary edema,arrythmias and

cardiac arrest.


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THANK YOU

Opiods in Anesthesia

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