ملخص

Drugs in Anesthesia are given:

1- Before surgery

2-During surgery:

3-After surgery:

A- Anxiolysis and Amnesia.

A-Induction: Usually IV (Pre-Oxygenated patient)
-Small doses of opiates
-Fentanyl
-Followed by Thiopental (Ultra short acting Barbiturate)
or: Propofol
a-Patient is not left alone until consciousness regained

B-Analgesia for patient in pain.

Or to:
Prevent post operative pain


Endotracheal tube insertion require paralysis
with Neuromuscular Block

b-Effect of neuromuscular blockade either wane off or reverted by Antidote.

C-Drying of bronchial secretions.
Anti muscarinic drugs Rarely used
Glycopyrronium is used one hour before surgery
Gastric content can lead to pulmonary aspiration:
-Single dose of anti acid
-Ranitidine
-Metoclopramide

B-Maintenance: (Inhalation)

-Nitrous oxide (N2O) and Oxygen
-Volatile agents +Oxygen + Air.
-Isoflurane
-Sevoflurane
-Halothane

c-Relief of pain

Mode of action:
On brain primarily on midbrain reticular formation system.
Lipid solubility is important as the more lipid soluble is the drug the more its effect on the brain.
Individual Anesthetics:
1-Gases and Volatile Agents: (Inhalation anesthesia)
*Agents with law solubility in blood provide rapid effect with rapid elimination
-N2O (Nitrous Oxide)
-Sevoflurane

Nitrous Oxide (N2O):

-Strong Analgesic action
-Recovery is very fas Around 4 minutes
Adverse reactions:

Contra indications of Nitrous Oxide (N2O):

Uses:

Disadvantages of Nitrous Oxide : (N2O)

-Nausea and vomiting
*When used for more than 4 hours
-Megaloblastic changes in blood.
-Teratogenicity to staff
-Any closed distended air filled space will expand
-Intra ocular surgery
-Middle ear
-lung
Use d to maintain surgical anesthesia with other agents e.g. Isoflurane 1-
2-Maintain anesthesia mixed with at least 30 % O2


Must be used with more potent drug to produce surgical anesthesia.-
-Post operative nausea and vomiting

Halogenated anesthetics:

(Volatile Agents)
-Halothane
-Isoflurane
-Sevoflurane

Halothane

Sevoflurane
Isoflurane:

-Slow recovery

-Decrease cardiac output
-Sensitize heart to catecholamine (Arrhythmia)
-induce liver enzymes
-Fever, anorexia, nausea, vomiting
Chemical analogue to Isoflurane
Enflurane causes more respiratory depression


Effects of Isoflurane:
-Respiratory depression
-Increased respiratory rate and tidal volume
-Can cause bronchial irritation
CVS:
-Slight depression in CVS
-And cardiac output
-Reduce Blood Pressure and peripheral vasodilatation.

Oxygen in anesthesia:

-Supplementary O2 is always useful
-With inhalation agents to prevent hypoxia
O2 concentration is 30%.... not exceed 80 %

Intravenous anesthesia:

Extremely rapid induction
*It is common practice to use iv induction and inhalation agents for maintenance.
Propofol:
-Inductions within 30 sec
-Recovery is rapid


Thiopental (Pentothal) :
-Very short acting barbiturate
-Induces anesthesia smoothly
-Half life = 4 min allows swift recovery after a single dosage
-Terminal half = life is 11 hours very prolonged recovery after repeated dosage or infusion

CNS:

-No analgesia
-Decrease intracranial pressure
CVS:
-Hypotension
-Tachycardia
-Decrease respiratory rate

Ketamine (Ketalar):

-Analgesia 15 min after a single IV injection
Used for Minor surgical interventions
Has an advantage in Shocked patients as it induce
Tachycardia
*Increased blood pressure
Cardiac output
Bronchodilatation.
Disadvantages of Ketamine:
-No muscle relaxation
*Increase intracranial and intra ocular pressure
-Hallucination during recovery


Contra indication of Ketamine:
-Hypertension
-Congestive cardiac failure
-Cerebral trauma
-Increased intracranial pressure
-Pregnancy (Contra indication in pregnancy)

Muscle relaxants in Anesthesia:

Abdominal surgery requires muscle relaxation
(Deep general anesthesia can cause relaxation)
Mechanical ventilation is always used
Neuromuscular block should only be given after induction of anesthesia

2- By Depolarization: as Suxamethonium = Succinylcholine

1- Competitive relaxants as Atracurium and Tubocurarine:

Shortest duration of action

Tracheal intubation in less than 60 sec
Total paralysis for 4 minutes
If intubation is impossible recovery is rapid
-Muscle fasciculation then paralysis
-Muscle pain 1-3 days
Most rapid onset


-Competitive antagonists to ach.
-Flaccid paralysis
Reversal of anticholinesterases drugs is by
Neostigmine
With Atracurium
Full blockade after 3 min
20-30 min duration
Tubocurarine:
Can cause Hypotension

Antagonism of Neuromuscular Blocking agents:

-Anti cholinesterase drugs
Neostigmine IV + Glycopyrronium or Atropine
To prevent bradycardia due to parasympathetic action of Neostigmine

Mode of action of local anesthesia:

1-Prevent the initiation and propagation of the action potential (nerve impulse)
2-Reducing the passage of sodium through voltage gated sodium channel
3-They rise the threshold for excitability and block conduction


** By infiltration local anesthesia act within 5 min And have a useful duration of effect for 1-1.5 h Can be doubled by vasoconstriction
Absorption of topical anesthesia on mucus membrane can be extremely rapid and give plasma concentration comparable to injection *This is important specially in urethra

Chemical classification of local anesthetics:

1-Esters:
Cocaine, Procaine,
2-Amides:
Lignocaine (Xylocaine) Lidocaine

Effect is terminated by removing the local anesthetic from the circulation.

Delaying this will increase the duration of action of L.A and decrease systemic absorption.
Addition of epinephrine (Adrenaline) increase the duration of lidocaine ,, Never use adrenaline in Extremities = fingertips Nose , toes, ..etc

Uses of local anesthesia:

1- Surface anesthesia: solution jelly cream
2- Infiltration anesthesia
3- Regional anesthesia
-Nerve block
-Intravenous regional anesthesia
-Epidural anesthesia
-Intrathecal ( Spinal anesthesia)