Intravenous Anaesthetic Agents drugs.pptx

Intravenous
Anaesthetic Agents
intravenous anaesthetic agents/anesthesiology/184-244 1

What are General Anesthetics?
• A drug that brings about a reversible loss of
consciousness
• generally administered by an
anesthesiologist in order to induce or
maintain general anesthesia to facilitate
surgery.

Routes for Delivery of General
Anesthetics
• Intravenous (IV)
• Inhalational

Induction
intravenous
Faster onset
avoiding the
excitatory
phase of
anaesthesia
inhalational
where IV
access is
difficult
Anticipated
difficult
intubation
patient
preference
(children)

Types of General Anesthetics
• Induction agents
• Induction agents usually administered IV
• can be inhalational for those who do not tolerate IV access
• Maintenance agents
• Maintenance agents usually administered inhalationally or IV with bolus
or continuous infusion technique

Structural formulas of anesthetic drugs

IV Anaesthetic Agents
• Barbituates (Thiopentone sodium)
• Benzodiazepines ( Diazepam, Midazolam)
• Propofol
• Ketamine
• Etomidate

Intravenous Anaesthetics
• Primary role as induction agents
• Maintenance with total intravenous anesthesia
• Rapid redistribution
• Shorter half lives
• Environmental risk of inhalational agents
• Rapid distribution to vessel rich tissue

• High lipid solubility allows for rapid induction
• When redistributed out of the brain, effect
decreases
• Advantages
• Rapid and complete induction
• Less CV depression

• Most exert their actions by potentiating GABAA receptor
• GABAergic actions may be similar to those of volatile
anesthetics, but act at different sites on receptor

• Most decrease cerebral metabolism and
intracranial pressure
• Most cause respiratory depression
• May cause apnea after induction of anesthesia
• Barbiturates, benzodiazepines and propofol
cause cardiovascular depression

Benzodiazepines
Rarely used alone for general anesthesia
• Cannot easily induce and maintain general anesthesia
• Lack analgesic properties
Used for sedative and amnestic effects

Benzodiazepines (Diazepam, Midazolam)
Indications:
1. Sedation during regional anesthesia
2. Radiological procedures (children, anxious persons)
3. Endoscopy
4. ICU
5. Supplementation to general anesthesia
6. Amnesia
7. Status epilepticu

Benzodiazepines (Diazepam, Midazolam)
Adverse effects:
1. Prolong duration (diazepam)
2. Painful on injection (diazepam)
3. Hypotension if used with other agents like opioids
4. Dependence
5. Respiratory depression in over dosage
Contraindications:
Early pregnancy (teratogenic effect)

Barbiturates (thiopenton or thiopental)

• greater potency,
• more rapid onset of action, and shorter durations
• of action (after a single “sleep dose”)
• Effect terminated not by metabolism but by
redistribution

Indications:
1. Induction of anesthesia
2. Maintenance of anesthesia (but has cumulative effects)
3. Treatment of status epilepticus
4. Reduction of intra-cranial pressure (ICP)

Adverse effects:
1. Hypotension
2. Respiratory depression
3. Tissue necrosis (if injected extra-vascular)
4. Laryngospasm
5. Bronchospasm (avoid in asthma)
6. Thrombophlibitis (less common in 2.5% conc.)
7. Allergic reactions 1 in 14000-20000
8. Intra-arterial injection (lead to sever
vasospasm and sever pain it may lead to
gangrene of the limb, treatment by keeping the
cannula in and inject papeverine 20 mg,
heparin and fluid, using 2.5% conc. Is safer)

Contra indications:
1. Airway obstruction (epiglottis or pharyngeal
tumours)
2. Porphyria
3. Previous hypersensitivity to this drug

Propofol

Indications:
• Induction of anesthesia when rapid early recovery of
consciousness is indicated
• Sedation during regional anesthesia
• Sedation in ICU
• Total intravenous anesthesia
Adverse effects:
• Cardiovascular depression
• Respiratory depression
• Excitatory phenomena (convulsion, myoclonus)
• Pain on injection
• Allergic reaction
Contra indication:
• Airway obstruction
• Hypersensitivity

Ketamine
• NMDA Receptor Antagonist
• usually stimulate rather than depress the circulatory system
• Dissociate anaesthesia
• Analgesia

Indications:
• Shocked patient
• Paediatric anesthesia
• Difficult locations (at accident site, wars)
• Analgesia And sedation (wound dressing change)
• In ICU
• In developing countries (where anesthesia equipments and trained staff are in short
supply)
Adverse effects:
• Emergence delirium, nightmares and hallucinations
• Hypertension and tachycardia
• Prolong recovery
• Salivation
• Increase intra-cranial pressure

Etomidate
Indications:
• Used in patient with cardiovascular disease (cardiovascular
stable)
• Suitable for out patient anesthesia

Adverse effects:
• Excitatory phenomena (involuntary movements,
hiccups, cough)
• Pain on injection
• Nausea and vomiting
• Venous thrombosis
Contraindications:
• Airway obstruction
• Porphyria
• Adrenal insufficiency
• Long term duration

Inhalation Anesthetics
Nitrous oxide
• Halothane
• Isoflurane
• Sevoflurane
• Enflurane
Halogenated
anaes:

MINIMUM ALVEOLAR CONCENTRATION
(MAC)
• The minimum alveolar concentration of an
inhaled anesthetics is the alveolar concentration
that prevents movement in 50% of patient in
response to a standardized stimulus (e.g.
Surgical Incision)

MINIMUM ALVEOLAR
CONCENTRATION (MAC)
DEF: The minimum alveolar concentration of an
inhaled anesthetics is the alveolar concentration
that prevents movement in 50% of patient in
response to a standardized stimulus (e.g.
Surgical Incision)

MAC VALUE OF INHALATION
ANESTHETICS AGENTS
• Nitrous oxide: 105%
• Halothane: 0.75%
• Isoflurane : 1.2%
• Desflurane: 6%
• Sevoflurane: 2%

NITROUS OXIDE

NITROUS OXIDE
Physical properties:
It is a laughing gas.
It is only inorganic anesthetic gas in clinical use.
Colorless and odorless
Non Explosive and Non Infammable
Gas at room temperature and can be kept as a
liquid under pressure.
It is relatively inexpensive.

Effects of Nitrous Oxide on Organ
System
1. CARDIOVASCULAR SYSTEM
• Stimulate sympathetic nervous system.
• Directly depresses myocardial contractility.
• Arterial blood pressure ,heart rate and cardiac
output are slightly increased.
2. RESPIRATORY SYSTEM:
• Increases respiratory rate with decreases tidal volume.
• Minimal change in minute ventilation.

3. CEREBRAL:
• Increases CBF thus increasing intracranial pressure.
4. RENAL SYSTEM:
• It decreases renal blood flow thus leads to drop in
glomerular filtration rate and urinary output.
5. HEPATIC SYSTEM:
• Decreases the Hepatic blood flow but to a lesser extent
than other inhalation agents.
6. GASTROINTESTINAL:
• It causes post operative Nausea and Vomiting.

CONTRAINDICATION OF N2O
• Air embolism
• Pneumothorax
• Acute Intestinal Obstruction
• Tension Pneumocephalus
• Tympanic membrane grafting

HALOTHANE
• Physical Properties:
• It is halogenated alkene.
• Non Inflammable and Non explosive.
• Least expensive .

EFFECTS ON ORGAN SYSTEM
1. CARDIOVASCULAR:
 Dose dependent reduction of arterial blood pressure by direct
myocardial depression.
 It is a coronary artery vasodilator.
 It causes slowing of SA node conduction resulting in
bradycardia.
 Causes rapid ,shallow breathing.
 Decrease in alveolar ventilation and Paco2 elevated.
 Potent dronchodilator.

3. CEREBRAL:
• It increases cerebral blood flow.
4. NEUROMUSCULAR:
• Relaxes skelatal muscle and potentiates Non
depolarizing neuro-muscular blocking agents.
5.RENAL:
• Reduces renal blood flow, glomerular filtration
rate and urinary output.
6. HEPATIC:
• Decreases hepatic blood flow.

CONTRAINDICATION
• Unexplained liver dysfunction.
• Intra-cranial mass lesions.
• Hypo-volemic patient with severe cardiac
diseases.

ISOFLURANE
 It is non flammable volatile with a pungent smell.
EFFECTS ON ORGAN SYSTEM:
1. CARDIOVASCULAR:
 Causes minimal cardiac depression.
 Rapid increase in MAC lead to increase in HR and BP.( Coronary
Steal)
 Dilates coronary arteries.
 Respiratory depression .
 Acts as a good bronchodilator.

3. CEREBRAL:
If con> 1 MAC causes increase in CBF and
Intracranial pressure.
4. NEUROMUSCULAR:
Relaxes skeletal muscles.
5. RENAL:
Decreases renal blood flow , glomerular filtration
rate and urinary output.
6. HEAPTIC:
Reduces hepatic blood flow.
INDICATIONS- For Cardiac and Neuro- Surgery

CONTRAINDICATION
• No such contraindication.
• Patient with severe hypovolemia may not tolorate its
vasodilating effects.

DESFLURANE
 Structure much similar to that of isoflurane.
 Recovery time are approximately 50 % less than those of
Isoflurane. Pungent Smell
 TEC 6
EFFECTS ON ORGAN SYSTEM:
1. CARDIOVASCULAR SYSTEM:
 Similar to Isoflurane( Increases HR and BP when increased
MAC rapidly)
 Dilates coronary arteries.

• Causes decrease in tidal volume and increase in
resp rate.
• Pungency and airway irritation so causes
coughing and sometime bronchospasm.
3. CEREBRAL:
• Increases CBF and Intracranial pressure.
4. NEUROMUSCULAR:
• Relaxes skeletal muscle.
5. RENAL AND HEPATIC SYSTEM:
• No any evidence has been documented.
INDICATION- For Hepatic and Renal Surgery

CONTRAINDICATION
• Severe hypo-volemia.
• Intracranial hypertension.
• Malignant hyperthermia.

SEVOFLURANE
 It is Non pungency.
EFFECTS ON ORGANS:
1. CARDIOVASCULAR SYSTEM:
 Mildly depresses myocardial contractility.
 May prolong QT interval, but no significance.
 Depresses respiratory rate.
 It reverses broncho-spasm

3. CEREBRAL:
• Increases CBF and intra-cranial pressure.
4. RENAL SYSTEM:
• Slightly decreases renal blood flow. Higher Conc
Causes Nephro-toxicity
5. HEPATIC:
• Decreases portal vein blood flow but increases
hepatic artery blood flow thus maintaining total
hepatic blood flow.
6.NEUROMUSCULAR:
• Adequate muscle relaxation.

CONTRAINDICATION
• Severe hypo-volemia.
• Intracranial hypertension.
• Malignant hyperthermia.

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