anesthesia
DESCRIPTION
TRANSCRIPT
ANESTHESIA
Anesthesia
• Loss of consciousness• Analgesia• Adequate muscle relaxation
Analgesia
•Loss of sensation to pain
Types of Anesthetics:
•General Anesthetics• Reversible loss of consciousness• Loss of CNS activity
•Local Anesthetics• No loss of consciousness• Reversible loss of pain sensation
GENERAL ANESTHETICS:
INHALATIONAL ANESTHETICS
INTRAVENOUS ANESTHETICS
STAGES OF GENERAL ANESTHESIA(Guedel)
• Stage I: Analgesia• Stage II:Excitement/ Delirium• Stage III: Surgical Anesthesia
– Plane I: reg. breathing loss of eye movement
– Plane II initiation of IC muscle paralysis
– Plane III: completion ICM paralysis– Plane IV: diaphragmatic paralysis
• Stage IV: Medullary Paralysis
Pharmacokinetics:• tension (partial pressure) in the brain
depth• tension in this tissues rate of
induction and recovery
• Flow of anesthetic during induction:Anesthesia Lungs Arterial Brain &
machine blood tissues
GENERAL ANESTHETICS:
Pharmacokinetics: • absorption (uptake)• distribution• metabolism• elimination lungs
Principal objective:To achieve a constant and optimal brain partial pressure of the inhaled anesthetic
GENERAL ANESTHETICS:
• 2 PHASES:2 PHASES:
– Pulmonary PhasePulmonary Phase
– Circulatory PhaseCirculatory Phase
GENERAL ANESTHETICS: UPTAKEGENERAL ANESTHETICS: UPTAKE
• Pulmonary Phase Concentration of the anesthetic
agent in the inspired gas
Pulmonary ventilation
Transfer of anesthetic gases from alveoli to blood• solubility of the agent• rate of pulmonary blood flow• partial pressure in the alveoli
and mixed venous blood
GENERAL ANESTHETICS: UPTAKEGENERAL ANESTHETICS: UPTAKE
As a rule, the more soluble an anesthetic in the blood the more of it must be dissolved to raise the partial pressure.
• Pulmonary Phase Concentration of the anesthetic
agent in the inspired gas
Pulmonary ventilation
Transfer of anesthetic gases from alveoli to blood• solubility of the agent• rate of pulmonary blood flow• partial pressure in the alveoli
and mixed venous blood
GENERAL ANESTHETICS: UPTAKEGENERAL ANESTHETICS: UPTAKE
GENERAL ANESTHETICS: UPTAKEGENERAL ANESTHETICS: UPTAKE
• Circulatory or Distribution Phase SolubilitySolubility
tissue:blood solubility coefficienttissue:blood solubility coefficient
Tissue Blood FlowTissue Blood Flow Vessel-Rich group – 75% of COVessel-Rich group – 75% of CO Muscle Group – 3%Muscle Group – 3% Fatty Group – 2%Fatty Group – 2% Vessel-Poor group - <1%Vessel-Poor group - <1%
Partial Pressure of Gas in Arterial Partial Pressure of Gas in Arterial Blood and TissuesBlood and Tissues
• RECOVERY and EMERGENCEFactors affecting rate of Elimination
• SOLUBILITY IN BLOOD & TISSUE• BLOOD FLOW
• Flow of anesthetic during elimination:
Tissue/ Blood Lungs AnesthesiaBrain Machine
GENERAL ANESTHETICS:GENERAL ANESTHETICS:
Ideal Characteristics of Inhalational Anesthetics:
• Rapid & pleasant induction & recovery• Rapid changes in depth of anesthesia• Adequate relaxation of smooth muscle• Wide margin of safety• Absence of toxic effect
INHALATIONAL ANESTHETICS
• GASEOUS ANESTHETIC:• NITROUS OXIDE• CYCLOPROPANE
• VOLATILE ANESTHETIC:
A. HalogenatedA. Halogenated B. Non B. Non HalogenatedHalogenated
1. 1. HalothaneHalothane 1. Ether1. Ether
2. Enflurane2. Enflurane 2.2. Chloroform Chloroform
3.3. Isoflurane Isoflurane
4. Methoxyflurane4. Methoxyflurane
5. Sevoflurane5. Sevoflurane
6.6. Desflurane Desflurane
INHALATIONAL ANESTHETICS
• GASEOUS ANESTHETIC:• NITROUS OXIDE• CYCLOPROPANE
• VOLATILE ANESTHETIC:
A. HalogenatedA. Halogenated B. Non B. Non HalogenatedHalogenated
1. 1. HalothaneHalothane 1. Ether1. Ether
2. Enflurane2. Enflurane 2.2. Chloroform Chloroform
3.3. Isoflurane Isoflurane
4. Methoxyflurane4. Methoxyflurane
5. Sevoflurane5. Sevoflurane
6.6. Desflurane Desflurane
Properties of a Desirable Local Anesthetic
• should not be irritating to tissues• should not cause permanent damage
to nerves• have low systemic toxicity• must be effective • should have rapid onset but long
duration of action
• MOA: block nerve conduction
• Structure:– aromatic group (Hydrophobic lipophilic)– amide group (hydrophilic)
• tertiary amine or secondary amine– intermediate chain
•Ester or Amide
LOCAL ANESTHETICSLOCAL ANESTHETICS
Structure
CH2-
CH3
NH2 O-O-CH2-CH2-N
O CH2-CH3
Aromatic grp Alkyl Amide grpLipophilic chain Hydrophilic
• METABOLISM:
Ester plasma and liver esterases metabolite: PABA
Amide liver
• EXCRETION:
kidneys
LOCAL ANESTHETICSLOCAL ANESTHETICS
• ROUTES OF ADMINISTRATION:
1. Topical2. Local Infiltration3. Nerve Block4. Spinal or Intrathecal injection5. Epidural 6. Caudal
LOCAL ANESTHETICSLOCAL ANESTHETICS
LOCAL ANESTHETICSLOCAL ANESTHETICS
ESTERS:ESTERS:
1.1. CocaineCocaine
2.2. ProcaineProcaine
3.3. ChloroprocaineChloroprocaine
4.4. TetracaineTetracaine
AMIDES:AMIDES:
1.1. LidocaineLidocaine
2.2. BupivacaineBupivacaine
3.3. MepivacaineMepivacaine
4.4. DibucaineDibucaine
5.5. PrilocainePrilocaine
6.6. EtidocaineEtidocaine
May also be classified into
a. Short acting – cocaine, procaineb. Intermediate acting – lidocaine,
mepivacaine, dibucaine, prilocainec. Long acting – tetracaine,
bupivacaine, etidocaine
1. Hepatotoxic agent a. Isoflurane
2. Nephrotoxic agent b. Barbiturate3. Cardiotoxic agent c. Enflurane4. Thiopental d. Halothane5. Flammable agent e. Ether
a.Amide LA b. Esther LA6. Lidocaine7. Tetracaine8. Cocaine9. Bupivacaine10. Etidocaine