LOCAL ANESTHETICS PART II Flashcards
EFFECTIVENESS OF LOCAL ANESTHETICS depends on (2) factors:
Onset Time
Duration of Action
induction time
A. Onset Time
B. Duration of Action
A
time it takes to achieve a nerve block from deposition of the anesthetic
A. Onset Time
B. Duration of Action
A
the amount of time the nerve block will remain
A. Onset Time
B. Duration of Action
B
FACTORS AFFECTING THE EFFECTIVENESS OF LOCAL ANESTHETICS (10)
- pH OF SOLUTION
- pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
- pKa OF SOLUTION
- LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
- TYPE AND SIZE OF NERVE
- ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
- INJECTING INTO A HIGHLY VASCULAR AREA
- PRESENCE OF VASOCONSTRICTOR
- VASODILATOR ACTIVITY
- NON-NERVOUS TISSUE DIFFUSIBILITY
T/F
increased pH means alkalinization and faster onset time
T
T/F
decreased pH means acidification and slower onset time
T
pH without vasoconstrictor
A. 5.5
B. 3.3
A
pH with vasoconstrictor
A. 5.5
B. 3.3
B
acidification of tissues causes inadequate anesthesia
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
B
deprotonation will not occur if the pH is acidic
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
B
low pKa means higher concentration of RN causing faster diffusion through the nerve membrane and producing a rapid onset time
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
C
pKa affects the onset time of the local anesthetic
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
C
Lidocaine pKa
7.7
Percent base (RN) at pH 7.4 of lidocaine
29
Onset of time of lidocaine
2 to 4 min
Tetracaine pKa
8.6
Percent base (RN) at pH 7.4 pf tetracaine
7
Onset time of tetracaine
10 to 15 min
increased lipid solubility and CHON binding causes increased potency
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
D
the more protein bound a drug is, the longer its duration of action
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
D
the more its affinity for lipid material, the longer its duration of action
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
D
not all nerves will be blocked at the same time
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
E
→ a nerve is a bundle of axons and in that bundle some are thin,
thick, myelinated or unmyelinated
→ because of this, a differential block can be achieved
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
E
→ a nerve is a bundle of axons and in that bundle some are thin,
thick, myelinated or unmyelinated
→ because of this, a differential block can be achieved
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
E
TYPE AND SIZE OF NERVE :
SEQUENCE OF BLOCK (3)
→ thin before thick nerve fibers
→ myelinated before unmyelinated
o because LA affects exposed areas of the myelinated nerve which are the nodes of Ranvier
→ C and small myelinated fibers (A-delta), before thick, myelinated (A-alpha and beta) fibers
TYPE AND SIZE OF NERVE:
DIFFERENTIAL BLOCK
Pain
↓
Temperature
↓
Touch
↓
Proprioception
↓
Muscle Tone
Proprioceptor fibers are found outside the ___ area.
apical
done when patient still feels pain
REINJECTION
located in the middle of the fasciculi
Core Fibers
fibers that go into dense tissue like bone
Core Fibers
blocked last
Core Fibers
located at the outer surface of the bundle
Mantle Fibers
fibers that go into soft tissues like the gingiva
Mantle Fibers
blocked first
Mantle Fibers
Significant in clinics because the patient may not feel anything on the soft tissue such as the gingiva but pain may still be felt when drilling into the bon
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
F
→ rapid absorption to systemic circulation
→ decreased effective concentration
→ rapid termination of anesthetic effect
These areas include the CNS and the CVS.
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
G
→ anesthetic solution is in contact with the nerve longer causing prolongation of intensity of analgesia
→ the longer it stays, the longer will be the intensity and duration; this has nothing to do with onset
→ vasoconstrictors are added so that anesthetic solution will stay longer in the area; it is not right away absorbed or brought away from the area being anesthetized
→ there are some anesthetics made without vasoconstrictors made for patients with medical conditions such as uncontrolled hypertension
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
H
→ rapid removal from site of injection causes decreased potency and duration
→ by nature, anesthetics are vasodilators; to make it more effective, it needs a vasoconstrictor
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY
I
causes decreased onset of time
→ as these anesthetic solutions get absorbed to other areas of the nerve, the onset time is slow
A. pH OF SOLUTION
B. pH OF TISSUES WHERE ANESTHETIC IS DEPOSITED
C. pKa OF SOLUTION
D. LIPID SOLUBILITY & CHON BINDING CHARACTERISTICS
E. TYPE AND SIZE OF NERVE
F. ARRANGEMENT OF NERVE FIBERS IN THE COAXIAL BUNDLE
G. INJECTING INTO A HIGHLY VASCULAR AREA
H. PRESENCE OF VASOCONSTRICTOR
I. VASODILATOR ACTIVITY
J. NON-NERVOUS TISSUE DIFFUSIBILITY