Local anesthetics work by reversibly blocking sodium channels in nerve cell membranes, preventing the generation and conduction of nerve impulses. Early local anesthetics included cocaine and procaine. Current local anesthetics are classified as esters or amides and differ in their metabolism and duration of action. The potency of local anesthetics depends on their lipid solubility, pKa, and ability to penetrate nerve sheaths. Co-administration with vasoconstrictors or opioids can prolong the duration and intensity of nerve blockade from local anesthetics.
The presentation gives a detailed overview of local anesthetics. This presentation made very effectively, covering mostly all the important sub topics. It will be definitely useful for all the students Comment your response regarding the presentation.
The presentation gives a detailed overview of local anesthetics. This presentation made very effectively, covering mostly all the important sub topics. It will be definitely useful for all the students Comment your response regarding the presentation.
EVERYTHING RELATED TO LOCAL ANESTHETICS LIKE DEFINITION, HISTORY INTRODUCTION PHYSIOLOGY MECHANISM OF ACTION ANATOMY OF NERVES CLASSIFICATIONS INDIVIDUAL DRUGS AND ITS USES LOCAL ANESTHETICS TOXICITY LOCAL ANESTHETIC SYSTEMIC TOXICITY (LAST) MANAGEMENT OF LAST ETC...
Lecture slides for undergraduates medical (MBBS) Students. Source material for this presentation is Essentials of Pharmacology, KD Tripathi, Katzung and Goodman and Gillman. It deals with Local anaesthetics with their mechanism of action, pharmacokinetics , adverse effects and therapeutic uses.
A teaching slide set describing the mechanisms of action and clinical use of local anaesthetics. This session is a basic introduction to the pharmacodynamics and pharmacokinetics of local anaesthetics. It is aimed at preclinical medical or dental students, or students in the early years of a pharmacology degree.
EVERYTHING RELATED TO LOCAL ANESTHETICS LIKE DEFINITION, HISTORY INTRODUCTION PHYSIOLOGY MECHANISM OF ACTION ANATOMY OF NERVES CLASSIFICATIONS INDIVIDUAL DRUGS AND ITS USES LOCAL ANESTHETICS TOXICITY LOCAL ANESTHETIC SYSTEMIC TOXICITY (LAST) MANAGEMENT OF LAST ETC...
Lecture slides for undergraduates medical (MBBS) Students. Source material for this presentation is Essentials of Pharmacology, KD Tripathi, Katzung and Goodman and Gillman. It deals with Local anaesthetics with their mechanism of action, pharmacokinetics , adverse effects and therapeutic uses.
A teaching slide set describing the mechanisms of action and clinical use of local anaesthetics. This session is a basic introduction to the pharmacodynamics and pharmacokinetics of local anaesthetics. It is aimed at preclinical medical or dental students, or students in the early years of a pharmacology degree.
Classification
Mechanism of action
Duration of action
Absorption and distribution
Mode of action
Theories of action of L.A
Pharmacokinetics of local anaesthetics
Routes of administration
Metabolism or biotransformation
Individual agents
Vasoconstrictors
Systemic effects
Toxicity
Advantages
Disadvantages
Maximum allowable dose
Local anaesthetics in community trust services
Pharmacology of local aesthetics and its mechanism of action, adverse effects and uses of local aesthetics with a note on the techniques of local aesthetics
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
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This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
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These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
New Drug Discovery and Development .....NEHA GUPTA
The "New Drug Discovery and Development" process involves the identification, design, testing, and manufacturing of novel pharmaceutical compounds with the aim of introducing new and improved treatments for various medical conditions. This comprehensive endeavor encompasses various stages, including target identification, preclinical studies, clinical trials, regulatory approval, and post-market surveillance. It involves multidisciplinary collaboration among scientists, researchers, clinicians, regulatory experts, and pharmaceutical companies to bring innovative therapies to market and address unmet medical needs.
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
ASA GUIDELINE
NYSORA Guideline
2 Case Reports of Gastric Ultrasound
6. Local Anesthetics
DEFINITION
• Drugs which
– produce a REVERSIBLE anesthesia and analgesia…
– in a localized part of the body…..
– when applied directly onto nerve tissues or mucous membranes
– Without causing damage to nerves
7. Local Anesthetics
DESIRABLE CHARACTERISTICS
Rapid onset of action
Brief, reversible block of nerve conduction
Low degree of systemic toxicity***
Soluble in water and stable in solution
Effective on all parts of the nervous system, all types of
nerve fibers
• NONE totally meets these optimally yet!!
8. C
LAs are Weak Bases
C O
O
R N
R
R
NH
O
R N
R
R
Aromatic portion Amine portion
Intermediate chain
ESTER
AMIDE
LIPOPHILIC HYDROPHILIC
9. Two types of linkages
give rise to 2 chemical classes of local anesthetics.
ESTER LINKAGE AMIDE LINKAGE (2 i’s!!)
PROCAINE
procaine (Novocaine)
chloroprocain
tetracaine (Pontocaine)
benzocaine
cocaine
LIDOCAINE
lidocaine (Xylocaine)
mepivacaine (Carbocaine)
bupivacaine (Marcaine)
etidocaine (Duranest)
ropivacaine (Naropin)
Prilocaine
10. Local Anesthetics
Clinical Significance of chemical classification
• Biotransformation
– ESTERS are rapidly metabolized in the plasma by a
cholinesterase
– AMIDES are more slowly destroyed by liver microsomal P450
enzymes.
11. Local Anesthetics
MECHANISM OF ACTION
(specific & non-specific)
• Specific (No effect on RMP)
– bind to specific receptors at the INTRACELLULAR end of
the voltage gated sodium channel
• prevent the transmission of nerve impulses (conduction blockade) by inhibiting the
passage of sodium ions through ion-selective sodium channels in nerve membranes.
• sodium ion channel permeability fails to increase-
12. Mechanism of action of LA
1. Impulse conduction slow
2. The rate of rise and magnitude of the action potential declines, and
3. The threshold for excitation increase
4. The ability to generate an action potential is abolished or cancelled..
• LA bind more readily to open sodium channels while they have greatest
affinity for sodium channel in inactivated state and slows its
reversion to the resting state.
13.
14. + +
- -
+ +
--
- -
+ + + +
- -
Na+
+ ++ +
- - - -
Resting
(Closed**)
Open
(brief)
inactivated
Very slow repolarization
in presence of LA
LA receptor
LA have highest affinity
for the inactivated form
Refractory period
**Closed state may exist in various forms as it moves from resting to open. LA have a high
affinity for the different closed forms and may prevent them from opening.
15. Structural characteristics
of Na+ channels
• 1 larger subunit (260 kD) (has
ion conducting path)
• 1 or 2 smaller subunits (30
kD)
• All subunits heavily
glycosylated
16. Structural characteristics
of Na+ channels
• 1 larger subunit (260 kD) (has
ion conducting path)
• 1 or 2 smaller subunits (30
kD)
• All subunits heavily
glycosylated
17. Local Anesthetics
MECHANISM OF ACTION
(specific)
• Action is voltage dependent
– This may be due to
• Voltage changes induce changes in form of Na+ channels
• LA have a higher affinity for Na+ channel in
–Some closed forms of the channel preventing them from opening
–higher affinity for channel in inactivated state slowing return to
resting form (prolonged refractory period)
• Increased entry into neuron through opened Na channel
18. Local Anesthetics
MECHANISM OF ACTION
(specific)
• LA are WEAK BASES and access to receptor site is dependent on:
– pKa
– lipid solubility
– molecular size and level of neuronal activity
• LA ACT IN CATIONIC FORM (charged)
19. Local Anesthetics
MECHANISM OF ACTION
(Non-specific)
• LA have some non-specific actions
– Appear to ‘dissolve’ in the membrane
– Distorting the membrane and altering function
• Benzocaine (pKa ~3 almost 100% in nonionized form)
20. Differential sensitivity of neurons to Local anesthetics
Fiber type Function Diameter (μM) Myelination Conduction velocity
(m/s)
Sensitivity to LA
block
Type A
Alpha proprioception, motor
12 – 20 Heavy 70 – 120 +
Beta touch, pressure 5 – 12 Heavy 30 – 70 ++
Gamma muscle tone 3 – 6 Heavy 15 – 30 ++
Delta pain, temperature 2 – 5 Heavy 12 – 30 +++
Type B preganglioniic
autonomic,(e.g. vasomotor)
<3 Light 3 – 15 ++++
Type C
Dorsal root pain, temperature 0.4 – 1.2 None 0.5 – 2.3 ++++
sympathetic postganglionic, (e.g.
vasomotor)
0.3 – 1.3 None 0.7 – 2.3 ++++
21. MINIMUM CONCENTRATION
Cm-The minimum conc. of LA necessary to produce the conduction blockade of
nerve impulses. (analogous to MAC)
Cm of motor fibers ~twice that of sensory fibers.
A minimal length of myelinated nerve fiber must be exposed to an adequate conc.
of LA for the conduction blockade.
Preganglionic B fibers are more readily blocked than any fiber, even though these
fibers are thicker than C fibres.
22. Differential blockade
The selective blockade of preganglionic sympathetic nervous system B
fibers in response to low conc. of LA.
Slightly higher concentrations interrupt conduction in small C fibers and
small- and medium-sized A fibers, with loss of sensation for pain and
temperature.
Touch, proprioception, and motor function are still present, so that the
patient will sense pressure but not pain with surgical stimulation.
23. FACTORS INFLUENCING LA ACTION
~ LIPID SOLUBILITY ~
• Potency and systemic toxicity directly correlate with Lipid Solubility
• Local duration positively correlated with Lipid Solubility and
inversely related to vasodilation
24. FACTORS INFLUENCING LA ACTION
Effect of pH
Charged (cationic) form binds to receptor site,efficacy of drug can be changed by
altering extracellular or intracellular pH
25. FACTORS INFLUENCING LA ACTION
~ Hydrogen ion concentration ~
• At pH 7.4 80 - 90% is ionized and can’t enter cells
– non-ionized (lipid-soluble) form needed for penetration
– cationic form required for binding to receptor
rate of ONSET is related to pKa (because it determines the % of LA in a LS form)
Alkalization hastens the onset of action
26. FACTORS INFLUENCING LA ACTION
~ Hydrogen ion concentration ~
• inflammation tends to produce lower pH in tissues therefore
• LA are more ionized
• don’t penetrate very well
• decreased ability of LA to produce effects
• RATE LIMITING FACTOR for LA onset is the time to penetrate nerve sheath
and permeate cell membrane
27. FACTORS INFLUENCING LA ACTION
• Central neuraxial coadministration of LA and opioids to prolong and
intensify analgesia and anesthesia
– LA act to decrease propagation of pain sensation
– Opioids act to diminish pain by decreasing NT from afferent neurons
• Alpha 2 agonists (e.g. clonidine) enhance intrathecal and epidural nerve
blocks by acting on alpha 2 receptors to decrease NT release
28. Local Anesthetics
~ PHARMACOKINETICS ~
• ABSORPTION
– LA generally have good absorption from mucous membranes and
intradermal injection sites. (into tissues)
Systemic absorption terminates local action (out of tissues). (Not local
metabolism!!!)
29. Local Anesthetics
~ PHARMACOKINETICS ~
• ABSORPTION
– Factors influencing peak PLASMA concentration:
• Site of injection (vascularity)
(IV > tracheal > intrathecal > intercostal > caudal > paracervical > epidural >
brachial plexus > sciatic > s.c.)
• Total dose
• Specific drug characteristics
– tendency to produce vasodilation
• Presence of vasoconstrictor (e.g., epinephrine, phenylephrine)
30. Local Anesthetics
~ PHARMACOKINETICS ~
• ABSORPTION
– Effects of vasoconstrictors
• Decrease rate of systemic absorption and decrease systemic toxicity
• Increase local drug concentration and increase neuronal uptake of LA
• Increase local duration of action (e.g. lidocaine’s duration may increase two fold
with epi)
31. Local Anesthetics
~ PHARMACOKINETICS ~
• ABSORPTION
– Potential adverse effects of vasoconstrictors
• May produce tissue necrosis
• DON’T use in areas of toes, fingers, ear lobes, penis (ischemia)
• May produce systemic toxicity (cardiovascular)
32. Local Anesthetics
~ PHARMACOKINETICS ~
• DISTRIBUTION
– LA can be widely distributed to all parts of the body including CNS
– Distribution is a means of terminating local drug action ........ not
metabolism!!
33. Local Anesthetics
~ PHARMACOKINETICS ~
• METABOLISM
– Ester type LA
• Hydrolysis by cholinesterase in plasma to PABA derivatives
– pseudo cholinesterase or butrylcholinesterase
• Generally, short acting and low systemic toxicity**
• Prolonged effects seen with genetically determined deficiency , altered
esterase, cholinesterase inhibitors
34. Local Anesthetics
~ PHARMACOKINETICS ~
• METABOLISM
– Amide type LA
• Hydrolyzed by liver microsomal enzymes (P450)
• Longer acting & more systemic toxicity than esters
• Caution with severely compromised hepatic function
35. Effects of medical conditions & drugs on LA dosing &
kinetics
Renal failure: ↑Vd; ↑accumulation of metabolic products
Hepatic failure: ↑amide Vd, ↓amide clearance
Cardiac failure; β and H2 blockers: ↓hepatic blood flow and ↓amide clearance
Cholinesterase deficiency or inhibition: ↓ester clearance
Pregnancy: ↑hepatic blood flow; ↑amide clearance; ↓protein binding
38. Local Anesthetics
Systemic Effects (toxicities)
• Extensions of pharmacological action
• Primarily related to blocking sodium channels
• Intensity is dependent on blood levels
• Toxic levels of LA in blood will not occur if absorption (into
systemic blood) is slow or metabolism is rapid
39. Local Anesthetics
Systemic Effects (toxicities)
• CNS (More sensitive than cardio)
– Dose-related spectrum of effects and All effects are due to depression of neurons
Premonitory signs include: ringing in ears, metalic taste, numbness around lips
• First an apparent CNS stimulation (convulsions most serious)
• Followed by CNS depression (death due to respiratory depression)
– Cocaine - euphoria (unique in its ability to stimulate CNS)
– Lidocaine - sedation even at non-toxic doses
40. Local Anesthetics
Systemic Effects (toxicities)
• Cardiovascular System
– HYPOTENSION: Arteriolar dilation is a result of:
• Direct effect (procaine and lidocaine have most effect)
• Block of postganglionic sympathetic fiber function
• CNS depression
• Avoid by adding vasoconstrictor to prep
• Note: cocaine is exception: produces vasoconstriction, blocks NE reuptake
41. Local Anesthetics
Systemic Effects (toxicities)
• Cardiovascular System
– ARRHYTHMIAS: direct effect (More resistant than CNS)
• Decrease cardioexcitability and contractility
• Decreased conduction rate
• Increased refractory rate (bupivacaine)
• Note: cocaine is exception......it stimulates heart
• ALL can cause arrhythmias if conc. is high enough
42. Lipid emulsion counteracts bupivacaine cardiac toxicity
• 20% Intralipid
• 1.5 mg/kg initial bolus
• 0.25 mg/kg/min infusion for 30-60 minutes
• Bolus may be repeated 1-2 times at 5 minutes interval for persistent
asystole
• May increase infusion rate up to 0.5 mg/kg/min if blood pressure
decreases
43. Local Anesthetics
Systemic Effects (toxicities)
• Methemoglobinemia
– Some LA metabolites have significant oxidizing properties
– This may cause a significant conversion of hemoglobin to methemoglobin
and compromise ability to carry oxygen
– May be a problem if cardiopulmonary reserve is limited
– Treat with oxygen and methylene blue (converts methemoglobin to
hemoglobin)
• prilocaine benzocaine have been implicated
44. Local Anesthetics
Systemic Effects (toxicities)
• ALLERGIC REACTIONS ... fairly rare
– Mostly with ester types; rarely amides (procaine)
• esters metabolized to PABA which has allergenic properties
– Cross-sensitivity within same chemical class of LA
– Anaphylactic reactions are rare ..... diphenhydramine can be used to control minor reactions.
– The preservative methyl paraban in multidose vials may be responsible for some allergic
phenomenon
45. Local Anesthetics
Systemic Effects (toxicities)
• NEUROTOXICITY
– LA can cause concentration-dependent nerve damage to central and
peripheral NS
– Mechanism(s) not clear
– Permanent neurological injury is rare
– May account for
• transient neurological symptoms after spinal anesthesia
• Cauda equina syndrome
• Ant.spinal artery syndrome
47. SELECTIVE PHARMACOLOGICAL PROPERTIES OF SOME ESTER - type LA
• Cocaine
• Natural alkaloid derived from leaves of erythroxylon coca
• Medical use limited to surface or topical anesthesia (corneal or
nasopharyngeal)
• Should never be injected, protoplasmic poison, can cause tissue necrosis
• Prominent CNS stimulation with marked effect on mood and behaviour
• Strong psychological but little physical dependence
• Stimulates vagal centre bradycardia
48. SELECTIVE PHARMACOLOGICAL PROPERTIES OF SOME ESTER - type LA
Contd..
•Stimulates vasomotor centre rise in BP
•Stimulates temperature regulatory centre pyrexia
•Avoid epinephrine because cocaine already has vasoconstrictor properties.
(EXCEPTION!!!)
•A toxic action on heart may induce rapid and lethal cardiac failure
.
•A marked pyrexia is associated with cocaine overdose
49. COCAINE TOXICITY
• Cocaine blocks the presynaptic uptake of NE and dopamine, thus increasing their
postsynaptic conc.
• Acute cocaine overdose
– Coronary vasospasm
– Myocardial ischemia and infarction
– Ventricular cardiac dysrhythmias (ventricular fibrillation)
– Hypertension and tachycardia (increased myocardial oxygen requirements)
– Dose dependent decreases in uterine blood flow (fetal hypoxemia)
51. SELECTIVE PHARMACOLOGICAL PROPERTIES OF SOME ESTER - type LA
• Benzocaine (Americaine)
– pKa ~ 3, essentially all non-ionized.... mechanism may be non-specific
– for surface anesthesia (topical) only ... ointments, sprays, etc.
– Used to produce anesthesia of mucous membranes and to suppress gag
reflex during endoscopy
– methemoglobinemia
52. SELECTIVE PHARMACOLOGICAL PROPERTIES OF SOME ESTER - type LA
• Procaine (Novocaine)
– Topically ineffective
– Used for infiltration because of low potency and short duration but most
commonly used for spinal anesthesia
– Short local duration ......produces significant vasodilation. Epinephrine
used to prolong effect
– systemic toxicity negligible because rapidly destroyed in plasma
53. SELECTIVE PHARMACOLOGICAL PROPERTIES OF SOME ESTER - type LA
• Tetracaine (Pentocaine)
– topical, infiltration and spinal anesthesia
– Frequently used for topical ophthalomogical anesthesia
– Also for topical application to nose, throat and tracheobronchial tree
– slow onset and more prolonged effect than procaine d/t slow
metabolism(longest duration of the esters)
– ~10X more toxic and more potent than procaine
55. SELECTIVE PHARMACOLOGICAL PROPERTIES OF SOME AMIDE - type LA
• LIDOCAINE (Xylocaine) Most widely used LA
– Effective by all routes.
– Faster onset, more intense, intermediate acting
– Good alternative for those allergic to ester type
– More sedative than others, early central effects are
drowsiness, mental clouding, altered taste and tinnitus
56. • Uses:
• surface application, infiltration, nerve block, epidural, spinal and IVRA
• Also as antiarrhythmic drug
• Produces intense analgesia when injected i.v., (continuous low dose
infusion of lidocaine to maintain plasma conc. Of 1-2 μg/ml decreases
severity of postop pain)
• Also has cough suppressant effect
• When inhaled, it attenuate histamine induced bronchospasm
57. • Mepivicaine (Carbocaine)
– Effective by all routes except topical
– Similar onset and duration as lidocaine
– More toxic to neonates so not used in obstetrical anesthesia
58. • Bupivacaine (Marcaine)
– No topical effect
– Slower onset and one of longer duration agents
– Unique property of sensory and motor dissociation can provide
sensory analgesia with minimal motor block
• has been popular drug for analgesia during labor
– More cardiotoxic than other LA
60. Levobupivacaine
• Newer amide LA
• S – enantiomer of bupivacaine.
• Almost similar pharmokinetics of bupivacaine
• Advantages : less cardio and neurotoxic than bupivac
• Disadvantage : less potent than bupivac.
61. • Ropivacaine
– Enantiomer of bupivacaine (S stereoisomer)
– No topical effectiveness
– Clinically ~ equivalent to bupivacaine
– Similar sensory versus motor selectivity as bupivacaine with
significantly less CV toxicity
– Continuous epidural ropivacaine is being used for relief of
postoperative and labour pain
62. • Prilocaine
– Similar clinical profile to that of lidocaine
– Does cause significantly less vasodilation than lidocaine
– Most popular clinical application is for topical anesthesia as in combo with
lidocaine in a eutectic mixture
– Because of rapid systemic metabolism considered least toxic of amide LA
63. Combination product
EMLA
• EMLA = Eutectic (easily melted) Mixture of Local Anesthetics
– Eutectic = two solid substances mixed together in equal quantities by
weight form a eutectic mixture
• EMLA =5% lidocaine and 5%prilocaine in 1:1 proportion becomes
an oily mixture
64. • Lidocaine/prilocaine combination is indicated for dermal anaesthesia
prevents pain associated with intravenous catheter insertion,
blood sampling,
split-thickness skin-graft harvesting
laser removal of portwine stains,
lithotripsy
circumcision
topical anaesthesia of leg ulcers for cleansing or debridement
– it can also be used to numb the skin before tattooing.
65. EMLA
• Dermal analgesia sufficient for beginning an i.v.line requires a contact time of at least 1 h
under an occlusive dressing. Depth of penetration (usually 3–5 mm), duration of action
(usually 1–2 h), and amount of drug absorbed depend on application time, dermal blood
flow, keratin thickness, and total dose administered.
• Typically, 1–2 g of cream is applied per 10-cm2 area of skin, with a maximum application
area of 2000 cm2 in an adult (100 cm2 in children weighing less than 10 kg.)
66. • Side effects include skin blanching, erythema, and edema.
• EMLA cream should not be used on mucous membranes, broken
skin, patients with a predisposition to methemoglobinemia
67. Other drugs with LA activity
• A few drugs, not generally used for local anesthesia, have LA
effects
• May be substituted if patient is allergic to both esters and amide
types.
– TCA
– diphenhydramine
– chlorpromazine
– corticosteroids
68. Local anesthetics
THINGS TO REMEMBER
• Give smallest volume and dose
• Make injections slowly to avoid inadvertent IV injection
• Have drugs available to manage adverse effects
• Don’t take food or liquids < 60 minutes after oral topical
application .... gag, swallow, cough reflexes may be not working
69. CLINICAL APPLICATIONS
• Regional Anesthesia
– Regional anesthesia is classified according to the following six sites of
placement of the local anesthetic solution:
– topical or surface anesthesia,
– local infiltration,
– peripheral nerve block,
– intravenous regional anesthesia (Bier block),
– epidural anesthesia, and
– intrathecal anesthesia
70. CLINICAL APPLICATIONS
• SURFACE ANESTHESIA (Topical)
– by placement on the mucous membranes of the nose, mouth,
tracheobronchial tree,cornea, esophagus, or genitourinary tract.
– Nebulized lidocaine- used to produce surface anesthesia of the upper
and lower respiratory tract before fiberoptic laryngoscopy and/or
bronchoscopy.
– Lidocaine, tetracaine
71. Topical anesthesia
drug Conc. onset Duration( min) Recomm. max.dose
( mg )
LIGNOCAINE 4%, 10% FAST 30-60 300
TETRACAINE 2% FAST 30-60 20
BENZOCAINE UPTO 20% FAST 30-60 200
COCAINE 4-10% FAST 30-60 150
72. CLINICAL APPLICATIONS
• INFILTRATION ANESTHESIA
– extravascular placement of LA in the area to be anesthetized, to reach
nerve terminals and branches
– Lidocaine- LA most often selected for infiltration anesthesia.
– Epinephrine-containing drugs should not be injected intracutaneously or
into tissues supplied by endarteries.
– Used in minor surgery.
– Immediate onset with variable duration.
• Most LA’s used
73. INFILTRATION ANAESTHESIA
drug Conc. onset Duration
( min )
Recomm. Max.dose
(mg)
LIDOCAINE 0.5-2% FAST 60-240 300 or
500 with adr
MEPIVACAINE 0.5-1% FAST 60-240 400 or
500 with adr
ETIDOCAINE 0.5% FAST 120-480 300 or
400 with adr
PRILOCAINE 0.5-1% FAST 60-120 600
BUPIVACAINE 0.25% FAST 120-480 175 or
225 with adr
LEVOBUPIVACAINE 0.25% FAST 120-480 150
ROPIVACAINE 0.2-0.5% FAST 120-360 200
CHLOROPROCAINE 1% FAST 30-60 800 or
1000 with adr
74. CLINICAL APPLICATIONS
• NERVE BLOCK or FIELD BLOCK
– Interruption of nerve conduction upon injection into the region of nerve plexus or trunk.
– nerve fibers located in the mantle of the mixed nerve are anesthetized first. These mantle
fibers usually are distributed to more proximal anatomical structuresthe initial development
of anesthesia proximally, with subsequent distal spread as LA solution diffuses to reach more
central core nerve fibers.
– Used for surgery, dentistry, analgesia.
• Most LA’s used
76. Peripheral Nerve Blocks
Any peripheral nerve can be blocked by injecting LA in their
perivascular sheath or the closed compartment in which it travels
Ex.,
- Cervical, Brachial plexus block
- Transverse abdominis block
- Lumbar block
- Sciatic nerve, Popliteal nerve block
- Ankle block
77. Nerve block anaesthesia
drug Conc. onset Duration
(min)
Recomm. max. dose
(Mg)
LIDOCAINE 1-1.5% fast 60-180 300 or
500 with adr
MEPIVACAINE 1-1.5% fast 120-240 400 or
500 with adr
ETIDOCAINE 0.5-1% fast 180-270 300 or
400 with adr
PRILOCAINE 1.5-2% fast 90-180 600
BUPIVACAINE 0.25-0.5% slow 240-960 175 or
225 with adr
LEVOBUPIVACAINE 0.25-0.5% slow 840-1020 150
ROPIVACAINE 0.5-1% slow 300-480 250
CHLOROPROCAINE 2% fast 30-60 800 or
1000 with adr
78. CLINICAL APPLICATIONS
• INTRAVENOUS REGIONAL ANAESTHESIA (BIER’S BLOCK)
– I.V. injection of a LA solution into an extremity isolated from the rest of the systemic circulation by a
tourniquet
– produces a rapid onset of anesthesia and skeletal muscle relaxation.
– duration of anesthesia- independent of the specific LA and determined by how long the tourniquet is
kept inflated.
– Normal sensation and skeletal muscle tone return promptly on release of the tourniquet, which
allows blood flow to dilute the conc. of LA
– Bupivacaine is contraindicated for IVRA
80. IVRA
drug Conc. onset Duration
(min)
Recomm. max. dose
(Mg)
LIDOCAINE 0.25-2.0% FAST 30-60 300
PRILOCAINE 0.25-0.5% FAST 30-60 600
81. CLINICAL APPLICATIONS
• SPINAL ANESTHESIA
– Injection into subarachnoid space below level of L2 vertebra.
– act on superficial layers of the spinal cord, but the principal site of action is the
preganglionic fibers as they leave the spinal cord in the anterior rami.
– Because preganglionic SNS fibres are blocked by conc. of LA that are insufficient to affect
sensory or motor fibres, the level of SNS denervation during spinal anesthesia extends
approximately two spinal segments cephalad to the level of sensory anesthesia.
82. – For the same reasons, the level of motor anesthesia averages two segments below
sensory anesthesia.
– Use hyperbaric or hypobaric solutions depending on area of blockade.
– Used for surgery to abdomen, pelvis or leg when can’t use general anesthesia.
• Lidocaine, tetracaine
85. SPINAL ANAESTHESIA
drug Conc. onset Duration
(min)
Recomm. max. dose
(Mg)
LIDOCAINE 1.5-5% FAST 30-60 100
MEPIVACAINE 2-4% FAST 60-120 100
BUPIVACAINE 0.5-0.75% FAST 60-240 20
LEVOBUPIVACAINE 0.5-0.75% FAST 60-360 20
CHLOROPROCAINE 2-3% FAST 30-60 Preservative free
PROCAINE 10% FAST 30-60 1000
TETRACAINE 0.5% FAST 120-360 20
86. Clinical Applications
• EPIDURAL AND CAUDAL ANESTHESIA
– Injection into epidural space usually at lumbar or sacral levels.
– produce anesthesia by diffusion across the dura to act on nerve roots and passage into the
paravertebral area through the intervertebral foramina, thus producing multiple
paravertebral nerve blocks.
– In contrast to SAB, often a zone of differential sympathetic nervous system blockade does
not exist, and the zone of differential motor blockade may average up to four rather than
two segments below the sensory level.
87. Clinical applications
– larger dose required, leading to a substantial systemic absorption of the LA. addition of
1:200,000 epinephrine solution decreases the systemic absorption of LA by
approximately one-third.
– Used like spinal and also painless childbirth.
– Unwanted effects similar to that of spinal less likely because longitudinal spread is
reduced.
– Addition of opioids to local anesthetic solutions placed in the epidural space results in
synergistic analgesia.
• Lidocaine, bupivacaine, ropivacaine
88. Epidural anaesthesia
drug Conc. onset Duration
(min)
Recomm. max. dose
(Mg)
LIDOCAINE 1.5-2% FAST 60-120 300 or
500 with adr
MEPIVACAINE 1.5-2% FAST 60-180 400 or
500 with adr
ETIDOCAINE 1-1.5% FAST 120-480 300 or
400 with adr
PRILOCAINE 2-3% FAST 60-180 600
BUPIVACAINE 0.5-0.75% MODERATE 120-300 175 or
225 with adr
LEVOBUPIVACAINE 0.5-0.75% MODERATE 300-540 150
ROPIVACAINE 0.5-1% MODERATE 120-360 200
CHLOROPROCAINE 2-3% FAST 30-60 800 or
1000 with adr
89. Next class : CVS physiology part – I
To be presented by : Dr. Sneha