intro to anaesthesia Flashcards
what is anaesthesia
loss of sensation to the entire or part of the body
what is analgesia
The absence of pain in response to stimulation which would normally be painful.
No loss of consciousness, retains some feeling and/or movement
(able to functional normally, just without pain)
explain the difference between anaesthesia and analgesia
anaesthsia: loss of sensation to part or whole body (uncocious)
analgesia: pain relief without causing unconciousness
give me examples of when anaesthesia is used
Facilitation of immobilisation for radiographs
Surgical or invasive medical procedures
Safe handling of fractious patients (agressive)
Transportation of wild and exotic animals
Euthanasia
Humane slaughter of food animals
what are the different types of anaesthesia
- general (completely unconcious, cannot be woken up even if experiencing pain)
-local (anaesthetising part of the body by temporarioy aboloshing the transmission of impulses along nerve fibre) (remember ur dental surgery and u felt the electric shock when given local)
-regional (cannot feel pain to a large body area, eg whole leg)
factors affecting anaesthesia
- human factors
Inadequate obtainment of history of the patient (pre opp)
Failure to perform adequate physical examination (pre opp)
Lack of familiarity with the anaesthetic machine and drugs being used (opp)
Incorrect administration of drugs
Personnel who are fatigue, pre-occupied or inattentive - Equipment factors
Exhausted carbon dioxide absorber
Empty oxygen tank
Mis-assembly of the anaesthetic machine
Endotracheal tube problems
Vapouriser problems
Pop-off valve problems - anaesthetic agent factor (choice of drug)
An anaesthetist should be familiar with the adverse side effects and contraindications of the respective drugs used.
(Multi-drug use to achieve balanced anaesthesia can be safer than using a single drug, provided the dosages of the individual drugs are appropriately reduced) - patient variation factor
Type of patient: old, young, sick
Species and breed dispositions
Dogs and cats vs pocket pets
Brachycephalic breeds
Underlying medical conditions
E.g., liver/kidney failure, heart murmur
Helps us determine the anaesthetic risk.
what is included in a minimum patient database (patient evaluation)
- patient history ( from client+ past medical history)
-physical examination ( species, breed, gender, age, steralisation status, body weight, BCS score tempremant, bad: fractious)
measuring vital signs (temp. pulse, respiration, mm colour, capillary refil time)
-diagnostic tests (CBC, biochem, UA, FA, radiographs) - ASA classification (for anesthetic risk)
components of a physical examination
-signalment (age, sex, breed, whole/steralised, weight: BCS 1(skinny)-5(fatty)
-patient disposition ( temprement)
-vitals )temp, pulse, resp, heart, mm, crt)
-examination of all major organ system
what are the different ASA status
1: healthy (blood test normal)
2. mild systemic disease (geriatirc, obease)
3. obvious system disease (poorly controlled diabetes,anemia, fever)
4. severe systemic disease (severe dehydration,shock,high fever)
5. patient will die with/without surgery (severe trauma, advanced cardiac, kindney,liber, endocrine disease)
classE: emmergency ( c section)
what is pharmacokinetics
action of the body on drugs
what is pharmacodynamics
action of the drugs on the body (dhamaka due to drugs)
what are the different medicinal use of drugs
CSP
cure diseases: when disease is elimated, drug is withdrawn (stopped)
-supress diseases (control symptoms and maintain health without curing)
-prevent diseases (primary: prevent from getting the diseases. secondary: prevent current disease from progression)
what are drugs and how can they be classified
Drugs are natural or synthetic substances that alter the biological function of living organisms through their chemical actions.
Drug use:
Medicinal – treatment, prevention, diagnosis of disease.
Non-medicinal (social) – recreational purposes.
what is the nature of drug (porperties, characteristics)
physical:
1. state ofdrug at room temp: solid (tablet/capsule) liquid(oral syrup/ injectables) gas (anaesthetic gases)
- drug size
- drug shape (lock and key theory-> drug shape is complementory to receptor site
induced fit theory-> drug shape is not exactly complemetory to receptor site-> drug binds to recptor site and induce the recptor to undergo conformational change which allows for better binding)
size and shape of drug are key factor that setermune the binding selectivity. higher binding selectivity (bind more specifically) -> are specific in its action (can on fit into one type of receptor)
chemical:
organic or inorganic compounds. organic: contains a carbon basis, can be further classified into weak acid/ base electrolyte)
For a drug to carry out its appropriate action, it must:
be transported to the target site from the site of administration
interact with the receptor (can be activated/not)
(drug-receptor interaction)
be inactivated or excreted at a reasonable rate (appropriate/safe action of drugs-> must be excreted once done)
Requirements for drug-receptor interaction:
1.Appropriate size & shape to bind to the receptors by either:
Lock and key model
Induced-fit mode
2.Appropriate electrical charges for chemical forces of interaction to form
Chemical forces of interaction:
Covalent
Very Strong
Not reversible
Electrostatic
Ionic bonds – relatively strong
Hydrogen bonds - weak
van der Waals - very weak
Hydrophobic
weakest
what are the two main types of responses when drugs bind to receptors:
for drugs to exert and effect-> needs to be bound to a protein )eg receptor)
two possible response
Drugs that produce a change in the cell functioning are called agonists. (start a change)
Drugs that stop a normal function of the cell are called antagonists. (stop normal function)
Pharmacokinetics (PK)
Refers to the action of the body on a drug
It is the study of the movement/transformation of drug substances through body compartments (Absorption, Distribution, Metabolism, Excretion).
These properties are of great importance in the choice of drug type and drug administration route.
4 types of drug receptors
Intracellular receptors
Ligand-gated ion channels
Enzyme-linked receptors
G protein-coupled receptors
- Intracellular receptors
receptors located inside cell, ligand (drug) must be lipid soluble to corss the plasma membrane and bind to the receptor-> form receptor-ligand complex that moves to the nucleus-> binds to DNA causing gene expression (follwing the instruction)
response time: hrs to days
- Ligand- gated ion channel
ion channels located in plasma membrane
binding of ligant can cause the ion channel to open/close-> causing influx/exflux
or block the channel
affect intercellular ion concentration-> altered membrane potention-> changes in cell excitation
response time: within a few miliseconds
- Enzyme-linked receptors
ligand bind to receptor on the plasma membrane-> conformational change to the receptor-> activation/inhibitation of ezyme activity (changes, sometimes it fits the siganlling molecules smtimes it doesnt)
response time: minutes to hours
- G protein-coupled receptors
activation
receptors are linked to protein and associated at rest (usually at rest)
3 subunits: a- and By subunits
ligand binding causes a conformational change-> GTP is exchanged for GDP on the a-subunit -> a subunit dissociates from By subunit-> these subunits interact with other effectors, enzymes and ion channels
termination
GTPase hydrolyses GTP on the a-subunit to GDP -> a-subuit dissocates from the effectpr and reassociate with the By subunit-> interaction is terminated
response time: sec to mins
which dose response curve is preferred and why
sigmoid curve over hyperbolic curve. sigmoid curve is preferred as it plots the response of the drug with greater precision. This makes it easier to compare 2 drugs. (uses log function which gives us more realistic resuts)
what are the four key information dose response curve can give us
- potency of drug (how much of the drug needs to be given to get results)
-(EC50: effective concentration at 50%: dose required to abotain 50% of maximal effect) Lower EC50 indicates higher potency of a drug - slope
steep: more difficult to ahcieve precise control of the effects
shallow: more likely to experience side effects - maximal effecacy (E max) max effect achieveable by drug
4, threshold dose: minimal dose where drug effect is seen
Measuring clinical response
- median effective dose (ED50) : dose that produces therapuetic effect in 50% of testes pop
- median toxic dose (TD50)
Dose that produces toxic effect in 50% of tested population
If the toxic effect is lethal, then is known as LD50 (median lethal dose)
3.Therapeutic index (TI)
Ratio between TD50/ED50
It is a measure of drug safety (bigger ration, safer)
what are the different stages of pkarmacokinetics (movement/ transformation of drug substance)
absorption
distribution
metabolism
excretion
what is absorption and the different mechanism of drug absorption (different ways the drug is absorbed)
Refers to the transfer of a drug from its site of administration to the bloodstream
Mechanisms of drug absorption:
Passive diffusion- most common and needs to be water or lipid soluble.
Active transport- for drugs of high molecular weight or lipid-insoluble (cannot pass through cell membrane/ mix with blood)
Endocytosis- Drug is engulfed by the cell membrane
Exocytosis- opposite of endocytosis, drug is expulsed into extracellular space
Factors affecting absorption:
things that affect the drug from moving into the blood
1.Drug properties (size, water sol,stability)
2. Routes of administration (oral/parenteral absorption, some faster than others)
3. Blood flow to administration site (low blood flow-delay)
4.Surface area for absorption (larger-faster)
5.Dosage forms of drugs (liquid,solid, liquid faster than solid)
6.Drug-drug interactions (one can have adverse effects on the other)
7.Disease status of patients (sick-low blood flow)
(DDDDRBS)
what is Distribution
Refers to the process of drugs leaving thecirculation and entering extracellular space or cells of tissues.
Major compartments in body that are involved for distribution of the drug
Plasma (drug lives here when it enters the blood)
extracellular space (Interstitium ) 9can be distributed here)
Cells/tissues (or here)
Factors affecting distribution of drugs
(factors affecting the drug moving into the cell/outside cell )
1. Tissue permeability of drugs
2. Organ/ tissue size and perfusion rate (blood supply, faster,faster the rate of diffusion (smaller organ-faster distribution)
3.Binding of drugs to tissue components (less drug available for effect, think it gets trapped)
4. Miscellaneous
Age (eg older have less water, less rug moving around)
Health status
Diet (high fat, even fat sol drug may not be able to digest)
Drug interactions (binding)
Metabolism
Refers to the chemical modification of a compound by an organism
Main purposes:
-Inactivate drug
-Converting to water-soluble form for elimination by the kidneys
Primary site of metabolism
liver
end product of metabolism known as
metabolite
Factors affecting drug metabolism
1.Genetic differences
Each individual has varying capacity to metabolize drug. (different animals have different capacity to metabolise (inactivate/convert into water sol) drug (less ability-> drug stays in body longer having more effect)
2.Liver diseases (main organ invloved in drug metabolism)
Decreased blood flow to liver
Damaged liver cells
- Age
Neonates have immature liver function
Elderly people - decreased liver function and blood flow.
4.Cytochrome P450 enzyme induction/inhibition (get activated druing metabolsim, function: to convert drug to water sol )
what is excretion
Process by which a drug or metabolite is removed from the body.
Routes of excretion
Renal- most common
Faecal
Lung
Milk
Sweat, saliva and tears
Renal excretion can be affected by:
1.Urine pH – acidic & alkaline urine, promote excretion
2.Urine flow rate (slower-slower excretion)
3.Plasma protein binding (less will be excreted)
4.Competition for active tubular secretion ( compete for the same transport proteins in the renal tubules that actively secrete them into the urine)
5.State of renal function – renal failure
what are the Pharmacokinetic parameters (measuring pahrmakokinetic ADME of drug)
- bioavailability (F)
- Half life (t 1/2)
what is bioavailability (F)
Is the fraction of chemically unchanged drug (%) that reaches the systemic circulation by any route
higher bioavailability->longer the duration of action and ability to achieve desired therapeutic effects
(how much of the drug can be used after travelling to the bloodstream)
what is bioavailability affected by
1.The drug formulation (tablet, capsule, liquid faster cos no need to dissove)
2.Drug delivery method (eg iv has 100% bioavailability cos its goes straight into the bloodstream, oral , intraperitoneal route aka straught into abdomen-> first pass effect)
3.Dosage (amt of dru given)
4.Patient factors age-older-less water-less able to be transported to blood, diseases)
what is first pass effect
Drugs given by oral and intra-peritoneal route have to pass through the liver before reaching the circulation.
The liver metabolizes the drug, thus
the drug level that reaches the circulation is less than the actual dosage given. (reduced bioavailability)
what is half life (t 1/2)
Time required for concentration of drug to be reduced by half.
It is the measure of how long a drug is likely to remain active within the body.
Enables the dosage frequency to be determine (ie. How many times a day)
(longer time to take to become half-> less drug need to be give)
what are the common routes of drug administration
Parenteral (ie. Via injection)
Oral
Topical
Inhalational
Parenteral drug administration
3 common types:
Intravenous (IV) (fastest onset of action, higest bioavailability)
Intramuscular (IM)
Subcutaneous (SC)
Advantages of parenteral route:
Avoids first-pass effect in liver
High bioavailability
Ensures full dose is delivered
Disadvantage of parenteral route:
May be irreversible
Contamination leading to infections
Too rapid delivery can cause adverse reactions
what is oral drug administration and when is it used
Could be in the form of tablets, capsules, syrups, powders etc.
Commonly used for administration of medications at home.
adv of oral drug administration
Easy to administer
Limit the number of infections by parenteral
disadv of oral drug administation
Lower bioavailability due to first-pass effect by liver
Absorption is affected by gastrointestinal (GI) environment (eg ph affects sol of drug)
Slow onset of action
when is Inhalational drug administration used
Used for providing gas anaesthesia or for nebulization.
advantages of Inhalational drug administration
Fast onset of action
Systemic side effects minimized (gas only affects repiration, iv affcets the entire body)
diadv of Inhalational drug administration
Proper technique of using inhaler or nebulizer is required to ensure correct dosage is administered
