Definitions Flashcards
Absorption
Absorption - rate & extent to which a drug leaves its site of administration.
The rate and extent of drug movement from the site of administration to the systemic circulation
Acid
Arrhenius
Bronsted-Lowry
Lewis
Acid – proton donor or substance that increases [H+] of a solution
Arrhenius: a substance which is capable of producing hydrogen ions in an aqueous solution
Bronsted-Lowry: a substance which can donate a hydrogen ion to another substance
Donor = conjugate acid
Acceptor = conjugate base
Lewis: any compound that was a potential electron pair acceptor
Additive effect
Additive effect - second drug, acting with the first, produces an effect equal to the algebraic sum of the effects of each drug when administered individually (1 + 1 = 2)
Afterload
Afterload - load the heart is acting against during systole, gives rise to active tension in ventricular wall
- Isolated: force restricting muscle fibre shortening or weight/load that a contracting muscle must overcome prior to shortening.
- Intact: either the stress imposed on the ventricular wall during systole or the arterial impedance to ejection of the stroke volume.
Agonist
Agonist - A drug that binds to a receptor of a cell and triggers a response by the cell. An agonist often mimics the action of a naturally occurring substance.
Full – able to evoke maximal biological response
Partial – can exert a submaximal response despite high doses
Alkaloid
Alkaloid – nitrogen containing base of plant origin
Antagonistic effect
Antagonistic effect - second drug, acting with the first, produces an effect less than the algebraic sum of the effects of each drug administered individually (1 + 1
Baricity
Baricity – density of one solution compared to another
density (mass / volume) of liquid relative to CSF (CSF baricity = 1)
Base
Base – proton acceptor or substance that decreases [H+] when added to a solution
Bioavailability
Bioavailability – the fraction of administered dose which reaches the systemic circulation as intact drug (fraction absorbed x (1-ER)
The rate and extent to which a drug reaches its site of action (or plasma) from its site of administration
Bioequivalence
Chemical
Biological
Therapeutic
Bioequivalence - refers to two formulations of that yield similar concentrations in blood and Tx’s.
Chemical: meets chemical and physical standards
Biological: yields same concentrations in blood and tissue
Therapeutic: provides equal therapeutic benefit
Biophase
Biophase – the zone in which the drug comes into intimate contact with its molecular site of action
Buffer
Buffer – solution containing substances that have the ability to minimize pH changes when an acid or base is added to it
A solution which has the ability to minimise changes in [H+] when an acid or base is added to it.
Clearance
Clearance – volume completely cleared of a substance per unit time (note total body, organ specific)
- the volume of fluid from which a substance is completely removed per unit time (eg. via passage through an organ).
Concentration effect
Concentration Effect – the effect of increasing Fi of agent accelerating the equilibrium of PA/PI, consisting of concentrating component and augmentation component.
The effect which the inspired concentration of the anaesthetic agent exerts on the speed with which that agent attains equilibrium
The higher the inspired concentrations, the more rapid the rise in alveolar concentration
Context senstive half-time
Context sensitive half time – time required following cessation of an infusion designed to maintain a constant plasma concentration, of a given duration (the context) for plasma levels to fall by 50%.
Dead space
Dead space – part of the tidal volume that does not participate in gas exchange
Physiological dead space is divided into alveolar and anatomical:
- Anatomical - the internal volume of the conducting airways or that part of the inspired TV which is expired unchanged.
- Alveolar - Part of inspired gas which passes through the anatomical dead space and enters the alveoli but is not effective in gas exchange given
Apparatus dead space is volume rebreathed from apparatus before fresh gas enters patient airway.
Dependence
Dependence
Psychological – Need for a specific psychoactive substance either for its positive effects or to avoid negative psychological or physical effects associated with its withdrawal
Physical – a physiological state of adaptation to a specific psychoactive substance characterized by a withdrawal syndrome during abstinence, which may be relieved in part or in total by readministration of the substance
Density
Density – weight in grams of 1mL of that solution at STP, mass per unit volume (see universal gas law for gasses)
Drug
Drug - a chemical substance that produces an effect on a biological tissue.
Effect site equilibration time
Effect site equilibration time – time taken for equilibration b/w [drug] in plasma and biophase following an IV bolus
Elimination half time
Elimination half time – time taken for 50% fall in plasma conc during elimination phase – upper limit on how long it will take plasma conc. to fall (0.693 x Cl/VD)_
Emulsion
Emulsion – stable suspension of small globules of 1 liquid in a 2nd liquid
Emulsifier
Emulsifier – surface active agent that promotes the formation of an emotion
Eutetic mixture
Eutetic Mixture – a mixture of constituents at a ratio that produces the lowest temperature melting point
Half life
Half life - time required for elimination of 50% of drug from the body
Time necessary for drug concentration to fall by half whether by redistribution or elimination etc
Half time
Half time – time taken for plasma levels of drug to fall by 50% (0.693 x Cl/VD in single compartment model)_
Hepatic extraction ratio
Hepatic Extraction Ratio – proportion of drug irreversibly removed from each unit volume of blood during a single passage through the liver (0-1)
Hyperactivity
Hyperactivity - usual response achieved at lower than normal dosage (supersensitivity if denervated)
Hypersensitivity
Hypersensitivity - usually implies allergy to the drug
Describes an exaggerated or inappropriate immune response that cause tissue damage and even death of the host
Type I: antigen binds to mast cell IgE, resulting in degranulation (eg. Hay fever, anaphylaxis)
Type II: antibody-antigen reaction, resulting in complement activation and antibody-dependent cell-mediated cytotoxicity (eg. Transfusion reactions)
Type III: deposition of antigen-antibody complexes in the host tissue (eg. Serum sickness)
Type IV: (Delayed hypersensitivity) results from antigen presentation to T lymphocytes causing a release of cytokines. (eg. TB)
Hyporeactivitiy
Hyporeactivity - usual response achieved at larger than normal dosage
Idiosyncrasy
Idiosyncrasy - unusual effect (qualitative difference or extreme quantitative difference) of a drug, usually unrelated to dose, occurring in only a small percentage of patients.
Immunity
Immunity - decreased sensitivity as a result of Ab formation
Inotrope
Inotrope: drug affecting force of muscle contraction (usually used w/ respect to +ve inotropes). Many (though not all) sympathomimetics are useful as inotropes.
Local anaesthetic
Local Anaesthetic - drug producing reversible depression of nerve conduction when placed in close proximity to nerve fibres
Drugs that block, reversibly, the conduction of impulses in the peripheral or central nervous system when applied locally or regionally.
Metabolic rate
Metabolic rate – energy expended per unit time (basal equals 12 hours of fasting at rest)
MAC
Minimum Alveolar Concentration (MAC) – agent at 1 atm preventing gross purposeful movement to supramaximal stimulus in 50% of patients
Minimum alveolar concentration at one atmosphere of an agent that produces immobility in 50% of those subjects exposed to a noxious stimulus
Qualified clinically by: 100% O2, no premedconversionj to a partial pressure, as percentage of 1atm which then represents the tension of anaesthetic at the site of action in the brain; patient aged 25-35yrs
Minimum concentration
Minimum Concentration (Cm) – the minimum conc of LA necessary in vitro to block conduction of all nerve impulses in a given nerve w/n a reasonable time period (usu 10 – 15/60)
Mixed venous blood
Mixed venous blood – blood drawn from pulmonary artery, thus containing entire venous return from systemic circulation and attendant oxygen extraction and carbon dioxide addition
Mixture
Mixture – physical combination of 2 or more substances, each retaining its own properties
Nausea
Nausea – and unpleasant objective sensation referred to the pharynx and upper abdomen assoc with desire to vomit
Unpleasant subjective sensation referred to the pharynx and upper abdomen, associated with a desire to vomit.
Opiate
Opiate – drugs derived from opium
strictly substances derived from Opium ie naturally occurring opioids.
Opioid
Opioid – all exogenous substances that bind specifically to any subtype of opioid receptor to produce some agonist effect
Opioid, endogenous – endorphins, dynorphins, enkephalins
Opium
Opium – dried powdered mixture of alkaloids from unripe seed capsules of Papaver sominiferum (opium poppy)
Pain
Pain - an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
Physiological pain – operates as a protective system, warning of contact with potentially damaging stimuli. Different receptors (low threshold for innocuous stimuli, high threshold nociceptors) allow such differentiation.
Pathological pain – pain associated with tissue damage or damage to nervous system. Prolonged stimulus causes modification of threshold of nociceptors, hyperalgesia and allodynia.
Acute pain – pain of recent onset and probable limited duration; usually with causal and temporal relationship to injury or disease.
Chronic pain – (usu >3 months) commonly persisting beyond the time of healing of an injury and may not have a clearly identifiable cause.
unpleasant sensory and emotional experience associated with actual or potential tissue damage, or expressed in terms of such damage.
Partition coefficient
Partition coefficient – ratios of concentration of dissolved agents present between two phases at a given temperature at equilibrium (equal partial pressures)
Ratio of amount of gases in two phases, at equilibrium, at stated temperature
Pharmacogenetics
Pharmacogenetics – study of hereditary (genetic) factors in variability of drug response
Preload
Preload - load on the myocardial m’s just prior to the onset of cxn. & determines the end diastolic fibre length prior to onset of contraction.
PRELOAD
- Isolated: load imposed on muscle before contraction, obtained by hanging a small weight at the end of resting muscle.
- Intact: ventricular wall tension at end diastole, determined by EDV, EDP and wall thickness, and approximated by PAWP/CVP.
Potentiation
Potentiation - a non-toxic agent ’ing the toxicity of a toxic agent.
Receptor
Receptor - the molecules of a biological target with which a drug reacts to produce its biological effect
Regurgitation
Regurgitation – passive, not reflex and not forceful
Retching
Retching – may precede vomiting, involves rhythmic contraction of same muscle groups, without expulsion of contents
Second gas effect
Second gas effect – high volume uptake of one agent (N2O usually) to increase the rate of increase of Fa/Fi of a second gas (classically volatile but also O2).
Uptake of one agent can increase the rate of uptake of a second agent
Sensitisation
Sensitization (Reverse tolerance) - acquired hyperactivity due to prior exposure to a drug.
Shock
Shock - physiologic state characterized by a significant reduction in systemic tissue perfusion, resulting in decreased tissue oxygen delivery
Sleep
Sleep – imperative, natural, periodic state of reversible unconsciousness, rousable by sensory stimuli
Solubility
Solubility – amount of specific substance that will dissolve in each vol. of a specified liquid at specified temp and pressure
Solution
Solution – homogenous mixture
Specific gravity
Specific Gravity – ratio of density of a solution compared to water
Suspension
Suspension – heterogenous mixture
SVR
SVR - resistance or impediment of the systemic vascular bed to blood flow, mainly from arterioles
Synergistic effect
Synergistic effect - second drug, acting with the first, produces an effect greater than the algebraic sum of the effects of each drug administered individually (1 + 1 > 2).
Sympathomimetic
Sympathomimetic - sympathomimetic drugs are those which evoke similar responses to those produced by the endogenous activity of the symp. NS.
Tachyphylaxis
Tachyphylaxis - acquired hyporeactivity that develops rapidly (mins/hrs) after only a few doses of a drug.
Rapid deterioration in response to repetitive administration of a pharmacologically active substance.
Tolerance
Tolerance - acquired hyporeactivity over time (days-wks) due to prior exposure to the drug (or another related drug => cross tolerance)
The demonstration of decreased receptor response to a given concentration of agonist
The need to increase the dose of (opioid) agonist to achieve the same (analgesic) effect previously achieved with a lower dose
Vapour
Vapour – gaseous state of a substance that is in equilibrium with the liquid or solid state, which is capable of forming a solid or liquid at the temperature of the vapour (Ie below critical temperature)
The gaseous form of a substance when the ambient temperature is below its critical temperature
Viscosity
Viscosity – fluids resistance to flow (ration of shearing stress to velocity gradient), fluids think honey, but gases get more viscous with increasing temperature
Vomitting
Vomiting – forceful expulsion of gastric contents via mouth, a survival reflex to expel toxins
Volume of distribution
Volume of distribution – the apparent volume which a drug would occupy if all of the drug present in the body distributed uniformly at the concentration present in the blood
Absolute humidity
Weight of H2O vapour in one litre of gas
Units: mg/L or gm / m3
0C= 4.8ml/l, 20C = 17mg/l, 37C = 44mg/l
Adabiatic change in state of a gas
In an isolated system, occurs when a change in pressure or volume results in a change in temperature.
Eg. If a compressed gas expands adabiatically, cooling occurs
Adaption
The temporal progressive reduction in the rate of firing of receptors in response to a continuous sensory stimulus
Eg. Adaption of pressure receptors on bum
Ageing
A normal physiological process of degeneration beginning around 30 and proceeding at a variable rate, with obvious changes becoming apparent around 60, and the end point being death.
Allodynia
Innocuous stimulus leading to pain
Alveolar dead space
That part of the inspired gas, which passes through the anatomical dead space to mix with alveolar gas, but is not perfused with blood and does not contribute to gas exchange. i.e. ventilated but not perfused alveoli
Alveolar gas equation
PAO2=PIO2 – PACO2/R + F
Ampere
A current which if maintained in two straight parallel conductors of infinite length and negligible cross section, placed one metre apart in a vacuum would produce between these conductors a force equal to 0.20 N/m of length
Amphipathic
Part hydrophilic, part hydrophobic
Analysis of variance (ANOVA)
A parametric test used to compare the means of two or more groups
Anaphylactic reaction
An acute hypersensitivity reaction which occurs in patients previously sensitised to the particular antigen.
Mediated by IgE attached to mast cells
Anaphylactoid reaction
Due to direct release of mediators (complement or direct histamine release) from the mast cells by the action of the causative drug or agent
Anatomical dead space
Volume of gas in airways excluding alveoli
Measured by Fowler’s method.
Antigen
A substance capable of stimulating the immune system of the host to produce a specific response to it.
Apparent volume of distribution
The imaginary volume into which a drug would need to distribute so that it has the same concentration as plasma
Autonomic nervous system
Efferent pathway controlling action of involuntary organs and tissues. Main function is homeostasis
Avagadro’s hypothesis
Equal volumes of gases at equal condition of pressure and temperature contain equal number of particles
Bainbridge reflex
Atrial reflex control of HR
Increase in atrial pressure causes increase in HR – stretch receptors transmit afferent signal through vagus to medulla
- infusion of blood or saline in
normovolemic subject causes reflex increase in HR independent of ↑BP
Bartter’s syndrome
Idiopathic hyperplasia of JG cells
Associated with hypokalaemia and increased levels of renin, AII, and aldosterone, but with normal BP
Bezold-Jarisch reflex
Coronary chemoreflex
Injection of vasoactive chemicals into coronary artery leading to apnoea, followed by rapid breathing, hypotension and bradycardia
Bias
Systemic deviation from the truth
Binomial distribution
Exists if a population contains items which belong to one of two mutually exclusive categories (eg male or female)
Biotransformation
The enzymatic conversion of a drug into a more polar, less lipid soluble molecule which is suitable for excretion
Phase I: oxidation, reduction, hydrolysis
Phase II: glucuronidation, sulphation, aceylation
Blood/gas solubility or partition coefficient
Also called “Ostwal solubility coefficient”
The ratio of the concentration of dissolved gas to the concentration in the gas phase at equilibrium
Determines the induction time
Bohr effect
Alteration of blood pH changes haemoglobins oxygen carrying capacity
rightward shift of the oxyhaemoglobin curve with ↑H+ concentration and ↑PCO2 reflecting lower affinity of Hb for oxygen.
Boiling point
The temperature at which its saturated vapour pressure becomes equal to ambient pressure
Temperature at which liquids becomes gases
Boyle’s Law
At a constant temperature the volume of a given mass of gas varies inversely with the absolute pressure
for a given mass, provided the temperature is constant, the volume is inversely proportional to pressure
→ V x P = K
Buffer power
buffer power = d{B+}/dpH
Here d[B+] = change in concentration of base
dpH = change in pH
Bulbs of Krause,
Ruffini
Krause: cold thermoreceptors in dermis
Ruffini: heat thermoreceptors in dermis
Candela
The luminous intensity of a surface of 1/600,000m2of a black body radiator at the temperature of freezing platinum under a pressure of 101,325 kPa
Capnography
The graphical measurement of CO2 vs time
Carotid chemoreceptor reflex of BP control
Decreased perfusion pressure reduces oxygenation, leading to increased pCO2 and stimulation of the vasomotor center of the brain stem, via Hering’s and vagus nerves.
Case control study
An observational study that begins with a definition of the outcome of interest and then looks backward in time to identify possible exposures, or risk factors, associated with that outcome.
Central limit theorem
As the sample size increases, the shape of the sampling distribution approaches normal shape, even if the distribution of the variable in question is not normal.
Charle’s Law
At a constant pressure the volume of a given mass varies directly with the absolute temperature
Chemoreceptor
Those receptors that are stimulated by a change in the chemical composition of the environment in which they are located
Chi square (X2) (Pearson’s)
Used to compare independent groups of categorical data
X^2 = sum (O=E)^2/E
where: O= observed number in each cell; E= the expected number in each cell
Chiral molecule
Describes a molecule that has a centre (or centres) of three-dimensional asymmetry (eg. C, N, S)
Clark’s occupancy theory
There is a dynamic reversible relationship between drug and receptor
Coagulation
Coagulation is a biological amplification system in which a few initial substances activate, by proteolysis, a cascade of circulating precursor enzymes.
Cockcroft-Gault formula
Creatinine clearance = ({140-age} x wt in kg)/[814 x serum cr]
multiply 0.85 for females.
Coefficient of variation
SD/mean
Cohort study
A cohort study observes a group of patients forward in time in order to record their eventual outcome.
Colligative properties
Properties of a solution that depend only on the particle concentration.
Ie the number of particles per unit volume
They are: vapour pressure depression, freezing point depression, boiling point elevation, osmotic pressure
properties of a solution that depend only on the number of freely moving particles and not on the nature of those particles. eg osmotic pressure, freezing point depression, vapour pressure.
Conduction
Transfer of heat at a molecular level. (cannot occur in a vacuum)
Q=KA(t1-t2)/d
Where: Q=heat loss
A= area of transfer
d= thickness of material over which heat has to travel
K= thermal conductivity of the substance
Confidence limits
The lowest and highest values of the CI
Confounding
Effect of imbalance and effect on outcome
Constitutional or structural isomers
molecules with the same empirical formulae whose atoms are connected to each other in a different sequence.
Eg. Isoflurane, enflurane
Contractility
A property of cardiac muscle which defines the work the heart can perform at a specified load.
Convection
A process of heat transfer through a stream of fluid. (Cannot occur in vacuum)
CP50
Plasma concentration required to produce a response in 50% of the population (or to produce a half-maximal effect)
CP95
Plasma concentration required to produce a response in 95% of the population (or to produce 95% of maximal effect)
Critical pressure
Minimum pressure for liquefaction at critical temperature
The vapour pressure of a substance at its critical temperature.
Critical temperature
The temperature above which a gas cannot be compressed into a liquid no matter how high the pressure is increased
Nitrous oxide 36.5 dC
O2 -119 dC
CO2 31 dC
Cushing reflex
Hypertension, bradycardia secondary to an increased ICP
When ICP is increased, the blood supply to the vasomotor area is compromised, and the local hypoxia and hypercapnoea increases its discharge. The resultant rise in BP restores the blood flow to the medulla, but the HR decreases due to the baroreceptor response.
Dalton’s law of partial pressure
In a mixture of gasses the pressure of each gas is the same as that would be exerted if it alone occupied the container.
the pressure exerted by a mixture of gases (or gases and vapour) is equal to the sum of the pressures which each gas would exert if occupying the same space alone.
NB at high pressures, the compressibility of some gases causes deviations in behaviour from predicted values.
Defaecation
The active expulsion of rectal contents to the external environment
Descriptive statistics
Describe a collection of data (mean, median, standard deviation, variance)
Dew point
The dew point is the temperature to which a gas must be lowered in order for water to condense from it. Ie the partial pressure of water vapour equals the saturated vapour pressure
Dibucaine number
Refers to the % inhibition of the esterase (in hydrolysing benzoyl choline) by Dibucaine 10-5 (Nupercaine) The D gene is resistant to inhibition.
Normal activity > 70%, atypical activity
Diffusional hypoxia
Fink effect
Returning N2O displaces the alveolar O2 from the lungs, lowering the alveolar O2 concentration
Distribution
The movement of drug from the systemic circulation to other body compartments
Drug interaction:
Additive
Synergistic
Antagonistic
Additive: the effect of a drug combination is the sum of the effects of each drug (eg potent volatiles)
Synergistic: the effect of a drug combination is greater than the sum of the effects of each drug (eg.opioids and volatiles)
Antagonistic: the effect of a drug combination is less than the sum of the effects of each drug
Eaton-Lambert effect
Myasthenic syndrome – muscle weakness caused by antibodies to presynaptic Ca2+ channels at nerve ending, thus preventing ACh release
ED50
Dose required to produce a response in 50% of the population (or to produce half-maximal effect)
ED95
Dose required to produce 95% depression of the twitch response of the adductor pollicis muscle to stimulation of the ulnar nerve.
Efficacy
The strength of the drug-receptor interaction in causing effect. It describes the response to a certain % receptor occupancy.
Electroencephalogram (EEG)
A continuous register of the summated electrical activity of the brain recorded by electrodes on the scalp
EMF (alternate Nernst equation)
EMF(mv) = +- 61.5log ([] inside/[ ] outside) (at 37 degrees C)
enantiomer
(substances of opposite shape)
a pair of molecules existing in two forms that are mirror images of one another (right and left handed) but cannot be superimposed. Eg. S- and R- bupivacaine
enantiomers and diastereoisomers are subtypes of stereoisomers.
Endocrine gland
Organs that secrete specific substances (hormones) which are released directly into the circulatory system and which influence metabolism and other body processes.
Endocrine system
The system of glands and other structures that elaborate internal secretion (hormones) which are released directly into the circulatory system and which influence metabolism and other body processes
Epidemiology
The study of disease in populations
Excretion
Irreversible elimination of the drug or its metabolites from the body
Exponential function
One where the rate of change of a variable is proportional to the magnitude of the variable
Fenn effect
The greater the amount of work performed by the muscle, the greater the amount of ATP that is cleaved
FEV1
Fraction of the vital capacity expired during the first second of a forced expiration
Fick principle
The amount of a substance taken up by an organ per unit of time is equal to the arterial level of the substance minus the venous level (a-v difference) times the blood flow
Fick’s law of Diffusion
rate = permability coefficient x (C1-C2) x (area/thickness)
First pass effect
Occurs when orally-administered drugs enter the systemic circulation in concentrations that are much lower than if the drug was administered systemically. Eg. Betablocker doses o vs iv
Fisher’s exact test
For use in 2x2 tables, when one or more of the variables
Fluoride number
Refers to the % inhibition of the esterase by fluoride 5 x 105M
Free water
The amount by which the water content of a solution (eg. Urine) exceeds that needed to form a solution isosmotic with plasma
Functional residual capacity
Volume of gas in the lung after a normal expiration
Equals ERV+RV = 0.7+1.1 = 1.8l = 30ml/kg
Gain
The ratio of the secondary change evoked by a given mechanism to the initiating change itself
Gas
The gaseous form of a substance when the ambient temperature is above its critical temperature
Gastro-ileal reflex
Raised secretory and motor activity in stomach increases ileal activity
Gaussian distribution
Normal distribution curve
GFR
GFR = Uw x V / Pw Uw = urine conc of W V = urine volume per unit time Pw = arterial plasma concentration
Goldman equation
Used to calculate the magnitude of the resting membrane potential (RMP)
Dependent on the concentrations and the permeability for each ion species present.
Graham’s law
Rate of diffusion varies with the inverse of the square root of molecular weight
the ratio of diffusion of gases through certain membranes is inversely proportional to the square root of the molecular weight.
Haemopexin
Binds to haem when haptoglobin is saturated
Hair hygrometer
A hair is attached to a dial via a system of levers, and lengthening of the hair is linear with increasing humidity. Accurate over the 30-90% range of relative humidity
Haldane effect
As Hb releases O2 it can carry more CO2 without a rise in pCO2
Deoxygenation of blood increases its ability to carry CO2 since the reduced form of Hb better buffers H+ (more CO2 transported as bicarbonate) and binds CO2 as carbamino groups.
Haptoglobin
An α2-globin. Binds to the globin moiety of free haemoglobin that may be in the plasma
Hawthorne effect
The actual process of study (patient explanation, informed consent, measurement, follow-up) may result in more favourable outcomes in such patients.
Heat
The energy which can be transferred from an object at a higher temperature to one at a lower temperature
A manifestation of the level of molecular kinetic energy present in a substance
Henderson-Hasselbalch equation
pH = 6.1 + log ( HCO3-/ {0.03 Pco2})
pH = pKa + log [HCO3]/ (0.03 x pCO2)Henry’s law
The concentration of a gas in a liquid is proportional to its partial pressure
Hering-Breuer reflex
Inflation reflex: increase in duration of expiration produced by steady lung inflation
Hormone
A chemical substance that is secreted into the body fluids by one cell or a group of cells that exerts a physiological control effect on other cells of the body
Peptide hormone: hypothalamus, pituitary, pancreas, parathyroid, gut, heart
Amines: thyroid, adrenal medulla
Steroid: sex hormones, adrenal cortex.
Humidity
Amount of water vapour present in air
Hyperalgesia
Mildly painful stimulus leading to severe pain
Immune system
A series of complex cellular and humoral elements that can interact with many different types of foreign molecular structures (antigens) to provide host defence against foreign substances
Incidence
The number of individuals who develop a disease (ie new case) in a given time period
Inferential statistics
That branch of statistics where data are collected and analysed from a sample to make inferences about the larger population (using parametric and non-parametric tests.)
Inspiratory capacity
Maximal inspiration following passive expiration
IC=TV+IRV = 7ml/kg + 45ml/kg = ~50ml/kg
Inspiratory reserve volume
Air inspired with a maximal inspiratory effort in excess of the tidal volume.
45ml/kg
Intestino-intestinal reflex
Over distension of one segment of intestine relaxes the rest of the intestine
Intracranial pressure
The pressure within the cranial vault relative to atmospheric pressure (gauge pressure)
Intravenous anaesthetic agent
A drug or combination of drugs which will induce anaesthesia, safely and reversibly, when injected in sufficient doses and which could also be given intermittently or by infusion for maintenance
Ionic permeability
Net quantity of ion that will diffuse across each unit area of the membrane per unit [ ] gradient
Isohydric principle
An assessment of the concentrations of any one acid-base pair can be utilised to provide a picture of overall acid-base balance in the body.
Isomer
Constitutional: compounds with the same empirical formulae whose atoms are connected to each other in a different sequence. Eg. Isoflurane, enflurane
Stereoisomers: molecules that not only have the same empirical formula but which also have the atoms attached in the same sequence. They differ, however, in the three-dimensional arrangement of those atoms.
Enantiomers: mirror images: eg. S- and R- bupivacaine
Diastereoisomers: oriented around a carbon double bond: eg. Atracurium.
Kelvin
The fraction 1/273.16 of the triple point of water (that temperature at which water can exist as solid and gas = 0.16 dC
Kilogram
The mass of the international prototype kilogram kept at the international Bureau of Weights and measures in France
Kruskal-Wallis test
A non-parametric equivalent of ANOVA
La Chatelier Effect
Shift in equilibrium of carbonic anhydrase reaction to CO2
H+ + HCO3= H2O + CO2
Lambert-Beer Law
There is a non linear, power relationship between the light intensity transmitted, and the incident light intensity
It=Iie-A
the intensity of light passing through a solution decreases exponentially with the concentration of solute and distance traveled through solution
I trans = I incident e^-A
A = DEC
(A = absorption)
D = distance, E = extinction coefficient, C= concentration
Laminar flow
Q proportional to [pi (P1-P2) r^4] / 8nl
n = viscosity (poises)
l = length of tube in cm
Q = flow of gas (ml/sec)
Note that flow is proportional to pressure drop, and to the radius to the power of 4, and inversely proportional to viscosity and length.
Laplace’s law
The equilibrium relationship between transmural pressure difference, wall tension, and radius of curvature in a concave surface, for a sphere: dP=2T/R; for a cylinder: dP=T/R
In a cylinder, for a constant internal pressure, wall tension varies directly with the radius
In a sphere, for a constant internal pressure, wall tension increases at twice the rate as the radius.
Latency
Time from drug introduction to onset of action
Latent heat
The amount of heat required to change the state of a substance, when it is at the temperature required to change state.
Latent heat of vapourization
The amount of heat required to change a liquid to the gaseous phase.
Lissauer’s tracts
Collections of axons that can travel up or down 1-2 segments
MAC awake
MAC at which consciousness is regained or at which 50% of patients will respond to a simple command.
Useful to predict recovery, usually ~0.6 MAC
MAC-95
MAC absolving 95% of the reflex response
MAC-BAR
MAC that blocks adrenergic response in 50% of patients
NA used, measuring BP & HR
MAC required to block adrenalin response (BP and HR increase mediated by catecholamines) in 50% of patients exposed to standard stimulus.
MAC-hr
Duration of exposure to 1 MAC of agent
Mann-Whitney U test
A non-parametric equivalent to the unpaired t-test
Mayer waves
Slow oscillations in arterial pressure that occur at the rate of about one per 20-40 seconds during hypotension.
Hypoxia stimulates chemoreceptors, stimulation raises BP, removing the stimulus to the chemoreceptors, and initiating a new cycle
Meta-analysis
Process of combining the results of different trials to derive a pooled estimate of effect.
Metre
The distance that light travels in a vacuum in 1/299,792,458 of a second
Molality
The number of moles of a solute per kilogram of solvent = this is independent of temperature
Mole
The amount of a substance which contains as many elemental entities as there are in 0.012Kg of carbon12
Monro-Kellie doctrine
The intracranial volume is fixed and for the intracranial pressure to remain constant reciprocal changes must occur between the volumes of the individual components of the intracranial contents.
Motor unit
Consists of an anterior horn cell, a motor neuron and the muscle fibres which it supplies.
Nebulisation
The breaking up of liquid water into tiny droplets, that can be held in air in suspense
Nernst equation
E = RT/FZ ln []o/[]i
where: E=equilibrium potential R= gas constant T= absolute temperature F= faraday (no of coulombs per mole of charge) Z= valence of the ion +/-
Nernst potential
The potential level across the membrane that will exactly prevent net diffusion of an ion in either direction
Newtonian fluid
Those fluids for which the shear rate is proportional to the shear stress.
Null hypothesis
There is no difference between the population variables in question
Number needed to treat
(NNT) the reciprocal of the absolute risk reduction
describes the number of patients who need to be treated in order to avoid one adverse event.
Odds ratio
The ratio of odds of an outcome in those treated vs. those not treated – usually a case-control study
OR 1 = no change
An estimate of the risk ratio (The proportion of patients with an outcome who were exposed to a risk factor vs. the proportion not exposed.)
Oil / Gas partition coefficient
The amount of gas in equal volume of two phases at stated temperature, independent of pressure at equilibrium
Oncotic pressure
Colloid osmotic pressure
That part of the osmotic pressure of plasma or interstitial fluid which is due to protein
One-tailed t-test
Used to look for a difference between two groups in only one direction (ie larger or smaller)
Opsonization
Coating of a target cell with certain complement proteins
Osmolality
Number of osmoles of solute per kilogram of solvent. One osmole contains Avogrado’s number of particles This is independent of temperature
Osmolarity
Number of osmoles of solute per litre of solution. This is altered by temperature changes because of the expansion of the solution.
Osmole
The mass of a substance which yields 6.02 x 1023 osmotically active particles
Overdrive suppression
The automaticity of pacemaker cells is depressed after a period of high frequency excitation
Eg. Firing of the SAN tends to suppress the automaticity in the other foci
Oxygen flux
Amount of oxygen delivered to the peripheral tissues per minute
P value
The probability of the event occurring by chance if the null hypothesis is true
P50
The PO2 at which the haemoglobin is half saturated with O2
P50 = 27. (HbF P50 = 20.)
Parameter
Summaries of population data (compared to statistics, which are summaries of sample data)
Defined by Greek letters (μ,σ, etc.)
Partial pressure of a gas in a liquid
That pressure which in the gaseous phase in equilibrium with the liquid would produce the concentration of gas molecules found in the liquid.
Pathological / clinical pain
Usually due to tissue or nerve damage and if unchecked, leads to sensitisation of the peripheral and central nervous system.
Pearson correlation coefficient
(r) a measure of how closely the data points on a scatterplot assume a straight line (value lies between –1 & 1)
It is a measure of association.
Perfect Gas Law
Absolute pressure at a given volume varies directly with the absolute temperature
Peristalsis
Progressive contraction of successive sections of circular muscle
pH
Negative log of the active hydrogen concentration
Introduced by Sorensen in 1909
or equivalently: aH+=10(-pH)
where aH+ = activity of hydrogen ion.
Pharmacodynamics
The study of the biochemical and physiological effects of drugs on the body
Physiological dead space
Sum of the alveolar and anatomical dead spaces.
Measured by the Bohr equation.
INSERT BOHR EQUATION
the ratio of the physiological dead space to the tidal volume can be estimated by measurement of the PCO2 in arterial blood and mixed expired gas.
Physiological pain
The normal protective response to noxious stimuli and warns of impending tissue damage
pKa
The negative logarithm (to the base 10) of the dissociation constant: HA↔H++A-
At pH equal to pKa, the acid is 50% dissociated (ie there are equal amounts of HA and A-)
Ionisation of acids is greatest at alkaline pH, ionisation of bases is greatest at acidic pH.
Poiseuille’s law
Q = pi(P1-P0)r^4 / 8nl Q = flow pi/8 = constant of proprtionality v = viscosity l = length r = radius P1-P0 = pressure gradient
Poisson distribution
Describes (rare) random processes, where there is no knowledge of how much did not occur. Eg. Given a rate that events occur (at random), how many events occur in a set time?
Potency
The (reciprocal) relationship between the therapeutic effect of a drug and the dose necessary to achieve that effect
Power (statistics)
The likelihood of detecting a difference between groups if one exists (ie preventing a type II error)
Pressure interconversion – 1atm
1 atm = 101.325 kPa = 1013.250 mbar = 760mmHg = 1035.08cm H2O = 14.696 psi (lb/in2)
Prevalence
The current number of cases (pre-existing and new)
Probability
A theory of uncertainty that is used as a rational means of dealing with an uncertain world
Protein binding
The percentage of a chemical that binds to proteins
Pulmonary chemoreflex
Juxtacapillary receptors in the lung respond to intravenous administration of chemicals. The reflex response is apnoea, followed by rapid breathing, bradycardia and hypotension.
Racemic mixture
Two enantiomers are present in equal proportions
Eg bupivacaine, ketamine. (the S form of ketamine is more potent and less likely to cause emergence delirium than the R form)
Radiation
Loss of energy from the body by electromagnetic radiation. Occurs through a vacuum, and does not require physical contact
Q=kT4
Rate
Measure of frequency of an event
Receptor potential
The alteration in membrane potential, generated by the stimulus, at the nerve ending associated with the receptor
Referred pain
Pain felt not at the site of origin (viscous or deep somatic) but in a somatic structure some distance away
Regurgitation
The effortless passive movement of gastric contents into the oesophagus and possibly the pharynx and oral cavity
Relative humidity
The ratio between the actual vapour content that exists to the maximum possible water content at the same temperature
Relative humidity = actual vapour pressure/saturated vapour pressure
Renal clearance
The volume of plasma from which that substance is completely cleared by the kidneys per unit time
Residual volume
The gas remaining in the lung after a maximal expiration
15-20ml/kg = 1.2l in adult male
Respiratory dead space
The space in the conducting zone of the airways occupied by gas that does not exchange with blood in the pulmonary vessels.
Reticular activating syste
A functional area of CNS, anatomically based on the reticular formation in the mid brain and medulla, responsible for the alert, conscious state and involved in vegetative functions
Risk ratio
Incidence rate of an event (outcome) in an exposed population versus the incidence rate in a non-exposed population.
Usually associated with a prospective cohort study
If the risk ratio is greater than 1.0, there is an increased risk with that exposure.
Rosenthal Correction Factor
Deltaph/deltaT = -0.015 pH units/degree C
i.e. temp = pH
Sample
A group taken from a population
Saturated vapour pressure
Equilibrium pressure point at which number of molecules leaving equals the number of molecules entering the liquid phase
This is independent of atmospheric pressure, dependent only on the temp and the physical characteristics of the liquid
Water at 20C 17gm/m3, at 37C is 44gm/m3 (ie 2.5 times)
Second
The time for 9,162,631,770 vibrations of a cesium133 atom
Second gas effect
Uptake of one agent can increase the rate of uptake of a second agent
Seebeck effect
If in a circuit made from two dissimilar metals, the junctions are set at different temperatures, there is a current generated in proportion to the temperature difference
Sequential analysis
A collection of valid statistical methods used to repeatedly compare the outcome of two groups while a trial is in progress. This allows a clinical trial to be stopped as soon as a significant difference between groups is identified.
Sleep
A temporary state of unconsciousness which can be overcome by sensory stimulation
Specific heat
The number of joules of energy required to raise the temperature of 1 Kg of a substance by 1K (Units kJ/kgK)
Water: 4.19kJ/kgK
Blood: 3.6kJ/kgK
Splay
Apperance of a substance in the urine before the Tm is reached
Staircase effect (treppe)
Progressive increase in strength in contractions of skeletal muscle when starting from at rest. Thought to be due to increased concentration of calcium ions in cytosol
Standard deviation
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Standard error
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Statistic
defines a sample
Stereoisomers
molecules that not only have the same empirical formula but which also have the atoms attached in the same sequence. They differ, however, in the three-dimensional arrangement of those atoms – i.e. have a chiral centre.
Enantiomers: mirror images: eg. S- and R- bupivacaine
Diastereoisomers: oriented around a carbon double bond: eg. Atracurium.
Student’s t-test
A parametric test used to compare the means of two groups
Summation
Adding together of individual twitch contractions to increase the intensity of overall muscle contraction.
Swallowing
The active movement of oral or pharyngeal contexts into the stomach
Synaptic transmission
The transmission of nerve signals from one neuron to another through interneuronal junctions called synapses
Temperature
A measure of the tendency of heat to travel between substances
Thermoneutral zone
The environmental temperature in which body temperature is normal and remains normal while heat production and evaporative heat loss both remain at a minimum.
Tidal volume
Normal inspiration to passive expiration
7ml/kg = 500ml in adult male
Time constant
The time constant is the time at which the process would have been complete had the initial rate of change continued
Tonicity
The effective osmolality of a solution
Total (physiological) dead space
Volume of gas not equilibrating with blood i.e. wasted ventilation
Transducer
A device that changes a signal from one form of energy to another
Transport maximum Tm
The limit of the amount of material a particular active reabsorptive system can transport per unit time because of saturation of the membrane transport proteins.
Eg. Glucose = 375gm/minute
Traube Hering waves
Fluctuations in BP associated with respiration
Type 1 error
Type 2 error
Type I: α error. Where one rejects the null hypothesis incorrectly – false conclusion of effect
(eg. More likely with multiple testing)
Type II: β error. Where one accepts the null hypothesis incorrectly– false conclusion of no effect
(more likely with inadequate sample size)
Universal law of constant proportion
As Y declines it does so at a rate proportional to its own magnitude
Unpaired T-test
Used to compare two independent groups
Van’t Hoff equation
Used to calculate osmotic pressure Osmotic pressure = n x (c/M) x RT N= number of particles into which the solution dissociates C = concentration in g/l M = molar weight of the molecules R = universal gas constant = 0.082 T = absolute temperature (K)
Vapour pressure
The pressure exerted by the molecules escaping from the surface of a liquid to enter the gaseous phase
Vapour pressure of water
Partial pressure of water vapour in a gas mixture. When vapour pressure equals atmospheric pressure, boiling occurs
Variance
Vascular compliance (eqn)
Vascular compliance = increase in volume/increase in pressure
Compliance = distendibility x volume
Vascular distensibility (eqn)
Vascular distensibility = increase in volume / (increase in pressure x original volume)
Viscosity
Ratio of shear stress to shear rate of fluid (dimensions dyne/cm2 = 1 Poise)
Shear stress: force applied in the direction of motion to the contact area.
Shear rate: ratio of the velocity of the plate to the depth of the liquid
Vital capacity
Maximal inspiration followed by a maximal expiration
VC=ERV+TV+IRV =1.0+0.5+3.3 = 4.8l in adult male (15+7+45=~60ml/kg)
Water content
Total amount of water present per unit volume of a gas. (vapour + fine suspended drops) Units are mg/l
Yate’s correction
For five or less values in a chi-squared test
Z transformation
Converts any normal distribution curve to a standard normal distribution curve, with mean = 0, SD = 1
Zymogen
Pro-enzymes requiring proteolytic cleavage to become active
Acidemia
arterial blood pH 44 nmol/L
ACIDOSIS
an abnormal process or condition which tends to lower arterial pH if there are inadequate secondary changes in response to the primary disease process
- Respiratory - 1º change in CO2
- Metabolic - 1º change not in CO2
ACTIVITY
the effective concentration of a substance in a reacting system
ADIABATIC HEAT
heat produced when a gas is compressed
Affinity
Avidity with which a drug binds to a receptor (analogous to potency), or ability to bind to a receptor and form a stable complex.
Alkalemia
arterial blood ph > 7.45 or [H+]
ALKALOSIS
an abnormal process or condition which tends to raise arterial pH if there are inadequate secondary changes.
AMPLITUDE LINEARITY
amplifications of the signal should be equal throughout the entire signal range to prevent distortion.
ANAESTHESIA
without sensation.
-General: controlled production of unconsciousness
ANALOGUE SIGNAL
where the output of the transducer in either volts or amps varies directly with the input signal
ANAPHYLAXIS
clinical syndrome produced by IgE type I hypersensitivity resulting from antigen-antibody reaction at surface of mast cells. The syndrome manifests as red rash/flush, bronchospasm, collapse, angioedema, GIT symptoms. Requires prior exposure to antigen.
Andoe
positive electrode to which negative ions attract
ANREP EFFECT
- intrinsic regulatory mechanism of the heart whereby an abrupt increase in afterload produces transient increase in LVEPD and decrease in SV allowing prompt restoration to near baseline values.
Atenuate
Reduce
ATPS
Ambient tempreature and pressure, saturated with water vapour (Tamb, Pb, PH2O)
AUTOREGULATION
ability of organ/body to maintain homeostasis in the presence of altering physiological conditions.
AVOGADRO’S HYPOTHESIS
- equal volumes of different gases at the same temperature and pressure contain equal number of molecules. One mole of any gas comprises 6.022 x 1023 molecules and occupies 22.4 L at STP
AZEOTROPE
a mixture of two substances that cannot be separated by fractional distillation given each component shares same boiling point (the boiling point of each is altered by the presence of the other). eg mixture of ether and halothane in the ratio of 1:2
BASAL METABOLIC RATE
- energy liberated by catabolism of food per unit time determined by measurement of heat produced by subject: I. in morning II. fasted III. resting supine IV. at normal body temp V. in thermic comfort
BASE EXCESS
- blood sample equilibrated to PaCO2
40mmHg is titrated with acid or base until the pH is normal (is negative in acidosis).
BECQUEREL
one becqueral is the amount of radioactivity produced when one nucleus disintegrates per second
BERNOULLI EFFECT
- lateral pressure in a tube decreases as fluid accelerates through a constriction given increased propagating kinetic energy. The total pressure in a cylinder or tube conducting fluid equals the lateral pressure plus the kinetic energy of its forward velocity.
BICARBONATE ACTUAL
- true [HCO3-] in whole blood calculated by blood gas analyser by substituting pH and pCO2 into Henderson-Hasselbalch equation.
BICARBONATE STANDARD
- [HCO3-] in whole blood equilibrated at 37ºC with plasma PCO2 40mmHg reflects acid/base status of plasma if lung function is normal.
BIMETALLIC STRIP
- two dissolver metals arranged in a coil with different coefficients of expansion.
Binomical distribution
distribution in which there are two possible outcomes for each measurement.
BIOTRANSFORMATION
enzymic conversion of a drug in general to a more polar and less lipid soluble molecule.
BELL-MAGENDIE LAW
in the spinal cord the dorsal roots are sensory and the ventral roots motor.
BOURDON GAUG
- coiled type of metal where rises in temp pressure cause tube to uncoil.
BREATHING
- the alternate inspiration and expiration of air into and out of the lungs.
BTPS
Body Temperature Pressure Saturated
(310K, Pb, P H2O 47mmHg)
BUFFER BASE
- sum of all buffer anions in the blood including deoxyHb, HCO3- and intracellular/extracellular proteins and phosphates, normally totaling 44 -48mmol L¯¹.
BULK FLOW
- net solvent movement in one direction.
BUNSEN SOLUBILITY COEFFICIENT
- the volume of gas dissolved in a unit volume of solvent at a stated temperature and one atmosphere of pressure.
CALIBRATION
(1) Zero point
(2) Linearity
(3) Gain
CALORIE
- heat energy necessary to raise the temp of 1g of H2O by 1°C from 15 to 16°C
CATHODE
negative electrode of galvanic battery to which cations migrate and are reduced and into which electrons are fed from their source.
CENTRAL LIMIT THEORY
- even when a variable is not normally distributed the sample mean will tend to be normally distributed
CENTRAL TENDENCY
- describes centre of normal distribution, with the terms mode, mean, and median.
CHARLES LAW
- for a given mass of gas at a constant pressure, volume is directly proportional to absolute temperature.
CHELATE
- to incorporate a metal into an organic complex whereby a metallic ion is sequestered and firmly bound into a ring within the chelating molecule.
CHEMICAL EQUIVALENT
weight of a substance that will combine with or replace 8 grams of oxygen (replaced by mole).
CHIRAL
not superimposable on its mirror image, hence a centre for mirror image isomerism.
CLOSING CAPACITY
the lung volume at which dependent airways begin to close during expiration.
COLLOID
substance unable to pass through a semipermeable membrane, or substance present in solution in the colloidal state.
COLLOIDAL STATE
a system of particles in suspension rather than being in true solution due to the larger size of the particles.
COMPLIANCE
change in volume per unit change in pressure.
CORONARY PERFUSION PRESSURE
= diastolic BP - LVEDP
CORRELATION
describes the strength of association between variables, expressed as the Pearson correlation coefficient (r). An r of +1or -1 indicates complete positive or negative association, and r = 0 indicates no association.
Cross match
- serum of patient’s blood is mixed with each donor unit to ascertain if agglutination is present.
CURRENT
1 Ampere = movement of 6.24 x 10 18 electrons(e-) per second past some point.
-Direct current: steady flow of e- in one direction only.
-Alternating current: Root Mean Square (RMS) - take mean of squared AC voltage then take square root of this
RMS AC = equivalent AC
DAMPING
- Under: overshoot common - the system oscillates prior to
stabilizing. - Over: slow signal response with inability to respond to rapid
change. - Critical: point at which overshoot is just avoided.
- Optimal: 64% of critical damping => minimal overshoot (6-7%)
with only slight reduction in speed of response => compromise
between speed and accuracy
DATA
- results for analysis
- Nominal: qualitative value eg gender
- Ordinal: relative value between points eg ASA
- Ratio: continuous data including zero value eg mmol/L, Kelvin
- Interval: continuous data with no absolute zero ie where zero is
arbitrary point eg temp in Celcius
DEGREES OF FREEDOM
- number of observations in a sample that can vary independently of other observations.
DESENSITIZATION
- same as tolerance
- Homologous - responsiveness lost to agonists of same class only.
- Heterologous- Loss of responsiveness to a whole range of stimuli.
DEXTRANS
- any of a range of glucose polymers of varying sizes formed during the hydrolysis of sucrose.
DEXTROSE
D-Glucose
DIBUCAINE NUMBER
- % inhibition of plasma cholinesterase activity after addition of 10 -5 M solution of dibucaine (cinchocaine)
DIFFUSION
movement of substances down an activity gradient for that substance.
DOPPLER EFFECT
alteration in frequency of signal when source moves in relation to observer. Hence, waves reflected from moving substance will be picked up as lower in frequency (and pitch) when substance moves away and higher when substance approaches detector.
DOUBLE BOHR EFFECT
fetus unloads CO2 and H+ to maternal blood at placenta so that maternal oxyHb curve shifts to right causing decreased O2 affinity => unloads O2 to fetus. Concurrently, fetal blood CO2 and H+ decrease, shifting fetal oxyHb to left causing increased affinity for O2.
DOUBLE BURST STIMULATION
- two short bursts of tetanus (2-4 pulses at 50 Hz) separated by 0.75sec. The tetanus bursts fatigue the NMJ more than two single twitches.
DOWN REGULATION
- reduction in receptor number which usually occurs with chronic exposure to an agonist. It is associated with reduced sensitivity to the agonist and increased sensitivity to the antagonist.
DRUG ABUSE
persistent or sporadic excessive use inconsistent with or unrelated to acceptable medical practice.
DRUG DEPENDANCE
- a state psychic or sometimes physical resulting from the interaction between a living organism and a drug, characterized by behavioural and other responses that always include a compulsion to take the drug on a continuous or periodic basis in order to experience its psychic effects, and sometimes to avoid the discomfort of its absence.
DYNE
- force needed to accelerate 1g by 1cm per sec per sec Dyne/cm² = 0.1 Pa.
ECG
Graphic recording of the changes occurring in the electrical potential (in mV) between different sites on the skin as a result of cardiac activity.
ELECTICAL EQUIVALENT:
= gram molecular weight/valance
Entrainment ratio
entrained flow/driving flow
Enzyme
biologial catalyst
Force
mass x acceleration (unit is Newton)
FOURIER ANALYSIS
any complex waveform can be constructed from multiple sine waves of different frequencies. The slowest component is the fundamental frequency, and higher frequency multiples of the fundamental frequency are termed harmonics.
FREE RADICAL
extremely reactive radical which carries an unpaired election (where radical is fundamental constituent of molecule).
F-TEST
a test to compare two variances to see if two samples represent the same population (divide larger variance by smaller and refer to F tables)
FUNCTIONAL PLASTICITY
implies dynamic alterations in response of neurons can occur.
Functional SaO2
HbO2x100 / [HbO2 + Hb]
GAIN STABILITY
gain is the ratio of output to input signal amplitude; the degree of signal gains should be the same and should remain constant over time.
GALVANOMETER
- measures current, usually by deflection of wire in a magnetic field.
GIBBS-DONNAN EFFECT
- in the presence of a non-diffusible ion, the diffusible ions distribute themselves so that at equilibrium their concentration ratios are equal.
GOLD STANDARD
- the standard by which new tests are compared, thought to generally have high accuracy (sensitivity and specificity).
GLYCOL
alcohol compounds with two or more hydroxyl (OH) groups.
HAPTEN
- small molecule that assists in immunological response but cannot produce response on its own.
HEAD’S PARADOXICAL REFLEX
- lung inflation produces a paradoxical further increase in inspiration.
HEAT CAPACITY
The amount of heat required to raise the temperature of a given object by 1 Kelvin. Specific heat capacity is the amount of heat required to raise the temperature of 1kg of a substance by 1 Kelvin.
HETEROMETRIC AUTOREGULATION
improved ventricular function that is dependant upon changes in myocardial fibre length.
HOMEOMETRIC AUTOREGULATION
compensatory mechanisms that result in improved ventricular performance independent of changes in myocardial fibre length.
HYPOTHALAMUS
the portion of the diencephalon (posterior forebrain) lying beneath the thalamus and forming the floor of the third ventricle. Concerned with:
- neuroendocrine, control of pituitary hormone sectretion
- Autonomic NS control
- thermoregulation
- control of motion, thirst
HYSTERESIS
value of one phenomena depends on whether another has been rising or falling eg transpulmonary pressure required to hold constant lung volume after expiration vs inspiration.
IDEAL GAS LAW
- an ideal gas is one which has negligible intermolecular attraction and the molecular volume is small in comparison to the space between molecules.
PV = nRT
INTRINSIC ACTIVITY
analogous to efficacy.
IMPEDENCE
resistance to a pulsatile/alternating flow/current.
INTRAOCULAR PRESSURE
pressure of aqueous humour. Normal is 12-20mmHg and it is raised by:
- increased choroidal blood volume/flow
- aqueous humour production/ absorption
- Intraocular mass/bleeding/hypoxemia
- CVP, transient ABP changes
- Extravascular muscle tone
- Direct external pressure
ISOTOPE
different form of same element.
JOULE
Work done when a force of one neutron moves its point of application one metre in the direction of the force.
KIDNEY FUNCTION:
- H20 and electrolyte balance/regulation
- Acid-base balance
- Removal waste and foreign chemicals
- Metabolism
- BP regulation
- Erythropoetin/Vitamin D activation
- Gluconeogenesis
KRUSKALL WALLIS
non-parametric equivalent of ANOVA
LIVER FUNCTIONS:
- Storage - Glycogen, fat, Cu/Fe, vitamins
- Bile production and disposal
- Metabolism - fat, CHO, proteins (including enzymes), hormones
- Detoxification
- Immunity
LUNG FUNCTIONS:
- Gas/respiration exchange
- Filtration
- Metabolism and deactivation (eg angiotensin, 5HT)
- Storage
- Surfactant
- Immunity
MANOMETER
device to measure pressure of a gas.
METABOLISM
literally means change, referring to all types of chemical and energy transformations that occur in the body.
- Catabolism: breakdown
- Anabolism: formation
MOLALITY
number of moles of solute per kg of solvent.
MOLARITY
number of moles of solute per litre of solution.
Dependant on temperature, density of solvent, and volume of solute.
MOLE
molecular weight of a substance in grams.
MOTOR UNIT
consists of anterior horn cell, motor axon, and muscle fibres supplied by it.
MULLER MANOUVRE
strong inspiratory effort against a closed glottis.
MUSCLE SPINDLE
- intrafusal muscle fibres (~10 in capsule) which are concerned with proprioception.
NATURAL FREQUENCY
- frequency at which a system resonates or oscillates at a greater amplitude than seen above or below this frequency.
NEGATIVE PREDICATIVE VALUE
likelihood of avoiding an outcome, equal to proportion of true negatives (TN) given a negative test result: TN/ (TN + FN). Depends on prevalence.
NEUROLEPTICS
- inhibit the following via Dopamine receptor blockade:
- learned conditioned behaviour
- amphetamine induced arousal
- opioid induced vomiting
NEUROMUSCULAR BLOCKADE:
Non-depolarizing / Competitive
- no fasciculation
- fade (T4/T1 0.7 (no fade)
- no post tetanic facilitation
- Phase II Block / Partial Non-Depolarizing: repeated doses of depolarizing relaxant can produce similar characteristics to non-depolarizing block, but this occurs via different mechanism and is difficult to reverse with neostigmine.
NOCICEPTION
the phase which initiates human pain experiences; the detection of tissue damage by receptors in the body and the transmission of this input to the CNS.
NON PARAMETERIC METHODS
used when data is not normally distributed eg nominal or ordinal data.
NORMALITY
- the number of chemical gram equivalents of solute per litre of solution.
OHM
the resistance which will allow one ampere of current to flow under the influence of a potential of one volt.
OHM’S LAW
V = IR
OVERTON-MEYER THEORY
olatile agents with the highest oil solubility are found to have the greatest potency as anaesthetics.
PARAMETER
a measurement which characterizes/summarizes population data distribution and hence defines a population. Uses Greek letters (c.f. statistics which uses Roman letters)
PERIPHERAL NERVE STIMULATOR (IDEAL)
- waveform: unpolar square 0.2 - 0.3msec
- current: supramaximal 20-60mA into 2.5 k Ω
- adjustable
- maintained with changing Ω
- positive electrode proximal
- stimulus: - T.O.F (2 Hz)
- single batch 1.0 Hz
- tetanus 50 Hz, 3-5sec (painful in awake patient)
- double burst, 2 short titanic 50 Hz for 60msec
POST TETANIC COUNT
- number of responses to 1 Hz stimulation for 3 seconds after 5 sec of 50 Hz tetanus.
- PTC 8-10 = first TOP
- PTC 0 = no buck or cough
- fade = NDR (c.f. DR)
Power (electrical)
Work/Unit time (unit = W, watt)
PRESSURE
force per unit area (unit = Pa.)
PSEUDO-CRITICAL TEMPERATURE -
temperature at which a gas mixture will separate out into its constituent components.
RAOULTS LAW
- an empirical result which describes the lowering of the vapour pressure of a solvent by the presence of a solute. Solute molecules reduce the concentration of solvent molecules in the liquid phase and hence reduce the number of solvent molecules which leave the liquid phase per unit time. If solvent and solute are chemically similar, Raoults law accurately describes the reduction in vapour pressure.
RECOVERY
Reversal of anaesthetized state to consious state including reversal of induction and recovery of neuromuscular function.
REDUCTION
- removal of O2 or gain of e-
REFLEX
basic unit of integrated neural activity or the sum total of any particular automatic response mediated by the nervous system.
REGRESSION
mathematically describes relationship between two variables and hence allows prediction of one variable given another.
RESPIRATORY EXCHANGE RATIO
estimation of Respiratory Quotient, derived from ratio of expired CO2 to inspired O2. Depends on ventilation and not necessarily at steady state.
RESPIRATORY QUOTIENT
the ratio in the steady state of the volume of CO2 produced to the volume of O2 consumed per unit time (1 for CHO, 0.7 for fat, 0.82 for protein).
Reynolds number
Re = rvd/n
Flow of fluid with velocity v, viscosity n, and density d through tube of radius r, becomes turbulent at ~Re > 2000
RHEOLOGY
The science dealing with the flow and deformation of matter.
SARCOMORE
the contractile unit of a myofibril delineated by Z bands.
SENSITIVITY
- the proportion of true positives that are correctly identified.
= TP/ (TP + FN)
SOLUTE
a substance dissolved in a solvent to form a solution.
SOLUTION
a homogenous molecular mixture of two or more substances of dissimilar molecular structure. Usually refers to solids in liquids.
SOLVENT
a substance (usually a liquid) having the power to dissolve other substances in it.
SOLVENT DRAG
solvent, moving by bulk flow, tends to drag along some molecules of solute.
Specific compliance
= lung compliance/lung volume
SPECIFICITY
the proportion of true negatives that are correctly identified.
= TN/(TN + FP)
STARCH
any of a group of polysaccharides of the general formula (C6 H10 O5)n
STARLINGS LAW OF THE HEART
the force of contraction is dependant on the end-diastolic muscle fibre length; the heart pumps whatever blood is returned to it.
STATISTICS
rganisation and mathematical manipulation of data. Defines a sample.
- Descriptive: describes the characteristics studied .
- Inferential: used to make decisions.
STAVERMAN REFLECTION COEFFICIENT
a measure of how impermeable the capillary is to proteins eg l = completely impermeable.
STPD
standard temperature pressure density
(273K, 1 atm, PH2O = 0)
STROKE VOLUME
LVED - LVESV
SUPRAMAXIMAL STIMULUS
the point where the force of contraction fails to increase rapidly despite an increase in delivered current (~ 2.75 x initial threshold)
SURFACTANT
urface active mixture of phospolipids (P I, D L, S) secreted by alveolar type II cells to decrease surface tension of pulmonary fluids and thus contribute to elastic properties of lung.
SYNERGISM
mplies two drugs interact to produce an effect greater than the additional effect.
SYSTEME INTERNATIONALE-
s Sec M,m Mol, metre A Ampere C Candela K,k Kelvin, Kilogram
TONOMETER
measures pressure of a liquid.
TOTAL LUNG CAPACITY
maximum volume that the lungs can contain.
TRAIN OF FOUR
4 pulses of supramaximal stimulus at 2.0 Hz.
TRANSDUCER
a device which changes a signal from one energy form to another. The ability of a transducer to respond to a change in the signal depends on
- frequency of the signal
- natural undamped frequency
- degree of damping
THERAPEUTIC INDEX:
Toxic dose SD/therapeutic dose SD
UP REGULATION
- increased receptor number (and reponse) which usually occurs with chronic exposure to the antagonist. Associated with increased sensitivity to the agonist but resistance to the antagonist.
VALSALVA MANOUVRE
forced expiration against a closed glottis.
VENOUS ADMIXTURE
theoretical amount of mixed venous blood needed to add to pulmonary capillary blood to create arterial gas tensions (ie O2).
VENTILATION
the process of exchange of air between the lungs and ambient air.
- Total: total volume leaving lung each minute.
- Alveolar: effective ventilation of the alveoli, where gas exchange with the blood takes place.
VITAMIN
an organic substance found in foods and essential in small quantities for growth, health , and preservation of life.
VOLT
the potential difference which produces a current of one ampere in a substance when the rate of energy dissipation is one volt.
VOMITING
forceful expulsion of gastric contents via the mouth.
WHEATSTONE BRIDGE
set of four resistors in series, an electrical source and a galvanometer, with one of the resistors often used as part of a strain guege or resistance thermometer.
WIND UP
Hyperexcitable state of pain transmission that may lead to pain memory establishment.
WORK
Force x distance or pressure x volume (unit= Joule)
WINDKESSEL EFFECT
hydraulic filtering which converts the intermittent output of the heart to a steady flow through the capillaries.
X-RAYS
- electromagnetic radiation produced when a beam of electrons is accelerated from a cathode to strike an anode (usually tungsten).
ZERO STABILITY
ability to maintain zero.
*EUTECTIC
mixture in which the melting point is lower than each individual constituent.
- LINDQUIST EFFECT-
Describes axial streaming of RBC in vessel
*LYOPMILISOD-
Creation of a stable preparation of a biologic substance by rapid freezing and dehydration under high vacuum.
*SEBBECK EFFECT
At any junction of two dissimilar metals, a small voltage is produced, the magnitude of which depends on the temperature of the junction.
Osmosis
Diffusion of a solvent down it’s concentration gradient across a semi permeable membrane
Absolute pressure
Gauge pressure + atmospheric pressure
Third perfect gas law
At constant volume, the absolute pressure of a given mass of gas varies directly with absolute temperature.
Tare weight
Of a cylinder is the weight when empty.
Specific latent heat
The heat required to convert 1kg of a substance from one phase to another at a given temperature.
Gauge Pressure
Measures pressure relative to ambient pressure, being the pressure above ambient pressure. Equals absolute pressure minus ambient pressure.
Micelle
Spherical aggregates of lipid molecule surrounded by bile salts rendering them water soluble.
Von Willebrand’s factor
Large plasma protein synthesized by endothelial cells & megakaryocytes which functions as an adhesive protein to bind platelets to each other & damaged endothelium.
ED95 NMBD
The dose of a neuromuscular drug required to produce 95% depression of a single twitch response at adductor pollicis under N20-barbiturate-opioid anaesthetic.
NMDA receptor
Multi-unit transmembrane protein forming an ligand gated cation channel, requiring partial membrane depolarization to release a magnesium ion ‘plug’ and the presence of glycine before it can be activated by glutamate and produce an EPSP.
Optical isomers
Have a chiral centre, Can be distinguished by the rotation of polarized light (dextro & laevo, d & l) absolute configurations (R & S)
Diastereoisomers
Have more that one chiral centre, and multiple possible stereoisomers; not all mirror images so cannot be called enantoimers.
Tautomerism
Refers to the dynamic interchange between two forms of a molecular structure, often precipitated by a change in the physical environment. Eg, midazolam.
Spare receptors
A maximal tissue response is produced receptor occupancy is less than 100%.
EC50
Measure of potency. The dose that will cause a response that is 50% of the maximum.
quantal dose-response curves
Used when the effect being measured is an all or none phenomenon - presence or absence of a response is plotted for a population. ED50, TD50, LD50.
Therapeutic window
Is the dose range between the minimum therapeutic concentration and maximum toxic concentration.
Shunt
Refers to blood which enters the arterial system without passing through the ventilated areas of the lung.
Anatomical dead space
Volume of the conducting airways.
2.2ml/kg or 150ml for 70kg adult. Measured by Fowler’s method.
Physiological dead space
Part of the tidal volume that does not participate in gas exchange. Equal to anatomical plus alveolar dead space and is measured by the Bohr equation.
Alveolar dead space
Part of the inspired gas which passes through the conducting airways to mix with gas at the alveolar level but does not participate in gas exchange.
Haemoglobin
Metalloprotein consisting of four globin chains each with it’s own haem group. The haem contains iron in it’s ferrous form (Fe2+), which forms loose reversible bond with O2.
Interthreshold range
Is the range of core temperature over which no autonomic thermoregulatory response occurs.
Malignant Hyperthermia [hyperpyrexia]
is an inherited (pharmacogenetic)
disorder of skeletal muscle, characterised by a hypermetabolic state, triggered
by all volatile anaesthetics and sux.
zero order kinetics
a constant amount of drug is eliminated per unit time. Occurs with high dosage phenytoin, salicylates, theophylline, and thiopentone (v. large doses).
Acute porphyria
Rare genetic diseases caused by errors in the pathway of haem biosynthesis resulting in the toxic accumulation of porphobilinogen and porphyrin precursors.
CPP
Cerebral Perfusion pressure is the driving pressure of blood flow through the brain. Equal to MAP mminus greater of ICP or cerebral venous pressure.
