1week before Flashcards
tripple point of water
STP
triple point: 273.16 K – 0.01°C, 611.2 Pa (0.06atm)
STP : 273.15K (0°C), 101.3 kPa (760 mmHg)
what is a resistance wire, thermocouple, thermistor?
resistance wire - metal. linear graph, positive gradient (temp =x , resistance =y). very accurate, slow response, fragile
thermistor = metal oxide. non linear - negative expontial graph (can be positive). cheap, fast, small. calibration error, deteriorates overtime.
thermocouple = temp vs potential difference. seebeck effect. very small, cheap, tough. needs amplificationw
where are thermistors found
Used in PA catheter and oesophageal stethoscope
which temperatures is mercury and alcohol liquid expansion thermometers suitable for?
Mercury is more suitable for high temperatures, between -39°C and 250°C (alcohol boils at 78.5°C)
Alcohol is more suitable for low temperatures, between -117°C and 78°C (mercury solidifies at -39)
how do infrared thermometers work?
pyoelectric sensor and thermopile
detect infrared radiation
how do chemical thermometers worK?
liquid crystals
change colour with temp
what can affect accuracy of bladder and rectal temp?
bladder - flow rates
rectal - few degrees higher due to bacterial fermentation
which temp sensor is best for hypothalamic?
tympanic
when should a forced air warmer and fluid warmer be used?
forced air warmer surgery >30mins
IV fluid warmer - fluids >500ml
what does hypothermia do to MAC?
drop
% of different forms of heat loss
40-50% of heat loss is via radiation, 30% by convection, 20% by evaporation and 3% by conduction.
what is found in a dial thermometer that is responsible for detecting temp change?
bimettalic strip
define relative humidity
Absolute humidity/the SVP of water at that temp, or,
The ratio of the mass of water vapour in a given volume of air compared with the mass that would be required to saturate that given volume of air at the same temp.
what is due point?
temp at which relative humidity exceeds 100% and water condenses out
what is hygroscopic material?
Material that attracts moisture from the atmosphere
how does a wet and dry bulb hygrometer work?
2 thermometers
one reads ambient temp.
one sits in a container of water which cools as water evaporates due to loss of heat of vapourisation
rate of evaporation varies with humidity of surrounding
difference between 2 = relative humidity
requires good air movement to be accurate
how does the regnaults hygrometer work?
silver tube containing ether
air bubbled through to cool it
when condensation occurs on the tube (dew point) this will be the temp at which ambient air is fully saturated
use table for comparison
more accurate the wet and dry bulb and hair hygrometer
methods to measure humidity?
hair hygrometer
wet and dry bulb
regnaults
mass spec
UV light absorption
transducers
what does regnaults hygrometer measure?
relative humidity
at what humidities is hair hygrometers most accurate
between relative humidity 30-90%
what are Pitot tubes in measurement?
improve accuracy of pneumatochograph
how does efficiency of HME vary with volume?
more efficient at lower TV
what principle do gas driven nebulisers rely on?
bernoulli / venturi
what does clonidine do to gastric motility? and cerebral blood flow
drops both
what ion is a cofactor for adenylate cyclase?
Mg
how do cAMP and cGMP lead to smooth muscle dilation?
cAMP –> PKA
cGMP –> PKG
MLCK = normally phosphorylates myosin for muscle contraction.
PKA - inhibits MLCK
PKG - promotes MLC phosphatase
cGMP also reduces Ca into cell
name 3 a2 agonists
clonidine,
methyldopa
dexmedetomidine - more selective
how is methyldopa normally given?
oral
rarely IV
what does clonidine do to hormones?
inhibits ADH
inhibits insulin release
which antihypertensives act as ganglionic blocking agents
rarely used
Trimetaphan
block nACHr at ganglia of ANS
less sympathetic output and vasodilation
what is Guanethidine ?
adrenergic blocking agent
(can be used for chronic pain)
this is uptaken by adrenergic neurons and blocks release of NA
how does hydralazine work?
arteriole dilator
acts via cGMP / guanyl cyclase pathway
what is the effect of hydralazine affected by?
acetylator activity
variable BO
what vessels do nitrates work on?
low doses - veins
high doses - arterioles
how does sodium nitroprusside work?
arteriolar and venous dilator
rapid on and offset
how does magnesium cause vasodilation?
co-factor for adenylate cyclase - more PKA , more MLCK inactivated
blocks catecholamine receptors
blocks L type Ca channels
how do Ca channel blockers work?
L type Ca channels
vasodilation
reduced contractility
reduced propagation of cardiac depolarization
what are the subgroups of Ca channel blockers?
Phenylalkylamines – Verapamil - antiarrhythmics
Dihydropyridines – Nifedipine, Amlodipine - arteriolar vasodilation
Benzothiazepines – Diltiazem - both cardiac and peripheral
which ACEi is a prodrug? which is secreted unchanged?
lisinopril - excreted unchanged
prodrug - ramipril, enalopril
guidelines for antiHTN management primary care
<55 years:
1st line: ACEI or Angiotensin II inhibitor
2nd line: Calcium channel blocker or Thiazide diuretic
> 55 years or black:
1st line: Calcium channel blocker or Thiazide diuretic
2nd line: ACEI or Angiotensin II inhibitor
what antiHTN used in preganncy ?
oral methyldopa, labetalol, nifedipine
if severe IV labetolol/ Mg/ hydralazine
side effects of clonidine
dry mouth, sedation, depression, reduced gastric motility and reduced cerebral perfusion
hypotension
rebound hypertension
how does sodium nitroprusside effect shunt?
It can increase shunt by impairing hypoxic pulmonary vasoconstriction.
how many cyanide ions does sodium nitroprusside make?
5
how does nifedipine affect MAC?
CaCB acting on arterioles - can reduce MAC
what is the anion gap in CKD like?
normal
how does low albumin affect the anion gap?
reduces it
unmeasured anion
where is HCO3 mostly reabsorbed?
PCT
which part of kidney determines final urine pH?
distal convoluted tubule
how does affinity for O2 compare in COHb and MetHb
increased in COhb
less in metHb - unable to bind O2
how much more soluble is CO2 than O2
x25
what is the CO2 content of venous blood?
500ml/L
how does O2 consumption, MV, CO and oxygen extraction change in vigorous exercise?
Maximum O2 consumption = 10 fold
cardiac output of 5 times,
minute ventilation 10 times
doubling of the oxygen extraction ratio to 0.5.
how does O2 dissociation curve shift in stored blood?
to the left
less 2,3 DPG
what is the minimum storage capacity for VIE oxygen?
14 days
how many more times its volume does liquid O2 in VIE provide O2 gas?
842x
what is the pressure inside VIE?
10.5 Bar / 1000kpa
what are modern gas cylinders made of?
Molybdenum steel,
high-carbon manganese steel
light-weigh steel aluminium composite.
what are pipelines for gases made of?
copper
what is the presure in pipeline for medical air?
It is 4 Bar for Medical Air and 7 Bar fo Surgical Air
what flow rate is required for suction?
25L/min
how much pressure should suctioning be able to generate?
more than 500 mmHg in 10 seconds
how is the resistance and compliance of suction tubing?
low resistance
low compliance - prevents colapsing of tubing
in a plenum vapouriser is the output dependant/independant on gas flow?
dependant - as it is only calibrated from 0.5-15L/min flow
how much CO2 does 1Kg soda lime absorb?
250 litres of CO2
standard size reservoir bag ?
2 L
what pressure do reservoir bags limit the system to?
40 cmH20
what part of cylinders are colour coded?
shoulder
not bodies
what pressure does the blow off valve of a VIE open?
1500kpa
is soda lime always essential in circle system?
no
can use high flows instead
should you disconnect a vapouriser before filling it up?
no
how is oxygen failure alarm checked?
disconnection of the oxygen hose
checked weekly
as part of AABGI anaesthetic machine check, does scavenging system need checking?
yes
how do inhalation agents affect NMBA?
potentiate action
because have effects to reduce muscle tone - reduce NT release at NMJ
what is the blood gas partition coeficient of xenon? how does this compare to N20 and desflurane?
xenon = 0.14
N20 = 0.47
des = 0.42
what happens to metabolism of atracurium in hypothermia?
reduced
how much plasma protein binding of atracurium?
15%
describe alcohol metabolism…
Alcohol is metabolised in cytoplasm by alcohol dehydrogenase to acetaldehyde, then by acetaldehyde dehydrogenase to acetate.
why does alcohol cause ataxia in acute intoxication
cerebellar toxin
what gives hangover effect of diazepam?
active metabolite - tenazepam
tenazepam has 8 hours half life.
removed via glucuronidation
what do class 1b drugs do to AVN conduction? e.g. phenytoin
enhance
elimination half life of digoxin?
35 hours, which is increased by renal impairment
excretion of digoxin?
Less than 10% undergoes metabolism in the liver. Digoxin is excreted primarily unchanged via the kidney by glomerular filtration and tubular secretion, hence the necessity for dose adjustment in renal impairment.
which receptors does dobutamine mainly act on
agonist
B1
in null deflection O2 paramagnetic analyser, what opposes the dumb bells?
opposing magnetic field
what does PEEP do to deadspace?
increases it
wavelength of O2 in pulse ox
oxy - 940
deoxy 660
in terms of korakoff sounds, how does systolic BP relate to them?
Systolic pressure corresponds to the onset of Korotkoff sounds, not the loudest sound
how is CO calculated via Ficks principle?
dividing oxygen consumption, in ml per minute (250 normally) by A-V oxygen difference, in ml per litre of blood (5ml.100mL-1 or 50ml.L-1 normally).
d/dt VO2 = (CaO2 - CvO2). Q
d/dt VO2 = uptake
Q= CO
what increases damping in arterial system?
bubbles,
poor functioning flushing system
very long tubing
less compliant tubing
many connections.
what direction is the T wave in aVR?
negative deflection
which lead is a Q wave normal in ?
V 6
whats the equation for energy/ work and pressure and volume ?
energy/work = pressure x volume
what is the equation for power, force and velocity?
power = force x velocity
does Vd depend on lipid solubility only?
no
also can depend on metabolism e.g. remifent is very lipid soluble but low Vd because rapid metabolism.
why is propofols Vd so large?
v lipid soluble
mostly unionised at physiological pH
metabolites of atracurium?
laudanosine
monoquarternary alcohol derivative
CYP enzymes with genetic variability?
2D6
2C9 - warfarin
how does rate of elimination related to clearance?
rate of elimination = clearance multiplied by plasma drug concentration
type of curve for wash in
described as negative exponential
1- Ae-kt
how is oral bioavailability calculated?
AUC(oral)/AUC(IV)
Vd for atropine - small or big?
big
v lipid soluble
what is the problem with using filters in ecg to reduce noise?
can also reduce signals in ecg that can be used for diagnosis
what frequency does diathermy work in?
1-5MHz
how does coagulation mode and cutting mode in diathermy differ?
Coagulation mode uses short burst sine waves and cutting mode uses continuous sine waves.
equation for energy in electricity
I^2 x R
or
V^2/ R
reynaulds number calculation…
Re = density x velocity x diameter/viscosity
what type of receptor is a2?
Gi
inhibits NA release - vasodilation of arterioles
also causes smooth muscle contraction of veins and coronary
platelet aggregation too
other than vasoconstiriction what does a1 receptors do?
glycogenolysis
increase insulin and glucacon
mydriasis
functions of B1, B2, B3
B1 - heart, renin, lipolyisis
B2 - lungs, glycogenolysis, insulin and glucagon release
B3 - lipolysis and thermogenesis
name the selective a1 antagonists…
uses..
Prazosin
doxazocin
terazosin
Used for essential hypertension, phaeochromocytoma and congestive cardiac failure.
also for BPH
non selective alpha 1 antagonists include..
Phentolamine - IV , given to block sympathetic driven HTN
Phenoxybenzamine - oral or IV, longer acting. makes covalent bonds with alpha receptors so long duration of action.
side effects of phentolamine
nasal congestion
bronchospasm from sulphite metabolites
hypoglycaemia due to insulin release
side effects of B blockers?
bronchospasm
poor peripheral perfusion
hallucinations, nightmares, depression
increased urine tone and retension
are B blockers used in heart failure?
sometimes
early stages NYHA 1 and 2
but not decompensated stage 4
when is labetolol and esmolol used?
labetolol = non cardioselective , reduces BP and HR. has alpha and beta affects
Esmolol cardioselective - only reduces HR. given as infusion. can cause bronchospasm sometimes
how does labetolols selective alter with route of administration
more selective to B receptors over alpha receptors when given IV
in pheochromocytoma, do alpha or beta blockers need to be given first and why?
alpha blocker
then B blocker
because if b blockers first it can worsen HTN by removing vasodilation from B receptors
what type of antagonism does phenoxybenzamine have?
Phenoxybenzamine is an irreversible α-adrenergic receptor antagonist
half life 24 hrs
treatment for bradycardia in ALS?
Atropine 500mcg
next
- atropine up to 3mg
- isophrenaline
- adrenaline
- pacing
is atropine racemic?
Yes (only L is active, D inactive)
can atropine cause bradycardia?
At low dose can initially produce bradycardia (Bezold-Jarisch reflex)
2 unusual side effects of atropine
local anaesthetic properties
reduces ADH release
does glycopyrolate cross placenta?
yes
but not BBB
what is more potent at reducing secretions glycopyrolate or atropine?
glycopyrolate
how does isophrenaline work?
B1 and B2 agonist
is atropine given in PEA arrest?
no
what effects on heart does amiodarone have?
blocks K+ channels
slows repolarisation
increases refractory
prolongs phase 3
slows AVN automaticity and conduction.
No effect on conduction through bundle of His and ventricles
is amiodarone protein bound?
yes high PB
can diplace digoxin, anticoags, CaCB and Bblockers
name a cardiac glycoside
digoxin
how is digoxin excreted?
mostly unchanged in urine
hence adjustments in renal failure
narrow therpeutic index
what increases risk of digoxin toxicity?
low K, low Mg
high Na, high Ca
hypoxia
amiodarone, verapamil, diltiazam
what drug class does flecanide belong too?
amide local anaesthetic
effects of digoxin toxicity
headache
abdo pain
convulsions
gynaecomastia
colour vision change
muscle weakness
heart block
which cytokine is anti inflammatory?
IL 10
what part of spinal needle stops wrong route of administration?
NRFit system
ywllow in colour
equation for heat generated by diathermy?
heat generated = current²/area.
gold standard for sterilisation?
steam via autoclave
4 parameters for autoclaving?
steam, pressure, temp, time
what antiemetics antagonise dopamine?
domperidone
droperidol
promethazine
chlorperizine
prochlorperizine
great toe extension myotome?
L5
at what level is the stellate ganglion blocked?
C6 - anterior tubercle
how long should the heparins and warfarin be stopped for before spinal?
Unfractionated heparin (IV) – 4 hours (check APTT).
LMWH (prophylactic dose) – 12 hours.
LMWH (treatment dose) – 24 hours.
Warfarin – INR < 1.5.
describe method of pasteurisation…
low temp steam
mechanism of azoles
inhibit formation of ergosterol
mechanism of polyenes
antifungal
bind ergosterol and create pores in membrane
amphotericin, nystatin
mechanism of echinocandins
inhibit B1 -3 glucan synthase
capsofungin etc
what is dobutamine an isomer of?
structural isomer of dihydrocodeine
what does sodium nitroprusside do to V:Q
reduces hypoxic vasoconstricition
worsens V:Q
can cause shunt
must use additional O2 to reduce this.
how is sodium nitroprusside metabolised?
hydrolysis in RBC to produce nitric acid, cyanide ions and methamoglobin
how does cyanide toxicity present?
hyperventilation
met acidosis
increased venous sats
what is a HMEF filter?
filters microbes as well as HME
equation for ventricular ejection fraction?
stroke volume/ end diastolic volume
name the parasympathetic ganglia in H&N…
ciliary, pterygopalatine, submandibular and otic.
what is the hepatic artery buffer response?
vasodilation of hepatic artery in response to reduced portal venous blood flow.
adenosine is secreted into the space of mall via O2 independant mechanism. reduced portal flow, less clearance of adenosine, builds up and causes vasodilation of hepatic artery.
describe tautomorism of midazolam?
pH <4 - open ring - water soluble
name structures…
A = fem nerve
B femoral canal
C= great saphenous vein
D = femoral sheath
causes of increased transfer factor and decreased?
increase = polycytheamia, alveolar haemorrhage
decrease = pulmonary fibrosis, P.E , emyphysema, pulmonary HTN
how does cisatracurium compare to atracurium in terms of potency and side effects?
less histamine release
more potent
which form of warfarin is more protein bound?
S warfarin
s is sticky
entonox is what ratio mixture?
50:50
by volume (not by weight)
what filter is used in cell salvage?
150 micro meters
what is represented by the area inside the hysteresis curve?
energy lost as heat
how are epidural catheters marked?
Epidural catheters have one single mark at the tip so that it may be identified on removal.
They have 5 single markings at 1 cm intervals from 5-9 cm,
a double marking at 10cm, 1cm intervals from 10-14cm,
a triple marking at 15cm and then quadruple markings at 20cm.
pka. PB and solubility of lidocaine, prilocaine and bupivacaine
Lidocaine has a pKa of 7.9, is 70% protein bound, and its relative lipid solubility is 150.
Prilocaine has a pKa of 7.7, is 55% protein bound, and its relative lipid solubility is 50.
Bupivacaine has pKa of 8.1, is 95% protein bound, and its relative lipid solubility is 1000.
normal urine output per hour
30-80ml/hr
how often is a diabetics BMs monitored intra op
1 hourly
mechanism of hyoscine?
Both hyoscine and atropine primarily work by antagonising muscarinic receptors at the chemoreceptor trigger zone.
describe the bundles in fibre optic endoscope?
It consists of two main bundles of optical fibres, a coherent bundle (to transmit image) and a non-coherent/illumination bundle (to transmit light), and a working channel surrounded by a flexible steel braid, angulation wires and a protective sheath.
Whilst the coherent channel consists of 10’000 individual fibres of diameter 10 μm, it constitutes only a very small portion of the diameter of a flexible fibre optic endoscope. The size of the working channel is the major determinant of size.
how often is a fuel cell calibrated?
daily
2 points - 21% and 100%
how does methylene blue work? some ADRs
nhibiting nitric oxide induced cGMP activity
causes pulmonary vasoconstriction
methamoglobinaemia
sats 85% (falsely)
what is the british standard for level of performance of a filter?
The British Standard is N95. At this level of performance, less than 5% of particles pass through the filter.
