Previous TF Q from book Flashcards
how many stereoisomers of atracurium?
10
how many more times potent is cisatracurium than atracurium?
3-4 x more potent
how is cisatracurium metabolised?
hofman degradation to laudanosine and monoquartenary acrylate
then hydrolysed by non specific plasma esterases to monoquart alcohol and acrylic acid
i.e. plasma esterase metabolism IS INDIRECT
does cisatracurium have any active metabolites?
none
is atracurium or cis-atracurium dependant on renal function for its clearance?
both are INDEPENDANT
what is the elimination half life for propofol?
5 to 12 hours
which part of propofol undergoes glucuronidation?
hydroxyl group in position 1
how does propofol exert its antiemetic effects?
via D2 antagonism
Is potency of local anaesthetics related to lipid solubility?
yes
which is more potent ropivacaine or lidocaine?
ropivacaine x4
how much protein binding does cocaine have? what about other ester LA?
all ester LA are highly protein bound
cocaine = 95%
which block will acetylcholinesterase inhibitors potentially potentiate?
phase 1 block by depolarising agents
more Ach in cleft - can potentiate depolarising effects of sux.
does sux cause post tetanic potentiation?
no
feature of non-depolarising blocks
OR phase 2
what are the ADRs of heparin?
thrombocytopenia
hyperkalaemia (inhibits aldosterone)
hypersensitivity
osteoporosis
can heparin cross placenta?
No - low lipid solubilty
doesnt have any fetal side effects
how does 2g/kg mannitol given IV affect serum osmolarity , sodium and volume of blood
increases osmolarity (it is an osmole itself)
water follows - drop in cellular osmolarity
hence sodium conc drops
volume increases
what does acetazolamide do to urinary pH?
inhibits CA
hence less excretion of H+
HCO3 not absorbed
alkaline urine
which drug potentiates aminoglycoside ototoxicity?
furosemide
which drugs can potentiate warfarin?
DAPETS
Doxycycline
Aspirin . Antifungals , Amiodarone
Propanol
erythromycin
tamoxifen
SSRIs
how does rifampicin effect warfarin?
inducer
reduces effects of warfarin
what is ketamine a derivative of?
phencyclidine
how does ketamine have a positive iono/chronotropic effect?
INDIRECTLY
activation of sympathetic NS
what is more potent etomidate or propofol?
etomidate 10x more potent
what pH is the propofol emulsion?
7
what is the extraction ratio of thiopentone compared to propofol
high - propofol
low - thio
hence thio more effected by protein binding, clearance of propofol more effected by liver blood flow
which benzos have active metabolites?
midazolam
diazepam
not lorazepam
benzos can cause impaired motor coordination and ataxia - T or F
T
can benzos reduce Chloride plasma conc?
no
the opening of channels hyperpolarises cell but wont lower plasma conc
can midazolam be given rectally and intranasally?
yes
how does aminophylline work?
phosphodiesterase inhibitor
at pH 7.4 what level of unionised alfentanil exists?
90%
how does the clearance of alfentanil and morphine compare and the half life?
morphine quicker clearance
however alfentanil has a shorter half life due to its smaller Vd
how does Vd of alfentanil and fentanyl compare?
alfentanul smaller - hence short half life.
what is the most protein bound opioid?
alfentanil
how long do the effects of cyclizine last?
6 hours
can cyclizine have sedative effects?
yes
can cyclizine have atropine like effects?
yes
has anticholinergic effects
how much are NSAIDs protein bound
99%
why do NSAIDs have small Vd?
due to extensive plasma protein binding
what are COX2 specific inhibitors associated with?
IHD
thrombotic events - MI and stroke
what is the boiling point of sevoflurane?
58 degrees
what is the boiling point of isoflurane?
48 degrees
can sevo be a respiratory stimulant?
no
causes dose dependant resp depression
how does clonidine work and how does it effect MAC?
A2 agonist
decreases MAC
how does methyl dopa affect MAC? Mechanism of methyldopa
decrease by reducing NA levels
Alpha 2 agonist
which of the following are prolonged by renal failure?
labetolol, propofol , ranitidine
Only ranitidine
is diamorphine naturally occuring or synthetic ?
synthetic
(not an opiate)
how well does diamorphine bind receptors? what is it metabolised too?
no affinity
metabolised to monoacetylmorphine and morphine which are both active.
how does the lipid solubility of diamorphine compare to morphine?
much more lipid soluble than morphine
rapidly absorbed after sub cut injection
which of the following insulins are fast/ slow acting
soluble insulin
insulin glargine
insulin lispro
protamine zinc inuslin
isophane insulin
soluble insulin and insulin lispro = fast acting
what are cells in anterior pituitary gland called?
chromophobe / chromophil cells
which part of the brain has neural connections to pineal gland?
hypothalamus - suprachiasmatic and paraventricular nucleus
(not pituitary)
how much inulin appears in glom filtrate?
inulin is freely filtered so same conc as in plasma
how does the kidney handle amino acids?
filtered at glom
completely reabsorbed at PCT
what hormones are produced in response to injury?
aldosterone
cortisol
adrenaline/NA
ADH
endorphins
effects - fluid retention, hyperglycaemia, catabolism, sodium retention
what happens to compliance of respiratory system in pregnancy?
lung compliance - unchanged
chest wall compliance - reduced due to diaphragm elevation
what happens to minute ventilation and PaCO2 and PaO2 in pregnancy?
increased MV
slight drop in PaCO2
no change in PaO2
which nerves when damaged can cause ptosis?
occulomotor
sympathetic chain
what does the supraorbital nerve do?
branch of frontal nerve = purely sensory
frontal is a branch of opthalmic division of trigeminal
why is the pH of CSF lower than blood?
less protein in CSF
less buffering capacity
how does glucose conc in CSF compare to blood?
glucose is lower in CSF
how is the blood flow to the liver divided between hepatic artery and portal vein?
2/3 from portal vein
1/3 from hepatic artery
where are the bile ducts within the lobule?
within triad at the corners of a lobule
(in centre of lobule is hepatic vein)
what is the normal pressure or the portal system in liver?
1-5mmHg
>5mmHg = portal HTN
>10 mmHg = significant
which part of the liver lobule is most at risk of hypoxic injury?
centre
what happens to urine nitrogen output and acid/base balance during starvation?
amino acids metabolised –> increased urinary nitrogen output
acid base - metabolic acidosis - increase in FFA and ketone bodies
what happens to the respiratory quotient in starvation?
decreases
how does closing capacity change from lying to standing
no change
HOWEVER
FRC increases so less likely that closing volume will encroach on the FRC
what method measures closing capacity?
single breath nitrogen washout
fowlers
can the O2 dissociation curve determine O2 content of blood?
no
primarily determined by Hb conc
what happens to O2 dissociation curve in anaemia?
goes to right
increase in 2,3 DPG
what is shape of carboxyHb curve?
hyperbolic
straight up and then plataeus
how can airway resistance be measured?
body plethsmography
or spirometry
units for airway resistance?
kpa.s/ L
(compare to V=IR)
how does airway resistance alter with forced expiration?
increases
how does airway resistance alter with flow?
increases from laminar to turbulent flow
what happens to acid base initially with altitude?
hyperventilation
lower CO2
alkalosis
excreted HCO3 in urine - alkaline urine
what parameters can be determinants of myocardial O2 consumption?
HR, contractility, ventricular wall tension - primarily determined by these 3
however also by these indirectly
LV EDV - corresponds to preload
pulmonary capilary wedge pressure - corresponds to preload
more pre-load = more work
name 2 phsyiological shunts…
thebesian veins
bronchial venous drainage - via pulmonary veins
(not anterior cardiac, coronary sinus)
what is kety schmidt method?
measures cerebral blood flow
NOT linked to ICP
how does thoracic pressure affect ICP?
lower thoracic pressure, more drainage, lower ICP
alternatively coughing - increases thoracic pressure and ICP
how does dietary protein affect osmolarity?
increased dietary protein increases urinary osmolarity as more nitrogen is excreted.
with central venous catheters how far should the tip of the catheter go?
should sit in SVC
depends on patient size
what is the normal size of a central line catheter ?
14-16 G
corresponds to 1.63mm and 1.3mm diameter
define microshock
current of less than 1mA
but close to the heart
what point is used for zeroing on the patient?
4th intercostal mid axillary line when supine this is as close to RA as possible
what is the only factor that influences the SVP of a inhalation gas?
temp
does gas mixture above the liquid affect SVP of a gas?
no
how is a watt derived in SI units?
watt is rate of work
hence
joules / second
what is the critical temp of O2?
-119 degrees
boiling point at atm = -180
do nitrous oxide cylinders always contain liquid?
No
not at the end of their use
what is the critical temp of nitrous oxide?
36.5
boiling point at 1 atm -88degrees
define critical pressure of a gas…
the pressure required to liquify a gas at its critical temp
does boyles law take into account molecular size?
all ideal gas laws assume molecular size is insignificant
for charles law - can temperatures in kelvin and degrees be used interchangable
e.g. 10 degrees C to 20 degrees C = double temp
does this mean Kelvin doubled?
no
kelvin would be
283 to 293
increased by a small percentage
is the doppler effect true for EM radiation?
yes
does the doppler effect change the velocity of reflected sound waves?
NO
changes their frequency depending on the velocity of the object it hit
in the doppler effect how does frequency change with objects moving towards?
increase frequency
does the doppler effect depend on the piezo electric properties of the crystals?
no
what is a refractometer?
can measure conc of any inhalation agent
can also be called inferometer
measures how much light is bent (refracted) as it moves from air to sample.
out of the 2 co-axial breathing systems, which carries FGF on inner tube and outertube?
Bain = inner tube carries FGF
lack = outer tube carriers FGF
for bain coaxial system what FGF rate is required ?
2-4x MV
can bain breathing system be used in paeds
yes including 20kg
what mapelson is the Bain?
mapelson D
what is the pressure of piped gas lines?
4.1 bar
how is gas flow switched between cylinder manifolds?
pneumatic shuttle mechanism
the schrader outlet contains an internal non-return valve? T or F
T
prevents backwards flow if pressures in pipeline drop subatm.
why is o2 paramagnetic?
UNpaired e in outer shell
in a paramagnetic analyser what are the balls filled with?
N2
how does water vapour affect paramagnetic analyser?
can affect accuracy
also can stick and reduce functioing of the mechanism
how does temp affect viscosity ?
Increases temp , drop in viscosity for liquids . More energy to break intermolecular bonds
Increase in temp, increase in viscosity in gas . More energy for more collisions resisting the flow
what type of flow does viscosity affect?
laminar
turbulent flow is not affected by viscosity (instead density)
how does helium affect air flow?
lower DENSITY
promotes laminar flow
via reynolds
less work of breathing - as flow proportional to pressure drop rather than square root of pressure drop
what is the differenc between barometer and manometer?
manometer open to atmosphere - not closed at the top. measures gauge
barometer - closed at the top - measures absolute. has a torricellian vacuum
Is there variation in peak expiratory flow rate?
yes dip by 10% in morning and night
if more than 20% variation = asthma
what mechanism is a wrights peak flow meter?
variable orifice device
what is the normal peak expiratory flow rate?
450 to 650 L/min
what are active and passive trasducers?
active - generate electric current from other environmental stimulus e.g. piezoelectric
passive change electrical quantity e.g. thermistor and strain gauge
what can inulin be used to measure?
ECF vol and EGFR
how is red blood cell volume measured?
chromium labelled RBC
what are anaesthetic gas cylinders made of?
steel alloy
either from maganese molybdenum steel or chromium molybdenum steel or nickel chromium molybdenum steel.
how is the filling ratio of N20 canister calculated?
weight of contents / weight of water it could hold.
what is the filling ratio of nitrous oxide cylinders in the UK
0.75
are the confidence intervals of a good study small or large?
small -
what is the formula for standard error of mean?
SEM = SD / root number in sample
what happens to impedence if skin is wet under ecg?
reduced electrical impedence
increase risk of shock
how is the modern diathermy made safer compared to old?
return plate not connected directly to earth
why doesnt the earths magnetic field induce all ferromagnetic objects?
often not strong enough
why is coiled wire better at producing magnetic field?
neighbouring coils induce neighbouring reinforcing magnetic flux
what properties do ferromagnets have?
unpaired electrons spin
microscopic domains containing random magnetic fields
what role does the earths magnetic field have?
protects against solar and cosmic radiation
how does flux density vary with current and distance?
flux density is proportional to the current at a point and inversely proportional to square of distance
what is the formula linking Voltage to number of turns in a transformer?
V1/V2 = N1/N2
current would be
I1 N1 = I2 N2
what is the reason for propofol allergy?
preservatives - more likely in asthmatics
metabisulphite and benzylalcohol
why does propofol sting on injection?
bradykinin
what can propofol do to skin, hair and urine?
antiprureitc effects
green hair and urine- secondary to quinol metabolites
what age is propofol not liscened?
3yrs and below
where are glycine receptors found?
spinal cord
which induction agent can cause hiccups?
propofol
which NMBA is propofol physically incompatible with?
atracurium
why should propofol syringe be changed after 6 hrs?
egg lecithin derivative can fascilitate bacterial growth
why may thio be prefered to propofol in difficult airway?
patients breath quicker after thio
how do NSAIDs react with thio?
reduce protein binding, increase free proportion
why is thio solution bacteriostatic?
high pH
how many optical isomers does methohexital have?
4 optical
2 are used in racemix
how does ketamine effect heart?
directly cardio depressant however indirectly stimulates via sympathetic. however if depletion of catecholamines/ weak response in elderly, the depressive effects may become more apparent
what other receptors does ketamine act on , other than NMDA?
nACHR, L type Ca, HCN channel
opioids
how do barbiturates and etomidate effect haeme synthesis?
increase ALA production by liver
ALA is a precursor for heme production.
(hence risk of porphyria)
what neurotransmitter does paracetamol effect?
5HT3
- responsible for part of its analgesic effects.
hence partly inhibited by ondansetron
cannabinoids too
when is naltrexone contraindicated?
liver disease
where are cannabinoid receptors found?
dorsal horn
brain
which lead is best for detecting arrhythmias?
lead 2
who should have an ecg pre op
> 60 yts
or >50yrs + smoker
or any CVS disease
how long to post pone surgery post MI?
3 months
most common abnormality on ecg?
t inversion.
t wave is most sensitive
how is sinus tachy distinguished from SVT?
deep breath will slow a sinus tachy only
what is the normal velocity of aortic blood flow from doppler?
1.7m/s
how is different levels of aortic stenosis defined?
mild = valve area >1.5 cm2, gradient <20mmHg, velocity <3m/s
moderate = area 1 to 1.5
20-40mmHg, velocity 3-4m/s
severe
<1.0cm valve area
>40mmHg gradient
velocity >4 m/s
critical if <0.7
>50 mmHg
>5m/s
MAP is measured by 1/3 systolic and 2/3 diastolic why is this not accurate always?i
if HR increased ratio becomes closer to 50:50
which part of the cardiac cycle does the R wave on ecg correspond to?
isovolumetric contraction
what % of ventricle filling occurs at atrial systole?
30%
what causes cannon a waves?
heart block where dissociation between ventricle and atria contraction
- atrial contract
- at same time as ventricles contract
what does tricuspid regurg do to JVP?
increase v waves
area inside a pressure volume loop for left ventricle means what?
stroke work
how does the pressure volume loop change with increased preload?
up and to the right
what happens to gradient of Ees of pressure volume loop when catecholamines given?
increased gradient
which coronary blood flow can continue in systole?
right coronary (lower presures)
how is coronary blood flow related to heart rate?
inversely
which is the main determinant of coronary blood flow
aortic DIASTOLIC pressure
flow occurs in diastole
also equivalent to LV end diastolic pressure
what determines the resting membrane potential?
Na/K ATPase
Donnan effect - negative proteins and phosphates in the cell
equilbrium potential for K / relative permeabilities of different ions
how long does the cardiac action potential last?
200-300ms
state mechanisms for Ca entry in cardiac cell AP and Ca removal./
entry
L type Ca
ryanodine - calcium induced calcium release
uptake
- inactivation of L type (time inactivation)
- SERCA pump
- Na/Ca pump (on plasma membrae)
how does B adrenergic stimulation increase ionotrophy?
increase Ca via L type channels
what does dp/dt represent in cardiac cycle?
contractility
the higher , the better CO
when is aortic pressure the highest?
mid systole
when is aortic blood flow lowest?
early diastole
how much does pulmonary vascular resistance change at birth of fetus?
80% drop
when does foramen ovale and ductus arteriosus close?
foramen ovale closes immediately but fuses within 48 hrs
ductus arteriosus within 48hr
which organ has biggest AV difference?
cardiac
valsalva increases intensity of what murmur?
mitral regurg
all others are decreased
what is the preffered route from right atria to left atria electical signals?
bachman bundle
fetal circulation at birth - what happens to flow in IVC?
falls
at birth what pressure does the first breath generate?
- 50 cmH20
what can LV end diastolic pressure say in terms of O2?
Raised LVEDP increases myocardial work and therefore oxygen requirement.
hence determines myocardial o2 consumption
when do type A and B atrial receptors discharge?
Atria have Type A stretch receptors that discharge predominantly during atrial systole and
Type B receptors that discharge predominantly during atrial diastole.
what is bainbridge reflex?
stretch of RA causes increased HR
what is Lusitropy?
Lusitropy is a term that decribes myocardial relaxation.
Catecholamines have a positive lusitropic action (allowing rapid relaxation) whilst hypercalcaemia inhibits relaxation due to incomplete calcium reuptake (an essential process in diastole).
how does the timing of contraction of chambers compare?
RA contration preceeds LA contraction, however LV contaction precedes RV contraction.
what happens to urinary nitrates in trauma?
increase
due to catabolism
how does mitral regurg effect afterload?
reduces it
low resistance pathway back into atria so less tension needed by LV
what is afterload likely to be in HF?
lower
what is the anrep effect?
If afterload increases, SV initially falls. SV is then (partially) restored by an increase in LVEDV.
what is afterload?
Afterload is the tension developed in the LV wall during systole.
SVR is the commonest index of afterload but is not equivalent to it
how much blood comes from hepatic artery?
The hepatic artery is a branch of the coeliac axis.
1/3 of hepatic blood comes from the hepatic artery.
2/3 portal vein
during exercise, what is the main factor increasing CO?
HR
does CVP change in exercise?
no
what happens to haematocrit and blood volume in exercise?
fluid loss
haematocrit increases
blood volume drops
what does hyperkalaemia do to automaticity?
increases it
what acts as a marker for preload and afterload?
preload - CVP (right side), pulmonary cap wedge pressure (left ventricle preload)
afterload - MAP / SVR
both left and right sympathetic chain innervate heart - what is their relative purpose?
left - force of contraction
right - rate
which vagus nerve innervates SAN vs AVN?
SAN - right vagus
AVN - left vagus
what changes are quicker - parasympathetic changes to heart or sympathetic?
para
what ratio of adrenaline / NA released by adrenal medulla?
adrenaline 4: 1 NA
what is normal aortic diameter?
2.5cm
what type of capillaries present in OVLT?
fenestrated
what do mesangial cells do? what do pericytes do?
contract to reduce S.A for Glomerular filtration. similar to pericytes
pericytes are found outside of the capillary - contract to regulate flow
will regulate capillary permeability by altering pore size
what type of capillary present in GIT? where else has this type of capillary?
fenestrated
endocrine glands , hypothyroid, pituitary, pineal gland
choroid plexus
how much does lymphatics drain?
2-4 L / day
when is the glycolayx disrupted?
sepsis , surgery - causes leaky capilaries.
oncotic pressure less significant
which tissues dont have lymphatics?
cartilage, CNS, eyes
where does the cisterna chyli lie?
L1/ L2
5-7cm long
what nodes do following organs drain into?..
adrenals
gonads
liver
abdo wall
adrenals and gonad = para aortic
liver = mediastinal nodes
abdo - mediastinal, superficial groin, axillary
where do T and B cells mature
T thymus
B bone marrow
how does CO of left side of heart compare to right?
left > right
recieves additional drainage from bronchial veins
how much is PVR compared to SVR?
1/10th
what is the blood flow and O2 consumption of the brain?
750ml/min
45ml/min
what is the blood flow and O2 consumption of the heart?
250ml/min
30ml/min
what is the blood flow and O2 consumption of the skeletal at rest?
1L/min
50ml/min
what is the blood flow to liver and kidneys?
kidneys - 1.25L/min (25%)
liver - 1.5L/min (30%)
what capillaries are found in spleen?
sinusoidal
what % of blood volume is in the veins?
around 50%
what is the main driver of lymph flow?
positive hydrostatic pressure in tissues.
the length of the cardiac cycle shortens with HR, is this linear?
no
which Ca channels are present in phase 4 and 0 of pacemaker AP?
phase 4 - T type
phase 0 - slow L type - hence slower upstroke that fast VG Na
what level do sympathetic fibres innervating heart come from?
T1 to T5
why is VOO pace mode safe in surgery?
ventricles are being paced
but nothing is being sensed hence no interference
what parameters are surrogates for contractility measure?
Stroke work
stroke volume
end systolic pressure
what type of hormone is angiotensin?
peptide
AT1 = 10aa
AT2 = 8aa
what is normal value for PVR in health?
160 dyn/sec / cm5
what is max stroke vol in normal adult?
100-120ml
in athletes may go higher - up to 180 ml
what is triamterene?
a diuretic
acts on DCT
stops Na reuptake
in plasma protein binding - are the unbound and bound drug related?
The bound and unbound portions of a drug are in equilibrium and therefore closely related.
the unionised proportion is what binds plasma protiens
define clearance..
Clearance is that volume of a body compartment (often blood or plasma) from which a drug is completely removed per unit time, usually expressed in ml min-1.
what is edrophonium?
Edrophonium has a quaternary nitrogen, which binds to the anionic site of acetylcholinesterase,
it is not an ester, so cannot bind to or be metabolised by the enzyme.
used in diagnosis of myasthenia gravis
how does MAC alter with temp?
increases with hyperthermia
how is MAC affected by CO2 tension, anaeamia, Mg?
AC is not affected by haemoglobin concentrations, arterial CO2 tensions or plasma magnesium concentrations.
what are microsomal liver enzymes?
group of enzymes of ER of hepatocytes
include CYP450
what induces cYP2E1?
Chronic intake of barbiturates, alcohol or cigarettes
how does lithium affect NMBA?
can prolong
(acts like a sodium ion)
what can prolong competitive NMBA?
hypothermia, hypokalaemia, hypocalcaemia and metabolic acidosis.
Mg
gentamicin
how does carbamazepine effect NMBA?
inducer
shortens effect
methods of measuring anaesthetic gases…
infra red
mass spec
ultrasonic
refractormeter
raman spec
photoacoustic spec
(NOT PARAMAGNETIC)
(not chromatography - too slow)
how does peak inspiratory flow compare to expiratory?
peak expiratory flow is much higher.
(flow in inspiration is highest at begining and then decreases. same for expiration).
how should frequency of a system compare to fundametal frequency?
The frequency response should ideally be above the first 8-10 harmonics of the fundamental frequency (heart rate), i.e. ten times the heart rate.
how long is the oesophageal doppler probe inserted to?
40cm
does ambient pressure affect rate of diffusion?
no
how many quarternary ammonias in
- acetylcholine
- succinylcholine?
acetylcholine = 1
sux = 2
how is aspirin metabolised?
Aspirin is rapidly metabolised by esterases in the intestinal mucosa and liver to acetic acid and salicylate;
what does aspirin do to urate excretion?
In normal doses (lesser than 2g per day), aspirin inhibits renal tubular secretion of urate
(not urea)
how much protein binding of aspirin?
80-90%
what are the causes of hypotension with morphine?
vagal stimulation
arteriole dilation (directly and sympathetic)
histamine release
decreased sympathetic activity
( myocardial contractility maintained)
what additional affects does pethidine have?
acts like atropine - anticholinergic
local anaesthetic effect
NA reuptake inhibition
what molecule is pethidine structurally related to?
atropine - anti Ach effects
what is the half life of pethidine compared to morphine?
pethidine
can ephedrine inhibit MAO?
yes
although not its main role / not clinically that significant
name 3 acetylcholinesterase inhibitors and state their duration of action
Edrophonium - shortest duration of neostigmine
pyridostigmine - longer than above
what type of amine does neostigmine have? what does this mean?
quarternary
doesnt cross BBB
poor oral absorption
what is Disopyramide
Disopyramide is a Class 1a antiarrhythmic
what does hydralazine do?
dilates arteries (not veins) via smooth muscle
how does GTN affect CVP?
falls
dilation of vessels
why is headache a side effect of GTN?
mengingeal dilation
why does GTN have low oral bioavailabity?
metabolised in both gut wall and liver
high first pass
what is diazoxide?
slows release of insulin from pancreas
increases glucose
for those with hypoglycaemia
which penicillin is active against penicillinase producing staphlococci
flucloxacillin is effective against penicillinase-producing staphylococci
which adreno receptors are present on uterus?
B2
hence salbutamol causes uterine relaxation
(NA has no effect on uterine tone as no A1)
what drug is flumazenil structurally similar to?
benzos
what is plasma protein binding of ropivacaine?
Plasma protein binding of ropivacaine is similar to that of bupivacaine; it is about 94% protein bound.
what is the pKA of lidocaine and ropivacaine?
he pKa of lidocaine is 7.9 and that of ropivacaine is 8.1
which flow measurements rely on variable orifice vs variable pressure?
variable pressure, fixed orifice = pneumatochograph
variable orifice, fixed pressure
= rotameters, writght peak flowmeter
how does wrights respirometer work?
measures a volume and then flow can be worked out from this.
wet spirometer also measures a volume
what is a lusitrope?
A drug that increases relaxation - e.g. B blockers
what is the minimum setting for expiratory valve to open?
50 Pa
what is the intracellular mechanism for ionotropy? which drugs act
B1 = PKA –> phosphotylates L type Ca Channels. dopamine, dobutamine, NA
Phosphodiesterase inhibitors - milronone
levosimendan - increases sensitivity to contractile units to calcium without increasing
what waves does doppler effect use
both sound and electromagnetic
with the doppler effect how does the frequency shift when blood is moving away?
shifts to lower frequency
can metaraminol show tachyphylaxis?
yes after days - not as quick as ephedrine
what is the strength of magnetic field in MRI
2-3 tesla
what does an osmolarity of 700mOsm/kg correspond to?
An osmolality of 700 corresponds with a specific gravity of 1020
what is the specific complication of vasopressin?
intra abdominal complications
from sphlanic vasoconstriction
what blood gas abnormality is seen with adrenaline infusion?
lactate acidosis
how does enoxamone work?
phosphodiesterase inhibitor
ionodilator
similar to milronone
how is Confidence interval calculated?
mean +/- 1.96 SEM
how many half lives and time constants to complete exponential process?
5 half-lives but just 3 time constants for an exponential process to be almost complete.
why is a capacitor used in lead of diathermy plate to earth?
The capacitor provides a high impedance to mains frequency current and prevents patient injury by preventing current flow to earth.
only allows high freq AC
how is ecg leads design to reduce current leak
a resistance is incorporated in each lead from the patient to an ECG machine
what happens to soda lime when left unused
hen left unused, the carbonate on the surface of the granules will move to the inside of the granule and the hydroxide moves to the surface
will regenerate
what is the advantage of jackson rees?
no valves - low resistance to flow
can add PEEP
what is pressure of N20 in pipeline?
4.1bar
what valve does the schrader system work with?
one way non return
name drugs metabolised by esterases
esmolol
aspirin
diamorphine
etomidate
local ester anaesthetics
remifentanil
how does diamorphine relate to morphine?
Diamorphine is 3,6 diacetylmorphine, a di-ester of one molecule of morphine and two molecules of acetic acid.
what can salicytates do to prothrombin?
hypoprothrombinaemia
how much protein binding is paracetamol
10%
which induction agent is the only one not to cause sleep in one arm brain circulation?
ketamine
does ketamine have active metabolites?
yes - norketamine
what is terminal elimination half life of propofol
5-12 hours
name the macrolides and mechanism
50S inhibition
erythromycin
clindamycin
Azithromycin
Clarithromycin
which abx inhibit 30s
tetracyclines
aminoglycosides
how is SVT treated?
vagal manouevres
6mg adenosine
12mg adenosine
18mg adenosine
if shock, Chest pain, HF signs = DC cardioversion
describe how a pH electrode works?
measuring electrode
- pH sensitive glass
- silver/AgCl electrode
- buffer solution
reference electrode
- permeable membrane
- solution of Kcl
- mercury/ calomel electrode (or silver/ agcl)
blood in contact with both electrodes
- H+ ions accumulate on pH sensitive glass (do not cross) but create a charge diference (i.e. attract negative ions) - this is called ion exchange
- buffer keeps pH constant
potential difference is measured in mV
60mV = 1 unit pH
the reference electrode and ionic solutions complete the circuit.
how does an osmometer work?
uses colligative properties of solution to measure osmotic pressure.
Colligative properties are physical properties that are dependent on number of dissolved particles rather than the identity of the solute.
These include elevation of boiling point, reduction of freezing point, reduction in vapour pressure and change in osmotic pressure.
usually depression of freezing point is used
what does aspirin have a higher affinity for COX 1 or 2
COX 1
what does heparin do?
binds ATIII and increases breakdown/inhibition of factor 2, 10 and 12,11,9 (intrinsic pathway)
LMWH only 2 and 10
fondaparinux only 10
protamine sulphate allergy can overlap with which other allergies?
allergies to protamine - in some insulins, fish and in sperm (vasectomized men)
what can be used to treat von willebrand disease?
desmopressin - stimulates release of vWF
what is the new reversal agent for apixaban and rivaroxaban ?
andexanet alfa
what is the role of citrate in blood products?
prevents coagulation
binds calcium
although since clotting factors have been removed, this is not so much of an issue hence SAG - M (the most common prep) doesnt contain citrate
what is the rarest and most common blood type?
AB negative = rarest
O most common
what type of inheritance is the ABO?
mendelian
what ab are present in ABO system and rhesus?
ABO = IgM - cant cross placenta
rhesus = IgG = can
which chromosome is rhesus antigen on?
chrom 1
what does sickle cell do to Hb dissociation curve?
shifts to the right
hence the anaemia seen isnt as severe as the same anaemic value in HbA because HbS can give up O2 to tissues more easily.
what happens in sickle cells - mutation and aa change?
adenine –> thymine
glutamate –> valine
on B chain of Hb
what does adenine do to packed red cells?
increases ATP for use and prolongs shelf life
however does also decrease 2,3 DPG
how are ABO antigens identified?
terminal sugar on the H antigen
where is ABO antigen found?
many different tissues not just RBC
what is the leading cause of mortality and death following transfusions?
TRALI
is donor blood tested for malaria?
no not routinely
which Ab is involved in acute haemolytic reaction and delayed haemolytic reaction
acute = ABO = IgM
delayed = others = IgG
what is the difference between intra and extravascular haemolysis ?
intra - occurs within vasculature, RBC rupture in blood stream
extra - in liver/ spleen - RBC ingested by macrophages
haptoglobin binds free Hb so this is lowered in intravascular but not in extra vascular
acute haemolytic reaction = intravascular
delayed = extravascular
what type of endothelium is present in kidney tubules
in proximal tubules - tight junctions
in bowens capsule fenestrated capillaries
in the kidney what is the difference between transcellular and paracellular transport?
transcellular - through cell
Paracellular transport occurs through both tight junctions and intercellular spaces via diffusion/ osmosis (not active)
what is FICKs law?
rate of diffusion proportional to…
SA (Con difference) / Distance
what FGF does a mapelson A / magil require?
minimum 70% of MV in spontaenous
2-3x MV in controlled
what is the capacity of a reservoir bag?
2L
what is the function of a reservoir bag in a breathing system?
prevents wastage of FGF during expiratory pause
visual aid
can meet peak inspiratory flow - otheriwse would need very high FGF rates to do this and would be wasteful at other points in vent cycle
which breathing systems are T pieces
D, E, F
why is magils inefficient in controlled ventilation?
The Magill system is inefficient during controlled ventilation because much of the gases are vented via pop-off valve
what gas is used in a quantiflex mixer
N20 can be safely delivered via a Quantiflex mixer which allows a full range oxygen/nitrous oxide mixtures to be administered from 21-100% oxygen so avoiding accidental hypoxic mixtures.
does the cardiff aldasorber increase work of breathing?
no low resistance device
how packed is a soda lime cannisters?
50%
does the concentration of inspired vapour exceed that on the setting in low flow anaesthesia at steady state?
During maintenance (i.e. at steady-state), the inspired volatile agent will eventually reach but never surpass the set concentration on the vapouriser.
what type of isomer is enflurane and isoflurane?
structural
what does isoflurane do to CVS system?
SVR drop
reflex tachy
minimal change to myocardial function
coronary steel
which inhalation agent doesnt have a chiral centre?
sevo
what does sevo produce when stored in glas?
hydrofluric acids
what molecule is sevo flurane
polyfluorinated methyl isopropyl ether.
which inhalation agent has largest molecular weight and what is this?
sevo, 200
molecular weight of desflurane
168
what inhalation agent should you be careful with when using adrenaline and why?
halothane
sensitiser heart to catecholamines
which bonds are most stable in inhalation agents?
C-F
the liver produces tri-fluroacetyl chloride under what conditions?
oxidative conditions
boiling point of desflurane
23.5
what can desflurane do to heart if mac >1
tachycardia and HTN
how does N20 cause sub acute degen of the cord?
oxidises B12 in colbalt ion
means methionine synthase is no longer able to function
inhibits DNA synthesis
needed for myelin
in descending order which inhalation agents affect cerebral blood flow?
halothane
enflurane
N20
isoflurane
why is halathane prepared with 0.01% thymol?
prevent decomposition by light.
what does halothane do to ANS?
bagal stimulation
can cause bradycardia
how much N20 is metabolised?
less than 0.01%
critical pressure of O2
50 bar
