Past paper Qs from Google drive Flashcards
What is most imporant electrical component in defib circuit for changing AC mains?
Primary application of rectifiers is to derive dc poser from ac supply. all electronic devies require dc so rectifiers are used inside power supplies of all electronic equipment
pacemaker cells demonstrate automaticity. What drugs increase slope phase 4 of PM AP?
SNS activation releasing NA increasing pm rate by decreasing k and increasing slow inward ca and na, pacemaker current is enhanced.
other drugs e.g. ca blockers will cause brady cardia by inhibiting slow inward ca current in phase 4+0
drugs affecting autonomic control or autonic receptors e.g. betablockers, muscarinic antagonists directly or indirectly alter pm activity
62 yo admitted in fast af with renal failure, given digoxin. initial dose is 5-10x subsequent doses reason for this is?
about 70-80% of oral digoxin is absorbed mainly by prox part of SI. degree of binding to serum albumin is 20-30%. dig is ex distributed large vol of d. high conc in heart and kidneys but skeletal muscles form largest digoixin storage. half lfe of elimination in healthy person varies between 26-46hrs. main route of elim is renal excretion closely correlated with gfr.
new muscle relaxant developed with 3 positive charge ammonium groups. hepatic ex ration =0.15 and terminal elimination half life is 15mins. what contributes to its fast terminal elimination time?
extraction ratio ratio of 0.15 means that it wont have metabolised by liver.
charged molecule so is not rapidly redistributed and not likely to be excreted by the lungs because it is charged and presumably not volatile
renally ecreted agent would have a terminal elimination half-life of more than 15mins.
some commonly used muscle relaxants are esters that are metabolised in tissue and plasma - most liekly explanation for rapid rate of elimination.
cs with iso/n20 and mac 1.5 and an anaesthetic with iso+air mac 1.5 which is more likely to happen with iso/nitrous?
differing b:g coefficients of nitrous and iso are responsible for more rapid recovery from nitrous
no difference in risk of awareness or intraoperative blood loss
exposure to nitrous is too short to cause effects in fetus and if anything nitrous mix would be most cardiostable and cause less low blood pr.
20 yo has PaO2 8kpa what is the least likely reasons for this?
PE/ARDS/bilat bronchopenumonia/ ascent to altitute 8000m with barometric pr 33kpa/ r bronchial intubation and vent with ippv and fio2 of 1.0.
From alveolar gas equation
Pao2= Fio2(Patm - PH20) - (PaCO2/RQ)
0.21(33-6.25) = 5.6 this is before taking into account co2 so PaO2 will be about 2kpa much less than 8kpa. if at high altitude so this is answer.
pe/pneumonia/ards easily give pao2 of 8kpa.
endobronchial intubation is not always assoc with desaturation but if the lung is not deflated and hypoxic pulmonary vasoconstriction has not occurred then it can cause even in most health of patients.
in fit normal adult which regional circulation receive highest blood flow per gram at rest?
...ml/min/100g 2000 - carotid bodies (high vo2 consumption 8ml o2/min/100g; tiny av o2 difference respond to Pao2 NOT oxygen content) 360 - kidneys 300 - adrenals 160 - thyroid 95 - liver 70 - heart 50 - brain 25 - bronchi 4 - muscle (inactive) 3 - skin 3 - bone
T3/4 molecules are bound inside thyroid gland by:
T4/3 covalently bound to thyroglobulin protein molecule ( as they are aas with iodine attached) they are cleaved from protein complex by protease enzymes before they are classed as free t3/4
Mapleson D Bain circuit attached to ett fit and well 25yo spont breathing with fgf 10l/min. malfunction with apl valve so no gas is vented. after one minute anaesthetist notices problem and disconnects circuit. no harm. what is most important mechanism that protecte pt from barotrauma in this situation?
Reservoir bag protects pt from increased pr in circuit as elastic so size of bag increases and stretches allowing for increase in volume
osmolarities on iv fluids which has highest osmolarity? 0.9% saline 5% dextrose 18% saline 4 % glucose 4.5 % albumin 10% mannitol
osmolarities on iv fluids 0.9% saline = 310 5% dextrose =253 18% saline 4 % glucose = 271 4.5 % albumin = 330 10% mannitol = 550 - highest osmolarity
pascal is si unit but is derived from a base si unit. what is pascal in base si units?
Pascal = N/m2 of kg m-1 s -2
what does changing gain in uss change?
digitally enhances image
uss from transducer are attenuated due to absorpiton, reflectionand scattering by tissues
function of gain is to counter this attenuation when the final image is produced
returning uss waves converted to electronic signla by transducer
gain - electronic amplicfication of signal thus in effect amplifying the reutning uss waves reflected back by the patient’s tissues
causes a genralised increase in brightness of image
as gain is a signal amplification process it could loosely be said to increasing the amplitude f uss waves however, being pedantic, uss waves themselves are not being physically amplifed because it is impossible to amplify the actual sound wave being reflected back - only the elctronic signal generated from the uss wave can be amplified. tuss technically, gain “digitially enhacnes the image” nad does not directly “ increase the amplitude of uss waves”
in arterial bp monitoring what variable which if it was changed would have the biggest effect on MAP?
likely position of transducer as small momvement lead to huge changes in bp.
overdamping will cause a flattened trace but mean should be same.
resonance may give rise to a hyperdynamic reading but with the mean staying the same
Bias can invalidate conclusion drawn from clinical trails. Which of the following is least likely to contribute to bias?
Randomisation is most important factor in trail design to prevent bias. (prevents selection bias in allocation of interventions, promotes similarity between treatement groups in terms of baseline characteristics at entry to trial, minimises numerous ocnfounding factors which could lead to uncertainty over genuine cause of any tretment difference found.
other: blinding removes bias from investigators or patients being aware of group allocation
case control selection is vulnerable to selection bias (systematic difference btw baseline characteristics of groups compared
power calculation used to calc no of pts needed in study to demonstrate defined clinically significant effet (effect size) with acceptable level of statiscal significance however effect size used in calculation can be under/over estimated due to bias.
During an op, you anaesthetise a pt for a lap procedure. 10mins post induction temperature via oesophageal probe drops 2 degrees, theatre is heated to 25 degrees and has laminar flow system. Best reason for rapid drop in temp?
Redistribution of body heat from core to peripheries ( vasodilatation)
Core hypothermia:
1. redistribution - largest drop in core temp. vasoldilatation, body heat content remains unchanged
facotrs affecting redistribution: patients initial heat content, more heat transferred from warm core to cold periphery and pts with cool peripheries will suffer a greater degreee of core hypothermia. neonates and infant have larger core compartment than adults, as it extends closer to body surface. body morphology obese patient have warmer peripheres as adipose acts as insulator
2. linear
3. plateau
