Cardiology basic science Flashcards
What Anaerobic threshold is considered high risk in CPET?
<11ml/kg/min
what is basal meta bolic rate?
3.5ml/kg/min
What anaesthesia considerations should be kept in mind for a patient with aortic stenosis?
Avoid rapid drops in systemic vascular resistance (SVR): Maintain blood pressure, as patients have reduced cardiac output and rely on afterload to maintain perfusion.
Slow induction: Gradual induction helps prevent hypotension.
Maintenance: Use drugs that avoid further reduction of SVR, like phenylephrine if necessary.
Monitor: Close monitoring of heart rate, blood pressure, and rhythm is essential.
Oxygen pulse is a term used to describe? the equation is?
oxygen uptake per heart beat
VO2/heart tare or SV x (CaO2-CvO2)
Current guidance suggests when to do a pre-op ECG
If 1 or more risk factor and undergoing intermediate to high risk surgery
Main indicators for pre-op ECHO? 2
Undiagnosed heart murmur
Evaluate LV function in pts with heart failure or dyspnoe of unknown origin
When is pre-operative stress testing undertaken?
when to consider?
> or - to 3 risk factors and pts undergoing high risk surgery
consider in those with > or- 2 risk factors undergoing high risk or pts have intermediate risk surgery
Stress radionucleotide myocardial perfusion imaging uses what?
dipyradimole-thallium imaging
Clincal applications of stress echo? 4
diagnose CAD (inducible RWMA)
asses myocardial viability ptiot to revascularisation
identify a culprit lesion in pts with known CAD
risk stratification in pts with risk factors for cardiac disease prior to surgery
When to do preop coronary angiography 3
acute MI, NSTEMI and unstable angina
refracotry angina not responsive to medical treatment
Apfel and Koivuranta scores are used to predict?
PONV risk
What scoring systems are available for pancreatitis?
Which one for ICU?
Glasgow and ranson
APACHE
pre-operative optimisation with medication in coronary disease has 2 aims…
plaque stabilisation
reduction of ischaemia
What did the POISE study demonstrate?
benefits of b-blockers lies ina small high risk group
give for 1 month pre-op and aim hr 60-80, systolic >100, use long acting B1 cardioselective if needed (bisoprolol or atenolol)
What did the DECREASE 3 trial show for statins?
thos given statins in high risk group for 30days pre/post op had halved incidence of detectable ischemia and cardivasc. mortalitiy
what do drug eluting stents release?
Paclitaxel or sirulimus
what are the pleiotropic effects of statins? 6
increased endothelial production of NO synthas
Decreased endothelin 1 production
improved thrombogenic profile
decreased CRP/inflammation levels
plaque stabilization
reduced atherosclerosis
Drug-eluting stent- what is mortality rate from stent thrombosis?
20%
what to do with dual antiplatelet therapy?
continue aspirin,
if clopidogrel needs stopped 5-7 days pre op then restart asap
tirofiban has a short half life of 2hrs- good alternative
delay surgery 6-12 mnths after drug eluting stents or 6 weeks bare metal stents
CVP- A wave represents
atrial contraction
c wave in CVP_
unclear but possibly due to tricuspid bulging during ventricular contraction
x- descent in cvp?
during ventricular systole- downward displacement of the ventricle and atrial relaxation
v wave in CVP?
venous filing of the atria against a closed tricuspid valve
Tricuspid regurgitations effect on v wave?
causes it to become more prominent
Y descent in CVP is?
Yawning opening of the tricuspid valve allowing passive ventricular filling
What does a rapid deep y descent potentially indiate
tricuspid regurgitation
what does a rapid short y descent potentially indicate
constrictive pericarditis, right sided diastolic failure- restrictive RV disease
what does a slow y descent indicate?
obstructive RV filling: tricuspid stenosis, right atrial myoxoma
What constitutes the largest single source of blood stream infection in hospitalized patients?
Central lines
Name ways to minimise infections with central lines
- subclavian rather than jugular or femoral
- totally implantable>tunnelled>untunnelled
- PICC
transpartent dressing
no active infection prior to insertion
single lumen catheters
specialist nursing care to maintain cleanliness
4 pieces of data that can be gained from a PAC?
Pressure monitoring (PAC gives direct measurements of central venous, right sided intercardiac and PAP, PCWP
Mixed venous oxygen saturations
3. cardiac output with thermodilution, uses stewart hamilton equation to estimate CO
4. Vascular restistance- calculate by combing pressure and flow data
Assuming no valvular impedence- what 3 things impede flow in a arterial waveform?
- Resistance (related to blood viscosity and valvular geometry)
- Inertia- the volume of blood to be moved
- compliance of the system( distensibility)
Where should transduce be placed within the PAC system?
mid point in a coronal plane and then transversely at junction og 4th intercostal space and the sternal margin
Normal RV pressures are?
Systolic 15-25 mmHg
Diastolic 3-12mmHg
what is usual PAOP
6-15 mmHg
causes of raised PAP with high PVR?
PE, pulmonary hypertension, hypoxic pulmonary vasoconstriciton
Raised PAP with normal PVR?
mitral valve disease, left to right shunt
Raised a wave in PCWP trace represents?
increased resistance to LV filling
Mitral stenosis, LV systolic or diastolic dysdfunction, volume overload, decreased LV compliance, (eg myocardial ischaemia, pr infarction)
Raised V wave in PCWP trace?
occurs when systole induces retrograde flow eg in mitral regurgitation or VSD complicating MI
when should PAOP be recorded- during which point of the breath cycle?
at end inspiration when intrathoracic pressure is equal to atmospheric pressure
pre-load in PAOP is represented by? and where (think west zones) must the tip of catheter lie and why?
LV end diastolic volume measurement- L atrial pressure
Weat zone 3 ( venous and arterial pressure is greater than alveolar pressure- so a continuous column of blood is created between tip of catheter and the left atrium)
Interpret preload estimations in PAOP with caution in 4 situations
- lv diastolic failure
- mitral valve disease
- high levels of intrathoracic pressure- PEEP
- raised PVR
what trial showed no benefit for icu patients CO monotioring with PAC as opposed to bedside/biochemical eg lactate/BP/Urine output or no monitoring
PAC-man
pulse contour analysis is reliant on what factors being in place?
Ventialted patient with stable intrathoracic pressure and >8ml/kg TV
How often does PiCCO system require calibration? what is needed for the system to work?
8 hourly cold water calibration
Art line with thermistor tip and a CVC line
temporal analysis of transpulmonary dilution curve allows what additional variables to be calculated? 2
Extrvascular lung water- cardiac or non in pulmonary oedema-a predictor of mortality in critically ill pts with acute lung injury
2. global end diastolic volume- volume based measure of preload (SV)
examples of uncalibrated monitors of CO …2
PRAM pressure recording analytic method
Flotrac
assumptions made for Oesophageal doppler measurements? 4
constant aortic blood flow
radius of aorta based on either a direct measure or data variables
Angle between doppler beam and blood flow is within 30 degrees of axial flow
fixed ratio of blood flow between upper and lower limbs
Adrenaline admisnistration is less predictable than noradrenaline due to its actions on?
peripheral Beta 2 receptors which can lead to vasodilatation