Applied Cardiovascular Physiology Flashcards
How does anaesthesia/surgery impact the CVS
- Pharmacological effects on myocardium/SVR/CO
- Stress response to surgery: neural/humoral
- Blood and fluid loss
Define cardiac output
The volume of blood leaving the heart in one minute
Normally: 5L/minute at rest
CO = SV x HR
Define preload and its determinants
The intraluminal pressure that stretches the right/left ventricle to its end diastolic dimensions
Reflected by:
Left: LVEDV = ± LVEDP = ± PCWP
Right: RVEDV = ± CVP
Define afterload
The stress developed in the left ventricular wall during ejection, and reflects the force opposing shortening of the myocytes
Reflected by:
Left: SVR and MAP
Right: PVR
Define myocardial contractility
Intrinsic ability of myocytes to generate mechanical power at a given preload and afterload
What is the cardiac index CI
Adjusts the CO for the patient’s size
CI = CO/TBSA
Normal: 3.2 L/min/m^2
Draw the Frank Starling Relationship including the following:
Normal Heart Failure Cardiogenic shock Exercise Positive inotropy Negative inotropy
Page 30 of Chambers
What % of ventricular filling is contributed by the atria
< 15% (20 - 40% in MS)
Draw the cardiac cycle (Wiggers diagram) including:
Aortic pressure Atrial pressure Ventricular pressure Ventricular volume Electrocardiogram Phonocardiogram The phases of the cycle And the valve status
See Notability ‘Cardiac Physiology” and Chambers page 119
What is the mnemonic to assist with what physiological process is represented by the a,c,v waves and x and y descents on the right atrial pressure (CVP) waveform graph.
What is the trick to drawing this waveform
a - Atrial contraction
c - Cusps of tricuspid av valve bulging in during ventricular contraction
x - RelaXing atrium
v - Venous return and filling of right atrium
y - emptYing right atrium during passive ventricular filling
Draw the ECG first.
The c wave corresponds with the S wave and the top of the v wave corresponds with half way between T wave and next p wave and it is lower in amplitude than the a and c waves.
Describe the innervation of the heart and control of heart rate
Baroreceptor reflex anantomy:
- Glossopharyngeal nerve (CN9) afferents from Carotid baroreceptors (at bifurcation of common carotid) to Medulla.
- Vagus nerve (CN10) afferents from aortic arch baroreceptors to Medulla.
Efferents:
Vagus efferent from Medulla to SA node
SNS efferents from SNS ganglia to SA node, myocardium, arterioles, venules, and adrenal medulla
Describe the baroreceptor reflex
Increase MAP –> Stretch baroreceptors (Aortic arch / Carotid sinus) –> increased firing –> increased APs –> Vasomotor center (Medulla) –> Vasodilator area –> inhibits SNS outflow
Decrease MAP –> opposite via increased SNS outflow from vasoconstrictor area
Vasomotor Center
1. Vasoconstrictor area –> tachycardia, increased contractility, vaso and veno constriction, adrenal medulla release of adrenalin from.
- Vasodilator area –> slows heart rate, reduces myocardial contractility and cause VD –> MAP to normal
List the factors that control blood pressure
- Intrinsic regulatory properties of the heart
- Autonomic pathways
- Vasomotor center inputs
- - baroreceptor reflex
- - Cerebral cortex
- - Stretch receptors in lung (exercise)
- - Pain
- - CO2
- - Hypoxia - Hormonal mechanisms (vascular tone)
- RAAS
- Vasopressin
- Adrenalin/Noradrenalin - Hormonal mechanisms (Salt and water balance)
- RAAS
- ADH
How do inhalational agents affect the cardiac output?
Myocardial depressant (mainly halothane)
Vasodilation
Altered baroreceptor activity
Tachycardia (in attempt to maintain CO)
How do induction agents affect the CVS
Propofol, Etomidate, Thipentone
–> Myocardial depression and decreased SVR
(Etomidate the most CVS stable)
Ketamine
- -> Increases CO by stimulation of endogenous catecholamine release
- -> decreases CO if endogenous catecholamine stores are depleted
