Exam 1 - Lecture I (Renal Re-Cap, Vascular Properties & CV Cycle) Flashcards
Fluid that is completely cleared of a substance is describing what?
Clearance.
(Usually referring to plasma.)
Slide 2
Clearance is measured in what units?
Volume/Time (mL/min)
Slide 2
What is Free Water clearance?
It is a # that tells you how much pure water is being removed from the blood.
Slide 2
What hormone governs Free Water clearance?
ADH
Slide 2
Your patient is hyponatremic. Do you expect her Free Water clearance to be high or low?
High!
The kidney will get rid of free water to increase her osmolarity.
(You would expect low FWC if she were hypernatremic)
Slide 2
Do we typically reabsorb ALL of the glucose we initially filter?
YES!
Slide 2
Identify each formula.
Notice the pattern -
most equations are (UxV / P)
The term that describes how elastic or stretchy something is? (Usually talking about vasculature)
Compliance!
Slide 3
What is the formula for compliance?
Change in volume / Change in pressure
Arteries are more compliant than veins. True or False?
False!
Veins are overall more compliant - the reason they serve as a large blood reservoir. 🩸🩸
What is the most compliant artery?
Why?
The aorta - it has to be able to absorb the differing pressures.
This also helps keeps the load down on the left ventricle.
Slide 3
The difference between SBP and DBP is? What are the normal, healthy values of each?
Pulse pressure (40) - 120/80
Slide 3
This term describes how rigid something is.
Elastance.
Slide 3.
What is the relationship between compliance and elastance?
Elastance is inversely proportional to compliance.
(The higher the compliance, the lower the elastance & vica versa)
Slide 3
What two things, from lecture, does the aorta serve as?
- Pressure reservoir
- Secondary pump - keeps blood flowing between heart beats.
Slide 3
What can pulse pressure tell you?
How stiff your arteries are.
Slide 3
What is a normal CVP seen in a healthy patient?
0mmHg
Pressure should dramatically decrease as blood returns to the heart.
Slide 3
What is the Delta P of the systemic circulation?
100-0
Slide 3
What are 3 reasons the pulmonary circulation is more compliant vs. the systemic?
- Closer to heart (shorter pathway)
- More vessels to choose from
- Less resistance vessels compiled with smooth muscle
Slide 3
The large arteries have higher elastance than than the aorta. True or False?
True!
The larger arteries are more rigid (elastance) thus experiencing higher pressures than the aorta.
What is the Delta P of the pulmonary circulation?
16-2 mmHg
Slide 3
List the pressures each of these chamber’s experience: LA, LV, RA, RV.
LA: ~2-5 (should always be low)
LV: 0-120 (lots of variability)
RA: 0-4
RV: 0-25 (variable as well)
Slide 4
You give epinephrine. Would you expect your patients capillaries to constrict? Why or why not?
No!
Capillaries have no smooth muscle & cannot respond to pressers.
Slide 5
Which vessels in the body make up most of the total cross-sectional area? What is the numerical value?
Capillaries!
4500 cm^2 (Lange)
2500 cm^2 (Guyton)
Slide 5
According to lecture, which vessels accept volume the best? Why?
Veins
The walls are thin, giving them lower vascular resistance.
Slide 5
Why is the velocity (V) of blood slower in the venae cavae vs the aorta?
Because the venae cavae make up a larger cross-sectional area.
(remember there are 2 vessels = CSA 8cm^2
V= Q/A
Slide 5
What is the formula for velocity?
How do calculate velocity for the circulatory system?
V = F/A
Flow rate / Cross-sectional Area
Slide 5 & 6
What is the cross-sectional area for the Aorta and the Venea Cavae?
Aorta: 2.5 cm^2
Venae cavae: 8 cm^2
Slide 6 (This is the Guyton table, the Lange table on Slide 5 has slightly different #s)
What is normal cardiac output/ flow rate of the circulatory system?
5 L/min
Why do veins have smooth muscle?
Helps maintain tone.
Slide 5
The circulatory system is mainly made up of ______ pathways that gives blood many options of flow.
Parallel
Slide 7
What are the two ways of flow, as discussed in lecture?
- Mechanical (the heart pump)
- Diffusion (the capillaries)
________ govern blood flow through a tissue by responding to capillary secretion of byproducts such as ____, ____, & ____.
Arterioles
Protons (H+), CO2 & Adenosine. (These increase blood flow by causing vasodilation, btw)
Slide 9
Fill in the normal capillary Starling Forces.
A. 30
B. 10
C. 17
D. 28
E. -3
F. Irrelevant ‘some low #’ according to Schmidt.
Slide 10
What are the three main colloids that make up our colloid pressure in order from most abundant to least?
- Albumin
- Globulins
- Fibrinogen
Your patient has an albumin level of 2.6. Is this high or low? What is normal?
What would you expect in your patient?
Albumin level of 2.6 is low.
Normal is 4.5 g/dL
Assuming other colloids and pressures remained normal, you would expect fluid to start leaking out of the vascular space potentially causing edema & hypotension bc your total colloid capillary pressure has dropped.
Slide 11
Why is it so danger-some to have leaky capillaries in the pulmonary circulation?
Because oxygen is not very water soluble and you will start to see gas exchange problems.
Slide 11
This helps create tone in the vasculature and is released by the nervous system.
Norepinephrine!
Slide 15
All vessels have ANS innervation. True or False?
False.
The capillaries do not have innervation or smooth muscle.
Slide 15
“To squeeze or not to squeeze?” That is up to norepi, but what determines how hard to squeeze?
The pressure! Depending on what our pressures are will determine the strength of the squeeze.
Slide 15
This second circulatory system runs parallel with our blood vessels and helps rid our blood of toxins and excess fluid.
Lymphatic System :D
Slide 16
Two-way valves are crucial in preventing backflow in the venous and lymphatic systems. True or False?
False!
“One-Way valves” silly goose.
Slide 16 & 19
What must we consider when giving a paralytic or general sedation and the lymphatic system?
Taking away skeletal muscle contraction - it acts as a pump to drive the lymphatic system.
Slide 16 & 17
Normal lymph flow is __ /day. In healthy specimens, it can increase by how much?
2L/day
20-fold!!!
(Last semester - lymph 120ml/hr = 2-3L day)
Slide 17
Normally, where does the lymphatic system dump?
Subclavian vein.
Slide 16
The lung lymphatic system is not as capable ridding as much fluid as the systemic lymphatic system. True or False?
True!
Slide 16
Pertaining to gravity, for each _____ cm beneath the heart, we must add ___mmHg of pressure.
1.36cm (or 13.6mm)
1 mmHg
Where is the isogravimetric point located? What is another name for it?
Next to the Tricuspid valve.
“Phlebostatic point”
Slide 19 & 20
When standing, what is the normal venous pressure in the lower leg/foot?
+ 90mmHg
Slide 19
Assuming you are standing, why do your venous and arterial pressures increase as you move inferior to your heart?
Gravity, baby!
The higher the column of blood, the higher the pressure - so you should see the highest pressures in your feet.
When standing, what is the normal arterial pressure in the lower leg/foot?
+190 mmHg
(Affects both SBP and DBP)
Slide 19
If this point beneath the subclavian vein is even with the isogravimetric point, why is it +6mmHg and not 0?
Slide 19, Guyton pg. 189
Why are the jugular veins 0 and not negative?
They remain at 0mmHg bc they are collapsed on themselves in the standing person d/t atmospheric pressure. (If cut, they would fall below 0 & collapse even more)
Slide 19, Guyton pg. 189-190
What factors are unique about the sagittal sinuses/veins?
They are rigid (don’t collapse) & have NO one-way valves - this allows the pressure to be negative (especially when we are standing or upright)
Slide 19
Your patient comes in with a hefty skull fracture. What are you worried about as far as pressures in his head?
Because the sagittal sinus is rigid, it wont collapse on itself d/t its negative pressure like the jugular veins would. Instead, there is risk it will create a sucking head wound if exposed to atmospheric pressure and possible air emboli. :(
Slide 19
Why do people pass out after standing still for a long period of time?
When standing still, blood can/will pool in your lower legs/feet because of gravity and no skeletal muscle movement helping return blood to your heart - this eventually decreases your CO and you collapse.
Slide 20
Why is patient positioning so important after you give a paralytic?
We wouldn’t want to pinch any nerves, cause blood pooling/clots, or pressure ulcers in our paralyzed patient.
Slide 20
Describing how much flow blood or air may have is called?
Conductance
Slide 21
What is the formula for conductance and what is it directly proportionate to?
Conductance is proportional to diameter^4.
Slide 21
This is the formula for what?
Distensibility.
Slide 21
Differentiate vascular compliance vs. vascular distensibility.
Distensibility - how compliant or EXPANDABLE something is; takes into account the STARTING volume of the system.
Compliance - the change in volume / change in pressure.
Slide 21
Systemic veins are ___ times more distensible vs. systemic arteries.
8 times!
Slide 21
Capillaries are made of ______ cells and allow ____ based substances, water and _____ through but typically not ______.
Endothelial, lipid, small compounds (glucose, electrolytes), & proteins/colloids.
Slide 22
What is different about the capillaries in the brain vs the systemic circulation?
Less porous, the junctions are tighter and more selective.
(Electrolytes typically are confined in the capillary)
Slide 22
Flow through a tube depends on what?
The pressure gradient.
Slide 23
What is the relationship between Delta P and flow through a capillary?
The higher the Delta P, the faster the flow!
Slide 23
Name and describe the three types of flow discussed in class?
- Turbulent - disorderly, tolerated okay in the healthy.
- Laminar - desired, orderly.
- No flow - lolz.
Slide 24
Laminar flow has differing speeds in the vessel. Explain this further and why.
Laminar flow has a faster flow in the middle of the tube vs a slower speed on the outer bc the blood is hitting the walls of the tube.
Slide 24
What does Reynold’s number describe and what is the formula?
Predicts turbulent flow.
Slide 24
You calculate Reynold’s number for your patient and you get 2000. Does this predict turbulent flow?
YES! >2000 = turbulent
Slide 24
Low velocity with a small diameter creates an opportunity for a lot of turbulent flow. True or False?
False!
HIGH velocity with a LARGE diameter would do this.
Slide 24
What vessel most likely experiences a lot of turbulent flow?
The aorta
Slide 24
Can you have turbulence in your lungs?
Yes! This is what causes increased breath sounds like wheezing or crackles.
Slide 24
You can hear your patients pulse - this is because of what?
Increased turbulence in the vessel.
Slide 24
Why are the slopes different between arterial and venous? What do the slopes equate to?
The slopes are different because each system responds to pressure and volume changes differently.
Slope = compliance
(lower the slope, the more compliant)
Slide 25
Would it be harder to inject saline into a vein or an artery? Why?
An artery, because it is less compliant and has higher pressures.
Slide 25
If we kept the arterial volume constant (700cc) but lost all sympathetic tone, what would happen to the pressure?
It would drop very low. (~40mmHg)
Slide 25
As we move further from the heart, pulse pressure gets higher. True or False?
False!
As we move further from the source of the pressure (heart) we LOSE our pulse pressure.
Slide 31
The _____artery waveform can give us a clean picture of our pulse pressure.
Radial.
Slide 31
As we age, you can expect pulse pressure to _____ because our arteries ______.
Widen, harden.
Slide 31
Does arteriosclerosis tend to affect SBP or DBP more? Does it increase or decrease it?
Hardened arteries tend to increase SBP.
Slide 31
Your patient is diagnosed with aortic regurgitation (leaky valve).
What changes to the DBP would you expect?
And what’s a normal DBP?
You would expect a lower DBP, typically ~40mmHg, bc you are losing volume.
Normal is ~80mmHg.
Slide 31
You’re preparing for a deep spinal anesthesia on your next case. What should you consider and why?
What medication(s) should you have prepped to react to this possible issue?
Hypotension - Losing your sympathetic innervation.
“It shouldn’t go lower than 50mmHg” -Schmidt
You should have Norepinephrine, or some pressor, but it’s best to replace whats missing.
(Remember, nervous system releases NE & NE also helps both your heart & vessels!)
Slide 35
The main controller(s) of BP and what keep it consistent throughout the day.
Baroreceptors!
Slide 36
For baroreceptors, which operate at higher pressures (~20-30mmHg higher) & can act as a ‘backup system’ if pressures get too high?
Aortic or Carotid?
Aortic! They are lower thus gravity creates a higher pressure.
(Notice the aortic curve is shifted to the right)
Slide 36
What part of the “s” wave is most sensitive to changes in pressure?
The middle/steepest incline.
(Pressure increases - firing increases & vic versa.)
Slide 36
What does NTS stand for, where is it located and what does it do?
Nucleus Tractus Solitarius
It’s in the medulla of the brainstem & is the BP control site! 😁
Slide 36
Where on the “s” curve is it least sensitive to changes?
The beginning/bottom & end/top.
Slide 36
The aortic baroreceptors use the ____ nerve & the carotid use _______ & _______ nerves to send impulses to the NTS.
Vagus, Hering’s & Glossopharyngeal
Slide 36
What nerve is the glossopharyngeal?
CN 9 (IX)
Slide 36
What would you expect in your patient if the surgeon clamped both common carotid arteries? Why?
Hypertension!
Your carotid baroreceptors would see lower pressures thus signaled to fire faster increasing your arterial pressures. :O
Slide 37
If your baroreceptors become denervated, what would you expect?
Wide swings in your arterial pressures. :(
Slide 37
List the 4 phases of the cardiac cycle (for this semester).
- Ventricular filling
- Isovolumetric contraction
- Ejection
- Isovolumetric Relaxation
Slide 39 & 40
What does the pressure/volume loop tell us?
Cardiac function/contractility.
Slide 39
Diastolic pressure is also referred to as?
Preload or filling pressure.
Slide 39
Systolic pressure is also referred to as?
Cardiac contractility / function.
Slide 39
What is open during phase I of the cardiac cycle and why?
AV valves bc the pressure in atria is higher than in the ventricle (~2-5).
Slide 40
In the left heart, when the ____ valve closes, Phase II of the cardiac cycle begins and it ends when the _____ valve opens.
Mitral, Aortic
Slide 40
During ejection, or Phase III of the cardiac cycle, approximately how much blood is ejected?
70cc (this is the stroke volume)
Slide 40
What is the normal ESV (end systolic volume)?
EDV (end diastolic volume)?
Passive filling volume?
ESV - 50cc
EDV - 120cc
PFV - 70cc
Slide 40
Which phases in the cardiac cycle are all valves closed?
Phase II and IV.
Isovolumetric contraction and isovolumetric relaxation.
Slide 40
At the end of phase III going into phase IV, how does ejection continue if the pressure is falling?
The ventricles are done squeezing but there is still blood moving through the aorta.
Slide 40
If Phase II weren’t a vertical line but deviated, what would this indicate?
That you are losing or gaining volume from somewhere in the heart.
Slide 40
The pressure outside of the aorta that the ventricle must overcome is referred to as?
What phase of the cardiac cycle begins at this point?
Afterload!
Phase III
Slide 40
In the left heart, at what pressure does the aortic valve close?
Why does it close?
~100mmHg
Aortic pressure > ventricular pressure
Slide 40
What is the BP of the pulmonary circulatory system?
25/8 mmHg
Slide 3
What is a phonocardiogram?
Recording of heart sounds ❤️
Slide 38
What 4 waveforms are on the Carl Wiggers diagram and what is its overall purpose?
Chamber/ aortic pressures, ventricular volume, ECG and phonocardiogram.
This diagram is used to demonstrate the varying pressures in the atria, ventricles and artery during one cardiac cycle.
Slide 38
What is the velocity through the venae cavae?
CSA = 8cm^2
Flow rate = 5L/min
10.4 cm/sec
(*remember to convert to ml and convert mins to secs)
Slide 6 (Guyton Table used for CSA)
What is the formula for resistance?
Change in pressure / flow rate
What is the PRU of the systemic circulation? (Last semester)
1 PRU = (100mmHg - 0mmHg / 100ml/sec)
What is PRU? What is the formula for it? (Last semester)
Peripheral Resistance Unit
Resistance = change in pressure / flow rate
What factors does Poiseuille’s Law include when it comes to flow (Q) through something?
Viscosity (n)
Pressure gradient (Delta P)
Length of vessel (l)
Diameter (r)
Slide 21
