Blood Pressure Monitoring Flashcards
in most organs does the blood flow/perfusion increase or decrease with increased BP?
increase
and decreases blood flow as BP decreases
what organs autoregulate their blood flow?
brain
kidney
heart
autoregulation of blood flow definition
the amount of blood flow/perfusion to these organs remains CONSTANT despite changes in BP (within autoreguation range)
proposed cerebral autoregulation ranges
60-160mmHg
If the BP in the brain goes above 160mmHg what happens to blood flow to the brain?
increases
If the BP in the brain goes below range (50-60) what happens to blood flow to the brain?
decreases
What happens to the autoregulation curve in a chronically hypertensive patient?
the curve is shifted to the right
What does an autoregulation curve shifted to the right mean for BP maintenance?
It means that the blood flow to the brain will decrease at a higher MAP than a healthy patient
What is the renal autoregulation range?
80-180mmHg
What is the coronary autoregulation range?
50-120mmHg
What do the local blood vessels that supply autoregulation organs do during hypotension or hypertension?
adjust their tone
example: cerebral hypotensive: vasodilate and increase perfusion
cerebral hypertensive: vasoconstrict and prevents over perfusion
What does preventing over perfusion to the brain do?
prevents increase in intracranial pressure
reduces the risk of brain injury
What happens if the MAP falls below autoregulatory range?
still receive blood flow but not as much
amount of blood flow of autoreg organs will be proportional to the BP
What happens if the MAP rises above the autoregulatory range?
will receive more blood flow than they should
amount of blood flow of autoreg organs will be proportional to the patients BP
When can autoregulation ability be impaired (4)?
ischemia
hypercarbia
acidosis
high end tidal concentration of volatile agent
During anesthesia what should the anesthetist try to keep the patients BP within?
20-30% of their baseline BP value
If a patient has a starting BP of 185/105 with MAP= 132; what should you not let the MAP fall below?
92mmHg MAP (30% below)
What is controlled hypotension?
when surgeons ask for hypotension on purpose to decrease bleeding at the surgical site and improve the view through a scope
what cautions should an anesthetist take during controlled hypotension (3)?
- dont allow as much hypotension in ill or chronic hypertensive pts
- don’t allow the same amount of hypotension if the patient is in beach chair postion
- communicate concerns with surgeon
what are the etiologies (causes) of hypotension (8)?
1- hypovolemia (NPO, blood loss) 2- vasodilation (anesthetics, sepsis) 3- patient positioning 4- vagal response 5- need for stress dose of steriods 6- decreased cardiac contractility/EF (lower CO) 7- BP cuff too large 8- lateral decubitus (depends on the arm you put it on)
Patients undergoing intestinal surgery will usually have to do what?
bowel prep
requires 1000-1200mL to replace this fluid
treatments for hypotension (5)?
1- vasoconstriction (phenylephrine or lower volatile agent)
2- increase intravascular volume (if hypovolemic: LR, N/S, albumin, blood)
3- change pt position
4- administer inotropes (if heart failure: epi)
5- stress dose of steroids (chronic steroid use)
What are the 5 types of BP measurement?
auscultation doppler (systolic only) NIBP (oscillometry; cuff) Noninvasive arterial line (tonometry) arterial line
other name for auscultation
sphygmomanometry
laminar defintion
(of a flow) taking place along constant streamlines; not turbulent.
korotkoff sound
the sounds you hear when taking a BP with auscultation
When do you hear and not hear the korotkoff sounds?
korotkoff sounds disappear when artery is completely compressed (no blood flow)
korotkoff sounds appear when partially compressed (blood flow turbulent)
korotkoff sounds disappear when artery is completely open (blood flow is laminar)
what are the systolic and diastolic BPs in terms of korotkoff sounds?
systolic (appearance of korotkoff sounds)
diastolic (disappearance of korotkoff sounds)
when the BP cuff is inflated to a pressure above systolic what is the pulse amplitude?
low bc artery is compressed and no blood flow
when the BP cuff starts to deflate and the pressure in the cuff matches the systolic pressure what is the pulse amplitude?
starts to increase and the pulse is felt b/c the artery is less compressed
when the BP cuff deflates to the point of MAP what is the pulse amplitude
the pulse amplitude is at its maximum
when the BP cuff is deflated to diastolic pressure and below what is the pulse amplitude?
the pulse amplitude is small again and cannot be felt
Does the NIBP calculate the MAP from the systolic and diastolic?
no it measures the MAP separately
Is oscillometry equally as accurate with regular and irregular rhythms?
no irregular rhythms cause it to be more inaccurate
In order to get an accurate reading how much greater should the width of the cuff be than the diameter of extremity
20-50%
If the cuff is too large will the BP be an overestimation or underestimation?
underestimation
it must squeeze harder in order to flatten artery
if the cuff is too small will the BP be an overestimation or underestimation?
overestimation
what is the difference between the systolic pressure in the arm vs. leg in supine patient
10-20mmHg greater in the legs
what is the difference between diastolic pressure in the arm vs. leg in supine patient
- some sources say equal
- some sources say equal to or lower than arm
MAP in arm vs leg in supine patient
leg MAP is higher
increase in systolic was greater than decrease in diastolic
is the NIBP accurate when you cannot feel a distal pulse or the extremities are cold?
no
do different sites on the body give you different BPs? why is this important?
yes
important b/c blood flow to an extremity can be compromised and we need an accurate BP
What would happen if the surgeon was leaning on the BP cuff?
overestimated BP
important to make sure reading is accurate before treating
Where should you not place the BP cuff (3)?
1- operative arm
2- same side as mastectomy or lymph node removal (lymphedema)
3- arm with AV fistula
AV fistula
artificial connection between artery and vein (vein gets big) allows for dialysis in renal failure patients
Non-invasive A line (tonometry)
gives a beat to beat BP by placing probe over wrist
senses the pressure required to flatten artery
disadvantages of non-invasive a lines (4)
sensitive to movement
sensitive to placement
needs frequent calibration
no arterial access for labs
dialysis
excess waste and fluid is removed from the blood in patients with renal failure
what are the two types of dialysis
hemodialysis (HD) peritoneal dialysis (PD)
process of HD (3)
1- large vein and artery are accessed (via AV fistula, graft or central line)
2- machine draws blood from artery
3- machine purifies and returns via vein
What type of anesthesia does a person getting a AV fistula?
MAC anesthesia
AV graft
artificial tube that connects the artery to the vein
when is an AV graft indicated?
the patients blood vessels are too small to create a fistula
AV graft advantage
mature faster than fistulas
AV graft disadvantage
more likely to clot
infxn more likely
central line for dialysis
short term solution until fistula or graft created
double lumen
peritoneal dialysis
dialysis solution is infused into the peritoneal cavity, waste diffuses and then solution is drained
anesthetic management for renal failure (3)
1-pt usually anemic (decreased EPO)
2- restrict fluids as much as possible (500mL on microdrip)
3- cautious of any increase in serum potassium (LR or Sux)
if the patient is not supine what effects the BP?
gravity
NIBP cuff is placed higher on a reverse trendelenburg will the BP be higher or lower?
lower
In lateral decubitus position the BP reading on the dependent arm will be over or under estimated?
over estimated
how can BP in the head be estimated in non supine positions?
1- measure distance from cuff to head
2- calculate the difference in BP at level of head
For each 1cm in height difference the MAP will be how much lower at the head??
0.77mmHg
