9. Blood Pressure Monitoring Flashcards
hypotension problems
causes decreased tissue organ perfusion
- stroke, MI, renal failure
postoperative delerium
causes of hypotension (8)
vasodilation
- anesthetic induced
hypovolemia
pt positioning
- head up (reverse trend, beach chair)
vagal response
chronic steroid pts
decreased cardiac contractility/EF
- decr CO
too large BP cuff
lateral decubitus
hypovolemia causes
dehydration/NPO status
blood loss
bowel prep
(reqs 1000-1200mL to replace fluid loss)
hypotension treatments (6)
IV fluids and/or blood products
- volume replacement takes time
vasoconstrictors
- treats anesthetic induced vasodilation
lighten anesthetic
change pts position
- trendelenberg
ionotropes
- improve contractility
stress dose steroids
most common cause of hypotension during surgery
anesthetic induced hypotension
is there any reason to believe low BP isn’t just vasodilation from the anesthetic?
reverse trendelenburg?
high blood loss?
too large BP cuff?
lateral decibutus position?
poor EF?
vagal response after incision?
vasoconstrictors primarily act on
peripheral arterioles
vasoconstrictors mechanism
decr blood flow in peripherals
incr blood flood to vital organs
hypertension problems
LV pumps against greater resistance
incr strain on heart = more O2 consumption
incr strain on cerebral vasculature
–intracerebral hemorrhage and stroke
hypertension etiologies
chronic:
- aging
- poor lifestyle (diet, sedentaty, etc)
Acute:
- pain
- light anesthesia
hypertension treatments
increase depth of anesthesia
narcotics (works if pt is in pain)
vasodilators
blood flow/perfusion and blood pressure
blood flow is proportional to blood pressure
incr BP: incr perfusion
decr BP: decr perfusion
autoregulation of blood flow
ability for an organ to maintain constant blood flow over a wide range of blood pressures
brain
heart
kidneys
cerebral autoregulation range
MAP: 60-160mmHg
renal autoregulation range
MAP: 80-180mmHg
coronary autoregulation range
MAP: 50-120 mmHg
if pt is hypotensive, cerebral blood vessels will
vasodilate
increases cerebral perfusion
if pt is hypertensive, cerebral blood vessels will
vasoconstrict
prevents too much blood flow going to the brain
prevents increase in ICP
cerebral autoregulation curve: Right Shift
chronically hypertensive pts
takes higher than normal BP to keep blood flow to the brain constant
lower autoreg level is higher than normal
renal glomerular filtration rate ceases below what level
MAP 40-50mmHg
what threshold should we keep pt’s BP within during surgery?
20-30% of baseline (preop) MAP value
systolic BP during anesthesia
> 90mmHg
diastolic BP during anesthesia
> 50mmHg
MAP during anesthesia
> 65mmHg
pulse pressure during anesthesia
> 35mmHg
“controlled hypotension”
surgeon request
decreases bleeding at surgical site
caution during “controlled hypotension” requests
sick/chronically hypertensive pts
beach chair position
communicate concerns w/surgeon
If BP falls below autoregulatory range
autoregulation organs receive blood flow, just not as much
If BP rises above autoreg range
autoreg organs receive more blood flow than they should
BF is proportional to blood pressure
autoregulation ability impairement
ischemia
hypercarbia
acidosis
stroke
high end tidal concentration of volatile agent
(>2 MAC)