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BP Monitoring

ANP1 Exam 3

BP frequency induction q 1 min maintenance q 2.5 min document q 5 min per ASA
indicator of end-organ perfusion arterial bp
what is a good bp depends on 1. pt baseline, pmh 2. surgical procedure 3. generally w/in 20% of baseline
SBP 1. peak pressure during systolic contraction 2. correlates with changes in myocardial O2 consumption
DBP 1. trough pressure during diastolic relaxation 2. determinant of coronary perfusion
MAP definition 1. time-wt'd avg of arterial pressures during a pulse cycle 2. most useful for assessing organ perfusion
MAP formula SBP + 2(DBP) / 3
pulse pressure difference bw systolic and diastolic pressures
NIBP accuracy depends on 1. proper cuff size 2. positioning (leaned on, tucked, etc) 3. HR (tachy, brady, irreg. ↓ accuracy)
proper NIBP cuff size 1. rubber bladder should be 1/2 way around extremity 2. with 20%-50% > diameter of extremity ~too narrow - over estimate SBP ~too wide - underestimate SBP
don't place NIBP on extremities with PIV or vascular abnormalities (fistulas, mastectomy)
if must place NIBP on arm with PIV place IV tubing underneath cuff to prevent extravasations
SBP by Palpation ~old, unreliable ~no dbp, map ~simple, cheap 1. locate palpable peripheral pulse 2. inflate cuff proximal to pulse til occluded 3. release cuff by 2-3mmHg/beat 4. measure cuff pressure where pulse palpable
SBP by doppler probe ~old 1. same as palpation, except with doppler instead of finger. 2. need lube, accurate position above artery
BP by auscultation 1. inflate cuff to pressure bw sbp, dbp 2. underlying artery partially collapses and produces korotkoff sounds 3. auscultate w/ stethoscope placed under inflated bp cuff 4. SBP = onset of sounds 5. DBP = disappearance of sounds
BP by oscillometry ~preferred ~versatile ~quick ~accurate 1. microprocessor derives SBP, DBP, MAP using an algorithm 2. arterial pulsation causes oscillations in cuff pressure 3. small when cuff > SBP 4. at SBP, markedly ↑ 5. at MAP, maximal 6. after MAP, ↓
BP by plethysmography ~peds ~unreliable w/ ↓ perfusion 1. arterial pulsations transiently ↑ blood vol in extremity 2. finger photoplethysmograph consists of light-emitting diode and photoelectric cell
BP by arterial tonometry ~@ Christ hospital ~freq calibration ~sensitive to movement 1. measures beat to beat pressure 2. senses pressure required to partially flatten a superficial artery supported by bony structure ie radial
NIBP limitations arrythmias
Art Line - Invasive BP monitoring GOLD STANDARD
A line indications 1. elective ↓ bp (to ↓ blood loss) 2. wide intra-op bp swings (pheochromocytoma) 3. end organ disease necessitating beat to beat pressure regulation 4. multiple ABG's 5. 1 lung ventilation 6. cardiac/major vascular surgery 7. strict bp paramet
A line contraindications 1. no collateral blood flow 2. suspicion of pre-existing vascular insufficiency
radial a line ~most common site ~superficial location ~collateral flow (5% lack collateral flow)
test for collateral flow before radial a line insertion 1. doppler probe 2. plethysmography 3. pulse ox (waveform w/ compressed artery) 4. allen's test (not reliable; need pt cooperation)
allen's test 1. exsanguinate hand by pt making fist 2. manually compress radial & ulnar arteries 3. relax hand 4. release pressure over ulnar artery 5. observe return of color < 5 sec = collateral flow 5-10 sec = inconclusive > 10 sec = inadequate circulati
ulnar a line ~more difficult d/t deeper, tortuous ~do NOT attempt if radial has been tried
brachial a line ~large, easily ID'd AC fossa ~less waveform distortion d/t proximity to aorta
femoral a line ~last resort ~prone to pseudoaneurysm & atheroma ~↑ infection & thrombosis ~peds complication: aseptic necrosis of femur head
dp/pt a line ~distorted waveforms d/t distance from aorta
axillary a line ~axillary plexus nerve damage d/t hematoma or traumatic cannulation ~air/thrombi quickly travel to brain during retrograde flusshing of L ax artery
a line complications 1. hematoma 2. bleeding 3. vasospasm 4. arterial thrombosis 5. embolization of air bubbles/thrombi 6. necrosis of skin overlying catheter 7. nerve damage 8. infection 9. loss of digits 10. unintentional intra-arterial drug injection
↑ risk of a line complications 1. prolonged cannulation 2. HLD 3. repeated insertion attempts 4. female 5. CP bypass 6. pressors 7. prolonged shock 8. pre-existing PVD
↓ risks of a line complications by 1. keep ratio of catheter to artery site small 2. heparinized saline at 2-3 ml/hr 3. limit flushing of catheter 4. meticulous attention paid to aseptic technique 5. place pulse ox to monitor perfusion during insertion
a line pressure system frequency 1. must exceed natural frequency of arterial pulse 2. most transducers > 200 Hz 3. stopcocks, air, extra tubing ↓ frequency
a line underdamp leading to overshoot ~ SBP falsely high (overestimated)
a line over damp frequency response too low ~ SBP falsely low (underestimated)
keys to accurate a line waveform 1. minimize tubing length 2. eliminate stopcocks 3. remove air 4. low compliance tubing 5. smaller catheters improve underdamped system & ↓ risk for vascular complications
pressure transducer 1. contains a diaphgram that is distorted by an arterial pressure wave 2. mechanical energy converted to electrical signal
strain gauge principle stretching a wire or silicone crystal changes its electrical resistance ~ pressure transducers based on this
Wheatstone bridge circuit pressure transducer sensing elements arranged so voltage output is proportionate to pressure applied to diaphragm
zero the a line 1. must move with pt 2. check regularly with position, temp changes 3. when pt is seated - brain arterial pressure differs significantly from LV pressure, so level at the ear, which approximates the Circle of Willis
a line waveform upstroke ~contractility 1. faster = ↑ contractility or ↓ SVR 2. slower = ↓ contractility or ↑ SVR
a line waveform downstroke peripheral vascular resistance
a line respiratory variation hypovolemia
a line dichrotic notch ~AV closure ~CO determines position on limb ~↑ = ↑ SV ~↓ = ↓ SV (hypovolemic)
Created by: girlnamedsharon