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BP Monitoring
ANP1 Exam 3
| Question | Answer |
|---|---|
| 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
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