Hemodynamics Flashcards
If you get systolic pressure variation (with A-line) >10 mmHg with positive pressure ventilation- what does this indicate?
It is an indirect measurement of volume status– consistent with hypovolemia
Femoral artery A-line placement
Palpate femoral artery (VAN- V closest to P), puncture site below inguinal ligament
Relative contraindications to A-line placement
Infection at site, ischemia, raynaud’s, traumatic injury, AV fistula in same extremity, lymphadenectomy, no collateral flow
Radial artery A-line placement positioning
Palm up on flat surface, dorsiflex wrist 30-45 degrees supported with towel (avoid hyper dorsiflexion), tape hand to work surface
What are hemodynamics influenced by?
blood pressure, blood flow, characteristics of blood- poiseuille’s law- (change in pressure * r^4 * pi/ viscosity of blood * vessel length * 8)
Systolic pressure
Max pressure- exerted when heart beats, reflects volume & speed of ejection & compliance of the aorta
Diastolic Pressure
Minimum pressure- exerted in between heart beats, reflects vascular resistance & competence of the aortic valve
Mean Arterial Pressure
Best indicator of tissue perfusion! Average driving pressure of blood during the cardiac cycle.. can use to calculate CPP (Map-ICP)
Pulse Pressure
Systolic - Diastolic, reflects difference in volume ejected from LV into arterial vessels & volume that is already there– function of SV & SVR.. wide PP – increased SV, decreased SVR like in sepsis, narrow PP– decreased SV & increased SVR like in tamponade
Korotkoff sounds
Turbulent blood flow will occur when cuff pressure is greater than diastolic & less than systolic (tapping sounds)
How does an automatic blood pressure monitor work?
Measures MAP (point of max oscillation amplitude) & calculates systolic & diastolic from formulas that examine the rate of change of pressure pulsations– diastolic most unreliable
Blood pressure cuff sizing
Compare length of bladder inside the cuff with the circumference of the patients arm- bladder at least 80% reading should be accurate
Shape of A-line waveform depends on?
Force generated by ventricle, speed of ejection, compliance of arterial vessels, rate of forward blood runoff (SVR)
Oscillations after fast flush of A-line
2 oscillations occur after fast flush- should be no more than 1/3rd of previous oscillation.. just one flush- have overdampening, “ringing” or repeated- underdampening
A-line complications
Ischemia, pseudoaneurysm, hemorrhage, hematoma, embolism, local infection, sepsis, neuropathy, misinterpretation of data
Effect of patient positioning on NIBP
NIBP will be higher in the dependent arm (if patient on side- the lower arm) and lower in the nondependent arm
CVP monitoring- indications, normal
Indication of preload of RV: low with tachycardia and hypotension usually is hypovolemic, high with hypotension indicative of myocardial congestion (MI, tamponade, tension pneumo).. normal is 6-10 mmHg
Prior to insertion of PA catheter what needs to be done?
Flush all lumens, check integrity of balloon with PASSIVE deflation, prepare transducer, connect lines to appropriate lumens (PA distal, CVP proximal)
PA catheter insertion
Insert to depth of 20 cm, CVP waveform identified, inflate balloon to carry through RA, RV & into PA)
Normal PA pressures
Systolic: 15-30/ Diastolic: 5-15 (mmHg)
Normal PACWP
4-14 mmHg
Complications of CVP & PA lines
Infection, pneumo, vessel erosion/perforation, venous air embolism, hemorrhage, rupture of PA, dysrhythmias
LiDCO
Lithium dilution cardiac output, minimally invasive way of monitoring continuous CO
What does EKG monitor
Electrical impulses (HR, arrhythmias, ischemia, pacemaker function, electrolytes) NOT contractility/output – think of PEA
How does EKG monitoring work
Silver chloride electrodes have conductive gel which decreases electrical resistance of skin, small signal amplified and broadcasted
Lead II function
Rhythm detection- inferior portion of heart (RCA)
Lead V5 function
Left ventricle (LAD)- placed 5th intercostal space anterior axillary line
Lead I function
Circumflex artery monitoring
Respiratory impedance monitoring
Measures movement of chest by electrodes- not fool proof
Pulse oximetry monitoring
Measurement of arterial hemoglobin oxygenation- measures pulsatile signals across perfused tissue at 2 discrete wavelengths (absorbance of light indicates state of hemoglobin)
What are the 2 light emitting diodes in pulse oximetry
Infrared (940 nm wavelength-oxyhemoglobin) Red (660 nm wavelength - reduced hemoglobin)
Carboxyhemoglobin appearance
Just like oxyhemoglobin- false high
Methemoglobin appearance
Gives saturation of 85% regardless of true oxygenation
