Hemodynamic Monitoring Flashcards
1
Q
Goals of the CV System
A
- deliver oxygen and nutrients
- remove waste
2
Q
Hemodynamics
A
- mvmt of blood through the closed circulatory system
influenced by:
- BP
- blood flow
- characteristics of blood (viscosity, hydration, etc)
3
Q
MAP Formula
A
MAP = CO x SVR
CO = HR x SV
4
Q
Blood Flow Formula
A
5
Q
Systolic Pressure
A
- max pressure
- pressure exerted when heart beats (systole)
- reflects volume and speed of ejection and compliance of the aorta
6
Q
Diastolic Pressure
A
- minimum pressure
- pressure exerted in between heart beats
- reflects vascular resistance and compentence of the aortic valve
7
Q
Circle of Life Visual
A
8
Q
MAP
A
- best indicator of tissue perfusion!
- average driving pressure of blood during the cardiac cycle
- MAP used to titrate pressures for induced hypotension or calculation of CPP
9
Q
Pulse Pressure
A
PP = SBP - DBP
- reflects difference in volume ejected from LV into arterial vessels and volume that is already there
- function of SV and SVR
10
Q
Widened PP
A
- increased SV and decreased SVR
- sepsis
11
Q
Narrow PP
A
- decreased SV and increased SVR
- atherosclerosis
12
Q
Arterial Pressure Monitoring
A
NIBP: auscultation or automatic (oscillometric)
Art Line: continuous pressure transduction
13
Q
Auscultation
A
- normal laminar flow in arteries produces little vibration and no sound
- when artery is constricted, blood flow becomes turbulent causing the artery to vibrate and produce sounds
14
Q
Karotkoff Sounds
A
- turbulent flow that occurs when cuff pressure is >diastolic and <systolic></systolic>
<p>- tapping sounds associated w turbulent flow</p>
<p> </p>
</systolic>
15
Q
Automatic Oscillometric Approach
A
- even when sounds are barely audible, the oscillometric method can pick up the vibrations
16
Q
Automatic BP Monitoring
A
- measures oscillations in machine umbilical cable
- measures MAP (point of max oscillation amplitude) and calculates SBP and DBP from formulas that examine the rate of change of the pressure pulsations
- SBP identified as the pressure at which the pulsations are increasing and are at 25% to 50% of max
- DBP is the most unreliable measurement and is recorded when the pulse amplitude has decreased to a small fraction of its peak value
17
Q
Comparison of BP Measurements Between Korotkoff Sounds and Oscillometry (Visual)
A
18
Q
Limitations of Oscillometric Measurement
A
- Motion artifact
- Bruising at cuff site
- Nerve damage
- Arterial or intravenous occlusion during inflation.
- If proximal to pulse oximeter, damping of pulse ox waveform and reading
- If SBP below 80, NIBP often over estimates MAP.
- Must have correct cuff size
- Dysrhythmias make values difficult to interpret or increase cycle time.
19
Q
BP Cuff Sizing
A
- ensure bladder length is 80% of arm circumference
20
Q
Troubleshooting Automatic NIBP
A
- air leaks at cuff, tubing, or connection to unit
- pt must keep arm still
- disconnect and reconnect to reset
- most default to q5 min, increase to q2.5 min for induction
21
Q
Invasive Arterial BP Monitoring
A
• Most accurate way to monitor beat to beat blood pressure and easy access to blood gas monitoring.
– Hemodynamic instability or predicted instability.
– Surgical procedure with anticipated significant blood loss or fluid shifts
– Monitoring of induced hypotension
– Monitoring response to vasoactive drugs
– NIBP is not feasible (burns, obese, shock)
– Repeated blood sampling
22
Q
Invasive Art Line Waveform
A
- shape depends on force generated by ventricle
- speed of ejection
- compliance of arterial vessels
- rate of forward blood runoff (dependent on resistance to forward flow or SVR)
23
Q
Troubleshooting Pressure Monitoring System
A
- keep it simple: minimize stopcocks, long tubing
- remove air bubbles
- zero line to midaxillary or phlebostatic axis (RA)
24
Q
Location of Phlebostatic Axis
A
- 4th intercostal space midaxillary line
- location of RA, where the tip of a CVP would lie
- if below, BP will be erroneously high
- if above, BP will be erroneously low
25
Pressure Transducers: Normal vs Dampened/Overdampened (Visual)
26
Art Line Complications
* Distal ischemia, pseudoaneurysm
* Hemorrhage, hematoma
* Aterial embolization
* Local infection, sepsis
* Peripheral neuropathy
* Misinterpretation of data
27
Systolic Pressure Variation
- mechanical ventilation
- pulsus paradoxus is \>10mmHg
***- normally doesn't exceed 10mmHg***
28
Pulse Pressure Variation
- normal should not exceed 13%
- (PPV) = (PPmax – PPmin) / PPmean
29
CVP Monitoring
- indication of RVEDV or Preload (fluid status)
**- normal 6-10**
• If abnormal, collect venous blood oxygenation samples
– Global tissue perfusion and oxygenation
30
High CVP
- persistant hypotension following fluid bolus and high CVP = myocardial congestion (MI, tamponade, tension pneumo)
31
Low CVP
low CVP, tachycardia, and hypotension = hypovolemia
32
CVP Catheter Types
- single lumen: rapid, high volume resuscitation or pressure monitoring
- multi lumen: drug therapy, nutrition support, pressure monitoring
33
CVP Waveform
* a -‐ atrial contraction, absent in a fib, larger in tricuspid stenosis, pulmonary stenosis and pulmonary HTN
* c – due to bulging of tricuspid valve into RA
* x -‐ atrial relaxation
* v -‐ rise in arterial P before tricuspid valve opens
* y -‐ atrial emptying as blood enters ventricle
34
CVP Waveform (Visual #2)
35
Pulmonary Artery Pressure Monitoring
• Better indicator of left heart pressure than CVP, especially when:
– LV function is impaired
– Significant valvular disease
– Pulmonary HTN
**• PCWP** – Best estimation of LVEDV (left V preload)
**• CO** – Thermodilution
**• SVO2** (mixed venous oxygen saturation)
– Evaluate oxygen consumption and delivery
36
PA Catheters
- multi-lumen polyvinylchloride catheter w balloon at tip
- inflation of balloon ensures that blood flow will move balloon/catheter forward in the direction of blood flow
37
Insertion of PA Catheter
- R heart catheterization w large bore introducer sheath
- typically via subclavian or IJ veins
- seldinger technique (introducer then guidewire then catheter over wire)
38
Prior to Insertion of PA Catheter
* Flush all lumens with solution
* Check integrity of balloon
– Always deflate passively
* Prepare transducer system that has been leveled and zeroed.
* Connect lines to appropriate lumens
– PA pressure monitor is distal
– CVP pressure monitor is proximal
39
Catheter Insertion
* PA catheter is inserted to a depth of 20cm.
* A CVP waveform must be idenAfied to confirm that the PAC type is in the R vena cava or atrium.
* Balloon then fully inflated, blood will carry or float the catheter through the RA, RV and into the PA.
40
Progression of PA Catheter (Visual)
41
PA Catheter Measures
Systolic: 15-30 mmHg
Diastolic: 5-15
PACWP: 4-14
42
Thermodilution CO
- cold water injected through PA catheter and the change in temp from proximal to distal ends of catheter is measured and analyzed against time
- thermistor tip
43
Complications of CVP and PA Lines
* Infection
* Pneumothorax
* Vessel erosion or perforation
* Venous air embolism
* Hemorrhage (rupture of PA)
* Cardiac dysrhythmias
44
LiDCO
- lithium dilution cardiac output
- minimally invasive **continuous** CO monitoring
• Uses the pulse pressure analysis algorithm for continuous measurement of changes in CO
– Derive SV from arterial pressure waveform
– Calculate HR
– CO = SV\*HR
– calibration
• Provides info on SV variation and pulse pressure variation
45
EKG
• Monitors electrical impulses through the heart
– HR
– Arrhythmias
– Myocardial ischemia
– Pacemaker function
– Electrolyte abnormalities
– NOT contractility or output! (PEA)
46
How does EKG monitoring work?
* Silver chloride electrode with a conductive gel which decreases the electrical resistance of the skin.
* A very small electrical signal is amplified and then broadcasted over a 0.01 to 250 Hz bandwidth.
* Prone to electrical interference
– Clean dry skin
47
EKG Lead Placement
**• Lead II** – Rhythm detection
– P waves
– Inferior portion of the heart supplied by the RCA
**• Lead V5** – Bulk of the LV supplied by LAD placed 5th intercostal space anterior axillary line
**• Lead I** – Circumflex artery
48
Respiratory Impedence of EKG
* Impedance pnuemography
* In short, measures movement of the chest electrodes.
* Anesthesia monitors do not default to show this, but helpful with sedation cases.
49
Pulse Oximetry
- measurement of arterial Hgb oxygenation
- oxygenation and deoxygenated blood absorb light differently
oxyHgb: infrared, 940nm wavelength
REDuced Hgb: red, 660 nm
50
Pulse Ox: Beer-Lambert Law
* Measure “pulsatile signals across perfused tissue at two discrete wavelengths”
* Absorbance of light indicates state of hemoglobin
* Two Light Emi|ng Diodes (LEDs)
– Infrared (940 nm wave length) – oxyhemoglobin
– Red (660 nm wave length) -‐ REDuced hemoglobin
• Light detector
51
Light Absorbance Visual
52
Carboxyhemoglobin
- CO poison
- appears like oxyHgb at 660 nm
- raises appearance of oxygenated Hgb
- falsely HIGH readings
53
Methemoglobin
- benzocaine, methylene blue
- gives a sat of 85% no matter what the true oxygenation is
54
