Patient Monitoring Flashcards
what is electrocardiogram (EKG or ECG) used for
used to monitor electrical activity as it travels through the myocardium of the heart sensed by electrodes on the skin
what can be diagnosed through EKG (4)
- dysrhythmias such as VFIB, AFIB, VTACH, bradycardia
- myocardial ischemia: ST changes, new T-wave changes
- conduction defects: AV blocks
- electrolyte disturbances: K+, CA++
cardiac conduction (electrical activity) results in
mechanical beating of the heart
what is mechanical beating created by
created by electrical impulses moving throughout the conduction system
Specific waves that appear on an ECG correspond both to the _____ and the _____ of a particular area of the heart
both to the mechanical and the electrical depolarization/repolarization of a particular area of the heart
what is the 5 electrode system
all but the posterior wall of the myocardium can be monitored for ischemia
- 1 electrode on each extremity and 1 precordial (chest) lead (v5)
what is v5 electrode best for
for monitoring the LV
in patients with coronary artery disease, the ______ is best single lead for diagnosing ______
the v5 lead is the best single lead in diagnosing myocardial ischemia
___% of ischemia episodes will be detected by EKG if leads __ and __ are analyzed simultaneously
90% leads II (white) and V (brown)
what does the P wave represent
depolarization of atria in response to SA node triggering
what does the PR interval represent
delay of AV node to allow filling of ventricals
what does the QRS complex represent
depolarization of ventricles
triggers main pumping contractions
what does the ST segment represent
Beginning of ventricle repolarization
should be flat
what does the T wave represent
ventricular repolarization
after the SA node fires, the depolarization wave passes through the right and left atria, stimulating ____ and producing the _____
stimulating the atrial contraction and producing the P wave
what does the AV node help with
- only normal conduction pathway between atria and ventricle
- slows impulse conduction to allow time for the atria to contract and blood to be pumped from atria to ventricles
Conduction time through he AV node accounts for most of the duration of the _____
PR interval
what does the Q wave represent
-impulse passing through the Purkinje fibers coming from the right and left branches of the Bundle of His
what follows the QRS complex
the plateau phase (ST segment)
what produces the T wave
ventricle repolarization
takes place slowly, generating a wide wave
what is an important characteristic in determining a normal heart rhythm
time
what are the 4 key intervals in particular that aid in the interpretation of ECGs
- PR interval
- QRS interval
- QT interval
- RR interval
- PQRS complex
the normal time for PR interval
120-200 ms
if the PR interval is > 200 ms
1st degree heart block
delayed conduction through the AV node
if the PR interval is <200 ms
suggest pre excitation
-presence of an accessory pathway between the atria and ventricles
normal time for QRS interval
60-100 ms
prolonged QRS indicates
hyperemia or bundle branch block
increased amplitude of QRS indicates
cardiac hypertrophy
when do pathologic Q waves occur
when the electrical signal passes through stunned or scarred heart muscle
-markers of previous myocardial infarctions
normal time for QT interval
350-430 ms
prolonged QT time
> 440 ms
-at risk for ventricular tachyarrhythmias & hypocalcemia
short QT time
< 350 ms
genetic disorder, hypercalcemia
RR interval represents
1 cardiac cycle
PQRST complex normal time
60 ms
(PR + QT) = 0.6 s
how is external measurement of blood pressure normally done
normally via the cuff on the brachial artery
too small of a cuff can cause
false high readings
too big of a cuff can cause
false low readings
non invasive blood pressure is ____ for monitoring hemodynamic parameters during cardiac surgical procedures
inadequate
what causes non invasive blood pressure to be inadequate for cardiac surgery
- inaccurate
- intermittent data
- requirements for pulsatile flow: this method cannot be used during non-pulsatile flow
what does the strain gauge transducer measure
strain on the sensor
what does the strain gauge transducer use to convert measurement
Wheatstone bridge
what does the strain gauge transduce convert via the Wheatstone bridge
converts measurement of strain to resistance
resistance is then converted to pressure
intravascular pressure monitoring is done via
direct cannulation of artery with a small catheter
-also used for arterial blood sampling site
systolic pressure _____ from ___ to _____
systolic pressure increases from ascending aorta to peripheral arteries
what is an important difference between intravascular pressure monitoring and non invasive pressure monitoring
real time pressure readings
what are some complications of intravascular pressure monitoring
infection, ischemia, aneurysm, cerebral embolism
what are the 3 major changes that occur in the arterial pulse contour as the pressure wave travels distally
- systolic portions of the pressure wave become narrowed and elevated
- high-frequency components on the pulse are damped out and soon disappear
- hump may appear on the diastolic portion of the pressure wave
what is ABP and what is it used for
stands for arterial blood pressure
use to monitor for patient instability, monitor arterial blood gases, direct monitoring even during nonpulsatile flow states
where is the ABP catheter placed
in the right or left radial artery prior to induction of anesthesia
what is the test to check and see if the radial artery can be used for the ABP catheter
allen test
if the capillary refill is greater than 15 seconds, should not be used
where else can the ABP be placed if radial artery can not be used
- femoral artery
- aorta (not an option at beginning of case, but can be accessed after chest is open to verify ABP)
- axillary artery: risk for debris embolus if on right side, safer on left
- brachial artery: should be avoided to prevent thromboembolism
- ulnar artery: only used if radial can’t be entered
- pedal artery: rarely used
HR can be determined from
ABP
pulse pressure
difference between systolic and diastolic pressure
-provides useful info on volume status and valvular competence
what has a narrowed pulse pressure
pericardial tamponade
hypovolemia
a sudden increase in pulse pressure may be a sign of
worsening AI
stroke volume can be estimated from
area under the aortic pressure wave from onset of systole to diacritic notch
the high position of the diacrotic not on the downslope trace gives an estimate of
high vascular resistance
low resistance tends to cause a diacritic notch to be
lower on the diastolic portion of the pressure tracing
what is overdamping
underestimates SBP, overestimated DBP
causes of overdamping
- kinking of arterial catheter or tubing
- occlusion: air or clot in catheter or tubing
- loss of flush pressure
- transducer failure
- soft compliant tubing
under damping
overestimates SBP, underestimates, DBP
causes of underdamping
- long stiff tubing
2. increased SVR
if a transducer is at the height at the level of the right atrium
zero transfer open to air
if the transducer is lower then the level of the right atrium
falsely high BP
if the transducer is high than the level of the right atrium
falsely low BP
complications of arterial catheters
- ischemia
- thrombosis
- infection
- bleeding
- false lowering of radial pressure immediately after CPB (vasospasm)
central venous pressure is a measure of
right atrial pressure
what is CVP used for
to monitor preload and to transfuse large volumes of fluids
what is CVP affected by
- blood volume
- venous tone
- RV function
CVP wave goes…..
a c x v y
a wave
atrial contraction
c wave
QRS and bulging of tricuspid valve into RA
x deflection
tricuspid valve pulled downward during late systole into RV
v wave
back pressure wave from right atrial filling
y descent
tricuspid valve opens and atrium empties into ventricle: early diastole
pros and cons of central venous pressure
pros: reasonable indicator of LV function in the absence of pulmonary hypertension and mitral valve disease, can measure coronary sinus pressure
cons: ventilator PEEP may falsely elevate CVP measurement
complications of CVP
dysrhythmias, pneumothorax, infection, carotid artery puncture, air embolism
what kind of catheter is used for a pulmonary artery catheter
Swan-ganz catheter
what is pulmonary artery catheter used for
- assessment of cardiac function and volume status
- access for cardiac pacing
- access for mixed venous blood sample
indications for use of pulmonary artery catheter
LV dysfunction, LM lesion, PA HTN, Recent MI, valvular lesion, sepsis, organ failure, major blood loss, aortic crossclamp
where is the insertion site for a pulmonary artery catheter
right internal jugular vein preferred, otherwise left IJK
reasons to not use pulmonary artery catheter
- mechanical right heart valve
- right ventricle assist device
- left bundle branch block
complications with using pulmonary artery catheter
- dysrhythmias
- PA rupture
- right bundle branch block
- valve damage
- thrombus
- balloon rupture
- infection
PA pressure is / of arterial pressure
1/3
if mean or systolic PAP is greater than 1/3 of the mean or systolic arterial pressure, the patient has
pulmonary hypertension
what 6 things does the PA catheter measure
- pulmonary artery pressure (PAP)
- pulmonary capillary wedge pressure (PCWP)
- central venous pressure (CVP)
- mixed venous oxygen saturation: SvO2
- cardiac output (CO)
- blood temperature
main indication for PA catheter
to monitor the LV and RV separately
what can the PA catheter help detect
- access volume status
- diagnosing LV failure by PAP and PCWP
- diagnosing RV failure
- diagnosing pulmonary hypertension
- assessing valvular disease
what are hallmarks of LV failure
high PAP and PCWP in the presence of systemic hypotension and low CO
what is blood temperature measure by off of the PA catheter
thermistor port
thermistor temp reflects core temp
what are the ports off of the PA catheter
- thermistor port
- proximal port
- distal port
- RA infusion port
- balloon inflation port
prior to CPB, how should the baseline blood gas be measured
non-heprainized blood must be in a heparinized syringe
on CPB, when should the blood gas be measured
within 10 min of initiation
and at least every 30 min after
what must you do to maintain anaerobic conditions
expel air bubbles and cap syringe
gas equilibration between air and blood will lead to
- decreased PaCO2
- increased PaO2
normal pH blood gas
7.35-7.45
normal PaO2 blood gas (partial pressure of O2)
80-100 mmHg
normal PaCO2 blood gas (partial pressure of CO2)
35-45 mmHg
normal HCO2 blood gas (bicarbonate level)
21-27 mEq/L
normal SaO2 blood gas (oxygen sat)
95-100%
normal FiO2 blood gas (fraction of inspired oxygen)
21%
what is used routinely to identify instant changes in a patients status
trending devices
how often should trending devices be calibrated for accuracy
each case
does trending devices replace the need for routine blood gas>
no
what does pulse oximetry montor?
non invasive way of measuring arterial oxygen saturation (SaO2)
how does pulse oximetry work
red and infrared light absorbency read by photodetector on opposite end
explain Beer’s law
amount of light absorbed is proportional to the concentration of the light absorbing substance
what does pulse oximetry not differentiate and what will be falsely read
does not differentiate between COhB and O2Hb
-falsely elevated readings will be seen in heavy smokers and patients with CO exposure
what must you have for an accurate and reliable pulse oximetry reading
a pulse
what does a low tone in pulse oximetry reading indicate
low oxygen saturation
beep rate indicates
HR
problems/ things that pulse oximetry cannot read that well or give false readings on
- anemia: tissues can suffer hypoxia despite high oxygen saturation in the blood that does arrive
- carbon monoxide not differentiated from oxygen bound to hemoglobin therefore high reading may occur despite the pt being hypoexmic
- low flow
- dark skin pigmentation can overestimate readings
- methemoglobinemia cause readings in the mid-80s, cannot bind oxygen
large quantities of MetHb greater than 10% may rising in what
SpO2 reading of about 85%
during cardiac surgery, a pt is at increased risk for adverse neurological effects during surgery due to CPB because of ______ and _____, as well as potential risk of ______.
pt is at increased risk for adverse neurological events during surgery due to CPB because of core cooling and changes in blood flow, as well as potential risk of emboli
what are 3 main reasons to monitor CNS
- diagnose cerebral ischemia
- assess depth of anesthesia
- assess effectiveness of neuroprotective medications
what are the monitors used to watch CNS electrical activity
- electroencephalogram (EEG)
- processed EEG
- evoked potentials
what are monitors of cerebral metabolic functions
- jugular bulb venous oximetry
2. NIRS
what does jugular bulb venous oximetry measure
measure mixed venous blood saturation of blood leaving the brain
what does NIRS stand for and
near-infrared spectroscopy
what are monitors for CNS hemodynamics
- transcranial doppler (TCD)
2. MetaOx
what does transcranial doppler (TCD) use
uses ultrasonic waves to measure the velocity of blood flow in the brain vessels
-can detect emboli in cerebral circulation
what does MetaOx measure
measures an index of blood flow using DCS (diffuse correlation spectroscopy)
EEG is used to
- guide seizure measurement
- assess level of consciousness
- detect cerebral ischemia
- monitor effects of medications
EEG signs (3)
status epilepticus
burst suppression
brain death
what is status epileptics on EEG
spike in amplitude
what is burst suppression on EEG
sign of anoxic brain injury to can be induced with medication
what does brain death show on EEg
cessation of any activity on EEG
what are the five frequency bands on EEG
delta theta alpha beta gamma mu
what is near infrared spectroscopy
trending device used to detect the regional oxygen saturation of brain tissue
what does near infrared spectroscopy measure
continuous, non invasive measurement of regional cerebral tissue oxygen saturation (SctO2)
where is near infrared spectroscopy sensors placed
about pt’s brows
for near infrared spectroscopy, increased ____ levels will increase values due to an _______
increased pCO2 levels will increase values due to an increase on cerebral blood flow
for near infrared spectroscopy, decrease in _____ will _____
decrease in body temperature will increase the values due to reductions in CMRO2
target and threshold values for cerebral oximetry are mostly dependent on what
upon patient’s baseline value
what is the typical rSO2 range
60-80 in adults
40-60 in neonates
intervention trigger for cerebral oximetry
<50 or 20% decrease for baseline
critical threshold for cerebral oximetry
<45 or 25% decrease from baseline
Bispectral index measures
depth of anesthesia and state of hypnosis by analyzing data from the EEG to measure level of sedation
why measure BIS
prevent patient awareness during surgery
what is the goal value for BIS during surgery
40-60
90-100 awake patient
0 - electrical silence and absence of brain activity
what is the correction dosage to maintain sedation
isoflurane on >0.6% on CPB is thought to be sufficient to maintain sedation
increase in mean cerebral blood flow indicates what
vasospasm
decrease in mean cerebral blood flow indicates what
impending or completed stroke
what are the positions of the 4 transducer position windows
- transtemporal
- transorbital
- suboccipital
- submandibular
why do you monitor renal function during CPB
renal failure after CPB occurs 2.5-3.1% of the time
-CPB presents an abnormal physiological state of non pulsatile flow which affects renal autoregulation
what is the diuretics used in CPB prim
mannitol
what are the 2 reasons to use mannitol during CPB
- hemolysis: urine output should be maintained to avoid damage to renal tubules
- deliberate hemodilution: maintenance of good urine output during and after CPB allows removal of excess free water
what is an adequate amount of urine output?
- 5 to 1.0 ml/kg/hr
- does not mean that no kidney damage has occurred
- does show that you have blood flow to kidney
what are serum electrolytes that should be checked toward the end and after CPB
K+
Mg2+
Ca2+
what can low ca2+ cause
poor myocardial contractility
when do you admin calcium
15-20 min after the cross clamp is removed and acceptable perfusion to the brain is established or could cause worsen neurologic outcome
what can low Ca2+ affect
coagulation
what can high K+ affect
electrical conduction
what does core temperature represent
temperature of the vital organs
where are the temperature monitoring sites
- esophageal
- PA catheter
- nasopharyngeal
- tympanic
- bladder
what is the accurate reflection of brain temp on CPB
nasopharyngeal
what is the best indicator of core temperature when pulmonary blood flow is present (pre and post CPB)
PA catheter thermistor
what is shell temp
majority of body (muscle, fat, bone)
-receives smaller portions of blood flow which can affect temp fluxes
when does the shell temp lag behind the core temp
during cooling and rewarming
what does the shell temp include
rectal and skin temp
myocardial temperature is the best indicator of what
cardioplegia delivery temp
recommendations for temperature monitoring on CPM
monitor 2 sites: a core and a shell site
monitor arterial and venous line temps
normothermic
> 34
mild hypothermia
28-34, <10 min arrest
moderate hypothermia
20-28
10-19 min arrest
deep hypothermia
14-20
20-45 min arrest
profound hypothermia
<14
46-65 min arrest
during cooling and rewarming what is the temp gradient and between what
8-10 C temperature gradient between patient temp and heat exchanger water source
warm normothermic cardioplegia temp causes
increase O2 delivery
less time in between doses
cold cardioplegia temperature (around 9 C) causes what
decreased O2 demand by cooling myocardium, more time in between doses, platelet activation
an echocardiogram (echo) uses
ultrasound to create pictures of your heart’s movement
a trans esophageal echo (TEE) test is…
a type of echo that uses a long, thin, tube (endoscope) to guide the ultrasound transducer down the esophagus (“food pipe” that goes from the mouth to the stomach)
a combination of a ___,___ and ____ to get information about how blood flows across your heart’s valves
TEE, Doppler ultrasound, and color doppler
trans thoracic is ___ and utilizes ___
noninvasive and utilizes sound waves
trans esophageal combines ____ and ____
ultrasonography and endoscopy
what can you see with TEE
image posterior of the heart heart structures clots, valves PFO LV function
sites of injury from TEE
oropharyngeal
esophageal
gastric trauma
when can you not use TEE
when pt has: esophageal pathology recent upper GI surgery perforated viscus full stomach, unprotected airway
the output of the roller pump is determined by
the rpm of the pump and the volume displaced with each revolution
the volume of the roller pump depends on
the size of the tubing and the length of the track
the flow rate can be seen
on the pump control panel
2 methods to measure flow on centrifugal pump
- ultrasonic: not in contact with blood but instead wrap around tubing
- electromagnetic: require blood contacting electrodes and are designed as connectors
3/16 tubing has what SV and blood flow
7 ml SV
1050 L/min blood flow at 105 PRM
1/4 tubing has what SV and blood flow
13 mL SV
1950 L/min blood flow at 150 RPM
3/8 tubing has what SV and blood flow
27 mL SV
4050 L/min blood flow at 150 RPM
1/2 tubing has what SV and blood flow
54 mL SV
8100 L/min blood flow at 150 RPM
systemic flow is most often indexed to
the pt’s body surface area (m2) or weight (kg)
when normothermic or when cooling, generally accepted indices for systemic flow is
2.2 to 2.4 L/min/m2 or 50-65 ml/kg
when are higher indices for systemic blood flow used
in peds patients or when rewarming
150-200 ml/kg
adequacy of perfusion is estimated by
MAP (>50 mmHg) SVO2 65-75 blood lactate levels (<2) hematocrit urine output (0.5-1.0 ml/kg/hr) central and peripheral temp blood pH change in pressure CO2
activated clotting time (ACT) should be
greater than 400 seconds, to go on bypass: 480
how often should ACT be tested
every 30 min while cannulated
thromboelastography (TEG) is a test of what
whole blood coagulation
- measures the global disco-elastic properties of whole blood clot formation under low shear stress
- usually performed post CPB due long amount of time to perform the test
thromboelastography may be used to
guide blood product administration in bleeding patients
glucose levels should be
greater than 200 ml/dL
what are glucose levels treated with
insulin
