Hemodynamic Monitoring and Cardiac Surgery Flashcards
Hemodynamic Monitoring
- can be invasive (arterial lines, PA catheter, central lines, SPO2) or non-invasive (VS, SPO2, end tidal CO2 monitoring - all things that can be done w/o poking people)
- measurements of pressure, flow, and oxygenation w/in the CV system
- tells us about heart function, fluid balances, the effects of drugs and fluids on CO
- tells us about O2 demand and delivery w/in body (making sure we know how much is going in and how much is being taken by the body and coming back to be circulated again)
- TRENDS ARE IMPORTANT
CO
normal: 4-8 L/min
CI
normal: 2.2-4
* more sensitive than CO b/c it’s based on body surface area of pt so more specific
* computer calculates CI once height and weight are entered
SV
stroke volume
amount of fluid being pumped, very dependent on amount of fluid available and HR
in order to have good stroke volume, need to have fluid and good stretch to accommodate the fluid
directly impacts CO (both fluid dependent)
SVI
stroke volume index
*preload, afterload, and contractility affect SV, and thus CO
MAP
normal: 65-105
represents maintained pressure w/in artery continuously (how much good circulation are arteries delivering to rest of body)
how to calculate: (systolic + (2 x diastolic))/3
Right Sided Heart Numbers
PAP - pulmonary artery pressure
-tells us about right side of the heart and pulmonary circulation
PAS: pulmonary artery systolic
normal = 20-30
PAD: pulmonary artery diastolic
normal = 8-15
PAWP/PCWP
pulmonary capillary/artery wedge pressure
indirect estimate of left atrial pressure, preload on the left side of the heart (if left ventricle is fluid overloaded, PAWP will be high b/c pathway of blood when fluid is overloaded is backwards - backs up into pulmonary circuit and causes balloon to read higher numbers)
measured via catheter (Swan-Ganz) inserted into peripheral vein and then threaded into branch of a pulmonary artery. Balloon on tip of catheter is inflated during insertion.
helps diagnose:
- valve stenosis (particular mitral valve), if if valve is stenosed your going to see blood back up into the pulmonary circuit
- severity of HF
- pulmonary HTN
- edema
Preload
volume in the ventricle at the end of diastole
dependent on fluid volume
CVP: preload for the right side of the heart, fluid returning to the right atrium and ventricle heart after circulating the body
-normal = 2-6 mm/h2O
PAWP: preload for the left side of the heart (left ventricular end diastolic pressure)
-normal = 6-12 mm/h2O
Afterload
afterload = SVR -normal = 800-1200
forces (the squeeze of aorta) pushing against ventricular ejection
affected by:
- arterial pressure, high arterial pressure > lots of work for the heart to overcome
- pressure of aortic valve: if it’s very stiff and doesn’t open a lot it’s going to create a lot of resistance
- mass and density of blood: thick blood is not going to flow as well
- high SVR = lots of squeeze
- low SVR = jiggly floppy aorta noodle (no resistance, not a good sign)
Contractility
strength of contraction
-normal = 55-70%
affected by disease that affect the heart muscle
high contractility causes: adrenaline release, SNS stimulation
tx high contractility: negative inotropes (like beta blockers, CCBs)
low contractility causes: anything that effects heart muscle, age, cardiac disease such as HF, CAD, history of MI, genetics (usually caused by underlying cardiac disease)
tx of low contractility: cardiac surgery or meds depending on how sick they are
Frank Starling Law
more stretch = more force
affected by preload (need fluid in order to have good stretch)
Meds that increase contractility
epinephrine, dobutamine, dopamine, milrinone
*dobutamine and dopamine can cause tachycardia and dysrhythmias
Milrinone
positive inotrope
benefit = vasodilation effect on top of being contractility agent. relaxes vessels making it easier for heart to pump in addition to making it pump better
Pulse Pressure
difference between systolic and diastolic BP
normal = 1/3 of systolic
increased pulse pressure (widening): d/t increased systolic which may occur during exercise, stress or in individuals w/ atherosclerosis of the large arteries
decreased pulse pressure (narrowing): d/t HF, hypovolemia, cardiac tamponade
*at minimum, should be a least 30 points difference but get concerned when it’s less than 20
Pulmonary Artery Catheter
aka Swan-Ganz
multi-lumen catheter inserted via right side of the heart (at IJ)
provides right and left heart numbers
Ports:
- distal: PAWP when balloon is inflated
- medial: fluids, meds
- proximal: CVP
Pulmonary Artery Catheter - Risks and Nursing Care
infection: assess line q4hrs, make sure it’s clean and dressing is completely occlusive and intact and any drainage is addressed
bleeding
balloon dislodgement or bursting causing cut off of circulation or damage to pulmonary vessels: closely monitor where we are wedging pt. balloon should only be inflated when we need to obtain wedge pressure
catheter can migrate and move: measure catheter depth q8hrs and make sure that number is consistent
SVO2
mixed venous gas (how much O2 is in blood after it circulates the body)
normal = 60-80%
*high O2 demand = low SVO2; low O2 demand = high SVO2
causes of low SVO2
anything that increases demand:
- fever (high temp increases O2 demand b/c of increase in metabolic rate)
- MI (poses risk to cardiac muscle, so cardiac muscle is requiring more O2)
- stress, activity (turning a pt causes SVO2 to tank b/c demand has increased by moving them, stop activity and come back to it after SVO2 has improved)
anything that decreases supply:
- lack of O2 (hypoxemic - give O2)
- lack of good cardiac function (anything that decreases contractility - MI, HF - not getting good supply b/c heart isn’t pumping it out)
High SVO2
usually a good sign and means pt is improving
OR
pt has sepsis
-there is a phase of sepsis where numbers look good (hyperdynamic phase) then takes a turn for the worst
Coronary Artery Bypass Graft (CABG)
bypass provides alternative source of blood flow by providing artery of vein and plugging it into somewhere that has good blood flow (maybe aorta or one of the stemming branches) and attach it further down on area of vessel where it was blocked therefore providing good blood flow to those areas again
can have a number of CABG’s done
conventional (open sternum, bypass machine) or minimally invasive (pt must be stable to get this)
Bypass
2 catheters are placed: in aorta (aortic arch) and superior or inferior vena cava.
pull out and circulate blood to vessels w/o providing circulation directly to heart
ventricles don’t beat so surgeon can work on heart
CABG Surgery - Roles
surgeon resident circulating nurse scrub nurse perfusionist
CABG Surgery - Intra-op
basic anesthesia intubated lines placed (Swan-Ganz and arterial lines) chest opened surgery starts artery/vein harvest portion chest closed pt stabilized taken off perfusion machine sent to cardiac ICU to recover
