hemodynamics Flashcards
cardiac output
- best indicator of the condition of the hearts contractile (inotropic ability)
- volume of blood ejected by the heart in 1 min into the systemic circuit
- does not equate for differences in body size
normal CO
4-8 l/min
cardiac index
CO divided by an indiviuals body surface area
normal: 2.2-4
measured by PA cath
CO = ____ x ____
SV x HR
what is stroke volume
- volume of blod ejected by the left ventricle during each systole
- affected by three factors: preload, afterload, and contractility
normal SV
60-100 ml
what is preload
- The amount of stretch placed on cardiac muscle fibers just before systole.
- Volume of blood in the ventricle at the end of diastole
- Amount of myocardial stretch placed on the ventricular muscle fibers prior to systole application of Frank-Starling law of the heart
- Volume of blood creates a filling pressure
causes of elevated preload
- volume overload
- LV dysfunction
- RV dysfunction
- valvular defects
- cardiac tamponade
effects of increase preload on the heart
Increases stroke volume
Increases ventricular work
Increases myocardial oxygen requirements
assessment of right sided elevated preload
JVD
Edema
Hepato-jugular reflux(HJR)
assessment of left sided elevated preload
Orthopnea
Dyspnea
Cough
Crackles
S3
ways to reduce preload
- Drugs that directly reduce blood volume, e.g. diuretics
- Drugs that promote vasodilation, e.g.
Nitrates - Patient positioning (semi/high fowlers)
causes of decreased preload
Hypovolemia
Hemorrhage
Third spacing
Diuresis
Vasodilation
assessment findings of a decreased preload
Tachycardia/hypotension
Dry, cool skin
Dry mucous membranes
Poor skin turgor
Alteration in LOC
Decreased urine output/vital organ perfusion
right sided preload assessment
Right Ventricular End-Diastolic Pressure (RVEDP)
Right Atrial Pressure (RAP)
Central Venous Pressure (CVP)
left sided preload assessment
Left Ventricular End-Diastolic Pressure (LVEDP)
Pulmonary Artery Wedge Pressure (PCWP) aka
Pulmonary Artery Occlusive Pressure (PAOP)
Pulmonary Artery Diastolic Pressure (PADP
treatment to increase preload
volume administration
patient positioning - modified trendelenburg
what is afterload
Increased ventricular wall tension or stress during systolic ejection
Pressure that the ventricle has to pump against to eject blood into the circulation during systole.
Most critical factor determining afterload is vascular resistance.
- Systemic vascular resistance (SVR)
assessment of afterload
Mean arterial pressure (MAP) *not always correlated
Systemic Vascular Resistance (SVR)
- must have an invasive catheter to calculate SVR (must know cardiac output)
Pulmonary Vascular Resistance (PVR)
what causes an elevated afterload
Vasoconstriction (increased SVR)
Medications
- Alpha 1 agonists
Catecholamine release (compensatory mechanisms)
- Hypovolemia
- Pain
- Hypoxia
- Hypothermia
Hypertension
Increased aortic impedance
afterload reduction therapy
Vasodilator therapy
- Nitroprusside (Nipride)
- Calcium Channel Blockers (Nicardipine)
- ACE-Inhibitors (-pril)
- Angiotension Receptor Blockers (-sartan)
what causes a decreased afterload
Vasodilation (decreased SVR)
Inadequate aortic valve function
Inflammatory response
Hyperthermia
therapy to increase afterload
Vasopressor therapy e.g. Adrenergic stimulants
- Norepinephrine (Levophed)
- Phenylephrine (Neo-synephrine)
- Dopamine
- Vasopressin
what is contractility
The inotropic action of the heart muscle during systole or the force of each ventricular contraction
what factors influence contractility
Intracellular calcium and ATP availability
Coronary artery perfusion
Cardiac oxygen supply/demand balance
Heart rate
Blood pressure
Valve competence
assessment findings with low contractility
Tachycardia
Cool, pale skin
Decreased urine output
Mental status changes
Poor peripheral circulation
how do we measure contractility
Cardiac output (CO)
Cardiac Index (CI)
Ejection Fraction (EF)
interventions to increase contractility
increase preload
positive inotropic agents
interventions to decrease conractility
negative inotropic agents
inotropic
myocardial contractility
chronotropic
heart rate
dromotropic
rate of electrical conduction
beta 1 receptors
Located primarily in the heart.
Stimulation produces:
altered ventricular function
+ chronotropic
+ inotropic
beta 2 receptors
Located in bronchial and vascular smooth muscle.
Stimulation produces:
bronchodilation
alpha 1 receptors
Located primarily in vascular smooth muscle
Stimulation produces vasoconstriction
Increased SVR
what is the phlebostatic axis
Reference level for placement of the transducer to ensure accuracy of measurements
Point is located at the intersection of two imaginary reference lines:
1st line - 4th ICS at sternum drawn to side of body
2nd line - drawn midway between anterior and posterior chest (mid-axillary line)
what MAP is needed to perfuse coronary arteries
> 60
ideal MAP
70-90
arterial lines
pre procedure
allens test
arterial lines
maintenance
Leveling & Zeroing
Phlebostatic Axis
Compare cuff pressure
Check circulation
Complications
IF BP CHANGES QUICKLY: CHECK PT, CONNECTIONS & LEVEL OF TRANSDUCER
what does CVP measure
CVP measures the pressure in the right atrium or vena cava.
Provides information regarding intravascular blood volume
Indirectly reflects right ventricular end-diastolic pressure (RVEDP)
Measures right ventricular preload
normal CVP
8
which port is used to measure CVP
distal
closest to right atrium
complications to CVP monitoring
Infection
Dislodgement
Pneumothorax
Thrombosis
Air embolism
PA pressure monitoring
Flow Directed Pulmonary Artery Catheter
“AKA” Swan-Ganz Catheter
Used to obtain intra cardiac data to diagnose/evaluate heart disease, shock states and any medical or surgical condition that compromises cardiac function and output;
To evaluate patient response to treatment
complications with PA monitoring
Pneumothorax
Infection
Ventricular dysrhythmias
Pulmonary artery rupture or perforation
Air embolus
