ObjectivesLearner will be able to state the definitionof basic hemodynamic terms. • The deﬁnition of hemodynamics. • The factors determining hemodynamics. • The deﬁnition of cardiac output. • Factors that determine cardiac output. • The deﬁnitions for preload, afterload, contractility. • Deﬁne cardiogenic shock, septic shock, hypovolemic shock and treatments.
WHAT ISHEMODYNAMIC MONITORING Simply stated hemodynamics is about pressure. Involves movement of blood. The measurement and monitoring factors that inﬂuence the force and ﬂow of blood. Universal law, all matter seeks its lowest possible energy state For blood it means trying to be at lowest pressure gradient. Hence going from highest to lowest pressure.
Gases also obey this pressure gradient• The reason carbon dioxide jumps off the blood stream, through alveolar capillary membrane and into alveoli is because there is less CO2 there.
Circulatory System Circulatory system divided into two major parts: Pulmonary System Systemic SystemPulmonary system made up of the right side of the heart right (right Systemic is made up of left side of atrium & right ventricle), the heart (left atrium and leftpulmonary arteries, & pulmonary ventricle), the arteries and veins. veins. Carry oxygenated blood from theArteries direct blood from the right left heart to different organ ventricle to the lungs. Veins systems. Veins partially return the conduct oxygenated blood from deoxygenated blood back to right lungs to left side of the heart. side of the heart.
IN THECIRCULATORY SYSTEM Heart is the pump that provides power to move blood throughout the blood vessels (perfusion) Blood vessels direct blood from the heart to tissues through arteries and capillaries (circulatory system) and back to the right heart through the veins Blood is the medium in which oxygen and other nutrients are carried to the tissues.
Blood movesdownstream• When leaving left ventricle pressure is about 120/80 mmgh• In capillaries pressure is about 20 mmHg• From capillaries , back to the right heart where pressure is about 4mmHg
WHAT IS CARDIAC OUTPUTCardiac output is the quantity of blood pumped out by theleft ventricle in each minute. Normal 4 - 8 L/min*Cardiac output is the product of heart rate and strokevolume (the vol. of blood ejected by the ventricle w/ eachcontraction.) Stroke volume is the volume of blood ejected by the ventricles by a single heart beat. Normal 60 -120ml/beat Cardiac output divided by body surface area is known as Cardiac Index. Normal 2.5 - to 4.0 L/min/m2*
What determines cardiac output? Heart Rate and Stroke Volume!! Stroke volume is a function of three important factors.Stroke volume is the volume of blood ejected by the ventricle by a single heart beat.Normal for adults 60 to 130 ml/beat.
Stroke volume is a function of three important factors. Preload After-load Contractility Arterial resistance to ﬂow Filling volume of the Forcefulness of myocardial out of the ventricles during ventricles (diastole). contraction contraction (aortic bp) SVR indicates afterload for If the ventricle is adequately the L. ventricle. PVR indicates ﬁlled & resistance to outﬂowThe ﬁlling volume of the afterload for the R. ventricle. optimal, cardiac output will ventricles prior to not be adequate if contractility Appropriate level of afterloadcontraction is one to the is poor. Factors that reduce for the L. ventricle is essential most important factors cardiac contractility are called to maintain adequate determining the negative inotropes & include perfusion pressure to the subsequent volume of hypoxemia, acidosis, & body. in afterload blood ejected during medications such as beta (peripheral vasodilation) will systole. Too little ﬁlling blockers. cause BP to drop. in BP willor too much ﬁlling leads Factors that increase stimulate the heart to C.O. to a reduced stroke contractility are called positive to maintain circulation. volume. inotropes and include certain The interaction between C.O. beta-adrenergics and & after-load determines BP. parasympatholytics.
Five factors we look at to determine hemodynamics • Right heart • Lungs • Left Heart • Too much ﬂuid • Not enough ﬂuid
Hemodynamics is all about pressures• CVP: Central Venous Pressure (before the R. heart)• PAP: Pulmonary Artery Pressure (after the R. heart)• PCWP: Pulmonary Wedge Pressure (after the lungs)• C.O Cardiac Output: although not a pressure but a volume it also relates to pressure (after the L. heart)• We are concerned about the functions that lies between these pressure values (i.e. right heart, lungs, left heart, and the systemic vascular system.)
Normal Values Also called right atrial pressure, right side preload, right ventricular end diastolic Measurement taken at the pressure... they all use right as description R. atrium or vena cava.CVP 2-6 mmHg Looks at function of right Low values may be High values heart in general dehydration or relates to ﬂuid vasodilation - ﬂuids or overload - vasoconstriction drugs. diurese the pt. Measurement taken w/ 6 - 15 transducer at tip ofPAP mmHg catheter placed in Also called Right ventricular after- load. (mean 14) pulmonary artery. Measurement taken w/ Also called left atrial 6-12 Relates to balloon-tipped catheter pressure, left ventricularPCWP Normal 8 inﬂated and wedge in ﬁlling pressure, left function of Left mmHg heart. pulmonary artery. ventricular preload If CO is , usu. Expressed as volume Generally relates to Left treat w/ cardiacC.O 4 - 8 L/min ventricle inotropics or rather than pressure. chronotropics.
Pressure after Relates to function the right heart of left heart PAP = 6 - 15 PCWP = 6 - 12 C.O. = 4 - 8CVP = 2 - 6 Pulmonary L/minPressure vascularbefore the system Generallyright heart relates to condition of left ventricle Right heart Left Heart
QUICK QUESTIONS TO ASK YOURSELFWHEN LOOKING AT THESE PRESSURES. What two pressure would you look at for right heart function? CVP and PAP CVP Before R. heart PAP After R. heart What two pressures would look at PWCP After lungs for blood ﬂow to the lungs? C.O. After L. heart PAP and PCWP What about left heart? PCWP and then volume C.O.
Etiology Results form inadequate cardiac contractility. Most common in the United states and most often seen in patients experiencing aCardiogenic shock: myocardial infarction. Approximately 6 to 7% of patients having an M.I. develop cardiogenic shock. Failure of vascular tone most often seen in the septic patient. Septic shock causes complex problems with maldistribution of ﬂow resulting in severe vasodilation and a very low afterload.Distributive shock: Cardiac output is often increased, but ﬂow to vital organs is often inadequate owing to low perfusion pressures and persistent hypotension. Hypovolemic Inadequate or decrease circulating blood volume. Can be a shock: result of bleeding from trauma, surgery, or dehydration.
Treatment Positive inotropes and vasopressors are the primary approach. Inotropics, chronotropes, and vasocontrictors, such as dopamines and norepinephrine, may be needed to improveCardiogenic shock: blood pressure. Inotropics should NOT be used if patient is suspected of having acute myocardial infarction given that in can further stress the heart and extend infarctions. Antibiotics and volume expansion are essential for patients in septic shock. Volume expansion improves BP by ﬁlling the void created by the peripheral vasodilation associated with sepsis.Distributive shock: Vasopressors such as dopamine and norepinephrine improve hypotension by partially reversing the vasodilation caused by sepsis and by stimulating contractility therefore improving cardiac output.. Rapid replacement of circulating blood volume is crucial. As a rule, ﬂuid resuscitation is needed whenever the systolic blood pressure is below 90mm Hg and there are no signs of vital Hypovolemic organ disfunction (abnormal sensorium). If patient had large shock: amount of blood loss, it is ideal to use blood as a replacement. If hypovolemic shock is not caused by bleeding, saline solutions are effective in aiding circulating blood.
Treatment Conclusion• Oxygen!!• Mechanical ventilation is most often needed in the patient with the type of shock that does not resolve quickly. Those with septic shock or sever cardiogenic shock most often need mechanical ventilation given that it aids in reducing oxygen consumption of the respiratory muscles.• Close monitoring of all patients diagnosed with shock in the ICU is important.