What Comes First? The PATIENT!!! View the patient first, the equipment is merely an adjunct.
Anatomical review Go to Start tutorial
Cardiovascular System Review Heart- pumps blood forward through the vasculature Arteries- carry oxygenated blood from the heart to the body. (Constriction and Dilation regulate the blood flow delivered) Capillaries-microscopic vessels that allow for exchange of gases, nutrients and metabolic waste between plasma and the body cells
Hemodynamics Basic tenet is the control of adequate oxygen delivery to the tissues. Interrelationship of various dynamic forces that affect the blood’s circulation through the body. Knowledge of pressure, flow and resistance provide the foundation of understanding.
Continued… The ability to anticipate hemodynamic deterioration or detect adverse changes early is a major factor in preventing hemodynamic crisis, thus the major reason for hemodynamic monitoring.
Indications for Hemodynamic Monitoring Dehydration Hemorrhage GI Bleed Burns Surgery Acute MI Cardiomyopathy Shock: all types: septic, cardiogenic, neurogenic, anaphylactic Congestive Heart Failure
Cont.. Veins return deoxygenated blood to the heart. About 70% of circulating blood volume is in the venous system at any one time. Blood has both a cellular and fluid component. About 60% of blood is plasma. The remainder consists of RBC’s, WBC’s, platelet’s. ERYTHROCYTES make up about 99% OF THE CELLULAR COMPONENTS AND ARE RESPONSIBLE FOR OXYGEN TRANSPORT. An increase in RBC’s increases viscosity of blood. Increased viscosity makes blood flow through smaller vessels more difficult.
Pressure, Flow and Resistance Basic physics law: Pressure=Flow X Resistance
Pressure=the force exerted Blood Flow= the amount of fluid moved per unit of time Resistance=the opposition to force or flow (influenced by the size, length and viscosity of the fluid)
Cardiac Cycle Both the atria and the ventricles have filling phases (diastole) and contraction phases (systole) During diastole the left and right ventricles receive blood from the atria During systole the ventricles squeeze blood from the heart to the aorta and the pulmonary artery. See figure 7.4 p.131
Atrial Kick Final contraction of the atrium filling the ventricle…
Preload Left ventricular end-diastolic VOLUME. The VOLUME left in the ventricle when the mitral valve closes determines the amount of blood ejected into the systemic circulation. The ventricle never ejects its entire volume…just a portion of it…usually 60-70%( this is the EF..(ejection fraction) The volume of blood EJECTED with each beat is referred to as Stroke Volume (SV).
Arterial Blood Flow Arterial blood pressure=measure of force exerted on the arterial walls by the blood
Afterload =The pressure or resistance of blood flow out of the ventricle. So, if arterial BP is high, the left ventricle must exert more force to pump blood out effectively…this increases myocardial oxygen requirements.
Contractility A measure of how forcefully the ventricle contracts to eject its volume. It is the intrinsic ability of the muscle fibers to shorten.
Systemic Vascular Resistance (SVR) THE major factor that influences SVR is the lumen (diameter) of the vessel. This is an important concept, often in the critical care setting, medications are used to alter the lumen size of systemic vessels (primarily the arterioles).
Hemodynamic Monitoring Equipment All contain: a transducer, monitor, and fluid filled catheter, tubing and flush system
Swan-Ganz Cath Normally has four ports (can have another proximal lumen for fluids or medication infusion) The thermistor lumen is used to measure cardiac output. The proximal port is used to measure right atrial pressure Distal lumen measures pulmonary artery pressure The balloon port has a special 1.5 ml syringe connected…this is used to measure PCWP
Functions of the Catheter Continuous hemodynamic monitoring, assessing vascular tone, myocardial contractility, and fluid balance. Measures PAP, CVP, and allows hemodynamic calculations. Cardiac output can be determined using thermodilution. Transvenous pacing
Complications of a Swan/Ganz Infection Dysrhytmias Air Embolism Pulmonary thromboembolism Pulmonary artery rupture Pulmonary Infarction See table 7-1 p. 147
Arterial Monitoring An invasive technique for monitoring arterial blood pressure. Preferred in unstable patients because it is accurate and continuous
Allen's test A test for integrity of the radial and ulnar arteries at the wrist. The examiner compresses the patient's radial and ulnar arteries at the wrist. The patient is then asked to open and close the hand rapidly until the palm appears white. The examiner then releases either the radial or the ulnar artery and looks for return of pink color and circulation to the hand. The test is then repeated releasing the other artery. The hand should return to its pink color within 6 seconds if circulation through that artery is adequate.
Indications for arterial Monitoring Patients requiring frequent ABG’s or lab work Patients with low flow states, hypotensive Patients with severe hypertension Patients with severe vasoconstriction or vasodilation.
Arterial Lines Placed in an artery, usually the radial, but can use femoral, or brachial. Connected to a pressurized source Complications include: thrombosis, embolism, blood loss, infection Tubing and transducer replaced every 96 hours.
Continued, Caveats Invasive monitoring is more accurate Invasive BP should by higher than cuff BP If cuff BP is higher look for equipment malfunction or technical error A dampened wave form can indicate a move toward hypotension…an immediate cuff pressure should be obtained
Nursing Implications Prevent or reduce the potential for complications. Maintain 300mmHg on bag Maintain continuous flow through tubing Aseptic dressing change Sterile caps on openings Change tubing q 96 hrs. 5 min hold on discontinued site
Arterial Measurements The systolic pressure is measured at the peak of the waveform. See fig p137 This pressure reflects the function of the left ventricle. NORMAL value= mmHg
The LOWEST point on the waveform represents the end diastolic pressure. This pressure reflects systemic resistance. Normal diastolic pressure is mmHg
Dicrotic notch The small notch on the downstroke of the wave form. It represents the closure of the aortic valve. This is the reference point between the systolic and diastolic phases of the cardiac cycle.
Mean Arterial Pressure/MAP Is a calculated pressure that closely estimates the perfusion pressure in the aorta and its branches. It represents the average systemic arterial pressure during the ENTIRE CARDIAC CYCLE. Normal MAP = mmHg MAP MUST be maintained above 60 for the major organs to perfuse.
CVP/ Right Atrial Pressure Monitoring A direct measure of the right atrium pressure Clinical significance: REFLECTS RIGHT VENTRICULAR DIASTOLIC PRESSURE Abnormalities in RAP are caused by conditions that alter venous tone, blood volume, or right ventricular contractility
Cont… Low RAP indicates hypovolemia that may be attributed to dehydration, acute blood loss, extreme vasodilation (as in sepsis) High RAP indicates severe vasoconstriction, fluid overload, pulmonary hypertension