Critical Care: Hemodynamic Parameters Flashcards
Arterial blood pressure is the product of _____ and _____
- Cardiac Output (CO)
2. Resistance to flow (systemic vascular resistance, SVR)
Cardiac output is the product of ____ and _____. What are the units?
- Cardiac output (mL of blood pumped per minute) is product of
- Stroke volume (mL of blood ejected from left ventricle per beat)
- Heart rate (beats per minute)
Stroke volume is determined by what 3 factors?
- Preload (amount of blood available to eject)
- Afterload (resistance to ejection)
- Contractility (amount of force generated by the heart)
Three different ways to express arterial blood pressure?
- Systolic BP (SBP)
- Diastolic BP (DBP)
- Mean arterial pressure (MAP)
MAP is an indication of _____ perfusion pressure
Global perfusion pressure
A MAP of at least ___ is necessary for adequate cerebral perfusion in most patients
65 mm Hg
MAP can be calculated by equation, but what is a more timely and accurate what to get it?
Direct measurement from an arterial line
Define preload
Ventricular end-diastolic volume
Due to the Frank-Starling mechanism, preload is one of the three main factors that directly influences _____
Stroke volume
List two common measures of preload and two new measures of preload
Common: 1. Central Venous Pressure (CVP) 2. Pulmonary Capillary Wedge Pressure (PCWP) or Pulmonary artery occlusion pressure (PAOP) New: 1. Stroke volume variation (SVV) 2. Pulse pressure variation (PPV)
Central Venous Pressure (CVP) is the pressure in the _____ at the point of blood returning to the _____.
CVP is the pressure in the
- Vena cava at the point of blood returning to the
- right atrium
CVP may reflect _____ status, but is a poor predictor of ______ responsiveness
CVP may reflect
- Volume status, although it is a poor predicator of whether a patient’s low
- blood pressure (volume responsiveness) will improve with an increase in intravascular volume.
Historically, a CVP of __ to ___ mm Hg has been considered optimal for a patient with hypoperfusion from sepsis
8 to 12 mm Hg
A higher CVP goal of ___ to ___ mm Hg has been considered optimal for patients on a ventilator due to increased ______ pressure.
12 to 16 mm Hg due to increased intrathoracic pressure
Data on the use of CVP is _______. It is known to be a poor predictor of _______ and _______
- Lacking
- Volume responsiveness
- Volulme status
CVP values at the extremes and volume status?
- Less than 2 mm Hg reflect hypovolemia
2. Greater than 18 mm Hg reflect hypervolemia
PCWP or PAOP is the pressure when __________________
Pulmonary capillary wedge pressure or pulmonary artery occlusion pressure is the pressure when a balloon is inflated (wedged) in one of the pulmonary artery branches.
Why might PCWP be a more accurate measure of volume status than CVP?
The pulmonary artery branches are closer to the left ventricle than the inferior vena cava.
Measuring preload: What’s used to measure right heart? What’s used to measure left heart?
- Central Venous Pressure (blood returning to heart from vena cava) used to measure right atrial pressure; estimate right ventricle preload.
- Pulmonary artery occlusion pressure (aka pulmonary capillary wedge pressure) blood returning to heart from pulmonary vein.
Describe the frank starling mechanism and frank starling curves. (e.g. why is there a family of curves)
- Cardiac output is directly proportional to end-diastolic volume (i.e. preload).
- The proportionality constant (e.g. slope of the curve) is dependent on contractility (i.e. inotropy, the force pushing with) and afterload (i.e. resistance, the force pushing against.)
- Cardiac output represented by a family of curves. There is a family of curves. You slide up a curve based on preload, and you shift between curves (e.g. change slope of curve) based on inotropy and afterload.
Why has the utility of pulmonary artery occlusion pressure been diminished recently?
The use of pulmonary artery catheters has diminished in favor of bedside echocardiography.
What are two examples of functional hemodynamic monitoring used to assess a patient’s position on the Starling curve and their fluid responsiveness?
- Stroke volume variation (SVV)
2. Pulse pressure variation (PPV)
The simplest measurement of adequate oxygen delivery is assessment of _____ function
Assessment of end organ function
List three signs of end organ dysfunction that may be first signs of inadequate oxygen delivery
- Changes in mental status
- Decreased urine output (less than 0.5 ml/kg/hour)
- Cold extremities
