Lecture 10 9/18/24 Flashcards
What is the goal of the cardiovascular system?
provision of circulating blood to allow delivery of nutrients, removal of waste, and homeostasis maintenance
What is CaO2?
amount of oxygen in arterial blood, mL/dL
What is CO/cardiac output?
the amount of blood pumped in a given time, L/min
What is the equation for delivery of oxygen?
DO2 = CO x CaO2
Which contributing factors of DO2 are routinely monitored during anesthesia?
-MAP
-heart rate
-heart rhythm
-CaO2
What are the characteristics of heart rate?
-quantitative
-important determinant of cardiac output
-sensitive indicator for change in physiologic status
What are the characteristics of heart rhythm?
-normal sinus rhythm allows for normal CO
-arrhythmia may alter CO and thus tissue blood supply
What is the primary method for monitoring heart rate and rhythm?
electrocardiogram
What information can be presented on an ECG?
-rate
-regular vs irregular rhythm
-P wave for each QRS
-PR interval
-QRS for every P wave
-ST segment
-T wave
What is palpated when assessing a pulse?
difference between SAP and DAP
How do pulse deficits appear on ECG and arterial pressure graphs?
the arterial pressure graph does not have a wave for every QRS on the ECG, indicating inadequate filling to produce a pulse
Why is pulse quality not a good surrogate for blood pressure?
pulse quality only relies on the difference between SAP and DAP, which can still be “good” even when the actual values are not
What is a plethysmograph?
graph that provides an indication of pulsatile flow
What are the methods for assessing pulsatile flow?
-plethysmograph
-pulse oximetry
-doppler
What are the characteristics of the mucus membranes as a monitoring tool?
-qualitative
-oral mucosa is more reliable than tongue
-pink color indicates good oxygenation +/- perfusion
-pale/gray/white coloration indicates vasoconstriction, hypotension, and/or anemia
-gray/blue indicates cyanosis and hypoxemia
-bright red indicates vasodilation and/or shock
What are the characteristics of capillary refill time?
-semi-quantitative
-normal value is around 1-2 seconds
-prolonged CRT results from vasoconstriction and decreased peripheral perfusion
-short CRT results from vasodilation
What is arterial blood pressure?
quantitative assessment of hydrostatic pressure in the arteries
Which blood pressure value is the best indicator of perfusion pressure?
MAP
How is MAP calculated?
MAP = 1/3 (SAP- DAP) + DAP
MAP = CO x SVR
What is hypotension?
-abnormally low blood pressure
-MAP < 60 mmHg
-SAP < 90 mmHg
What are the characteristics of direct ABP monitoring?
-quantitative
-invasive blood pressure measurement
-gold standard
-arterial catheter + BP transducer equipment
-continuous, beat to beat updates
What are the advantages of direct ABP monitoring?
-accurate
-continuous
-provides information regarding CO, wall tone, and arrhythmias
What are the disadvantages of direct ABP monitoring?
-invasive
-technically difficult
-requires capable monitors
-complications such as thrombosis, infection, and ischemia
How is blood pressure cuff size determined?
cuff width should equal roughly 40% of limb circumference
How does an incorrectly sized blood pressure cuff impact BP reading?
-if the cuff is too loose or too large the reading is overestimated
-if the cuff is too tight or too small the reading is underestimated
What are the characteristics of doppler ABP monitoring?
-quantitative
-non-invasive
-requires appropriately sized cuff, sphygmomanometer, and doppler
-doppler detects blood flow and transmits as an audible sound
-when cuff pressure is greater than SAP, no sound produced
-when SAP is just above cuff pressure, 1st doppler sound is heard; indicates SAP
What are the advantages of doppler ABP monitoring?
-non-invasive
-can be done on awake patients
-easy
-cheap
What are the disadvantages of doppler ABP monitoring?
-only measures SAP
-user error possible
-accuracy issues with extremes of ABP, brady/tachycardia, arrhythmias, and small patients
What are the characteristics of oscillometric ABP monitoring?
-quantitative
-non-invasive
-requires appropriately sized cuff and oscillometer
-detects oscillations in cuff due to arterial pulsation
-evaluates pressure at which oscillations change
What are the advantages of oscillometric ABP monitoring?
-non-invasive
-can be done on awake patients
-easy
-less expensive than IBP
-gives SAP, DAP, and MAP values
What are the disadvantages of oscillometric ABP monitoring?
-technical errors
-accuracy issues with extremes of ABP, brady/tachycardia, and arrhythmias
What is perfusion?
delivery of blood to the tissue
How is perfusion measured?
-by measuring the output of waste products from the cells (lactate)
-by measuring the oxygen difference between arterial and venous blood
