CPB (Neuro/Endo) Flashcards
What is the incidence of stroke during surgery?
2-8%
Does CPB alone increase the risk of minor post-op neurologic dysfunction?
Yes, especially during the early post-op period
What are the sources of microemboli while on CPB?
Air (from oxygenator, heart, temperature gradients, IV solutions, arterial line filter) + Oxygen + Lipid globules (from cardiotomy suction) + muscle/connective tissue fragments + platelet/leukocyte fibrin aggregates + plastic + calcific particles (from aorta, cannulation sites)
What are the major sources of macroemboli during cardiac surgery?
Large air bubbles or atheromatous/calcific debris from valvular lesions or plaques on the aorta; most often occurs during clamping and cannulation of the aorta
What is an air embolus made primarily of?
Nitrogen (doesn’t desolve rapidly); this is why a CPB circuit is flushed with highly disssolvable CO2
What are signs of an air embolus?
Seizures, arrhythmias, and ventricular dysfunction
How can you decrease the risk of air embolism while on CPB?
Arterial filters/pre-bypass filters (decreases pump debris and gas/particular matter)
What are common sources of air embolisms?
Aorta, pulmonary vessels, and intracardiac negative pressure vents + unexpected, open contracting heart + pressured cardiotomy circuit + reversal of vents
Where does most air end up in the heart?
LAA + ventricular apex + spaces between chordae tendinae, pap muscles, and trabeculae carinae + cardiac chamber cul-de-sacs + aortic root
What are independent risk factors for neurologic dysfunction after cardiac surgery?
Advanced age (>75yo are 2x more likely to have a neurologic event) + duration of CPB (>2 hrs) + DM, history of CVA, and calcified aorta
What are ways to monitor the CNS during cardiac surgery?
EEG + transcranial doppler (measures blood flow velocity through MCA - can detect embolic events) + jugular venous O2 sat (measures cerebral O2 delivery)
What is the formula for cerebral perfusion pressure and what is the normal range?
CPP = MAP - ICP (or CVP); normal is 60-80 mmHg
What does pH stat generally do to the CNS during hypothermia?
Keeps patients more acidotic (adding CO2 to preserve pH of 7.4 and PCO2 of 40) which leads to cerebral vasodilation and increased CBF; loss of cerebral autoregulation and mismatch of CBF and CMRO2
Which method of acid-base management has been associated with improved neurologic outcomes in adults?
Alpha stat; possibly due to decreased risk of microemboli (since there is hypocarbia and cerebral vasoconstriction) while pH stat adds CO2 so increased CBF and higher risk of emboli
Which method of acid-base management has been associated with improved neurologic outcomes in children?
pH stat; less risk of emboli so you get better balanced brain cooling with cerebral vasodilation (CBF and CMRO2 are dissociated) + right-shift of oxy-hemoglobin dissociation curve
How much of your CO does the splanchnic circulation receive and why is it at risk during CPB?
20% of CO and is unable to autoregulate at extremes of blood pressure so it is more vulnerable to flow changes while on CPB