Book 4, case 5-CABG and MV replacement Flashcards
Roller vs centrifugal:
Roller not sensitiveto preload
or afterload (i.e. kinking, occlusion, increased SVR, clamp placement), can deliver
pulsatile flow, and reliably produces a certain amount of flow based on pump speed.
The disadvantages of this type of pump include: 1) relatively increased damage to red
blood cells; 2) the potential delivery oflarge quantities of air to the patient if air was
entrained into the pump;
Centrifugal: centrifugal (kinetic) pump, rotational force is responsible for forward flow.
A centrifugal pump is less damaging to red blood cells; is sensitive to changes in
preload and afterload; and will cease to function if a significant amount of air is
entrained.this type of pump is incapable of
delivering pulsatile flow and is only able to partially compensate (via increased
speed) for decreases in forward flow resulting from increases in distal pressure.
Alpha stat and pH stat: what do they both measure? What are their differences, and how would the operator do different stuff depending on the one they do?
Does it actually increase CO2 content?
there is some
evidence of slightly improved neuropsychologic outcomes with the use of alpha-stat
management in adults.
describes:
describe different approaches to managing
C02 in the hypothermic patient, where hypothermia leads to an increase in the
solubility of C02 with subsequent reductions in arterial pH and the partial pressure of
C02 (it does not reduce the total C02 content).
pH: pH-stat
strategy of gas tension management would add C02 to the oxygenator as necessary to
maintain a PaC02 of 40 mmHg and a pH of 7.40;
Alpha:
a practitioner using the alpha-stat
strategy of gas tension management would not add C02 with the onset of
hypothermia, maintaining electrochemical neutrality.
Primary Mechanism of brain injury in adults vs children and how that relates to pH and alpha stat
Adults: embolic events (so alpha stat would be best because CO2 would increase flow increasing risk of embolic events!)
Kids: ischemia so i wouold use pH stat (adding CO2 vasodilates increasing blood flow)
When is heparinization adequate to start CPB? What if you are using aprotin?
When ACT is greater than 480 seconds. Aprotin can artifactually prolong celite ACT.
Does it matter if his mitral regurgitation is acute or chronic in nature? Describe
the pathophysiology of acute mitral regurgitation.
It does matter, because acute mitral regurgitation results in left atrial
and ventricular volume overload without the compensatory ventricular dilation that
occurs with chronic mitral regurgitation. This results in markedly increased left atrial
and left ventricular end-diastolic pressures, leading to decreased cardiac output,
pulmonary congestion, pulmonary edema, and right ventricular failure. Furthermore,
elevated L VEDP combined with compensatory tachycardia places this patient at
increased risk of worsening myocardial ischemia.
PC wedge tracing during severe MR?
In the presence of mitral regurgitation, the pulmonary capillary wedge
tracing usually exhibits a prominent v-wave, an absent x-descent, and a rapid y-
descent.
Pulmonary capillary wedge tracing in a healthy heart
In the healthy heart, the c wave reflects elevation of the mitral valve during
early ventricular systole, the v wave reflects venous return against a closed mitral
valve, the x descent occurs with the downward displacement of the atrium during
ventricular contraction, and they descent represents the decline in atrial pressure as
the mitral valve opens during diastole.
What are core temps?
tympanic, nasopharyngeal, and esophageal are core temps
Shell temps?
rectal
Soooo..you need to measure which two temps during CPB surgeries? Avoid what as far as temp?
Core and shell due to the fact that you needto monitor temp gradient that develops during cooling and rewarming. Avoid large temp gradients (>10 degrees celsius) that can lead to formation of gas bubbles in blood. MAKE SURE PT IS NORMOTHERMIC PRIOR TO D/C OF CARDIOPULMONARY BYPASS
During laryngoscopy in Mitral regurg pt, BP increases and he goes into a fib-what do you think? What would you do?
The atrial fibrillation could be related to ischemia and/or atrial dilation
resulting from worsening mitral regurgitation. Inadequate anesthesia during
laryngoscopy could lead to hypertension and tachycardia with worsening mitral
regurgitation (secondary to hypertension) and increased myocardial oxygen demand
(secondary to both the hypertension and the tachycardia). An overaggressive
induction dose of anesthesia could lead to bradycardia with worsening mitral
regurgitation and/or hypotension with decreased coronary artery perfusion.
what would you do? atrial contribution to preload is less critical in patients with
mitral regurgitation versus those with stenotic lesions, I may just ensure control of
ventricular rate (P-blocker, calcium channel blocker, or digoxin) and monitor his
blood pressure closely. However, given this patient’s coronary artery disease and the
risk of worsening regurgitation and heart failure, I would have a low threshold for
pharmacologic ( amiodarone) or DC cardioversion should he develop signs of
ischemia or persistent hypotension.
Following the initiation of cardiopulmonary bypass, the perfusionist says that
the venous reservoir level is decreasing. What would you do?
Now what if Low BP CPB:
I would immediately have the perfusionist reduce pump flows and add
fluid to the blood volume as necessary to prevent reservoir emptying with subsequent
massive arterial air embolism. At the same time, I would look for potential causes of
decreased venous return, such as elevation of the heart by the surgeon or problems
with the venous cannula, including air lock, inadequate diameter, kinking,
malpositioning, or obstruction by thrombotic material.
Elevate patient’s height to facilitate passive drainage
Increase preload with volume or ask perfusionist to increase flow, could be due to decreased SVR so you may need pressor, could get an H&H to see if you need blood.
Following the surgical repair, the surgeon asks you to vigorously inflate the
lungs. Why? Is de-airing the heart important for this procedure? (CABG)
Vigorous inflation of the lungs following cardiopulmonary bypass
serves two functions. First, it aids in the recruitment of collapsed alveoli. Second,
the positive pressure results in increased blood flow through the pulmonary
vasculature, displacing air into the left heart where it can be more easily removed
with a vent.
Deairing: De-airing of the heart is important to prevent the end-organ damage that
can occur with embolization of air into cerebral or coronary arteries.
The patient is normothermic and an attempt is being made to wean him from
cardiopulmonary bypass. During this process, the pulmonary artery pressure
increases and the systemic pressure decreases. What do you think?
Same amount of volume in smaller space Increasing pulmonary artery pressures combined with decreasing
systemic pressures is suggestive of left ventricular failure. There are multiple
complications that could lead to left heart failure in this patient: 1) increased afterload
secondary to mitral valve replacement (the low resistance flow back into the atrium is
no longer available); 2) graft failure (kinking, air, clot); 3) inadequate myocardial
preservation during cardiopulmonary bypass; 4) inadequate coronary blood flow
(hypotension, coronary emboli, coronary spasm, tachycardia with decreased diastolic
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perfusion time); 5) myocardial infarction; 6) valve failure; 7) hypoxemia; 8)
inadequate preload (hypovolemia, loss of atrial kick); 9) reperfusion injury; 10)
acidemia; and 11) electrolyte abnormalities.
IABP is the only intervention that does what two things as it relates to myocardial oxygen supply?
IABP may prove beneficial by improving coronary
perfusion during diastole and reducing afterload during systole. This is the only
intervention that serves to reduce myocardial oxygen demand, while at the same time,
increasing myocardial oxygen supply.
Where does the IABP need to be placed? It should then be synchronized with the cardiac cycle-how?
The IABP should be positioned so that the tip
is at the junction of the aortic arch and descending aorta (below the left subclavian
artery to prevent cerebral emboli).
using either the arterial pressure wave form or the electrocardiographic QRS
complex, timed so that balloon inflation occurs with aortic valve closure ( dicrotic
notch of the arterial wave form & the middle of the T-wave on the ECG), and set at a
ratio of 1 :2 to allow for comparison of the natural ventricular beats to augmented
beats, which aids in the optimization of timing and efficacy.
deflation before upstroke in aortic pressure curve
