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60 Cards in this Set
- Front
- Back
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What is airlock when referring to a CPB machine? |
gravity siphon process of venous drainage that is disrupted by a large bubble
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What is the usual reading on the arterial inflow line pressure gauge? what is it prebypass?
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200-300mm Hg; the pressure reading on the guage prebypass should correlate with the arterial pressure tracing
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What are the indications if pulsations are absent from the arterial inflow line pressure guage?
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cannula has not been properly placed(and major dissection is about to occur with start of CPB), or the patient has been attached to the circuit backwards
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What should you do if pressure on the arterial inflow line pressure guage rises rapidly with the onset of bypass?
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turn off the pump, failure to do so will result in disruption of one or more of the fittings causing an explosion
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What should MAP during CPB be maintained at? Why?
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50 mmHg, lowest normal pressure at which autoregulation is maintained
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If the CPB pump fails what can you do?
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crank it by hand
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Where are cardioplegia catheters placed?
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through the right atrium and into the coronary sinus or the aortic root where cardioplegia can enter the coronary arteries
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How is LV venting accomplished?
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placing a cannula through the right superior pulmonary vein, into the L atrium, through the mitral valve and into the LV
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What is the purpose of the LV vent?
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prevents excessive distention of the LV due to physiologic shunting through the bronchial, thesbian, and pleural veins
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What does the cardiotomy suction do?
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adds blood to the circuit, it must be gentle so that blood cells are not traumatized
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What is the benefit of the bubble oxygenator?
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cheaper and easier to set up
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What is the benefit of the membrane oxygenator?
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less RBC damage, important when CPB runs >3 hrs
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What are the benefits of pulsatile pumps?
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reduce the neuroendocrine stress response; used less commonly
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What is the typical components of the priming solution?
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2L balanced salt solution, 20mL of 20% mannitol, hct is kept above 20, mannitol used to decrease incidence of renal failure
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During isovolemic hemodilution what principally maintains a normal SvO2?
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decreased blood viscosity
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What are causes of high aortic line pressures?
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occlusion of the line by a kink or clamp, cannula too small for flow, improper positioning of the cannula
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What are causes of low venous return during CPB?
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1. Occlusion of the venous line 2. Bleeding 3. Aortic dissection
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What are causes of hypertension during CPB?
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excessive flow, inadequate anesthesia
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How does cooling and rewarming affect ACT?
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cooling prolongs ACT, rewarming shortens ACT
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What is the typical concentration of potassium in cardioplegia solution?
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25-30mEq/L
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How often should cardioplegia be given and why?
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every 20min, reestablished hypothermia and washes out lactate
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What should you worry about with difficulty separating from bypass?
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post-ischemic myocardial dysfunction
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What patient's are at risk for postischemic myocardial dysfunction?
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poor presurgical function, long cross clamp times, poor myocardial preservation during cross clamp time
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How do you treat postischemic myocardial dysfunction?
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aggressive inotropic support with agents such as epi
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What is normal ionized ca and what is the typical value after bypass?
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2-2.2mEq/L; frequently falls to <1.5mEq/L
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When is recall most likely during CPB?
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rewarming
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How does temperature affect the solubility of O2 and CO2?
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at lower temp the solubility of both in solution is higher, less molecules in the gas phase, and the partial pressure of both is decreased, pH is therefore higher at lower temperature
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What is a temperature corrected blood gas?
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utilizes a computer normogram that corrects which corrects for solubilty and pH changes which occur with temperature
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What is alpha stat for ABGs?
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uncorrected arterial blood gas values, no attempt is made to correct parital pressure of O2 and CO2 for temperature
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What is the pH stat method of analyzing ABGs?
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temperature corrected values and involves administering CO2 systemically to patients to correct for lower CO2 partial pressure secondary to it's increased solubility in solution, it aims to keep pH at 7.4 and pCO2 at 40
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On a intraaortic balloon pump tracing what is the PSP and IP?
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peak systolic pressure-highest aortic pressure produced by ventricular ejection; inflation point: the point where balloon inflation originates(immediately following closure of the aortic valve)
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On a intraaortic balloon pump tracing what is the PDP and BAEDP?
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peak diastolic pressure: the highest aortic pressure produced by balloon inflation, usually higher than PSP; Balloon aortic end diastolic pressure: the lowest pressure in the aorta reflecting balloon deflation, deflation occurs just prior to opening of the aortic valve
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On a intraaortic balloon pump tracing what is the APSP, DN, PAEDP?
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assisted peak systolic pressure: systolic pressure which reflects balloon action; dicrotic notch: the landmark on the down slope of the arterial pressure waveform that signals aortic valve closure and the beginning of diastole; patient aortic end diastolic pressure: the lowest pressure normally occuring in the aorta(diastolic pressure)
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How is the balloon triggered?
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R wave on the EKG, during diastole, immediately following closure of the aortic valve.
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How does balloon inflation affect physiology?
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increased aortic diastolic pressure and thus increased coronary perfusion
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How does balloon deflation affect cardiac physiology?
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decreased afterload, increased SV, increased CO, decreased MVO2, decreased myocardial work
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When does balloon deflation occur?
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during isovolemic contraction(late diastole) just prior to opening of the aortic valve
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What are contraindications to IABP?
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aortic valve insufficiency, aortic aneurysm, severe aortoiliac or femoral disease
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What is the major risk of using IABP?
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inflation of the balloon during systole and subsequent impedement to CO
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What is the purpose of the arterial inflow line filter?
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Filters microemboli at about 40 microns. This can be bypassed if obstructed.
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How is perfusion during CPB best monitored?
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Assessment of UOP and mixed venous O2 sat as well as presence of acidosis
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What are the 4 complications of CPB?
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1. High aortic line pressure 2. Low venous return 3. Hypotension 4. Hypertension
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What are the 2 main types of oxygenators?
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1. Bubble oxygenator 2. Membrane oxygenator
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What are the advantages of hemodilution?
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1. Increased microcirculation 2. Increased UOP 3. Reduced blood demands
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What are pump flow rates usually?
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2-3 L/min/m2; adjustment of flow to mixed venous O2 sat is popular
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Explain cooling and rewarming on CPB?
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There is uneven distribution of body temp. Esophageal temp represents core temp. Rectal temp represents peripheral temp. Using the pump oxygenator, esophageal temp changes quickly. Using surface cooling and rewarming rectal temp changes quickly. Both temps should be monitored.
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What are the causes of hypotension during CPB?
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1. Pump problems, malfunction 2. Low venous return 3. low peripheral resistance caused by low hct or vasodilator
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Dose of Heparin for CPB
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3 mg/kg or 300 units/kg. 2 hrs after the initial dose 100 units/kg is empirically given
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What is the t1/2 of heparin? What does it depend on?
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Normal 1-3hrs. Depends on temp, dose, and presence of renal or hepatic dysfunction
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Normal ACT. what is acceptable for CPB?
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120-150. >300 for CPB is safe but usually >480
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What is more sensitive to measure clotting, ACT or PT/PTT and platelets?
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PT/PTT and platelets
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What is used to reverse heparin? What is the dose?
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Protamine 1 mg/100 units of the initial Heparin dose given. Heparin (acid) + protamine (base) = inactive salt
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Hypertension during CPB
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MAP >100. Not generally tx by lowering pump flow rate. Rx with volatile agent, vasodilator, or narcotic.
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What is considered Hypotension during CPB? What is it usually due to? How do you treat it?
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MAP <40 - most often due to either low CO or low peripheral resistance. Low CO tx by increasing pump flow rate. Low PVR rx by use of phenylephrine.
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CPB should not be discontinued until what temp is reached?
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Esophageal 37, rectal 33
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What does sweating during rewarming indicate?
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Does not mean awareness. It is secondary to hypothalamic rewarming.
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Explain how solubility of oxygen and carbon dioxide are temp dependent.
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At lower temps the solubility of O2 and CO2 in solution is higher. There are less molecules in the gas phase and the partial pressure of both is decreased. Partial pressure of CO2 is less and the pH is higher at lower temp.
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Immediate common problems coming off bypass.
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1. Myocardial dysfunction 2. Bleeding 3. Hypovolemia 4. Cardiac tamponade 5. Air embolism 6. Hypotension 7. Hypocalcemia
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Impaired blood clotting resulting from CPB is usually related to...
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1. Unreversed heparin 2. Decreased ionized calcium, 3. decrease in platelets 4. Decrease in fibrinogen (1 and 2 most common)
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Name the points on the IABP tracing.
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1. Peak systolic pressure (PSP) 2. Inflation point (IP) 3. Peak diastolic pressure (PDP) 4. Balloon aortic end diastolic pressure (BAEDP) 5. Assisted peak systolic pressure (APSP) 6. Dicrotic notch (DN) 7. Patient aortic end diastolic pressure (PAEDP)
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