Cardiac Intra-op Mgmt (pt 1/2) Flashcards
What is your room setup for CPB?
1) Monitors- Standard ASA monitors plus ABP/PAP/CVP, Cerebral Oximetry, BIS, TEE
2) Medications
-Emergency: Inotrope (Epinephrine), -Vasopressor (Phenylephrine), Vasodilator (Nicardipine)
-Routine: Induction agent, paralytic, narcotic, Heparin
3) Infusions READY
-Carrier (Aminocaproic Acid or NS)
-Vasopressor (Phenylephrine) and/or Inotrope (Epinephrine)
-Vasodilator (Nicardipine, NTG)
4)Blood available
5) Temporary Pacemaker
What is important to know with premedication and CPB?
-The risk of recall is higher in cardiac surgery as compared to other surgical procedures.
-Surgery itself coupled with insertion of arterial lines prior to induction is painful and anxiety provoking
-Resultant anxiety can produce an unwanted sympathetic response—>versed and fentanyl
-Be cautious in patients with CHF and low CO as well as patients with pulm HTN (don’t make them hypercarbic at all)
What are your pre-bypass goals?
- keep the patient where he lives
- the enemy of good is better: not chasing perfect numbers under anesthesia prior to correction of the underlying problem
- do no harm
What are the pre-bypass periods of GREATER stimulation?
-Incision
-Sternotomy and retraction
-Sympathetic nerve dissection (within pericardium)
-Pericardiotomy (highly stimulating if SNS nerves are dissected)
-Aortic cannulation
**inadequate anesthesia during these times increases circulating catecholamines, possibly resulting in hypertension, dysrhythmias, tachycardia, ischemia, or heart failure
What are the pre-bypass periods of LESS stimulation?
-Preincision
-Peripheral graft harvest
-IMA dissection: risk of extensive bleeding, may do small bolus of heparin, may need to hand ventilate (lungs get in the way)
-Venous cannulation
**risks during these periods include HOTN, bradycardia, dysrhythmias, and ischemia
What are your goals for induction?
“Low, Slow, and Neo”
-Render the patient unconscious
-Avoid worsening cardiac pathology: Myocardial ischemia, valvular pathology, Hypotension, tachycardia
-Blunt stress response
-All induction agents (except Ketamine) decrease vascular tone (arterial and venous), and cause some amount of cardiac depression
What do you do for induction with a CPB patient?
1) Lidocaine: 1-1.5mg/kg
-Provides local anesthesia to vein; blunts sympathetic response to intubation
2) Induction Agent
-Propofol – 1-2mg/kg – Preferred for LVEF >35%. Reduced dose due to cardiac disease, causes significant vasodilation and hypotension – up to 40%
-Etomidate – 0.2-0.3mg/kg – Preferred for LVEF <35%. Vasodilation/Hypotension – 10-15%, Cardiac depressant effects less profound than propofol, but can cause adrenal insufficiency for up to 24 hours after just 1 dose.
3)Neuromuscular blocker
-Succinylcholine 1-1.5mg/kg
-Rocuronium – 0.6-1mg/kg
-Vecuronium – 0.1mg/kg
How do you manage BP during induction?
-Induction doses - lower than in a non-cardiac patient
-Phenylephrine syringe readily available throughout the induction period
-LOW-SLOW-NEO
What is the most stimulating portion of induction?
Laryngoscopy.
-Avoidance of tachycardia is extremely important
-Increased myocardial oxygen demand
-Decreased diastolic filling time → Decreased stroke volume
-For cardiac disease that will be significantly worse with tachycardia - Esmolol syringe readily available (Severe CAD (Left Main Disease), Aortic stenosis, Mitral stenosis = NO TACHYCARDIA in these people)
When is Ketamine used for induction?
Ketamine – 2mg/kg
-Useful for patients with compromised hemodynamics (Hypovolemia due to hemorrhage or Cardiac Tamponade***)
-Will cause increases in sympathetic response (Tachycardia, hypertension)
-Avoid in patients with increased ICP
-Also not great for usual CAD patient
When could a Sevo Inhalational induction be used?
-Useful for Low EF
-Hemodynamic compromise less likely with inhalation induction
-Induction can be fast in patients with biventricular (especially RV) dysfunction. Concentration will be higher in the lungs due to poor perfusion.
What do you need to do pre-incision?
-Check pressure points
-Send baseline ABG/ACT
-Antibiotics: Vanc and Cefazolin
-Check lines (arms will be tucked)
-Start Amicar bolus & infusion (Aminocaproic acid): Antifibrinolytics are used to minimize bleeding and therefore decrease patient exposure to blood products.
-Hemodynamics: Keep them within 20% of baseline
How does stimulation change during the pre-incision period?
-Large stimulus during intubation & TEE placement
-Minimal stimulation during prepping & draping
-Decreased SNS tone + decreased stimulation = post induction slump.
-Maintain coronary perfusion.
How do you treat post-induction slump?
-Maintain coronary perfusion by maintaining preload/afterload & minimizing tachy/bradycardia
-Phenylephrine infusion very useful in maintaining vascular tone
-Fluid administration is not first line treatment for hypotension
Why is fluid administration not the first line tx for hypotension with CPB?
Avoidance of hemodilution (patients will get really hemodiluted when on bypass, so don’t want to give a lot of volume before going on bypass)
What should you do as you prepare for sternal incision?
-Ensure sufficient muscle relaxation
-Acceptable to use a little Neo to allow for appropriate administration of Fentanyl prior to sternal incision
-surgeon leaving to scrub= sternal incision is imminent
-Don’t want tachycardia with incision: give narcotics right before.
Incision = Increased stimuli
Prepare for hypertension and tachycardia
-Fentanyl +/- Propofol & Esmolol/ Nicardipine
What is Autologous Blood Removal?
-May take a unit off to sequester platelets and clotting factors from damage during CPB, with return at conclusion of bypass
-Stored in a bag with citrate phosphate dextrose solution (CPD) similar to banked blood.
What are the risks associated with Autologous Blood Removal?
-HOTN 2/2 hypovolemia
-Decreased O2-carrying capacity, which will be reflected on mixed venous sat
-Infection—maintain sterile technique for removal and subsequent return
What are the relative contraindications for Autologous Blood Removal?
-Left Main dz (can’t tolerate dec in O2 carrying capacity
-LV dysfunction
-Anemia with Hgb <12
-Aortic Stenosis
-Emergency Surgery
Why is autologous blood removal done?
Only for on-bypass procedures.
-Bypass machine makes plts inactive/dysfunctional due to heparin.
-Taking blood off so that it never touches the circuit and you have functional cells available at the end of surgery.
-Also reduces blood viscosity.
-Don’t give blood back until after bypass and protamine is given.
What is your job during Sternotomy?
-Turn off ventilator to reduce risk for accidental lung injury from saw
-Surgeon may say “Lungs Down”
-Turn off Vent & pull off bag so no PEEP
-Remain vigilant – expectation is that you are aware of what’s happening in the field!
What is different about a Redo Sternotomy?
-Pericardium not usually closed after heart surgery—aorta, RV, and bypass grafts may adhere to underside of sternum
-Oscillating saw used to decrease risk of injury
-If preoperative imaging suggests mediastinal structures adherent to sternum, peripheral cannulation and preparation for CPB may be necessary
-If any major structures are accidentally cut, definitive treatment=CPB
-Blood products checked and ready for administration
-Prolonged dissection increases risk of dysrhythmias with re-do
-External defib pads always placed on these patients prior to induction.
How do you manage hemodynamics prior to going on bypass?
-Short acting agents are best: Phenylephrine, Nicardipine, Esmolol
-Volume administration NOT preferred
-Your job is to prevent worsening of cardiac pathology
-Hypotension = Ischemia
-Tachycardia = Increased Oxygen demand, decreased LV Filling
What is the initial dose of Heparin?
300 units/kg (dependent on baseline ACT
-AT3 deficiency needs to be treated with giving ATIII or FFP
When is Heparin given?
ALWAYS given prior to aortic cannulation.
-Give heparin, set a timer for 3 minutes, and draw ACT.
-Need ACT > 450 prior to cannulation
What are you BP goals during Aortic Cannulation?
-Systolic blood pressure 90-100 for aortic cannulation (high pressure = inc risk for dissection of aorta)
-When you see surgeon putting purse-strings in the aorta, start working on optimizing blood pressure.
Why is the aortic cannula inserted first?
Aortic cannula inserted first to allow infusion of volume in case of hemorrhage associated with venous cannulation.
What is the usual arterial cannulation site? Backups?
Most common arterial access site is the Distal Ascending Aorta.
-If not an option (Type A Dissection or redo sternotomy), femoral arterial cannulation or axillary may be used (Axillary is more likely)
What are the complications of Aortic Cannulation?
-Embolic phenomena from air or atherosclerotic plaque dislodgement
-HOTN—usually 2/2 hypovolemia but may result from mechanical compression of heart pay attention to what the surgical team is doing
-Dysrhythmias likely r/t surgical manipulation
-Aortic dissection can occur with cannula misplacement—pulsatile pressure from aortic cannula that correlates with arterial line MAP effectively rules out dissection
-Bleeding: minor not uncommon, major if aorta torn—give volume or (more likely) go on CPB
-Air entrainment from around cannula with systemic embolization
What do you do after the aortic cannula is placed?
Gently raise SBP to 100-120 mmHg so perfusion can RAP.
How is Venous Cannulation performed?
-Incision in right atrium, cannula placed into atrium and down into IVC
-Accompanied by significant dysrhythmias and hypotension
-BiCaval Cannulation: SVC Cannula added through RA
-Alternative site: femoral vein cannulation
What are complications associated with Venous Cannulation?
-HOTN—again r/t hypovolemia or mechanical compression (heart commonly manipulated during venous cannulation)
-Bleeding—if RA or SVC/IVC torn
-Dysrhythmias
-Air entrainment: Line will be checked for air bubbles
How can you help prevent air entrainment during cannulation?
PEEP may be helpful to avoid air entrainment during cannulation of RA by increasing intracardiac pressures
What is the purpose of placing the Aortic Root Vent (cardioplegia) line?
-A small cannula is placed in the aortic root, below the aortic cannula.
-Put at aortic root for de-airing heart at end of CPB
-Used for administering cardioplegia: High potassium cold solution that we fill the heart with to stop the heart.
-Blood pressure goals are same as aortic cannulation.
Why is Antegrade Cardioplegia used?
-Want cardioplegia solution to get into coronary arteries. Insertion of R and L coronaries at aortic root.
-Cardiomyocytes stop in diastolic arrest.
-Can get by with just antegrade plegia in valve surgeries
Why is Retrograde Cardioplegia used?
-Patient has a clot or issue that causes blood to not get to the heart. Cardioplegia solution will be blocked by the clot as well.
-Used to get solution to ischemic area of the heart.
-Uses venous system of the heart. Feeds backwards into the coronaries
-Cannula in coronary sinus. Push the plegia solution in backwards.
-Only used in patients with CAD.
What is Retrograde Autologous Priming?
-Perfusionist will drain blood out of the patient through the aortic cannula to prime the CPB circuit. Essentially, just back priming the circuit with aortic blood.
-Reduces hemodilution
-May cause hypotension – perfusion may request increase in BP to facilitate drainage (give Neo).
Describe the commencement of CPB?
-Once cannulae in place and confirmed to be appropriately positioned and patent, the surgeon will indicate time to initiate CPB.
-Surgeon will announce “Go on Bypass”
-Perfusion will gradually increase flow of oxygenated blood through the arterial cannula
-Venous clamp gradually released allowing increasing portion of systemic venous blood to drain into CPB reservoir
-Arterial inflow increased until roughly equal to normal CO= “full flow” (CI 2.2 -2.4)
-Continue ventilation until full flow is confirmed. Will see dampening of arterial line.
What is your initial bypass checklist?
Lungs Down & off; Volatile agent off
Vasopressors/dilators off (Goal MAP is ~70)
Confirm Perfusionist has Isoflurane On
Confirm Neuromuscular Blockade (no twitches)
Empty Foley/Document Urine Output
What do you need to assess about the patient when you first go on bypass?
-Face: examine for color, temperature, edema, and symmetry
-Eyes: examine pupils for size and symmetry, conjunctiva for edema
-Pump lines: AV color difference should be visible (aortic very red and venous very dark)
-ABP: 30-60 mmHg initially (will see big drop when you get on bypass at first)
-PA Pressure: <15 mmHg
-CVP: <5 mmHg
-Examine the heart: Distention (not draining appropriately)? Contractility?
-Stop ventilation
What do you need to monitor during CPB?
-ECG, MAP, CVP, core temp, UOP, Cerebral oximetry, BIS
-Perfusion watches cerebral oximetry. Pay close attention to glucose and Hgb
How is the volatile administered during CPB?
-Volatile is administered by perfusion via pump oxygenator
-Have a more defined role in myocardial protection that other anesthetics through ischemic preconditioning and reduction of reperfusion injury
Why do you need to ensure muscle relaxation during CPB?
Movement during CPB risks cannula dislodgement; spontaneous ventilation risks development of negative vascular pressures and potential air entrainment
What occurs to the body temperature under CPB?
-Anesthetic requirements decrease as body temperature decreases
-Due to relatively high blood supply, brain temp will change faster than core temp.
-Hence must ensure adequate anesthesia as soon as rewarming commences.
-Rewarming - risk of awareness. Can start propofol drip during rewarming.
How do you monitor the depth of anesthesia during CPB?
-Awareness may be difficult to exclude due to use of high-dose opiates, cardiovascular drugs (e.g. beta blockers), and muscle relaxants
-HD cues unable to be used during CPB
-Check patient for pupil dilation & sweating
-Monitor BIS
What is your MAP goal during CPB?
MAP: 50-70 mmHg
Higher pressure if pre-existing HTN or cerebrovascular dz
How is CO maintained during CPB?
-CO is generated by the CPB pump
-Perfusion regulates the flow depending on patient’s height, weight, and temp
~2.4 L/min/M2 at 37C and ~1.5 L/min/M2 at 28C
-Metabolic needs are decreased.
How is MAP maintained during CPB?
-Flow rate can be increased temporarily during HOTN, but this is NOT appropriate for persistent HOTN.
-Pressure is r/t the SVR. Can increase flow, but not going to correct the problem of hypotension. May need pressor to ensure good tone.
Inadequate perfusion flow rate will cause what to happen?
-Inadequate perfusion flow rate will result in development of metabolic acidosis and increased lactic acid.
-Check ABGs and Lactic Acid level
-Nonpulsatile blood flow throughout the whole body. Some metabolic acidosis is unavoidable.
What does it mean if your patient becomes hypertensive during CPB?
-May be d/t SNS stimulation or hypothermia
-Ensure adequate anesthesia (may need Fentanyl)
-HTN can decrease the ability of the perfusionist to flow.
-Need to dec SVR
-ACT maintained >400. Checked by perfusion while on pump
What are the benefits of hypothermia?
-Decreased metabolic rate and oxygen requirements
-Protects organs from ischemia
What are the disadvantages of hypothermia?
-Coagulation abnormalities
-Possible microbubble formation during rewarming
-O2Hb curve shifts LEFT, reducing peripheral O2 delivery (ok d/t decreased requirements)
