Cardiac Anesthesia Flashcards
Preop Evaluation
Cardiac history - disease severity & hemodynamic status
- EKG, stress ECHO, cardiac catheterization
- Baseline status (EF, LVEDP, pulmonary HTN, valvular or congenital lesions, CHF)
Past surgical history - previous sternotomy (scarring), vascular surgery, graft sites, or Protamine administration
Angina presentation
Dysrhythmias
METs (exercise tolerance)
Past medical history - TIA or CVA (carotid studies before CV surgery to preserve CBF)
Comorbidities: HTN, COPD, T2D (infection risk), vascular disease, renal or liver insufficiency
Medications - anticoagulants, antianginal, β blockers, insulin, ACEi, ARBs
What’s the mortality percentage after an intraop MI?
50%
Cardiac Catheterization
Locates potential blockage(s)
EKG
Recent MI
Assess rate & rhythm
ECHO
EF % Valve function Wall abnormalities Aorta calcification Atrial thrombus
Coagulation Studies
PTT/PT
Baseline ACT
Platelet number & functionality
TEG (thromboelastogram)
Chest X-ray
Aorta calcification
Cardiomegaly
Edema
Renal Function
Decreased function ↑postop mortality
Liver Function
Cardio-pulmonary bypass ↓liver perfusion
↑hypoperfusion risk d/t ↓splanchnic flow on CPB
What medications to continue leading up to cardiac surgery?
Antiarrhythmics
Ca2+ channel blockers
β blockers
Nitrates
Ø antiplatelet/anticoagulants
Cardiac Anesthesia Goals
- ↓cardiac oxygen utilization (MVO2)
- Maintain O2 supply
- Anticoagulation
- Normotensive w/in 20% baseline
↓MVO2
Anesthesia ↓SNS
Hypothermia - alters platelet function & ↓fibrin enzyme function, inhibits thrombin formation, & ↓metabolic demand, ↑ischemia tolerance
Cardioplegia K+ continuous admin during cross-clamping → electrical & mechanical activity ceases (renal patients hyperkalemia)
Empty cardiac chambers Ø LV distension
Maintain O2 Supply
Maximize O2 carrying capacity & flow
Optimal Hgb/Hct 30%
Hemodilution (dilutes clotting factors) = less viscous ↓blood viscosity ↑flow
Acceptable perfusion pressures & flow
Hypotension
↓end-organ perfusion
Hypertension
Disrupt myocardial balance
↑MVO2 (demand)
Monitoring
Pox
NIBP + A-line
EKG (ensure correct placement especially leads II & V5)
Temp probe (Foley best site for core temp w/ less impact from cooling, but delayed reading)
Foley
CVP or PA cath
NIRS/BIS on before induction to provide baseline
TEE
Transesophageal Echo
Evaluate preload (ventricular filling)
Volume status
Estimate CO
Assess ventricular systolic/diastolic function
Valvular pathology
Aorta calcifications
Cardiac tamponade
Atrial thrombus
Assess air present in heart prior to closure → de-airing maneuvers
Anastomosis evaluation after patient off bypass
When to admin volume, start vasoactive gtts, re-examine graft, & assess surgical repair
TEE Contraindications
Esophageal pathology (i.e. alcoholic varices) Empty stomach before placing the probe - After asleep place down OG to suction
Swan Ganz
Pulmonary artery catheter
Typically placed in the R IJ (most direct route)
Cordis placed after induction as introducer to float the PA through when needed
TEE > PA cath
PA Catheter Insertion
R Atrium
5mmHg
PA Catheter Insertion
R Ventricle
15-30 / 0-8
PA Catheter Insertion
Pulmonary Artery Normal Pressures
15-30 / 5-15 mmHg
PA Catheter Wedge Pressure (PAWP)
Reflects the L ventricle pressure
Dampened waveform
Balloon inflated & catheter wedged into pulmonary artery distal branch
= 10
Swan Ganz Complications
Ventricular arrhythmias
Heart block (especially in patient w/ pre-existing L bundle branch block)
Pneumothorax (most common w/ subclavian approach)
Unintended arterial puncture (most common acute injury)
Valve damage
Hematoma/thromboemoblism
Vascular injury (localized hematoma)
Thorax perforation → hemothorax
Pulmonary artery rupture → blood noted in ETT
Cardiac tamponade
Bloodstream infection
Aortic or Mitral Stenosis Valve Repair
Maintain preload (volume) Maintain SVR (afterload) Lower HR < NSR 50-80bpm
Aortic or Mitral Regurgitation Valve Repair
Maintain preload (volume)
↓SVR
↑HR to promote forward flow & prevent regurgitation
Monitoring, Equipment, & Drugs (Infusions/Emergency)
Pacemaker
Infusions:
- Nitroglycerin or sodium nitroprusside
- Epi or NE
- Phenylephrine
- Dopamine/Dobutamine
- Antiarrhythmics (Esmolol, Lidocaine, Magnesium, Amiodarone)
- Insulin
Coagulation monitoring ACTs or TEG/ROTEM
Emergency drugs - Atropine, Glycopyrrolate, Ephedrine, Succinylcholine
Type & cross 4 units PRBCs available in OR
What neuromuscular blocking agent should be avoided in cardiac anesthesia? Why?
Pancuronium
Vagolytic ↑HR d/t reflex tachycardia
When to administer antibiotics?
Pre-incision & post bypass
What diagnoses fibrinolysis? When to start monitoring to be effective?
Thromboelastogram (TEG)
BEFORE going on CPB
Preop Anesthetic Considerations
How to prepare the patient for induction?
Oxygen via NC or non-rebreather
Limit or avoid Midazolam
Place lines before induction - PIV x2, A-line, CVP, PA catheter (after induction in stable patients)
Discuss access when surgical team regarding A-line & vein or graft harvesting sites
Obtain baseline ABG & ACT
Place external defibrillation (R2) pads on prior to induction
Intraop Anesthetic Considerations:
Positioning, Incision, & Temperature
Positioning - supine w/ arms tucked
Ensure lines infusing, A-line waveform present, & blood return +
Preop area from sternal notch to toes (saphenous vein graft)
Fluid warmer
Under-body forced air warmer
Rapid infuser available
Infusions set-up, programed, connected to the patient, & ready to go
Volatile Anesthetics
Dose-dependent cardiac depression
Negative effects d/t intracellular Ca2+ alterations
Sensitizes the myocardium to Epi
Prevent or facilitate atrial or ventricular arrhythmias during myocardial ischemia or infarction
Produces weak coronary artery dilation & depresses baroreceptor reflex control (arterial pressure)
Induction
Narcotics CV stable
- High dose
- Low dose w/ induction agent
Awake intubation when difficult airway anticipated
Post-induction place central line, OG, & TEE (stable patients when not placed pre-induction)
What to anticipate pre-incision?
Lack stimulation → HoTN
Systemic pressure support
Recall rare
Incision → Bypass
Sternotomy - drop the lungs
Discontinue or ↓pressors prior to sternotomy
Intense surgical stimulation w/ incision
HTN → deepen the anesthetic & consider vasodilator agents
Anticipate significant bleeding (consider previous sternotomy effects & anticipate response)
Identify & localize ischemia
Arterial and/or saphenous veins harvested
Pre-Bypass
Administer Heparin
*Drawn up BEFORE sternotomy → available in case need to crash onto bypass
Check ACT
Heparin MOA
Binds to antithrombin III & potentiates natural anticoagulant properties
Heparin Dosage
300-400 units/kg
Heparin Administration
Via central line BEFORE cannulas placed
*Check ACT 3-5min after administration
Normal ACT
< 130 seconds
80-120 seconds
ACT range required to start cardio-pulmonary bypass?
> 400-450
Response to Heparin
↓SVR/BP 10-20%
HIT
Heparin-induced thrombocytopenia
Antiplatelet antibodies → lead to platelet aggregation & potentially life-threatening thromboembolic events
Platelet count < 100,000
*Previous Heparin exposure
Check antibodies to antiplatelet factor IV
Heparin Alternative
Bivalirudin
Direct thrombin inhibitor
Pre-Bypass (Post Heparinization)
↓BP before aortic cannulation to prevent aortic dissection
TEE to assess Ca2+ deposits or plaques present in aorta
Aorta cannulation (arterial) 1st
- Perfusionist able to administer fluids through
R atrium (venous) cannulation 2nd
- HoTN and/or arrhythmias w/ venous placement
Coronary artery sinus cannulation - retrograde cardioplegia ↓BP
Pre-Bypass Complications
Arrhythmias - cardiac manipulation & cannulation; potentially 1st sign myocardial ischemia
HTN especially during aortic cannulation
HoTN - admin volume via aortic line or pump; consider pressors
Heart failure
Bleeding - sternotomy lacerates R ventricle or aorta
Transitioning to Cardio-Pulmonary Bypass
Perfusionist opens venous clamp to passively drain blood into the venous reservoir
Begins active patient cooling
A-line flat
Pull back pulmonary artery catheter 2-3cm into R ventricle
Assess for swelling or blanching (indicates improper venous catheter placement Ø adequate drainage from the head)
Pupils & BIS
When to stop the ventilator?
When transitioning to bypass once the heart volume emptied
Bypass at full flows discontinue IV fluids
Bypass Numbers
Pump flow 2.5-3L/min or 50-60mL/kg
Goal MAP 65-70mmHg (valve repair 50-60)
CVP 0-5 or (-) w/ vacuum assist to remove the blood
Mixed venous saturation 70-80%
Cerebral oximetry ↓normal when transition to bypass
Pump Prime
Ask perfusionist
1,500-2,500mL balanced electrolyte solution
Crystalloid
Albumin, Heparin, bicarbonate, & Mannitol (↑osmolality ↓edema → promote diuresis)
Corticosteroids, antifibrinolytics, & blood products
Anticipated patient response to going on bypass
Dilutional effect ↓viscosity (cooling ↑viscosity) ↓SVR → promotes blood flow to tissues
Catecholamine dilution → administer + inotropes
Hemodilution ↓O2 carrying capacity
Cardio-Pulmonary Bypass Goal
Bloodless field
Still heart (not beating)
Quiet <3
Hct %
20% acceptable
Goal 25-28%
Optimal viscosity = 30%
Admin PRBCs after patient off bypass
How often to check labs after bypass initiated?
Q30min
ABG & ACT
Cardioplegia Solution
4°C Reduces cardiac metabolism Contains KCl 26mEq/L → depolarization Glucose 43.9g/L Mannitol 12.5g/L NaHCO3 2.67mEq/L Methylprednisolone Na+ 1g/L Normosol-R pH 7.6 Osmolality 480mOsm/Kg H2O
When does V-fib occur?
Hint: Temperature °C
25-30°C
When does the heart arrest?
DIASTOLE phase
Cardio-Pulmonary Bypass Complications
HoTN ↓SVR
Renal ischemia d/t hypo-perfusion and/or hemodilution
CVA d/t thrombus in bypass pump (clot or foreign object)
Air emboli
Thrombocytopenia → extrinsic & intrinsic coagulation pathways activated
↑inflammatory response
Altered postop mental status “pump head”
What patients are at an ↑risk to experience postop renal compromise?
Pre-existing renal conditions
Pump run time > 1hr
Elderly
Cerebral Protection Mechanisms:
Hypothermia
Blood gas management
Adequate BP
BIS & cerebral oximetry
*Emboli 1° culprit → CNS complications
When does re-warming the patient begin?
During the last anastomosis
Turn on warming blanket
Indicates close to coming off bypass
30-40min to re-warm patient
Re-Warming
Begins PRIOR to aortic cross-clamp removal
When last distal anastomosis in angioplasty procedure
All valve sutures are in & knots are being tied down
↑temperature ___°C per ___-___ minutes
↑1°C per 3-5 minutes
What to anticipate w/ re-warming?
Recall risk - administer amnestic & neuromuscular blocker
Vasodilation ↓BP
Preparation to come OFF bypass:
Core temperature > 35°C (target 37°C) Check labs: ABG, ACT, electrolytes, CBC+ 1. Correct K+ 2. Acid base balance 3. Hct% Inflate the lungs w/ manual ventilation Perform de-airing maneuvers Remove aortic cross-clamp Ensure HR > 90bpm (pacing as required) Perfusionist slowly clamps the venous line & turns down flows to allow R atrium to fill - Monitor PA & A-line pressures (anticipate ↑) Pump off & venous cannula clamped = OFF bypass Monitor CO via TEE, PA (re-float Swan Ganz), A-line ↑SvO2 indicates ↑O2 demand or ↓delivery Shivering → administer muscle relaxant Turn ventilator on Perform recruitment maneuvers PRN
Hyperkalemia Treatment
CaCl 500mg
Magnesium
2-4 grams
↓A fib risk
How to restart the heart?
Surgeon administers “hot shot” warm cardioplegia solution w/o K+ after removing the cross-clamp
Unsuccessful?
Attempt internal shock or pacing
Blood Glucose Goals
< 200
180-200
↑risk sternal wound infections w/ uncontrolled blood glucose levels
Diabetic response to bypass:
↑glucose on bypass
Regular insulin gtt
When providing recruitment breaths & manual ventilation what does the anesthetist need to monitor for?
Pressures < 30cmH2O
Internal mammary/thoracic artery anastomosis → LAD
Aortic Cross-Clamp Time
Prolonged cross-clamp time α postop morbidity
Normal patient response to aortic cross-clamp removal:
Paradoxical myocardial damage & limit recovery extent d/t free radicals released from the site (anaerobic metabolism)
Slow release
As blood flow returns, metabolites will be washed out
Aortic Cross-Clamp
Complications
Hemorrhage at the cannulation site
Atheromas (clots) dislodgement
Aortic dissection
What does ST elevation indicate?
Myocardial supply & demand mismatch → ischemia Air trapped in the heart - Notify the surgeon - De-airing maneuvers - Needle insertion by surgeon
Open Chest Defibrillation
10-30 joules
Assessments when coming OFF bypass:
Contractility - heart filling & rhythm
TEE - volume, wall motion, valve function
Inspect for bleeding
Systemic α pulmonary artery pressure
Protamine Dosage
1mg per 100 units Heparin
Protamine Administration
SLOWLY via peripheral line
Potential to cause pulmonary HTN & R heart failure
Post-Bypass Complications
Recall Neurocognitive changes Bleeding - ↓clotting factors, fibrinolysis, thrombocytopenia, surgical blood loss, transfusion reaction, vessel trauma, & anaerobic metabolites Organ hypo-perfusion Emboli or thrombi Systemic inflammatory response Residual hypothermia
Protamine
Multiple low-molecular weight proteins derived from salmon sperm
Neutralizes & reverses Heparin effects → Heparin-Protamine complex
Protamine Half-Life
30-60 minutes
Potential to experience “Heparin rebound”
When to check ACT after Protamine administration?
15-30 minutes
Protamine Type I
Allergic Reaction
Histamine release → HoTN
Prevent w/ slow administration over 20-30min
Treat w/ volume or inotrope
Protamine Type II
Allergic Reaction
IgE antibody mediated
Bronchoconstriction presents as anaphylactic reaction
Protamine Type III
Allergic Reaction
Heparin-Protamine complex lodges in the pulmonary circulation
→ pulmonary HTN & R ventricle failure
Prevent w/ administering slowly via peripheral vein
Closing the Chest
Cardiac tamponade type scenario where the heart squished & patient unable to tolerate → open back up
↓BP
Monitor TEE & hemodynamics
Transport to ICU
Ambu-bag O2 tank Monitors Emergency drugs Keep surgical table sterile Transport assistance Re-check breath sounds Attach to ventilator 100% FiO2
