Week 7 - Cardiac Anesthesia Flashcards
What is included in the preop evaluation for a cardiac patient?
Assessment of cardiac characteristics:
- cardiac history (acute unstable angina, acute MI, CHF, shock)
- coronary lesion (left main high grade lesion, triple-vessel disease, diffuse lesion)
- ventricular function
- valvular disease
What are some common comorbidities in cardiac patients?
- Carotid and cerebrovascular disease
- Diabetes
- Renal disease
- Pulmonary disease
- Peripheral vascular disease
What are the most important factors in balancing myocardial oxygen supply and demand?
Heart Rate and Left Ventricular Pressure
What medications should cardiac patients continue taking preoperatively?
Beta Blockers
Calcium Channel Blockers
ASA
Long-acting insulin
What medications should cardiac patients hold preoperatively?
Diuretics
Renin-Angiotension-Aldosterone System inhibitors (ACE/ARB)
Warfarin
Short-acting insulin
When should cardiac patients stop taking their ACE/ARBs prior to surgery?
24 hours prior to surgery
*except Captopril can be held 12 hours prior
ACE/ARBs may cause vasoplegic syndrome – unexpected refractory hypotension under GA with MAP less than 50 mmHg, cardiac index > 2.5 L/min, and a low systemic vascular resistance despite vasopressor admin
What surgical risk assessment scales are used preoperatively for cardiac patients?
The Society of Thoracic Surgeons Cardiac Surgery Risk Score – allows calculation of pt’s risk of mortality and morbidities for the most commonly performed cardiac surgeries
European System for Cardiac Operative Risk Evaluation II – predicts risk of in-hospital mortality after major cardiac surgery
What is the most sensitive clinical monitor for detecting wall motion abnormalities cause by myocardial ischemia?
TEE
*completed before CPB to identify baseline pathology and function
What are the pros and cons of the different induction agents for cardiac surgery?
- Etomidate causes less myocardial depression than propofol, but the adrenal suppression cause by etomidate is subject for debate
- Etomidate provides more stable hemodynamic parameters compared to propofol in pts with poor LV function
- Pts with severe LV dysfunction may require a primary narcotic technique since all volatile agents cause some degree of myocardial depression and afterload reduction
*typical to do large dose of versed and fentanyl for induction – slower but hemodynamically stable
What are the hemodynamic goals pre-bypass in cardiac surgery?
Maintain perfusion pressure
Lower cardiac oxygen consumption
Increase oxygen supply
What are the hemodynamic goals post-bypass for cardiac surgery?
Mean 60-70 mmHg
HR 80-90 bpm
Cardiac Index >2
What are common medication infusions used in cardiac surgery?
Phenylephrine Norepinephrine Epinephrine Nitroglycerin Nitroprusside Nicardipine Dopamine Dobutamine Tranexamic Acid Insulin Dexmedetomidine
What occurs from incision to bypass in cardiac surgery? What is the anesthetic goals?
Goal: Maintain Hemodynamic Stability
- Incision and Sternotomy: narcotics, esmolol, deepen volatile, additional muscle relaxant
- Harvesting of Grafts (if CABG)
- Heparin 300-400 units/kg (ACT >450)
- Cannulation: aortic cannula, venous cannula, antegrade/retrograde cardioplegia cannula
- before aortic cannulation BP is decreased to SBP 90-100 or MAP <70 to decrease the risk of aortic dissection
What is the typical dose of heparin administered prior to initiation of cardiopulmonary bypass?
300-400 units/kg
- ACT is measured 3-5 min after admin
- Goal ACT is >400 seconds (450 at some places) – normal ACT = 80-120
What are the advantages and disadvantages of using volatile anesthetics in cardiac surgery?
- Potentially cause myocardial depression, vasodilation, and hypotension
- Lower the arrhythmogenic threshold to catecholamines, and don’t provide pain relief in post-op period
- Including volatile agents is associated with better outcome after cardiac surgery than using total IV technique
- Most pts will benefit from myocardial protection of volatile agents (exception is severe LV dysfunction who can’t tolerate further cardiac depression)
- Des and N2O raise PVR, PA pressure, and wedge pressure
Why should nitrous oxide be avoided in cardiac surgery?
Potential for expansion of air introduced into the circulation during bypass
May cause catecholamine release and LV dysfunction
What anesthetic technique facilitates early extubation post cardiac surgery?
Low to moderate dose narcotics (fentanyl 5-20 mcg/kg or sufentanil 2-10 mcg/kg) combined with volatile agent, or TIVA with short to moderate acting drugs such as remifentanil, propofol, or dexmedetomidine
What are the advantages and disadvantages of narcotic use in cardiac surgery?
- Don’t cause myocardial depression
- Maintain stable hemodynamics
- Can cause significant bradycardia, recall, chest wall rigidity, and prolonged intubation
*primary narcotic technique is reserved for hemodynamically unstable pts
What is included in the pre-bypass checklist?
- Anticoagulation (heparin admin, desired anticoag level - ACT >450)
- Arterial cannulation
- Venous cannulation
- Pulmonary artery catheter (if used) pulled back
- Are all monitors/access catheters functional?
- TEE
- Supplemental medications (muscle relaxant, anesthetics, analgesics, amnestics)
- Inspection of head and neck (color, symmetry, venous drainage, pupils)
What are the steps of cardiac surgery on CPB?
- On bypass
- Cross clamp aorta
- Cardioplegia
- Cardiac arrest
- Grafts anastomosis
- Unclamp aorta
- Rewarming
- Wean off CBP
- Protamine
Where is cardioplegia infused during cardiac surgery?
Solution infused either through:
- a catheter placed in the aortic root (cardioplegia moves forward into the coronary arteries – antegrade)
- a catheter placed in the coronary sinus (cardioplegia moves backward into the coronary veins – retrograde)
What is the function of cardioplegia?
- Keeps heart muscle still to allow surgery to be more easily completed
- Greatly reduces the metabolic needs and oxygen requirements of the heart muscle, reducing the amount of ischemia during surgery
*may be infused multiple times during surgery to ensure the heart doesn’t beat
What does intraop management of CPB look like?
- With full flow there will no longer a pulsatile trace on the PA or A-line as blood is now bypassing the lungs
- Stop mechanical ventilation
- Vaporizer if used in attached to the oxygenator inlet of the CPB machine
- Infusion of all IV fluids and most meds stopped (insulin and antifibrinolytics be continued)
- CPB flow is temporarily decreased and aorta is cross clamped (note time)
- Cardiac arrest ensues and cardioplegia is infused (high potassium) and then asystole
- Active cooling may ensue, or allow patients temp to “drift” to ambient.
What is the MAP goal while on CPB?
60 - 80 mmHg
*closer to 80 if pt has preexisting renal insufficiency or known atherosclerosis of carotid or cerebral arteries
How is hypertension and hypotension typically treated while on CBP?
HTN: increasing anesthetic
HoTN: small boluses of phenylephrine (per perfusionist)
What are the physiologic effects of CPB?
- Systemic Inflammatory Response (SIRS)
- Myocardial Injury
- Neurological Deficits: Type 1 CVA, encephalopathy, coma, TIA – Type 2 confusion, agitation, disorientation, memory deficits, seizures (may improve after 3 months)
- Pulmonary Complications (Atelectasis, Acute Lung Injury (ALI), ARDS, hemothorax, pnueomothorax, pulmonary edema)
- Renal Dysfunction (ARF)
- GI system dysfunction
- Coagulopathies
What is included in the discontinuation from bypass checklist?
- Air clearance maneuvers complete
- Rewarming completed
- Address issue of adequacy of anesthesia and muscle relaxation
- Obtain stable cardiac rate/rhythm
- Pump flow and systemic arterial pressure
- Metabolic parameters (normal limits, K+ 4-5.5)
- Ensuring all monitors/access catheters are functional
- Respiratory management (lungs re-expanded)
- IV fluids restarted
- Inotropes/vasopressors/vasodilators prepared
What are the steps of coming off bypass?
- As cardiac chambers are surgically closed, the lungs are inflated to remove air from the heart and pulmonary veins and to assist in filling the heart
- Perfusionist lowers pump flow as surgeon removes aortic cross clamp
- Heart will commonly fibrillate as it is re-perfused, internal defibrillation as indicated
- Antidysrhythmics are often administered (lidocaine 100mg, Mg 1-2mg)
- Optimal HR 80-90, AV asynchronous pacing if needed – change to synchronous mode when cautery use stops
- Delivery of volatile or IV anesthetics
- TEE assessment
- Perfusionist then gradually occludes venous return to facilitate filling of RV, as arterial pressure rises CPB flow is gradually decreased and stopped
What is the blood pressure goal during decannulation after CBP?
SBP 90 or MAP of 70 mmHg
*to decrease bleeding
What is the dosing of Protamine after decannulation of CBP?
1mg Protamine to reverse every 100 units of heparin given
- normal heparin dose of 30,000 units would require 300mg protamine
- ACT is taken 3-5 min after protamine to confirm ACT returns to baseline
- Give slow (mild hypotension) – anaphylaxis
What occurs with cardiac tamponade?
Accumulation of blood in pericardium –> decreased SV –> compensatory rise in right atrial pressure –> septal shift to left –> diminished LV filling –> HoTN, systemic acidosis, myocardial ischemia, reduced CO
What is Beck’s Triad?
Clinical Presentation of Cardiac Tamponade:
- Hypotension
- Jugular Distension
- Distant muffled heart sounds
What are the symptoms of cardiac tamponade?
Beck’s Triad (HoTN, jugular distention, and distant muffled heart sounds)
Pulsus Paradoxus: >10 mmHg decrease in SPV that occurs during inspiration
How is cardiac tamponade diagnosed?
Chest X-Ray
Echo
*typically occurs 12-24 hours post cardiac surgery
What regional anesthesia techniques can be used in cardiac surgery?
- Central Neuraxial Block: thoracic epidural, spinal anesthesia
- Peripheral Neuaxial Block: thoracic paravertebral block, intercostal nerve block
- Field Block
What are the benefits of regional anesthesia in cardiac surgery?
Decreased opioid consumption Pain control Decreased surgical stimulus Fast track Decreased respiratory complication Hemodynamic stability Decreased dysrhythmias
What are the risks of regional anesthesia in cardiac surgery?
Hematoma Infection Local anesthetic toxicity Hypotension Bradycardia
What are the differences for Off-Pump cardiac surgery?
- Good communication with surgeon
- Require more volume replacement
- Maintain normothermia, less neurological protection
- Anticoagulation is necessary, but goal is usually at 300 ACT
- Antifibrinolytics are not routinely used
- MAP is kept relatively high during distal anastomosis (90-100)
- Map is lowered with aortic anastomosis (60-70)
Compare and contrast on-pump vs off-pump cardiac surgery
- Surgical time: off-pump shorter
- Transfusion rate: off-pump lower
- Hospital & ICU stay : off-pump shorter
- Neurological damage: off-pump lower
- Overall perioperative complications: off-pump = on-pump
- Graft-patency rate lower for off pump at three months: off-pump 88% vs. on-pump 97%
- Similar early and late graft patency, incidence of recurrent or residual myocardial ischemia, need for reintervention, and long-term survival
