-
What 2 drugs classes comprise the mainstay of medical management for ischemic HD pts?
BB and nitrates
-
Syndrome X
- angina with normal coronaries and lack of extra cardiac etiology of angina
- ? due to coronary microvascular flow
-
Stunning
- ischemic symptom
- brief period of myocardial ischemia leads to cardiac dysfunction for several hours
- occurs during reperfusion phase
- in CT surg pts often occurs after CPB when heart is reperfused
- generally transient
-
Hibernation
- Symptom of ischemia
- Adjacent to an area of infarction in an area of myocardium with impaired function
- Occurs in setting of impaired myocardial blood flow
- Transient
-
Preconditioning
Brief intermittent period of ischemia confers protection against subsequent larger ischemic insult
-
LCA 2 branches
LAD (anterior) and Lcx (lateral)
-
-
What factor can cause a 200% increase in cardiac oxygen demand?
contractility
-
After contractility, what factor causes the next greatest increase in O2 demand?
HR
-
What factors affect O2 demand?
HR, wall tension (diastolic volume and after load), contractility
-
What factors affect O2 supply?
arterial O2 content (anemia, hypoxia), O2 extraction (left shift on oxyHbg dissoc curve), coronary blood flow
-
Papillary muscles
- Pull valve cusps downward and together at onset of ventricular contraction
- Prevent back flow of blood into the atria
-
systolic anterior motion
- form of papillary muscle dysfunction
- valve leaflets move back into the atria during systole
- regurg results
-
2 AV valves
- tricuspid (3 cusps)- right side
- mitral (2 cusps)- left side
-
Semiluminar valves
- Pulmonary (right side)
- Aortic (left side)
- both have 3 cusps normally
-
Most common congenital heart issue
Valve disease
-
Most common valve issue
AS
-
What is considered severe AS?
- valve area < 0.8 cm2
- or
- systolic gradient > 50 mmHg
-
Major principles in management of AS
- Maintain NSR to allow for adequate filling
- Avoid hypotension and hypertension
- Maintain adequate volume
-
Issues associated with AS (changes to the heart)
- LVH (to try to maintain LV output)
- Increased dependence on atrial kick for filling
-
Hypertrophic CMP
- Ventricular hypertrophy without an obvious cause such as AS or HTN
- Genetic- AD
- Manage like AS
-
General principles for management of regurg pts
- fast full forward flow
- afterload reduction is beneficial
- Avoid bradycardia and hypovolemia
-
Most common cause of AR and MS
rheumatic heart disease
-
-
-
Management of MS
- Maintain NSR
- Avoid tachycardia
- Maintain euvolemia
-
Why is PH often associated with MS?
Blood backs up into LA which causes pressure build up in pulm vein
-
things to check prior to induction
- availability of blood
- surgeon present
- defibrillator in room
-
Pts at high risk for ischemia during induction
- AS, MS
- LM disease or LM equivalent disease
-
LM equivalent disease
High grade stenosis of both LAD and LCx
-
Preferred opioid and dose used for induction
- fentanyl due to bradycardia SE, little effect on contractility
- 3-10 mcg/ kg
-
How does induction for cardiac surgery differ from regular induction
Usually use higher dose opioid (3-10 mcg/ kg fentanyl) and lower dose hypnotic (1-2 mg prop)
-
How does the dose of volatiles used in cardiac surgery differ from standard dosing?
- Lower volatile doses to avoid tachycardia and hypotension
- Usually iso is used
-
Why is N20 not used in cardiac anesthesia?
Avoid expansion of air bubbles in bypass machine
-
When using the US machine to insert a CL, is the artery or vein compressible?
Vein
-
Fast track cardiac anesthesia
- extubation 8 hours post-op
- most cardiac surgery these days
- lower dose narcs are used, limit fent to 10-15 mcg/ kg
-
Preincision
-level of stimulation
-anesthetist duties
- low stim
- check PPP
- drop OGT and decompress stomach
- TEE probe is inserted
- obtain baseline labs (ACT and lytes)
- start antibiotics
-
Anesthetist duties during incision
- Ensure adequate level of anesthesia- sternal split is very stimulating
- Avoid HTN
- Deflate lungs (detach from vent)
- Once chest open switch to internal paddles
- Ensure blood is available
-
Amps used for internal defib
10 milliamps
-
What occurs after incision?
- IMA and radial artery dissection
- then sympathetic nerve dissection (can be very stimulating)
-
How do we prepare for bypass?
-
How does heparin work?
binds to antithrombin 3
-
heparin half life
2.5 hours
-
goal ACT prior to bypass
> 300 sec
-
Normal ACT
105-167 seconds
-
Sling placement
- Goes behind heart to allow it to be lifted
- Can cause extreme HD changes (flat line)
- Not treated if due to manipulation
-
Goal BP during arterial (aortic) cannulation- why?
- Goal SBP <= 90 mmHg
- Risk of aortic dissection
-
Goal BP during venous cannulation
SBP <= 90 mmHg
-
How would know you aortic dissection occurred during cannulation?
- There's a pressure sensor on the aortic cannula (goes to perfusionist)
- If aortic pressure reads 20 mmHg but radial reads 60 mmHg that could mean possible dissection
-
Risks associated with venous cannulation
- Atrial dysrhythmias- not treated as about to go on bypass
- Occur as cannula is placed in or close to atria
-
Communication during cardiac surgery
Closed loop!!
-
Prebypass checklist
- Adequate anticoagulation
- Adequate anesthesia
- Cannulation proper and patent
- Infusions off
- Monitors in place
- Foley in
- Check pupils (check for eye swelling 2/2 misplaced venous cannula)
-
How does bypass affect the concentrations of our drugs?
CPB solution dilutes our drugs, may need to give more
-
CPB checklist
- Face- color, temp, symmetry (potential misplaced venous cannula)
- Eyes- pupils equal and symmetric
- Pump lines- visible color difference btw arterial and venous blood
- Art and pulm BP
- Stop ventilation once aortic ejection ceases
-
Normal arterial BP on bypass
- Will see mean only
- 30-60 mmHg
-
Normal PA pressures on bypass (if monitored)
< 15 mmHg
-
What happens once on CPB
- stop ventilation
- induce mild to moderate hypothermia
- aorta is cross clamped (note on anesthesia record)
- cardioplegia is infused
-
cardioplegia solution
- differs by inst
- high K sol'n that stops the heart
-
Distal vs. proximal anastamoses
- Distal- on heart, not aorta
- Proximal- on aorta
-
What occurs after the distal anastamoses are completed
Start to rewarm pt, need normothermia prior to coming off of bypass
-
why do we tend to see hyperglycemia while on CPB? How do we manage it?
- D/t cardioplegia solution
- Check BS q 20 mins
- Insulin gtt
- Goal BS < 150
-
Why is checking UO q 30 minutes important?
Ensure adequate renal perfusion
-
CPB termination
- Rewarm pt
- Remove air PRN (more likely to occur with valve surgery as the heart is open)
- Optimize metabolic condition
-
Partial bypass
- Occurs when weaning pt off of CPB
- Some of venous blood flows into bypass, some into heart
-
When do you start reventilating the pt
Once blood is again flowing directly to the heart and lungs
-
When is CPB terminated
SBP > = 90 mmHg or < 1L pump flow
-
In terminating CPB, the key factor is optimal ____.
Preload
-
How can we assess preload
Via echo
-
The pt no long requires bypass, now what?
- Venous cannula is removed first, then arterial
- Protamine is given
-
Protamine administration
- 1st give test dose of 5-10 mg
- Perfusionist calculates dose
- Surgeon will tell you when to give
- Administer slowly
- Tell surgeon progress of administration (33%, 50%, etc)
-
Protamine complications
PH, systemic hypotension
-
Pump lung
- Severe ARDS
- Occurs 2/2 CPB
- Rarely occurs nowadays
-
Differential dx of LV failure after CPB
- Ischemia
- Inadequate coronary flow
- Valve failure
- Gas exchange issues
- Preload- excessive or inadequate
- Reperfusion injury
-
1st line agents for inotropic support once off CPB
- epi or milrinone
- varies by institution
-
What pts are at risk for RV failure?
PH, MV dz, RV infarct or ischemia, RV outflow obstruction, TR
-
RV failure treatment
- Hyperventilate to lower CO2 and thus lower PVR
- Avoid hypoxemia, acidosis, and N20
- NTG
- optimize preload
- inotropic support with milrinone or dobutamine
-
MIDCAB
- minimally invasive CPB
- no bypass
|
|
