Cardiac anesthesia 2 Flashcards
Patient preparation prior to induction includes
oxygen via nasal cannula (NRB facemask if respiratory distress)
evaluate need for mild sedation
line placement
baseline ABG and baseline activated clotting time
cross matched blood
place external defibrillation pads prior to induction
make sure team is rolling back
Evaluating the need for mild sedation includes
limiting or avoiding versed based on age & cognitive state preoperatively
fentanyl preferred
Line placement prior to induction includes
2 PIVs & arterial line
typically cordis & SWAN placed after induction in stable patients
Intraoperative preparation & positioning includes:
supine with legs padded foam head support arms tucked at sides and padded check lines prep area: from sternal notch to toes Foley (hook up bladder temperature) fluid & under-body forced air warmer rapid infuser (Belmont or "Level-1") drips spiked and ready to go
The prep area includes
sternal notch to toes
The best place to measure temperature is
bladder temp
Describe the use of propofol as an induction agent.
use safely in patients with ischemic & valvular heart disease
biggest challenge is hypotension
Describe the use of etomidate as an induction agent.
may be less likely to cause hypotension than propofol
Describe the use of ketamine as an induction agent.
CV effects are advantageous
biggest challenge is CV stimulation
Avoid ________ during induction and on CPB!!!
N2O
Volatile anesthetics produce dose dependent
global cardiac depression
The negative effects of volatile anesthetics are due to
alterations in intracellular Ca++
Volatile anesthetics are responsible for sensitizing the myocardium to the effects of _____ in varying degrees
EPI
Volatile anesthetics may prevent or facilitate _______ during myocardial ischemia or infarction
atrial or ventricular arrhytmias
The perfusionist has a vaporizer on the bypass machine
and thus you should turn off your vaporizer
Volatile anesthetics produce weak coronary
artery dilation and depresses baroreceptor reflex control of arterial pressure
Pre-incision hypotension considerations include
lack of stimulation
systemic pressure support
risks involved with vasoconstrictors
recall rare at this point, unless severe hypotension occurs in the face of purely opioid technique
For induction it is important to proceed
slowly and know your plan
it is not the drug but the way it is given that is important
The induction technique may include
either high versus low dose narcotics work
use propofol or other induction agent with low dose narcotics
If you anticipate a difficult airway, do not hesitate to
do an awake intubation
-a well planned, well topicalized patient provides the smoothest induction
Post induction tasks include
central line (if not placed pre-op) OG then TEE
Veins that are harvested include
arterial and saphenous veins
Incision time to bypass is intense
surgical stimuli
hypertension may develop- deepen anesthetic, vasoactive agents- NTG/NTP
_______ can be significant with incision
bleeding
Considerations for incision include
identifying and localizing ischemia
drop the lungs for sternotomy
Prior to bypass, the patient should be
anticoagulated with heparin
Heparin works by
binding to antithrombin III and potentiates its natural anticoagulant properties
Heparin should be administered via
CVP or directly into RA
The dosing of heparin is
weight based dosing at 300-400 units/kg- wait 3-5 minutes for ACT
Normal ACT & CPB ACT:
Normal is 130 secs or less (80-120)
ACT of >400-450 for bypass
With heparinization, _________ can decrease
SVR & BP can decrease by 10-20%
Special circumstances in which heparin should not be used includes
ATIII deficiency- pt unresponsive to heparin; FFP can be given or thrombate III
heparin-induced thrombocytopenia, antiplatelet, antibodies which lead to platelet aggregation and potentially life threatening thromboembolic events
The ACT needs to be
> 400 to go on CPB
-give heparin BEFORE any cannulas are placed
Cannulation of the aorta (arterial) and RA (venous) considerations include
must drop the pts BP for aortic cannulation (systolic <90)
BP might drop and/or arrhythmias can occur while placing venous cannula
the perfusionist can give fluids via the arterial line
Pre bypass and post heparinization medications include
medicate patient with midazolam and fentanyl
If BP is too high during cannulation of the aorta,
aortic dissection can occur
Cannulation of the coronary sinus for retrograde cardioplegia includes
similar effects to cannulation of the aorta & RA with a drop in BP
Frequently encountered problems on bypass include
arrhythmias heart failure hypertension hypotension heart failure bleeding :sternotomy lacerates RV or aorta
Hypertension during _______ is most concerning
aortic cannulation d/t risk of aortic dissection
Hypotension prior to bypass may be treated with
volume through aortic line via pump
Arrhythmias are usually related to
cardiac manipulation and cannulation
-may be the first sign of myocardial ischemia
Transitioning to bypass involves the perfusionist opening
venous clamp and allowing blood to drain passively into venous reservoir which immediately begins to cool patient
When the patients goes to bypass, the arterial line
tracing goes flat but ECG is still present
Prior to going on bypass pull back
2-3 cm on PAC so it is no longer in pulmonary artery and won’t cause obstruction
When transitioning to bypass, look for
head for swelling- indicate proper placement of venous catheter
check pupils & BIS–> thrombus
Drugs to consider when transitioning to CPB include
give muscle relaxant to prevent shivering or if mixed venous gas is going down (70-80 is desired)
give amnestic drug
close down fluids
CVP on bypass should be
0-5 possibly even negative
______ will decrease on bypass but a marked decrease is concerning
Cerebral oximetry
For adults, the CPB machine is primed with
1500-2500 mL of balanced electrolyte solution
Albumin, heparin, mannitol, and NaHCO3- is often added to
increase osmolality, reduce edema, and promote diuresis
The CPB machine causes significant
hemodilution and a decrease in oxygen carrying capacity occurs
Typically a hematocrit of _____ is acceptable when patients are on bypass
20%
Hemodilution is associated with
decreased viscosity, decreased SVR, and promotes blood flow to tissues
Describe the path of cardiopulmonary bypass.
arterial inflow–> filter–> flow meter–> oxygenator–> heat exchanger–> pump–> bubble detector–> reservoir–> SVO2–> venous return line
Cardioplegia is
cold- at 4 degrees C
contains K+- 26 mEq/L
The potassium in cardioplegia causes
depolarization of the heart
The cold for cardioplegia reduces
metabolism of the heart
vfib occurs at 25-30 degrees C
Retrograde cardioplegia is infused via
the coronary sinus
Issues related to CPB include
hypotension renal ischemia CVA air emobli introduced into CPB system thromboyctopenia increased inflammatory response altered post-op mental state "pump-head"
Renal ischemia related to CPB occurs due to
hypo-perfusion and/or hemodilution
A CVA while on CPB occurs from
thrombus in CPB system (clot or foreign object)
Hypotension on CPB is related to
decreased SVR
________ failure is mot common after bypass
kidney
Cardiac surgery inflammatory response is a result of
surgical factors
perfusion factors
pharmacology
& technological
