Anesthesia for Coronary Artery Bypass Surgery

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Anesthesia for Coronary Artery Bypass Surgery

• Vincent Conte, MD
• Clinical Assistant Professor
• FIU College of Nursing
• Anesthesiology Nursing Program

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• Cardiopulmonary
• Bypass
• Machine

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Cardiopulmonary Bypass

• CPB is accomplished through the use of a CPB
  Pump/machine
• Its basic function is to act like the heart and
  lungs while the heart is made still for surgery
  to proceed
• The main difference is that the flow from the
  pump is NON-PULSATILE vs. normal pulsatile flow
  from the heart

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Cardiopulmonary Bypass

• CPB is characterized by gravity drainage of blood
  from the venae cavae into an OXYGENATOR followed
  by its return to the arterial system, usually the
  ascending aorta, by means of a ROLLER PUMP
• In the presence of a competent Aortic Valve, the
  heart is excluded from the patients circulation

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CPB

• If the aortic valve is NOT competent, then the
  aorta must be CROSS-CLAMPED between the valve and
  the INFLOW cannula
• If this step is NOT done, then blood would flow
  into the heart and the heart would NOT be
  isolated from the circuit and work would be
  impossible to proceed

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CPB

• When the heart is isolated from the circulation,
  Total Cardiopulmonary Bypass is present and
  ventilation of the lungs is no longer necessary
  to maintain oxygenation
• At this point the ventilator can be turned off
  and the reservoir bag is usually removed with
  your pop off valve in the wide open position
• The circuit is open to room air pressure so no
  pressure can build in the lungs, making them
  expand and getting in the way of the surgical
  field

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CPB

• The CPB machine has five basic components
• A VENOUS RESERVOIR
• An OXYGENATOR
• A HEAT EXCHANGER
• A MAIN PUMP
• An ARTERIAL FILTER

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CPB

• Prior to its use, the CPB machine must be primed
  with fluid (1200-1800 mL) that is devoid of
  bubbles
• Usually a balanced salt solution is used to flush
  the machine, but sometimes Albumin or Hespan is
  added
• Blood is also used as a priming solution for
  small pediatric patients or for anemic adult
  patients

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CPB

• At the onset of bypass, hemodilution usually
  decreases the hematocrit to about 22-25 in most
  patients
• That is why in the more critically ill or anemic
  patients, blood is used for priming the CPB
  machine to avoid too drastic a drop in hematocrit
  and consequently compromising O2 delivery and
  leading to Ischemia

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Reservoir

• The reservoir of the CPB machine receives blood
  from the patient via one or two venous cannulas
  placed into the Right atrium or the Superior and
  Inferior vena cavae
• Blood flows to the reservoir by gravity drainage
  so depending on the rate of flow, you may see the
  pump tech raise or lower the reservoir at
  different times during the case

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Oxygenator

• Blood comes from the bottom of the reservoir and
  passes next through the OXYGENATOR
• There is a bloodgas interface and oxygen is
  bubbled through the blood as it flows passed the
  interface
• A volatile anesthetic is also frequently added at
  the oxygenator gas inlet to allow for control of
  BP while the patient is on the CPB machine

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Oxygenator

• CO2 is usually eliminated at the same site as
  where the O2 is added by allowing it to flow down
  its concentration gradient
• There is usually a regulator that allows the pump
  tech to set the concentration of O2 at the point
  of mixing so as they monitor the PaO2 by ABG
  analysis, they can adjust the O2 flow to maximize
  PaO2 as needed

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Heat Exchanger

• Blood from the oxygenator enters the heat
  exchanger
• The blood is then either cooled or warmed
  depending on the temperature of the water flowing
  through the exchanger (4-42 degrees C)
• Heat transfer occurs by conduction
• To cool the blood, ice is added to the outer
  chamber of the heat exchanger

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Heat Exchanger

• The blood is cooled to lower body temperature
  during bypass
• Lowering of body temperature decreases O2
  consumption so in case there is an interruption
  in blood flow, there will be less chance of
  ischemia occurring during the interruption
• There is also a protective effect on the brain
  during the period of hypothermia

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Heat Exchanger

• Once the surgery is complete then the heat
  exchanger has a heating coil that is then used to
  warm the blood back to normal body temperature
• Because gas solubility decreases as blood temp
  rises, there is a filter built into the distal
  end of the heat exchanger to catch any bubbles
  that may form during rewarming

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Main Pump

• Modern CPB machines use either an electrically
  driven double-arm roller pump or a centrifugal
  pump
• The pump is used to propel blood through the CPB
  circuit
• Roller pumps produce flow by compressing
  large-bore tubing in the main pumping chamber as
  the head turns

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Main Pump

• The constant speed of the rollers pumps blood
  regardless of the resistance encountered and
  produces a continuous non-pulsatile flow
• Flow is directly proportional to the number of
  revolutions per minute
• There are usually battery backups in case of
  power failure and most roller pumps have a hand
  crank built in just in case of complete failure

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Main Pump

• Centrifugal pumps consist of a series of cones in
  a plastic housing
• As the cones spin, the centrifugal forces created
  propel the blood from the centrally located inlet
  to the periphery
• In contrast to roller pumps, these pumps are less
  traumatic to blood and blood elements

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Arterial Filter

• Particulate matter (thrombi, fat globules,
  calcium, tissue debris) enters the CPB circuit
  with alarming regularity
• A final in-line arterial filter is mandatory to
  prevent systemic embolism
• Once filtered, the propelled blood returns to the
  patient, usually via a cannula in the ascending
  aorta

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Accessory Pumps Devices

• Several accessory devices are usually
  incorporated into the CPB pump
• Cardiotomy Suction
• Left Ventricular Vent
• Cardioplegia Pump

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Cardiotomy Suction

• This suction aspirates blood from the surgical
  field during CPB and returns the blood back to
  the main reservoir
• It is at a lower suction pressure than that from
  the wall so it produces less trauma to the red
  cells and blood elements and they can safely be
  recirculated back into the pump and back into the
  patient

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Left Ventricular Vent

• With time, even after institution of total
  bypass, blood accumulates in the left ventricle
  as a result of residual pulmonary blood flow from
  bronchial arteries
• Distention of the left ventricle compromises
  myocardial preservation and requires
  decompression (venting)
• The blood aspirated by the vent pump normally
  passes through a filter and is returned to the
  venous reservoir

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Cardioplegia Pump

• Cardioplegia (a high concentrated K solution
  used to stop the heart from contracting) is most
  often administered via an accessory pump on the
  CPB machine
• This pump usually has its own heat exchanger
  associated with it
• This solution is the key factor that stops the
  heart for surgery to proceed

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• Systemic Hypothermia

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Hypothermia

• Intentional hypothermia is routinely used
  following initiation of CPB
• Core body temp. is usually reduced to 20-32
  degrees C
• Metabolic O2 demands are generally cut in half
  with each reduction of 10 degrees C in body temp

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Hypothermia

• Profound hypothermia to 15-18 degrees C allows
  total circulatory arrest for complex repairs of
  the aorta for up to 60 min.
• During that time, both the heart AND CPB pump are
  stopped
• Hypothermia is NOT w/o its problems however

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Hypothermia

• Profound hypothermia can be associated with
• Platelet dysfunction
• Reduced serum ionized Calcium
• Reversible coagulopathy
• Depression of myocardial contractility

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• Myocardial
• Preservation

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Myocardial Preservation

• Optimal surgical results depend on prevention of
  myocardial damage and maintenance of normal
  cellular integrity and function during CPB
• Nearly ALL patients sustain some myocardial
  damage during CPB
• Proper preservation techniques can keep this
  damage to a minimum

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Myocardial Preservation

• Inadequate myocardial preservation usually
  manifests at the end of CPB as a persistently LOW
  CO, EKG signs of ischemia, or cardiac arrhythmias
• Aortic cross-clamping during CPB completely cuts
  off coronary blood flow
• Although no studies have really been done to
  determine an optimal time for cross-clamping, it
  is believed that cross-clamp times GREATER than
  120 min. are generally considered as undesirable

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Myocardial Preservation

• The most widely used method or arresting the
  myocardium and decreasing O2 demand is through
  the use of a solution high in K called
  Cardioplegia
• Following initiation of CPB, induction of
  hypothermia and cross-clamping of the aorta, the
  coronary circulation is periodically perfused
  with cold cardioplegia

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Cardioplegia

• The resultant increase in extracellular K
• eventually leads to the INACTIVATION of the
  fast Na channels, basically paralyzing the
  myocardium
• Basically with the temperature reduced and the
  tissues paralyzed, the myocardial O2 demand is
  approx. 1/20th of its normal requirement and in
  this condition the tissue can survive with
  minimal O2 supplied to it

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Cardioplegia

• Although the exact composition varies from center
  to center, basically the composition of
  cardioplegia is the same approx. 10-40mEq/L of
  K
• Small amounts of calcium and magnesium are added
  to help maintain cellular integrity and sodium
  concentrations are usually kept less than normal
  serum Na (lt140 mEq/L)

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Cardioplegia

• Since the cardioplegia cannot reach areas of the
  heart that are distal to the coronary artery
  obstructions, many surgeons also administer
  cardioplegia retrograde through a coronary sinus
  catheter and back through the venous system
• Some studies have reported that the combination
  of antegrade and retrograde cardioplegia is FAR
  superior at protecting the myocardium as compared
  to only antegrade administration

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Cardioplegia

• Cardioplegia is usually administered every 20-30
  minutes while the patient is on CPB
• Excessive cardioplegia can result in an absence
  of electrical activity, AV conduction blockade,
  or a poorly contracting heart at the conclusion
  of CPB
• There is often a period of Wash Out needed
  after long cases at which time the heart is
  allowed to return beating while still on partial
  CPB to allow excess cardioplegia and cellular
  byproducts to become eliminated and allow the
  myocardium to contract fully and without any
  depression

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• Monitoring and
• IV Access

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Monitoring

• The following monitors are usually used during a
  CABG procedure
• EKG (at least a minimum of 2 leads, II and V5)
• O2 Sat
• BP Cuff
• Temp
• EtCO2
• A-line (for ABGs and continuous BP placed
  PREOP)
• SG Cath (w/ or w/o fiberoptics to calculate CO
  and to sample Mixed Venous blood or to get a
  continuous readout of MVO2 Sat)
• TEE
• BIS

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IV Access

• In the preop suite prior to induction, the nurses
  or MDs usually place AT LEAST an 18g, preferably
  a 16g, IV Cath
• Once the IV Cath is placed, premedication can be
  given and then the A-line is placed
• This is the minimum needed prior to induction
• In sicker patients, an Introducer and an SG cath
  need to be placed as well ALL prior to induction
  of anesthesia

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• Induction
• Maintenance

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Premedication

• The choice AND amount of premedication is
  dependant on the degree of myocardial disease
  that is present preop
• Patients with an EF lt40 should be given preop
  medications slowly and carefully since they are
  much more sensitive to the hypotensive effects of
  the meds

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Premedication

• The usual preop cocktail at Baptist PRIOR to
  A-line placement was
• Versed 2-6 mg as tolerated IV
• Fentanyl 1-2 cc as tolerated IV
• Robinul 0.2 IV
• O2 NC _at_ 3-5L/Min (ALL patients)

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Induction

• For ELECTIVE procedures, induction of GA should
  be done in a slow, smooth, controlled fashion,
  often referred to as a cardiac induction
• Many studies have been done that have shown no
  difference in long-term outcomes when different
  anesthetic techniques are compared

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Induction

• It should be emphasized that anesthetic dose
  requirements are extremely variable and generally
  are INVERSELY related to ventricular function
• Severely compromised patients should be given
  agents in small doses, slowly and in increments
• In those cases, Etomidate or Ketamine may be your
  drugs of choice since they are both associated
  with the least amount of myocardial depression

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Induction

• Several techniques are available for your use
• High Dose Opioid Anesthesia
• Total Intravenous Anesthesia (TIVA)
• Mixed Intravenous/Inhalation Anesthesia

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High Dose Narcotics

• High dose opioid techniques were developed to
  circumvent the myocardial depression seen with
  the older inhalational agents
• Dose ranges are as follows
• Fentanyl 50-100 mcg/kg
• Sufenta 15-25 mcg/kg

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High Dose Narcotics

• Drawbacks to this technique are
• PROLONGED postop respiratory depression (12-24
  hrs)
• Very high incidence of patient awareness
• Often fails to control the hypertensive response
  to stimulation in many patients with good LVF
• Rigidity during Intubation
• Postop Ileus

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TIVA

• TIVA techniques were developed for cost
  containment reasons since with these techniques,
  patients were extubated earlier, had shorter ICU
  stays, and had earlier hospital discharge
• This technique usually employs induction with a
  bolus of Propofol (0.5-1.5mg/kg depending on
  Vent. Function)
• This is usually followed by a Propofol infusion
  between 25-100mcg/kg/min depending on BP response
  to stimuli

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TIVA

• Usually, Remifentanil is added (1mcg/kg bolus)
  followed by an infusion of 0.25-1mcg/kg/min
• Since Remifentanil has such a short half life, it
  needs to be D/Ced at the end of the case and
  usually MS is given for postop pain control (5-10
  mg boluses titrated to BP and pulse)

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Mixed IV/Inhalation Anesthesia

• Renewed interest in volatile anesthetics came
  about following several studies that demonstrated
  a protective effect of volatile anesthetics on
  ischemic myocardium
• This is especially valuable since the newer
  volatile anesthetics have much less myocardial
  depression than the older agents have

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Mixed Anesthesia

• Induction is usually done with Propofol (0.5-1.5
  mg/kg) or Etomidate (0.1-0.3 mg/kg)
• Thiopental can also be used as an induction agent
  (1-2 mg/kg)
• Narcotics are given in smaller doses (Fentanyl
  1-2 mcg/kg Sufenta 0.25-0.5 mcg/kg)

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Mixed Anesthesia

• A volatile anesthetic (0.5-1.5 MAC) is also
  administered for maintenance of anesthesia and to
  blunt the sympathetic response to stimuli (Sevo
  or Iso)
• Some clinicians also administer a low-dose
  propofol infusion (25-50 mcg/kg/min) for
  maintenance as well
• Couple all of this with a shorter acting muscle
  relaxant (Zem or Nimbex) and you can usually wake
  up the patient and extubate them within 1-2 hours
  after surgery)

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Mixed Anesthesia

• OF NOTE N2O is usually avoided during Cardiac
  surgery that uses CPB to avoid enlarging any
  bubbles that may enter into the circulation
  during the procedure

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Other Techniques

• The combination of Ketamine (1-2 mg/kg for
  induction) with or w/o Versed (0.05-0.1mg/kg) for
  induction can also be used in patients with
  depressed ventricular function
• This is usually followed by LOW dose narcotics
  (Fentanyl 0.5-1 mcg/kg) and low dose volatile
  anesthetics (0.5 MAC) to provide amnesia during
  the procedure

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Other Techniques

• If needed, additional boluses of Ketamine (0.5-2
  mg/kg) may be given during the procedure as
  dictated by the BIS reading if the patient cannot
  tolerate the small doses of narcotics or the
  small doses of inhalational agents
• In patients with severely depressed ventricular
  function, Etomidate and O2 can be used as the
  sole anesthetic and additional boluses of
  Etomidate given also dictated by the BIS reading

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• Break
• Time!!!

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• Muscle
• Relaxants

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Muscle Relaxants

• Muscle relaxation is necessary for intubation, to
  facilitate sternal retraction and to prevent
  patient movement and shivering
• Unless airway difficulty is anticipated,
  intubation is usually done through the use of
  NON-depolarizing NMBs
• The choice of agent is solely based on the
  desired hemodynamic response

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Muscle Relaxants

• Ideally, the agent should be devoid of
  significant cardiovascular side effects
• Rocuronium and Vecuronium are MOST commonly used
• Pancuronium can be used in patients with
  depressed ventricular function
• Atricurium should be avoided due to possible
  hypotension from histamine release

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Muscle Relaxants

• SUX should be considered for endotracheal
  intubation if the potential for difficult airway
  exists or in full stomach inductions
• A nerve stimulator is mandatory to use along with
  ANY NMB especially if early extubation is being
  planned

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• Baptist
• Techniques

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Baptist Technique

• What my Induction technique was, is as follows
• Slowly in 2-3cc increments, I would give 10cc
  Fentanyl as tolerated
• That would be followed with 10-15cc of Propofol
  again as tolerated and by BIS readings
• Then Zemuron 50mg (or Vec 10cc)
• I would mask ventilate with 100 FiO2 until
  paralyzed and then Intubate

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Baptist Induction

• 5) Again, depending on the BIS reading, if it was
  still above 60 after the Fentanyl/Propofol combo,
  I would ventilate with 2-3 Sevoflurane, or
  0.5-1 Isoflurane until paralyzed and then
  intubate once my BIS reading was below 60
  (preferably 40-50)
• 6) Men would get an 8.0 ETT and women would get a
  7.5ETT since I would be anticipating postop
  ventilation for at least 2-3 hours

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Baptist Induction

• 7) At that point, I would set my Sevo on 2 or
  Iso on 1 and gown and glove up to insert my
  Introducer and SG cath
• 8) During the insertion, if hypotension would
  develop, I would instruct my assistant to turn
  down/or off the gas and give 5-10mg ephedrine or
  50-100mcg of Neo depending on the heart rate

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Baptist Maintenance

• 9) Once my SG was in place, depending on the BIS
  reading I would dial in volatile agents as needed
  to keep it 40-50
• 10) Right before STERNOTOMY I would give another
  5-10cc Fentanyl depending on the ventricular
  function
• 11) Right before going on bypass, I would give
  another 5-10cc Fentanyl and another FULL
  intubating dose of an NMB (usually Zem 50, or Vec
  10mg)

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Baptist Technique

• 12) Once it was confirmed that we were on FULL
  bypass, the vent would be turned off, Pop-off set
  to full open, and Reservoir bag removed and the
  system left open to air (I know it seems weird to
  TURN OF your vent but remember, oxygenation is
  NOW being done by the CPB Machine and the surgeon
  cant work with a pair of lungs expanding and
  contracting in his OR field)

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Baptist Technique

• 13) Also at that time, your Vaporizers need to be
  turned off completely as well
• 14) During bypass, I would be guided by my BIS
  monitor if it would start to creep up close to
  50-55, I would give another 5cc Fentanyl if it
  would stay stable at 30,40,50 I would do nothing
  but watch the surgery and anticipate coming off
  bypass

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Baptist Technique II

• For sicker patients or patients with poor
  ventricular function, I would approach the
  situation differently
• INDUCTION Induction was usually done with
  Etomidate (0.2-0.3mg/kg) followed by a muscle
  relaxant if that was tolerated well then
  Fentanyl 3-5cc was also given and another
  Fentanyl 3-5cc right before sternotomy OR
  Etomidate at half an induction dose bolus right
  before sternotomy

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Baptist Techniques II

• Regardless of sick or not, you always run 100
  FiO2 to maximize oxygenation to the myocardium
• In the sicker patients, your entire anesthetic
  can be Etomidate given in periodic boluses at the
  appropriate moments (Induction, Pre-sternotomy,
  coming off bypass, at end before transfer to ICU)

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• Pre-Bypass
• Period

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Pre-bypass Period

• Following induction and intubation, the
  anesthetic course is typically characterized by
  an initial period of minimal stimulation (prep
  and draping) that is frequently associated with
  periods of hypotension
• These periods of hypotension will be interspersed
  with periods of INTENSE stimulation (Skin
  incision, Sternotomy) that can induce
  hypertension and tachycardia

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Pre-bypass Period

• Your anesthetic agent(s) should be adjusted
  appropriately IN ANTICIPATION of these periods of
  stimulation
• Sternal retraction may be associated with periods
  of bradycardia that may need treatment with
  ephedrine or atropine
• Deeply anesthetized patients may have a gradual
  decrease in CO once the chest is opened due to
  decreased venous return since now the chest is
  open to normal atmospheric pressure and the
  negative intrathoracic pressure that draws blood
  into the chest is lost

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Pre-bypass Period

• Myocardial ischemia in the pre-bypass period is
  often but not always associated with tachycardia,
  hypertension, or hypotension
• Use of a balanced technique incorporating
  narcotics AND volatile agents can give you a
  better degree of control of hemodynamic
  parameters rather than using only one drug by
  itself

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Sternotomy

• A WORD ABOUT STERNOTOMY
• When it is time for sternotomy, the surgeon
  will give a command LUNGS DOWN If the lungs
  are inflated during sternotomy he can possible
  slice right through them
• IT IS NOT ENOUGH JUST TO TURN YOUR VENT OFF
  DISCONNECT THE INLET SIDE OF THE CIRCUIT (going
  TO the patient) and hold it while Sternotomy is
  made

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Sternotomy

• This serves TWO purposes
• Makes sure there is NO AIR going into the lungs
• You will REMEMBER that the breathing is off by
  having the circuit in YOUR HAND!!
• (A COMMON problem is forgetting to turn the vent
  back ON!! It really does happen, so work it into
  your routine that you always remember to turn the
  vent back on)

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Communication

• This is a good opportunity to bring up the
  subject of communication ALWAYS COMMUNICATE WITH
  THE SURGEON AND PUMP TECH
• It is a good habit to get into to REPEAT orders
  given to you by the surgeon
• An example is when he/she says Lungs Down, you
  acknowledge Lungs Down both as a confirmation
  that you heard and also as a signal that you have
  done what is asked of you

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Communication

• This is a good habit to have between you and all
  the major players in the room
• Especially coming off bypass when the surgeon
  gives you orders to start drips, etc. you always
  acknowledge NTG _at_ 5mcgms or Neo/Epi _at_ 10cc
• Then he knows its done and you have just double
  checked in your own head what was asked of you

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Sternotomy

• There are TWO ways to do a sternotomy
• A regular sternal saw on a Virgin chest
• A Recipricating saw on a Redo chest
• The regular saw looks like a Jig saw with a guard
  on the blade
• The recipricating saw has a round wheel that cuts
  from the top down with pressure

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Sternotomy

• The reason for the two saws is that with a REDO
  there may be structures that have healed and are
  stuck to the underside of the sternum and with
  a regular saw, you will cut right through these
  structures
• The REDO saw cuts from the TOP down and as soon
  as the bone is cut through, then the surgeon
  stops and moves down to the next spot

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Redo Sternotomy

• WITH A REDO CASE ALWAYS be ready for the shit to
  HIT THE FAN after sternotomy just in case
  anything vital is sawed through
• Have your fluids ready, your heparin ready for a
  STAT heparinization and be ready to go on CPB in
  a matter of minutes (even seconds if the surgeon
  is fast enough!!)

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• Anticoagulation

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Anticoagulation

• Anticoagulation must be established prior to CPB
  to prevent acute DIC and formation of clots in
  the CPB pump
• The adequacy of anticoagulation MUST be confirmed
  by a test called an ACT (Activated Clotting Test)
• An ACT longer than 400-500 sec. is considered
  SAFE at most centers

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Anticoagulation

• The Heparin dose that is usually given prior to
  measurement of an ACT is 300-400 U/kg
• The dose of heparin is usually given at the point
  in surgery where the Aortic Purse string sutures
  are being placed prior to cannulation
• Some surgeons prefer to administer the heparin
  themselves while others leave it up to Anesthesia
  or the Pump techs
• Usually the pump tech will determine the exact
  dose to be given and communicate it to you prior
  to administration

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Anticoagulation

• Commonly, doses of Heparin that will be given are
  between 28,000 U to 40,000 U
• For this purpose, Heparin comes in a special vial
  with a concentration of 10,000 U per 1cc instead
  of the normal 1,000 U /cc
• MAKE SURE YOU ARE USING THE CORRECT CONCENTRATION

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Anticoagulation

• If need be, in an emergency, a 3.5cc dose of
  10,000 U/cc Heparin is usually sufficient to get
  an ACT between 400-500 Sec. so remember 3.5cc in
  an emergency
• If the Heparin is administered by the
  anesthesiologist, it should normally be
  administered through a Central Line and the ACT
  should be measured between 3-5 min POST heparin
  dose being given

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Anticoagulation

• There are times that the surgeon will be waiting
  for the ACT prior to beginning his surgery so
  there may be times that you are pressured to
  HURRY the 3 min. needed post Heparin, BUT DONT
• Again if you go on bypass and the ACT was not in
  the correct range, you can easily KILL a patient
  and the blame will be placed on you so stand fast
  and stick to the protocol

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Anticoagulation

• Occasionally, resistance to Heparin is
  encountered in patients with Antithrombin III
  deficiency
• Patients with Antithrombin III deficiency will
  achieve normal anticoagulation after receiving 2
  U of FFP
• In some instances, it may take double the normal
  dose of heparin to achieve normal ACT response
  (400-500 Sec) in some of these patients

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Bleeding Prophylaxis

• Bleeding prophylaxis with ANTIFIBRINOLYTIC AGENTS
  may be initiated before or after anticoagulation
• APROTININ therapy should be considered in
  patients who
• Are undergoing a repeat operation
• In patients who refuse blood products (i.e.
  Jehovahs Witnesses)
• Who are at high risk for postop bleeding because
  of preop therapy with Plavix, Rheo pro, Ticlid,
  etc.

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Aprotinin

• Although the exact mechanism is not known,
  Aprotinin is an inhibitor of serine proteases
  that lead to platelet dysfunction
• Its most important action is to preserve platelet
  function (adhesiveness and aggregation)
• Aprotinin therapy is highly effective in reducing
  periop and postop blood loss and transfusion
  requirements (by 40-80)

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Aprotinin

• It also seems to blunt the intense inflammatory
  response to CPB
• SERIOUS ALLERGIC REACTIONS can occur in a small
  number of patients so a test dose of 1cc is
  usually given to ALL patients receiving Aprotinin
• The 1cc test dose is given and if there will be
  an allergic reaction it is going to occur within
  5 min. and manifest as drastic reductions in BP
• Some people have complete anaphylactic reactions
  that require Rx w/Epinephrine

98
Aprotinin

• Reactions are also more likely to occur upon
  repeat exposure
• Some surgeons reserve the use of Aprotinin for
  difficult cases involving the aorta and the
  replacement of part of the arch as in Aortic
  aneurysms or for repeat procedures
• Others use it routinely with ALL their cases as
  they believe that it significantly reduces the
  need for periop and postop transfusion
  requirements

99

• Cannulation

100
Cannulation

• Cannulation for CPB is a critical time
• AFTER heparinization, AORTIC cannulation is
  usually done first so that if any rapid fluid
  infusions need to be done to support the BP at
  this critical time, it can be done rapidly
• Next is Venous cannulation and either one or two
  venous cannulas will be placed

101
Cannulation

• If one cannula is used, it will be placed in the
  Right Atrium
• If two are used they will be placed in the vena
  cavae, one Superior, the other Inferior
• There can be quite a bit of blood loss associated
  with venous cannulation so that is another reason
  why the aortic is placed first, so any blood loss
  with venous cannulation can be rapidly
  compensated for through the aortic cannula

102
Cannulation

• Venous cannulation frequently precipitates
  atrial, or less common, ventricular arrhythmias
• PACs and transient bursts of SVTs are common
• In rarer cases, sustained Atrial tachycardia and
  A-fib can occur causing significant alteration in
  hemodynamics
• This is usually fixed by going on bypass and
  administering cardioplegia to quiet the heart and
  discontinue the problem arrhythmias

103

• Bypass
• Period

104
Bypass Period

• Once the cannulas are properly placed and
  secured, the ACT is acceptable and the pump tech
  is ready, CPB is initiated
• The venous clamp and aortic clamp are released
  from the pump lines and the heart gradually
  begins to empty
• Cardioplegia is administered to quiet the heart
  and cooling is begun

105
Bypass Period

• Once the pump tech lets you know that you are on
  FULL bypass, you can shut down the ventilator,
  open the system to room air and NOW begin your
  preparation for coming OFF bypass
• You will need to organize your emergency drugs
  (Neo, Ephedrine, Epi) and you will also need to
  organize your DRIPS to be used if needed

106
Bypass Period

• Standard Drips usually include
• NTG and/or Nipride drips
• Neosynephrine drip
• Epinephrine drip
• A Combo Neo/Epi drip if used instead of single
  drips
• Levophed drip if used
• Lidocaine drip if used

107
Bypass Period

• ALL of these drips should be run through a
  MANIFOLD with a carrier solution and hooked up to
  a PA cath port (either distal or Infusion port)
• You should also ready some muscle relaxant, some
  Fentanyl, possibly some Versed
• We had a rule that when we were coming off pump
  we would give Versed 4-8 mg regardless of the BIS
  reading to prevent recall (a surgeon created rule
  that no amount of logic could change!!!)

108
Bypass Period

• Anesthesia during the bypass period will be
  guided by your BIS monitor
• Hypothermia (lt34 degrees C) itself is usually
  enough anesthesia to suffice but if your BIS
  starts to creep up, you have a multitude of
  choices to use
• Fentanyl, Etomidate, Propofol, Ketamine, Versed
  are ALL valid choices to use to treat an elevated
  BIS during bypass

109
Control of Blood Pressure

• During bypass there may be periods when your BIS
  reading is acceptable but the BP rises. There
  are several options available to you
• Give more anesthetic regardless of the BIS level
• Start a NTG drip or give the Pump Tech some NTG
  in a syringe and they will gradually titrate it
  to a lower BP
• The Pump Tech can start giving their Inhalational
  agent via their machine along with the oxygen
  being bubbled through the bloodgas interface

110
Rewarming

• Once the surgical procedure is about ¾ finished,
  the surgeon will give the command to REWARM
• The blood will be warmed in the pump to approx.
  39 degrees C and circulated throughout the body
  while you watch your temp monitors closely
• THIS IS THE TIME OF MAXIMUM RECALL

111
Rewarming

• Over 80 of patient recall postop can be traced
  back to the REWARMING period
• Most of this data was collected prior to
  institution of the use of the BIS monitor
• Now, with the BIS monitor, recall incidents have
  decreased by over 75
• Just watch your BIS and if it climbs as the
  patient rewarms, administer a bolus of any of the
  drugs that we have just previously mentioned

112
Rewarming

• If you have started with a drug then usually
  stick to that drug, or mix and match
• Many clinicians (pre-BIS) would routinely
  administer Versed 5-10mg IV or Scopolamine
  0.2-0.4mg when rewarming is initiated
• Sweating during rewarming is NOT an indication of
  light anesthesia rather it is a hypothalamic
  reflex to perfusion with blood at 39 degrees C
• It occurs very commonly during rewarming

113

• Termination
• Of
• CPB

114
Termination of CPB

• Discontinuation of bypass is accomplished by a
  series of necessary procedures and conditions
• Rewarming must be completed
• Air must be evacuated from the heart and any
  bypass grafts
• The Aortic cross-clamp must be removed
• Lung ventilation must be resumed

115
Termination of CPB

• The surgeons decision about when to rewarm is
  critical
• Adequate rewarming requires time, BUT rewarming
  too soon removes the protective effects of
  hypothermia
• Rapid rewarming often results in large
  temperature gradients between well-perfused
  organs and peripheral vasoconstricted tissues

116
Termination of CPB

• It is a common occurrence that soon after
  discontinuation of CPB, there is a significant
  drop in temperature as the peripheral locations
  equilibrate with the more perfused organs to
  cause a lower overall body temperature
• Excessively rapid rewarming can result in the
  formation of gas bubbles in the blood stream as
  the solubility of gases rapidly decreases with
  increased temp

117
Termination of CPB

• It is not uncommon that the heart develops
  arrhythmias during rewarming
• It can even go into V-fib which requires
  immediate defibrillation by internal paddles at
  5-10 J
• You can assist in this process by administering
  Lidocaine 100-200mg and Magnesium 1-2gms prior to
  the removal of the aortic cross-clamp

118
Termination of CPB

• Many clinicians advocate a head-down position
  while intracardiac air is being evacuated to
  decrease the likelihood of cerebral emboli
• TEE can be used to assess when the intracardiac
  air is completely evacuated (you can see the tiny
  bubbles bouncing around and can watch them
  gradually dissipate until they are gone)

119
Termination of CPB

• During this period you will be asked to reinflate
  the lungs
• Initial inflation may require higher than normal
  insp. pressures (40-50mm H2O)
• You should do this while using direct vision so
  you can see how the lungs inflate and DO NOT
  over-inflate them or you can interfere with the
  surgical procedure or grafts that have been placed

120
Termination of CPB

• General guidelines for separation from CPB
  include the following
• The core body temperature should be at least 37
  degrees C
• A stable rhythm (preferably sinus) must be
  present
• The Heart rate must be adequate (generally 80-100
  beats/min)

121
Termination of CPB

• 4) Lab values must be within acceptable limits.
  Significant acidosis (pHlt7.20), hypocalcemia, and
  hyperkalemia (gt5.5mEq/L) should be treated
  hematocrit must be at least 22-25
• 5) Adequate ventilation with 100 O2 must have
  been resumed
• 6) ALL monitors should be rechecked for proper
  function and recalibrated if necessary

122
Weaning from CPB

• Discontinuation of CPB should be gradual as
  systemic arterial pressure, ventricular volumes
  and filling pressures, and CO are assessed
• Central aortic pressure can be estimated by
  palpation by the surgeon
• Vent. Volume and contractility can be estimated
  VISUALLY whereas filling pressures are measured
  using the wedge pressures
• CO can be measured by thermodilution
• TEE also provides all of this same information by
  direct visualization in real-time

123
Weaning from CPB

• Weaning is accomplished by progressively clamping
  the venous return line to the CPB machine and
  allowing the heart to gradually fill and eject
• Pump flow is gradually decreased as systemic
  arterial pressure rises
• Once the venous line is completely occluded and
  the systolic arterial pressure is gt80-90mm Hg,
  pump flow is stopped and the patient is evaluated

124
Weaning from CPB

• Most patients fall into one of the following four
  groups when coming off bypass (see next slide)
• Patients with good ventricular function are
  usually quick to develop good blood pressure and
  cardiac output and can be separated from CPB
  immediately

125
(No Transcript)
126
Weaning from CPB

• Hypovolemic patients are a mixed group that
  includes both patients with nl VF and those with
  varying degrees of impairment
• Patients with pump failure emerge from CPB with a
  sluggish, poorly contracting heart that
  progressively distends
• In these cases, CPB is restarted until adequate
  inotropic therapy can be used to augment function
  and support the heart as it comes off of CPB

127
Weaning from CPB

• In patients who have trouble coming off of CPB,
  other causes need to be investigated and
  eliminated
• The patient should be evaluated for unrecognized
  ischemia (kinked graft, coronary vasospasm),
  valvular dysfunction, shunting, or right
  ventricular failure (distention primarily in the
  right ventricle)

128
Weaning from CPB

• TEE may be used to diagnose many of the reasons
  why the patient may not be able to come of CPB
  smoothly and easily
• If inotropes and afterload reduction fail to
  remedy the situation, an Intraaortic balloon pump
  can be inserted
• An IABP helps rest the heart and can reduce O2
  demand by approx. 50

129

• Post-bypass
• Period

130
Post-bypass Period

• During the post-bypass period, bleeding is
  controlled, bypass cannulas are removed,
  anticoagulation is reversed and the chest is
  closed
• Systolic pressure is usually maintained at 90-100
  mm Hg to minimize bleeding
• Venous cannulas are removed first before the
  aortic cannula in case the aortic cannula is
  needed for rapid infusion of volume or blood

131
Post-bypass Period

• Most patients need additional blood volume
  subsequent to termination of CPB
• Administration of blood, colloids, and
  crystalloid fluid is guided by filling pressures
  and post bypass hematocrit
• A final hematocrit of 25-30 is generally
  desirable

132
Reversal of Anticoagulation

• Once hemostasis is judged acceptable and the
  patient continues to remain stable, heparin
  activity is reversed with PROTAMINE
• PROTAMINE is a protein that binds to and
  effectively inactivates heparin
• There are several techniques for administration
  of Protamine, but regardless of which technique
  is used, an ACT is done 3-5 min. after reversal
  is given

133
Reversal of Anticoagulation

• The simplest technique to calculate the dose of
  Protamine is to base the dose of Protamine on the
  dose of heparin given total
• The Protamine is given in a ratio of 1-1.3mg of
  Protamine for every 100 U of Heparin given
• The dose is usually calculated by the pump tech
  and is reported to you for administration
• It is usually on a CC per CC basis with the
  Heparin (30cc of Hep given 30cc of Protamine
  given)
• The concentration of Protamine is 10mg/cc
• After administration of Protamine the ACT should
  return to baseline

134
Reversal of Anticoagulation

• IMPORTANT SAFETY POINT DO NOT draw up your
  Protamine until it is time to give it EVEN if it
  is labeled and set aside
• If Protamine is inadvertently given prior to its
  need, it will cause massive coagulation within
  the CPB pump and tubing and lead to patient DEATH
  very quickly!!!
• GIVE YOUR PROTAMINE THROUGH A PERIPHERAL SITE TO
  AID IN DILUTION

135
Protamine

• Protamine administration can result in a number
  of adverse hemodynamic effects
• To lessen these effects, PROTAMINE SHOULD ALWAYS
  BE GIVEN SLOWLY (over 5-10 min)
• This will help to minimize the hypotension that
  can sometimes be seen with Protamine
  administration

136
Protamine

• Rapid administration of Protamine can cause
• HYPOTENSION (sometimes extreme) from acute
  systemic vasodilation
• Myocardial depression
• Marked pulmonary hypertension
• Diabetics on Insulin are at a particularly high
  risk for adverse reactions to Protamine so be
  extra careful with any patient on Insulin for
  their DM and go extra slow with your
  administration

137
Protamine

• The trick I used was as follows
• If my protamine dose was 30cc, I would give 5cc
  and then draw back 5cc of Crystalloid, wait 30
  sec. and give another 5cc, draw back another 5cc
  of crystalloid, give another 5cc and continue the
  above until about 5-7 minutes had passed and then
  I would give the entire 30cc slowly over a minute
  or so since by then all I had left was primarily
  crystalloid in the syringe

138
Persistent Bleeding

• Persistent bleeding following bypass often
  follows long bypass periods (gt2 hrs)
• There can be several different causes for postop
  bleeding
• Inadequate surgical control
• Inadequate reversal of Heparin
• Reheparinization from administration of Heparin
  containing cell saver blood
• Thrombocytopenia from pump destruction of
  platelets
• Platelet dysfunction
• Hypothermia

139
Persistent Bleeding

• Careful observation of the surgical field
  following Protamine administration will reveal if
  clot formation is present or not
• The absence of clot formation should be
  identified and causes should be looked for
• Full clotting studies should be sent and
  appropriate action taken on the results
• It is not uncommon that after long pump runs, (gt2
  hr) FFP and Platelets are needed to correct
  clotting abnormalities

140

• Anesthesia
• Following
• CPB

141
Anesthesia post CPB

• Additional anesthetic agents are usually needed
  following termination of CPB
• These can be
• Low dose Inhalation agents
• Periodic boluses of Propofol/Etomidate
• Periodic boluses of narcotics
• Re-dosing of NMBs to prevent patient movement

142
Anesthesia Post-bypass

• Since you will NOT be extubating your patient, do
  not worry about re-dosing with NMBs
• It is better to have a patient who is not moving
  than to have a patient suddenly start to move at
  the end of a case
• Especially before transfer, make sure that your
  patient is dosed with NMBs and some Narcotics
  for sedation

143
Transportation

• Transporting patients from the OR to the ICU is a
  hazardous process
• There are many areas for potential failure and
  disaster
• Monitor black out, overdosing of meds,
  interruption of drips and hemodynamic instability
  en route are just a few of the possible
  complications that can occur

144
Transportation

• One of the most common errors is that drips, once
  removed from pumps, are either left to drip wide
  open or are hooked up again either improperly or
  at improper flow rates due to time constraints
  and difficult position to be able to see the pump
  displays properly
• BE CAREFUL WITH YOUR DRIPS AND DOUBLE CHECK THEM
  AFTER TRANSFER

145
Transportation

• Prior to transfer from the OR table to the bed,
  several things need to be made ready
• O2 source with Ambu and FULL tank
• Monitor for EKG, O2 Sat, A-line readings
• Infusion pumps (the correct number)
• Emergency drugs (Neosynephrine, Ephedrine,
  Fentanyl some even carry 1-2cc of NTG in case
  the BP spikes in transit)

146
Transportation

• Once the patient is moved to the ICU bed and you
  assume control of their ventilations, go as
  quickly (BUT NOT recklessly) to the ICU and watch
  ALL your tubings while in transit
• Once in the ICU go slowly into the room so
  nothing hangs up on monitors, vent arms, etc.

147
ICU

• Your care of the patient continues even in the
  ICU until you have given report AND the ICU nurse
  feels comfortable with the patient
• DO NOT leave your emergency drugs behind for the
  nurse to use if needed
• Let them use their own meds!!!!
• Especially remember to bring back your FENTANYL
  dont leave that behind

148
ICU

• You are responsible to give an accurate report to
  the ICU RN. It should include
• Patient name
• Allergies
• PM History
• Procedure
• Any eventful activities that went on
• Bypass time and how easy they came off
• Is heparin reversed?
• Fluids in/Blood loss out
• Any drips they are on and what doses/rates
• Labs incl. K, ABG readings and coags if bleeding
  was a problem

149
ICU

• Here is an example
• This is Mr. Homer Simpson, allergic to PCN has
  a history of 3 vessel disease with good LVF, DM,
  Smoking, and elev. Cholesterol just had a 4
  vessel bypass, pump run was 38 min., came off
  pump easily Heparin reversed on Neo/Epi at 15cc
  and NTG at 5cc last Fentanyl dose was 5cc about
  10 min. ago and is currently in stable condition
  Fluids given were Crystalloid 3500cc, 2U PRBCs,
  Urine output 1200, Blood loss 3500cc labs were
  good w/ an ACT of 135, K at 4.4 and glucose at
  215 (ABG can be given as well)

150
ICU

• While you are giving report, the nurse and
  assistants will be hooking up the patient
• DONT LEAVE A MASS OF TANGLED TUBING TO BE SORTED
  THROUGH
• Try to be neat and organized and they will love
  you for it (NOW you will see what it is like on
  the OTHER side!!! NOT SO EASY IS IT!!!)

151
ICU

• Your stay in the ICU should last between 10-15
  minutes until you get a set of vitals from the
  ICU nurse and are sure that your patient is
  stable and the nurse is comfortable
• I would ALWAYS ask if it was OK for me to leave
  prior to departure
• Also, make sure your SG cath is wedging before
  you leave the caths have a tendency to advance
  during surgery and you end up with an OVER wedged
  reading check and adjust before you take off

152
NG Tubes

• I left out the NG tube!!!!
• It doesnt pay to put it in on induction because
  it will be coming out when the TEE goes in
• Put it in AFTER heparin is reversed and ACT is
  back to baseline
• Grease it up real good since you may be dealing
  with faulty platelets and you dont want a nasal
  hemorrhage on your hands

153
Conclusion

• Doing Hearts is like Peds you LOVE it or you
  HATE it
• Unfortunately the Heart surgeons tend to be a
  bunch of assholes in general so that does not add
  to the pleasure
• Get used to being yelled at and blamed for
  everything even if they did it themselves
• If you develop a tough skin, you can really enjoy
  doing the hearts and have a very satisfying
  experience