test 6 circ arrest and cerebral perfusion

Question 1

CPB W/O CIRC ARREST

Answer 1

 Very proximal aneurysms limited to the Aortic Root or Ascending Aorta.
 Cannulate in the ascending aorta or transverse aorta, and Dual stage in RA or Bicaval
 Cross clamp proximal to the Innominate Artery
 If patient is unstable prior to sternotomy – cannulate femoral to go on CPB prior to sternotomy
 Normal LV/PA Vent
 Normal CPG

Question 2

Deep Hypothermic Circulatory Arrest (DHCA) provides

Answer 2

 Bloodless field
 Uncluttered by clamps and cannulas
 Studies have shown it doesn’t necessarily abate cerebral metabolic demands
 Significant cerebral metabolic activity occurs at temperatures at which DHCA is initiated.
 Promotes brain ischemia
 Accumulation of metabolic wastes

Question 3

THINGS NEEDED FOR A CIRC ARREST CASE

Answer 3

 Need to monitor temperatures (naso/bladder)
 Need to monitor the brain (EEG)
 Mannitol (25g) and Steroids for cerebral protection
 Cannulation
 Axillary Cannulation is preferred
 In an emergency – femoral artery is used
 Venous cannula – RA, Bicaval, Femoral

Question 4

HOW TO DO A CIRC ARREST CASE

Answer 4

 CPB is initiated (Assess adequacy of perfusion)
 Cooling (Pump flows can be reduced to a CI of 1.6-1.8 L/min/m2)
 A 10°C decrease in temperature causes a 20-25% increase in blood viscosity
 Hct kept low until rewarm
 Give CPG via retrograde cannula because aneurysm/dissection is probably in the ascending aorta or arch
 Arrest is maintained with deep hypothermia
 Keep cooling until EEG shows no cerebral electrical activity (usually takes 20-25 mins or just 25 mins with no EEG with brain temp 18-20 degrees C and no lower than 15 degrees C)
 Head is packed in ice to facilitate surface cooling
 Put patient in Trendelenburg position

Question 5

After head is packed in ice and patient in trendelenburg position

Answer 5

 Flow is turned off
 Patient is drained
 Innominate artery is snared
 Initiate ACP - 10 mL/kg/min
 Right axillary – innominate artery – snare diverts blood antegrade through right common carotid – brain.
 Pressure no more than 90mmHg
 Aorta is opened
 Bleed back from the L. Common Carotid and L. Subclavian obscure field view
 Cardiotomy suction in distal arch
 Possible use of balloon occluder in both vessels.

Question 6

DHCA AND BRAIN ISCHEMIA

Answer 6

 Higher neurologic complications when DHCA was greater than 40 minutes
 Mortality
 Increased dramatically when DHCA was greater than 65 minutes.

Question 7

RETROGRADE CEREBRAL PERFUSION

Answer 7

 Gained popularity in the ‘90s.
 1st done in 1980 by Milles and Ochsner
 Used as neuroprotection in 1990.
- pressure no higher than 20-25 mmHg

Question 8

RETROGRADE CEREBRAL PERFUSION Benefits

Answer 8

• USED FOR MASSIVE AIR EMBOLISM
   Homogeneous cerebral cooling
   Air bubble wash out
   Wash out of embolic debris
   Wash out of metabolic wastes
   Prevent cerebral blood cell micro aggregation
   Delivery of oxygen and nutrients to brain.

Question 9

ANTEGRADE CEREBRAL PERFUSION

Answer 9

 Most popular right now
 Maintained pre-DHCA jugular venous sats and cerebral oxygen extraction
 Unilateral ACP associated with higher risk of perioperative stroke than bilateral ACP
 Unilateral and bilateral ACP under DHCA provided uniform cerebral perfusion to both hemispheres

Question 10

While delivering cerebral perfusion, what will be going on in the surgery

Answer 10

 End of graft is sewn to proximal descending thoracic aorta, transverse arch or distal ascending aorta
 Attach head vessels
 Island
 Branched graft
 Put patient in steep Trendelenburg
 Cardiotomy suction placed in unattached graft
 Release tourniquet on innominate
 Slowly increase flow to full flow (50mL/kg/min) as the aorta and graft are deaired
 If cannulated femorally, move the cannula to the arch
 Systemic circulation re-established.
 Proximal graft attached
 Slowly rewarm to 36.5°C
 Proximal complete
 Deair with venting needle through graft
 AoXC removed
 TEE is utilized to make sure there is no air present
 CPB is terminated

Question 11

OFF PUMP circ arrest

Answer 11

 Want systolic BP appx 100-120mmHg (do not overfill)
 Mean 70-90mmHg
 HR 60-80 BPM
 CI 2.0-2.5 L/min/m2
 Will see a coagulopathy after bypass, especially with DHCA
 Platelet dysfunction secondary to extreme hypothermia
 Usually requires FFP/ Platelets/ Cryo?
 Often resort to Factor VII and IX
 Usually use an antifibrinolytic to help with bleeding.

Question 12

COMPLICATIONS OF AORTIC SURGERY AND DHCA

Answer 12

 Air Emboli
 Clots
 LV Dysfunction
 MI (Reimplanting coronaries)
 Renal Failure
 Respiratory failure
 Coagulopathy
 Hemorrhage