What physiologic change would you see with cross clamping?
↑ Arterial blood pressure above the clamp
↓ Arterial blood pressure below the clamp
↑ Segmental wall motion abnormalities
↑ Left Ventricular wall tension
↓ Ejection Fraction
↓ Cardiac Output
↓ Renal Blood Flow
↑ Pulmonary Occlusive Pressure
↑ CVP ↑ Coronary Blood Flow
What metabolic changes would you see with cross clamping?
↓ Total body Oxygen Consumption
↓Total Body Carbon dioxide production
↑Mixed Venous Oxygen Saturation
↓ Total body Oxygen extraction
↑ Epinephrine and Norepinephrine
What can we do for afterload reduction during cross clamping?
Shunts and Aorto to femoral Bypass.
What can we do for preload reduction during cross clamping?
Atrial to femoral bypass
What can we do for renal protection during cross clamping?
Distal aortic perfusion techniques
Drugs to Augment renal perfusion.
What other things can we during cross clamping (think metabolic and acid/base)
↓ Minute Ventilation
When the aortic clamp is released, what cerebrovascular and metabolic changes do you see?
Reactive Hyperemia and Central Hypovolemia
CO and Cardiac contractility decreases (because of humoral factors)
pH decreases, lactate increases
What therapeutic interventions can you do during the release of the aortic clamp?
Calcium, ephedrine, epinephrine
In aortic cross clamping, blood is redistributed away from hypoxia prone renal medulla, with a cross clamp an increase in renal vascular resistance may persist for ______________ after clamp is released.
How are the renal HD affected by the aortic cross clamp?
ARF approaches 5% with infrarenal clamping; 13% with suprarenal clamp
Mortality is 5 times higher with postop dialysis
RBP ↓ 80% with suprarenal clamp
Renal vascular resistance Increases 70%.
What are Barash goals of treatment for cross-clamping?
Wedge at 5-15mmHg, keep HR less than 80.
Use narcotics prior to cross clamping.
Keep patient somewhat hypovolemic or increase volatile. (just keep euvolemic).
Try to avoid neosynephrine, Neo has been associated with wall motion abnormalities.
Keep Hct 30% during clamp time.
Let BP increase gradually and let the clamp up slowly.
What can we do for renal protection during cross clamping??
Mannitol– 12.5 to 25 mg/70 kg
Lasix-- .5 to 1 mg/kg
Dopamine– 1 to 3 µg/kg/min
Fenoldopam--.05 to 0.1µg/kg/min
Mucomyst-600 mg PO bid
What two things are the best predictors of post-op renal function??
Pre-op renal function and volume status
Describe humoral and coagulation changes with aortic cross clamping.
Humoral mediators released from underperfused areas
May result in pulmonary hypertension and pulmonary edema
Increased clotting factor consumption after clamping
Increased clotting activity with clamping
May require cryoprecipitate, 1:1 PRBC with FFP, Amicar, desmopresin, ↑ room temperature
Describe the visceral and mesenteric ischemia that happens with cross clamping
Gut permeability and bacterial translocation
Inflammatory mediators from gut ischemia may be factors in renal failure and respiratory failure
What happens to the cerebral vasculature during unclamping?
Cerebral vasoconstriction caused from chemical mediators
Cerebral vasodilation after unclamping followed by profound vasoconstriction
Spinal cord ischemia is more likely to occur the more proximal the repair is. Which artery is very important in perfusing the spinal cord and where does it enter ?
Artery of Adamkiewicz – 75% joins anterior spinal artery between T8 and T12; 10% L1 to L2
Name the 8 methods of CNS protection during AAA surgery
Fast surgery/clamp time less than 30 minutes
Intraoperative regulation of hemodynamics (normohemodynamics)
Maintain or increase perfusion pressure
May need bypass if longer clamp times
Hypothermia 30 to 32 degrees Celsius
Calcium channel blockers
What is the single best anesthetic technique for AAA? (regional vs general)
Trick question, there isn't a single best! Balanced approach is probably best!