Medical Pharmacology Chapter 42:  Evaluation, Risk Assessment and  Anesthesia for Cardiovascular Procedures

 

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  •   Rationale for Concern:

    •  Vascular surgery is unique since vital organs may be completely deprived of their blood supply during surgery

    •  Highest  surgical mortality/morbidity is associated with vascular procedures

  •  Basis for morbidity/mortality associated with vascular surgery:

    1. Myocardial failure

    2. Myocardial ischemia

    3. Myocardial infarction

Surgical Procedures of Special Concern

Coronary bypass surgery

Carotid vessel surgery

Aorta surgery

Major vascular surgery (supplying viscera/limbs)

  •  Pathophysiology: Coronary Artery Disease (CAD): The major cause of death in the United States

    •  Major risk factors in development and progression of atherosclerosis

      • Obesity

      • Oobacco use

      • Inactivity

    • Atherosclerotic lesions:

      • Fatty streaks

      • Atheromatous plaques

  • "Aorta of a young man. 

  • It shows fatty streaks (elongated, flat, yellow lesions) and early fibrotic plaques, (broader and slightly elevated lesion)"

  • Courtesy of Jim Fishback, M.D., Department of Pathology, University of Kansas Medical Center

  • Fatty streak of the aorta, histology Lipid containing cells (probably macrophages) are present in the intima of the aorta"

  •  courtesy of Jim Fishback, M.D., Department of Pathology, University of Kansas Medical Center

 

  •  Atheromatous plaques 

    • Reduces vessel diameter (luminal diameter)

    • Location of thrombosis, vessel wall calcification, vessel wall weakening 

    •  Clinical Consequences:

      • Occlusion

      • Vessel rupture

      • Aneurysmal dissection

    •   Distribution of atheromatous plaques: Factors--

      • Regions of disturbed blood flow; shear stresses

        • Lower descending aorta {ostia of the major branches}

        • First  3 inches of coronary arteries

        • Descending aorta

        • Internal carotids

        • Circle of Willis

        • Leg arteries

    •  Atherogenesis: multistep process probably involving: (a)  Dysfunctional endothelial cells, (b) induction of growth and coagulation factors, (c) macrophage and monocyte involvement in injury response)

      •  Risk factors (hypolipidemia, smoking, hypertension) affect multiple steps

      •  Hypertension promotes endothelial damage

      •  Abnormal flow/perfusion characteristics increase atherosclerosis development

      •  Hyperlipidemia promotes atherosclerosis

;

  • "Severe atherosclerosis of the aorta. 

  • The intima of the aorta is eroded and ulcerated, appears rough, and is totally covered with clotted blood."

  • Courtesy of Jim Fishback, M.D., Department of Pathology, University of Kansas Medical Center

  • "Aneurysm of the aorta with a thrombus.  On opening of the aneurysm at autopsy, a mural thrombus was found partially occluding the lumen of the blood vessel."

 

  • "Atherosclerosis of the order with narrowing and thrombosis. 

  • Narrowing of the aorta is one of the common complications of atherosclerosis. 

  • Thrombi overlying the ulcerated endothelium contributes to the narrowing of the lumen and may completely block the blood flow through the narrow part of the blood vessel."

  • Courtesy of Jim Fishback, M.D., Department of Pathology, University of Kansas Medical Center

  • Prominent risk factors for atherosclerosis: hypercholesterolemia, tobacco smoking, hypertension

    •  Hypercholesterolemia:  reduction in cholesterol concentration may slow/reverse atherosclerosis

      •  Individuals with lower cholesterol exhibited reduction in all-cause mortality {30-year Framingham subject follow-up}

      •  Significant lowering of total cholesterol and low-density lipoproteins (LDL) cholesterol associated with:

        • Reduced total mortality (33%)

        • Reduced coronary  mortality (42%)

        • Reduced non-fatal coronary infarctions (33%) reduced requirement for coronary revascularization (30%)

    •  Hypertriglyceridemia:

      •   Possible independent risk fact for coronary disease

        • Hypertriglyceridemia--independent risk factor in women {Framingham study}

      •   Hypertriglyceridemia associated with reduced high-density lipoproteins levels (HDL levels)

    •  Tobacco Smoking: Cardiovascular systemic effects

      • Increased sympathetic tone secondary to nicotine absorption

      • Increased platelet adhesiveness

      • Displacement of O2 by CO

      • Possible immunological reaction in vessel wall

      • Most preventable risk factor for cardiovascular disease

    •  Hypertension --major risk factor independent of gender, age groups, race

      • Frequency: 10%-20% (USA): elevated blood pressure

      • Hypertension has additive effects with respect to other risk factors.

  • Primary Reference: Katz, J.,  Evaluation Risk Assessment of Patients with Vascular Disease in Principles and Practice of Anesthesiology (Longnecker, D.E., Tinker, J.H. Morgan, Jr., G. E., eds)  Mosby, St. Louis, Mo., pp. 201-218, 1998.

 
 
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