Medical Pharmacology Chapter 43:  Adult Cardiac Procedures

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Cardiovascular Anesthesia: Choice of Agents and Related Issues

Fast Track Recovery

Opioids

 

Intravenous (IV) Sedative-Hypnotics

Nitrous Oxide (NO)

 

Inhalational Agents

Hypertrophic Cardiomyopathy*

  • "In this case the muscle thickening use of equal severity throughout the whole left ventricle"

  •  "In some cases of asymmetric septal hypertrophy obstruction to the outflow blood from the heart may occur as shown here.  Note that the mitral valve now touches the septum, blocking the outflow tract (Systolic Anterior Motion of the Mitral Valve or SAM). Some blood is leaking back through the mitral valve (Mitral Regurgitation)."

  • "In this form of hypertrophic cardiomyopathy the muscle thickening occurs predominately at the tip (apex of the left ventricle).  Only a small slit-like cavity remains"

* Drawings courtesy of The Cardiomyopathy Association

Myocardial Performance

Cardiac Drugs

 

Premedication for Cardiovascular Surgery

 

Other medications

 

Management of Intraoperative ischemia

  • Heparin Review

    • Composition:

      • Sulfated mucopolysaccharides (heterogenous)

    • Mechanism of Action:

      1. Binds to endothelial cell surface membrane.

      2. Heparin activity dependent on: plasma protease inhibitor antithrombin III

        • Antithrombin III -- inhibitor of clotting factors proteases (forming 1:1 stable complexes)

        • Complex forming reactions normally slow -- accelerated by three orders of magnitude (1000 times) by heparin

        • Following antithrombin-protease complex formation, heparin is released; available for binding to other antithrombin molecules

          •  A heparin high-molecular-weight (HMW) fraction has higher affinity for antithrombin compared to other fractions

          •  A heparin low-molecular-weight (LMW) fraction has a lower affinity for antithrombin but inhibits factor Xa (activated)

    • Toxicity:heparin

      • Major adverse/toxic effect: bleeding

        • Risk managed by attention to:

          1. Patient selection

          2. Dosage control

          3. Monitoring of partial thromboplastin time (PTT)

        •  Factors predisposing to hemorrhage:

          • Elderly

          • Renal failure patients

      •  Long-term heparin use-- increased incidence of:

        • Osteoporosis

        • Spontaneous fractures

      •  Transient thrombocytopenia: frequency = 25%

      •  Severe thrombocytopenia: frequency = 5%

      •  Paradoxical thromboembolism heparin-induced platelet aggregation

      •  Patients on heparin:

        • Thrombocytopenia that causes bleeding: probably due to heparin

        • New thrombus: may be due to heparin

        • If thromboembolic disease may be heparin-induced: discontinue heparin

    • Contraindications:heparin

      •  Heparin hypersensitivity

      •  Hematologic disease:

        • Hemophilia, thrombocytopenia, purpura,

      •  Cardiovascular:

        • Severe hypertension, intracranial hemorrhage, infective endocarditis

      •  Active tuberculosis

      •  Gastrointestinal tract

        • Ulcerative lesions

        • Visceral carcinoma

      •  Advanced hepatic/renal dysfunction

      •  Threatened abortion

      •  Related to medical procedures:

        • After brain, spinal cord or eye surgery

        • Lumbar puncture/regional anesthesia blocks

    •  Reversal of Heparin Effects:

      1. Drug discontinuation

      2. Use specific antagonist, e.g. protamine sulfate (note!- excess protamine also has an anticoagulant effect)

 

 

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