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INHALATIONAL ANESTHETICS PHYSIOLOGICAL EFFECTS AND CLINICAL COMPARISONS. DENNIS STEVENS MSN, CRNA, ARNP SEPTEMBER 2006 FLORIDA INTERNATIONAL UNIVERSITY PHARMACOLOGY OF ANESTHESIOLOGY NURSING NGR 6173. OBJECTIVES. Discuss the discovery and early development of inhalational anesthetics.
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INHALATIONAL ANESTHETICSPHYSIOLOGICAL EFFECTSAND CLINICAL COMPARISONS DENNIS STEVENS MSN, CRNA, ARNP SEPTEMBER 2006 FLORIDA INTERNATIONAL UNIVERSITY PHARMACOLOGY OF ANESTHESIOLOGY NURSING NGR 6173
OBJECTIVES • Discuss the discovery and early development of inhalational anesthetics. • Explain theories of anesthetic action related to inhalational anesthetics. • Define MAC and respective percentages for volatile anesthetic agents. • Compare and contrast the physical properties of inhalational anesthetics and their effects on organ systems. • Discuss biotransformation and contraindications related to specific volatile anesthetic agents.
HISTORY • 1840’S • Nitrous oxide • Diethyl Ether • Chloroform • 1920’s – 1940’s • Ethylene • Cyclopropane • Divinyl Ether • 1950’s • Discoveries in fluorine chemistry
INHALATIONAL AGENTS • Nitrous Oxide (N20) • Halothane (Fluothane) • Enflurane (Ethrane) • Isoflurane (Forane) • Desflurane (Suprane) • Sevoflurane (Ultane)
PROPOSED MECHANISMS OF INHALATION ANESTHETIC ACTION • General anesthesia is an altered physiologic state characterized by reversible loss of consciousness, analgesia of the entire body, amnesia, and to some degree muscle relaxation • Meyer-Overton Rule (Critical Volume Hypothesis) • Protein Receptor Hypothesis (Agent Specific Theory) • Microcrystaline Theory • Alteration in Neurotransmitter Availability
MINIMUM ALVEOLAR CONCENTRATION • MAC defined as • MAC mirrors brain partial pressure, allows comparisons of potency between agents, and provides a standard for experimental evaluations • Patient specific • MAC %: • N2O • Halothane • Ethrane • Forane • Desflurane • Sevoflurane • Factors affecting MAC
NITROUS OXIDE • Physical Properties • Effects on Organ Systems: • Cardiovascular • Respiratory • Cerebral • Neuromuscular • Renal • Hepatic • Gastrointestinal • Biotransformation and Toxicity • Contraindications • Drug Interactions
HALOTHANE • Physical Properties • Effects on Organ Systems: • Cardiovascular • Respiratory • Cerebral • Neuromuscular • Renal • Hepatic • Biotransformation and Toxicity • Contraindications • Drug Interactions
ETHRANE • Physical Properties • Effects on Organ Systems: • Cardiovascular • Respiratory • Cerebral • Neuromuscular • Renal • Hepatic • Biotransformation and Toxicity • Contraindications • Drug Interactions
FORANE • Physical Properties • Effects on Organ Systems: • Cardiovascular • Respiratory • Cerebral • Neuromuscular • Renal • Hepatic • Biotransformation and Toxicity • Contraindications • Drug Interactions
DESFLURANE • Physical Properties • Effects on Organ Systems: • Cardiovascular • Respiratory • Cerebral • Neuromuscular • Renal • Hepatic • Biotransformation and Toxicity • Contraindications • Drug Interactions
SEVOFLURANE • Physical Properties • Effects on Organ Systems: • Cardiovascular • Respiratory • Cerebral • Neuromuscular • Renal • Hepatic • Biotransformation and Toxicity • Contraindications • Drug Interactions
IDEAL INHALATIONAL ANESTHETIC • Rapid onset – rapid recovery • Easy to administer • Possess clear indication of anesthetic depth • No significant effect on organ systems • High margin of safety for all age groups • Inexpensive
CLINCAL CASE STUDIES • 78 year old male presents to OR from ED diagnosed with a small bowel obstruction. PMH: CHF, CAD, and history of seizures 2 years prior to admission. • 26 year old female presents to OR for emergent cesarean section. General anesthesia is initiated due to fetal distress (bradycardia and acidosis). PMH: negative. • 47 year old male presents to OR for elective colon resection. PMH: CRFand arthritis. • 6 year old female presents to the OR for elective adenoidectomy and tonsillectomy. PMH: negative.
REFERENCES • Morgan, G.E., Mikhail, M.S., and Murray, M.J. (2006). Clinical Anesthesiology. (4th ed.) New York, NY: McGraw-Hill. • Stoelting, R.K. (1999). Pharmacology & Physiology in Anesthetic Practice. (3rd ed.) Philadelphia, PA: J.B. Lippincott Company.