local and general anesthetics (ch 26-27)

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Chapter 26:

Chapter 26 Local Anesthetics

Local Anesthetics:

Local Anesthetics Suppress pain by blocking sodium channels, thereby blocking impulse conduction along axons Only in neurons located near the site of administration Suppress pain without generalized depression of nervous system

Properties of Individual Local Anesthetics:

Properties of Individual Local Anesthetics Procaine Lidocaine Cocaine Other local anesthetics

Lidocaine:

Lidocaine Most widely used local anesthetic Topical and injectable applications Effects extended if given with epinephrine Also used for cardiac dysrhythmias

Lidocaine:

Lidocaine Preparations Cream Ointment Jelly Solution Aerosol Patch

Other Local Anesthetics:

Other Local Anesthetics Topical Therapeutic uses Systemic toxicity Injection Infiltration, nerve block, IV regional, epidural, and spinal (subarachnoid) Should be administered by anesthesiologist IV and monitoring required

Chapter 27:

Chapter 27 General Anesthetics

General Anesthetics :

General Anesthetics General anesthetics are drugs that produce unconsciousness and a lack of responsiveness to all painful stimuli. Local anesthetics do not reduce consciousness, and they blunt pain only in a limited area.

Pain:

Pain Analgesia Loss of sensibility to pain Anesthesia Loss of pain and loss of all other sensations

General Anesthetics :

General Anesthetics Two main groups Inhalation anesthetics IV anesthetics Prior to 1846 Surgery – brutal and excruciatingly painful Strong men and straps used to restrain patient Survival based on surgeon ’ s speed

General Anesthetics:

General Anesthetics Only given by licensed anesthesiologists (physicians) and CRNAs (nurses) Also used to facilitate certain procedures Endoscopy, urologic procedures, radiation therapy, electroconvulsive therapy, transbronchial biopsy, various cardiologic procedures

Neuromuscular Blocking Agents:

Neuromuscular Blocking Agents Surgical procedures require skeletal muscle relaxation. NBAs reduce amount of anesthesia needed. NBAs prevent contraction of all skeletal muscles, including diaphragm and muscles of respiration – flaccid paralysis. 21 million patients undergo surgery. 20,000-40,000 wake up during procedure.

Postanesthetic Medications:

Postanesthetic Medications Analgesics Mild pain – aspirin-like drugs Severe pain – opioids Antiemetics Ondansetron (Zofran) Muscarinic antagonists Abdominal distention and urinary retention Bethanechol

Halothane:

Halothane Adverse effects Hypotension Respiratory depression Requires support with oxygen-rich gas mixture Promotion of dysrhythmias Epinephrine and catecholamines should be used with caution Malignant hyperthermia Genetically predisposed Hepatotoxicity Rare Other adverse effects Elimination 60%-80% by lungs and 20% hepatic

Isoflurane:

Isoflurane Most widely used inhalation anesthetic Properties much like those of halothane Better muscle relaxant, but still requires NMB Not associated with renal or hepatic toxicity

Nitrous Oxide:

Nitrous Oxide Also known as “ laughing gas ” Very low anesthetic potency Very high analgesic potency Never employed as primary anesthetic Frequently combined with other inhalation agents to enhance analgesia 20% nitrous oxide = pain relief of morphine No serious side effects (nausea and vomiting)

Intravenous Anesthetics:

Intravenous Anesthetics Short-acting barbiturates (thiobarbiturates) Benzodiazepines Propofol Etomidate Ketamine Neuroleptic-opioid combination: droperidol plus fentanyl

Short-Acting Barbiturates (Thiobarbiturates):

Short-Acting Barbiturates (Thiobarbiturates) Administered intravenously Employed for induction of anesthesia Two agents Thiopental sodium (Pentothal) Methohexital sodium (Brevital)

Benzodiazepines:

Benzodiazepines Diazepam Induction with IV diazepam (Valium) Unconsciousness within a minute Very little muscle relaxation Midazolam Unconsciousness within 80 seconds Can cause dangerous cardiorespiratory effects

Propofol:

Propofol Actions and uses Unconsciousness develops within 60 seconds and lasts 3-5 minutes Sedative-hypnotic for induction and maintenance of analgesia Mechanical ventilation and procedures Adverse effects Can cause profound respiratory depression Can cause hypotension Risk of bacterial infection

Etomidate:

Etomidate Potent hypnotic agent Used for induction Repeated administration can cause hypotension, oliguria, electrolyte disturbances, and high incidence of postoperative nausea and vomiting

Ketamine:

Ketamine Anesthetic effects Dissociative anesthesia Sedation, immobility, analgesia, and amnesia Adverse psychologic reactions Hallucinations, disturbing dreams, and delirium Soothing environment Therapeutic uses Anesthesia for young children with minor procedures

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