Chapter 11 General and Local Anesthetics Flashcards
Anesthetics
Drugs that reduce or eliminate pain by depressing nerve function in the central nervous system (CNS) and peripheral nervous system
General anesthesia
complete loss of consciousness and loss of body reflexes, including paralysis of respiratory muscles.
Local anesthesia
no paralysis of respiratory function; elimination of pain sensation in the tissues innervated by anesthetized nerves
Adjunct anesthetics
Drug that enhances clinical therapy when used simultaneously with another drug
Balanced anesthesia
The practice of using combinations of different drug classes rather than a single drug to produce anesthesia
Overton-Meyer theory
- For all anesthetics, potency varies directly with lipid solubility.
- Fat-soluble drugs are stronger anesthetics than water-soluble drugs.
- Nerve cell membranes have high lipid content, as does the blood–brain barrier.
- Lipid-soluble anesthetic drugs can therefore easily cross the blood–brain barrier to concentrate in nerve cell membranes
Malignant hyperthermia
- Occurs during or after volatile inhaled general anesthesia or use of the neuromuscular blocking drug (NMBD) succinylcholine
- Sudden elevation in body temperature (greater than 104° F)
- Tachypnea, tachycardia, muscle rigidity
- Life-threatening emergency
- Treated with cardiorespiratory supportive care and dantrolene (skeletal muscle relaxant)
Antihypertensives
increased hypotensive effects
Beta blockers\
increased myocardial depression
Dexmedetomidine (Precedex)
- Alpha-2 adrenergic receptor agonist
- Dose-dependent sedation, decreased anxiety, and analgesia without respiratory depression
- Use: procedural sedation, surgeries of short duration.
- Short half-life, and the patient awakens quickly upon withdrawal of the drug.
- Sedation of mechanically ventilated patients in the intensive care unit (ICU)
Ketamine
- Intravenous administration use for both general anesthesia and moderate sedation
- Rapid onset of action
- Low incidence of reduction of cardiovascular, respiratory, and bowel function
- Adverse effects: disturbing psychomimetic effects, including hallucinations
Nitrous Oxide
- “Laughing gas”
- Only inhaled gas currently used as a general anesthetic
- Weakest of the general anesthetic drugs
- Used primarily for dental procedures or as a supplement to other, more potent anesthetics
Propofol (Diprivan)
- Parenteral general anesthetic
- Used for the induction and maintenance of general anesthesia
- Sedation for mechanical ventilation in ICU settings
- Lower doses: sedative-hypnotic for moderate sedation
- Monitor triglycerides if administered with total parenteral nutrition
Sevoflurane (Ultane)
- Fluorinated ether
- Widely used
- Rapid onset and rapid elimination
- Especially useful in outpatient surgery settings
- Nonirritating to the airway
- Greatly facilitates induction of an unconscious state, especially in pediatric patients
Moderate Sedation
- Also called conscious sedation and procedural sedation
- Does not cause complete loss of consciousness and does not normally cause respiratory arrest.
- Combination of an IV benzodiazepine (e.g., midazolam) or propofol and an opiate analgesic (e.g., fentanyl or morphine)
- Anxiety and sensitivity to pain are reduced, and the patient cannot recall the procedure.
Moderate Sedation uses
- Used for diagnostic procedures and minor surgical procedures that do not require deep anesthesia
- Preserves the patient’s ability to maintain own airway and to respond to verbal commands
- Rapid recovery time and greater safety profile than general anesthesia
Types of Local Anesthesia
- Spinal or intraspinal
- Intrathecal
- Epidural
- Infiltration
- Nerve block
- Topical
- Peripheral nerve catheter attached to a pump containing the local anesthetic: Pain Buster and On-Q pump
Local anesthetics are used for:
- Surgical, dental, and diagnostic procedures
- Treatment of certain types of chronic pain
- Spinal anesthesia: to control pain during surgical procedures and childbirth
Local anesthetics are given by:
Infiltration anesthesia
Nerve block anesthesia
“Spinal headache”
- 70% of patients who either experience inadvertent dural puncture during epidural anesthesia or undergo intrathecal anesthesia.
- Usually self-limiting
- Treatment: bed rest, analgesics, caffeine, blood patch
Neuromuscular Blocking Drugs
- Also known as NMBDs
- Prevent nerve transmission in skeletal and smooth muscle, resulting in muscle paralysis
- Also paralyze the skeletal muscles required for breathing: the intercostal muscles and the diaphragm
- Used with anesthetics during surgery
- When used during surgery, artificial mechanical ventilation is required.
