Chemicals {anesthesia}| {anesthetic} can inhibit voluntary-muscle movements {immobility}, inhibit involuntary-muscle movements {muscle relaxation}, lower consciousness to sleep-like level with dreaming {narcosis, anesthesia} {hypnosis, anesthesia}, inhibit pain {analgesia, anesthesia}, cause no memory of episode {amnesia, anesthesia}, and lower brain activity {sedation, anesthesia}.
Anesthesia can be borderline anesthesia {hypesthesia}. Light anesthesia allows consciousness but blocks muscle movements.
Deep anesthesia blocks consciousness and muscle movements.
levels
Anesthesia first affects higher brain functions {anesthetic depth}. The lightest anesthesia causes analgesia, memory loss, and euphoria. Deeper anesthesia causes consciousness loss, rapid shallow breathing, sweating, and flushing. Complete anesthesia causes quiet, regular breathing, with eyeballs moving rhythmically. It does not affect reflexes. In deep anesthesia, first reflexes fail, then breathing becomes shallow, and finally people die.
levels: measurement
Inhaled anesthetics have alveoli concentrations {minimum alveolar concentration} (MAC) that block movements in response to stimuli in 50% of patients. Inhaled anesthetics have lower alveoli concentrations {minimum alveolar concentration-aware} {MAC-aware} that block stimulus awareness in 50% of patients. Intravenous anesthetics have blood-plasma concentrations {end-tidal concentration} that block movements in response to stimuli in 50% of patients.
Blood pressure, heart rate, sweating, and tear secretion combined {PRST score} indicate awareness level.
EEG power spectrum shows waves at 3 Hz below alpha-wave frequency. Stimuli cause EEG evoked potentials that appear at various times after event. Anesthesia reduces or delays evoked potentials. In anesthesia, three auditory evoked potentials typically happen 20 ms to 45 ms after stimulus {AEP index}.
local anesthesia
Local anesthesia makes body parts feel non-existent, rather than senseless or paralyzed. Local anesthesia inhibits touch and pain perception with lidocaine and similar chemicals, by injection into local nerves {nerve block}, spinal-cord epidural region {epidural anesthesia}, or subarachnoid spaces {spinal anesthesia}.
Local anesthesia does not cause amnesia and maintains consciousness. Local anesthesia can combine with benzodiazepine sedation {conscious sedation}, which causes amnesia but maintains consciousness.
biology
Anesthetics typically affect cell-membrane proteins. Anesthetics stimulate vagus nerve, which detects lung expansion.
biology: brain
Anesthesia can have prolonged brain-potential synchronization. Anesthetics seem to work on whole brain, not isolated circuits or regions [Alkire et al., 1998].
biology: drugs
Barbiturates, high-pressure nitrogen, alcohols, cleaning fluids like trichloroethene, industrial solvents, steroids, ether, chloroform, xenon, nitrous oxide, phencyclidine, opioids, and cholinergic agents can cause reversible consciousness loss.
Different drugs separately affect memory, voluntary muscles, and perception. Alfentanil, chloroform, cocaine, enflurane, ethyl p-aminobenzoate [1890], etomidate, halothane, isoflurane, ketamine, nitrous oxide, procaine, and propofol are anesthetics. Ethyl p-aminobenzoate [1890] is a local anesthetic.
Different anesthetics can have cross-tolerance.
biology: EEG
Bispectral index can measure anesthesia depth.
biology: endorphins
Perhaps, anesthetics affect enkephalin or endorphin chemistry.
biology: hippocampus
Perhaps, decreased hippocampus activity causes amnesia.
biology: receptors
Perhaps, anesthetics bind to NMDA or GABA-A receptor. Some anesthetics bind to microtubules. Anesthetics inhibit signal transfer between neurons [Alkire et al., 1997] [Alkire et al., 1999] [Antkowiak, 2001] [Franks and Lieb, 1994] [Franks and Lieb, 1998] [Kulli and Koch, 1991] [Lamme et al., 1998] [Logothetis et al., 1999] [Logothetis et al., 2001] [Rosen and Lunn, 1987] [Sennholz, 2000] [Tamura and Tanaka, 2001].
procedure
Before operations, patients have sedative, intravenous benzodiazepine, and oxygen.
Next comes intravenous thiopental or propofol, whose effects wear off quickly, followed by intravenous muscle relaxant {rapid sequence induction}, for quick anesthesia. Alternatively, next comes inhaled nitrous oxide and oxygen then inhaled halothane, desflurane, or sevoflurane {inhalation induction} {mask induction}, for slow anesthesia. Alternatively, next comes intravenous sufentanyl or propofol {intravenous anesthesia}.
After surgery, neostygmine allows muscle movement, and morphine inhibits pain.
High air pressures aid recovery from anesthesia.
results: amnesia
Anesthesia can cause no memory of surgery.
results: immobility
Anesthesia can cause no reaction to stimuli and no voluntary-muscle movement. Immobility can result from inhibition at spinal-cord GABA receptors.
results: memory
After anesthesia at level that precludes consciousness, patients can remember things that happened in surgery. Intense stimuli can cause memory without consciousness [Kihlstrom, 1996] [Levinson, 1965] [Merikle and Daneman, 1996].
Biological Sciences>Medicine>Drug>Kinds>Anesthetic
4-Medicine-Drug-Kinds-Anesthetic
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Date Modified: 2022.0224