ANESTHESIA OVERVIEW

– combine IV agents with local anesthetics
• For more extensive procedures: balanced anesthesia
– short-acting IV agents with opioids and nitrous oxide
• For major surgery: general anesthesia
• Anesthesia is used to relax (sedate) you, block pain sensations (analgesia and anesthesia), induce sleepiness or forgetfulness (amnesia), or make you unconscious for your surgery.
• Analgesia - blocking the conscious perception of pain • Amnesia - preventing memory formation • Relaxation - preventing unwanted movement or muscle tone • Obtundation of reflexes, preventing exaggerated autonomic reflexes
– IV drugs to induce anesthetic state – inhaled anesthetics to maintain anesthesia – +/- neuromuscular blocking agents for muscle relaxation
• There are several drugs and gases that can be combined or used alone to produce general anesthesia. • When anesthetics reach the bloodstream, the drugs that affect the brain pass through other blood vessels and organs so they are often affected too. Therefore, patients must be carefully monitored.
REFLEX
Eyelash absent Eyelid absent and conjunctival depressed Corneal depressed Laryngeal depressed Carinal depressed
Regular larg, small volume Irreg diaphragmatic small volume apnea
• General anesthesia is used for more extensive procedures or for procedures that aren't amenable to regional anesthesia. The medications used in general anesthesia are given intravenously or by inhalation. The drugs circulate in your bloodstream to all areas of your body, including your brain. It results in amnesia, paralysis and analgesia.They can suppress all of your protective reflexes, such as coughing, gagging and even breathing. Consequently, a general anesthetic requires the use of a mask or breathing tube during the surgery.
Inhaled General Anesthetics
• • • • • • • Nitrous oxide Halothane Enflurane Isoflurane Sevoflurane Desflurane Xenon (rarely used)
Anesthesia Machine
IV General Anesthetics and Sedative Agents
STAGE ONE Analgesia Two excitement Threeanesthesia Plane I Plane II Plane III
RESPIRATION Regular small volume irregular Regular large volume
EYES PUPIL Central small Divergent large Central small
ANESTHESIA:OVERVIEW
Chen Datong MD
• Anesthesia is the use of medications and close monitoring to provide comfort and maintain vital life functions during surgery or other medical procedures.
Central medium Central medium
Plane IV
Central large
Fouroverdose
Central full dilatation
Cardiac depressed
Curved (Macintosh) 1. The tip of the blade is advance into the space between the base of the tongue and the pharyngeal surface of the epiglottis. 2. Move the blade forward and upward to elevate the epiglottis and expose the glottic opening. Straight (Jackson-Wisconsin) or Straight with curved tip (Miller) 1. The tip of the blade is passed beneath the laryngeal surface of the epiglottis 2. Same with curve blade
• • • • • • • • Thiopental Methohexital Propofol Etomidate Ketamine Diazepam Midazolam Lorazepam • These drugs quickly reach the brain and their effect is dependent on several factors including the volume in which the drug is distributed in the body, the fat-solubility of the drug, and how quickly the body eliminates the drug.
Four stages of Anesthesia and increasing depth of CNS depression 1. Analgesia: ↓awareness of pain without amnesia
2. Excitement: delirium and excited with amnesia 3. Surgical anesthesia: unconscious, no pain reflexes, regular respiration and BP maintained 4. Medullary depression: severe respiratory and CV depression; death without CV and respiratory support
• Anesthesia: reversible, druginduced loss of sensation in the entire body or in a part of it • Local anesthetic agents: agents that block sensory and motor nerve conduction to produce temporary loss of sensation without a loss of consciousness • General anesthetics: CNS depressants with action that can be induced and terminated more rapidly than sedative hypnotics • Preanesthetic medication: may include sedatives, opioids, tranquilizers and anticholinergic agents
• It is not completely clear exactly how general anesthetics work at a cellular level, but it is speculated that general anesthetics affect the spinal cord (resulting in immobility), the brain-stem reticular activating system (resulting in unconsciousness) and the cerebral cortex (seen as changes in electrical activity on an electroencephalogram).