Anesthesiology Basics

Anesthesia

• Anesthesia is a state of reduced neurologic function, characterized by complete or partial loss of sensation.

Moderate Sedation

• Also known as conscious sedation or procedural sedation
• Does not necessarily cause complete loss of consciousness and does not normally cause respiratory arrest
• Uses a combination of several drugs from different groups
• Drugs may be given by IV, IM, spinal, or oral routes
• Allows the patient to relax yet maintain their own open airway and respond to verbal commands
• Used for diagnostic procedures and minor surgical procedures that do not require deep anesthesia

General Anesthesia

• Involves complete loss of consciousness, loss of body reflexes, elimination of pain and other sensations throughout the entire body, and skeletal and smooth muscle paralysis
• General anesthetics are drugs that induce general anesthesia, and are most commonly used to induce anesthesia during surgical procedures
• Often achieved by the use of one or more drugs, which allows for smaller doses of each drug and better control of the patient's anesthetized state
• Can be classified into inhalational anesthetics (volatile liquids or gases that are vaporized or mixed with oxygen) and parenteral anesthetics (given IV and used for induction and/or maintenance of general anesthesia, induction of amnesia, and as adjuncts to inhalation anesthetics)

Adjunct Anesthetics

• "Helper drugs" that complement the use of general anesthetics and are used simultaneously for anesthesia induction, sedation, reduction of anxiety, and amnesia
• Examples include neuromuscular blocking agents, sedative hypnotics or anxiolytics, propofol, benzodiazepines, barbiturates, hydroxyzine, promethazine, opioid analgesics, anticholinergics, and antiemetics

Mechanism of Action and Drug Effects

• The mechanism of action of general anesthetics varies widely and is not easily explained by a structure-receptor relationship
• Fat-soluble drugs are stronger anesthetics than water-soluble drugs
• The overall effect of general anesthetics is a progressive reduction of sensory and motor CNS functions
• The degree and speed of this process vary with the anesthetics and adjuncts used, along with their dosages and routes of administration

Adverse Effects of General Anesthesia

• Sites primarily affected include the heart, peripheral circulation, liver, kidneys, and respiratory tract
• Malignant hyperthermia is an uncommon but potentially fatal adverse effect, characterized by sudden elevation in body temperature, tachypnea, tachycardia, muscle rigidity, and can be treated with dantrolene

Local Anesthesia

• Types include central (spinal or intraspinal anesthesia), peripheral (infiltration, nerve block, and topical anesthesia)
• Mechanism of action involves blocking the generation and conduction of nerve impulses by blocking the movement of certain ions
• Adverse effects include systemic effects on circulatory and respiratory function, which depend on where and how the drug is administered

Lidocaine

• One of the most commonly used local anesthetics, available in several strengths and concentrations with epinephrine
• Used for both infiltration and nerve block anesthesia, and also available in topical form
• Parenteral lidocaine is also used to treat certain cardiac dysrhythmias

Neuromuscular Blocking Drugs (NMBDs)

• Prevent nerve transmission in skeletal and smooth muscles, leading to paralysis
• Often used as adjuncts with general anesthetics, and require mechanical ventilation to prevent brain damage or death by suffocation
• Can be classified into depolarizing (e.g., succinylcholine) and non-depolarizing (e.g., mivacurium, atracurium, rocuronium, vecuronium, dexacurium, pancuronium, and tubocurarine) types
• Indications include maintaining controlled ventilation during surgical procedures, endotracheal intubation, reducing muscle contraction in an area that needs surgery, and as diagnostic drugs for myasthenia gravis

Nursing Implications

• Always assess past history of surgeries and response to anesthesia
• Assessment is vital during preoperative, intraoperative, and postoperative phases
• Monitor vital signs, baseline lab work, ECG, oxygen saturation, and ABCs
• Watch for sudden elevations in body temperature during recovery, and monitor for cardiovascular depression, respiratory depression, and complications of anesthesia
• Implement safety measures during recovery, especially if motor or sensory loss occurs due to local anesthesia
• Reorient the patient to their surroundings and teach them about postoperative turning, coughing, and deep breathing