Techniques of Local Anesthesia Administration

Techniques for Applying Local Anesthesia

• Topical anesthesia: applied to mucous membranes, including the eyes, lips, gums, and throat, using creams, sprays, suppositories, drops, and lozenges.
• Infiltration anesthesia: direct injection into tissue immediate to the surgical site, where the drug diffuses into tissue to block a specific group of nerves in a small area close to the surgical site.
• Nerve block anesthesia: direct injection into tissue that may be distant from the operation site, affecting nerve bundles serving the surgical area.
• Spinal anesthesia: injection into the cerebral spinal fluid (CSF), affecting a large, regional area such as the lower abdomen and legs.
• Epidural anesthesia: injection into the epidural space of the spinal cord, commonly used in obstetrics during labor and delivery.

General Anesthetics

• Block the flow of sodium into neurons, delaying nerve impulses and reducing neural activity.
• Produce unconsciousness and a lack of responsiveness to painful stimuli.

Stages of General Anesthesia

• Stage I: Loss of pain, where the patient loses general sensation but may be awake.
• Stage II: Excitement and hyperactivity, where the patient may be delirious and try to resist treatment.
• Stage III: Surgical anesthesia, characterized by relaxation of skeletal muscles and pupil dilation.
• Stage IV: Respiratory and cardiovascular paralysis, which is usually avoided during general anesthesia.

Administration of General Anesthetics

• Induction: the period from the beginning of anesthesia until stage 3, or surgical anesthesia, is reached.
• Maintenance: the period from stage 3 until the surgical procedure is complete.
• Recovery: the period from discontinuation of the anesthetic until the patient has regained consciousness.

Intravenous General Anesthetics

• Examples include ketamine, propofol, and others.
• Adverse effects include allergic reactions, dysrhythmias, respiratory depression, CNS depression, shivering, headache, nausea, and vomiting.

Inhaled General Anesthetics

• Examples include nitric oxide and isoflurane.
• Prevent the flow of sodium into neurons in the CNS, delaying nerve impulses and reducing neural activity.
• Primary use is with IV agents to maintain loss of consciousness, and used alone for dental procedures.

Adjuncts to Anesthesia

• Medications given to complement the effects of general anesthesia and treat anticipated side effects.
• Examples include anticholinergic, benzodiazepine, cholinergic agonists, dopamine blockers, neuromuscular blockers, opioids, and phenothiazine.

Neuromuscular Blockers

• Used to cause paralysis (loss of muscular function) for surgical procedures and to facilitate mechanical ventilation.
• Examples include succinylcholine (Anectine, Quelicin), mivacurium (Mivacron), and tubocurarine.

Prototype Drug: Succinylcholine (Anectine, Quelicin)

• Therapeutic class: skeletal muscle paralytic drug; neuromuscular blocker.
• Pharmacologic class: depolarizing blocker; acetylcholine receptor blocking drug.
• Actions and uses: acts on cholinergic receptor sites at neuromuscular junctions, causing depolarization and muscle contraction, followed by paralysis.
• Pharmacokinetics: onset is 0.5-1 min IV, peak is variable within minutes, and duration is 2-3 min IV.
• Adverse effects: complete paralysis of the diaphragm and intercostal muscles, bradycardia, and respiratory depression.