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Local anesthesia mechanism?
- MECHANISM: is by blocking sodium channels in the axons (peripheral NS- outside the brain and spinal cord) near the site of administration, ONLY. it is much less risky. No loss of consciousness.
- *** Propagation of action potential requires movement of sodium ions from outside the axon to the inside.
Local anesthesia AE
- CNS—> excitation followed by depression. Seizures may occur during excitation. Death can occur secondary from depression of respiration.
- Cardiovascular system—> suppress the myocardium and conduction system can cause bradycardia, heart block, cardiac arrest, etc.
- Allergic Rxn—> Ester-type are more prone to cause a severe allergic rxn than Amides. The rxns could go from allergic dermatitis to anaphylaxis.
- In labor/delivery—> depression of the uterine contractility may cause a longer labor time. Also, it could pass through the placenta to the baby causing bradycardia and CNS depression in the neonate.
- Methemoglobinemia—> Hemoglobin changes such as it cannot release O2 to the tissues(usually caused by benzocaine).
Nursing implication on topical local anesthetics:
- Preadministration assessment: The therapeutic goal is to relieve pt. with local disorders related to the skin and mucous. It is very important to identify High risk pts— for ester anesthetic, avoid pts with history of allergies toward these type of drugs.
- Implementation: Administration: Topical use for skin and mucous membranes. Use the smallest dosage in the smallest area. Avoid application to injured skin. Wear gloves.
- ** Epinephrine (vasoconstrictor and Bronchodilator) is often added to prolong effects, stop bleeding, and decrease lidocaine effects systemically.
- Ongoing Evaluation and interventions: Minimize adverse rxns such as systemic toxicity and methemoglobinemia. Systemic toxicity occurs when the anesthetic is absorbed into the general circulation. To avoid this, apply in small areas and avoid injured skin. Methemoglobinemia could cause death. Avoid applying it in pts under 2, unless a provider authorized it. In children and adults apply with caution (benocaine)
Nursing implications on injected local anesthetics:
- Preadministration Assessment: The therapeutic goal is to generate anesthesia for surgical, dental, and obstetric procedures. Avoid Esther-type drugs with pts that have allergic problems with these types of meds.
- Implementation: Administration: Prepared the pt for the injection (injection site, shaving the site when indicated, placing the pt in position for the injection). Administration most be from a provider, dentist, nurse anesthetist)
- Ongoing evaluation and interventions: Be awarded of systemic toxicity (CNS excitement follows by CNS depression— respiration depression) Monitor BP, RR, and state of consciousness. Have resuscitation available. Allergic rxns Rare, but occur most of the time in Ester-type anesthetics. Labor and delivery Bradycardia and CNS depression in neonate. Self-inflicted Injury Unintentional harm after recovering from anesthesia. Spinal Headache and Urinary Retention Headaches could be fix when pt laying supine for 12 hrs.
Stages of general Anesthesia:
- Stage I—> Analgesia, conscious to unconscious.
- Stage II—> Excitement or Delirium, depression of the cerebral cortex.
- Stage III—> Surgical procedure perfumed during this stage, anesthesia deepens.
- Stage IV—> Medullary paralysis, respirations are lost circulatory collapse occurs and ventilatory assistance is necessary.
- Drugs that produce unconsciousness and lack of all stimuli to pain (analgesia). Anesthesia is analgesia plus unconsciousness and other sensations (temperature, touch, taste, etc) . occurs IV or inhaled. Usually induced by IV and maintained by gas.
- ** A mixture of compound need to be mixed to achieve anesthesia, 1) short acting barbiturate, 2) Narcotic analgesic and an anticholinergic, 3) sodium penthothal 4)Inhaled gas such as Nitrous oxide and oxygen 4) Neuromuscular blocking agent—muscle relaxant as needed.
Mechanism of action of inhaled anesthesia:
- uptake occurs in the lungs
- —> Distribution is determine by blood flow (Brain, kidneys, heart, and liver then Skin, skeletal, etc)
- —> Elimination through lungs, hepatic intervention is minimal. Enhances transmission at inhibitory synapses and depressing transmission of excitatory synapses— Interacts with multiple receptors in the brain —Inhibits neurotransmitters that activate the RAS — Easily cross the BBB.
Mechanism of action of IV anesthesia
It is used for the induction and maintenance of general anesthesia, and to promote amnesia — Helps pt to go rapidly through stage I and II — Allows the dose of inhaled anesthetic to be lower. Ultra short acting drugs, CNS depressants.
AE of inhaled anesthesia:
- Respiratory and Cardiac depression can occur with all inhaled anesthetic, mechanical support of ventilator is required.
- *Increase of sensibility of the heart to Catecholamines (epinephrine, norepinephrine) that could cause dysrhythmias.
- *Malignant Hyperthermia predisposition of the rxn is genetic, characterized by muscle rigidity and profound elevation of temperature. Could occur in all inhaled anesthetics, except Nitrous oxide)
- *Aspiration of Gastric Contents Could happen under the effects of anesthesia causing bronchospasm and pneumonia.
AE of IV anesthesia.
- Drug Specific, apneas, bronchospasm, hypotension (less than 90, IV fluids use to get normalize)
- respiratory depression (to avoid it, wake the pt up)
- confusion (let them know what is going on, “Mr. NN you are in the hospital. you just had surgery …)
Nursing implications as a whole.
- Preoperative physical assessment (Baselines)
- Administer preoperative medication (anti-anxiety, pain, antibiotics, etc)
- Preoperative checklist (No food, no piercing , NPO, why are you there, No contacts, dentures)
- Post operative care: wake the patient. Assess for pain and administer pain medication as needed (sedative and analgesic must be decrease to 1/4 for the first dose after surgery)
- Administer O.
- Avoid Heat loss
- Monitor VS and LOC (level of consciousness) closely — we want them to breath!!!
- Monitor Nausea & Vomiting
Less than 8 RR?