Download to read offline
Reginal Block Anesthesia-anesthesia topic
- 1.
- 2. Objectives • Mastering thebasic category of local anesthesia • Mastering the diagnosis and treatment of local anesthetic toxicity. • Being familiar with the performing of subarachnoid space puncture
- 3. Key Concepts • CNSsymptoms of local anesthetic toxicity. • Treatments of local anesthetic toxicity.
- 4. Introduction • Regional anesthesiais defined as such state in which a patient under waking consciousness is administered local anesthetics regionally, therefore the conduction function of sensory nerves in a part of body is blocked temporarily while the motor nerve conduction is kept intact, or meanwhile is blocked to some extent only.
- 5. • The advantagesof regional anesthesia include that it is simple convenient and easy to be carried out and also it is safe and reliable
- 6. Common regional anesthesia includefour classes: • topical anesthesia, • local infiltration anesthesia, • field block • nerve blockade. • The latter can be classified further into nerve trunk blockade, epidural block and spinal analgesia.
- 7. Topical anesthesia • Analgesiastate induced by the effects of local anesthetics with potent permeability on local mucous membrane is called topical anesthesia . Topical anesthesia is frequently used in the superficial operation or examination as that on eyes, nasal cavity, oral cavity, throat, trachea etc
- 8. • The peripheralnerves in cornea are accessible, 0. 5% - 1% of tetracaine can be administered and the potency may last for 30 minutes. In case needed, the drug can be administered repeatedly.
- 9. Local infiltration anesthesia •The local infiltration anesthesia refers to the process that the local anesthetics is injected along the operative incision line to block the nerve endings in tissues
- 10. Procedure • Take aintradermal injection needle, have the bevel of the pinhead tight touch with and then puncture into the skin of patient to inject the anesthetics, resulting in an orange peel-like nodule , If the distant tissues need to be infiltrated with the drug, the needle should first puncture through the spot which has been infiltrated early with the anesthetics to remit the puncture-associated pain.
- 11. Announcements • Always dopumpback first before injecting the anesthetics in order to avoid the possibility of getting the drug into blood vessels directly • Never exceed the maximal dose allowed for every injection in order to avoid the toxic reactions of the anesthetics. • In the spots of infection or tumor, local infiltration anesthesia is unsuitable.
- 12. Field block • Fieldblock is regarded as the operation that around the operation area the anesthetics is injected, involving the circumference and bottom, to block the nerve trunk and endings throughout the operation area
- 13. • Field blockapplies to such outpatient operation as excision of small cysts or lump as well as biopsy . The key points and drug preparation of field block are the same as that for local infiltration, but with the following advantages: Avoiding the direct injection of anesthetics into pathological or tumor tissues;
- 14. Nerve block • nervetrunk blockade, • epidural block and spinal analgesia. • Brachial plexus block • Sciatic nerve block • epidural block and spinal analgesia
- 15. Systemic toxic reactionsof local anesthetics • Causes; • Accident injection of local anesthetics into blood vessels during anesthesia or its dose used exceeding maximal safety dose.
- 16. Central nervous system Symptoms •Early manifestations include perioral numbness, paresthesia of tongue, dizziness, tinnitus, dirmess of vision. Generally, the excitive symptoms of central nervous system (restlessness, agitation, ) precede the inhibition ones ( drowsiness, coma).
- 17. Protective measures • Neverexceed the safety dose of local anesthetics. • Reduce the dose appropriately, depending on the patient’s conditions and injection site. • Always do aspiration first before injection. Only when no blood was withdrawn can we start injection, and during injection of test dose, we should observe whether any uncomfortable reactions appear. • For those with no contraindications involving vasopressors, add appropriate amount of epinephrine in local anesthetics solution to delay the absorption of drug. • Give appropriate amount of benzodiazepines, to raise the threshold of toxicity, and observe prodromes closely of the reactions. Once symptoms occur, stop injection immediately.
- 18. Treatments • the treatmentsfor the general toxic reaction of local anesthetics mainly involve supporting therapy. • Stop using local anesthetics. • Sedation and hyperventilation may raise the threshold of seizure. • Maintain sufficient ventilation and oxygenation because anoxia and acidosis may increase the general toxicity of local anesthetics. When needed, administer scoline (1-2 mg,/kg)to stop convulsion and perform tracheal intubation for positive pressure ventilation. • scoline may stop the convulsion in seizure, but can not stop the epilepsy in central nervous system. Intravenous injection of midazolam (2 - 5 mg) or propofo(1 mg/kg) may stop seizure itself.
- 19. summary • Regional anesthesiais defined as a patient under waking consciousness is administered local anesthetics regionally, therefore the conduction function of sensory nerves in a part of body is blocked temporarily.
- 20. summary • Common regionalanesthesia includes the following; topical anesthesia, local infiltration anesthesia, field block and nerve blockade. The latter can be classified further into nerve trunk blockade, epidural block and spinal analgesia.
- 21. summary • The greatestimmediate risk of regional anesthesia is systemic toxicity of local anesthetics from intravascular injection and rapid or excessive amounts absorbed . Anesthesiologists need to use local anesthetics with cautions.