LOCAL/REGIONAL ANESTHESIA

1. LOCAL/REGIONAL ANESTHESIA SFC Shrader

2. Advantages/Disadvantages of Regional and Local Anesthesia.

3. advantages • patient remains conscious • maintain his own airway • aspiration of gastric contents unlikely • smooth recovery requiring less skilled nursing care as compared to general anesthesia

4. advantages • postoperative analgesia • reduction in surgical stress • earlier discharge for outpatients • less expense

5. Disadvantages: • patient may prefer to be asleep • practice and skill is required for the best results • some blocks require up to 30 minutes or more to be fully effective • analgesia may not always be totally effective-patient may require additional analgesics, IV sedation, or a light general anesthetic

6. Disadvantages: • toxicity may occur if the local anesthetic is given intravenously or if an overdose is injected • some operations are unsuitable for local anesthetics, e.g., thoracotomies

7. Mechanism of Action of Local Anesthetics • produce a blockade of nerve impulse by preventing increases in permeability of nerve membranes to Na ions, slowing the rate of depolarization • interact directly with specific receptors on the sodium channel, inhibiting sodium influx • do not alter the resting membrane resting potential or threshold potential

8. Selection of Local/Regional Anesthetics • specific nerves to be blocked • onset time or latency • required duration of effect

9. Systemic Toxicity of Local Anesthetics • Drugs-not a great difference in toxicity between equally potent local anesthetics-one of low toxicity when a large dose is required • Site of injection-vascular sites lead to rapid absorption • accidental I.V. injection is the most common cause of toxicity

10. Systemic Toxicity of Local Anesthetics • Addition of Epinephrine-causes local vasoconstriction and slows absorption • Follow recommended dose

11. Signs and Symptoms of Local/Regional Anesthesia Toxicity • CNS • CV

12. Signs/symptoms of central nervous system (CNS) toxicity-- CNS toxicity will be enhanced by acidosis and hypoxia, both of which can occur very rapidly if convulsions appear (when breathing may stop and the excessive muscular activity consumes oxygen stores)

13. S/S CNS Toxicity • Unconsciousness • Generalized convulsions • Coma • Apnea • Numbness of the mouth and tongue, metal taste in the mouth

14. S/S CNS Toxicity • Light-headedness • Tinnitus • Visual disturbance • Muscle twitching • Irrational behavior and speech

15. Cardiovascular toxicity • slowing of the conduction in the myocardium • myocardial depression • peripheral vasodilatation • usually seen after 2 to 4 times the convulsant dose has been injected

16. Prevention and Treatment of Local/Regional Anesthesia Toxicity

17. prevention • Always use the recommended dose • Aspirate through the needle or catheter before injecting the local anesthetic. Intravascular injection can have catastrophic results. • If a large quantity of a drug is required, use a drug of low toxicity and divide the dose into small increments, increasing the total injection time • always inject slowly (<10 ml/min) and communicate with the pt

18. treatment • All necessary equipment to perform resuscitation, induction, and intubation should be on hand before injection of local/regional anesthetics • Manage airway and give oxygen • Stop convulsions if they continue for more than 15 to 20 seconds • Thiopental 100 mg to 150 mg IV • or Diazepam 5 mg to 20 mg IV