LOCAL/REGIONAL ANESTHESIA SFC Shrader

Advantages/Disadvantages of Regional and Local Anesthesia.

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

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

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

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

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

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

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

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

Signs and Symptoms of Local/Regional Anesthesia Toxicity CNS CV

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)

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

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

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

Prevention and Treatment of Local/Regional Anesthesia Toxicity

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

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