... ability of the patient to perform various activities is not significantly impaired hoever, prolonged anesthesia may provoke anxiety or be considered unpleasant or irritating by many patients hen 713it persists for many hours after hospital discharge and should be discussed ith patients before instituting such a block. Local anesthetic agents are commonly classified according to their relative potency and duration of action as follos lo potency and short duration e.g., chloroprocaine, moderate potency and duration e.g., lidocaine and mepivacaine, high potency and long duration e.g., tetracaine, bupivacaine, and etidocaine. Selection of specific blocks are discussed later. Selecting the appropriate local anesthetic for a given regional anesthetic requires consideration of a number of factors, including potency, speed of onset, duration of action of local anesthetics, site and duration of surgery, the degree of muscle relaxation required, and the duration of analgesia desired. Duration of anesthesia ith a given agent varies ith the site of injection and frequently ith the total mass of drug injected. i70s Thus, bupivacaine injected into the epidural space lasts approximately 2 to 3 hours hereas the same dose injected into the brachial plexus may last 10 to 11 hours. Vasoconstrictors, such as epinephrine, are added to increase the duration of action, provide an indication of intravascular injection, and reduce peak serum levels of local anesthetic. The extent to hich epinephrine prolongs the duration of anesthesia depends on the specific local anesthetic used and the site of injection. Vasoconstrictors do not prolong the duration of action of all local anesthetics in all situations Table 2 Table Not Available . Epinephrine prolongs the duration of action of all agents for peripheral nerve blocks except ropivacaine. i33s It also prolongs the duration of action of epidural chloroprocaine, lidocaine, and mepivacaine. The local anesthetic properties of the intrinsically more potent and longer acting agents bupivacaine, etidocaine, tetracaine are influenced less by the addition of epinephrine, particularly hen such agents are used epidurally. Epinephrine does not markedly prolong the duration of motor block by epidural bupivacaine or etidocaine hoever, it does extend the sensory block by these epidural agents. i71s The effects of epinephrine added to agents used for spinal anesthesia are discussed later.The optimal dose of epinephrine is one that ould produce maximal increase in the duration of a local anesthetic agent and minimal hemodynamic effects. Kennedy et al i36s shoed that a supraclavicular brachial plexus block ith 30 mL of 1.6 lidocaine has virtually no hemodynamic effects hereas the same agent ith epinephrine 1200,000 produced a dose-related increase in cardiac rate, cardiac output, and stroke volume that persisted for 90 minutes and decreases in peripheral resistance and concomitant changes in mean arterial pressure that persisted for 120 minutes. Absorbed epinephrine produces predominantly beta-adrenergic effects ith little evidence of alpha-aea1,0l,0l000s000Ti0nsTimes Ne RomanSymbol ArialTimes Ne RomanTimes Ne RomanAnesthesiology Clinics of North AmericaVolume 14 Number 4 December 1996Copyright 1996 . B. Saunders Company 711Ambulatory AnesthesiaCURRENT STATUS OF REGIONAL ANESTHESIA FOR ADULT OUTPATIENTSDermot Fitzgibbon MB, BCh, FFARCSI From the Department of Anesthesiology, University of ashington School of Medicine, Seattle, ashingtonAddress reprint requests toDermot Fitzgibbon, MB, BCh, FFARCSIDepartment of AnesthesiologyUniversity of ashingtonSchool of Medicine1959 N.E. Pacific StreetSeattle, A 98195BENEFITS OF REGIONAL ANESTHESIAThe challenge of anesthesia for ambulatory patients is to provide for rapid return to street readiness ith the most effective postoperative analgesia and minimal undesirable side effects. Regional anesthesia, ith its selective local action and relatively simple equipment, offers an excellent anesthetic choice in an outpatient facility. In addition to limiting the anesthetized area to the surgical site, the common side effects of general anesthesia e.g., nausea, vomiting, lethargy are reduced, the risks and side effects of endotracheal intubation are minimized, patient recovery time may be decreased, and improved analgesia is provided in the postoperative period. i7s i46s A number of studies i51s i82s have evaluated the efficacy of ambulatory regional anesthesia. Urmey et al i82s prospectively recorded data on ambulatory surgery patients at an orthopedic speciality hospital here regional anesthesia as the first-line standard care the various types of anesthesia administered are listed in Table 1 Table Not Available . Only 4.4 of patients ho had regional anesthesia required admission compared ith 12 of general anesthetics. Discharge times ere similar for general, spinal, or epidural anesthesia average of 3 hours patients ho had peripheral nerve blocks ere discharged in approximately 2 hours. Failure of regional anesthesia, necessitating general anesthesia, occurred in only 1 of cases. The authors concluded that regional anesthesia in an ambulatory center is effective in all but a small percentage of patients. Osborne i51s evaluated outcome for 6000 consecutive procedures in a major public teaching hospital day surgery unit. Anesthesia-related complications ere more frequent ith general anesthesia 1114 than ith regional anesthesia 1180 or local anesthesia plus sedation 712TABLE 1 -- ANESTHETIC TECHNIQUES FOR AMBULATORY ORTHOPEDIC PROCEDURES From Urmey F, Stanton J, Sharrock NE Initial one-year experience of a 97.3 regional anesthesia ambulatory surgery center. Reg Anesth 1869, 1993 Churchill Livingstone, ith permission. Not Available1780. Recovery ith regional or local anesthesia as significantly shorter than after general anesthesia. Despite the potential advantages cited regional anesthesia should not be considered universally appropriate. Factors that contribute to a successful regional anesthetic include the appropriate selection of patients, anesthetic technique, and local anesthetic, use of sedative and hypnotic agents, and the skill of the anesthesiologist. Prior screening of patients through preanesthesia testing PAT clinics is very useful in determining the acceptability of patients for a regional anesthetic. Very young or excessively anxious patients may be poor candidates. Similarly, obese patients may present technical problems, especially for central neuraxial blocks. Patients of American Society of Anesthesiologists ASA physical status III or IV may be particularly good candidates for ambulatory regional anesthesia compared to general anesthesia, especially if their systemic diseases are medically stable.SELECTION OF TECHNIQUE AND LOCAL ANESTHETICOutpatient regional techniques require some modification from standard inpatient procedures. Idedrenergic effects at TABLE 2 -- DURATION OF ACTION OF LOCAL ANESTHETICS AND EF...
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