***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    Input: This study assessed the minimum dose of clonidine required to prolong the duration of both anesthesia and analgesia after axillary brachial plexus blockade . Eighty patients scheduled for elective h and surgery were divided into eight groups in a r and omized , double-blind fashion . An axillary brachial plexus block was performed with 40 mL 1 % mepivacaine plus 1:200,000 epinephrine . The control group received no clonidine . In the other groups , increasing doses of clonidine ( 0.1 , 0.2 , 0.3 , 0.4 , 0.5 , 1 , and 1.5 micro g/kg ) were added to the local anesthetic solution . Onset time , duration of anesthesia and analgesia , postoperative pain score , intake of analgesics , and adverse effects were recorded . The eight groups were comparable in terms of onset time , postoperative pain score , and analgesic requirement . The minimum dose of clonidine required to significantly prolong the duration of analgesia and anesthesia was , respectively , 0.1 and 0.5 micro g/kg . No side effects ( sedation , drowsiness , bradycardia , arterial hypotension ) were reported . We conclude that the dose of clonidine required to prolong significantly the duration of both anesthesia and analgesia after axillary brachial plexus blockade is 0.5 micro g/kg and that , at this dose , clonidine may be used without important reported side effects even in out patients . ( Anesth Analg 1996;83:1046 - 50 STUDY OBJECTIVE To determine whether the addition of morphine to the axillary block local anesthetic solution provides improved or prolonged postoperative analgesia . DESIGN Prospect i ve , r and omized , double-blind clinical trial with 24-hour follow-up . SETTING Ambulatory unit of a large academic referral center . PATIENTS Consecutive healthy volunteers scheduled for elective upper extremity surgery . INTERVENTIONS Patients in the treatment group ( AX ) were given intravenous ( IV ) saline and had morphine 0.1 mg/kg added to their axillary block solution .  Control subjects ( CT ) received morphine 0.1 mg/kg IV and had saline added to their axillary block solution . All axillary blocks were performed using 0.55 ml/kg of 1.5 % lidocaine with epinephrine 1:200,000 . MEASUREMENTS AND MAIN RESULTS During the first 24 hours after surgery , visual analog scale ( VAS ) scores , supplementary analgesic ( oxycodone 5 mg with acetaminophen 500 mg ) use , and complications were recorded . Both groups had similar VAS scores throughout the study . In the 24-hour postoperative study period , AX patients required approximately half as many doses ( median , 2 doses ; range , 0 to 7 doses of supplemental analgesic as CT patients ( median , 4 doses ; range , 0 to 12 doses ) . There were no major complications in either group . CONCLUSIONS The addition of morphine 0.1 mg/kg to the local anesthetic axillary block solution provided improved postoperative analgesia without an increased frequency of side effects or major complications We have reported recently that continuous administration of butorphanol into the brachial plexus sheath provided analgesia of a quality superior to that of continuous i.v . administration . In the present study , we have compared postoperative pain relief produced by continuous infusion of one of three types of solution into the axillary sheath : opioid alone , local anaesthetic alone or a mixture of local anaesthetic and opioid . In patients undergoing upper extremity surgery with continuous axillary brachial plexus block , we injected one of the three solutions into the axillary neurovascular sheath : butorphanol 2 mg ( group B ) , 0.5 % mepivacaine alone ( group M ) and 0.5 % mepivacaine-butorphanol ( group MB ) ; the volume of each solution was 50 ml , administered at a rate of 50 ml per 24 h. At 3 h after operation , visual analogue scale ( VAS ) scores were significantly higher in group M than in group MB ( P < 0.01 ) , and higher in group B than in group MB ( P < 0.05 ) Background : Although addition of clonidine to local anesthetics can prolong pain relief after peripheral nerve block , a dose‐range effect has not been determined . Methods : Fifty‐six out patients undergoing carpal tunnel release were r and omly assigned to receive in a double‐blind fashion 45 ml of a mixture containing either 400 mg lidocaine plus saline or 400 mg lidocaine plus 30 , 90 or 300 micro gram clonidine for axillary nerve block . In each group ( n = 14 ) , blocks were evaluated at regular time intervals to determine sensory and motor functions in the five nerve regions of the h and and forearm . Also , adequacy of the block for surgery , postoperative pain intensity , and side effects were evaluated . Results : Compared with saline , each dose of clonidine reduced the onset time of sensory block and extended the field of adequate anesthesia . Ten minutes after injection , 30 micro gram clonidine was more effective than 90 micro gram clonidine in producing sensory blockade . Sedation occurred with clonidine 30 and 300 micro gram . Clonidine reduced the use of supplementary intravenous anesthetic agents for surgery and produced dose‐dependent prolongation of analgesia , reaching a mean 770 min ( range , 190–1440 min ) for the largest dose . Clonidine also produced a dose‐dependent decrease in systolic arterial pressure of up to ‐22.5 % ( range , ‐6.0–29.9 % ) of baseline . With clonidine , 300 micro gram , three patients had mean arterial pressure of < 55 mmHg ; four patients had episodes of arterial oxyhemoglobin saturation of < 90 % , and two others were not discharged because of hypotension . Conclusion : This study suggests that a small dose of clonidine enhances the quality of the peripheral blocks from lidocaine and limits the classical alpha2 ‐agonist side effects to sedation The effectiveness of buprenorphine and morphine , administered into the brachial plexus sheath , was evaluated in 40 patients , aged 18 - 90 years . All patients received 40 ml of 0.5 % bupivacaine , injected into the brachial plexus sheath using the supraclavicular technique . In addition , the 20 patients in Group I received morphine hydrochloride ( 50 μg/kg ) , while the 20 patients in Group II received buprenorphine hydrochloride ( 3 μg/kg ) . Using a three-point pain scale , the quality of analgesia was evaluated every hour for six hours , every two hours for the next six hours , and then at 12 , 24 , 36 and 48 hours . A significant difference in the quality of analgesia was found ; and was consistently superior with buprenorphine as compared with morphine . The duration of analgesia was nearly twice as long in the buprenorphine group as in the morphine group ( 35.05 ± 1.95 hour versus 18.25 ± 1.15 hour ) . We conclude that buprenorphine injection into the brachial plexus sheath is an efficient way to assure control of postoperative pain after upper limb surgery We have studied 40 patients undergoing elective shoulder surgery for chronically painful conditions . Patients were allocated r and omly to two groups and received interscalene brachial plexus block with 0.5 % bupivacaine and adrenaline 1/200,000 40 ml either alone or with the addition of morphine 5 mg . All patients also received a general anaesthetic . The quality of the block , analgesic requirements and any complications or side effects were noted in the intraoperative period and during the 48 h after operation . No significant difference was seen in quality of analgesia or patient satisfaction between the two groups Peripheral administration of opioids has been suggested as a means of improving regional block . We studied 60 patients receiving axillary brachial plexus anaesthesia , allocated r and omly to receive either normal saline 10 ml or normal saline 10 ml with alfentanil 10 micrograms/kg body weight through an axillary cannula . All patients received 1.5 % lignocaine at a dose of 7 mg/kg body weight with adrenaline 1 in 200,000 . The incidence of satisfactory block was similar in both groups . Although the percentage of patients with complete anaesthesia in the median nerve distribution was greater in the alfentanil group , there was no significant difference in any other distribution . The time to return of sensation and motor function was prolonged significantly in the alfentanil group ( P < 0.05 ) . After return of normal sensation , there was no significant difference between groups in postoperative analgesia . In a second part of the study , there was no significant increase in plasma concentrations of alfentanil in 10 patients given lignocaine and alfentanil , as outlined above . These observations suggest that alfentanil may have a peripheral local anaesthetic action The effects of clonidine and epinephrine , administered into the brachial plexus sheath , were evaluated in 60 patients who underwent surgery of the upper limb . All patients received 40 to 50 ml of 0.25 % bupivacaine , injected into the brachial plexus sheath , using the supraclavicular technique . The patients were r and omly allocated to two groups so that 30 patients received 150 μg clonidine hydrochloride ( Group I ) , and 30 received 200 μg epinephrine ( Group II ) . The quality and the duration of analgesia were assessed as well as , the possible side-effects . The block produced with the addition of clonidine was longer ( 994.2±34.2 vs 728.3±35.8 min ) and superior to that with epinephrine ( P<0.001 ) . No major side-effects were recorded . We conclude that the injection of clonidine into the brachial plexus sheath is an attractive alternative to epinephrine to prolong the duration of analgesia following upper limb surgery under conduction anaesthesia . RésuméLes effets de l’addition d’agents agonistes alpha-adrénergiques à la bupivacaïne lors de blocs du plexus brachial ont été évalués chez soixante patients ayant une intervention chirurgicale sur le membre supérieur . L’ensemble des patients a reçu 40 à 50 ml de bupivacaïne à 0.25 % pour réaliser un bloc du plexus brachial par voie sus-claviculaire . Les patients du groupe I ( n=30 ) recevaient par la même voie 150 μg de clonidine , ceux du groupe II ( n=30 ) 200 μg d ’ adrénaline . La durée et la qualité de l’analgésie sont ensuite étudiées ainsi que les éventuels effets adverses . Une différence statistiquement significative a été retrouvée en ce qui concerne la durée d’analgésie qui était supérieure dans le groupe clonidine ( 994,2±34,2 min vs 728,3 ±35,8 min ; P<0.001 ) . Aucun effet adverse majeur n’est retrouvé . Les auteurs concluent à l’intérêt particulier de la clonidine pour prolonger la durée d ’ analgésie après chirurgie du membre supérieur réalisée sous anesthésie régionale The admixture of clonidine or epinephrine to lidocaine for brachial plexus block was studied with regard to duration of block , postoperative analgesia , and plasma concentrations of lidocaine .  Thirty-three patients of ASA physical status I and II received an admixture of either clonidine ( 150 micrograms ; n = 15 ) or epinephrine ( 200 micrograms ; n = 18 ) to 40 mL of 1 % lidocaine in a r and omized , double-blind fashion . Bone surgery predominated in those patients receiving clonidine and soft-tissue surgery in those receiving epinephrine ( P less than 0.05 ) . Onset and duration of block were not different between the groups . With the admixture of clonidine , fewer patients were completely pain free for greater than 12 h ( 13.3 % ) and pain scores ( visual analogue scale 0 - 10 ) were higher 6 h after the block ( median 4 ; range 0 - 6 ) than with epinephrine ( 61.1 % ; median 2 ; range 0 - 7 , respectively ; P less than 0.05 ) . In patients who had received clonidine , peak plasma concentrations of lidocaine  were higher ( 10.29 + /- 2.96 mumol/L ) and occurred earlier ( 23.7 + /- 9.3 min ; mean + /- SD ) than in those treated with epinephrine ( 6.9 + /- 1.71 mumol/L ; 72.5 + /- 56.2 min ; P less than 0.05 ) . This indicates the absence of a local vasoconstrictor effect of clonidine and implies a reduced margin of safety with regard to local anesthetic 
    Output:
    
Clonidine appears to have significant analgesic benefit and to cause minimal adverse effects when used in doses up to 150 microg .