COMPARISON OF BUPIVACAINE HYDROCHLORIDE AND CARBONATED BUPIVACAINE IN BRACHIAL PLEXUS BLOCK BY THE INTERSCALENE TECHNIQUE

A double-blind comparison of carbonated bupivacaine and bupivacainehydrochloride in brachial plexus anaesthesia produced by theinterscalene technique was made in 20 patients. A more widespreadand more intense nerve block was demonstrated using the carbonatedsolution.     

PLASMA CONCENTRATIONS OF BUPIVACAINE AND TWO OF ITS METABOLITES DURING CONTINUOUS INTERSCALENE BRACHIAL PLEXUS BLOCK

An interscalene brachial plexus block was performed via a catheterwith 20–28 ml of 0.75% bupivacaine plus adrenaline forsurgery of the shoulder region in 12 patients. Constant infusionof 0.25% bupivacaine 0.25 mg kg^–1 h^–1 was continuedfor 24 h. During surgery light general anaesthesia, withoutanalgesics, was maintained. Plasma concentrations of total andunbound (free fraction) bupivacaine, desbutylbupivacaine (DBB),4-hydroxybupivacaine (4-OHB) and alpha₁-acid glycoprotein (AAG)were measured at predetermined intervals during the continuousblock. The greatest mean plasma concentrations of bupivacainewere measured at 30 min (1.63 (SD 0.55) µg ml^–1)and 60 min (1.38 (0.48) µg ml^–1). There was a smallbut statistically significant increase in the plasma concentrationof bupivacaine between 12 and 24 h of infusion. The mean unboundconcentration of bupivacaine in plasma decreased from 0.044(0.015) µg ml^–1 (3.6 (1.1)% of total bupivacaineconcentration) at 3 h to 0.023 (0.011) µg ml^–1 (2.1(1.0)%) at 24 h. The AAG concentration in plasma increased by38% in 24 h. The metabolites DBB and 4-OHB were detectable inplasma from 30 min, with a gradual increase during infusion.At 24 h the mean concentrations of DBB and 4-OHB were 0.33 (0.22)µg ml^–1 and 0. 13 (0.04) µg ml^–1, respectively.There were no toxic reactions during the blocks.     

PROLONGED BRACHIAL PLEXUS BLOCK WITH 0.42% BUPIVACAINE

A 55-yr-old man received a left supraclavicular brachial plexusblock with 0.42% bupivacaine; he had profound motor and sensoryblock 26 h after injection; complete recovery occurred at 40h.     

INVERSE CORRELATION BETWEEN THE PEAK VENOUS SERUM CONCENTRATION OF BUPIVACAINE AND THE WEIGHT OF THE PATIENT DURING INTERSCALENE BRACHIAL PLEXUS BLOCK

Thirty-five adult pàtients with rheumatoid arthritisreceived for 36 interscalene brachial plexus blocks a standarddose of bupivacaine 200 mg, regardless of the weight (range39.2–702.5kg) of the patient. The peak venous serum concentrations(Cmax) of bupivacaine, measured by HPLC. were in the range 0.82–4.30mg litre^–1; there were no signs of toxicity. There wasa very significant inverse correlation between the Cmax of bupivacaineand the weight of the patient (r = –0.5922; t = –4.285;P = 0.0001, Pearson's test). In spite of the correlation, only35.1% of the total variance could be explained by regression.Thus weight had little influence on Cmax under interscalenebrachial plexus block. ^*Present address, for correspondence: Department of Anaesthesiology,Turku City Hospital, Kunnallissairaalantie 20, SF-20700 Turku,Finland.     

PLASMA CONCENTRATIONS OF LOCAL ANAESTHETICS AFTER INTERSCALENE BRACHIAL PLEXUS BLOCK

Plasma concentrations of local anaesthetic agents have beenmeasured after 40 interscalene brachial plexus blocks in 39patients, using lignocaine, prilocaine, bupivacaine and etidocaine.Lignocaine produced greater concentrations than prilocaine,and bupivacaine greater concentrations than etidocaine. Theaddition of adrenaline resulted in much lower concentrationsin the case of all four agents.     

EXTRADURAL DIAMORPHINE WITH ADRENALINE IN LABOUR: COMPARISON WITH DIAMORPHINE AND BUPIVACAINE

In a randomized double-blind study of 51 primigravida, we haveexamined the relative efficacies of bupivacaine, diamorphineor diamorphine with adrenaline given by the extradural routefor relief of pain during labour. Group 1 (n = 18) receiveddiamorphine 5 mg in 0.9% sodium chloride 8 ml; group 2 (n =19) received diamorphine 5 mg in 0.9% sodium chloride 8 ml with1: 200 000 adrenaline; group 3 (n = 14) received 0.375% bupivacaine8 ml. All patients received 0.375% bupivacaine 8 ml as a supplementafter the initial analgesia had subsided. Patients in all groupshad satisfactory and comparable analgesia 20 min after the initialinjection. However, after 60 min and up to 8 h, analgesia wassuperior in group 2 as assessed by linear analogue pain scores,with statistical significance at 4, 6 and 8 h. Groups 1 and2 required bupivacaine supplements less frequently than group3 (P < 0.001). There were no serious adverse effects in anygroup, but pruritus was a feature in the diamorphine groups.Diamorphine 5 mg may be used as an alternative to bupivacaine0.375% 8 ml in the first stage of labour and provides a longerduration of action. The addition of adrenaline 1: 200 000 appearsto augment both the quality and duration of analgesia.     

EXTRADURAL ANALGESIA IN OBSTETRICS: A CONTROLLED TRIAL OF CARBONATED LIGNOCAINE AND BUPIVACAINE HYDROCHLORIDE WITH OR WITHOUT ADRENALINE

Four local anaesthetic solutions (2% carbonated lignocaine withor without adrenaline and 0.5% bupivacaine HCl with or withoutadrenaline) were used randomly for 335 continuous lumbar extra-duralblocks in labour. Carbonated lignocaine caused a more rapidonset of analgesia than bupivacaine HCl. The addition of adrenalinemade little difference to the onset times, prolonged markedlythe duration of analgesia with carbonated lignocaine and hadlittle effect on the duration of analgesia with bupivacaineHCl. Tachyphylaxis was a feature with carbonated lignocaineand adrenaline, but not with the other solutions. The incidenceof unblocked segments was 7–9% in the four groups. Theincidence of unilateral analgesia was 6% with plain lignocaineand 13% in the other groups! Complete pain relief occurred morefrequently with bupivacaine HCl than with carbonated lignocaineand the use of adrenaline had little effect on the degree ofanalgesia.     

PLASMA PRILOCAINE CONCENTRATIONS AFTER THREE TECHNIQUES OF BRACHIAL PLEXUS BLOCKADE

Brachial plexus blockade (n = 30: 10 axillary, 10 perivascularsubclavian, 10 interscalene) was performed on 28 patients, using35 ml of 1.5% prilocaine in plain solution. Plasma prilocaineconcentrations were measured at intervals over the following60 min. There was no significant difference in the prilocaineconcentrations between the three groups. One asymptomatic patientin the interscalene group had a peak prilocaine concentrationgreater than the accepted threshold for toxic symptoms.     

INSUFFICIENT VENOUS DRAINAGE FOLLOWING AXILLARY APPROACH TO BRACHIAL PLEXUS BLOCKADE

Progressive obstruction of an axillary vein following an axillaryapproach to brachial plexus blockade is described. At surgicalexploration, the axillary vein was narrowed with an aneurysmof its wall. It is likely that, during the performance of theblock, the needle penetrated the adventitia of the vein, causinga sub-adventitial haematoma and an aneurysm of the vein wall.Normal venous drainage was re-established surgically and thepatient recovered completely     

AN INFRARED THERMOGRAPHY STUDY ON THE DURATION OF INTERCOSTAL NERVE BLOCKS USING BUPIVACAINE WITH AND WITHOUT ADRENALINE

Because of a fairly wide range of duration of intercostal nerve blocks postoperatively in patients an objective method was used to study this problem. Infrared thermography was applied to study intercostal nerve blocks produced by bupivacaine 0.5% with and without adrenaline. Consistent results were obtained in volunteers when thermography and pin-prick methods were compared. Added adrenaline does not seem to prolong the intercostal nerve block.
When patients were studied only bupivacaine 0.5% with adrenaline was used. The range of duration was wide (7 to 20 hours), and the variation between pin-prick and thermography results less consistent.

ZUSAMMENFASSUNG

Wegen der ziemlich weitgestreuten Wirkungsdauer postoperativer Intercostalnervenblockaden wurde eine objektive Mediode zum Studium dieses Problems angewandt. Wir bedienten uns der Infrarot-Thermographie zur Untersuchung von Intercostalnervenblockaden durch Bupivacain 0,5%, mit und ohne Adrenalin. Beim Vergleich der Thermographic mit der Nadelstich-Testmediode an freiwilligen Versuchspersonen ergab sich gute Übereinstimmung. Adrenalinzusatz scheint die Nervbloskdauer nicht zu verlängern.
Bei den Untersuchungen an Patienten wurde nur 0,5%iges Bupivacain mit Adrenalin verwendet. Die Wirkungsdauer war weit gestreut (zwischen 7 und 20 Stunden), die Übereinstimmung zwischen Thermographic und Nadel-stichtest war weniger verlässlich.     

CLONIDINE COMBINED WITH SUFENTANIL AND BUPIVACAINE WITH ADRENALINE FOR OBSTETRIC ANALGESIA

Clonidine produces analgesia via a non-opioid mechanism andit may be used as an interesting adjuvant to local anaestheticsand opioids in obstetric analgesia. To examine the effects ofthe addition of clonidine to bolus injections of bupivacaine,adrenaline and sufentanil, we enrolled 50 women receiving extraduralanalgesia for vaginal delivery into a double-blind study. Theywere allocated randomly to two groups: group A received a 10-mlextradural solution of bupivacaine 12.5 mg combined with adrenaline25 µg and sufentanil 10 µg; group B received thesame solution with clonidine 30 µg Each patient was allowedtwo subsequent injections of the chosen solution. Subsequently,if still in the first stage of labour, analgesia was augmentedwith additional 10-ml injections of bupivacaine 12.5 mg withadrenaline 25 µg. without sufentanil or clonidine. Thelatter solution was used for perineal analgesia in group A;clonidine 30 µg was added in group B. During the firstand second stages of labour, there was no difference betweenthe two groups in duration of analgesia after the first injection(142 min in group A; 127 min in group B), number of injections(1.8 in group A; 1.9 in group B) and the total bupivacaine requirements(33.9mg in group A; 34 mg in group B). The quality of analgesiawas evaluated as very good in both groups (23/25 in group A;24/25 in group B). The degree of motor block or the frequencyof other side effects were not enhanced by clonidine. Analgesiawas greater for episiotomy in group B (15/20 in group A; 21/21in group B) (P < 0.05). Within the limits of this study,the total dose of extradural clonidine 90 µg appearedto be safe for the mother and the child. (Br. J. Anaesth. 1993;71: 657–660)     

COMPARISON OF BUPIVACAINE AND ETIDOCAINE IN EXTRADURAL BLOCKADE

In a randomized, double-blind study, 40 female patients underwentmajor gynaecological surgery with extradural anaesthesia providedby 0.75% bupivacaine, 0.75% bupivacaine with adrenaline 5µgml^–1,1.5%etidocaine or 1.5% etidocaine with adrenaline 5 µg ml^–1,20ml in each case. In all patients the resultant blockade wassuitable for intra-abdominal pelvic surgery. Mean maximum spreadof analgecia was around T3/4 with all four drugs. Onset of sensoryand motor block was more rapid following etidocaine than followingbupivacaine. The addition of adrenaline increased the speedof onset of sensory block. Patients receiving etidocaine hada denser motor blockade than those receiving bupivacaine, andthe addition of adrenaline led to an increase in the densityof the motor blockade. There were no differences in the durationsof motor blockade. Objective measurements of the duration ofsensory blockade showed that there were no differences betweenthe drugs and that the addition of adrenaline increased theduration of blockade. However, pain returned sooner followingetidocaine than bupivacaine, and the additive effect of adrenalinewas to increase this period of subjective analgesia.     

EFFECTS OF SPINAL BLOCKADE WITH BUPIVACAINE ON PARTURITION IN RATS

On the day of expected delivery, primigravid rats received 0.5%bupivacaine continuously through a chronically implanted intrathecalcannula to produce intense sensory and motor blockade belowthe T10 level. The mean duration of delivery was prolonged to3.1 h compared with 1.4 h in a control group without intrathecalblockade and a group which received an intrathecal infusionof Hartmann's solution. The mean percentages of live birthsper litter surviving the first 6 h was 94% in the control groupsand 42% in those receiving bupivacaine by intrathecal infusion.No increased perinatal mortality was observed in another controlgroup receiving an i.p. infusion of 0.5% bupivacaine in thesame dose as that given intrathecally. Two mother rats diedduring delivery under spinal blockade because of prolonged labour.It is concluded that, without obstetric intervention, intensesensory and motor blockade delayed parturition and increasedfetal mortality in the pregnant rats. ^* Present address: Department of Obstetrics and Gynaecology,University of Hong Kong, Hong Kong.     

EFFECT OF ADDITION OF HYALURONIDASE TO BUPIVACAINE DURING AXILLARY BRACHIAL PLEXUS BLOCK

We have studied in 22 patients the effect of adding hyaluronidaseto bupivacaine during axillary brachial plexus block (BPB) ina double-blind design. Patients received BPB using bupivacaine2 mg kg^–1 with adrenaline 1 in 200000, either with orwithout hyaluronidase 3000 iu, in a volume of 0.5 ml per 2.54cm of the patient's height. The use of hyaluronidase did notincrease the speed of onset of anaesthesia or reduce the incidenceof inadequate nerve block. Hyaluronidase produced a significantreduction in the duration of anaesthesia. Changes in grip strengthand skin temperature were useful in assessing the onset andprogress of BPB.     

EXTRADURAL PETHIDINE WITH AND WITHOUT ADRENALINE DURING LABOUR: WIDE VARIATION IN EFFECT

The pain-relieving effect of a single extradural dose of pethidine25mg with and without adrenaline waS studied in 20 healthy womenduring labour. The study was open regarding the effects of pethidinebut double-blind regarding the addition of adrenaline. In 14of 19 women good or excellent analgesia was achieved for a periodof 50–160 min. Pethidine with adrenaline 25 µg wasnot more effecnve than pethidine alone Eight of the 14 womenshowed signs of regional analgesia to pin-prick and temperaturediscrimination The patients had small (45-188 ng ml^–1)concentrations of pethidine in plasma In eight patients theplasma concentrations of pethidine were maintained for at least1.5 h. Extradural pethidine thus induces analgesia of shortand variable duration. Repeated doses may be needed, resultingin accumulation of the drug in plasma with the risk of respiratorydepression in mother or child.     

FENTANYL AND BUPIVACAINE MIXTURES FOR EXTRADURAL BLOCKADE

In a prospective double-blind study, single dose lumbar extraduralblockade was instituted in 80 healthy male patients undergoinglower abdominal surgery. Patients were assigned randomly toone of four groups. Each group received treatment with 0.5%bupivacaine 20 ml containing adrenaline 1:200 000. To this solutionwas added fentanyl 0, 50, 100 or 200 µg. The time to regressionof analgesic blockade was significantly prolonged (P < 0.05)only with mixtures containing fentanyl 200 µg; no effectwas demonstrated with lower doses of the opioid. However, thedegree of motor blockade was less intense and incomplete S1-blockade(root-jumping) was more frequent with mixtures containing increasingdoses of fentanyl. Patients treated with bupivacaine—fentanylmixtures shivered less than the control group and showed fewerinstances of acute hypotension. The side-effects observed wereminor.     

SUBARACHNOID BLOCKADE WITH BUPIVACAINE: A comparison with cinchocaine

Subarachnoid anaesthesia was induced in 40 patients with 0.5%bupivacaine 3 ml with no glucose, 5% glucose or 8% glucose,or with hyperbaric cinchocaine. The injections were made inthe lateral position and the patients turned supine immediately.The onset, extent and duration of sensory and motor blockade,the quality of anaesthesia, cardiovascular effects, and thefrequency of side-effects were studied. The hyperbaric solutionsproduced a greater cephalad spread (T6–T7) than the glucose-freesolution (T10–T11). Cinchocaine produced a longer durationof action at Tl0 and Tl2 than the hyperbaric bupivacaine solutions.No advantage was seen when 8% rather than 5% glucose was used.The glucose-free bupivacaine produced intense blockade of longduration and was suitable when a lower level of blockade wasadequate for the proposed surgery.     

EFFECTS OF EXTRADURAL BUPIVACAINE WITH ADRENALINE FOR CAESAREAN SECTION ON UTEROPLACENTAL AND FETAL CIRCULATION

We have studied the effects of an extradural block using bupivacainewith adrenaline 90–100 µg on blood flow in the maternaluterine and placental arcuate arteries and the fetal umbilical,renal and middle cerebral arteries, using a colour Doppler techniquein eight healthy parturients undergoing elective Caesarean section.Fetal myocardial function was investigated simultaneously byM-mode echocardiography. Maternal heart rate increased and diastolicarterial pressure decreased after extradural administrationof bupivacaine with adrenaline. The latter effect was relievedby increasing the infusion rate in every case and none of thepatients required vaso-pressors. There were no significant differencesin maternal or fetal blood velocity waveforms, and no significantchanges were found in any of the fetal myocardial measurementsrelative to control values. These observations suggest thatextradural anaesthesia using bupivacaine with adrenaline doesnot have an adverse effect on vascular resistance in the uteroplacentalor fetal circulations or on fetal myocardial function in normalpregnancy when bupivacaine-adrenaline is administered fractionallyand maternal hypotension is prevented by rapid crystalloid volumeloading.     

ADRENALINE, FENTANYL OR ADRENALINE AND FENTANYL AS ADJUNCTS TO BUPIVACAINE FOR EXTRADURAL ANAESTHESIA IN ELECTIVE CAESAREAN SECTION

We have compared the effects of extradural fentanyl and fentanylplus adrenaline with adrenaline alone as adjuncts to extraduralbupivacaine in patients undergoing elective Caesarean section.Forty-five patients were allocated randomly to receive 0.45%bupivacaine 20 ml with adrenaline 4.5 µg ml^–1, fentanyl4.5 µg ml^–1 or adrenaline plus fentanyl (4.5 µgml^–1 of each) as supplements. The main outcome measureswere time to bilateral analgesia of T6 or higher, need for intraoperativeanalgesic supplements, observer rating of intraoperative analgesiaand patient assessment of analgesia using a 10-cm visual analoguescale. The time to onset of analgesia to T6 was reduced insignificantlyby the fentanyl solutions compared with adrenaline only. Thequality of analgesia as assessed by the need for analgesic supplementswas superior for the patients given fentanyl. An observer ratingof pain and visual analogue pain scoring by the patient alsoindicated superior analgesia with fentanyl supplementation.Two patients experienced respiratory depression after extraduralfentanyl and were given naloxone. Two neonates were also givennaloxone. Close supervision is therefore recommended in theearly postoperative period when this technique is used.