SPINAL ANAESTHESIA WITH HYPERBARIC BUPIVACAINE: EFFECTS OF CONCENTRATION AND VOLUME ADMINISTERED

A double-blind study was earned out using hyperbaric solutionsof bupivacaine to compare the effects of varying the concentrationof bupivacaine and the volume of solution administered intrathecallyFifty-seven patients were studied. Ten patients received eachvolume of each concentration: 0.5% bupivacaine in 8% dextrose,2 ml, 3 ml or 4 ml and 0.75% bupivacaine in 8% dextrose, 1.3ml or 2 ml A further seven patients received 3 ml of the 0.75%solution Both solutions consistently produced good nerve blockade.With the 0.5% solution, increases in the volume administeredhad no effect on the spread of sensory loss, whereas with the0 75% solution, increasing the volume administered resultedin a significantly greater cephalad spread. The use of 3 mlof this solution was abandoned after seven patients had receivedit because of the excessive spread. With both solutions, increasingthe volume produced a longer duration of action. The use ofa 0 75% solution of hyperbaric bupivacaine for spinal anaesthesiadid not appear to confer any advantage over the 0.5% solution.     

EFFECT OF THE TRENDELENBERG POSITION ON SPINAL ANAESTHESIA WITH HYPERBARIC BUPIVACAINE

In a double-blind study, the effect of the Trendelenberg positionwas compared with the supine, in 20 patients following intrathecalinjection of 3 ml of 0.5% bupivacaine in 8% glucose. All patientshad blocks suitable for abdominal surgery Although the meanspread was greater in those patients tilted head-down, thiswas not statistically significant. The variation of the spreadaround the mean was greater in the head-down group, and blocksextended into the cervical region in two patients. There wereno differences in motor block, duration or cardiovascular changesbetween the groups. It is concluded that the Trendelenberg positionis not necessary to ensure spread of local anaesthetic solutioninto the mid-thoracic region for abdominal surgery.     

SPINAL ANALGESIA WITH HYPERBARIC BUPIVACAINE: EFFECTS OF VOLUME OF SOLUTION

The effects of 0.5% bupivacaine 1.5, 2 and 3ml in 8% glucosewere compared in a double-blind study involving 30 patientsundergoing spinal analgesia. The time to the onset of maximumsegmental spread of analgesia was approximately 15 min for allthree volumes. Cephalad spread of analgesia was related to thevolume used: 1 5 ml reached T10, 2 ml T8 and 3 ml T7. The durationof analgesia increased with increasing volume, 3 ml producinganalgesia in T8–T12 for 1.5–2 h, and in the lumbarregion for 2.5–3 h. Increasing the volume increased theextent of motor blockade and speeded up its onset. Significantdecreases in arterial pressure were observed in the 2- and 3-m]groups The changes in heart rate were moderate and not correlatedwith the amount of drug. Spinal headache occurred in two patients.     

SPINAL ANAESTHESIA WITH 0.5% BUPIVACAINE 3 ML: COMPARISON OF PLAIN AND HYPERBARIC SOLUTIONS ADMINISTERED TO SEATED PATIENTS

In a double-blind study, 0.5% bupivacaine 3 ml in plain (n=10)or hyperbaric (n=10) solution was injected intrathecally to20 patients who were in the sitting position, to produce spinalanaesthesia for transurethral resection of prostate. No statisticallysignificant differences were found in time to maximum cephaladspread of analgesia nor in the level reached. However, the plainsolution produced a smaller scatter around the mean level thanthe hyperbaric solution. The duration of analgesia was not significantlydifferent between two groups. There was no difference in theincidence of complete motor block, but a longer duration oflesser degrees of motor block was found with the plain solution(P<0.05). The plain solution produced a more predictablelevel of blockade.     

SPINAL ANALGESIA WITH HYPERBARIC BUPIVACAINE: INFLUENCE OF AGE

The effects of age were investigated on characteristics of spinalanalgesia with hyperbaric bupivacaine in 38 younger patients(<50yr: group I), and 48 older patients (>80 yr: groupII). Four millilitre of 0.375% bupivacaine in 2.5% dextrosewas injected via the L3–4 space in a lateral position,and the patients were immediately turned supine. In group II,the time to maximum spread was significantly shorter, and thesensory spinal blockade higher (one derma-tome) than in groupI. The mean sensory recovery of the two uppermost segments didnot differ between the two groups. The mean duration of analgesiaat the L2 level was increased by only 15min in the older group.Complete motor blockade of the lower limbs developed most rapidlyin group II, while duration of all degrees of motor blockadedid not differ significantly with age. Because of great individualvariation, the clinical significance of such differences islimited. In the older group, there was a greater decrease insystolic arterial pressure from resting values, despite rapidinfusion of lactated Ringer's solution.     

PREDICTION OF THE SPREAD OF REPEATED SPINAL ANAESTHESIA WITH BUPIVACAINE

We have studied in 56 patients the predictability of spreadof repeated spinal anaesthesia in the same patient on the basisof a previous block. With plain 0.5% bupivacaine, predictionof the second block was accurate. A significantly higher orlower spread of analgesia than in the previous block was achievedwhen plain 0.5% bupivacaine was administered using a modifiedtechnique7mdash;sitting position or lower interspace, respectively.When hyperbaric 0.5% bupivacaine was injected instead of plainsolution for the second block using a similar technique, nobaricity-related correlation was found between the first andsecond blocks. Change in technique did not reduce interindividualvariation in the spread of analgesia. We conclude that individualanatomical properties may play a more important role than, forexample, baricity in subarachnoid distribution of a local anaestheticsolution.     

SPINAL ANAESTHESIA WITH GLUCOSE-FREE 0.5% BUPIVACAINE: EFFECTS OF DIFFERENT VOLUMES

The effects of different volumes (1.5, 2, 3, and 4ml) of glucose-free0.5% bupivacaine used for spinal anaesthesia were compared in40 patients scheduled for urological surgery. The blocks wereperformed with the patients in the sitting position. The timeto maximum cephalad spread of analgesia varied between 13 and18.5 min. A significant difference was found in cephalad spreadbetween the 1.5-and 2-ml groups and the 3-and 4-ml groups. Theduration of analgesia increased, the time to complete motorblockade of the lower limbs decreased and the frequency of completemotor blockade increased with increasing volume. Spinal anaesthesiawith 3–4ml of glucose-free 0.5% bupivacaine proved satisfactoryfor transurethral resection of the prostate.     

SPINAL ANAESTHESIA WITH HYPERBARIC BUPIVACAINE: Effects of Age on Neural Blockade and Pharmacokinetics

Effects of ageing were studied on the neural blockade and thepharmacokinetics after subarachnoid administration of 0.5% bupi-vacaine3 ml in 8% glucose in two groups of 15 male patients, between20 and 55 yr and older than 55 yr, respectively. The blockadewas performed with the patient in the sitting position. Twominutes after the injection the patient was placed in the supineposition. The time to maximum cephalad spread and the upperlevel of analgesia increased with advancing age, whereas thetime to onset of motor blockade decreased with advancing age.Effects of age on the total duration of analgesia and motorblockade could not be demonstrated. Age had no effect on thepeak plasma concentration of bupivacaine. The time to peak concentrationand the terminal half-life increased, whereas the total plasmaclearance decreased with advancing age.     

CARDIORESPIRATORY EFFECTS OF THE SITTING POSITION IN NEUROSURGERY

The cardiorespiratory effects of raising patients from the supineto the sitting position for neurosurgery were investigated.The change caused marked decreases in cardiac index, strokevolume, Pa_O2 and Qs/Qt, with a significant increase in (PA_O2— Pa_O2) and total peripheral resistance. It is concludedthat patients who maintain normotension in the sitting positiondo not necessarily have an adequate circulatory status.     

EFFECT OF BARICITY ON SPINAL ANAESTHESIA WITH BUPIVACAINE

In a double-blind study of spinal anaesthesia with 0.5% bupivacaine3 ml with no glucose, 5% glucose or 8% glucose all three solutionsgave consistently good nerve blocks. The hyperbaric solutions(5% and 8% glucose) produced a greater cephalad spread and weresuitable for lower abdominal surgery, whereas the plain solution(no glucose) seldom affected the thoracic nerves. Cardiovascularchanges were more marked with the hyperbaric solutions but onlynecessitated treatment on two occasions. The duration of blockwas not affected by baricity and was in the range 140–160min.     

SUBARACHNOID ANAESTHESIA: COMPARISON OF HYPERBARIC SOLUTIONS OF BUPIVACAINE AND AMETHOCAINE

Hyperbaric solutions of 0.5% bupivacaine and 0.5% amethocaine(2 and 3 ml) were compared in a double-blind study of 40 patientsreceiving subarachnoid anaesthesia for urological surgery. Thedrugs produced similar and satisfactory analgesia in the testedconcentrations and volumes. Motor blockade was more profoundand longer lasting with amethocaine.     

EFFECTS OF POSTURE ON THE SPREAD OF SPINAL ANAESTHESIA WITH ISOBARIC 0.75% OR 0.5% BUPIVACAINE

In a double-blind study the effects of posture on the the spreadof 3 ml of isobanc bupivacaine 5 and 7 Smgml^–1 were comparedafter intrathecal injection in 40 patients undergoing orthopaedicsurgery. Three milhhtre of isobanc bupivacaine 7 5 mgml^–1administered with the patient in a sitting position during andfor 2.5 mm after injection produced the highest spread of analgesia(T4) Horizontal posture, and the smaller dose in both positions,resulted in spread of analgesia to T7-8. Motor block in thelegs was good in all cases. Horizontal posture at the time ofinjection resulted in the longest mean duration of analgesiaand motor block, although there was no statistically significantdifference in mean rimes between the groups The longest meanduration of pin-prick analgesia (329 ± 23 min) was inthe patients injected in the horizontal posture with bupivacaine7.5 mgml^–1. The course of anaesthesia and recovery wereuneventful in all patients.     

DISCREPANCY BETWEEN THE DEVELOPMENT OF TOLERANCE TO BUPIVACAINE IN EXTRADURAL AND SPINAL ANAESTHESIA IN RABBITS

We gave equal groups of rabbits seven extradural (500 µgkg^–1 or intrathecal (250 µg kg^–1 injectionsof bupivacaine, at 24-h intervals. A decrease in the durationof motor block was observed after the extradural injections.The intrathecal injections exerted a reproducible effect. Anadditional regimen was tested in which five doses of bupivacaine125 µg kg^–1 were administered intrathecally aftera loading dose of 250 µg kg^–1 when the animals showedpartial recovery from the previous dose; there was no decreasein the effect. The absence of tolerance to intrathecal bupivacaineimplies that tachyphylaxis to extradural local anaestheticsresults from a decrease in availability of the drug to the neuraltarget, rather than a diminution in effect at the site of action.(Br. J. Anaesth. 1993; 71: 450–452) ^*NIH, Hypertension-Endocrine Branch, Building 10, Room 8C103,Bethesda, MD 20892 U.S.A. Department of Anesthesiology, NYU Med Center, 550 1st Avenue,New York, NY 10016 U.S.A.     

EFFECTS OF POSTURE AND BARICITY ON SPINAL ANAESTHESIA WITH 0.5% BUPIVACAINE 5 ML: A Double-Blind Study

In four groups of 10 patients, 0.5% bupivacaine 5 ml was usedin spinal anaesthesia for gynaecological surgery. Group 1 receivedplain solution in the sitting position, group 2 plain solutionin the lateral position, group 3 hyperbaric solution in thesitting position and group 4 hyperbaric solution in the lateralposition. All patients were returned to the horizontal supineposition, the sitting subjects 2min after, and the lateral subjectsimmediately after, spinal injection. In each group the meanheight of block was to the mid-thoracic segments, but therewas no significant difference between the groups. There was,however, considerable scatter within each group. Posture hadsome effect on the speed of onset of the analgesia, but no significanteffect on the final outcome. The use of 0.5% bupivacaine asa test dose in extradural blockade is discussed.     

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 LATE POSTURE CHANGE ON THE LEVEL OF SPINAL ANAESTHESIA WITH PLAIN BUPIVACAINE

We studied 40 patients, 18–60 yr, undergoing orthopaedicsurgery of the lower limb under spinal anaesthesia. A midilnelumbar puncture was performed in the L3–4 interspace usinga 27-gaugeneedle with the patient in the lateral horizontalposition. Plain bupivacaine 3 ml at room temperature was injected.The cephalad level of an algesia was assessed by pinprick 60min after injection of local anaesthetic, at the end of surgeryand again after the patient was moved into bed. All patientshad a segmental level of the block of L1-T5 at the beginningof the study. The upper half of the patient's body was thentilted to a 30° head-up position. Segmental spread was subsequentlyassessed by pinprick at 5-min intervals for 30 min. In six ofthe 40 patients (15%), increased cephalad spread of spinal analgesiaoccurred. The mean time from induction of spinal anaesthesiawas shorter in these six patients (mean 92 min, range 80–115min) than in the patients whose block did not change or wasdecreasing during the 30-min test (mean 119 mm, range 83–210min) (P <0.05). We conclude that the patient should remainin the supine horizontal position until recovery from the spinalblock. (Br. J. Anaesth. 1993; 71: 807–809)     

SPINAL ANAESTHESIA WITH 0.75% BUPIVACAINE AND 0.5% AMETHOCAINE IN 5% GLUCOSE

Three millititre of 0.75% plain bupivacaine and 0.5% amethocaine3 ml in 5% glucose were used for spinal anaesthesia and comparedin a double-blind study of 20 patients undergoing urologicalsurgery. The onset time to maximum cephalad spread of sensoryanalgesia was approximately 45 min for bupivacaine and approximately30 min in the amethocaine group (ns). The mean maximum spreadof sensory analgesia was similar for both agents: T6-7 180 minafter injection, although the cephalad spread of sensory analgesiawith bupivacaine persisted for longer at a significantly higherlevel than that of amethocaine. Duration of sensory analgesiawas significantly longer in the bupivacaine group from S3 toS5 and from T12 to L2 levels. Onset time to complete motor blockadeof the lower limbs was similar for both agents. Nine of 10 bupivacainepatients and seven of the 10 patients receiving amethocainehad complete motor blockade of the lower limbs. Duration ofmotor blockade was significantly longer for all degrees in thebupivacaine group.     

RADIOLOGICAL EXAMINATION OF THE INTRATHECAL POSITION OF MICROCATHETERS IN CONTINUOUS SPINAL ANAESTHESIA

There have been few studies of the intrathecal position of spinalcatheters in continuous spinal anaesthesia. This prospectivestudy was designed to examine radiologically the intrathecalposition of 28-gauge spinal catheters. We studied the entryinto the subarachnoid space and the intrathecal position of68 spinal catheters. In 50%, the catheters passed in a cranialdirection, in 34% the catheters remained at the level of thepuncture site and in 16% the catheters were directed caudally.The intrathecal position of the catheters did not depend onthe level of the lumbar puncture (P = 0.6246), but was dependenton the position of the patient during insertion of the catheter(P = 0 0093), and on the depth of insertion (P = 0.0099). Ourstudy sug gests that patients should be in a sitting positionduring insertion of a subarachnoid microcatheter and that thedepth of insertion should not exceed 4cm. (Br. J. Anaesth. 1993;71: 803–806)     

EFFECT OF INJECTED VOLUME AND SPEED OF INJECTION ON THE SPREAD OF SPINAL ANAESTHESIA WITH ISOBARIC AMETHOCAINE

Amethocaine 10 mg in isobaric solution was injected intrathecallyin 40 patients. Three volumes (1, 2 and 4 ml) of injection andtwo rates of injection (1 ml per 5 s and 1 ml per 10 s) werestudied. Small volumes (1 and 2 ml) of the more concentratedsolutions (1 % and 0.5%) produced predictable blockade withspread restricted to the lower thoracic segments. Increasingthe volume had little effect on the mean height of spinal blockade,but blockade was less predictable. Slowing the speed of injectionof the largest volume (4 ml) partly counteracted this effect.