UTEROPLACENTAL AND FETAL CIRCULATION DURING EXTRADURAL BUPIVACAINE-ADRENALINE AND BUPIVACAINE FOR CAESAREAN SECTION IN HYPERTENSIVE PREGNANCIES WITH CHRONIC FETAL ASPHYXIA

We have studied the effects of an extradural block during Caesareansection using either bupivacaine plain or with adrenaline 85–100µg on blood velocity waveforms of maternal uterine andplacental arcuate arteries and fetal umbilical, renal and middlecerebral arteries, in 20 hypertensive parturients with chronicfetal asphyxia. Fetal myocardial function was investigated atthe same time by M-mode echocardiography. Extradural anaesthesiaresulted in a significant decrease in maternal mean systolicand diastolic arterial pressures in both groups, but this wasmore marked after plain bupivacaine. There were no significantdifferences in any of the Doppler recordings relative to baselinevalues after plain bupivacaine, but after bupivacaine with adrenalinethere were significantly increased blood flow velocity indicesfor the maternal uterine and placental arcuate arteries andsignificantly decreased indices in the fetal renal and middlecerebral arteries. Neonatal outcome as evaluated by Apgar scoresand acid-base values in the umbilical cord were similar in thetwo groups. The results suggest that adrenaline added to thesolution of bupivacaine increased vascular resistance in theuteroplacental circulation, indicating impaired blood flow.     

EFFECT OF ADRENALINE ON EXTRADURAL ANAESTHESIA AND PLASMA BUPIVACAINE CONCENTRATIONS DURING CAESAREAN SECTION

The effect of adrenaline on the efficacy of extradural blockand plasma bupivacaine concentrations was investigated in womenundergoing elective (n = 40) and emergency (n = 40) Caesareansection. Patients were randomly allocated within these two groupsto receive 0.5% bupivacaine 20 ml either plain or with adrenaline1 in 200000, as a single fractionated extradural injection.The elective plain group needed significantly more supplementaryanalgesia compared with the other three groups (P <0.05).In the elective group, plasma bupivacaine concentrations weresignificantly lower in the subgroup receiving extradural adrenalinethan in the plain subgroup. This effect was not observed whencomparing only those who received bupivacaine 100 mg. In theemergency group, there were no significant differences in plasmabupivacaine concentrations between the plain and adrenalinesubgroups. Maximum plasma concentrations correlated significantly(P < 0.0001) with dose of bupivacaine (mg kg^–1). Itis concluded that extradural adrenaline does not usefully reducesystemic absorption of 0.5% bupivacaine, but may improve itsefficacy in extradural anaesthesia for elective Caesarean section.     

EFFECT OF EXTRADURAL ANALGESIA USING BUPIVACAINE AND 2-CHLOROPROCAINE ON INTERVILLOUS BLOOD FLOW DURING NORMAL LABOUR

The effect of lumbar extradural analgmig on intervillous bloodflow (IBF) during labour was studied in 26 healthy parturientsusing an i. v. bolus injection of xenon-133. There was a 19%decrease (n.s.) in mean IBF in six parturients (non-extraduralcontrol group). Mean IBF increased by 37.5% when 0.25% bupivacaine10 ml was used and by 35.2% when 2% 2-chloroprocaine 10 ml wasused (n.s.). When the two extradural groups were combined, themean difference between IBFi and IBF2 was 45± 112 mlmin dl^–1. This increase is statistically significant (P<0.05). The improvement in IBF after extradural block was consideredto be a result of the decreased uterine vascular resistance,as no significant changes were observed in arterial pressure,utenne activity or uterine tone.     

Double-blind comparison of extradural block with three bupivacaine- ketamine mixtures in knee arthroplasty

We have compared 0.5% bupivacaine 75 mg (group A; n = 15) with three 0.5% bupivacaine 75 mg-ketamine mixtures for extradural block in 59 ASA I-III patients undergoing total knee replacement in a randomized, double-blind study. The following doses of preservative-free 1% ketamine were used: 0.3 mg kg-1 (group B: n = 14); 0.5 mg kg-1 (group C: n = 5); and 0.67 mg kg-1 (group D: n = 15). Level of sensory block, degree of motor weakness and sedation scores were recorded before and after operation. Duration of postoperative analgesia was also noted. There was no difference between groups in median maximum level of sensory block (group A: T4 (range T10-T2); group B: T4 (T10-T2); group C: T4 (T8-T2); and group D: T3 (T8-C3)) or in the degree of motor block. Thirty-three of the 44 patients who received ketamine showed signs of systemic absorption (blurred vision, sedation) within 10 min of injection. There was no significant difference between groups in median duration of analgesia (group A: 240 (range 115-340) min; group B: 198 (97-460) min; group C: 150 (122-448) min; and group D: 210 (130- 390) min). No patient suffered any adverse psychomimetic effects. We conclude that at the doses used, addition of ketamine to extradural bupivacaine did not improve extradural block in adult patients undergoing total knee replacement.      

Effect of epidural epinephrine infusion with bupivacaine on labor pain and mother-fetus outcome in humans

BACKGROUND AND OBJECTIVES: Epinephrine is used with local anesthetics to prolong the duration of epidural analgesia and decrease the peak plasma concentrations of local anesthetics. In the practice of obstetric anesthesia, the utero-placental and fetal effects of epinephrine are controversial issues. We designed a prospective, randomized, and double-blind study to examine the effects of epinephrine infusion on the quality of analgesia and uterine or umbilical blood flows with Doppler ultrasound, as well as the duration of the first or the second stage of labor, and fetal outcome. METHODS: Twenty-eight parturients received continuous epidural bupivacaine 0.25% (4 mL/h) combined either with epinephrine (20 microg/h) (n = 13) or without epinephrine (n = 15) for analgesia during labor. If patients requested additional analgesia, an additional bolus of 1% or 1.5% lidocaine (6 to 10 mL) was administered. RESULTS: The total amount of additional lidocaine was greater in the plain bupivacaine group (130 [0, 280] mg; median [25th, 75th percentile] with P < .05) than in the epinephrine group (0 [0, 60] mg). Epinephrine infusion did not alter the resistance of the uterine and umbilical arteries as measured by resistance index. The duration of the first or second stages of labor did not significantly differ in the 2 groups. Epinephrine infusion did not change the fetal heart rate or the blood gas data in the umbilical artery. CONCLUSIONS: A low-dose epidural infusion of epinephrine decreased anesthetic requirements.     

Ropivacaine, 0.1%, plus sufentanil, 0.5 microg/ml, versus bupivacaine, 0.1%, plus sufentanil, 0.5 microg/ml, using patient-controlled epidural analgesia for labor: a double-blind comparison

BACKGROUND: This study compared the administration of 0.1% ropivacaine and 0.5 microg/ml sufentanil with that of 0.1% bupivacaine and 0.5 microg/ml sufentanil via patient-controlled epidural analgesia route during labor. METHODS: Two hundred healthy pregnant women at term with a single fetus with a vertex fetal presentation were randomized in a double-blind fashion to receive either 0.1% ropivacaine and 0.5 microg/ml sufentanil or 0.1% bupivacaine and 0.5 microg/ml sufentanil using a patient-controlled epidural analgesia pump (5-ml bolus dose, 10-min locked-out period, no basal infusion). Pain score on a visual analog scale, Bromage score (0-3), level of sensory block, patient-controlled epidural analgesia ratio, drug use, supplemental boluses, and side effects were recorded at 30 min and then hourly. Mode of delivery, duration of first and second stages of labor, umbilical cord pH, Apgar scores of the newborn, and a measure of maternal satisfaction were recorded after delivery. RESULTS: No differences were seen between the two groups for pain scores on a visual analog scale during labor, volume of anesthetic solution used, mode of delivery, or side effects. Motor block during the first stage of labor was significantly less in the ropivacaine group than in the bupivacaine group (no motor block in 97.8 of patients vs. 88.3%, respectively; P < 0.01). Duration of the second stage of labor was shorter in the ropivacaine group (1.3 +/- 1.0 vs. 1.5 +/- 1.2 h [mean +/- SD]; P < 0.05). Maternal satisfaction was greater in the bupivacaine group (91 +/- 13 mm for contraction, 89 +/- 19 mm for delivery on a visual scale: 0 = not satisfied at all, 100 = fully satisfied) than in the ropivacaine group (84 +/- 21 and 80 +/- 25 mm; P < 0.0001). Patients in the ropivacaine group requested more supplemental boluses to achieve analgesia during the second stage of labor than those in the bupivacaine group (29.7 vs. 19.8%, respectively, requested one or more supplemental boluses; P < 0.05). CONCLUSIONS: Delivered as patient-controlled epidural analgesia, 0.1% ropivacaine and 0.5 microg/ml sufentanil produce less motor block but are clinically less potent than 0.1% bupivacaine and 0.5 microg/ml sufentanil.     

Plasma bupivacaine levels associated with extradural anaesthesia for Caesarean section

Plasma bupivacaine levels were measured in 47 women undergoing extradural Caesarean delivery. They were divided into four groups according to the following dose regimens using 0.5% bupivacaine. Group A were given a bolus of 20 ml with increment after 20 minutes. Groups B and C were given 10 ml initially with further increments if required at 10 minutes (group B) and 20 minutes (group C); Group D consisted of patients who had an extradural block extended for emergency Caesarean delivery. In the elective groups the highest and most rapidly achieved values were associated with group A and the lowest levels found in group C. The highest levels of all were found in the emergency group. The investigation indicates that slow controlled induction of extradural anaesthesia for Caesarean section greatly reduces the risk of local anaesthetic toxicity.     

Ropivacaine, 0.1%, Plus Sufentanil, 0.5 μg/ml, versus Bupivacaine, 0.1%, Plus Sufentanil, 0.5 μg/ml, Using Patient-controlled Epidural Analgesia for Labor: A Double-blind Comparison

Background: This study compared the administration of 0.1% ropivacaine and 0.5 [mu]g/ml sufentanil with that of 0.1% bupivacaine and 0.5 [mu]g/ml sufentanil via patient-controlled epidural analgesia route during labor.

Methods: Two hundred healthy pregnant women at term with a single fetus with a vertex fetal presentation were randomized in a double-blind fashion to receive either 0.1% ropivacaine and 0.5 [mu]g/ml sufentanil or 0.1% bupivacaine and 0.5 [mu]g/ml sufentanil using a patient-controlled epidural analgesia pump (5-ml bolus dose, 10-min locked-out period, no basal infusion). Pain score on a visual analog scale, Bromage score (0-3), level of sensory block, patient-controlled epidural analgesia ratio, drug use, supplemental boluses, and side effects were recorded at 30 min and then hourly. Mode of delivery, duration of first and second stages of labor, umbilical cord pH, Apgar scores of the newborn, and a measure of maternal satisfaction were recorded after delivery.

Results: No differences were seen between the two groups for pain scores on a visual analog scale during labor, volume of anesthetic solution used, mode of delivery, or side effects. Motor block during the first stage of labor was significantly less in the ropivacaine group than in the bupivacaine group (no motor block in 97.8 of patients vs. 88.3%, respectively;P < 0.01). Duration of the second stage of labor was shorter in the ropivacaine group (1.3 +/- 1.0 vs. 1.5 +/- 1.2 h [mean +/- SD];P < 0.05). Maternal satisfaction was greater in the bupivacaine group (91 +/- 13 mm for contraction, 89 +/- 19 mm for delivery on a visual scale: 0 = not satisfied at all, 100 = fully satisfied) than in the ropivacaine group (84 +/- 21 and 80 +/- 25 mm;P < 0.0001). Patients in the ropivacaine group requested more supplemental boluses to achieve analgesia during the second stage of labor than those in the bupivacaine group (29.7 vs. 19.8%, respectively, requested one or more supplemental boluses;P < 0.05).     

PROTEIN METABOLISM AFTER ABDOMINAL SURGERY: EFFECT OF 24-H EXTRADURAL BLOCK WITH LOCAL ANAESTHETIC

We have studied the effect of intraoperative and postoperative(24 h) extradural block with local anaesthetic on whole bodyprotein turnover (stable isotope methodology) and urinary excretionof urea nitrogen, adrenaline, noradrenaline and cortisol ina group of well nourished elderly patients undergoing colorectalsurgery who received a constant nutritional intake before (7days) and after (4 days) surgery. One group (control, n = 8)received routine anaesthetic and surgical care. Patients inthe test group (extradural, n = 9) received extradural bupivacaine,and sensory block (T4-S5) was maintained during and after surgeryfor a period of 24 h. Whole body protein breakdown and aminoacidoxidation increased significantly after surgery in both groups(P < 0.05), but the increase in protein breakdown in theextradural group was significantly less than that in the controlgroup. Urinary excretion of urea nitrogen, adrenaline and noradrenalineincreased in the control group after surgery, whilst the increasein the extradural group was very small. In contrast, urinaryexcretion of cortisol increased significantly in both groupsafter surgery. We conclude that extradural block maintainedfor 24 h after surgery significantly minimized postoperativeprotein breakdown without compromising whole body protein synthesis.     

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.     

Extradural anaesthesia for Caesarean section: a double-blind comparison of 0.5% ropivacaine with 0.5% bupivacaine

Seventy-three parturients for elective Caesarean section wereallocated randomly to receive extradural block with 20 ml ofeither 0.5% ropivacaine or 0.5% bupivacaine. If the block didnot reach T6 within 30 mm, another 5 ml of solution was given.If needed, a further 5 ml was given 45 mm after the main dose.The mean total dose of bupivacaine was 23.1 ml (n = 35) andof ropivacaine 23.7 ml (n = 37). There was no significant differencebetween the groups in the profile of sensory block produced.There was no significant difference in the time of onset, orintensity of motor block between the groups but the durationof motor block was significantly shorter in the ropivacainegroup. There was no significant difference in neonatal outcome,as assessed by Apgar score, umbilical cord bloodgas tensionsat delivery or the neurological and adaptive capacity score2 and 24 h after delivery. (Br. J. Anaesth. 1995; 74: 512–516)     

UTEROPLACENTAL AND FETAL HAEMODYNAMICS DURING EXTRADURAL ANAESTHESIA FOR CAESAREAN SECTION

We have studied the effects of extradural anaesthesia with bupivacaine(plain) in eight healthy parturients undergoing elective Caesareansection, on blood flow in maternal uterine and placental arcuatearteries and in fetal umbilical, renal and middle cerebral arteries,using a colour Doppler technique. Simultaneously, fetal myocardialfunction was investigated by M-mode echocardiography. Maternaland fetal blood velocity waveform indices did not change significantly.We found no changes in fetal myocardial function with extraduralanaesthesia, except for an increase in the right ventricularinner end-diastolic dimensions. These results suggest that extraduralanaesthesia has no detrimental effects on uteroplacental andfetal circulations in the uncomplicated pregnancy when maternalhypotension is avoided with rapid prehydration.     

Epidural anesthesia with ropivacaine vs. bupivacaine in continuous perfusion for the treatment of labor pains

OBJECTIVE: To compare the analgesic efficacy and extent of motor block when 0.125% ropivacaine or 0.125% bupivacaine were given in continuous perfusion through an epidural catheter during labor. PATIENTS AND METHODS: We studied 60 ASA I-II women, each carrying a single fetus at full term and in spontaneous labor. The patients were distributed in 2 groups. Women in the ropivacaine group (R) (n = 30) received 8 mL of 0.2% ropivacaine for analgesic induction, followed by a continuous perfusion of 10 mL/h at 0.125%. The bupivacaine group (B) (n = 30) received bupivacaine at the same concentration and infusion rate. The objective of analgesia was to achieve a score less than 3 on a visual analog pain scale. If analgesia was inadequate, a 5 mL bolus of 0.2% ropivacaine or bupivacaine, depending on group, was administered. The motor block was evaluated on an abbreviated Bromage scale and we recorded hemodynamic stability, fetal status, type of delivery and the total dose of local anesthetic. RESULTS: Analgesia and hemodynamics were similar in both groups. Group R required a larger number of additional boluses, although the difference was not statistically significant. A motor block was observed in 8 patients in group B and 1 in group R (p < 0.05). Fetal status was similar in both groups. CONCLUSION: Both drugs were equally effective for controlling the pain accompanying labor, such that ropivacaine offered no advantage over bupivacaine in that regard. Ropivacaine's reduced motor block effect at the doses administered may offer an advantage in some situations, such as when a walking epidural is provided.     

Effect of standard diluted epinephrine infusion on epidural anesthesia in labor

BACKGROUND AND OBJECTIVES: Epinephrine is used with local anesthetics to prolong the duration of epidural analgesia and decrease the peak plasma concentrations of local anesthetics. However, the duration of labor may be prolonged because epinephrine reduces uterine activity. We designed a prospective, randomized, and doubleblind study to examine the effects of epinephrine infusion on the quality of analgesia and plasma concentration of local anesthetic, as well as the effect on the uteroplacental circulation, duration of the first or second stage of labor, and fetal outcome. METHODS: Twenty-four parturients received continuous epidural bupivacaine 0.125% (8 mL/h) combined either with epinephrine (40 microg/h) (n = 12) or without epinephrine (n = 12) for analgesia during labor. If patients requested additional analgesia, a bolus of 1% or 1.5% lidocaine (6 to 10 mL) was given. RESULTS: Only the plain bupivacaine group required additional lidocaine. However, epinephrine infusion prolonged the median (range) duration of the second stages of labor: 69 (21 to 231) minutes with epinephrine group versus 31 (8 to 99) minutes without epinephrine group (P < .05), and decreased pH in umbilical artery at the time of delivery. Epinephrine infusion did not change the uterine and umbilical blood flow, which were determined as the resistance indices. Changes in the fetal heart rate and Apgar score were also comparable. Epinephrine significantly reduced the umbilical venous to maternal arterial bupivacaine concentration (P < .05). CONCLUSIONS: A standard diluted epinephrine infusion (40 microg/h) into epidural space decreased anesthetic requirements. The possibility of the prolonged duration of labor remains a problem.     

Continuous extradural infusion of lignocaine 0.75% vs bupivacaine 0.125% in primiparae: quality of analgesia and influence on labour

We studied 86 primiparous women with uncomplicated pregnancy and labour requesting extradural analgesia in labour. All the women were over 36 weeks of gestation with a cephalic-presenting singleton fetus. The women were allocated randomly to two groups: group A, who received an extradural infusion of lignocaine 0.75%, after an initial dose of 10 ml of lignocaine 1.5%, and group B, who received an infusion of bupivacaine 0.125% after an initial dose of 10 ml of bupivacaine 0.25%. All the women had their labour actively managed. Assessment of analgesia during labour and delivery, and the requirements for additional top-ups were noted, as were mode of delivery, requirement for oxytocic augmentation and incidence of fetal distress. Maternal and umbilical cord plasma concentrations of lignocaine were measured at delivery in 12 women receiving extradural lignocaine. There were no statistically significant differences between the two groups in terms of the mode of delivery, incidence of fetal distress, fetal heart rate abnormalities, or Apgar scores of the babies. Women in the bupivacaine group had a significantly better quality of analgesia during both the first and second stages of labour (p = 0.0005) and required fewer top-ups than those in the lignocaine group. However, the requirement for oxytocin augmentation during the first and second stages of labour was significantly less in the lignocaine group (p = 0.004). Similarly, the duration of the second stage was shorter compared with the bupivacaine group. In spite of high plasma concentrations of lignocaine, no side effects were noted in either mothers or babies.     

Comparison between extradural infusion of ropivacaine or bupivacaine for the prevention of postoperative pain after total knee arthroplasty

We have compared the analgesia and motor block produced by extradural infusions of ropivacaine and bupivacaine after total knee arthroplasty. Fifty-two patients received 8 ml h1 of either 0.2% ropivacaine or 0.2% bupivacaine by extradural infusion for 24 h after operation. Analgesia was assessed by postoperative visual analogue scale (VAS) and morphine consumption. At rest these were low in both groups; median VAS was 0- 13.3 mm for the ropivacaine group and 0-0.5 mm for the bupivacaine group. Over the 24 h of the infusion, the estimated (ropivacaine bupivacaine) difference in wound pain at rest was 5.6 mm (P = 0.017) and on passive movement 11.6 mm (P = 0.016). Median morphine consumption was 30.7 mg in the ropivacaine group and 20.5 mg in the bupivacaine group. In the ropivacaine group, 50% of patients compared with 19% in the bupivacaine group had no motor block 2 h after operation, increasing to 88% for ropivacaine and 56% for bupivacaine by 24 h. Bupivacaine produced significantly more frequent and intense motor block over the 24 h (P = 0.015).      

The effects of regional anaesthesia for caesarean section on maternal and fetal blood flow velocities measured by doppler ultrasound

We studied the effects of spinal anaesthesia (Group S), epidural anaesthesia (Group E), and combined spinal and epidural anaesthesia (Group SE), on maternal and fetal blood flow in 24 healthy parturients (n = 8/group) with uncomplicated singleton pregnancies using Doppler technique. Prior to the induction of anaesthesia, the patients were prehydrated with balanced electrolyte solution 15 ml kg^-1 over a period of 15 min. After the induction of regional anaesthesia, the systolic blood pressure was maintained within 15% limits of the preoperative values using prophylactic etilefrine infusion in Groups S and SE. The flow velocity waveforms of the maternal femoral artery, the main branch of the uterine artery (placental side), the foetal umbilical and middle cerebral arteries were recorded by Doppler technique before and after prehydration as well as after onset of T7 analgesia and the pulsatility indices (PI) were derived. Rapid intravenous prehydration had no effects on uteroplacental or fetal circulation as indicated by unaltered uterine, umbilical, and fetal middle cerebral artery Pis. After the onset of T7 analgesia, the uterine artery PI was increased in Group S indicating increased uterine vascular resistance while no changes occurred in Groups E and SE. No adverse effects were observed on the neonates as indicated by the Apgar score and the umbilical artery and vein acid–base status in any of the groups.     

Motor block during epidural infusions for nulliparous women in labour: a randomized double-blind study of plain bupivacaine and low dose bupivacaine with fentanyl

Sixty nulliparous women received epidural infusions in labour of either 0.125% plain bupivacaine or 0.0625% bupivacaine containing 2.5 mcg/ml fentanyl both starting at 12 ml/h and titrated to maintain a sensory block to T10. Those women who received low dose bupivacaine with fentanyl took significantly longer to reach full cervical dilation (P < 0.05). There was no statistical difference between the groups in the number of additional epidural bolus doses required during the infusions. Of the women receiving low dose bupivacaine with fentanyl, 77% required one or no additional top-up doses compared to 87% in the plain bupivacaine group. There was no reduction in the incidence of perineal pain in the group who received fentanyl. Significantly more women who received 0.125% bupivacaine had motor block after 2 h of the infusion (P < 0.05). The mode of delivery was similar in the two groups as was the satisfaction with epidural analgesia in both the first and second stages of labour and with labour overall. There were no significant differences in Apgar scores, umbilical cord blood pH levels or neurologic and adaptive capacity scores at 2 or 24 h. There was no significant difference in the incidence of symptoms 24 h after delivery.     

Feasibility of electromyography (sEMG) in measuring muscular activity during spinal anaesthesia in patients undergoing knee arthroplasty

BACKGROUND: Bromage scale (0-3) is used to measure the degree of motor block during spinal anaesthesia. However, an estimation of motor block is difficult during surgery. The purpose of this study was to evaluate the feasibility of surface EMG describing spontaneous muscular activity in the lower extremities during spinal anaesthesia. METHODS: In part I of the study, 13 patients undergoing day case surgery were studied. They received 10 mg hyperbaric bupivacaine at interspace L3-4. EMG, sensory and muscular block were measured at 5-min intervals during the first 30 min and then every 15 min until the patient was able to flex the knee. In part II of the study, 16 patients undergoing knee arthroplasty received 10 mg bupivacaine through spinal catheter at interspace L3-4 (Group CSA). An additional bolus of 2.5 mg was administered using EMG-guidance, if needed. Another group, 15 patients, received a single bolus of bupivacaine (15-20 mg) at L3-4 (Group Bolus). EMG, muscular and sensory block were monitored as described above. The epidural catheter was used as rescue. RESULTS: Part I: EMG compared to modified Bromage scale showed a significant correlation (P < 0.01, Spearman rank correlation). Part II: The amount of bupivacaine was significantly reduced with EMG guidance when compared with the single bolus group (14.0 mg vs. 17.0 mg) (P < 0.05 Mann-Whitney U). Motor block started to recover before the sensory block in 7/15 CSA patients vs. 1/15 Bolus patient. CONCLUSION: Stable maximal sensory block does not necessarily correlate with adequate motor block in patients receiving spinal anaesthesia induced with small bolus doses. In spite of electrical noise, EMG-guided administration of spinal anaesthesia significantly reduced the amount of bupivacaine compared to the hospital routine. Further studies are needed to develop the method.     

MECHANISM OF EXTENSION OF SPINAL ANAESTHESIA BY EXTRADURAL INJECTION OF LOCAL ANAESTHETIC

We have examined the effect of extradural injection of 0.5%bupivacaine or normal saline on the progression of spinal anaesthesiain 28 patients undergoing Caesarean section. Three groups werestudied. Subarachnoid anaesthesia was established in all patients.Group A (n = 10), the control, received no extradural injectionfor 20 min. Group B (u= 9) received extradural bupivacaine 10ml and group C (n = 9) received extradural saline 10 ml 5 minafter the subarachnoid injection. Sensory levels were comparedat 5-min intervals and extension of the block was found to besimilar in groups B and C and significantly faster than thecontrol (P < 0.05). The quality of anaesthesia and incidenceof adverse effects was similar for all three groups. We concludethat the mechanism of extension of spinal anaesthesia by extraduralinjection of local anaesthesia is largely a volume effect. (Br.J. Anaesth. 1992; 69: 457–460) ^*Present address, for correspondence: Department of Anaesthetics,Freeman Hospital, High Heaton, Newcastle Upon Tyne NE7 7DN.