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.     

Uteroplacental and fetal haemodynamics and cardiac function of the fetus and newborn after crystalloid and colloid preloading for extradural Caesarean section anaesthesia

We have studied the effects of randomized preloading with eithera crystalloid (lactated Ringer's) 15 ml kg^–1 or colloid(hydroxyethyl starch) 7.5 ml kg^–1 solution in 20 parturientsundergoing elective Caesarean section under extradural anaesthesia,on blood flow in maternal placental and non-placental uterineand placental arcuate arteries and in fetal umbilical, renaland middle cerebral arteries, using a pulsed colour Dopplertechnique. Simultaneously, fetal and neonatal myocardial functionwere investigated by pulsed Doppler and M mode echocardiography.We found no changes in maternal or fetal blood velocity waveformindices after crystalloid preloading, but the pulsatility indexof the maternal non-placental uterine artery in creased significantlyafter colloid preloading. Fetal heart rate decreased after preloadingwith crystalloid solution. There were no differences in fetalor neonatal myocardial function between the groups, and theoutcome of the newborn infants were uneventful in all cases.These results suggest that preloading with either a crystalloidor colloid solution may lead to different uterine and fetalhaemodynamics but these solutions had only minimal effects onfetal and neonatal myocardial performance and no effect on theclinical condition of newborns in uncomplicated pregnancies.     

EFFECT OF TIME AND ADRENALINE ON THE FETOMATERNAL DISTRIBUTION OF BUPIVACAINE

Following lumbar extradural analgesia with 0.5% bupivacaine,the placental transfer of bupivacaine was examined in 40 womenundergoing elective and 40 women undergoing emergency Caesareansection. Within each group, the patients received randomly eitherplain bupivacaine or bupivacaine with adrenaline 1 in 200000.Plasma bupivacaine concentrations were measured in blood samplestaken simultaneously at delivery from the umbilical vein (UV),umbilical artery (UA) and maternal vein (MV). Bupivacaine concentrationsin MV, UV and UA were not significantly affected by the presenceof adrenaline, but were positively correlated with first doseto delivery interval (FDD) while MV and UV were inversely correlatedwith last dose to delivery interval (LDD). Mean ratio of UV:MVconcentrations of bupivacaine was 0.346 and for UA:MV it was0.305. There was no significant correlation between any fetal:maternal ratio and FDD or LDD. UA:UV ratio appeared to increasetowards unity 30–40 min after the last dose. The presenceof adrenaline was associated with an increase in UA:UV in theelective group (P <0.01). In eight patients who receivedadrenaline there was reverse placental transfer (UA:UV >1). There was no evidence of progressive fetal accumulationof bupivacaine beyond 30–40 min. ^* Present address: St Thomas' Hospital London SE1 7EH     

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.     

Extradural clonidine combined with sufentanil and 0.0625% bupivacaine for analgesia in labour

We have studied the use of clonidine combined with low doses of sufentanil and bupivacaine in 45 parturients requiring extradural analgesia for the first stage of labour, in a double-blind, randomized study. We gave 0.0625% bupivacaine 10 ml containing 1:200,000 adrenaline and sufentanil 10 micrograms (1 ml) to which was added 0.9% saline, or clonidine 100 or 150 micrograms (1 ml). We compared the quality (VAS scores) and duration of analgesia, motor block, maternal haemodynamic state (mean arterial pressure and heart rate) and fetal and maternal side effects. Mean duration of anaesthesia was prolonged slightly: 105 (SD 21) min without clonidine, 130 (26) min with clonidine 100 micrograms (P < 0.05 vs control) and 144 (40) min with clonidine 150 micrograms (P < 0.01 vs control, ns vs 100 micrograms). There were no differences in VAS scores, onset times, heart rate, ventilatory frequency, motor block, sedation, pruritus or bradycardia between the groups. Analgesia was associated with a reduction in mean arterial pressure with clonidine. However, these adverse side effects were of minor clinical importance regardless of the extradural clonidine dose, except for a high incidence of fetal heart tracing abnormalities when clonidine 150 micrograms was used. These effects associated with a limited effect on analgesia may curtail the widespread use of clonidine as an adjunct to extradural 0.0625% bupivacaine with sufentanil 10 micrograms during labour.      

EFFECT OF ADRENALINE ON THE DISTRIBUTION OF BUPIVACAINE IN THE RABBIT FETUS

Adrenaline may decrease uterine blood flow and influence transplacentaldistribution of bupivacaine. Sixteen pregnant rabbits receivedan i.v. infusion of 0.125% bupivacaine either plain (n = 8)or with adrenaline 1.25 µg ml^–1. At 15-min intervalsfollowing the start of the infusion, rabbit fetuses were removedserially and bupivacaine concentrations measured in maternalarterial plasma, fetal plasma and brain, amniotic fluid andplacenta. The presence of adrenaline was associated with increasedbupivacaine concentration in placenta; there was no other significanteffect on fetal bupivacaine concentrations or ratios. Fetal:maternal plasma ratios increased (P < 0.05), while fetalbrain: fetal plasma ratios decreased (P < 0.05) significantlywith time.     

EFFECT OF SEGMENTAL EXTRADURAL ANALGESIA ON PLACENTAL BLOOD FLOW DURING NORMAL LABOUR

Placental blood flow was measured during the first stage ofnormal labour using a xenon-133 clearance technique before andafter segmental extradural analgesia. Analgesia was producedwith 0.5% plain bupivacaine in eight patients and with 0.5%bupivacaine-adrenaline in 10 patients. Segmental extraduralanalgesia with a small dose (20 mg) of bupivacaine did not changeplacental blood flow significantly. The addition of adrenaline20 µg produced no effect.     

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.     

Single bolus compared with a fractionated dose injection technique of bupivacaine for extradural Caesarean section: effect on uteroplacental and fetal haemodynamic state

We studied 26 healthy parturients undergoing elective Caesarean section, allocated randomly to receive extradural block with 0.5% plain bupivacaine in a double-blind manner in either a single bolus or fractionated doses. After a 3-ml test dose, an additional 20 ml of bupivacaine were given over a 5-min period in the single bolus group (n = 13) and over a 25-min period in the fractionated dose group (n = 13). We studied the effects of bupivacaine on blood flow velocities in the maternal placental and non-placental uterine and fetal umbilical arteries before and four times during establishment of extradural block using a pulsed colour Doppler technique. Median sensory block reached T3 in the single-dose group compared with T4 in the fractionated-dose group. Two subjects in each group required i.v. ephedrine to correct transient hypotension (systolic arterial pressure < 90 mm Hg). Blood flow velocity waveform indices of the uterine and umbilical arteries did not differ significantly within or between groups during the study. There was no significant difference in neonatal outcome, as assessed by Apgar scores and umbilical artery pH values. In conclusion, we observed no deterioration in uteroplacental circulation after administration of a single bolus dose of bupivacaine.      

EFFECT OF ADRENALINE ON PLACENTAL TRANSFER OF BUPIVACAINE IN THE PERFUSED IN SITU RABBIT PLACENTA

Following general anaesthesia, each of 18 pregnant rabbits receivedan i.v. infusion, at a declining rate, of 0.125% bupivacaine,either plain solution followed by adrenaline (1.25 µgml^–1)-containing solution (n = 10) or vice versa (n =8). All solutions contained antipyrine as an index of placentalexchange. In each rabbit, a single fetal sac was opened, theumbilical vessels were cannulated and the placenta was perfusedin situ with buffered Krebs solution containing Dextran. Bupivacaineand antipyrine concentrations were measured in effluent perfusate(fetal) and in maternal plasma sampled simultaneously. Meanmaternal arterial pressure and mean placental perfusion pressurewere not altered by adrenaline. Fetal:maternal concentration(F: M) ratios of antipyrine decreased significantly (P <0.05) during the second half of the experiment. In contrast,F: M ratios of bupivacaine were unchanged during the time courseof the experiment and unaltered by the addition of adrenaline.It is concluded that neither adrenaline nor minor alterationsin maternal placental flow affect placental transfer of bupivacaine.     

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 EXTRADURAL ANAESTHESIA ON HUMAN FETAL BLOOD FLOW IN UTERO: Comparison of Three Local Anaesthetic Solutions

Twenty-seven women, scheduled for elective Caesarean sectionunder extradural anaesthesia were allocated randomly to oneof three groups: group Ea received 1.5% etidocaine with adrenaline,group Bp 0.5% bupivacaine plain, and group Ba 0.5% bupivacainewith adrenaline. There was no difference in the quality anddistribution of sensory blockade between the three groups. Motorblockade was most profound in group Ea. Maternal heart rateand arterial pressure were only slightly affected in the threegroups. Before induction of extradural anaesthesia, and 15 and30 min after, fetal umbilical and aortic blood flows were examinedusing a combination of real-time ultrasono-graphy and the pulsedDoppler technique. Blood flow in the umbilical vein was notaffected in any of the groups, and blood flow in the fetal aortaremained unchanged in groups Ea and Bp, but was increased by12% after 30 min in group Ba. We conclude that, with the threelocal anaesthetic solutions studied during extradural anaesthesiafor elective Caesarean section, fetal circulatory variablesremained stable and within normal limits, when in associationwith normal values of maternal arterial pressure.     

BLOOD LOSS IN TOTAL HIP REPLACEMENT: EXTRADURAL v. PHENOPERIDINE ANALGESIA

The effects of phenopendine and extradural analgesia on bloodloss during and after total hip replacement were compared in41 patients randomly divided into two statistically comparablegroups. Mean blood loss in patients who received phenoperidinewas 1065 ± 316ml and in patients who received extraduralanalgesia with 0 5% bupivacaine with adrenaline 1:200 000 itwas 650 ±277 ml (P <0 001). There was no significantdifference in postoperative blood loss between the two groupsThe reduction in blood loss resulting from the extradural blockmay prove beneficial in decreasing the hazard and cost of bloodtransfusions and in facilitating autologous transfusion.     

The effects of ephedrine and etilefrine on uterine and fetal blood flow and on fetal myocardial function during spinal anaesthesia for caesarean section

The effects of two vasopressors, ephedrine and etilefrine, on blood flow in maternal uterine, fetal umbilical, middle cerebral and renal arteries and on fetal myocardial function were studied by colour Doppler and M-mode echocardiography techniques during spinal anaesthesia for caesarean section. There were 7 healthy pregnant women in each treatment group. The vascular resistance of maternal uterine arteries increased significantly after both of the vasopressors while the vascular resistance of the umbilical artery remained unchanged. Ephedrine decreased the blood velocity waveform indices in the fetal middle cerebral and renal arteries, increased fetal right ventricular contractility and decreased left ventricular inner end-diastolic dimension. Fetal heart rate was unchanged. Etilefrine caused no detectable changes in fetal haemodynamics or in fetal myocardial function. These findings demonstrate that vasopressors administered for the treatment of minor maternal arterial pressure fall produce vasoconstriction in the uterine circulation during spinal anaesthesia, yet healthy fetuses seem to tolerate these haemodynamic alterations well. On the other hand, ephedrine caused changes in fetal myocardial function and in the vascular resistance of fetal middle cerebral and renal arteries, which demonstrates the potential modifying effect of vasoactive drug given to the mother on fetal haemodynamics.     

Factors affecting the maternal-fetal distribution of pethidine and bupivacaine in the rabbit

Twenty pregnant New Zealand white rabbits (mean body weight 4.6 kg) within 3 days of term were anaesthetized and given an intravenous infusion of bupivacaine 1.25 mg/ml with pethidine 1.25 mg/ml at a rate of 12 ml/h for 20 min, 6 ml/h for 60 min and 3 ml/h thereafter. In 10 of the does the solution also contained adrenaline 1.25 microg/ml. Up to 8 fetuses were removed at 15 min intervals from the start of the infusion and umbilical vein pH was measured, together with bupivacaine and pethidine concentrations, in fetal plasma, fetal brain and maternal plasma sampled synchronously. Mean umbilical vein pH fell with time with no significant difference between the groups. Maternal plasma concentrations of both drugs did not alter significantly during the experiment. Maternal clearance of bupivacaine was 85.6 ml/min and of pethidine was 249 ml/min. Despite the three-fold higher maternal plasma concentrations of bupivacaine, concentrations of pethidine in fetal plasma and brain were consistently higher than those of bupivacaine. Fetal plasma pethidine concentrations rose 0.276 microg x ml(-1)h(-1) and bupivacaine concentrations rose 0.184 microg x ml(-1)h(-1). The mean (+/-SD) maximum fetal: maternal plasma ratio for bupivacaine was 0.361+/-0.127 and for pethidine 1.78+/-0.81. The fetal brain:plasma ratio of pethidine was consistently higher than that of bupivacaine and did not change significantly with time, whereas that of bupivacaine fell significantly (P<0.05). Concentrations of bupivacaine and pethidine in fetal and maternal brain were consistently higher with adrenaline, although adrenaline had no significant effect on the concentrations in this or any compartment.     

Speed of onset of sensory block for elective extradural Caesarean section: choice of agent and temperature of injectate

We have studied the effects of choice of local anaesthetic andtemperature of extradural injectate on speed of onset of sensoryblock for elective extradural Caesarean section in a double-blindtrial in 120 women allocated randomly to one of four groupsto receive either plain 0.5% bupivacaine or 2% lignocaine with1:200000 adrenaline at either room temperature or 38°C.The onset time of lignocaine with adrenaline was shorter thanthat of bupivacaine regardless of temperature (P < 0.01).Warmed lignocaine produced the most rapid block overall (P <0.025). The incidence of hypotension, ephedrine requirement,shivering, quality of analgesia and additional analgesic requirementswere similar for all groups.     

CONTINUOUS EXTRADURAL ANAESTHESIA IN CHILDREN: Clinical and Haemodynamic Implications

This study reports the experience of a department of paediatricanaesthesia with 234 continuous extradural anaesthetics performedin 229 children over a 15-month period. Fifty-nine of the childrenwere aged 0–2 yr, 71 were aged 2–8 yr and 104 wereolder than 8 yr. The surgical procedures lasted more than 60min (mean 150±10.6 min); all were carried out under lightgeneral anaesthesia. Technical procedure and difficulties arereported. The only local anaesthetic agent used was bupivacainewith or without adrenaline. Mean initial dosage was 0.75 mlkg^–1 for children weighing less than 20 kg and 1 ml/10cm of height for children taller than 100 cm. Using 0.25% bupivacainemean times until a further injection were 92.0±2.0 minfor bupivacaine with adrenaline and 71.0±2.5 min forbupivacaine without adrenaline (P < 0.001). A much longerduration of analgesia was found for younger children using thesolution with adrenaline. A haemodynamic study was performedin 74 unpremedicated children (ASA l; aged 0–2 yr (n =15), 2–8 yr (n = 26) and older than 8 yr (n = 35)). Beforeinduction of anaesthesia, heart rate (HR) was significantlyincreased in the youngest children, but no significant changewas found for systolic arterial pressure (SAP). After extraduralanaesthesia with 0.25% bupivacaine with adrenaline 1:200000,minimal changes in HR or SAP occurred in children younger than8 yr; in those older than 8 yr a significant decrease in bothHR and SAP was observed. Changes in SAP were at their maximum25 min after the extradural block and changes in HR were notstatistically significant before the 25th min following injectionof local anaesthetic. The catheter remained in place in 155children for postoperative analgesia, mainly for the first 48h.     

INFLUENCE OF TIMING ON THE EFFECT OF CONTINUOUS EXTRADURAL ANALGESIA WITH BUPIVACAINE AND MORPHINE AFTER MAJOR ABDOMINAL SURGERY

We have studied the effect of continuous extradural analgesiawith bupivacaine and morphine, initiated before or after colonicsurgery, in a double-blind, randomized study. Thirty-two patientswere allocated randomly to receive an identical extradural blockinitiated 40 min before surgical incision (n = 16) or at closureof the surgical wound (n = 16). The extradural regimen consistedof a bolus of 7 ml of plain bupivacaine 7.5 mg ml^–1 plusmorphine 2 mg and continuous extradural infusion of a mixtureof bupivacaine 7.5mg ml^–1 plus morphine 0.05 mg ml^–1,4 ml h^–1 for 2 h, followed by a continuous extraduralinfusion of a mixture of bupivacaine 2.5mgml^–1 plus morphine0.05 mg ml^–1, 4 ml^–1 h^–1, continued for 72h after operation. In addition, all patients received similargeneral anaesthesia. There was no significant difference inrequest for additional morphine and no significant differencesbetween the groups in pain scores (visual analogue scale orverbal) during rest or ambulation at any time of measurement.These results do not suggest that timing of analgesia with aconventional extradural regimen is of major clinical importancein patients undergoing colonic surgery     

COMPARISON OF FOUR SUBARACHNOID SOLUTIONS IN A NEEDLE-THROUGH-NEEDLE TECHNIQUE FOR ELECTIVE CAESAREAN SECTION

We have used both spinal and extradural anaesthesia with a 26-gauge,long spinal needle through a 16-gauge Tuohy needle for electiveCaesarean section. Four different subarachnoid solutions ofbupivacaine were compared: 0.5% heavy bupivacaine alone, orwith adrenaline, fentanyl or adrenaline and fentanyl. The incidenceof complications and time of regression of the sensory blockwere analysed. The technique is recommended because it allowsrapid onset of anaesthesia and the advantages of an extraduralcatheter. The subarachnoid solution of choice was 0.5% heavybupivacaine 12.5 mg with fentanyl 10 µg     

Effect of adrenaline, fentanyl and warming of injectate on shivering following extradural analgesia in labour

This prospective, controlled study was undertaken to determine whether addition of adrenaline or fentanyl to bupivacaine or warming of the injectate had any effect on the incidence of shivering following extradural analgesia in the labouring parturient. Eighty-four patients were sequentially allocated to four groups (control, warm injectate, extradural adrenaline and extradural fentanyl). The adrenaline group had the highest incidence of shivering, the warm injectate and fentanyl groups the lowest. Extradural fentanyl also seemed promising in reducing shivering in pre-block shiverers. This paper also explores the rapidity of temperature decay of solutions of bupivacaine in different clinical situations.