COMPARISON OF BUPIVACAINE AND BUPIVACAINE WITH FENTANYL IN CONTINUOUS EXTRADURAL ANALGESIA DURING LABOUR

In a randomized, double-blind study of 39 mothers in labour,we have compared a loading dose of 0.5% bupivacaine 6.0 ml andfentanyl 100 µg given extradurally, followed by an infusionof 0.08% bupivacaine 15 ml h^–1 plus fentanyl 37.5 µgh^–1, with a loading dose of 0.5% bupivacaine 6.0 ml andsaline 2.0 ml, followed by an extradural infusion of 0.08% bupivacainealone, per hour. Analgesic levels were more consistent and sustainedin mothers who received fentanyl in addition to bupivacaine,and the duration from the time of the loading dose to the firsttop-up was extended considerably in this group. The only significantside effect was a high incidence of mild pruritus in the fentanylgroup. The addition of fentanyl to the extradural loading doseand subsequent infusion of local anaesthetic is a satisfactoryalternative to giving higher doses of local anaesthetic alone.     

EFFECT OF NALOXONE ON GASTRIC EMPTYING DURING LABOUR

The rate of gastric emptying was studied in 30 women duringlabour. All the women had received pethidine 100 mg i.m. foranalgesia and, subsequently, extradural analgesia had been establishedfor obstetric indications. The women were allocated randomlyto two groups: 15 received naloxone 1.2 mg i.v. and 15 weregiven saline 3 ml (placebo). All 30 patients were then givenparacetamol 1.5 g orally with water 100 ml. The amount of paracetamolabsorbed, and hence gastric emptying, was significantly greaterin the naloxone group in the first 30 min following the administrationof the paracetamol. ^*Present Addresses: Department of Anaesthesia, Southern GeneralHospital, 1345, Govan Road, Glasgow G51 4TF. Present addresses: Department of Anaesthesia, Ninewells Hospital,Dundee.     

GASTRIC EMPTYING FOLLOWING HYSTERECTOMY WITH EXTRADURAL ANALGESIA

Using the rate of absorption of paracetamol following oral administrationof the drug, gastric emptying was measured in 21 patients followinghysterectomy. Gastric emptying was inhibited markedly in patientsreceiving narcotic analgesia after operation, but only a moderatedelay was observed in patients undergoing extradural analgesia.     

CHANGES IN FETAL TCPO2 VALUES OCCURRING DURING LABOUR IN ASSOCIATION WITH LUMBAR EXTRADURAL ANALGESIA

Forty-six of 64 high risk labours were managed with continuouslumbar extradural analgesia. Fetal heart rate (FHR) and continuoustranscutaneous PO₂ (tcPO₂) measurements were made in the 64patients. Abnormal fetal heart rate patterns and low tcP0₂ valuesassociated with the onset of the extradural block were notedin 9% of these cases A decrease in maternal arterial pressureand uterine hypertonus appeared to be responsible, singly orm combination, for the changes. These effects and the changesin FHR were not seen in the 18 mothers not receiving extraduralanalgesia. The supine position was associated with slightlysmaller fetal tcPo2 values than the preferred lateral positions,with a significant worsening of the fetal tcPo2 values afterinduction of the extradural block although, overall, extraduralanalgesia neither improved nor impaired the fetal tcPo2     

EXTRADURAL ANALGESIA DURING LABOUR USING ALFENTANIL

Sixteen primiparous patients requesting pain relief during labourreceived a continuous infusion of alfentanil 30 µg kg^–1h^–1 via an extradural catheter. Supplementary (extradural)bolus doses {30 µg kg^–1) were administered whendeemed necessary. Excellent pain relief was rapidly obtainedearly in labour in all patients. However, analgesia was inadequatein the latter part of stage I and during the second stage infive of the 16 patients—notwithstanding several additionaldoses of alfentanil, and bupi-vacaine had to be administered.No serious maternal side-effects, except nausea, were en-countered.Although all neonatal Apgar scores were between 7 and 10, theAmiel-Tison test clearly indicated the existence of neonatalhypotonia. The continuous extradural administration of alfentanilproved to be unsatisfactory for pain relief in labour.     

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.     

LACK OF EFFECT OF KETAMINE ANALGESIA ON GASTRIC EMPTYING IN MAN

The effect of ketamine analgesia on gastric emptying was assessedin five healthy volunteers. Gastric emptying, estimated indirectlyby the absorption of orally administered paracetamol, was notsignificantly delayed following administration of i m. ketaminewhen compared with placebo.     

A CONTROLLED TRIAL OF EXTRADURAL FENTANYL IN LABOUR

In a double-blind trial carried out on patients in the firststage of labour, either fentanyl 80 µg (n = 35) or physiologicalsaline (n=33) was added to the test dose of bupivacaine andadministered extradurally Thereafter analgesia was maintainedas necessary with 0.5% bupivacaine alone Supplementary bupivacaine(a further dose within 1 h) was required to produce satisfactoryanalgesia in eight patients in the fentanyl group and in 26patients in the control group. Analgesia was more rapid in onsetand more complete in the fentanyl group, and the duration fromfirst dose to first top-up was 2.36 h, compared with 1 66h (supplementsnotwithstanding) in the control group No serious side-effectswere encountered in either group, although eight patients inthe fentanyl group experienced mild itching, compared with onein the control group     

MATERNAL TEMPERATURE REGULATION DURING EXTRADURAL ANALGESIA FOR LABOUR

We have studied the effect of analgesia on maternal temperature(oral and tympanic membrane) progression in 53 women duringnormal spontaneous labour. Three groups were studied: two receivedextradural analgesia with a continuous infusion of 0.25% bupivacainewith or without the addition of fentanyl; the third group receivedonly parenteral opioid analgesia. All patients were afebrileand without clinical evidence of infection at the beginningof the study. Both groups of patients receiving extradural analgesiahad a consistent and significant increase in temperature afterapproximately 5 h of analgesia; no such trend was observed inthe parenteral opioid group. Alterations in mechanisms of heatdissipation may explain these findings.     

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.     

PLACENTAL BLOOD FLOW DURING CAESAREAN SECTION UNDER LUMBAR EXTRADURAL ANALGESIA

The effect on intervillous blood flow of lumbar extradural analgesiafor Caesarean section was studied in nine healthy women usingxenon-133. Extradural anaesthesia was performed with lignocaine1% 16–20 ml with adrenaline 6µg ml^–1. Impairmentof placental blood flow during the block was observed in sevenpatients, but the mean decrease (13% from the control value)was not statistically significant. The most notable decreasein intervillous blood flow occurred in two patients with simultaneousarterial hypotension.     

THE OCCURRENCE OF UNBLOCKED SEGMENTS DURING CONTINUOUS LUMBAR EPIDURAL ANALGESIA FOR PAIN RELIEF IN LABOUR

The records of a consecutive series of 920 cases of continuouslumbar epidural analgesia for the control of pain in labourwere examined to ascertain the incidence of unilateral blockand unblocked segments. An unblocked segment was noted to haveoccurred in 6.7 per cent of patients and was persistent in 1.5per cent of patients. Unilateral block occurred in 1.5 per centof patients, being persistent in 0.54 per cent. Present address: Anaesthetic Department, East Birmingham Hospital,Birmingham 9, England.     

PLASMA CONCENTRATIONS OF BUPIVACAINE DURING CONTINUOUS EPIDURAL ANALGESIA IN LABOUR: THE EFFECT OF ADRENALINE

Continuous epidural analgesia has been provided for eighteenpatients during the first and second stages of labour. Ninepatients received bupivacaine 0.5 per cent with adrenaline 5µg/ml, and nine bupivacaine alone, using a double-blindtechnique. The initial dose of bupivacaine was 30 mg, repeatedand increased as necessary. A total of fifty-nine doses wasgiven. Plasma concentrations of bupivacaine were measured inthe mother throughout the blockade, and in the baby at delivery.The duration of action of bupivacaine was not significantlyprolonged by adrenaline, though plasma concentrations were significantlyreduced 20 minutes after the first dose and 40 minutes afterthe second. In neither treatment group did bupivacaine accumulatemarkedly in maternal plasma unless the second stage necessitatedincreased doses. Neonatal bupivacaine concentrations were alwayslow and neonatal: maternal ratios increased by the use of adrenaline.It is thus uncertain whether adrenaline offered a significantadvantage except with large doses of bupivacaine, when it reducedthe likelihood of maternal intoxication.     

EFFECT OF ALCOHOL ON GASTRIC EMPTYING IN VOLUNTEERS

We have examined the effect of alcohol on the gastric emptyingrate of a liquid meal in 10 volunteers. Each volunteer was allocatedrandomly to receive, on three occasions, no alcohol, 3 unitsor 6 units of alcohol. Gastric emptying was measured using appliedpotential tomography. The rate of gastric emptying as measuredby the time to 50% emptying (T₅₀) was delayed significantly(P < 0.01) after alcohol 6 units (median 45.0 mm (range 19–90min)) compared with control (23.0 min (13–36 min)) andthere was little change after alcohol 3 units (25.5 min (10–41min)). (Br. J. Anaesth. 1993; 71: 674–676) Provisional data from this study were presented to the AnaestheticResearch Society at Cambridge (British Journal of Anaesthsna1992; 68: 447P)     

ANTRODUODENAL MOTILITY, pH AND GASTRIC EMPTYING DURING BALANCED ANAESTHESIA: COMPARISON OF PETHIDINE AND FENTANYL

In a randomized study of 22 patients, antroduodenal motility,pH and gastric emptying rate were measured during barbiturateanaesthesia with pethidine or fentanyl. Motility was measuredby manometry and gastric emptying rate by the paracetamol absorptiontest. Anaesthesia reduced the duration of the interdigestivemotility complexes with both analgesics (P < 0.001), mainlyby a shortening of phase Il (P < 0.01) The duration of phaseII and III were shorter with pethidine, and pethidine reducedboth the frequency and amplitudes of antral contractions duringphase II (P < 0.01). Fentanyl affected only the amplitudes.The phase III variables assessed were unchanged, apart froma decrease in the velocity of propagation of the motility complexeswith pethidine (P < 0.01). The gastric pH increased in bothgroups during and after operation (P < 0.01). Gastric emptyingrate was normal in 82% with fentanyl and in 60% with pethidine.Motility in the recovery period approached, but did not reach,preoperative values. Balanced anaesthesia with pethidine andfentanyl seem to have minor influence on gastroduodenal motilityand gastric emptying rate.     

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.     

EFFECT OF MATERNAL POSITING ON FETAL HEART RATE DURING EXTRADURAL ANALGESIA

Using continuous cardiotocography, the effect of maternal positionon fetal heart rate (FHR)was studied during extradural analgesia(EA) with either 50 or 100 mg of etidocaine without adrenalinefor labour and vaginal delivery. Of 79 healthy parturients,39 were supine and 40 were in the lateral position. FHR wasnormal in all patients during the control period before EA,and remained normal during EA in 53. Transient abnormal patternsoccurred in 26 patients, 22 (56%) in the supine group and four(10%) in the lateral group, a significant difference (P 0.001).The decrease in arterial pressure (AP) did not differ betweenthe groups, but the frequency of abnormal FHR associated witha small or moderate decrease in AP (30% or less) was greaterin the supine (51%) than in the lateral group (3%)     

EFFECT OF ANXIETY ON GASTRIC EMPTYING IN PREOPERATIVE PATIENTS

On the morning of operation 30 patients awaiting minor gynaecologicalsurgery completed a Spielberger State Trait Anxiety Inventory.Gastric emptying was then measured using paracetamol absorption.Anxiety State scores, which reflected situational anxiety, wereunrelated to Anxiety Trait scores, which assessed anxiety proneness.Paracetamol absorption was reduced and delayed in patients withlow anxiety trait who developed high anxiety state before surgery,compared with patients whose anxiety state scores were lowerthan, or similar to, their anxiety trait scores. Therefore,it was concluded that gastric stasis occurred in patients witha low predisposition to anxiety who became apprehensive whilstawaiting surgery.     

EFFECT OF CISAPRIDE ON MORPHINE-INDUCED DELAY IN GASTRIC EMPTYING

Forty patients were allocated randomly to receive one of fourpremedications i.m.: placebo only, morphine 10 mg plus placebo,morphine 10 mg plus cisapride 10 mg and morphine 10 mg pluscisapride 4 mg. Gastric emptying after each premedication wasassessed using the oral paracetamol absorption model. The morphineonly group and the morphine and cisapride 4 mg group showeddelayed gastric emptying when compared with the placebo group.Delay in gastric emptying in the morphine and cisapride 10 mggroup was not demonstrated. It is concluded that cisapride 10mg prevents the delay in gastric emptying associated with theadministration of morphine.     

EFFECT OF EXTRADURAL COMPLIANCE AND RESISTANCE ON SPREAD OF EXTRADURAL ANALGESIA

We have studied the effect of extradural compliance and extraduralresistance on the spread of extradural analgesia. In 111 patientsaged 21–75 yr, compliance and resistance of the extraduralspace were calculated by a mathematical analysis (using theWindkessel theory) of the extradural pressure-response curveto injection of a given volume of local anaesthetic. The calculatedmean extradural compliance was 0.39 (SD 0.13) ml mm Hg^–1and this increased with advancing age (P < 0.01). The totalnumber of analgesic segments blocked was related to extraduralcompliance (P < 0.01). Segmental dose requirement was relatedinversely to extradural compliance (P < 0.01). Calculatedextradural resistance was 26.8 (14.5) mm Hg s ml^–1 andthis decreased with advancing age ( P < 0.05). The totalnumber of analgesic segments blocked was related inversely toextradural resistance ( P < 0.05). Segmental dose requirementwas related to extradural resistance (P < 0.05).