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.     

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.     

BUPIVACAINE TOXICITY IN ASSOCIATION WITH EXTRADURAL ANALGESIA FOR CAESAREAN SECTION

Evidence of central nervous system toxicity was noted in twopatients undergoing extradural analgmia for Caesarean section.There was no cardiovascular depression and both patients recoveredrapidly. The patients had received total doses of bupivacaineplain solution of 357.5 mg and 356.25 mg, respectively and therelationship of these to the clinical signs of bupivacaine toxicityis discussed.     

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.     

EXTRADURAL ANAESTHESIA FOR CAESAREAN SECTION IN ACHONDROPLASIA

We describe the successful management of a 26-yr-old achondroplasticdwarf undergoing elective Caesarean section under extraduralanaesthesia. The patient had marked thoraco-lumbar kyphoscoliosisand clinical features which suggested that tracheal intubationwould prove difficult. Block sufficient for surgery requiredonly 5 ml of 0.5% bupivacaine and, apart from an initial unilateralblock and mild intraoperative hypotension, her perioperativecourse was uneventful. ^* Present address: Department of Anaesthesia, Green Lane Hospital,Green Lane, Auckland, New Zealand.     

MATERNAL AND FETAL HAEMODYNAMIC EFFECTS OF SPINAL AND EXTRADURAL ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION

Serial haemodynamic investigations were performed in 32 womenwho were allocated randomly to receive either spinal or extraduralanaesthesia for elective Caesarean section. Cardiac output wasmeasured by Doppler and cross-sectional echo-cardiography atthe aortic valve. Doppler flow velocity waveforms were recordedalso from the umbilical artery. Preloading with Ringer lactatesolution 1 litre increased cardiac output in both groups. Afterinjection of bupivacaine, cardiac output remained increasedin the extradural group, but decreased in the spinal group.This was associated with an increase in umbilical artery pulsatilityindex in the spinal group. Umbilical artery pH was less in thespinal group (7.22 vs 7.27). although no neonate was depressedat birth. The maximum percentage change in cardiac output andumbilical artery pulsatility index correlated with umbilicalartery pH (r = 0.54, r = 0.72, respectively). There was no significantcorrelation with change in arterial pressure.     

EXPERIENCES WITH LUMBAR EXTRADURAL ANALGESIA FOR CAESAREAN SECTION

The results of 324 Caesarean sections conducted under lumbarextradural block are discussed. In addition to pre-loading withfluid i.v. and the avoidance of aorto-caval compression, morerecent modifications have been to administer bupivacaine inincremental doses, to be less concerned with the size of thetotal dose, and to provide the mother with supplementary oxygenuntil delivery. As a result of these modifications, the frequencyof maternal discomfort and hypotension has been reduced, andthe need for supplementary analgesia or a vasopressor has becomea rarity. Administration of diazepam after delivery is stilloccasionally advisable. The technique has many advantages forboth mother and infant and with a good obstetric service, fewdisadvantages. Prolongation of the interval between incisionof the myometrium and delivery appears to be less detrimentalto the infant than is the case when general anaesthesia is used.     

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.     

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.     

COMPARISON OF PLAIN AND ALKALINIZED LOCAL ANAESTHETIC MIXTURES OF LIGNOCAINE AND BUPIVACAINE FOR ELECTIVE EXTRADURAL CAESAREAN SECTION

We have examined a local anaesthetic mixture of 0.5% bupivacaine10 ml and 2% lignocaine 10 ml with adrenaline 1 in 200000, towhich 8.4% sodium bicarbonate 2ml was added, for extraduralCaesarean section. The alkalinized mixture of local anaestheticsproduced a block of more rapid onset and density than a mixtureof bupivacaine and lignocaine alone (p < 0.001). ^*Present address: Department of Anaesthetics, Hammersmith Hospital,Du Cane Road, London.     

EXTRADURAL ABSCESS COMPLICATING EXTRADURAL ANAESTHESIA FOR CAESAREAN SECTION

Extradural abscess has been described infrequently as a complicationof extradural anaesthesia and analgesia. We describe an abscessthat developed 5 days after operation in a patient who had extraduralanaesthesia for Caesarean section and postoperative analgesia,and review the literature on extradural abscess complicatingextradural catheterization, including a discussion on patho-genesis,clinical presentation, diagnosis and management. There havenow been 16 reported cases of extradural catheter-related extraduralabscess. Only one previous case has been in obstetric practice,despite the widespread use of these techniques in this specialty.A disproportionate number of cases have involved thoracic catheters.Duration of catheterization ranged from 40 h to 6 weeks, themajority of catheters being in place for 5 days or less. Thetime from catheter placement to development of symptoms rangedfrom 72 h to 5 months. The causative organism was isolated in11 cases: Staphylococcus aureus was identified in nine (82%)and Staphylococcus epidermidis in two (18%). Outcome was reportedin 15 cases, of which seven (47%) had a full or near full recoveryand eight (53%) had a persistent neurological deficit. One casewas managed successfully without surgery. Fifty percent of allcases have been reported in the past 5 years. With the increasinguse of extradural techniques for anaesthesia and analgesia,this serious complication may be seen more frequently in thefuture.     

FETAL BLOOD FLOW DURING INTRATHECAL ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION

Fetal aortic and umbilical blood flows were studied in 15 mothersbefore and during spinal (intrathecal) anaesthesia for electiveCaesarean section, using a method combining real-time ultrasonographyand a pulsed Doppler technique. Spinal anaesthesia with 0.5%bupivacaine hydrochloride 2.5ml in 8% glucose monohydrate solutionwas administered after preloading with 2 litre of lactated Ringer'ssolution. Simultaneously with the subarachnoid injection, aninfusion i. v. of ephedrine 50 mg in 500 ml normal saline wasinitiated. Maternal heart rate and systolic arterial pressureremained stable during the spinal anaesthesia, but diastolicarterial pressure decreased (P<0.05). Fetal heart rate increased(P<0.05) 30 min after the introduction of the spinal anaesthesia,but blood flows in the fetal descending aorta and umbilicalvein were unaffected. The pulsatility index of the fetal bloodvelocity decreased (P<0.05) both in the fetal aorta and inthe umbilical artery 30 min after induction of the spinal anaesthesia,indicating a possible decrease in the placental vascular resistance.We conclude that, when normotension is maintained in the motherwith a preload infusion and an infusion of ephedrine, spinalanaesthesia for Caesarean section has no harmful effect on thefetal circulation.     

SPREAD OF SPINAL ANAESTHESIA FOR CAESAREAN SECTION IN SINGLETON AND TWIN PREGNANCIES

We have compared the spread of spinal anaesthesia in parturientswith singleton and those with twin pregnancies. Fifty-five unpremedicatedpatients with uncomplicated pregnancy scheduled for Caesareansection were allocated to two groups: group I = 35 singletonmothers; group II = 20 with twin pregnancy. Both groups receivedspinal anaesthesia with hyper baric bupivacaine 10 mg (2 mlof 0.5%). Mean birthweight was 3290 (SD 452) g and 5008 (495)g in groups I and II (combined birth weights), respectively.We found a statistically significant difference in onset andmaximal cephal-ad spread of spinal anaesthesia (group I median15, range 18–14; group II 13, range 16–12). Themechanisms of higher cephalad spread of spinal anaesthesia inparturients may be a decrease in cerebrospinal fluid volumesecondary to shunting of blood from the obstructed inferiorvena cava to the extradural venous plexus and increased nervesensitivity to local anaesthetics because of increased concentrationsof progesterone. The twin pregnancy group had heavier, largeruteri and greater daily production of progesterone. (Br. J.Anaesth. 1993; 70: 639–641)     

EXTRADURAL BUPIVACAINE OR LIGNOCAINE ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION: THE ROLE OF MATERNAL POSTURE

Extradural anaesthesia was induced in 64 patients in eitherthe sitting or the lateral position, for elective Caesareansection with either 0.5% plain bupivacaine or 2% lignocainewith adrenaline 1 in 200 000. Onset was significantly shorterand a significantly greater number of patients were ready forsurgery within 35 min following injection of lignocaine in thelateral position. Hypotension (defined as a 25% or greater reductionin arterial pressure) occurred in 36% of patients. Significantlymore patients who had received the first injection of localanaesthetic agent in the sitting position required ephedrineto correct maternal hypotension. Most frequently, hypotensioncoincided with transfer of patients to theatre and thus wasassociated with movement of the patient in the presence of extensivesympathetic block.     

EXTRADURAL ANALGESIA FOR CAESAREAN SECTION: A COMPARISON WITH GENERAL ANAESTHESIA

Thirty-two patients received lumbar extradural anaesthesia forelective Caesarean section. The results obtained from this serieswere compared with those from a similar (control) group of parturientswho received general anaesthesia. The extradural group (mothersand infants) were metabolically acidaemic relative to control.However, maternal to fetal blood-gas differences were comparablein the two series. Infants sustained respiration more rapidlyafter regional blockade, otherwise the clinical condition ofthe infants was similar with extradural and general anaesthesia.No advantage of conduction over general anaesthesia was evidentfrom this study, with respect to the biochemical status of theinfant at birth.     

MATERNAL AND UMBILICAL CORD PLASMA NORADRENALINE CONCENTRATIONS DURING LABOUR WITH AND WITHOUT SEGMENTAL EXTRADURAL ANALGESIA, AND DURING CAESAREAN SECTION

Serial measurements of maternal and umbilical cord plasma noradernalineconcentrations were obtained in 10 patients undergoing normalvaginal delivery with segmental extradural analgesia, in 10patients undergoing normal vaginal delivery without extraduralanalgesia, and in 12 patients undergoing elective Caesareansection under general anaesthesia. Maternal noradrenaline concentrationsincreased significantly during delivery in all three groups,the peak concentrations occurring at delivery. However, theincrease in the maternal noradrenaline concentration duringdelivery in the extradural group was lower than in the non-extraduralgroup (P<0.05). Umbilical venous and arterial concentrationsof noradernaline were lower after Caesarean section than aftervaginal delivery. However, extradural analgesia did not affectthe fetal noradrenalinc concentrations. Since noradrenalineis probably required for the adaptation of the newborn to extrauterinelife, the unaltered fetal response may be beneficial.     

CAESAREAN SECTION UNDER EXTRADURAL ANALGESIA IN A PATIENT WITH EBSTEIN'S ANOMALY

Ebstein's anomaly is a rare congenital malformation of the tricuspidvalve, often associated with an atrial septal defect. Deathoccurs usually from cardiac arrhythmias. The successful useof a two-catheter technique for elective Caesarean section withextradural analgesia is described and the hazards associatedwith Ebstein's anomaly in pregnancy and anaesthesia are discussed.     

COMPARISON OF EXTRADURAL BUPRENORPHINE AND EXTRADURAL MORPHINE AFTER CAESAREAN SECTION

Fifty-seven women received extradural morphine 3 mg, buprenorphine0.18 mg or buprenorphine 0.09 mg after elective Caesarean sectioncarried out under extradural bupivacaine. Supplementary sublingualbuprenorphine was available on demand. Ten-centimetre visualanalogue pain scores were completed regularly; emesis, pruritisand urinary retention were recorded for 24 h. Patients who receivedbuprenorphine 0.09 mg had more pain, and required more supplementaryanalgesia, than those who received morphine 3 mg. Pain scoresand analgesic requirements after buprenorphine 0.18 mg werenot significantly different from either of the other two groups.Emesis was not significantly different in the three groups.More itching occurred after morphine 3 mg and buprenorphine0.18 mg than after buprenorphine 0.09 mg; pruritis of the face,legs and perineum was more common after morphine than buprenorphine.Twenty-eight percent of patients without a urinary catheterdeveloped retention of urine. Seventy-five to 84% of patientswere satisfied with analgesia during the first day after operation.Analgesia and adverse effects were similar when morphine 3 mgor buprenorphine 0.18 mg was given extradurally after Caesareansection.     

SERIAL PEAK EXPIRATORY FLOW RATES IN MOTHERS DURING CAESAREAN SECTION UNDER EXTRADURAL ANAESTHESIA

Peak expiratory flow rate (PEFR) was measured in 19 mothersduring elective Caesarean section under unsupplemented extraduralanaesthesia. In 18 mothers, serial measurements of peak expiratoryflow rate indicated adequate expiratory reserve and residualabdominal muscle power consistent with an effective cough. Inone mother, with severe respiratory disease, PEFR decreasedto a value indicative of inadequate cough. Data for one othermother who came for emergency Caesarean section after 4 h ofan extradural infusion also indicated an inability to cough.     

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.