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.     

BUPIVACAINE IN PARACERVICAL BLOCK--PLASMA LEVELS AND CHANGES IN MATERNAL AND FOETAL ACID-BASE BALANCE

Bupivacaine without adrenaline (20 ml of 0.5 per cent solution)was used for paracervical block in 11 normal parturients inwhom there were no signs of foetal asphyxia. Maternal and foetalplasma concentrations of bupivacaine were determined by gaschromatography from serial venous samples. The intrauterineacid-base balance of the child was observed before and afterblock from blood samples taken by Saling's technique. The maternalplasma concentrations remained below 0.7 µg/ml (median).At the time of birth the bupivacaine concentration in maternalplasma was in all cases higher than that in umbilical vein blood.After block there were no appreciable changes in the foetalacid-base balance.     

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 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.     

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.     

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.     

A COMPARISON OF POSTOPERATIVE ACID-BASE EQUILIBRIUM AND RESPIRATORY ADEQUACY AFTER TWO TYPES OF NEUROLEPTANALGESIA

Two different types of neuroleptanalgesia supplemented withnitrous oxide and oxygen, NLA I (haloperidol and phenoperidine)and NLA II (dehydrobenzperidol and fentanyl), were given totwenty-seven and thirty-six patients, respectively. The comparisonof respiratory adequacy shows that, after NLA I, there was respiratoryacidosis and slight metabolic acidosis, most prominent 30 minutesafter anaesthesia with a tendency to return to normal duringthe three-hour follow-up period. With NLA II there were no signsof respiratory depression. Base excess and pH also remainedwell within the physiological range.