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.     

PLASMA LIGNOCAINE CONCENTRATIONS ASSOCIATED WITH EXTRADURAL ANALGESIA IN PATIENTS WITH AND WITHOUT MULTIPLE ORGAN FAILURE

We have measured plasma concentrations of ligno-caine afterthoracic extradural analgesia with continuous infusion of lignocainein eight intensive care patients with chest wall trauma or aftermajor upper abdominal surgery. Four patients developed multipleorgan failure (MOF). Plasma concentrations of lignocaine inarterial blood were measured 4, 8, 24 and 48 h after a continuousinfusion of lignocaine was commenced in the extradural space.Plasma concentrations of lignocaine were greater in all patientswith MOF (range 2.7–5.1 ng ml^–1) than in patientswithout MOF (range 0.8–1.2 fig mh^–1). Because plasmaconcentrations in patients with MOF were within the low toxicrange, extradural infusion of lignocaine should only be consideredin intensive care patients without MOF or when plasma concentrationsof lignocaine are monitored. (Br. J. Anaesth. 1992;69:513–516)     

PHARMACOKINETICS OF PANCURONIUM IN PATIENTS WITH NORMAL AND IMPAIRED RENAL FUNCTION

Plasma concentrations of pancuronium were measured using a fluorimetricmethod in six patients with normal renal function and sevenpatients in chronic renal failure. A two-compartment open modelwas used in the pharmacokinetic analysis of the data. With thismodel, the clearance of pancuronium was found to be reducedsignificantly in the patients with renal failure, and in theseindividuals the volume of the central (distribution) compartmentwas increased significantly. The clinical implications of thesefindings are discussed.     

DELAYED PRESENTATION OF AN EXTRADURAL ABSCESS COMPLICATING THORACIC EXTRADURAL ANALGESIA

Extradural abscess is a rare but recognized complication ofextradural anaesthesia. Previous reports have been associatedwith a short time interval between extradural catheterizationand presentation. We report a patient with rheumatoid arthritis,receiving steroid therapy, in whom an extradural abscess didnot present until 23 days after the insertion of a thoracicextradural catheter to provide postoperative analgesia.     

COMPARISON OF VECURONIUM, ATRACURIUM AND TUBOCURARINE IN NORMAL PATIENTS AND IN PATIENTS WITH NO RENAL FUNCTION

Vecuronium (initial dose 0.1 mg kg^–1; incremental doses0.04 mg kg^–1) was given to 21 normal and 21 anephric patients.There were no gross difference between the two groups in theeffect or in the duration of action of either initial or incrementaldoses, except in two anephric patients who were resistant tothe agent. Reversal with neostigmine was satisfactory. In normalpatients the initial dose of vecuronium was slower in onsetof action than was atracurium 0.5 mg kg^–1 (26 patients):the first two incremental doses of vecuronium were administeredsignificantly earlier than the corresponding increments of atracurium(0.2 mg kg^–1), but the duration of action of incrementsover-all was not greatly different. However, in anephric patients,except in the resistant patients, the behaviour of vecuroniumwas similar to that of atracurium (26 patients). A comparisonwith an initial dose of rubocurarine 0.5mg kg^–1 givento 20 anephric patients and tubocurarine 0.6 mg kg^–1 givento 21 normal and 20 anephric patients showed tubocurarine tobe longer acting and considerably less predictable. This wasparticularly so in the anephric group, in which its action sometimespersisted after neostigmine had been given     

POSTOPERATIVE ANALGESIA AND LUNG FUNCTION: A COMPARISON OF MORPHINE WITH EXTRADURAL BLOCK

Twenty-one patients for vagotomy with gastroenterostomy or pyloroplastywere allocated randomly to postoperative analgesia with eithermorphine by injection or continuous extradural nerve block.In terms of clinical assessment and A–a Po² differencemeasured before and after operation, extradural nerve blockwas found to reduce the degree of postoperative lung dysfunction.It is concluded that the conventional use of narcotics for postoperativeanalgesia increases the risk of lung morbidity. University Department of Anaesthesia (Western Infirmary), 4Lilybank Gardens, Glasgow W.2, Scotland.     

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.     

PHARMACOKINETICS OF ATRACURIUM AND ITS METABOLITES IN PATIENTS WITH NORMAL RENAL FUNCTION, AND IN PATIENTS IN RENAL FAILURE

The plasma pharmacokinetic profiles of atracurium and its derivatives,lafdanosine and monoquaternary alcohol, were studied in sixpatients with renal failure after a bolus dose of atracurium0.3–0.4 mg kg^–1. The pharmacokinetics of the derivativesonly were studied in a group of four normal patients receivingatracurium 0.3 mg kg^–1. Measurements of plasma and urineconcentrations were performed by high pressure liquid chromatography.Pharmacokinetics of atracurium were not significantly differentin the renal failure group when compared with those obtainedin a previous study on six normal patients. Although 2–10%of the dose was recovered in the urine of normal patients asunchanged atracurium, and 3–4% as lafdanosine, renal failureproduced no significant differences in plasma pharmacokinetics,with mean plasma elimination half-lives of 20 min for atracurium,234 min for lafdanosine and 39 min for quaternary alcohol. ^*Southend Hospital, Prittlewell Chase, Westcliff-on-Sea, EssexSSO ORY. Upjohn Limited, Fleming Way, Crawley, West Sussex RH10 2NJ.     

ALTERATIONS OF RESPIRATORY FUNCTION IN PATIENTS WITH SEVERE HEAD INJURIES

Studies were made of the ventilation and arterial acid-basebalance of twenty-three patients who had suffered severe headinjuries. The most frequent findings were an increased minutevolume, an increased production of carbon dioxide, an arterialhypoxaemia, hypocapnia and a raised arterial pH. There was noinstance of respiratory acidosis, and only three patients showednormal ventilation and acid-base values. The increased minutevolume was associated not only with an increased carbon dioxideproduction, but also with a reduced arterial carbon dioxidetension and, therefore, with an increased alveolar ventilation,which may be due to hypoxaemia or to central factors which werenot investigated. The hypoxaemia was associated with increasedalveolar-arterial differences in oxygen tension, and with largevalues for the "physiological deadspace"; these indicated irregularventilation-perfusion relationships. Aspiration and atelectasisat the time of the head injury may initiate the hypoxaemia,the increase in ventilation, and the arterial respiratory alkalosiswhich have been recorded.     

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.     

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.     

ANALGESIA FOLLOWING EXTRADURAL AND I.M. PETHIDINE IN POST-CAESAREAN SECTION PATIENTS

The onset, quality and duration of analgesia following extraduralpethidine 50 mg and i.m. pethidine 100 mg was assessed in 30post-operative patients who had undergone Cae-sarean sectionunder extradural anaesthesia. Saline and pethidine were givenin a randomized, double-blind fashion using simultaneous extraduraland i.m. injections. Extradural pethidine provided superioranalgesia, of quicker onset but similar duration, and both treatmentswere associated with a low incidence of side effects.     

POSTOPERATIVE GLUCOSE TOLERANCE DURING EXTRADURAL ANALGESIA

Thirteen patients undergoing lower abdominal gynaecologicalsurgery were allocated to general anaesthesia (halothane andnitrous oxide) or general anaesthesia plus extradural analgesia(T8-S5) I v. glucose tolerance tests were performed on the daybefore surgery and 8 h after skin incision. All patients havingextradural analgesia (T8) were pain-free following surgery.Extradural analgesia blocked the hyperglycaemic response tosurgery but not the late postoperative cortisol response, althoughvalues were significantly less than in the group receiving generalanaesthesia alone. Impairment of glucose tolerance and of theinsulin response to the glucose load in the period after operationwere not influenced by extradural analgesia and this may haveresulted from insufficient inhibition of the stress-inducedrelease of catecholamines or cortisol, or both, or from blockadeof stimulatory efferent sympathetic pathways to pancreatic islets. ^*Present address. Department of Anesthcsiology, University ofWashington, School of Medicine, ZA-14, Seattle, Washington 98195,U.S A.     

EFFECTS OF SEGMENTAL THORACIC EXTRADURAL ANALGESIA ON SYMPATHETIC BLOCK IN CONSCIOUS DOGS

To test the hypothesis that segmental thoracic extradural blockcauses sympathetic denervation caudally beyond dermatomes renderedanalgesic, we have measured regional skin temperatures in sixconscious dogs after upper thoracic, mid thoracic, and lumbarextradural injection of 0.5% bupivacaine 0.5, 1 and 2 ml cumulatively(total dose: 3.5 ml) given at 45-min intervals. Dogs were studiedat constant ambient and rectal temperatures. Upper thoracicextradural injections resulted in a significant increase inskin temperatures on both the front (+ 1.4 (SEM 0.2) °C)and hind paw (+ 1.4 (0.3) °C), while the area of analgesiawas confined to the upper trunk. With lumbar extradural injection,skin temperatures increased significantly (+2.0 (0.5) °C)on the lower extremities only. Mid thoracic injection significantlyincreased both front (+2.4 (0.9) °C) and hind paw (+2.2(0.6) °C) skin temperatures, but decreased temperatureson the thorax (–0.9 (0.2) °C) and abdomen (–1.0(0.2) °C), reversing the normal temperature gradient alongthe body axis. Irrespective of the injection site, skin temperatureson the trunk failed to increase or even decreased significantly.These data suggest that small doses of local anaesthetics appliedto the extradural space of conscious dogs cause increased lowerextremity skin temperatures caudal to areas unresponsive topinprick stimulation when injected at a high thoracic level,and decreased trunk skin temperature even in analgesic areas,so that skin temperature measurements are unlikely to reflectpurely sympathetic efferent activity on the trunk. Upper thoracicsegmental extradural analgesia induced a decrease in sympathetictone distal to the area of analgesia.     

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.     

POSTOPERATIVE ANALGESIA WITH EXTRADURAL CLONIDINE

The analgesic effect of extradural clonidine was evaluated ina double-blind study. In the recovery room, following orthopaedicor perineal surgery 20 ASA I and II patients were allocatedrandomly to two groups. The extradural clonidine (EC) groupreceived clonidine 2 µg kg^–1 in isotonic salinesolution 15 µg ml^–1. The extradural saline (ES)group received the equivalent volume of plain isotonic salinesolution. Pain was evaluated by a visual analogue scale (VAS)at 15-min intervals for the first 2 h and subsequently at 30-minintervals for the following 4 h. Morphine 5 mg was given s.c.when patients complained of pain after extradural saline orclonidine. In the EC group, the mean (SD) maximum pain reliefwas 68.2 (24.1)% of the initial VAS score, but it was only 14.7(25.2)% in the ES group. The mean duration of analgesia, beforeinjection of morphine, was significantly longer in the EC group(210 (87) min) compared with the ES group (45 (27) min) (P <0.001). Drowsiness and moderate hypotension were observed inthe EC group.     

MICROCOMPUTER-BASED HAEMODYNAMIC MONITORING DURING CONTINUOUS EXTRADURAL ANALGESIA

A system for monitoring, recording and storing arterial pressureand heart rate during continuous extradural analgesia has beendeveloped using an Apple II microcomputer and a Dinamap 1846non-invasive arterial pressure monitor. The administration oflocal anaesthetic (or vasopressor) was recorded using a lightpen. The computer was programmed to recognize this, and to initiateautomatically more frequent measurements of heart rate and arterialpressure. The results of a study using this equipment are reported.The commands for computer control of the Dinamap 1846 are described.     

RESPIRATORY EFFECTS OF EXTRADURAL ANALGESIA AFTER LOWER ABDOMINAL SURGERY

Blood-gas tensions, FRC and volume of trapped gas (V_TG) in thelung were measured in patients on the day before lower abdominalgynaecological surgery, and twice on the day following surgery,before and after establishing lumbar extradural block (EDB)using 0.5% bupivacaine to provide analgesia after operation.FRC and V_TG were measured with the closed-circuit helium-dilutiontechnique. Mean VTG was 175 ml before operation and 275 ml afteroperation. Pa_O2decreased significantly after operation, andthe changes in FRC and V_TG that occurred were related qualitatively.EDB did not significantly alter FRC, V_TG or Pa_O2. Individualchanges in FRC could not be related to changes in V_TG or Pa_O2.Although EDB provided effective analgesia, the variables measureddid not indicate that EDB conferred an immediate respiratoryadvantage.     

URINARY RETENTION DURING I.M. AND EXTRADURAL MORPHINE ANALGESIA

In the postoperative period fifty-six healthy patients undergoingcholecystectomy or operations for duodenal ulcer, received,in a randomized order, i.m , "high-level" or "low-level" extraduralmorphine Thirty-five per cent in the i m. group, 33% in thehigh-level group and 50% in the low-level group suffered urinaryretention, in all cases within the first 24 h The mean cumulativedose of morphine necessary for pain relief was m the same range(13 4–16 5 mg) during the first 2 h of therapy for allgroups, while the amounts after 24 and 48 h were twice to fourtimes with the i m route compared with the extradural route.A peripheral effect of morphine on the urinary bladder is possibleand the mechanism of action is discussed