EFFECT OF ADRENALINE ON PLASMA CONCENTRATIONS OF BUPIVACAINE FOLLOWING LOWER LIMB NERVE BLOCK

Twenty-two patients undergoing total knee arthroplasty receivedcombined sciatic plus femoral "3 in 1" blocks as adjuncts togeneral anaesthesia. Eleven patients received 0.375% bupivacaine45 ml (168.75 mg) with adrenaline 1 in 200000 and the remaining11 received plain solution according to a previously prepared,randomized list. The mean maximum plasma bupivacaine concentrationwas significantly greater with plain solution than when adrenalinewas added (1.66 µg ml^–1 compared with 0.98 µgml^–1) (P < 0.05). Bupivacaine concentrations were greaterat all times in the plain group compared with the group receivingadrenaline. These differences were statistically significantat 10, 15 and 20 min (P < 0.05). The greatest peak concentrationrecorded was 3.13 µg ml^–1 in one patient receivingplain bupivacaine. No patient developed signs of systemic toxiceffects. Peak plasma concentrations were related inversely tobody weight in patients receiving solution containing adrenaline(P < 0.005), but no relationship existed in patients whoreceived plain solution.     

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 ADRENALINE ON PLASMA CONCENTRATIONS OF BUPIVACAINE FOLLOWING INTRA-ARTICULAR INJECTION OF BUPIVACAINE FOR KNEE ARTHROSCOPY

We administered 0.5% bupivacaine 30 ml either with or withoutadrenaline 5 ug ml^–1 randomly to 16 healthy outpatients,to determine the efficacy of local and intra-articular localanaesthesia for knee arthroscopy and whether or not adrenalineshould be added to intra-articular bupivacaine. Bupivacaineconcentrations were measured in plasma obtained 15, 30, 45 and60 min after intra-articular injection. Patients receiving bupivacainewith adrenaline had significantly smaller plasma concentrationsof bupivacaine at all times than did patients receiving plainbupivacaine. The maximal concentrations of bupivacaine in theplain group (median 515 ng ml^–1, range 46–875 ngml^–1) were greater than those in the adrenaline group(median 33 ng ml^–1, range 7–125 ng ml^–1) (P= 0.001). All patients found the anaesthetic satisfactory. Weconclude that intra-articular/local anaesthesia is satisfactoryfor outpatient arthroscopic surgery, and that adrenaline shouldprobably be added to bupivacaine before intra-articular injection.     

Postoperative extradural analgesia in children: comparison of morphine with fentanyl

We have compared the efficacy and side effects of extraduralmorphine with extradural fentanyl for postoperative pain relief.Thirty children (ages 1–16 yr) were allocated randomlyto receive, after extradural administration of 0.5% bupivacaine0.75 ml kg^–1 and before surgical incision, extreduralmorphine 0.75 µg kg^–1 (group M), with an additionaldose administered 24 h later or extradural fentanyl 2 µgkg^–1 (group F) followed by a continuous extradural infusion(during 48 h). There was no major complication (respiratorydepression). Pain scores were satisfactory in both groups for48 h. Ventilatory frequency was greater in group M 20, 21, 22,23 and 25 h after the beginning of analgesia (P < 0.05).Pruritus, nausea and vomiting were less common with extraduralfentanyl (20% vs 53%, P < 0.05 and 0% vs 33%, P < 0.05)than with morphine. Urinary retention occurred with equal frequency(25%) in the two groups. After a bolus of 2 µg kg^–1,continuous extradural infusion of fentanyl 5 µg kg^–1day^–1 provided analgesia comparable to that from a dailybolus of extradural morphine 0.75 mg kg^–1 and producedfewer side effects.      

FUNCTIONAL AND METABOLIC EFFECTS OF BUPIVACAINE AND LIGNOCAINE IN THE RAT HEART-LUNG PREPARATION

We have examined the effects of bupivacaine and lignocaine onmyocardial metabolism in the rat isolated heart-lung preparation.Bupivacaine 1, 5 or 25 µg ml^–1 or lignocaine 4,20 or 100 µg ml^–1 was administered 5 min after thestart of perfusion. Both bupivacaine 25 µg ml^–1and lignocaine 100 µg ml^–1 reduced heart rate significantly.Bupivacaine 25 µg ml^–1 was associated with a higherincidence of arrhythmias than the other groups. Three heartsin the bupivacaine 25 µg ml^–1 group (n = 8) andtwo hearts in the lignocaine 100 µg ml^–1 group (n= 8) failed (zero cardiac output) at the end of the experiment.Although there were no significant differences in myocardiallactate and glycogen concentrations between groups, ATP contentin the bupivacaine 25 µg ml^–1 and lignocaine 100µg ml^–1 groups was significantly less than thatin the control group. The results suggest that myocardial depressionand subsequent metabolic deterioration occurred with both thehigh doses of local anaesthetics; these findings do not accountfor the apparent increased cardiotoxicity of bupivacaine.     

Influence of acute normovolaemic haemodilution on the dose-response relationship, time-course of action and pharmacokinetics of rocuronium bromide

Background. Acute normovolaemic haemodilution (ANH) is an effectivestrategy for avoiding or reducing allogeneic blood transfusion.We aimed to study its effect on the pharmacological profileof rocuronium. Methods. In two study centres, 28 patients undergoing majorsurgery with ANH were matched with 28 control patients. In thedose–response groups, using the mechanomyograph, neuromuscularblock of six consecutive incremental doses of rocuronium 50µg kg^–1, followed by 300 µg kg^–1, wasevaluated. In the pharmacokinetics groups, serial arterial bloodsamples were withdrawn for rocuronium assay after a single doseof rocuronium 600 µg kg^–1. Results. ANH resulted in a shift to the left of rocuronium dose–responsecurve. Rocuronium effective dose₉₅ (ED₉₅) was 26% lower (P<0.05)in the ANH group [283.4 (92.0) µg kg^–1] comparedwith the control group [383.5 (127.3) µg kg^–1].Times from administration of last incremental dose until 25%of first response of train-of-four (TOF) recovery (Dur₂₅) and0.8 TOF ratio recovery (Dur_0.8) were 28% longer in the ANH group[39.9 (8.4), 66.7 (14.2) min] compared with the control group[31.1 (6.6), 52.1 (15.8) min] (P<0.01, P<0.05), respectively.Volume of distribution was higher (P<0.01), central clearancewas lower (P<0.05) and terminal elimination half-life waslonger (P<0.0001) in the ANH group [234.97 (47.11) ml kg^–1,4.70 (0.94) ml kg^–1 min^–1, 77.29 (12.25) min] comparedwith the control group [181.22 (35.73) ml kg^–1, 5.71 (1.29)ml kg^–1 min^–1, 56.86 (10.05) min, respectively]. Conclusion. ANH resulted in prolongation of rocuronium time-courseof action, thus careful monitoring of neuromuscular block isrecommended in patients who undergo ANH.     

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.     

Pharmacokinetics of levobupivacaine 0.25% following caudal administration in children under 2 years of age

Background. Levobupivacaine, the S(–)enantiomer of racemicbupivacaine is less cardiotoxic than racemic bupivacaine andthe R(+)enantiomer dexbupivacaine, while retaining similar localanaesthetic properties and potency to racemic bupivacaine. Thepharmacokinetic profiles of the two bupivacaine enantiomersdiffers and that of racemic bupivacaine may be age dependent.We examined the pharmacokinetics of levobupivacaine after itssingle shot caudal epidural administration in children. Methods. An open-label phase 2 study was undertaken to examinethe pharmacokinetics of levobupivacaine 0.25% 2 mg kg^–1in 49 children aged less than 2 yr, after single shot caudalepidural administration. Plasma concentrations were determinedat intervals up to 60 min after caudal injection. Results. Time to peak plasma concentration (T_max) ranged between5 and 60 min (median 30 min) and was reached later in childrenaged less than 3 months (P<0.005). Peak plasma concentration(C_max) ranged between 0.41 and 2.12 µg ml^–1 (median0.80, mean (SD) 0.91 (0.40) µg ml^–1). Conclusion. After the caudal epidural administration of levobupivacaine2 mg kg^–1 in children less than 2 yr of age, C_max waswithin the accepted safe range for racemic bupivacaine. T_maxvaried and occurred later in some children, particularly thoseaged less than 3 months. Sampling in future pharmacokineticstudies in this age group should extend beyond 60 min. Br J Anaesth 2004; 92: 218–22     

PLASMA CONCENTRATIONS OF BUPIVACAINE AND TWO OF ITS METABOLITES DURING CONTINUOUS INTERSCALENE BRACHIAL PLEXUS BLOCK

An interscalene brachial plexus block was performed via a catheterwith 20–28 ml of 0.75% bupivacaine plus adrenaline forsurgery of the shoulder region in 12 patients. Constant infusionof 0.25% bupivacaine 0.25 mg kg^–1 h^–1 was continuedfor 24 h. During surgery light general anaesthesia, withoutanalgesics, was maintained. Plasma concentrations of total andunbound (free fraction) bupivacaine, desbutylbupivacaine (DBB),4-hydroxybupivacaine (4-OHB) and alpha₁-acid glycoprotein (AAG)were measured at predetermined intervals during the continuousblock. The greatest mean plasma concentrations of bupivacainewere measured at 30 min (1.63 (SD 0.55) µg ml^–1)and 60 min (1.38 (0.48) µg ml^–1). There was a smallbut statistically significant increase in the plasma concentrationof bupivacaine between 12 and 24 h of infusion. The mean unboundconcentration of bupivacaine in plasma decreased from 0.044(0.015) µg ml^–1 (3.6 (1.1)% of total bupivacaineconcentration) at 3 h to 0.023 (0.011) µg ml^–1 (2.1(1.0)%) at 24 h. The AAG concentration in plasma increased by38% in 24 h. The metabolites DBB and 4-OHB were detectable inplasma from 30 min, with a gradual increase during infusion.At 24 h the mean concentrations of DBB and 4-OHB were 0.33 (0.22)µg ml^–1 and 0. 13 (0.04) µg ml^–1, respectively.There were no toxic reactions during the blocks.     

Effect of intravenous vasopressor on spread of spinal anaesthesia and fetal acid-base equilibrium

Background: We previously found rostral spread of spinal plain levobupivacaineto be less with prophylactic i.v. phenylephrine than with ephedrineduring Caesarean delivery. This study investigated whether rostralspread of spinal hyperbaric bupivacaine is also less with phenylephrinethan with ephedrine. Methods: The study was randomized and double blind. It compared phenylephrine100 µg ml^–1 (phenylephrine group, n = 27), and ephedrine4.5 mg ml^–1 (ephedrine group, n = 27), given by infusionduring spinal anaesthesia for Caesarean delivery. Block heightwas assessed to cold and light touch sensation at 15, 30, 60,and 90-min after the spinal injection of 2.8 ml of hyperbaric0.5% w/v bupivacaine, combined with 0.4 ml diamorphine (1 mgml^–1). Umbilical blood gas values were monitored duringthe study. Results: Block height was similar for both groups at all of the assessmenttimes. Umbilical artery pH was higher with phenylephrine [median7.32 (IQR 7.28–7.34)] than with ephedrine [7.20 (7.10–7.28)](P < 0.0001). There was a strong negative correlation betweenumbilical artery pH and spinal-delivery interval, but only withephedrine: phenylephrine group, r² = 0.09 (P = 0.17), and ephedrinegroup, r² = 0.53 (P < 0.0001). Five-minute Apgar scores werehigher with phenylephrine [10 (9–10)] than ephedrine [9(9–9)] (P = 0.009). Conclusions: In contrast to its effect on spinal plain levobupivacaine, wedid not find rostral spread of spinal hyperbaric bupivacaineto be less with prophylactic phenylephrine than with ephedrine.We observed an unexpectedly high incidence of fetal acidosiswith ephedrine and found evidence that longer spinal-deliveryintervals increase the risk of fetal acidosis developing withephedrine, but not phenylephrine.     

CLINICAL AND HAEMODYNAMIC EFFECTS OF MILRINONE IN THE TREATMENT OF LOW CARDIAC OUTPUT AFTER CARDIAC SURGERY

We have studied the haemodynamic effects of i.v. milrinone.a newphosphodiesterase inhibitor, in patients with low cardiacoutput after cardiac surgery. Thirty-five patients with a cardiacindex (Cl) < 2.5 litre min^–1 m^–2 and a pulmonarycapillary wedge pressure (PCWP) > 8 mm Hg were given a loadingdose of milrinone 50 µg kg^–1 followed by an infusionat one of three rates: 0.375 fig kg^–1 min^–1, 0.5fig kg^–1 min^–1 or 0.75 µg kg^–1 min^–1for 12 h. After 1 h there were increases in Cl (35%) (P<0.001), heart rate (13%) (P< 0.01) and stroke volume index(19%) (P< 0.005). There were decreases in mean arterial pressure(12%) (P< 0.01), systemic vascular resistance (35%) (P<0.001) and PCWP (24%) (P< 0.05). Pulmonary vascular resistancewas unchanged or reduced and left ventricular stroke work indexwas unchanged or increased. The haemodynamic improvements weresustained throughout the infusion period. Milrinone was toleratedwell: three patients developed tachycardia > 125 beat min^–1,one patient developed atrial fibrillation and one patient hada short run of atrial bigemini. We conclude that milrinone isa useful agent in the treatment of patients with a reduced cardiacoutput after cardiac surgery.     

Comparison of propofol/remifentanil and sevoflurane/remifentanil for maintenance of anaesthesia for elective intracranial surgery

Background. Propofol and sevoflurane are suitable agents formaintenance of anaesthesia during neurosurgical procedures.We have prospectively compared these agents in combination withthe short-acting opioid, remifentanil. Methods. Fifty unpremedicated patients undergoing elective craniotomyreceived remifentanil 1 µg kg^–1 followed by an infusioncommencing at 0.5 µg kg^–1 min^–1 reducing to0.25 µg kg^–1 min^–1 after craniotomy. Anaesthesiawas induced with propofol, and maintained with either a target-controlledinfusion of propofol, minimum target 2 µg ml^–1 orsevoflurane, initial concentration 2%_ET. Episodes of mean arterialpressure (MAP) more than 100 mm Hg or less than 60 mm Hg formore than 1 min were defined as hypertensive or hypotensiveevents, respectively. A surgical assessment of operating conditionsand times to spontaneous respiration, extubation, obey commandsand eye opening were recorded. Drug acquisition costs were calculated. Results. Twenty-four and twenty-six patients were assigned topropofol (Group P) and sevoflurane anaesthesia (Group S), respectively.The number of hypertensive events was comparable, whilst morehypotensive events were observed in Group S than in Group P(P=0.053, chi-squared test). As rescue therapy, more labetolol[45 (33) vs 76 (58) mg, P=0.073] and ephedrine [4.80 (2.21)vs 9.78 (5.59) mg, P=0.020] were used in Group S. Between groupdifferences in recovery times were small and clinically unimportant.The combined hourly acquisition costs of hypnotic, analgesic,and vasoactive drugs appeared to be lower in patients maintainedwith sevoflurane than with propofol. Conclusion. Propofol/remifentanil and sevoflurane/remifentanilboth provided satisfactory anaesthesia for intracranial surgery.     

Co-administration of pethidine and clonidine: a spinal anaesthetic technique for total hip replacement

Co-administration of pethidine 0.75 mg kg^–1 and clonidine75 µg intrathecally provided good intra-operative anaesthesiafor total hip replacement, similar to that obtained using 0.5%isobaric bupi-vacaine. Sensory and motor block were of shorterduration than that after 0.5% isobaric bupivacaine and 0.5%isobaric bupivacaine with morphine 0.5 mg (P<0.001 sensoryblock, P<0.001 motor block). Postoperative morphine consumption,measured using a patient-controlled system, was similar to thatin patients in the bupivacaine only group (pethidine-clonidine:median 39mg/24h; bupivacaine: median 34 mg/24 h) but greaterthan that in the bupivacaine-morphine group (median 8 mg/24h) (P<0.001). Visual analogue pain scores after operationwere similar to those with bupivacaine alone at all but oneof the recording times but were greater than those in patientswho received bupivacaine and morphine at 4, 6 and 10 h afteroperation (P<0.001, P<0.04, P<0.02). The combinationdid not offer any major advantage over conventional agents.     

NON-INVASIVE MEASUREMENT OF CARDIAC OUTPUT DURING INDUCTION OF ANAESTHESIA AND TRACHEAL INTUBATION: THIOPENTONE AND PROPOFOL COMPARED

We have investigated the haemodynamic changes in response toinduction of anaesthesia and tracheal intubation in patientswho received either thiopentone 5 mg kg^–1 or propofol3 mg kg^–1 followed by atracurium 0.5 mg kg^–1 andfentanyl 1.5 µg kg^–1. Anaesthesia was maintainedwith 0.6% enflurane and 50% nitrous oxide in oxygen with assistedventilation. Cardiac output and heart rate (HR) were monitoredcontinuously with a transthoracic impedence monitor. Mean HRdid not change after induction in each group, but increasedafter tracheal intubation in both groups (P < 0.01). Meancardiac index (CI) decreased after induction (P < 0.05) anddecreased further after tracheal intubation in both groups (P< 0.05). There was no difference between the two groups withrespect to changes in CI and HR. Mean arterial pressure (MAP)and systemic vascular resistance (SVR) did not change significantlyafter induction in the thiopentone group. Both variables increasedfrom preinduction values 1 min after tracheal intubation (P< 0.001). In contrast, both MAP and SVR decreased after inductionin the propofol group (P < 0.001) and did not differ frompreinduction values 1 min after tracheal intubation. MAP andSVR were greater in the thiopentone group compared with thepropofol group after induction and tracheal intubation (P <0.01).     

Epidural analgesia with 0.15% ropivacaine plus sufentanil 0.5 microgram ml-1 versus 0.10% bupivacaine plus sufentanil 0.5 microgram ml-1: a double-blind comparison during labour

Background. Ropivacaine has been claimed to produce less motorblock than bupivacaine during epidural analgesia. However, thisadvantage has not been clearly confirmed in obstetric studiesusing low analgesic concentrations in a ratio close to thatsuggested to be equianalgesic. Methods. This double-blind, randomized, prospective study wasperformed in 140 parturients who requested epidural analgesia.After a lumbar epidural catheter had been placed, patients receivedeither 0.10% bupivacaine plus sufentanil 0.5 µg ml^–1or 0.15% ropivacaine plus sufentanil 0.5 µg ml^–1followed by a continuous infusion. Additional boluses were usedfor inadequate levels of analgesia. Visual analogue pain scores,motor block, level of sensory block, supplementary boluses andmain characteristics of labour were recorded. Results. No differences were observed between the two groupsfor pain scores, total volume of anaesthetic solution used [59(23) and 57 (24) ml in the bupivacaine and ropivacaine groupsrespectively], duration of labour, mode of delivery, side-effectsor satisfaction score. The incidence of motor block was notstatistically different between the groups (54 and 69% in thebupivacaine and ropivacaine groups respectively, P=0.07). However,when motor block occurred, survival analysis showed that itoccurred sooner in the course of labour with ropivacaine comparedwith bupivacaine (log rank test, P=0.012). Conclusion. Combined with sufentanil 0.5 µg ml^–1,0.10% bupivacaine and 0.15% ropivacaine produce effective andequivalent analgesia during labour, with similar incidencesof motor block. Br J Anaesth 2002; 88: 809–13     

Pharmacokinetics of remifentanil and its major metabolite, remifentanil acid, in ICU patients with renal impairment

Background. The pharmacokinetics of remifentanil, an opioidanalgesic metabolized by non-specific esterases, and its principalmetabolite, remifentanil acid (RA), which is excreted via thekidneys, were assessed as part of an open-label safety studyin intensive care unit (ICU) patients with varying degrees ofrenal impairment. Methods. Forty adult ICU patients with normal/mildly impairedrenal function (creatinine clearance [CL_cr] 62.9 (SD) 14.5 mlmin^–1; n=10) or moderate/severe renal impairment (CL_cr14.7 (15.7) ml min^–1; n=30) were included. Remifentanilwas infused for up to 72 h, at a starting rate of 6–9µg kg^–1 h^–1 titrated to achieve a target sedationlevel, with additional propofol (0.5 mg kg^–1 h^–1)if required. Intensive arterial sampling was performed for upto 72 h after infusion. Pharmacokinetic parameters obtainedby simultaneous modelling of remifentanil and RA data were statisticallycompared between the two groups. Results. Remifentanil pharmacokinetics were not significantlyaffected by renal status. RA clearance in the moderate/severegroup was reduced to about 25% that of the normal/mild group(41 (29) vs 176 (49) ml kg^–1 h^–1, P<0.0001).Metabolic ratio, a predictor of the ratio of RA to remifentanilconcentrations at steady state, was approximately eight-foldhigher in the moderate/severe group relative to the normal/mildgroup (116 (110) vs 15 (4), P<0.0001). Maximum RA levelsapproached 700 ng ml^–1 in the moderate/severe group. Conclusions. Although RA accumulates in patients with moderate/severerenal impairment, pharmacokinetic modelling predicts that RAconcentrations during a 9 µg kg^–1 h^–1 remifentanilinfusion for up to 15 days would not exceed those reported inthe present study, for which no associated prolongation of µ-opioideffects was observed. Br J Anaesth 2004; 92: 493–503     

FENTANYL INHIBITS THE UPTAKE OF [3H]NORADRENALINE IN CULTURED NEURONAL CELLS

We have examined how fentanyl modulates [³H]noradrenaline uptakein two cultured neuronal cell preparations, the human neuroblastomaSH-SY5Y and the rat phaeochromocytoma PC12. Fentanyl produceda significant, dose-dependent inhibition of [³noradrenalineuptake at concentrations in excess of 0.1 µmol litre^–1(P <0.05) and 0.3 µmol litre^–1 (P < 0.05)for PC12 and SH-SY5Y cells, respectively. However, these valuesexceed the serum concentration of fentanyl required to produceanalgesia. At the maximum concentration examined (100 µmollitre^–1), fentanyl produced 85–95% inhibition ofuptake. This effect was not antagonized by naloxone, implyinga nonopioid mechanism of action. Imipramine 1 µmol litre^–1reduced [³H]noradrenaline uptake by 65–70% but morphine,in contrast to fentanyl, had no effect (P > 0.1). (Br. J.Anaesth. 1993; 71: 540–543)     

Prevention of postoperative nausea and vomiting by continuous infusion of subhypnotic propofol in female patients receiving intravenous patient-controlled analgesia

In this prospective, randomized, double-blind, placebo-controlledstudy, the use of continuous subhypnotic propofol infusion asan antiemetic in fentanyl intravenous patient-controlled analgesia(i.v. PCA) was investigated during the first 24 h after surgery.One hundred female patients, ASA I–II, aged 20–71yr, undergoing major gynaecological or orthopaedic surgery,were included. Either propofol 10 mg or placebo (1 ml of Intralipid)was given and one of the following five regimens was maintainedfor 24 h: propofol 5, 10, 15 or 20 µg kg^–1 min^–1or Intralipid 1 ml h^–1 as a placebo. Fentanyl i.v. PCAwas started in the postanaesthesia care unit for postoperativeanalgesia. Significantly more of the patients given propofol15 and 20 µg kg^–1 min^–1 experienced no nauseaor vomiting compared with those given placebo (65% and 70% versus25%; P<0.05). Patients given propofol 20 µg kg^–1min^–1 reported more sedation than those in the other groups4 h after surgery (P<0.05). Br J Anaesth 2000; 85: 898–900     

METABOLIC CHANGES DURING DOPAMINE INFUSION IN DOGS

The effects were investigated, in 12 dogs, of the infusion ofdopamine 10 or 30 µg kg^–1 min^–1 on circulatingglucose, glycerol, lactate and potassium concentrations. Bothdoses of dopamine produced an initial increase in blood glucoseconcentration (P < 0.05) followed by hypoglycaemia (P<0.05).Lipolysis was stimulated as shown by an increase in plasma glycerolconcentrations with dopamine 10 µg kg^–1 min^–1(P<0.05) and dopamine 30 µg kg^–1 min^–1(P<0.01). Blood lactate concentrations increased slightlyin both groups, but this was significant (P < 0.05) onlyin the dogs infused with dopamine 10 µg kg^–1min^–1.Dopamine had no significant effect on the plasma potassium concentration.     

Oral clonidine vs midazolam in the prevention of sevoflurane-induced agitation in children. a prospective, randomized, controlled trial

Background: This randomized, double-blind study tested the hypothesis that,in comparison with midazolam, premedication with oral clonidinereduces the incidence of emergence agitation in preschool childrenanaesthetized with sevoflurane. Methods: Sixty-eight ASA I–II children undergoing circumcisionwere randomized into three groups to receive different oralpremedication given 30 min before anaesthesia: midazolam 0.5mg kg^–1, clonidine 2 µg kg^–1, and clonidine4 µg kg^–1. Sevoflurane anaesthesia was administeredvia a facemask (O₂/N₂O: 40/60). Analgesia was with penile block(bupivacaine 0.5% 0.3 ml kg^–1) and rectal paracetamol(30 mg kg^–1). During the first postoperative hour, childrenwere evaluated using a modified ‘objective pain scale’. Results: Only the 4 µg kg^–1 dose of clonidine was associatedwith a significant reduction in emergence agitation. Fewer childrenin the clonidine 4 µg kg^–1 group displayed agitation(25%) than in the midazolam group (60%) (P = 0.025). Incidenceof hypotension and bradycardia, time to first micturition andfirst drink did not differ among groups. Conclusions: In comparison with midazolam, clonidine 4 µg kg^–1reduced sevoflurane-induced emergence agitation without increasingpostoperative side-effects.