COMPARATIVE STUDY OF LORAZEPAM AND TRIMEPRAZINE FOR ORAL PREMEDICATION IN PAEDIATRIC ANAESTHESIA

One hundred and ninety-nine children received either lorazepam0.05 mg kg^–1 or trimeprazine 3 mg kg^–1 as oral premedicationin a double-blind trial. Lorazepam proved more palatable andproduced a cheerful demeanour, but possessed no significantadvantages on overall assessment before surgery Following operation,restlessness with vomiting, and evidence of retrograde amnesiaoccurred more frequently with lorazepam. ^*Present addresses: Department of Anaesthesia, New Cross Hospital,Wol-verhampton, West Midlands. Present addresses: Department of Anaesthesia, Victoria Hospital,Kirkcaldy, Fife, Scotland.     

METABOLISM OF SODIUM NITROPRUSSIDE AND CYANIDE IN THE DOG

Blood cyanide (HCN) and thiocyanate (SCN) concentrations weremeasured at intervals in anaesthetized dogs given bolus dosesof sodium nitroprusside (SNP) 1 mg kg^–1 or potassium cyanide1.07 mg kg^–1and in animals infused with SNP 1.5 mg kg^–1for1 h. Cyanide appeared rapidly in the red cells to give peakconcentrations which accounted for more than 90% of the totalblood HCN. A delay between the peak plasma and red cell HCNconcentrations confirmed that some of the SNP was degraded inthe plasma. Comparison of HCN and SCN concentrations with thosemeasured previously in patients receiving an infusion of SNPsuggests that the degradation of SNP and detoxication of HCNmay be more rapid in the dog. The various pathways of HCN detoxicationare discussed in relation to the reduced formation of SCN indogs receiving SNP compared with those receiving KCN. ^*Present addresses: Department of Anaesthesia, Royal Infirmary,Bristol BS2 8HW. Present addresses: Department of Medicine, Charing Cross Hospital,London W6 8RF.     

CLINICAL PHARMACOLOGY OF ATRACURIUM GIVEN IN HIGH DOSE

The safety and efficacy of atracurium 0.8 mg kg^–1 wasdetermined in healthy patients with particular attention tothe speed of onset of blockade, and to changes in haemodynamicvariables. Atracurium 0.8 mg kg^–1 had a shorter onsettime than atracurium 0.5 mg kg^–1, and satisfactory intubatingconditions were achieved earlier. "Priming" produced no significantimprovement in onset time or intubating conditions. Onset timeswere significantly shorter with nitrous oxide-opioid anaesthesiathan following thiopentone alone. Although a 0.8-mg kg^–1bolus resulted in a significant reduction in mean arterial pressureto 75% of control and was associated with a significant increasein plasma histamine concentrations, this response could be preventedby injecting the drug over 75 s. "Priming" or a 30-s injectionproduced no haemodynamic protection. The protection achievedby pretreatment with anti-histamines was incomplete: mean arterialpressure decreased to 83% of control. Presented at the International Anaesthesia Research SocietyCongress, Las Vegas, U.S.A. on March 19, 1986.     

EFFECTS OF DIFFERENT DOSES OF THIOPENTONE ON THE INCREASE IN SERUM MYOGLOBIN INDUCED BY SUXAMETHONIUM IN CHILDREN

We have studied the effects of different doses of thiopentoneon the increase in serum myoglobin after administration of suxamethoniumduring inhalation induction of anaesthesia in children. Forty-threechildren were anaesthetized with halothane and nitrous oxidein oxygen and allocated to four groups. group S received suxamethonium1 mg kg^–1 to facilitate intubation; group ST2 receivedthiopentone 2 mg kg^–1 and group ST4 received thiopentone4 mg kg^–1 before administration of suxamethonium 1 mgkg^–1; group N did not receive thiopentone or suxamethonium.Serum myoglobin and creatine kinase (CK) concentrations weremeasured until 60 min after the injection of suxamethonium.Both myoglobin and CK concentrations increased in the threegroups receiving suxamethonium. There were no significant differencesbetween groups S and ST2, but the myo globin concentration wasless in group ST4 than in groups S and ST2. A significant differencein CK concentration was found only between groups ST2 and ST4at 60min. In group N, both values remained reasonably constant.Thiopentone 4mg kg^–1, but not 2 mg kg^–1, attenuatedthe increase. The results indicate that to prevent a markedelevation in serum myoglobin after administration of suxamethonium,thiopentone 4 mg kg^–1 should be administered. Presented in part at the Annual Meeting of the American Societyof Anesthesiology, October 1989 (Anesthesiology 1989; 71: A1046).     

HAEMODYNAMIC RESPONSES TO ISOFLURANE ANAESTHESIA AND HYPOVOLAEMIA IN THE DOG, AND THEIR MODIFICATION BY PROPRANOLOL

In six dogs chronically implanted with flow and pressure transducers,equipotent inspired concentrations of halothane and isofluranewere determined as the minimum inspired concentration of eachagent which would abolish an individual dog's response to pawclamping. In equipotent concentrations, isoflurane (1.2%, SD0.2%) caused less myocardial depression than halothane (1.0%,SD 0.1%). Dose–response studies were possible up to amean inspired isoflurane concentration of 3.0%, both beforeand after propranolol 0.3 mg kg^-1, i.v. After propranolol, sensitiveindices of myocardial contractility were depressed at all concentrationsof isoflurane, indicating a moderate degree of ß-receptoractivation by isoflurane. The hacmodynamic response to hypovolaemiaduring isoflurane anaesthesia was not modified by propranolol. ^*Present addresses:Department of Anaesthetics, St Vincent'sHospital,Darlinghurst, N.S.W. 2010, Australia. Present addresses:Department of Anaesthesia, University of Bristol,BristolRoyal Infirmary, Bristol BS2 8HW. Present addresses:Department of Anaesthesia, Flinders University,SouthAustralia, Bedford Park, South Australia 5042.     

COMPARISON OF THE CEREBRAL FUNCTION MONITOR AND PLASMA CONCENTRATIONS OF THIOPENTONE AND ALPHAXALONE DURING TOTAL I.V. ANAESTHESIA WITH REPEATED BOLUS DOSES OF THIOPENTONE AND ALTHESIN

Repeated bolus doses of thiopentone or Althesin were administeredto 10 patients every 240 s while cerebral electrical activitywas recorded with the Cerebral Function Monitor (CFM). Peripheralvenous blood samples were collected at 60 and 225s after eachbolus dose for the measurement of plasma concentrations of thedrugs. Significant correlations in the range r = 0.56–0.96(P = 0.02–0.00001) between plasma thiopentone or alphazaloneconcentrations and the upper and lower edges of the CFM tracewere found. For the patiena with relatively poor correlations,better correlations were obtained when 60- and 22 5-s sampleswere analysed separately. ^*Present addresses: Anaesthetic Department, Barnet General Hospital,Barnet, Herts. Present addresses: Institute of Psychiatry, De Crespigny Park,London SE58AF.     

CARDIOVASCULAR EFFECTS OF I.V. INDUCTION IN CHILDREN: COMPARISON BETWEEN PROPOFOL AND THIOPENTONE

We have compared the haemodynamic responses to i.v. propofol2.5 mg kg^-1 with those to thio-pentone 5.0 mg kg^-1 in 41 healthyChinese children at induction of anaesthesia. They were allocatedto four groups according to their age and induction agent received:group 1 <2yr, propofol, n = 9; group II < 2 yr, thiopentone,n = 9; group III 2–12 yr. propofol, n = 12; group IV 2–12yr, thiopentone, n = 11. Anaesthesia was maintained by spontaneousventilation with 70% nitrous oxide and 0.5% halothane in oxygen.Arterial pressure and heart rate were monitored by automaticoscillo -tonometer. Stroke volume was measured by two-dimensionalechocardiography and pulse Dopper. Measurements were made beforeinduction and at 1-min intervals for 5 min after induction.The reduction in mean arterial pressure was significantly greaterafter propofol (28–31%) than after thiopentone (14–21%)(P = 0.001). The reduction in cardiac index (10–15%) afterinduction was not significantly different between the two agents(P = 0.122). Baroref/ex mediated increases in heart rate andsystemic vascular resistance were less after propofol than afterthiopentone. The baroreceptor reflex was more attenuated inchildren aged less than 2 yr than in older children. (Br. J.Anaesth. 1993; 70: 647–653) ^*Present address: Department of Anaesthesia, Addenbrookes Hospital,Hills Road, Cambridge     

CARDIOVASCULAR EFFECTS OF DOXACURIUM, PANCURONIUM AND VECURONIUM IN ANAESTHETIZED PATIENTS PRESENTING FOR CORONARY ARTERY BYPASS SURGERY

The cardiovascular effects of bolus doses of doxacurium 0.037mg kg^–1 were compared with those following equipotentdoses of pancuronium (0.09 mg kg^–1) and vecuronium (0.075mg kg^–1) and with those following high-dose doxacurium(0.075 mg kg^–1), in patients with coronary artery disease.Anaesthetic technique comprised premedication with lorazepam,papaveretum and hyoscine, induction with diazepam, fentanyl,thiopentone, atropine and suxamethonium, and the trachea wasintubated. At least 20 min later, during stable nitrous oxidein oxygen anaesthesia, a single bolus of neuromuscular blockingdrug was administered and the effects measured at 1, 5 and 10min. There was a small decrease in heart rate following doxacurium0.075 mg kg^–1, but no other significant or dose-relatedchanges in mean heart rate, arterial pressure or cardiac indexwith doxacurium. Similar results were found following vecuronium,but the reduction in heart rate was more pronounced. In contrast,significant increases in mean arterial pressure, heart rateand cardiac index occurred after pancuronium. Presented in part at The Anaesthetic Research Society, WarwickMeeting, April 7–8, 1989.     

I.V. LIGNOCAINE FAILS TO ATTENUATE THE CARDIOVASCULAR RESPONSE TO LARYNGOSCOPY AND TRACHEAL INTUBATION

I.v. lignocaine has been used with varying success to attenuatethe cardiovascular responses to laryngoscopy and tracheal intubation.We determined the optimal time of administration in 45 ASA Iand II Chinese patients premedicated with morphine and hyoscine,and anaesthetized with thiopentone and suxamethonium. Patientswere allocated randomly to a control group or three treatmentgroups to receive lignocaine 1.5 mg kg^–1 i.v. 1, 2, or3 min before laryngoscopy. Analysis of variance for measuredand derived cardiovascular variables failed to show any significantdifference between any of the groups. Present addresses: Department of Anaesthesia, Stobhill GeneralHospital, Balornock Road, Glasgow G21 Department of Cardioanaesthesia, Freeman Hospital, High Heaton,Newcastle Upon Tyne NE7 7DN.     

Recovery after propofol infusion anaesthesia in children: comparision with propofol, thiopentone or halothane induction followed by halothane maintenance

We have compared the recovery profiles of 163 healthy Chinesechildren after general anaesthesia for minor surgical procedures.Patients were allocated randomly to receive one of four anaesthetictechniques: propofol infusion for induction and maintenanceusing a pharmacokinetic model-controlled syringe pump set initiallyat a target concentration of 8 µg ml^–1 and thenadjusted according to clinical requirements; propofol 2.5–3.5mg kg^–1, thiopentone 4–5 mg kg^–1 or 2–3%halothane for induction of anaesthesia followed by 1–2% halothane for maintenance of anaesthesia. All oatients breatheda mixture of 70% nitrous oxide in oxygen through a laryngealmask airway and received an appropriate regional anaestheticblock. Recovery was assessed using the time to achieve fullSteward score, open eyes on command, orientation and the timerequired to complete a simple ouzzle. Recovery was slowest withthe propofol infusion (mean 39.8 (SO 12.9) min when eyes openedon command). The recovery times were significantly shorter withthe three other techniques (propofol bolus 21.9 (9.9) min, thiopentone23.4 (11.3) min, halothane 20.1 (8.9) min), and the choice amongthese three methods had no significant influence on the recoveryprofile. (Br. J. Anaesth. 1994; 72: 554–558) ^*Present address: Department of Anaesthesia,Addenbrooke's Hospital,HillsRoad,Cambridge.     

EFFECT OF INDUCTION OF ANAESTHESIA WITH ETOMIDATE ON CORTICOSTEROID SYNTHESIS IN MAN

The effects of a single bolus dose of etomidate 0.3 mg kg^–or thiopentone 5 mg kg^– on the synthesis of corticosteroidhormones and adrenocorticotrophic hormone (ACTH), were comparedfor 24 h in 12 patients, undergoing minor surgery under generalanaesthesia. Following opioid premedication i.m. and generalanaesthesia, plasma cortisoi concentrations decreased transientlywithin the first hour of anaesthesia in all 12 patients. Thesix patients who received etomidate had statistically higherplasma 11-deoxycorticosterone concentrations at 4 and 24 h thanthose who had received thiopentone (P < 0.01). Throughoutthe study, no difference in plasma cortisoi, corticosteroneor ACTH concentrations were found between the two groups. Wehave demonstrated a biochemical effect of a single bolus doseof etomidate consistent with incomplete inhibition of adrenocorticalmitochondrial 11 ß-hydroxylase activity, but no clinicallysignificant adrenocortical suppression. ^*Present address: Department of Anaesthesia, Sheffield UniversityMedical School, Beech Hill Road, Sheffield S10 2RX.     

COMPARISON OF THE EFFECTS OF ORG NC45 AND PANCURONIUM BROMIDE ON HEART RATE AND ARTERIAL PRESSURE IN ANAESTHETIZED MAN

The effects of Org NC 45 and pancuronium bromide on heart rateand arterial pressure were studied in anaesthetized man A bolusof either Org NC450.12mg kg^–1 or pancuronium 0.1 mg kg^–1was administered to lightly anaesthetized unstunulated subjects.Following Org NC 45 heart rate decreased in the majority ofsubjects (mean and SEM 3.78 ± 1.36), whereas after pancuroniumheart rate was increased (mean and SEM 11.91 ± 1 9).The changes in mean arterial pressure observed were minimalThe effect of endotracheal intubation on mean arterial pressurewas then studied. Increase of mean arterial pressure was observedin all subjects. The increase was more marked in those patientswho had received pancuronium and was significantly higher thanm those patients who had received Org NC45 (P<0.01) We concludethat Org NC 45 is devoid of vagal blocking acoon, and that thedifference m response to the stimulus of endotracheal intubationis a result of the different effects exerted on the sympatheticnervous system by Org NC 45 and pancuronium. ^*Present addresses: Department of Anaesthetics, Kingston Hospital,Kingston upon Thames, Surrey. Present addresses: Department of Anaesthetics, Royal HampshireCounty Hospital, Winchester, Hants.     

DANGERS OF ANAESTHESIA IN MUNCHAUSEN'S SYNDROME

Patients with Munchausen's syndrome often undergo multiple surgicaloperations under general anaesthesia. They tend to have multipleexposures to routinely used anaesthetic agents. A patient withMunchausen's syndrome who developed an anaphylactoid reactionto thiopentone is described and the importance of obtainingprevious case notes is stressed. ^*Present addresses: Department of Anaesthesia, South ClevelandHospital, Marton Road, Middlesbrough, Cleveland TS3 4BW. Department of Anaesthesia, Edinburgh Royal Infirmary, EdinburghEH3 9YW.     

GLYCOPYRRONIUM REQUIREMENTS FOR ANTAGONISM OF THE MUSCARINIC SIDE EFFECTS OF EDROPHONIUM

We have compared, in 60 adult patients, the cardiovascular effectsof glycopyrronium 5 µg kg^–1 and 10 µg kg^–1given either simultaneously or 1 min before edrophonium 1 µgkg^–1. Significant differences between the four groupswere detected (P < 0.001). Both groups receiving 10 µgkg^–1 showed increases in heart rate of up to 30 beat min-1(95% confidence limits 28–32 beat min-1). Use of glycopyrronium5 µg kg^–1 provided greater cardiovascular stabilityand, given 1 min before the edrophonium, was sufficient to minimizeearly, edrophonium-induced bradycardias. This low dose of glycoprroniumprovided good control of oropharyngeal secretions. ^*Present address: Respiratory Unit, The Hospital for Sick Children,Great Ormond Street, London W. 1. Presented in part at the June 1987 meeting of the AnaestheticResearch Society.     

AN EVALUATION OF PRIMING WITH VECURONIUM

Priming with vecuronium was evaluated in three groups of patients.Group 1 (n=10) received tubocurarine 0.05 mg kg^–1, group2 (n=19) received physiological saline and group 3 (n = 21)received vecuronium 0.012 mg kg^–1. After 4 min maximuminspiratory pressure was measured. Anaesthesia was induced withthiopentone 6–8 mg kg^–1 and controlled ventilationwith nitrous oxide and oxygen via a face mask instituted. Theulnar nerve was stimulated at the wrist. At 5 min group 1 patientsreceived suxamethonium 1.5 mg kg^–1, group 2 received vecuronium0.072 mg kg^–1, and group 3 received vecuronium 0.060 mgkg^–1. Intubation was accomplished at 6.5 min in all patientsin group 1, 89% in group 2 and 90% in group 3. Patients in group1had no twitch response to stimulation at the time of intubation.Mean T4: T1 ratios at 6.5 min were 0.82 in group 2 and 0.61in group 3 (P < 0.05). Intubatingn conditions were excellentin all group 1 patients, and in 53% and 67% of groups 2 and3, respectively. Two patients in group 3 did not tolerate thepriming dose and many had subjective complaints. Four group3 patients could not sustain head lift and five showed decreasedinspiratory pressure. Priming did not improve intubating conditionswhen compared with a single bolus technique and was not welltolerated. Presented in part at the annual meeting of the American Societyof Anesthesiologists, San Francisco, California, October 1985.     

REPAIR OF TRAUMATIC TRANSECTION OF THE THORACIC AORTA: ESMOLOL FOR INTRAOPERATIVE CONTROL OF ARTERIAL PRESSURE

We report the intraoperative use of esmolol for control of arterialpressure during repair of a traumatic transection of the descendingthoracic aorta. A mean infusion rate of esmolol 50.5 µgkg^–1 min^–1 resulted in a decrease in mean arterialpressure to 63 mm Hg and heart rate to 99 beat min^–1 andwas associated with excellent surgical conditions. The infusionrate of esmolol was titrated easily against mean arterial pressure,which increased rapidly on discontinuing its infusion. Controlof arterial pressure with esmolol was comparable to that achievedwith sodium nitroprusside, but without the reflex tachycardiaor decrease in ?aOl associated with the latter agent. ^*Present addresses: Department of Anaesthesia, St Helier Hospital,Wrythe Lane, Carshalton, Surrey SM5 1AA. Department of Anaesthetics, Charing Cross Hospital, Fulham PalaceRoad, London W6 8RF.     

HISTAMINE RELEASE DURING THE ADMINISTRATION OF ATRACURIUM OR VECURONIUM IN CHILDREN

The histamine releasing potential of equivalent bolus dosesof atracurium 0.6 mg kg^–1 or vecuronium 0.12 mg kg^–1was evaluated in 20 children anaesthetized with halothane. Bloodsamples were obtained before, and at 2 and 5 min after the administrationof the neuromuscular blocker. The twitch response to 0.15Hzwas also evaluated. None of the 10 patients receiving vecuroniumhad a significant increase in plasma histamine concentration.In two of the 10 children receiving atracurium, the plasma histamineconcentration increased markedly, but without any apparent clinicalmanifestations. Recovery of neuromuscular function (to 95% twitchheight) after vecuronium 0.12 mg kg^–1 was faster thanafter atracurium 0.6 mg kg^–1 (P < 0.02). ^*Present address: Department of Anesthesia and Critical Care,University of Chicago, Chicago, II, U.S.A.     

Mivacurium in the myasthenic patient

We have used mivacurium in four myasthenic patients presentingfor thymectomy. Supramaximal single twitch stimulation was appliedto the ulnar nerve at the wrist and the force of contractionof the adductor pollicis was measured. After an initial bolusdose of 30 µg kg^–1 (approximately one-fifth of thenormal intubating dose), we observed a mean 37.5 (SEM 5.6)%reduction in evoked twitch tension. Neuromuscular block wasincreased with incremental doses and maintained with repeatbolus doses of 15 µg kg^–1 at 25% recovery. The intervalbetween maintenance bolus doses remained constant (mean 5.9(0.7) min). Spontaneous offset was rapid with a mean recoveryindex (T25-T75) of 11.9 (2.1) min. Provided anticholinesterasetherapy is withheld in the immediate preoperative period, mivacuriumwould appear to be a safe and appropriate neuromuscular blockerin this variably sensitive group of patients. The cumulativedose required to establish full neuromuscular block varied between60 and 90 µg kg^–1 A maintenance infusion, commencingat 3 µg kg^–1 min^–1 is recommended, guidedby neuromuscular monitoring. Present address: Department of Anaesthesia, Chase Farm Hospital,The Ridgeway, Eafield, Middlesex EN2 8JL Present address: Department of Anaesthesia, St Mary's Hospital,London Present address: Department of Anaesthesia, Queen ElizabethHospital, Birmingham     

HEART RATE AND ARTERIAL BLOOD PRESSURE DURING DIFFERENT FORMS OF INDUCTION OF ANAESTHESIA IN PATIENTS WITH MITRAL STENOSIS AND CONSTRICTIVE PERICARDITIS

Twenty-four patients about to undergo surgery for mitral stenosisor constxictive pericarditis were studied by recording intra-arterialblood pressure and heart rate continuously during the inductionperiod. In two groups of patients, narcosis was induced withthiopentone or hexobarbitone. In the third group, inductiontook place with nitrous oxide. The investigation shows that:(1) A significant increase in blood pressure occurred duringintubation in all three groups, and was most marked in the thiopentonegroup. The blood pressure returned to the initial values inthe thiopentone and nitrous oxide groups. Pronounced hypotensionappeared in the hexobarbitone group. (2) A significant increasein heart rate during intubation occurred only in the barbiturategroups. Bradycardia appeared in the hexobarbitone group. ^*Present addresses; Anaesthesia Department, East Hospital, Universityof Gothenburg, Sweden. Present addresses; Anaesthesia Department, County Hospital,Skellefteft, Sweden.     

HAEMODYNAMIC RESPONSES TO ENFLURANE ANAESTHESIA AND HYPOVOLAEMIA IN THE DOG, AND THEIR MODIFICATION BY PROPRANOLOL

The haemodynamic responses to minumum equipotent concentrationsof halothane and enflurance were compared in seven dogs. Thehaemodynamic responses to increasing concentrations of enflurane,and to induced hypovolaemia during enflurane anaesthesia, werestudied in the same dogs, both before and after administrationof propranolol 0.3 mg kg^-1 i.v. In equipotent concentrations,enflurane caused marginally greater impairment of left ventricularfunction than halothane, and caused a dose-dependent reductionof arterial pressure, cardiac output and myocardial contractility.Following administration of propranolol, these haemodynamiceffects of enflurane were marked, and withdrawal of 20% of estimatedblood volume was tolerated poorly. ^*Present addresses :Department of Anaesthetics, St Vincent'sHospital,Darlinghurst, N.S.W. 2010, Australia. Present addresses :Department of Anaesthesia, University ofBristol,Royal Infirmary, Bristol BS2 8HW. Present addresses :Department of Anesthesiology, Universityof California,San Francisco Medical Center, San Francisco, U.S.A. Present addresses :Department of Anaesthesia, Flinders Universityof South Australia, Bedford Park, South Australia 5042.