Tramadol does not modify the Bispectral Index during anaesthesia with sevoflurane and remifentanil

Background. The aim of this study was to investigate the effectsof tramadol administered with ketorolac on the Bispectral Index(BIS) during anaesthesia with sevoflurane and remifentanil. Methods. Forty-six adult patients, ASA I–III, scheduledfor elective minor surgical procedures were studied. Patientswere premedicated with remifentanil infusion 0.4 µg kg^–1min^–1 and anaesthesia was induced 4–5 min laterwith propofol 1.5 mg kg^–1 and maintained with air–oxygen( 0.4), remifentanil 0.1–0.15 µg kg^–1 min^–1 and sevoflurane, adjusted to keep theBIS between 40 and 50. After 20 min of stable anaesthesia, thesubjects were allocated randomly to receive i.v. tramadol 1.5mg kg^–1 and i.v. ketorolac 0.3 mg kg^–1 (tramadolgroup) or saline (control group). BIS values, mean arterialpressure, heart rate and end-tidal carbon dioxide were recordedevery 5 min for 20 min. Results. Mean BIS values after tramadol administration werenot significantly different from those recorded in patientsreceiving saline throughout the period of observation. Therewere no patients who presented explicit recall of events underanaesthesia. No significant changes in mean arterial pressure,heart rate and end-tidal carbon dioxide were noted after tramadolinjection. Conclusion. Tramadol, given with ketorolac to prevent postoperativepain, during anaesthesia maintained with sevoflurane and remifentanilat BIS between 40 and 50, does not modify the BIS value.     

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.     

Early recovery after remifentanil-pronounced compared with propofol-pronounced total intravenous anaesthesia for short painful procedures

Background. We compared recovery from high-dose propofol/low-doseremifentanil (‘propofol-pronounced’) compared withhigh-dose remifentanil/low-dose propofol (‘remifentanil-pronounced’)anaesthesia. Methods. Adult patients having panendoscopy, microlaryngoscopy,or tonsillectomy were randomly assigned to receive either propofol-pronounced(propofol 100 µg kg^–1 min^–1; remifentanil0.15 µg kg^–1 min^–1) or remifentanil-pronounced(propofol 50 µg kg^–1 min^–1; remifentanil 0.45µg kg^–1 min^–1) anaesthesia. In both groups,the procedure was started with remifentanil 0.4 µg kg^–1,propofol 2 mg kg^–1, and mivacurium 0.2 mg kg^–1.Cardiovascular measurements and EEG bispectral index (BIS) wererecorded. To maintain comparable anaesthetic depth, additionalpropofol (0.5 mg kg^–1) was given if BIS values were greaterthan 55 and remifentanil (0.4 µg kg^–1) if heartrate or arterial pressure was greater than 110% of pre-anaestheticvalues. Results. Patient and surgical characteristics, cardiovascularmeasurements, and BIS values were similar in both groups. Therewere no differences in recovery times between the groups (timeto extubation: 12.7 (4.5) vs 12.0 (3.6) min, readiness for transferto the recovery ward: 14.4 (4.4) vs. 13.7 (3.6) min, mean (SD)). Conclusions. In patients having short painful surgery, lesspropofol does not give faster recovery as long as the same anaestheticlevel (as indicated by BIS and clinical signs) is maintainedby more remifentanil. However, recovery times were less variablefollowing remifentanil-pronounced anaesthesia suggesting a morepredictable recovery. Br J Anaesth 2003; 91: 580–2     

Haemodynamic effects of remifentanil in children with and without intravenous atropine. An echocardiographic study

Background. Remifentanil is known to cause bradycardia and hypotension.We aimed to characterize the haemodynamic profile of remifentanilduring sevoflurane anaesthesia in children with or without atropine. Methods. Forty children who required elective surgery receivedinhalational induction of anaesthesia using 8% sevoflurane.They were allocated randomly to receive either atropine, 20µg kg^–1 (atropine group) or Ringer's lactate (controlgroup) after 10 min of steady-state 1 MAC sevoflurane anaesthesia(baseline). Three minutes later (T0), all children receivedremifentanil 1 µg kg^–1 injected over a 60 s period,followed by an infusion of 0.25 µg kg^–1 min^–1for 10 min then 0.5 µg kg^–1 min^–1 for 10 min.Haemodynamic variables and echocardiographic data were determinedat baseline, T0, T5, T10, T15 and T20 min. Results. Remifentanil caused a significant decrease in heartrate compared with the T0 value, which was greater at T20 thanT10 in the two groups: however, the values at T10 and T20 werenot significantly different from baseline in the atropine group.In comparison with T0, there was a significant fall in bloodpressure in the two groups. Remifentanil caused a significantdecrease in the cardiac index with or without atropine. Remifentanildid not cause variation in stroke volume (SV). In both groups,a significant increase in systemic vascular resistance occurredafter administration of remifentanil. Contractility decreasedsignificantly in the two groups, but this decrease remainedmoderate (between –2 and +2 SD). Conclusion. Remifentanil produced a fall in blood pressure andcardiac index, mainly as a result of a fall in heart rate. Althoughatropine was able to reduce the fall in heart rate, it did notcompletely prevent the reduction in cardiac index.     

Comparison of effects of remifentanil and alfentanil on cardiovascular response to tracheal intubation in hypertensive patients

In a randomized double-blind study, we compared the effect ofremifentanil and alfentanil on the cardiovascular response tolaryngoscopy and tracheal intubation in patients on long-termtreatment for hypertension. Forty ASA II–III patientswere allocated to receive (i) remifentanil 0.5 µg kg^–1followed by an infusion of 0.1 µg kg min^–1 or (ii)alfentanil 10 µg kg^–1 followed by an infusion ofsaline; all patients received glycopyrrolate 200 µg beforethe study drug. Anaesthesia was induced with propofol and rocuroniumand maintained with 1% isoflurane and 66% nitrous oxide in oxygen.Laryngoscopy and tracheal intubation were performed after establishmentof neuromuscular block. Arterial pressure and heart rate (HR)were measured non-invasively at 1 min intervals from 3 minbefore induction until 5 min after intubation. Systolic(SAP), diastolic and mean arterial pressure decreased significantlyafter induction in both groups (P<0.05). Maximum increasesin mean SAP after laryngoscopy and intubation were 35 and 41mm Hg in the remifentanil and alfentanil groups, respectively.After intubation, arterial pressure did not increase above baselinevalues in either group. HR remained stable after induction ofanaesthesia, but increased above baseline values after intubation.Mean maximum HR was 87 beats min^–1 for the remifentanilgroup (12 beats min^–1 above baseline; P=0.065) and 89beats min^–1 for the alfentanil group (15 beats min^–1above baseline; P<0.05). There were no significant differencesbetween groups in HR or arterial pressure at any time. Therewere no incidences of bradycardia. Seven patients in the remifentanilgroup and four in the alfentanil group received ephedrine forhypotension (i.e. SAP<100 mm Hg). Br J Anaesth 2001; 86: 90–3     

Effect of remifentanil infusion rate on stress response to the pre-bypass phase of paediatric cardiac surgery

Background. Opioids are used routinely to eliminate the stressresponse in the pre-bypass phase of paediatric cardiac surgery.Remifentanil is a unique opioid allowing a rapidly titratableeffect. No data are available regarding a suitable remifentanildose regimen for obtunding stress and cardiovascular responsesto such surgery. Methods. We recruited 49 infants and children under 5 yr oldwho were randomized to receive one of four remifentanil infusionrates (0.25, 1.0, 2.5, or 5.0 µg kg^–1 min^–1).Blood samples were obtained at induction, pre-surgery, 5 minafter opening the chest, and immediately pre-bypass. Whole bloodglucose was measured at all time points while cortisol and neuropeptideY (NPY) were measured in the first and last samples. Heart rateand arterial pressure were also recorded. Results. There was a significant increase in whole blood glucose5 min after opening the chest and pre-bypass (P=0.009, P=0.002)in patients receiving remifentanil 0.25 µg kg^–1min^–1, but not in those receiving higher doses. Increasedremifentanil dosage was associated with reduced plasma cortisolduring surgery (P<0.001). Baseline NPY showed considerablevariation and there was no association between pre-bypass NPYand remifentanil dose. There was a significantly higher heartrate at the pre-bypass stage of surgery in the remifentanil0.25 µg kg^–1 min^–1 group compared with higherdoses (P=0.0006). Four out of five neonates with complex cardiacconditions showed severe bradycardia associated with remifentanil. Conclusions. In infants and children under 5 yr, remifentanilinfusions of 1.0 µg kg^–1 min^–1 and greatercan suppress the glucose increase and tachycardia associatedwith the pre-bypass phase of cardiac surgery, while 0.25 µgkg^–1 min^–1 does not. Remifentanil should be usedwith caution in neonates with complex congenital heart disease. Br J Anaesth 2004; 92: 187–94     

Effects of xenon anaesthesia on the circulatory response to hypoventilation

Background. Circulatory response to hypoventilation is aimedat eliminating carbon dioxide and maintaining oxygen delivery(DO₂) by increasing cardiac output (CO). The hypothesis thatthis increase is more pronounced with xenon than with isofluraneanaesthesia was tested in pigs. Methods. Twenty pigs received anaesthesia with xenon 0.55 MAC/remifentanil0.5 µg kg^–1 min^–1 (group X, n=10) or isoflurane0.55 MAC/remifentanil 0.5 µg kg^–1min^–1 (groupI, n=10). CO, heart rate (HR), mean arterial pressure (MAP)and left ventricular fractional area change (FAC) were measuredat baseline, after 5 and 15 min of hypoventilation and after5, 15 and 30 min of restored ventilation. Results. CO increased by 10–20% with both anaesthetics,with an equivalent rise in HR, maintaining DO₂ in spite of a20% reduction in arterial oxygen content. Decreased left ventricular(LV) afterload during hypoventilation increased FAC, and thiswas more marked with xenon (0.60–0.66, P<0.05 comparedwith baseline and isoflurane). This difference is attributedto negative inotropic effects of isoflurane. Increased pulmonaryvascular resistance during hypoventilation was found with bothanaesthetics. Conclusion. The cardiovascular effects observed in this modelof moderate hypoventilation were sufficient to maintain DO₂.Although the haemodynamic response appeared more pronouncedwith xenon, differences were not clinically relevant. An increasein FAC with xenon is attributed to its lack of negative inotropiceffects.     

Propofol-alfentanil vs propofol-remifentanil for posterior spinal fusion including wake-up test

Background. Wake-up test can be used during posterior spinalfusion (PSF) to ensure that spinal function remains intact.This study aims at assessing the characteristics of the wake-uptest during propofol–alfentanil (PA) vs propofol–remifentanil(PR) infusions for PSF surgery. Methods. Sixty patients with scoliosis and candidates for PSFsurgery were randomly allocated in either alfentanil (PA) orremifentanil (PR) group. After an i.v. bolus of alfentanil 30µg kg^–1 in the PA group or remifentanil 1 µgkg^–1 in the PR group, anaesthesia was induced with thiopentaland atracurium. During maintenance, opioid infusion consistedof alfentanil 1 µg kg^–1 min^–1 or remifentanil0.2 µg kg^–1 min^–1, in the PA group and thePR group, respectively. All patients received propofol 50 µgkg^–1 min^–1. Atracurium was given to maintain therequired surgical relaxation. At the surgeon's request, allinfusions were discontinued. Patients were asked to move theirhands and feet. Time from anaesthetic discontinuation to spontaneousventilation (T₁), and from then until movement of the handsand feet (T₂), and its quality were recorded. Results. The average T₁ and T₂ were significantly shorter inthe PR group [3.6 (2.5) and 4.1 (2) min] than the PA group [6.1(4) and 7.5 (4.5) min]. Quality of wake-up test, however, didnot show significant difference between the two groups studied. Conclusion. Wake-up test can be conducted faster with remifentanilcompared with alfentanil infusion during PSF surgery.     

Treatment of ischaemic left ventricular dysfunction with milrinone or dobutamine administered during coronary artery stenosis in the presence of beta blockade in pigs

Background. This study examines the effects of phosphodiesterasetype III (PDEIII) inhibition vs beta stimulation on global functionof the left ventricle (LV) and systemic haemodynamics in a porcinemodel of acute coronary stenosis with beta blockade. Methods. A total of 18 adult swine were anaesthetized. Micromanometer-tippedcatheters were placed in the ascending aorta and LV. Two pairsof ultrasonic dimension transducers were placed in the subendocardiumon the short axis proximal to a left anterior descending (LAD)artery occluder and the long axis of the LV. Before ischaemia,i.v. esmolol was infused to decrease baseline heart rate (HR)by approximately 25%, and all animals received an esmolol infusion(150 µg kg^–1 min^–1). Ischaemia was producedby reducing the flow in the LAD artery by approximately 80%,from 17(4) to 3(2) ml min^–1. Animals were randomized toreceive (after esmolol) one of the following: no drug, shamonly (Group 1, n=6), control (C); 50 µg kg^–1 i.v.milrinone (Group 2, n=6) followed by 0.375 µg kg^–1min^–1 (M); or incremental doses of dobutamine (Group 3,n=6) every 10 min (5, 10 and 20 µg kg^–1 min^–1)(D). Left ventricular function data obtained included HR, arterialand LV pressures, cardiac output (CO), Emax and dP/dT. Measurementswere taken during five time periods: before ischaemia (at baseline,after esmolol) and every 10 min during ischaemia (at 10, 20and 30 min). Results. The effects of beta blockade and ischaemia had a significantimpact on contractility (Emax) in Group M and myocardial performance(left ventricular end-diastolic pressure, LVEDP) in all groups.Left ventricular function (Emax, CO, LVEDP and SVR) was betterpreserved when milrinone was added in Group M. A moderate doseof dobutamine (10 µg kg^–1 min^–1) increasedCO. Only the high dose (20 µg kg^–1 min^–1)improved contractility (Emax), but at the expense of increasedSVR. Also, LVEDP with either dose of dobutamine remained highand unchanged. Conclusions. From our limited findings, it would appear thatthere may, theoretically, be some benefit for using milrinonein preference to other inotropic drugs in the presence of betablockade. Milrinone administration should be considered in patientswith acute ischaemic LV dysfunction and preexisting beta blockadebefore using other inotropic drugs such as beta stimulants. Presented in part at: the 27th Annual Meeting of the Societyof Cardiovascular Anesthesiologists, May 14–18, 2005,Baltimore, MD, USA (Anesth Analg 2005; 100: 5CA60).     

Sedative, haemodynamic and respiratory effects of dexmedetomidine in children undergoing magnetic resonance imaging examination: preliminary results

Background. We evaluated the sedative, haemodynamic and respiratoryeffects of dexmedetomidine and compared them with those of midazolamin children undergoing magnetic resonance imaging (MRI) procedures. Methods. Eighty children aged between 1 and 7 yr were randomlyallocated to receive sedation with either dexmedetomidine (groupD, n=40) or midazolam (group M, n=40). The loading dose of thestudy drugs was administered for 10 min (dexmedetomidine 1 µgkg^–1 or midazolam 0.2 mg kg^–1) followed by continuousinfusion (dexmedetomidine 0.5 µg kg^–1 h^–1or midazolam 6 µg kg^–1 min^–1). Inadequatesedation was defined as difficulty in completing the procedurebecause of the child's movement during MRI. The children whowere inadequately sedated were given a single dose of rescuemidazolam and/or propofol intravenously. Mean arterial pressure(MAP), heart rate (HR), peripheral oxygen saturation (     

Treatment of cardiogenic shock with levosimendan in combination with beta-adrenergic antagonists

Levosimendan, a calcium sensitizer, was used in combinationwith ß-adrenergic antagonists in a man aged 56 yrwith cardiogenic shock, complicating acute myocardial infarction,who developed severe tachycardia after dobutamine administration.The patient's trachea was intubated, his lungs were ventilated,and he was started on dopamine 5 µg kg^–1 min^–1and dobutamine 5 µg kg^–1 min^–1, titrated toa mean arterial pressure 65 mm Hg. He progressively became tachycardiac(>120 beats min^–1) with a cardiac index (CI) of 1.4litre min^–1 m^–2 despite adequate preload. Levosimendan6 µg kg^–1 was administered intravenously over 10min followed by a continuous infusion of 0.2 µg kg^–1min^–1 for 24 h. Within 30 min, the patient's CI increasedto 2.2 litre min^–1 m^–2, but the heart rate (HR)also increased from 142 to 155 beats min^–1. Esmolol 1mg kg^–1 i.v. was administered with a consequent transientdecrease in HR to 110 beats min^–1 without adverse haemodynamiceffects; however, HR increased again shortly afterwards. Carvedilol3.125 mg orally twice a day was then administered, and the dosewas increased to 6.25 mg orally twice daily on the followingday. Subsequently, HR decreased over time and both catecholamineswere discontinued 14 h after starting levosimendan infusion.The trachea was extubated within 20 h and the patient was dischargedto the ward on day 4 after admission. In conclusion, levosimendanin combination with a ß-adrenergic antagonist mayhave beneficial effects in patients with cardiogenic shock whoexhibit tachycardia in response to inotropic agents.     

No clinical evidence of acute opioid tolerance after remifentanil-based anaesthesia

We have prospectively assessed whether remifentanil-based anaesthesiais associated with clinically relevant acute opioid tolerance,expressed as greater postoperative pain scores or morphine consumption.Sixty patients undergoing elective gynaecological, non-laparoscopic,surgery were randomly assigned to receive remifentanil (groupR, n=30) or sevoflurane (group S, n=30) based anaesthesia. Postoperativeanalgesia was provided with morphine through a patient-controlledinfusion device. Mean (SD) remifentanil infusion rate in groupR was 0.23 (0.10) µg kg^–1 min^–1 and mean inspiredfraction of sevoflurane in group S was 1.75 (0.70)%. Mean (SD)cumulative morphine consumption during the first 24 postoperativehours was similar between groups: 28.0 (14.2) mg (group R) vs28.6 (12.4) mg (group S). Pain scores, were also similar betweengroups during this period. These data do not support the developmentof acute opioid tolerance after remifentanil-based anaesthesiain this type of surgery. Br J Anaesth 2001; 87: 866–9     

Recovery from propofol anaesthesia supplemented with remifentanil

We have examined the effects on recovery end-points of supplementationof a propofol-based anaesthetic with remifentanil. After inductionof anaesthesia with propofol and remifentanil 1.0 µg kg^–1,15 patients each were randomly allocated to target plasma propofolconcentrations of 2, 3, 4 or 5 µg ml^–1for maintenance of anaesthesia. Remifentanil was administeredby infusion for supplementation in doses required for maintenanceof adequate anaesthesia. All patients received 50% nitrous oxidein oxygen and ventilation was controlled. The total amount ofdrugs used and times to different recovery end-points were recorded.Cognitive function was also assessed using a Mini-Mental Statequestionnaire. The median dose of remifentanil for maintenanceof adequate anaesthesia (excluding the initial bolus dose) inthe four groups was 0.21, 0.15, 0.11 and 0.13 µg kg^–1 min^–1respectively (P=0.0026). The median times to eye opening andorientation were shortest in the 2 µg ml^–1group [6.0 and 6.5 min, 8.5 and 10.8 min, 13.4 and15.8 min, and 14.2 and 19.5 min respectively in thepropofol 2, 3, 4, and 5 µg ml^–1 groups respectively(P<0.001)]. The times to discharge from the recovery wardand the Mini-Mental State scores were not significantly different. Br J Anaesth 2001; 86: 361–5     

Questioning the cardiocirculatory excitatory effects of opioids under volatile anaesthesia

Background. Opioid-induced hyperalgesia has been demonstratedin awake animals. We observed an increased haemodynamic reactivityin response to noxious stimuli in rats under sevoflurane anaesthesiatreated with a very low dose of sufentanil. The aim of thisinvestigation was to determine whether the two phenomena sharea common origin: an opioid-induced excitatory reaction. To addressthis, we administered several drugs with proven efficacy inopioid hyperalgesia to rats presenting with haemodynamic hyper-reactivity. Methods. The MACbar of sevoflurane was measured in controlsand in animals treated with sufentanil 0.005 µg kg^–1min^–1 before and after administration of i.v. (0.25, 0.5mg kg^–1) and intrathecal (i.t.) (250 µg) ketamine,i.v. (0.5, 1 mg kg^–1) and i.t. (30 µg) MK-801(NMDAantagonist), i.v. (0.1, 0.5 mg kg^–1) naloxone, i.v. (10mg kg^–1) and i.t. (50, 100 µg) ketorolac or i.t.(100, 150 µg) meloxicam (COX-2 inhibitor). Results. Sufentanil 0.005 µg kg^–1 min^–1 significantlyincreased MACbar (3.2 (SD 0.3) versus 1.9 (0.3) vol%). Withthe exception of naloxone, all drugs displayed a significantMACbar-sparing effect (>50%) in controls. Naloxone completelyprevented haemodynamic hyperactivity. Two patterns of reactionwere recorded for the other drugs: either hyper-reactivity wassuppressed and the MACbar-sparing effect was maintained (i.t.ketamine, i.t. MK-801, i.t. ketorolac [100 µg], i.t. meloxicam[150 µg]) or hyper-reactivity was blocked but MACbar-sparingeffect was lost (i.v. ketamine [0.5 mg kg^–1], i.v. MK-801[0.5, 1 mg kg^–1], i.v. ketorolac [10 µg kg^–1],i.t. ketorolac [50 µg], i.t. meloxicam [100 µg]). Conclusions. We have demonstrated that low-dose sufentanil-inducedhaemodynamic hyper-reactivity is an excitatory µ-opiate-relatedphenomenon. This effect is reversed by drugs effective in treatingopiate-induced hyperalgesia.     

Low-dose remifentanil to suppress haemodynamic responses to noxious stimuli in cardiac surgery: a dose-finding study

Background: High-dose remifentanil (1–5 µg kg^–1 min^–1),commonly used for cardiac surgery, has been associated withmuscle rigidity, hypotension, bradycardia, and reduced cardiacoutput. The aim of this study was to determine an optimal lowerremifentanil dose, which should be accompanied by fewer adverseevents, that still effectively suppresses haemodynamic responsesto typical stressful stimuli (i.e. intubation, skin incision,and sternotomy). Methods: Total i.v. anaesthesia consisted of a target-controlled propofol(2 µg ml^–1) and a remifentanil infusion. Forty patientswere allocated to receive either a constant infusion of remifentanilat 0.1 µg kg^–1 min^–1 or up-titrations to 0.2,0.3, or 0.4 µg kg^–1 min^–1, respectively, 5min before each stimulus. Subsequently, changes in heart rateand mean arterial blood pressure were recorded for 8 min. Increasesexceeding 20% of baseline were considered to be of clinicalrelevance. Patients who exhibited these alterations were termedresponders. Results: The number of responders was less with the two higher remifentanildosages (P < 0.05) while propofol target doses could eitherbe kept at the same level or even be reduced without affectingthe plane of anaesthesia. Although single phenylephrine bolushad to be applied more frequently in these two groups (P <0.05), no severe haemodynamic depression was observed. Conclusions: Remifentanil at 0.3 and 0.4 µg kg^–1 min^–1in combination with a target-controlled propofol infusion inthe pre-bypass period is well tolerated. It appears to mitigatepotentially hazardous haemodynamic responses from stressfulstimuli equally well as higher doses when compared with datafrom the literature.     

Remifentanil compared with sufentanil during extra-corporeal shock wave lithotripsy with spontaneous ventilation: a double-blind,randomized study

Background. The pharmacokinetic properties of remifentanil mayallow a rapid analgesic action during painful procedures andshort lasting postoperative respiratory depression. Methods. We carried out a randomized, blind, study in 60 patientsto compare remifentanil (continuous i.v. infusion starting at0.025 µg kg^–1 min^–1) and sufentanil (i.v.doses of 0.15 µg kg^–1) during extra-corporeal shockwave lithotripsy (ESWL). Pain was assessed using a numericalpain scale (0–100), and pain relief was defined as a score     

Patient-controlled analgesia for labour using remifentanil: a feasibility study

We have investigated the efficacy and safety of remifentanilin a patient-controlled analgesia device for labour in 21 women.Remifentanil was available in increasing doses (bolus doses0.25–1.0 µg kg^–1) with and without a backgroundinfusion (0.025–0.05 µg kg^–1 min^–1).A lockout time of 2 min was used. Thirteen out of 21 (62%) womenchose to continue using remifentanil up to and during delivery.Nineteen out of 21 (90%) achieved a reduction in pain scorefrom baseline. Using a VAS of 0–10 cm the median maximumreduction in pain score was 3 cm (range 0–8 cm). Therewas a significant reduction (P<0.05) from baseline pain scores(median= 8 cm) to scores at bolus doses in the range 0.25–0.5µg kg^–1 (median=5 cm). There were no significantreductions in the fetal heart rate. Apgar scores and cord bloodgas analyses remained within normal limits. We conclude thata remifentanil patient-controlled analgesia system (bolus doses0.25–0.5 µg kg^–1, without a background infusion)may safely provide worthwhile, although incomplete, analgesiafor labour. Br J Anaesth 2001; 87: 415–20     

Testing of a new pneumatic device to cause pain in humans

Background. Surgical pain typically combines superficial anddeep pain. We wished to generate pain that resembled surgicalpain, reliably and reproducibly, in volunteers. Methods. We constructed a computer-controlled pneumatic deviceto apply pressure to the anterior tibia. The reproducibilityof the pain was tested by rating the pressure that caused painrated 4–5 on a visual analogue scale (VAS) on days 0,7, and 24 in 10 volunteers. The effect of remifentanil (0.025,0.05, 0.075, and 0.1 µg kg^–1 min^–1) on paintolerance in another set of volunteers (n=11) was used as anindirect measure of the reliability of pain production. Results. The pressure needed (0.7 (0.3) to 0.9 (0.4) atm (mean(SD)) to induce pain rated 4–5 (VAS) did not vary, showinglong-term reproducibility of the method. When pressure was appliedto cause increasing pain in volunteers (n=11) 0.05 µgkg^–1 min^–1 remifentanil increased pain toleranceby 50%. An approximate doubling of the dose (0.1 µg kg^–1min^–1) increased pain tolerance significantly more. Thelinear logarithmic dose-effect relationship shows that the devicecauses pain reliably, and this can be reduced with opioid treatment. Conclusion. This pneumatic device can apply pain reliably andreproducibly. Br J Anaesth 2004; 92: 532–5     

Dexmedetomidine vs midazolam for monitored anaesthesia care during cataract surgery

Background. Cataract surgery is commonly performed under localanaesthesia with midazolam sedation. Dexmedetomidine, a sedative-analgesic,is devoid of respiratory depressant effects, and its use incataract surgery has not been reported. This double-blind studycompared the use of dexmedetomidine and midazolam in patientsundergoing cataract surgery. Methods. Forty-four patients undergoing cataract surgery underperibulbar anaesthesia randomly received either i.v. dexmedetomidine1 µg kg^–1 over 10 min; followed by 0.1–0.7µg kg^–1 h^–1 i.v. infusion (Group D), or midazolam20 µg kg^–1 i.v.; followed by 0.5 mg i.v. bolusesas required (Group M). Sedation was titrated to a Ramsay sedationscore of 3. Mean arterial pressure (MAP), heart rate (HR), readinessfor recovery room discharge (time to Aldrete score of 10), andpatients' and surgeons' satisfaction (on a scale of 1–7)were determined. Results. MAP and HR were lower in Group D compared with GroupM [86 (SE 3) vs 102 (3) mm Hg and 65 (2) vs 72 (2) beats min^–1,respectively] (P<0.05). Group D patients had slightly highersatisfaction with sedation [median (IQR): 6 (6–7) vs 6(5–7), P<0.05], but delayed readiness for discharge[45 (36–54) vs 21 (10–32) min, P<0.01] comparedwith patients in Group M. Surgeons' satisfaction was comparablein both groups [5 (4–6) vs 5 (4–6)]. Conclusion. Compared with midazolam, dexmedetomidine does notappear to be suitable for sedation in patients undergoing cataractsurgery. While there was a slightly better subjective patientsatisfaction, it was accompanied by relative cardiovasculardepression and delayed recovery room discharge.     

Pretreatment with remifentanil to prevent withdrawal after rocuronium in children

Background. Pain from rocuronium injection is a common side-effectreported to occur in 50–80% of the patients. This randomized,double-blind, placebo-controlled study was designed to evaluatethe efficacy of pretreatment with i.v. remifentanil on preventionof withdrawal response during rocuronium injection in paediatricpatients. Methods. After obtaining parental consents, 70 paediatric patientswere randomly allocated into two groups to receive either i.v.remifentanil 1 µg kg^–1 (remifentanil group, n=35)or i.v. saline 5 ml (saline group, n=35). Anaesthesia was inducedwith thiopental sodium 2.5% (5 mg kg^–1) and the test drugwas injected over 30 s. One minute after the test drug injection,rocuronium 1% (0.6 mg kg^–1) was injected over 5 s andthe response was recorded. Mean arterial pressure (MAP) andheart rate were recorded on arrival in the operating theatre,before and 1 min after the tracheal intubation. Results. The overall incidence of withdrawal movements was significantlyhigher in the saline group (33 patients; 94%) than that in theremifentanil group (8 patients; 23%) (P<0.001). No patientin the remifentanil group showed generalized movement, whereas51% of patients in the saline group did. Remifentanil preventedsignificant increase in MAP after intubation. Conclusion. This study demonstrated that pretreatment with remifentanil1 µg kg^–1 provided a safe and simple method forreducing the incidence of rocuronium-associated withdrawal movementwith haemodynamic stability in children.