PULMONARY VASCULAR EFFECTS OF TRINITROGLYCERIN AND ISOSORBIDE DINITRATE AFTER CARDIOPULMONARY BYPASS

We have compared the systemic and right ventricular haemodynamiceffects of trinitroglycerin (TNG) and isosorbide dinitrate (ISDN)in patients recovering from coronary artery bypass grafting.Each of the 16 patients was given increasing i.v. doses of thetwo nitrates in a random order and double blind fashion untilthe target of a 25% decrease in mean pulmonary artery pressure(MPAP) was achieved. Total doses of TNG 9 (6–12) µgkg^–1 (mean, 95% confidence interval) and ISDN 148 (76–220)µg kg^–1 were given during infusions of 22 (18–25)min and 34 (28–41) min duration, respectively. The targetdecrease in MPAP was produced with infusion rates of TNG 0.5(0.4–0.7) µg kg^–1 min^–1 and ISDN 5.8(4.1–7.5) µg kg^–1 min^–1 These dosesproduced similar acute decreases in MPAP and similar effectson pulmonary and systemic vascular resistances and systemicand right ventricular haemodynamic variables. We conclude thatTNG is more than 10 times as potent as ISDN in its acute haemodynamic effects in cardiac surgical patients in the immediatepostoperative period. Both nitrates have relatively greatereffect on the pulmonary than the systemic vasculature. (Br.J. Anaesth. 1993; 71:720–724) Presented in part at the Annual Meeting of the Society of CardiovascularAnesthesiologists, San Antonio, Texas, May 1991.     

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.     

TOTAL I.V. ANAESTHESIA WITH PROPOFOL AND ALFENTANIL: DOSE REQUIREMENTS FOR PROPOFOL AND THE EFFECT OF PREMEDICATION WITH CLONIDINE

We determined in 51 healthy patients undergoing body surfacesurgery the dose requirements for propofol, as part of a totali.v. anaesthesia technique with an alfentanil infusion. Afterpremedication with temazepam, patients received alfentanil 50µg kg^–1 followed by an infusion of 50 µg kg^–1h^–1. Patients were anaesthetized with a loading dose ofpropofol followed by a three-stage infusion designed to reachone of five preselected blood concentrations of propofol. Themotor response to the initial surgical incision was noted andprobit analysis was used to derive the ED₅₀ (2.94 mg kg^–1h^–1; 95% confidence limits: 2.35–3.37 mg kg^–1h^–1). and ED₉₅ (4.98 mg kg^–1 h^–1; 95% limits:4.13–8.8 mg kg^–1 h^–1) for the final propololinfusion rate under these conditions. Whole blood concentrationof propofol at the time of the incision was related linearlyto the infusion rate and the EC₅₀ and EC₉₅ (probit analysis)were derived as 1.44 (95% confidence limits 0.62–1.87)and 4.05 (95% confidence limits 2.78–30.5) µg ml^–1,respectively. Postoperative recovery was rapid, uncomplicatedand uneventful. In a subgroup of eight patients, the additionof clonidine 0.6mg to the premedication significantly decreasedthe requirement for propofol (P <0.05) during surgery, butresulted in prolonged recovery times. Pilot study presented to the Anaesthetic Research Society, June24, 1988 [1].     

CONTINUOUS INFUSION OF FENTANYL OR ALFENTANIL FOR CORONARY ARTERY SURGERY: Plasma Opiate Concentrations, Haemodynamics and Postoperative Course

Nine patients received a mean total dose of 110 µg kg^–1of fentanyl and 10 patients received alfentanil 1379 µgkg^–1 as a continuous infusion during coronary artery bypassgrafting (CABG). Circulatory stability was well maintained throughthe induction of anaesthesia and a similar cardiovascular coursewas achieved with both agents, with the exception of small differencesin heart rate and cardiac index immediately before trachealintubation. Similar haemodynamic responses to sternotomy, cardiopulmonarybypass and awakening from anaesthesia were found with both analgesics.Although the times to awakening and extubation were somewhatshorter in patients receiving alfentanil, the differences betweenthe groups were not significant. With the continuous infusiontechniques, plasma opiate concentrations could be maintainedwell above the awakening values during cardiopulmonary bypass.In a total dose ratio of 1:13, fentanyl and alfentanil producedsimilar haemodynamic profiles and clinical courses in patientsundergoing CABG.     

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.     

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     

EFFECTS OF ALFENTANIL ON THE PRESSOR AND CATECHOLAMINE RESPONSES TO TRACHEAL INTUBATION

The effects of alfentanil (given during induction of anaesthesia)on the haemodynamic and catecholamine responses to trachealintubation were studied in 44 adult patients who received alfentanil10 µg kg^–1 or 40 µg kg^–1, or salineplacebo. Alfentanil 10 µg kg^–1 and 40 fig kg^–1prevented any increase in heart rate and arterial pressure aftertracheal intubation. Alfentanil 40 µg kg^–1 producedprofound hypotension and bradycardia. The use of alfentanilin both doses was associated with a decrease in plasma adrenalineconcentrations after tracheal intubation.     

INFLUENCE OF CROHN'S DISEASE ON THE PHARMACOKINETICS AND PHARMACODYNAMICS OF ALFENTANIL

We have compared the dose requirements, pharma cokinetics andpharmacodynamics of alfentanil in 12 patients with Crohn's diseaseand 10 control patients undergoing abdominal surgery. Plasmaconcentrations of ₁-acid glycoprotein (AAG) and alfentanil proteinbinding were also measured. Anaesthesia was induced with aifentanil100 µg kg^–1 and thiopentone, and maintained withnitrous oxide in oxygen and aifentanil 25–200 µgkg^–1 h^–1 Arterial blood samples were obtained beforeand after each change in the aifentanil infusion rate and for6 h after stopping the infusion. Pharmacokinetic data were derivedusing non-compartmental methods. Alfentanil concen tration—effectdata were evaluated by non-linear regression, where effect waseither response or no response to surgical stimulation. Meanintra operative aifentanil requirement was greater in patientswith Crohn's disease (2.48 µg kg^–1 min^–1)than in control patients (1.35 µg kg^–1 min^–1)(P< 0.01). Mean elimination half-life, total plasma clearanceand steady state distribution volume in patients with Crohn'sdisease were comparable to those in control patients (80 vs81 min, 5.7 vs 6.4 ml kg^–1 min^–1 and 0.70 vs 0.68litre kg^–1, respectively). Mean plasma concentration atwhich the probability of no response was 50% for the intra-abdominalperiod of surgery was greater in the Crohn group (359 ng ml^–1)than in the control group (199 ng ml^–1 (P<0.02). PlasmaAAG concentrations were greater in the Crohn group, but thefree fraction of aifentanil was similar in both groups. Thisstudy indicates that the increased alfentanil requirement inpatients with Crohn's disease may be attributed to a changein pharmacodynamics. (Br. J. Anaesth. 1993; 71: 827–834)     

Reducing stress responses in the pre-bypass phase of open heart surgery in infants and young children: a comparison of different fentanyl doses

High-dose opioids are advocated for paediatric cardiac surgeryto suppress stress responses but they can produce unwanted sideeffects. There are no data on the dose-dependent effects ofopioids on the stress response on which to base rational opioidadministration. We conducted a dose ranging study on 40 childrenless than 4 yr undergoing elective open heart surgery usingone of five fentanyl doses: 2, 25, 50, 100 or 150 µg kg^–1before surgery. The standardized anaesthetic also included pancuroniumand isoflurane. Blood samples were taken at induction, beforeincision, after sternotomy, immediately before, and at the endof cardiopulmonary bypass. Patients in the 2 µg kg^–1group had significant rises in pre-bypass glucose (P<0.01),pre- and post-bypass cortisol (P<0.01), and pre- and post-bypassnorepinephrine (P<0.01). No significant rise occurred inglucose, cortisol and catecholamines in any of the higher dosagegroups. Patients in the 2 µg kg^–1 group had significantlyhigher mean systolic blood pressure (P<0.02) and heart rate(P<0.04). A balanced anaesthetic containing fentanyl 25–50µg kg^–1 is sufficient to obtund haemodynamic andstress responses to the pre-bypass phase of surgery. Higherdoses of fentanyl (100 and 150 µg kg^–1) offer littleadvantage over 50 µg kg^–1, and can necessitate interventionto prevent hypotension.     

ALFENTANIL AND PROPOFOL INFUSIONS FOR SURGERY IN THE BURNED PATIENT

We have studied combinations of alfentanil and propofol fortotal i.v. anaesthesia in 24 severely burned patients. No inhalationagents were used. After a loading dose of alfentanil 100 µgkg^–1, the intraoperative requirement was 1.24 (SEM 0.7)µg kg^–1 min^–1, and after a propofol inductiondose of 2 mg kg^–1 the maintenance rate was 100 µgkg^–1 min^–1. Initial hypotension occurred after inductionof anaesthesia, but during the operation, cardiovascular variableswere stable. After adequate antagonism of neuromuscular block,respiratory depression persisted in three patients when thetwo agents were discontinued simultaneously; this was not seenwhen alfentanil was discontinued 15 min before propofol. Qualityof recovery was good, and satisfactory postoperative analgesiawas present in the majority of patients 2 h after operation.This study indicates that total i.v. anaesthesia with a combinationof alfentanil and propofol appears to be satisfactory in burnedpatients.     

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.     

Fast-track cardiac anaesthesia in the elderly: effect of two different anaesthetic techniques on mental recovery

Elderly patients may be considered for ‘fast-track’cardiac anaesthesia, but can suffer psychological complicationsand slow recovery of mental function after surgery, which caninterfere with recovery. Reduced metabolism and changed distributionof anaesthetic and sedative agents can cause poor recovery.We made a prospective randomized comparison of mental function,haemodynamic stability and extubation and discharge times inelderly patients (65–79 yr) receiving two premedication,anaesthetic and sedative techniques. Patients received eitherpropofol (n=39) (fentanyl 10–15 µg kg^–1and propofol 2–6 mg kg^–1 intraoperativelyand a propofol infusion for 3 h postoperatively) or premedicationwith lorazepam followed by midazolam for anaesthesia (n=39)(fentanyl 10–15 µg kg^–1 and midazolam0.05–0.075 mg kg^–1 intraoperatively anda midazolam infusion for 3 h postoperatively). Impairmentof mental function was noted in 41% of patients in the propofolgroup and 83% in the lorazepam and midazolam group (P=0.001)18 h after extubation. Patients in the propofol group wereextubated earlier [1.4 (SD 0.6) vs 1.9 (0.8) h, P=0.02];and reached standard intensive care unit discharge criteria[7.6 (4.6) vs 14.2 (13) h, P=0.02] and hospital dischargecriteria [4.3 (1.0) vs 4.9 (1.1) days, P=0.04) sooner than patientsin the lorazepam and midazolam group, but actual discharge timesdid not differ between the groups. Haemodynamic values werestable in both groups.Br J Anesth 2001; 86: 68–76     

PHARMACOKINETICS OF ALFENTANIL DURING AND AFTER A FIXED RATE INFUSION

Twenty-nine patients (age range 14–81 yr) undergoing orthopaedicsurgery received alfentanil 100 µg kg^–1 given astwo i.v. boluses followed by a fixed rate infusion of 1 µgkg^–1 min^–1 for 44–445 min. Additional 1-mgbolus doses of alfentanil were administered as required. Plasmasamples were assayed for alfentanil using radio-immunoassay.Pharmacokinetic parameters were estimated by a model-independentapproach and by curve-fitting. Regression analysis showed nostatistical relationship between T, CI or Vd and the durationof the infusion, total dose or body weight. We found no significantcorrelation between age and T of alfentanil for patients youngerthan 40 yr. For patients older than 40 yr, T increased linearlywith age. There was no significant decrease in Cl with age,although the lower values for CI (100–200 ml min^–1)were generally found in subjects older than 60 yr. The presentstudy demonstrated that a 100-µg kg^–1 loading doseand a 1-µg kg^–1 min^–1 infusion may be appropriatefor analgesia in general surgical procedures.     

Tracheal intubation without neuromuscular block in children

We have studied 80 healthy children, aged 2–14 yr, undergoingadenotonsillectomy in a double-blind, randomized design. Trachealintubation facilitated by either suxamethonium 1.5 mg kg^–1or alfentanil 15 µg kg^–1 was compared after inductionof anaesthesia with propofol 3–4 mg kg^–1. The qualityof tracheal intubation was graded according to the ease of laryngoscopy,position of the vocal cords, coughing, jaw relaxation and movementof limbs. There were no significant differences in the overallassessment of intubating conditions between the two groups,and all children underwent successful tracheal intubation. Fewerpatients coughed (P < 0.014) and limb movement was less common(P < 0.007) after tracheal intubation facilitated by suxamethonium.Alfentanil attenuated the haemodynamic responses to trachealintubation. (Br. J. Anaesth. 1994; 72: 403–406)     

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).     

EFFECT OF ALFENTANIL ANAESTHESIA ON THE ADRENOCORTICAL AND HYPERGLYCAEMIC RESPONSE TO ABDOMINAL SURGERY

Plasma concentrations of cortisol and glucose were measuredfrom before to 9 h after skin incision in 24 patients undergoingabdominal hysterectomy. The patients were randomly allocatedto receive either high-dose alfentanil anaesthesia (150 µgkg^–1 initially, followed by continuous infusion at a rateof 3 µg kg^–1 min^–1) or neurolept anaesthesia(droperidol 0.25 mg kg^–1 plus fentanyl 5 µg kg^–1initially, followed by intermittent incremental doses of fentanyl50 µg). The intraoperative and initial postoperative increasesin plasma cortisol and glucose concentrations were inhibited(P < 0.05) by alfentanil but, later in the postoperativeperiod, both groups showed identical increases in cortisol andglucose concentrations. Mean arterial pressure and heart ratewere more stable in the alfentanil group. The concept of "stress-free"anaesthesia during highdose opiate administration seems to bevalid during operation and for the initial 1–3 h intothe postoperative period.     

Continuous infusions of propofol administered to dogs: effects on ICG and propofol disposition

We have studied the effects of stepwise increasing infusionrates of propofol 200–500 µg kg^–1 min^–1on blood concentrations of propofol and the disposition andclearance of a bolus dose of indocyanine green (ICG) 0.5 mgkg^–1 in 10 acutely instrumented dogs. Drug concentrationsand ICG clearance were measured 30 min after each change ofinfusion rate and after reverting for 60 min to the basal propofolinfusion rate. Increasing infusion rates resulted in significantprolongation of the elimination half-life of ICG and decreasein ICG clearance at the largest infusion rate (500 µgkg^–1 min^–1) compared with the basal rate. Similarly,there were greater than predicted blood concentrations of propofolat the largest infusion rate. When the infusion rate revertedto 200 µg kg^–1 min^–1, and continued for 60min, there was a significant difference between the initialblood concentration of propofol at this basal infusion rateand this latter value (P < 0.01). These changes reflect thepersistent myocardial depression observed during the recoveryphase. (Br. J. Anaesth. 1994; 72: 451–455) Presented in part at the Annual Meeting of the American Societyof Anesthesiologists, October 1990, Las Vegas, U.S.A.     

PHARMACOKINETICS OF ALFENTANIL IN CHILDREN UNDERGOING SURGERY

Alfentanil pharmacokinetics and protein binding were deteminedin 20 children aged 10 months 6.5 yr. The data were comparedwith those from 10 adult patients. Eighteen children receiveda single i.v. dose of alfentanil 20 µg kg^–1 Theapparent volume of distribution (V^ß) did not differbetween the two groups. The degree of plasma protein bindingwas also similar in children and adults with mean free fractionsof 11.5±0.9% (±SD) and 11.8±3.9%, respectively.There were marked differences in the elimination half-life ofalfentanil (63±24 min in children; 95±20 min inadults (P < 0.001)) and plasma clearance of alfentanil (11.1±3.9ml min^–1 kg^–1 in children and 5.9±1.6 mlmin^–1 kg^–1 in adults (P < 0.001)).     

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.     

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 (