QT prolongation under sevoflurane in infants

Introduction   QT interval prolongation may cause the potentially lethal tachyarrhythmia torsades de pointes ( 1 ). The cause of the QT interval prolongation may be a congenital mutation in genes encoding cardiac potassium and sodium channels ( 2 ) or be acquired following drug administration ( 3 ) or metabolic disorders ( 4 ). Among a few other drugs volatile anaesthetics prolong the QT interval. During the last few years sevoflurane has become the most used volatile anaesthetic for the induction of anaesthesia in infants.
Methods   This investigation, on infants aged from 1 to 6 months, was approved by the institutional ethic committee. Thirty-six otherwise healthy infants due to elective surgery were included in our study The patients were randomly assigned to one of two treatment groups. Group S ( n  = 24) was anaesthetised with sevoflurane, Group H was anaesthetised with halothane. ECG recordings were taken before the anaesthesia onset, 15 min after the first contact with the volatile anaesthetic and 60 min after the ending of the volatile gas exposition. QTc interval was calculated using the Bazett's formula ( 5 ).
Results   QTc interval was significantly ( P < 0.0002) (Table 1) lengthened 15 min after anaesthesia induction with sevoflurane as well as 60 min ( P < 0.01) after the ending of the gas exposition without any difference in age and gender. The QTc interval in patients anaesthetised with halothane did not show any significant change.  

  Table 1     

2.

Effects of isoflurane and halothane on the auditory and somatosensory evoked potentials     

M C Bimar-Blanc  J M Dejode  J Bimar 《Annales fran?aises d'anesthèsie et de rèanimation》1988,7(4):279-288

The effects of isoflurane and halothane anaesthesia on brainstem auditory (BEAR) and somatosensory evoked potentials (SEP) were recorded in 15 patients; eight received isoflurane and seven halothane. Atropine alone was given as premedication. After induction of anaesthesia with thiopentone, it was maintained with 50% nitrous oxide in oxygen. Ventilation was controlled. Isoflurane and halothane concentrations were gradually increased to 3%. Recordings were made at 1%, 2.5% and 3%. There were statistically significant differences in the latencies of SEP and BEAR with increasing concentrations of anaesthetic. The BEAR waves significantly affected were wave V and the latency between peaks I to V (p less than 0.001); for the SEP, it was wave N20. SEP central conduction time was prolonged with both anaesthetics (p less than 0.001). The effects of isoflurane and halothane were similar. These results could not be explained by changes in central body temperature or end-tidal carbon dioxide concentration. The study showed a dose-related direct effect of both anaesthetic agents on the brainstem auditory and somatosensory evoked responses. It may be that the measurement of changes in evoked potentials could be a useful indicator of anaesthetic depth.     

3.

Redistribution of halothane and sevoflurane under simulated conditions of acute airway obstruction     

Y. Girgis  C. M. Frerk  D. Pigott 《Anaesthesia》2001,56(7):613-615

Forty patients having surgery requiring muscle paralysis and tracheal intubation were randomly allocated to receive either halothane (n = 20) or sevoflurane (n = 20). Following intravenous anaesthesia and tracheal intubation, inhalation induction of anaesthesia was simulated. After attaining an end-tidal anaesthetic concentration of 2 MAC for the respective agent, the airway was obstructed for 3 min. The end-tidal anaesthetic concentration was measured for the first three breaths following the period of airway obstruction. The decrease in alveolar concentration of sevoflurane following 3 min of airway obstruction was found to be significantly greater than that of halothane. We conclude that even if the airway obstructs completely during inhalational induction of general anaesthesia, awakening would be faster with sevoflurane than with halothane.     

4.

Occupational exposure to sevoflurane, halothane and nitrous oxide during paediatric anaesthesia   Waste gas exposure during paediatric anaesthesia     

K. Hoerauf  W. Funk  M. Harth  & J. Hobbhahn 《Anaesthesia》1997,52(3):215-219

We report the findings of a study on exposure of operating room staff to sevoflurane, halothane and nitrous oxide during induction and maintenance of anaesthesia in children. Concentrations of anaesthetic agents in the operating theatre were measured directly by highly sensitive, photoacoustic infrared spectrometer during 20 anaesthetics. Samples were taken from the breathing zones of the anaesthetist and the circulating nurse. The operating theatre was of modern design with an air conditioning system providing 20 changes of air each hour. The threshold values of 100 ppm N₂O, 50 ppm isoflurane and 10 ppm halothane recommended by the United Kingdom Committee for Occupational Safety and Health (COSH) were exceeded in several cases for a short time during mask induction. After tracheal intubation, trace concentrations of sevoflurane, halothane and N₂O were mostly under the recommended levels and comparable to levels measured during adult anaesthesia.     

5.

The Bispectral Index in children: comparing isoflurane and halothane   总被引：3，自引：1，他引：2  

Davidson AJ  Czarnecki C 《British journal of anaesthesia》2004,92(1):14-17

Background. The Bispectral Index (BIS) has been calibrated forseveral general anaesthetic agents including isoflurane. Halothaneis still used in paediatric anaesthesia. Compared with othervolatile anaesthetics, halothane has a different receptor affinityand differing effects on the EEG. There are limited data evaluatingthe BIS with halothane. We set out to compare the BIS usinghalothane and isoflurane at a clinically relevant equipotentconcentration (1 MAC) and at a reproducible measure of anaestheticeffect (awakening). Methods. Forty children aged between 2 and 15 yr were enrolledin a masked randomized trial—20 in each group. Anaesthesiawas induced with sevoflurane or propofol. Either halothane orisoflurane were given to obtain an end-tidal concentration of1 MAC for 15 min. The BIS was then recorded. The BIS was alsorecorded at awakening. Values (mean (SD)) were compared witha t test. Results. At 1 MAC the BIS for halothane was significantly greaterthan isoflurane (56.5 (8.1) vs 35.9 (8.5), P<0.0001). Atawakening there was no significant difference (BIS halothane;81.1 (11.9), BIS isoflurane; 82.5 (16.4)). The difference inmeans at awakening was 1.4 (95% CI –8.2 to 11.1). Conclusions. At equipotent concentrations of halothane and isofluraneBIS valves were significantly greater with halothane. At awakeningthe BIS values were equivalent for each agent. This findingis consistent with the BIS being more affected by the agentused at higher concentrations of anaesthetic. The BIS must beinterpreted with caution when using halothane. Br J Anaesth 2004; 92: 14–17     

6.

The effects of sevoflurane, isoflurane and desflurane on QT interval of the ECG   总被引：4，自引：0，他引：4  

Yildirim H  Adanir T  Atay A  Katircioğlu K  Savaci S 《European journal of anaesthesiology》2004,21(7):566-570

BACKGROUND AND OBJECTIVE: To determine if there is any significant difference between the effects of desflurane, isoflurane and sevoflurane on the QT interval, QT dispersion, heart rate corrected QT interval and QTc dispersion of the electrocardiogram. METHODS: The study was conducted in a prospective, double blind and randomized manner in a teaching hospital. Ninety ASA I patients, aged 16-50 yr, undergoing general anaesthesia for noncardiac surgery were studied. RESULTS: There was no significant change in QT intervals during the study in any group (P > 0.05). QT dispersion in the sevoflurane group 49+/-14 ms vs. 37+/-10 ms; in the desflurane group 55+/-16 and 62+/-21 ms vs. 35+/-14 ms and in the isoflurane group 54+/-26 and 59+/-24 ms vs. 42+/-19 ms were significantly increased at 3 and 10 min after 1 MAC of steady end-tidal anaesthetic concentration compared with baseline values (P < 0.05). QTc values in the sevoflurane group were 444+/-24 and 435+/-2 1ms vs. 413+/-19 ms (P < 0.05), in the isoflurane group were 450+/-26 and 455+/-34 ms vs. 416+/-34 ms (P < 0.05), in the desflurane group were 450+/-26 and 455+/-34 ms vs. 416+/-34 ms (P < 0.05) at 3 and 10 min after reaching 1 MAC of anaesthetic concentration and significantly increased compared with baseline values. QTc dispersion increased significantly with sevoflurane 62+/-14 ms vs. 45+/-16 ms (P < 0.05); isoflurane 70+/-36 ms at 3 min and 75+/-36 ms at 10 min after reaching 1 MAC of anaesthetic concentration vs. 50+/-24 ms (P < 0.05); desflurane 67+/-25 ms at 3 min and 74+/-27 ms at 10 min after 1 MAC concentration vs. 41+/-22 ms (P < 0.05). CONCLUSION: Sevoflurane, isoflurane and desflurane all prolonged QTd, QTc and QTcd but there were no significant intergroup differences.     

7.

Time course of potentiation of mivacurium by halothane and isoflurane in children   总被引：2，自引：1，他引：1  

Meretoja  O. A.; Wirtavuori  K.; Taivainen  T.; Olkkola  K. T. 《British journal of anaesthesia》1996,76(2):235-238

We studied 40 children, aged 1-15 yr, to analyse the time course of potentiation of mivacurium produced by halothane and isoflurane. A steady infusion requirement of mivacurium to maintain 90% neuromuscular block was established during thiopentone-alfentanil-nitrous oxide- oxygen anaesthesia. Patients were then allocated randomly to receive 1 MAC end-tidal concentration of either halothane (group Hal) or isoflurane (group Iso) while neuromuscular block was maintained at 90%. Both volatile agents decreased the infusion requirements of mivacurium in an exponential manner in that maximal potentiation occurred only after 30-80 min. Maximal reduction in infusion rate (32% in group Hal and 70% in group Iso; P < 0.0001) did not depend on the age of the child but became established sooner the younger the child in the case of isoflurane (P = 0.002).      

8.

Isoflurane in paediatric anaesthesia   总被引：1，自引：0，他引：1  

W. S. WREN  A. J. MCSHANE  J. G. MCCARTHY  B. J. LAMONT  W. F. CASEY  V. M. HANNON 《Anaesthesia》1985,40(4):315-323

The characteristics of induction with and recovery from isoflurane anaesthesia were studied in 248 children. The mean time to loss of consciousness was 1.5 min (SD 0.5). Tracheal intubation, without interruption of spontaneous ventilation, was accomplished in a mean time of 4.2 min (SD 54 seconds). Movement and excitement, of 20-30 seconds duration, occurred in 23.9% children and 22 patients coughed during induction; 15 (12.6%) during the first 124 inductions; 7 (5.6%) subsequently. The mean half-times of reduction of alveolar isoflurane concentrations in 28 children whose lungs were ventilated with isoflurane and in 13 children who breathed isoflurane spontaneously during anaesthesia were: 45 sec after exposure for one hour, 70 sec after exposure of 2-3 hours and 110 seconds following exposures of 4-8 hours. The mean recovery times of the three groups were 6.5, 9.5 and 11.5 min respectively. In two further groups of nine children the mean half times of elimination of halothane and isoflurane were 220 seconds and 54 seconds respectively; recovery from isoflurane was markedly faster. Isoflurane is well accepted by children; induction is more rapid than with halothane, and the marked flexibility in the control of its effects are due to its relative insolubility. It has wide application in paediatric anaesthesia.     

9.

Similar haemodynamic, respiratory and metabolic changes with the use of sevoflurane or halothane in children breathing spontaneously via a laryngeal mask airway     

Erb T  Christen P  Kern C  Frei FJ 《Acta anaesthesiologica Scandinavica》2001,45(5):639-644

BACKGROUND: In preschool children, short-lasting surgical procedures are often performed under combined inhalational and regional anaesthesia with the child breathing spontaneously via a laryngeal mask airway (LMA). Despite widespread use, only limited data are available on haemodynamic, respiratory and metabolic effects of sevoflurane and halothane during LMA anaesthesia. METHODS: In an open-label, randomised, controlled study, 49 children (aged 3-8 years) were allocated to receive either sevoflurane or halothane in 60% nitrous oxide. After insertion of the LMA, end-tidal concentrations of sevoflurane or halothane were maintained at 1 MAC with the child ventilating spontaneously throughout the entire procedure. Analgesia was provided by caudal block. Haemodynamic and respiratory parameters were recorded, and capillary blood-gas samples were obtained repeatedly. RESULTS: Changes in heart rate (HR) and systolic blood pressure were similar in both groups during all observed periods, apart from a significantly higher increase in HR during inhalational induction with sevoflurane (P<0.05). Regression slope analysis during anaesthesia revealed a decrease of the respiratory rate of 5 breaths h-1 (P<0.001) and an increase of end-tidal PCO2 and capillary PCO2 of about 0.25 kPa h-1 (P<0.001), with no significant difference between the two groups. Base excess, calculated in capillary blood gas samples, did not change over time (P>0.5) in either group. CONCLUSIONS: The use of approximately 1 MAC sevoflurane or halothane in 60% N2O in children breathing spontaneously via LMA resulted in comparable haemodynamic, respiratory and metabolic changes, and clinically relevant deteriorations did not occur during the 65-min study period.     

10.

The theoretical ideal fresh-gas flow sequence at the start of low-flow anaesthesia   总被引：6，自引：0，他引：6  

W. W. Mapleson 《Anaesthesia》1998,53(3):264-272

A spreadsheet model of a circle breathing system and a 70-kg anaesthetised 'standard man' has been used to simulate the first 20 min of low-flow anaesthesia with halothane, enflurane, isoflurane, sevoflurane and desflurane in oxygen. It is shown that, with the fresh-gas flow set initially equal to the total ventilation and the fresh-gas partial pressure to 3 MAC, the end-expired partial pressure can be raised to 1 MAC in 1 min with desflurane and sevoflurane, 1.5 min with isoflurane, 2.5 min with enflurane and 4 min with halothane. Sequences of lower fresh-gas flow and partial pressure settings are given for then maintaining 1 MAC end-expired partial pressure, with a minimum usage of anaesthetic, e.g. 13 ml of liquid desflurane in 20 min (of which only 33% is taken up by the patient) if the minimum acceptable flow is 1 lmin⁻¹, or 8 ml (with 57% in the patient) if the minimum is 250 mlmin⁻¹.     

11.

A non-rebreathing coaxial anaesthesia system: dependence of end-tidal gas concentrations on fresh gas flow and tidal volume     

W. A. Tweed 《Anaesthesia》1997,52(3):237-241

A non-rebreathing adaptation of the Bain coaxial anaesthesia circuit was developed in Nepal as a simple and economical anaesthetic system for underdeveloped countries. It was made by inserting a coaxial (Bain) tubing between an Ambu-E valve and an Ambu self-inflating bag. The present study examined the dependence of end-tidal gas concentrations on fresh gas flow and tidal volume during halothane/oxygen/air inhalation anaesthesia. Four levels of fresh gas flow with normocapnia (0.2–3 l.min⁻¹) and three levels of tidal volume at a constant respiratory rate of 15 breath.min⁻¹ (to achieve end-tidal carbon dioxide values of 4 ± 0.5%, 5 ± 0.5% and 6 ± 0.5%) were introduced in random order. Twelve ASA class 1 and 2 adult patients having intra-abdominal or pelvic surgery were studied. With increasing fresh gas flow rates, there were proportionate increases in the end-tidal concentrations of oxygen and halothane; with decreasing tidal volume and therefore less air dilution, there were proportionate increases in the end-tidal concentrations of carbon dioxide, oxygen and halothane. Both effects were statistically and clinically significant. Thus, when this system is used as described, the end-tidal concentrations of oxygen and halothane are highly dependent upon both the fresh gas flow and the tidal volume.     

12.

A comparison of sevoflurane to halothane in paediatric surgical patients: results of a multicentre international study     

B. KATARIA MD  R. EPSTEIN MD  †  A. BAILEY MD  ‡  M. SCHMITZ MD  §  W.W. BACKUS MD  ¶  D. SCHOECK MD  &#;  W. HACKL MD    M.J.M. GOVAERTS MD  ††  J.C. ROUGE PHD  ‡‡  C. KERN MD  §§  K. VAN  ACKERN MD¶¶ D.J. HATCH MB  &#;&#; 《Paediatric anaesthesia》1996,6(4):283-292

Induction, emergence and recovery characteristics were compared during sevoflurane or halothane anaesthetic in a large (428) multicentre, international study of children undergoing elective inpatient surgical procedures. Two hundred and fourteen children in each group underwent inhalation induction with nitrous oxide/oxygen and sevoflurane or halothane. Incremental doses of either study drug were added until loss of eyelash reflex was achieved. Steady state concentrations of anaesthesia were maintained until the end of surgery when anaesthetic agents were terminated simultaneously. Time variables were recorded for induction, emergence and the first need for analgesia in the recovery room. In addition, in 86 of the children in both groups, venous blood samples were drawn for plasma fluoride levels during and after surgery. There was a trend toward smoother induction (induction of anaesthesia without coughing, breath holding, excitement laryngospasm, bronchospasm, increased secretion, and vomiting) in the sevoflurane group with faster induction (2.1 min vs 2.9 min, P= 0.037) and rapid emergence times (10.3 min vs 13.9 min, P= 0.003). Among the children given sevoflurane, 2% developed bradycardia compared with 11% in the halothane group. Postoperatively, 46% of the children in the halothane group developed nausea and or vomiting versus 31% in the sevoflurane group (P= 0.002). Two children in the halothane group developed cardiac dysrhythmia and were dropped from the study. In addition, a child in the halothane group developed malignant hyperthermia, received dantrolene, and had an uneventful recovery. Mean maximum inorganic fluoride concentration was 18.3 μM˙l^?1. The fluoride concentrations peaked within one h of termination of sevoflurane anaesthetic and returned rapidly to baseline within 48 h. This study suggests that sevoflurane may be the drug of choice for the anaesthetic management of children.     

13.

Is prolongation of the QTc interval during isoflurane anaesthesia more prominent in women pretreated with anthracyclines for breast cancer?     

Owczuk R  Wujtewicz MA  Sawicka W  Wujtewicz M  Swierblewski M 《British journal of anaesthesia》2004,92(5):658-661

Background. Inhalation anaesthetics and anthracycline chemotherapeuticdrugs may both prolong the QT interval of the electrocardiogram.We investigated whether isoflurane may induce or augment QTcprolongation in patients who had previously received cancerchemotherapy including anthracycline drugs. Methods. Forty women undergoing surgery for breast cancer wereincluded in the study. They were divided into two groups: (A)women previously treated with anthracyclines (n=20); and (B)women not treated with antineoplastic drugs (n=20). All patientsreceived a standardized balanced anaesthetic in which isoflurane0.5 vol% was used. The QT and corrected QT intervals were measuredbefore anaesthesia, after induction and tracheal intubation,after 1, 5, 15, 30, 60 and 90 min of anaesthesia, and duringrecovery. Results. In both groups we observed a tendency to QTc prolongation,but statistically significant differences among baseline valuesand values observed during isoflurane-containing anaesthesiawere seen only in group A. During anaesthesia, significant differencesin QTc values between the two groups were observed. Conclusion. In female patients pretreated with anthracyclinesfor breast cancer, the tendency to QTc prolongation during isoflurane-containinggeneral anaesthesia was more strongly expressed than in patientswithout previous chemotherapy. Br J Anaesth 2004; 92: 658–61     

14.

END-TIDAL CONCENTRATIONS OF HALOTHANE AND ISOFLURANE DURING INDUCTION OF ANAESTHESIA IN YOUNG AND ELDERLY PATIENTS     

DWYER  R.; FEE  J. P. H.; CLARKE  R. S. J. 《British journal of anaesthesia》1990,64(1):36-41

Twenty-two young (18–32 yr) and 22 healthy elderly (60–80yr) patients received either halothane or isoflurane for maintenanceof anaesthesia during controlled ventilation. Endtidal fractionalconcentrations (FE) of the agents were measured for 20 min aftertheir introduction into inspired gas and the increase in end-tidalconcentrations of the two agents was compared during inductionof anaesthesia using the ratios of FE to the inspired fraction(F1). FE: F1 ratios for isoflurane were higher than those forhalothane in both young and elderly patients, confirming thatequilibration of end-tidal with inspired concentration occursmore rapidly with isoflurane than with halothane in both agegroups. FE: F1 ratios for isoflurane became significantly lowerin the elderly than in the young after 15 min administrationof isoflurane. This suggests slower induction of anaesthesiain the elderly if equipotent concentrations of isoflurane areused; the clinical significance of this difference is probablysmall. Mean FE: F1 ratios for halothane in elderly patientswere similar to those in the young throughout induction of anaesthesia.     

15.

The effect of esmolol on the QTc interval during induction of anaesthesia in patients with coronary artery disease     

F. Erdil  S. Demirbilek  Z. Begec  E. Ozturk  A. But  M. Ozcan Ersoy 《Anaesthesia》2009,64(3):246-250

The aim of this study was to evaluate whether esmolol has an effect on QT interval during induction of anaesthesia using etomidate and fentanyl in patients with known coronary artery disease. Sixty patients were prospectively randomised to either a control group or the esmolol group. Esmolol was administered as a bolus 1 mg.kg⁻¹, followed by a continuous infusion at 250 μg.kg⁻¹min⁻¹. All patients received etomidate 0.3 mg.kg⁻¹ and fentanyl 15 μg.kg⁻¹. The ECG was recorded prior to induction of anaesthesia (T0), 5 min following the start of drug infusions (T1), 1 min following etomidate (T2), 3 min following vecuronium (T3), 30 s (T4), 2 min (T5) and 4 min (T6) after intubation. In the esmolol group, QTc interval was significantly shorter at T1, T2 and T4 compared to the control group (p < 0.05). In conclusion, QTc interval increased following tracheal intubation during induction of anaesthesia using etomidate and fentanyl. An infusion of Esmolol attenuated the QTc interval prolongation associated with tracheal intubation.     

16.

The effect of inhalational anaesthetics on QTc interval     

Karagöz AH  Basgul E  Celiker V  Aypar U 《European journal of anaesthesiology》2005,22(3):171-174

BACKGROUND AND OBJECTIVE: The aim of this study was to assess time dependent cumulative effects of three different inhalation anaesthetics on QTc interval during the maintenance of anaesthesia. METHOD: Seventy-five ASA I-II male patients undergoing inguinal herniorrhaphy were randomly allocated into three groups. No premedication was given. Anaesthesia was induced with thiopental and tracheal intubation was facilitated by vecuronium in all groups. Anaesthesia was maintained with 0.8% halothane (Group I) (n = 25), 1% isoflurane (Group II) (n = 25), or 2% sevoflurane (Group III) (n = 25) and 66% nitrous oxide in oxygen. Three lead electrocardiogram recordings were taken before induction, 2, 5, 10, 15, 30 and 45 min after induction and after extubation. Heart rate, systolic, diastolic, mean arterial pressure and SpO2 were recorded at the same time. Heart rate and corrected QT interval were evaluated by using Bazett's formula. Multivariate analysis of variance for repeated measures was used to determine intergroup and intragroup differences. RESULTS: There was no statistically significant difference in the baseline QTc values of the groups. There was no difference between QTc values with halothane and sevoflurane. There was a difference between QTc values with isoflurane and those with the other two inhalation anaesthetics (P < 0.05). Although QTc values in the isoflurane group were higher at all times, the critical value of 440 ms was not exceeded. CONCLUSION: We conclude that halothane 0.8%, isoflurane 1% and sevoflurane 2% do not prolong QTc interval.     

17.

The efficacy of clonidine for reducing perioperative haemodynamic changes and volatile anaesthetic requirements in children     

K. Nishina    K. Mikawa    N. Maekawa  H. Obara 《Acta anaesthesiologica Scandinavica》1996,40(6):746-751

Background: Oral clonidine given as a premedicant in adults has been shown to reduce intraoperative inhalation anaesthetic requirements and provide perioperative haemodynamic stability. We conducted the current study to ascertain whether or not these beneficial effects of clonidine can be reproduced in children. Methods: In a prospective, randomized, double-blind, controlled clinical trial, 60 children (ASA I) aged 5–11 yr, received placebo (control), 2 μg kg^-1 clonidine, or 4 μg kg^-1 clonidine orally 105 min before induction of anaesthesia. Anaesthesia was induced with halothane, nitrous oxide in oxygen via mask and maintained with halothane and 60% nitrous oxide in oxygen. The halothane concentration was titrated to the concentration required to maintain haemodynamic stability (defined as 20% of blood pressure (BP) and heart rate (HR)) for maintenance of anaesthesia. The end-tidal concentration of halothane was monitored throughout anaesthesia. On completion of surgery, nitrous oxide and halothane were discontinued. Following confirmation of recovery from anaesthesia and muscle relaxation, the endotracheal tube was removed. Results: Higher inspired concentrations of halothane (%) were required in the control and 2 μg kg^-1 clonidine-treated groups (mean SD: 1.1 ±0.2 and 1.0±0.2, respectively) than in the 4 μg kg^-1 clonidine-treated group (0.6±0.1) for haemodynamic stability (P<0.05). Clonidine, 4 μg kg^-1, significantly reuced the intraoperative lability (coefficient of variation) of systolic and diastolic BP and HR compared with the other two regimens. Conclusion: Oral clonidine premedication at a dose of 4 μg kg^-1 provided intraoperative haemodynamic stability and reduced anaesthetic requirements in children. However, we are unable to extrapolate these observations to younger children and infants.     

18.

The effect of clonidine on sevoflurane requirements for anaesthesia and hypnosis   总被引：3，自引：0，他引：3  

T. Katoh  & K. Ikeda 《Anaesthesia》1997,52(4):377-381

We evaluated the effects of clonidine given orally on sevoflurane requirements for anaesthesia and hypnosis. Patients received either clonidine (5 μg.kg⁻¹) by mouth ( n  =21) 90 min before surgery or no premedication ( n  =21) by random allocation. MAC was calculated using repeated tetanic nerve stimulation with end-tidal sevoflurane concentration increased or decreased by 0.3 vol.% depending on the previous response. MAC awake was calculated according to the response to verbal command. The mean (SD) MAC in the clonidine-treated patients was 1.53 (0.20)% compared with 1.83 (0.15)% in the control group (p <0.001). Similarly, MAC awake was reduced in the clonidine group (0.50 (0.08)% compared with 0.60 (0.07)% in the control group) (p <0.001). We conclude that clonidine 5 μg.kg⁻¹ orally administered pre-operatively reduces sevoflurane requirements for anaesthesia and hypnosis.     

19.

TRANSCRANIAL DOPPLER SONOGRAPHY: EFFECTS OF HALOTHANE, ENFLURANE AND ISOFLURANE ON BLOOD FLOW VELOCITY IN THE MIDDLE CEREBRAL ARTERY     

THIEL  A.; ZICKMANN  B.; ZIMMERMANN  R.; HEMPELMANN  G. 《British journal of anaesthesia》1992,68(4):388-393

Systolic, diastolic, and mean blood flow velocity in the middlecerebral artery (Vs,mca; Vd,mca; Wm,mca) and pulsatility (Vs- Vd)/Vm of the waveform obtained were recorded in 51 patientsbefore, during and after general anaesthesia. Transcranial Doppler(TCD) sonographic variables were measured in the awake patientand after induction of anaesthesia with thiopentone 5–6mg kg^–1. After tracheal intubation, 17 patients received0.8% halothane and 66% nitrous oxide in oxygen for 30 min (15minnormoventilation; 15min hyper-ventilation). The inspired halothaneconcentration was then increased to 1.6% for 45min (15min normoventilation;15 min hyperventilation; 15 min normoventilation with nitrousoxide replaced by oxygen). Enflurane (1.7% for 30 min and 3.4%for 45 min) was given to another 17 patients; 17 other patientsreceived isoflurane (1.2% and 2.4%). Mean arterial pressure(MAP), nasopharyngeal temperature, end-tidal carbon dioxideconcentration, inspired and end-tidal anaesthetic agent concentrations,haemoglobin concentration, PVC and TCD variables were measuredat the end of each 15 min period. After recovery from anaesthesia,TCD variables were measured again. There were no intergroupdifferences in changes in MAP, nasopharyngeal temperature, haemoglobinconcentration and PCV. Halothane, enflurane and isoflurane atlow doses and normoventilation had little influence on TCD variablescompared with awake values. In large concentrations with nitrousoxide in oxygen and normoventilation, there were differencesbetween the volatile agents. Halothane increased blood flowvelocities, but enflurane and isoflurane caused little change.Hyperventilation always decreased blood flow velocities andincreased pulsatility. Six of 17 patients undergoing hyperventilationwith 2.4% isoflurane and nitrous oxide in oxygen showed zerodiastolic flow. This phenomenon was not observed in any patientreceiving halothane or enflurane. With high doses of the volatileagents and normoventilation, blood flow velocities decreasedin all groups after discontinuation of nitrous oxide. Our TCDresults are compatible with the known effects of halothane,enflurane and isoflurane on cerebral blood flow (CBF). However,the relative changes in blood flow velocity and CBF may notbe proportional with large doses of volatile agents, as a constantdiameter of basal cerebral arteries may not be assumed underthese conditions.     

20.

Recovery characteristics of sevoflurane or halothane for day-case anaesthesia in children aged 1-3 years     

Viitanen H  Baer G  Annila P 《Acta anaesthesiologica Scandinavica》2000,44(1):101-106

BACKGROUND: Our objective was to compare the recovery characteristics of sevoflurane and halothane for short day-case anaesthesia in a specifically limited age group of children 1-3 yr. METHODS: Eighty unpremedicated children undergoing day-case adenoidectomy were randomly assigned to receive inhalational induction with either sevoflurane 8% or halothane 5% and nitrous oxide in oxygen (70/30) via a face mask. Tracheal intubation was performed without a muscle relaxant. Anaesthesia was continued with the volatile anaesthetic, adjusted to maintain heart rate and blood pressure within +/-20% of initial values. Recovery was evaluated using a modified Aldrete score, a Pain/Discomfort scale and by measuring recovery end-points. A postoperative questionnaire was used to determine the well-being of the child at home until 24 h after discharge. RESULTS: Emergence and interaction occurred significantly earlier after sevoflurane than halothane but discharge times were similar. More children in the sevoflurane group achieved full Aldrete scores within the first 30 min after anaesthesia, although this group suffered more discomfort during the first 10 min. The amount of postoperative analgesic administered was higher and the first dose given earlier in the sevoflurane group. Postoperative vomiting was more common with halothane, but side-effects in the two groups were otherwise similar in the recovery room and at home. CONCLUSIONS: In children 1-3 yr, sevoflurane provided more rapid early recovery but not discharge after anaesthesia of <30-min duration. Apart from more vomiting with halothane and more discomfort during the first 10 min after awakening with sevoflurane, the quality of recovery was similar with the two anaesthestics.     

Effects of isoflurane and halothane on the auditory and somatosensory evoked potentials

The effects of isoflurane and halothane anaesthesia on brainstem auditory (BEAR) and somatosensory evoked potentials (SEP) were recorded in 15 patients; eight received isoflurane and seven halothane. Atropine alone was given as premedication. After induction of anaesthesia with thiopentone, it was maintained with 50% nitrous oxide in oxygen. Ventilation was controlled. Isoflurane and halothane concentrations were gradually increased to 3%. Recordings were made at 1%, 2.5% and 3%. There were statistically significant differences in the latencies of SEP and BEAR with increasing concentrations of anaesthetic. The BEAR waves significantly affected were wave V and the latency between peaks I to V (p less than 0.001); for the SEP, it was wave N20. SEP central conduction time was prolonged with both anaesthetics (p less than 0.001). The effects of isoflurane and halothane were similar. These results could not be explained by changes in central body temperature or end-tidal carbon dioxide concentration. The study showed a dose-related direct effect of both anaesthetic agents on the brainstem auditory and somatosensory evoked responses. It may be that the measurement of changes in evoked potentials could be a useful indicator of anaesthetic depth.     

Redistribution of halothane and sevoflurane under simulated conditions of acute airway obstruction

Forty patients having surgery requiring muscle paralysis and tracheal intubation were randomly allocated to receive either halothane (n = 20) or sevoflurane (n = 20). Following intravenous anaesthesia and tracheal intubation, inhalation induction of anaesthesia was simulated. After attaining an end-tidal anaesthetic concentration of 2 MAC for the respective agent, the airway was obstructed for 3 min. The end-tidal anaesthetic concentration was measured for the first three breaths following the period of airway obstruction. The decrease in alveolar concentration of sevoflurane following 3 min of airway obstruction was found to be significantly greater than that of halothane. We conclude that even if the airway obstructs completely during inhalational induction of general anaesthesia, awakening would be faster with sevoflurane than with halothane.     

Occupational exposure to sevoflurane, halothane and nitrous oxide during paediatric anaesthesia Waste gas exposure during paediatric anaesthesia

We report the findings of a study on exposure of operating room staff to sevoflurane, halothane and nitrous oxide during induction and maintenance of anaesthesia in children. Concentrations of anaesthetic agents in the operating theatre were measured directly by highly sensitive, photoacoustic infrared spectrometer during 20 anaesthetics. Samples were taken from the breathing zones of the anaesthetist and the circulating nurse. The operating theatre was of modern design with an air conditioning system providing 20 changes of air each hour. The threshold values of 100 ppm N₂O, 50 ppm isoflurane and 10 ppm halothane recommended by the United Kingdom Committee for Occupational Safety and Health (COSH) were exceeded in several cases for a short time during mask induction. After tracheal intubation, trace concentrations of sevoflurane, halothane and N₂O were mostly under the recommended levels and comparable to levels measured during adult anaesthesia.     

The Bispectral Index in children: comparing isoflurane and halothane

Background. The Bispectral Index (BIS) has been calibrated forseveral general anaesthetic agents including isoflurane. Halothaneis still used in paediatric anaesthesia. Compared with othervolatile anaesthetics, halothane has a different receptor affinityand differing effects on the EEG. There are limited data evaluatingthe BIS with halothane. We set out to compare the BIS usinghalothane and isoflurane at a clinically relevant equipotentconcentration (1 MAC) and at a reproducible measure of anaestheticeffect (awakening). Methods. Forty children aged between 2 and 15 yr were enrolledin a masked randomized trial—20 in each group. Anaesthesiawas induced with sevoflurane or propofol. Either halothane orisoflurane were given to obtain an end-tidal concentration of1 MAC for 15 min. The BIS was then recorded. The BIS was alsorecorded at awakening. Values (mean (SD)) were compared witha t test. Results. At 1 MAC the BIS for halothane was significantly greaterthan isoflurane (56.5 (8.1) vs 35.9 (8.5), P<0.0001). Atawakening there was no significant difference (BIS halothane;81.1 (11.9), BIS isoflurane; 82.5 (16.4)). The difference inmeans at awakening was 1.4 (95% CI –8.2 to 11.1). Conclusions. At equipotent concentrations of halothane and isofluraneBIS valves were significantly greater with halothane. At awakeningthe BIS values were equivalent for each agent. This findingis consistent with the BIS being more affected by the agentused at higher concentrations of anaesthetic. The BIS must beinterpreted with caution when using halothane. Br J Anaesth 2004; 92: 14–17     

The effects of sevoflurane, isoflurane and desflurane on QT interval of the ECG

BACKGROUND AND OBJECTIVE: To determine if there is any significant difference between the effects of desflurane, isoflurane and sevoflurane on the QT interval, QT dispersion, heart rate corrected QT interval and QTc dispersion of the electrocardiogram. METHODS: The study was conducted in a prospective, double blind and randomized manner in a teaching hospital. Ninety ASA I patients, aged 16-50 yr, undergoing general anaesthesia for noncardiac surgery were studied. RESULTS: There was no significant change in QT intervals during the study in any group (P > 0.05). QT dispersion in the sevoflurane group 49+/-14 ms vs. 37+/-10 ms; in the desflurane group 55+/-16 and 62+/-21 ms vs. 35+/-14 ms and in the isoflurane group 54+/-26 and 59+/-24 ms vs. 42+/-19 ms were significantly increased at 3 and 10 min after 1 MAC of steady end-tidal anaesthetic concentration compared with baseline values (P < 0.05). QTc values in the sevoflurane group were 444+/-24 and 435+/-2 1ms vs. 413+/-19 ms (P < 0.05), in the isoflurane group were 450+/-26 and 455+/-34 ms vs. 416+/-34 ms (P < 0.05), in the desflurane group were 450+/-26 and 455+/-34 ms vs. 416+/-34 ms (P < 0.05) at 3 and 10 min after reaching 1 MAC of anaesthetic concentration and significantly increased compared with baseline values. QTc dispersion increased significantly with sevoflurane 62+/-14 ms vs. 45+/-16 ms (P < 0.05); isoflurane 70+/-36 ms at 3 min and 75+/-36 ms at 10 min after reaching 1 MAC of anaesthetic concentration vs. 50+/-24 ms (P < 0.05); desflurane 67+/-25 ms at 3 min and 74+/-27 ms at 10 min after 1 MAC concentration vs. 41+/-22 ms (P < 0.05). CONCLUSION: Sevoflurane, isoflurane and desflurane all prolonged QTd, QTc and QTcd but there were no significant intergroup differences.     

Time course of potentiation of mivacurium by halothane and isoflurane in children

We studied 40 children, aged 1-15 yr, to analyse the time course of potentiation of mivacurium produced by halothane and isoflurane. A steady infusion requirement of mivacurium to maintain 90% neuromuscular block was established during thiopentone-alfentanil-nitrous oxide- oxygen anaesthesia. Patients were then allocated randomly to receive 1 MAC end-tidal concentration of either halothane (group Hal) or isoflurane (group Iso) while neuromuscular block was maintained at 90%. Both volatile agents decreased the infusion requirements of mivacurium in an exponential manner in that maximal potentiation occurred only after 30-80 min. Maximal reduction in infusion rate (32% in group Hal and 70% in group Iso; P < 0.0001) did not depend on the age of the child but became established sooner the younger the child in the case of isoflurane (P = 0.002).      

Isoflurane in paediatric anaesthesia

The characteristics of induction with and recovery from isoflurane anaesthesia were studied in 248 children. The mean time to loss of consciousness was 1.5 min (SD 0.5). Tracheal intubation, without interruption of spontaneous ventilation, was accomplished in a mean time of 4.2 min (SD 54 seconds). Movement and excitement, of 20-30 seconds duration, occurred in 23.9% children and 22 patients coughed during induction; 15 (12.6%) during the first 124 inductions; 7 (5.6%) subsequently. The mean half-times of reduction of alveolar isoflurane concentrations in 28 children whose lungs were ventilated with isoflurane and in 13 children who breathed isoflurane spontaneously during anaesthesia were: 45 sec after exposure for one hour, 70 sec after exposure of 2-3 hours and 110 seconds following exposures of 4-8 hours. The mean recovery times of the three groups were 6.5, 9.5 and 11.5 min respectively. In two further groups of nine children the mean half times of elimination of halothane and isoflurane were 220 seconds and 54 seconds respectively; recovery from isoflurane was markedly faster. Isoflurane is well accepted by children; induction is more rapid than with halothane, and the marked flexibility in the control of its effects are due to its relative insolubility. It has wide application in paediatric anaesthesia.     

Similar haemodynamic, respiratory and metabolic changes with the use of sevoflurane or halothane in children breathing spontaneously via a laryngeal mask airway

BACKGROUND: In preschool children, short-lasting surgical procedures are often performed under combined inhalational and regional anaesthesia with the child breathing spontaneously via a laryngeal mask airway (LMA). Despite widespread use, only limited data are available on haemodynamic, respiratory and metabolic effects of sevoflurane and halothane during LMA anaesthesia. METHODS: In an open-label, randomised, controlled study, 49 children (aged 3-8 years) were allocated to receive either sevoflurane or halothane in 60% nitrous oxide. After insertion of the LMA, end-tidal concentrations of sevoflurane or halothane were maintained at 1 MAC with the child ventilating spontaneously throughout the entire procedure. Analgesia was provided by caudal block. Haemodynamic and respiratory parameters were recorded, and capillary blood-gas samples were obtained repeatedly. RESULTS: Changes in heart rate (HR) and systolic blood pressure were similar in both groups during all observed periods, apart from a significantly higher increase in HR during inhalational induction with sevoflurane (P<0.05). Regression slope analysis during anaesthesia revealed a decrease of the respiratory rate of 5 breaths h-1 (P<0.001) and an increase of end-tidal PCO2 and capillary PCO2 of about 0.25 kPa h-1 (P<0.001), with no significant difference between the two groups. Base excess, calculated in capillary blood gas samples, did not change over time (P>0.5) in either group. CONCLUSIONS: The use of approximately 1 MAC sevoflurane or halothane in 60% N2O in children breathing spontaneously via LMA resulted in comparable haemodynamic, respiratory and metabolic changes, and clinically relevant deteriorations did not occur during the 65-min study period.     

The theoretical ideal fresh-gas flow sequence at the start of low-flow anaesthesia

A spreadsheet model of a circle breathing system and a 70-kg anaesthetised 'standard man' has been used to simulate the first 20 min of low-flow anaesthesia with halothane, enflurane, isoflurane, sevoflurane and desflurane in oxygen. It is shown that, with the fresh-gas flow set initially equal to the total ventilation and the fresh-gas partial pressure to 3 MAC, the end-expired partial pressure can be raised to 1 MAC in 1 min with desflurane and sevoflurane, 1.5 min with isoflurane, 2.5 min with enflurane and 4 min with halothane. Sequences of lower fresh-gas flow and partial pressure settings are given for then maintaining 1 MAC end-expired partial pressure, with a minimum usage of anaesthetic, e.g. 13 ml of liquid desflurane in 20 min (of which only 33% is taken up by the patient) if the minimum acceptable flow is 1 lmin⁻¹, or 8 ml (with 57% in the patient) if the minimum is 250 mlmin⁻¹.     

A non-rebreathing coaxial anaesthesia system: dependence of end-tidal gas concentrations on fresh gas flow and tidal volume

A non-rebreathing adaptation of the Bain coaxial anaesthesia circuit was developed in Nepal as a simple and economical anaesthetic system for underdeveloped countries. It was made by inserting a coaxial (Bain) tubing between an Ambu-E valve and an Ambu self-inflating bag. The present study examined the dependence of end-tidal gas concentrations on fresh gas flow and tidal volume during halothane/oxygen/air inhalation anaesthesia. Four levels of fresh gas flow with normocapnia (0.2–3 l.min⁻¹) and three levels of tidal volume at a constant respiratory rate of 15 breath.min⁻¹ (to achieve end-tidal carbon dioxide values of 4 ± 0.5%, 5 ± 0.5% and 6 ± 0.5%) were introduced in random order. Twelve ASA class 1 and 2 adult patients having intra-abdominal or pelvic surgery were studied. With increasing fresh gas flow rates, there were proportionate increases in the end-tidal concentrations of oxygen and halothane; with decreasing tidal volume and therefore less air dilution, there were proportionate increases in the end-tidal concentrations of carbon dioxide, oxygen and halothane. Both effects were statistically and clinically significant. Thus, when this system is used as described, the end-tidal concentrations of oxygen and halothane are highly dependent upon both the fresh gas flow and the tidal volume.     

A comparison of sevoflurane to halothane in paediatric surgical patients: results of a multicentre international study

Induction, emergence and recovery characteristics were compared during sevoflurane or halothane anaesthetic in a large (428) multicentre, international study of children undergoing elective inpatient surgical procedures. Two hundred and fourteen children in each group underwent inhalation induction with nitrous oxide/oxygen and sevoflurane or halothane. Incremental doses of either study drug were added until loss of eyelash reflex was achieved. Steady state concentrations of anaesthesia were maintained until the end of surgery when anaesthetic agents were terminated simultaneously. Time variables were recorded for induction, emergence and the first need for analgesia in the recovery room. In addition, in 86 of the children in both groups, venous blood samples were drawn for plasma fluoride levels during and after surgery. There was a trend toward smoother induction (induction of anaesthesia without coughing, breath holding, excitement laryngospasm, bronchospasm, increased secretion, and vomiting) in the sevoflurane group with faster induction (2.1 min vs 2.9 min, P= 0.037) and rapid emergence times (10.3 min vs 13.9 min, P= 0.003). Among the children given sevoflurane, 2% developed bradycardia compared with 11% in the halothane group. Postoperatively, 46% of the children in the halothane group developed nausea and or vomiting versus 31% in the sevoflurane group (P= 0.002). Two children in the halothane group developed cardiac dysrhythmia and were dropped from the study. In addition, a child in the halothane group developed malignant hyperthermia, received dantrolene, and had an uneventful recovery. Mean maximum inorganic fluoride concentration was 18.3 μM˙l^?1. The fluoride concentrations peaked within one h of termination of sevoflurane anaesthetic and returned rapidly to baseline within 48 h. This study suggests that sevoflurane may be the drug of choice for the anaesthetic management of children.     

Is prolongation of the QTc interval during isoflurane anaesthesia more prominent in women pretreated with anthracyclines for breast cancer?

Background. Inhalation anaesthetics and anthracycline chemotherapeuticdrugs may both prolong the QT interval of the electrocardiogram.We investigated whether isoflurane may induce or augment QTcprolongation in patients who had previously received cancerchemotherapy including anthracycline drugs. Methods. Forty women undergoing surgery for breast cancer wereincluded in the study. They were divided into two groups: (A)women previously treated with anthracyclines (n=20); and (B)women not treated with antineoplastic drugs (n=20). All patientsreceived a standardized balanced anaesthetic in which isoflurane0.5 vol% was used. The QT and corrected QT intervals were measuredbefore anaesthesia, after induction and tracheal intubation,after 1, 5, 15, 30, 60 and 90 min of anaesthesia, and duringrecovery. Results. In both groups we observed a tendency to QTc prolongation,but statistically significant differences among baseline valuesand values observed during isoflurane-containing anaesthesiawere seen only in group A. During anaesthesia, significant differencesin QTc values between the two groups were observed. Conclusion. In female patients pretreated with anthracyclinesfor breast cancer, the tendency to QTc prolongation during isoflurane-containinggeneral anaesthesia was more strongly expressed than in patientswithout previous chemotherapy. Br J Anaesth 2004; 92: 658–61     

END-TIDAL CONCENTRATIONS OF HALOTHANE AND ISOFLURANE DURING INDUCTION OF ANAESTHESIA IN YOUNG AND ELDERLY PATIENTS

Twenty-two young (18–32 yr) and 22 healthy elderly (60–80yr) patients received either halothane or isoflurane for maintenanceof anaesthesia during controlled ventilation. Endtidal fractionalconcentrations (FE) of the agents were measured for 20 min aftertheir introduction into inspired gas and the increase in end-tidalconcentrations of the two agents was compared during inductionof anaesthesia using the ratios of FE to the inspired fraction(F1). FE: F1 ratios for isoflurane were higher than those forhalothane in both young and elderly patients, confirming thatequilibration of end-tidal with inspired concentration occursmore rapidly with isoflurane than with halothane in both agegroups. FE: F1 ratios for isoflurane became significantly lowerin the elderly than in the young after 15 min administrationof isoflurane. This suggests slower induction of anaesthesiain the elderly if equipotent concentrations of isoflurane areused; the clinical significance of this difference is probablysmall. Mean FE: F1 ratios for halothane in elderly patientswere similar to those in the young throughout induction of anaesthesia.     

The effect of esmolol on the QTc interval during induction of anaesthesia in patients with coronary artery disease

The aim of this study was to evaluate whether esmolol has an effect on QT interval during induction of anaesthesia using etomidate and fentanyl in patients with known coronary artery disease. Sixty patients were prospectively randomised to either a control group or the esmolol group. Esmolol was administered as a bolus 1 mg.kg⁻¹, followed by a continuous infusion at 250 μg.kg⁻¹min⁻¹. All patients received etomidate 0.3 mg.kg⁻¹ and fentanyl 15 μg.kg⁻¹. The ECG was recorded prior to induction of anaesthesia (T0), 5 min following the start of drug infusions (T1), 1 min following etomidate (T2), 3 min following vecuronium (T3), 30 s (T4), 2 min (T5) and 4 min (T6) after intubation. In the esmolol group, QTc interval was significantly shorter at T1, T2 and T4 compared to the control group (p < 0.05). In conclusion, QTc interval increased following tracheal intubation during induction of anaesthesia using etomidate and fentanyl. An infusion of Esmolol attenuated the QTc interval prolongation associated with tracheal intubation.     

The effect of inhalational anaesthetics on QTc interval

BACKGROUND AND OBJECTIVE: The aim of this study was to assess time dependent cumulative effects of three different inhalation anaesthetics on QTc interval during the maintenance of anaesthesia. METHOD: Seventy-five ASA I-II male patients undergoing inguinal herniorrhaphy were randomly allocated into three groups. No premedication was given. Anaesthesia was induced with thiopental and tracheal intubation was facilitated by vecuronium in all groups. Anaesthesia was maintained with 0.8% halothane (Group I) (n = 25), 1% isoflurane (Group II) (n = 25), or 2% sevoflurane (Group III) (n = 25) and 66% nitrous oxide in oxygen. Three lead electrocardiogram recordings were taken before induction, 2, 5, 10, 15, 30 and 45 min after induction and after extubation. Heart rate, systolic, diastolic, mean arterial pressure and SpO2 were recorded at the same time. Heart rate and corrected QT interval were evaluated by using Bazett's formula. Multivariate analysis of variance for repeated measures was used to determine intergroup and intragroup differences. RESULTS: There was no statistically significant difference in the baseline QTc values of the groups. There was no difference between QTc values with halothane and sevoflurane. There was a difference between QTc values with isoflurane and those with the other two inhalation anaesthetics (P < 0.05). Although QTc values in the isoflurane group were higher at all times, the critical value of 440 ms was not exceeded. CONCLUSION: We conclude that halothane 0.8%, isoflurane 1% and sevoflurane 2% do not prolong QTc interval.     

The efficacy of clonidine for reducing perioperative haemodynamic changes and volatile anaesthetic requirements in children

Background: Oral clonidine given as a premedicant in adults has been shown to reduce intraoperative inhalation anaesthetic requirements and provide perioperative haemodynamic stability. We conducted the current study to ascertain whether or not these beneficial effects of clonidine can be reproduced in children. Methods: In a prospective, randomized, double-blind, controlled clinical trial, 60 children (ASA I) aged 5–11 yr, received placebo (control), 2 μg kg^-1 clonidine, or 4 μg kg^-1 clonidine orally 105 min before induction of anaesthesia. Anaesthesia was induced with halothane, nitrous oxide in oxygen via mask and maintained with halothane and 60% nitrous oxide in oxygen. The halothane concentration was titrated to the concentration required to maintain haemodynamic stability (defined as 20% of blood pressure (BP) and heart rate (HR)) for maintenance of anaesthesia. The end-tidal concentration of halothane was monitored throughout anaesthesia. On completion of surgery, nitrous oxide and halothane were discontinued. Following confirmation of recovery from anaesthesia and muscle relaxation, the endotracheal tube was removed. Results: Higher inspired concentrations of halothane (%) were required in the control and 2 μg kg^-1 clonidine-treated groups (mean SD: 1.1 ±0.2 and 1.0±0.2, respectively) than in the 4 μg kg^-1 clonidine-treated group (0.6±0.1) for haemodynamic stability (P<0.05). Clonidine, 4 μg kg^-1, significantly reuced the intraoperative lability (coefficient of variation) of systolic and diastolic BP and HR compared with the other two regimens. Conclusion: Oral clonidine premedication at a dose of 4 μg kg^-1 provided intraoperative haemodynamic stability and reduced anaesthetic requirements in children. However, we are unable to extrapolate these observations to younger children and infants.     

The effect of clonidine on sevoflurane requirements for anaesthesia and hypnosis

We evaluated the effects of clonidine given orally on sevoflurane requirements for anaesthesia and hypnosis. Patients received either clonidine (5 μg.kg⁻¹) by mouth ( n  =21) 90 min before surgery or no premedication ( n  =21) by random allocation. MAC was calculated using repeated tetanic nerve stimulation with end-tidal sevoflurane concentration increased or decreased by 0.3 vol.% depending on the previous response. MAC awake was calculated according to the response to verbal command. The mean (SD) MAC in the clonidine-treated patients was 1.53 (0.20)% compared with 1.83 (0.15)% in the control group (p <0.001). Similarly, MAC awake was reduced in the clonidine group (0.50 (0.08)% compared with 0.60 (0.07)% in the control group) (p <0.001). We conclude that clonidine 5 μg.kg⁻¹ orally administered pre-operatively reduces sevoflurane requirements for anaesthesia and hypnosis.     

TRANSCRANIAL DOPPLER SONOGRAPHY: EFFECTS OF HALOTHANE, ENFLURANE AND ISOFLURANE ON BLOOD FLOW VELOCITY IN THE MIDDLE CEREBRAL ARTERY

Systolic, diastolic, and mean blood flow velocity in the middlecerebral artery (Vs,mca; Vd,mca; Wm,mca) and pulsatility (Vs- Vd)/Vm of the waveform obtained were recorded in 51 patientsbefore, during and after general anaesthesia. Transcranial Doppler(TCD) sonographic variables were measured in the awake patientand after induction of anaesthesia with thiopentone 5–6mg kg^–1. After tracheal intubation, 17 patients received0.8% halothane and 66% nitrous oxide in oxygen for 30 min (15minnormoventilation; 15min hyper-ventilation). The inspired halothaneconcentration was then increased to 1.6% for 45min (15min normoventilation;15 min hyperventilation; 15 min normoventilation with nitrousoxide replaced by oxygen). Enflurane (1.7% for 30 min and 3.4%for 45 min) was given to another 17 patients; 17 other patientsreceived isoflurane (1.2% and 2.4%). Mean arterial pressure(MAP), nasopharyngeal temperature, end-tidal carbon dioxideconcentration, inspired and end-tidal anaesthetic agent concentrations,haemoglobin concentration, PVC and TCD variables were measuredat the end of each 15 min period. After recovery from anaesthesia,TCD variables were measured again. There were no intergroupdifferences in changes in MAP, nasopharyngeal temperature, haemoglobinconcentration and PCV. Halothane, enflurane and isoflurane atlow doses and normoventilation had little influence on TCD variablescompared with awake values. In large concentrations with nitrousoxide in oxygen and normoventilation, there were differencesbetween the volatile agents. Halothane increased blood flowvelocities, but enflurane and isoflurane caused little change.Hyperventilation always decreased blood flow velocities andincreased pulsatility. Six of 17 patients undergoing hyperventilationwith 2.4% isoflurane and nitrous oxide in oxygen showed zerodiastolic flow. This phenomenon was not observed in any patientreceiving halothane or enflurane. With high doses of the volatileagents and normoventilation, blood flow velocities decreasedin all groups after discontinuation of nitrous oxide. Our TCDresults are compatible with the known effects of halothane,enflurane and isoflurane on cerebral blood flow (CBF). However,the relative changes in blood flow velocity and CBF may notbe proportional with large doses of volatile agents, as a constantdiameter of basal cerebral arteries may not be assumed underthese conditions.     

Recovery characteristics of sevoflurane or halothane for day-case anaesthesia in children aged 1-3 years

BACKGROUND: Our objective was to compare the recovery characteristics of sevoflurane and halothane for short day-case anaesthesia in a specifically limited age group of children 1-3 yr. METHODS: Eighty unpremedicated children undergoing day-case adenoidectomy were randomly assigned to receive inhalational induction with either sevoflurane 8% or halothane 5% and nitrous oxide in oxygen (70/30) via a face mask. Tracheal intubation was performed without a muscle relaxant. Anaesthesia was continued with the volatile anaesthetic, adjusted to maintain heart rate and blood pressure within +/-20% of initial values. Recovery was evaluated using a modified Aldrete score, a Pain/Discomfort scale and by measuring recovery end-points. A postoperative questionnaire was used to determine the well-being of the child at home until 24 h after discharge. RESULTS: Emergence and interaction occurred significantly earlier after sevoflurane than halothane but discharge times were similar. More children in the sevoflurane group achieved full Aldrete scores within the first 30 min after anaesthesia, although this group suffered more discomfort during the first 10 min. The amount of postoperative analgesic administered was higher and the first dose given earlier in the sevoflurane group. Postoperative vomiting was more common with halothane, but side-effects in the two groups were otherwise similar in the recovery room and at home. CONCLUSIONS: In children 1-3 yr, sevoflurane provided more rapid early recovery but not discharge after anaesthesia of <30-min duration. Apart from more vomiting with halothane and more discomfort during the first 10 min after awakening with sevoflurane, the quality of recovery was similar with the two anaesthestics.