Clinical evaluation of low-flow sevoflurane anaesthesia for paediatric patients

Background: Sevoflurane expenditure, inspired gas humidity, temperature, soda lime temperature, and compounds A and B were measured during high and low fresh gas flow anaesthesia in paediatric patients. Methods: Sixty ASA 1 or 2 paediatric patients were randomly allocated to two groups: low-flow circle anaesthesia (LFA) patient group (n=30) and high-flow circle anaesthesia (HFA) patient group (n=30). Initial fresh gas flow (FGF) was 4 l · min^?1 of nitrous oxide and 2 l · min^?1 of oxygen in both groups. This FGF of 6 l · min^?1 was maintained in the HFA group. After 10 min of HFA, the FGF was reduced to 600 ml · min^?1 (nitrous oxide and oxygen 300 ml · min^?1 each) in the LFA group. Results: Sevoflurane expenditure during LFA was about 1/7 of that during HFA (3.3±0.2 ml · h^?1 · vol.%^?1 compared to 22.8±0.6 ml · h^?1 · vol.%^?1, mean±SEM, respectively). Absolute humidity in the LFA patients was 4 times higher than that in the HFA patients (22.8±2.4 g · m^?3, 5.6±3.4 g · m^?3 respectively). There was no significant difference in the inspiratory gas temperature between the LFA (28.5±0.6°C) and HFA (26.9±1.3°C) groups. There was significant difference in the mean highest soda lime temperature between the LFA (35.5±1.2°C) and HFA (28.7±1.2°C) groups. The mean highest concentration of compound A was 12.2±3.8 ppm in the LFA group. The mean highest concentration of compound B was less than 1 ppm. Compounds A and B were below detectable level in the HFA group. Conclusion: In conclusion, sevoflurane used for paediatric patients in a circle system with a fresh gas flow of 0.6 l · min^?1 resulted in a significantly reduced sevoflurane expenditure, higher inspired absolute humidity, but not temperature, compared to a fresh gas flow of 6 l · min^?1. Low levels of compounds A and B were detected.     

Gaseous homeostasis during low-flow anaesthesia

The object of this clinical study was to investigate the circle system gas homeostasis during low-flow anaesthesia using a technique designed to keep a constant inspired oxygen fraction of 0.30. Denitrogenation was adequately accomplished with mask preoxygenation, 10 l/min, for 1 min and an initial fresh gas flow of 5 l/min for 6 min after intubation. There was no need to wash out accumulated nitrogen at intervals, since the already low nitrogen concentration in the system tended to decrease after 1 h. The fresh gas flow of nitrous oxide to oxygen ratio and the inspiratory to end-expiratory oxygen concentration difference both reflected the uptake of nitrous oxide. The calculated rates of uptake of nitrous oxide, a subject of controversy, were in accordance with those found by Severinghaus and Barton & Nunn.     

Comparison of plasma α glutathione S-transferase concentrations during and after low-flow sevoflurane or isoflurane anaesthesia

BACKGROUND: We evaluated the effect of low-flow sevoflurane anaesthesia, in which compound A is generated, and isoflurane anaesthesia, in which compound A is not generated (n=13 in each group), on hepatocellular integrity using alpha glutathione S-transferase (GST). Alpha GST is a more sensitive and specific marker of hepatocellular damage than is aminotransferase activity and correlates better with hepatic histology. METHODS: Sevoflurane or isoflurane were delivered without nitrous oxide with a fresh gas flow of 1 l/min. Concentrations of compound A in the circuit were measured hourly, and plasma alpha GST concentrations were measured perioperatively. RESULTS: Mean duration of anaesthesia was 338+/-92 min in the sevoflurane group and 320+/-63 min in the isoflurane group. Mean compound A concentration in the sevoflurane group was 28.6+/-9.0 ppm. There was no significant difference in alpha GST concentrations between the sevoflurane and isoflurane groups during or after anaesthesia. CONCLUSION: These results indicate that low-flow sevoflurane and isoflurane anaesthesia have the same effect on hepatic function, as assessed by plasma alpha GST concentrations.     

The uptake of sevoflurane during anaesthesia

The rate of uptake of sevoflurane during clinical anaesthesia (1.3 MAC) was measured by computer-controlled injection of liquid anaesthetic into a closed breathing system. The cumulative uptake of sevoflurane was 4.8 ml, 7.4 ml. 9.5 ml and 11.5 ml at 30, 60, 90 and 120 min, respectively. The ratio of inspired to end-expired sevoflurane was greater than similar measurements we have made for desflurane in the past, but the absolute rate of sevoflurane uptake was less than the rate of uptake of desflurane in these cases. The rate of uptake was equivalent to 0.59e^{−0.32 t}  + 0.039e^{−0.036 t}  + 0.105e^{−0.0034 t}  mlmin⁻¹ liquid sevoflurane. Plasma urea and creatinine measured on the first postoperative day were not significantly different from pre-operative values.     

Compound A, formaldehyde and methanol concentrations during low-flow sevoflurane anaesthesia: comparison of three carbon dioxide absorbers

Aim: To determine compound A, formaldehyde and methanol concentrations in low‐flow anaesthesia using different carbon dioxide absorbers. Methods: Fifteen patients scheduled for general or urological surgery were exposed to low‐flow (500 ml/min) anaesthesia with sevoflurane. The patients were randomly allocated to three groups: soda lime, DrägerSorb Free^® or Amsorb Plus^®. The concentrations of compound A, formaldehyde and methanol were sampled and analysed from the limbs of the anaesthesia circuit at T30 (30 min after the start of low‐flow sevoflurane anaesthesia), T90 (90 min) and T150 (150 min). The temperatures of the absorbers were measured at the same time. Results: Statistically significant differences (P < 0.05) were found in the production of compound A from soda lime (with the highest values), DrägerSorb Free^® and Amsorb Plus^® at each measurement time. Only traces of methanol (ranging from < 0.131 to 3.799 mg/m³) were measured, higher with Amsorb Plus^® (statistically significant differences were found only at T90). The formaldehyde values (ranging from < 0.1227 to 17.79 mcg/m³ p.p.b.) were higher with soda lime, and the difference was statistically significant at T150 and, in the inspiratory limb only, at T90. The temperatures of the absorbers were higher for soda lime and lower for Amsorb Plus^®; the difference was statistically significant at T0 in the upper canister and at T30 in both canisters. Conclusion: The concentrations of harmful products in the circuit were negligible and were lower using the new‐generation absorbers. Using Amsorb Plus^®, the temperatures in the canisters were lower than with the other two absorbers.     

低流量七氟烷吸入麻醉时不同二氧化碳吸收剂环路中化合物A浓度的比较及其对患者肝肾功能的影响

Objective To investigate the influence of different carbon dioxide (CO2) absorbents (Dr(a)gersorb 800 plus , Sodasorb,Sodasorb LF) on the production of compound A during low-flow sevoflurane anesthesia.Methods Twenty-seven ASA Ⅰ or Ⅱ patients aged 20-64 years were randomly assigned to three groups according to different CO2 absorbents: Dr(a)gersorb 800 plus' group (group D, n = 10), Sodasorb group (group S, n = 10) and Sodasorb LF group (group LF, n = 7). Anesthesia was maintained with low-flow (500 ml/min) sevoflurane inhalation (with the end-tidal sevoflurane concentration of approximately 2% ). At 2 h after low-flow sevoflurane anesthesia, gas samples were taken from the expiratory limb of the circuit. Compound A was detected by gas chromatography. Serum alanine transaminase (ALT), aspartate aminotransferase (AST), bilirubin (BR), urea nitrogen (BUN) and creatinine (Cr) levels were measured before (T0 ) and 24 h after operation (T1).Results The three groups were comparable with respect to age, body weight and height. After 2 h of low-flow sevoflurane anesthesia, compound A concentrations in the expiratory limb of the circuit were 11.6 ± 5.8 (group D), 2.1 ± 1.9 (group S)and ＜ 0.1 ppm (group LF), respectively. There were no significant changes in the serum ALT, AST, BR, BUN and Cr levels at 24 h after operation as compared with the preoperative baseline values in the three groups.Conclusion After 2 h of low-flow (500 ml/min) sevoflurane anesthesia, compound A concentrations within the circuit with different CO2 absorbents ( Dr(a)gersorb 800 plus' , Sodasorb, Sodasorb LF) are less than 50 ppm, with the lowest in Sodasorb LF.However, they have no significant effects on hepatic or renal function.     

Effects of sevoflurane, isoflurane, enflurane, and halothane on left ventricular diastolic performance in dogs

The effects of volatile anesthetics on active (ventricular relaxation) and passive (chamber stiffness) indices of diastolic function and on left ventricular filling rates in dogs were studied to determine how these agents affect left ventricular diastolic performance. Thirty-five mongrel dogs were randomly assigned to receive sevoflurane, isoflurane, enflurane, or halothane. Left ventricular pressure waveforms, phonocardiograms, and echocardiograms were recorded after administering the anesthetics at concentrations of 0% (control), 1%, 2%, and 3%. Ventricular relaxation was defined as the time constant of the decline in left ventricular pressure. Chamber stiffness was derived from the ventricular pressure-volume relationship during passive filling. Rapid filling rate, slow filling rate, and atrial filling rate were obtained from echocardiograms and phonocardiograms. No change in the time constant or in chamber stiffness was observed at any concentration of sevoflurane or isoflurane. However, the highest studied concentration of enflurane and halothane produced a significant increase in the time constant and in chamber stiffness. Rapid filling rate as well as atrial filling rate decreased significantly with the volatile anesthetics, especially with enflurane and halothane. Sevoflurane and isoflurane did not alter ventricular relaxation or chamber stiffness, but did affect diastolic function as manifested by their alteration of filling rates. In contrast, enflurane and halothane each prolonged ventricular relaxation and increased chamber stiffness. With the administration of the volatile anesthetics, the rapid filling rate decreased with the deterioration of diastolic function; in addition, atrial filling rates decreased and did not compensate for the reduction in early ventricular filling.     

Fluoride excretion in children after sevoflurane anaesthesia

Background. Defluorination of sevoflurane is catalysed by thehepatic enzyme cytochrome P450 2E1 (CYP2E1). Data about theontogenesis (developmental variations in activity) of this enzymesuggest a low metabolism of sevoflurane during the first monthsof life. Methods. To test this hypothesis, 45 children less than 48 monthsof age undergoing sevoflurane anaesthesia were enrolled in aprospective open clinical trial. The 24 h urine fluoride excretionwas measured in five groups of children (A, <4 months; B,4 to <8 months; C, 8–12 months; D, >12–24months; and E, >24–48 months old). An index of sevofluranemetabolism (ISM) was calculated as the ratio of fluoride excretion,cumulative expiratory sevoflurane concentrations measured everyminute during anaesthesia, and body surface area. ISM valueswere median (IQ 25–75%). Results. ISM was lower in group A (n=9, 18.9 (11.2–29.5)than group C (n=11, 44.2 (37.5–53.5), P<0.05), groupD (n=7, 52.6 (45.8–68.4), P<0.01) and group E (n=9,53.6 (50.7–85), P<0.001). Median ISM expressed as afunction of median age, exponentially increased with a rapidincrease during the first months of life, followed by a slowerincrease after 10 months of age. Conclusion. These results suggest that, in children less than48 months, sevoflurane metabolism parallels postnatal developmentof CYP2E1. Br J Anaesth 2002; 89: 693–6     

Alveolar integrity and ultrastructure in pigs remain undamaged after exposure to sevoflurane

Previous studies have shown that both halothane and isoflurane have adverse but reversible effects on alveolar physiology. The present study was designed to test the hypothesis that also sevoflurane may affect alveolar integrity.
Fifteen pigs were randomly selected to receive either thiopentone infusion (control group, n=8) or sevoflurane (n=7) at 4.0% inspiratory concentration (1.5 MAC) in air for 6 h. Tissue samples from the lungs were obtained at the end of the experiment. Both histopathological light microscopy and electron microscopy were used to assess the structural integrity of the alveoli.
Pulmonary hemodynamics were comparable in both groups. Light microscopy showed no difference between the groups in the amount of alveolar macrophages, red blood cells or edema. Electron microscopy showed minor changes such as moderate local swelling of alveolar epithelium in both study groups. Alveolar type II cells were ultrastructurally unaltered in both study groups.
We conclude that long-term, high concentration exposure to sevoflurane has no detrimental effect on the alveolar integrity in pigs.     

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.     

A review of recovery from sevoflurane anaesthesia: comparisons with isoflurane and propofol including meta-analysis

BACKGROUND: Sevoflurane has a lower blood:gas partition coefficient than isoflurane and thus should be associated with a more rapid recovery from anaesthesia. METHODS: A review and meta-analysis were employed to examine the recovery profiles of adult patients following anaesthesia, comparing sevoflurane to isoflurane and sevoflurane to propofol. RESULTS: There were significant differences in times to several recovery events that favoured sevoflurane to isoflurane anaesthesia, including time to emergence, response to commands, extubation, and orientation. Likewise, there were significant differences in times to the same recovery events following anaesthesia with sevoflurane versus propofol. There were no differences in time to recovery room discharge when comparing sevoflurane to isoflurane or propofol. CONCLUSION: The observed differences between sevoflurane and isoflurane or propofol anaesthesia support the postulate that the use of sevoflurane is associated with a more rapid recovery from anaesthesia than either isoflurane or propofol.     

The comparative effect of single dose mivacurium during sevoflurane or propofol anesthesia in children

BACKGROUND: We aimed to randomly compare intubating conditions, recovery characteristics and neuromuscular effects of single dose of mivacurium (0.2 mg.kg(-1)) during sevoflurane vs. propofol anesthesia in 60 healthy children, undergoing inguinal surgery. METHODS: All children were randomly allocated to receive 2 mg.kg(-1) propofol iv or sevoflurane 8% inspired concentration for induction of anesthesia. Anaesthesia was maintained with 66% nitrous oxide in oxygen and 100-120 microg.kg(-1) propofol or sevoflurane approximately 2-3% inspired concentration with controlled ventilation. The ulnar nerve was stimulated at the wrist by a train-of four (TOF) stimulus every 20 s and neuromuscular function was measured at the adductor pollicis. When the response to TOF was stable, 0.2 mg.kg(-1) mivacurium was given. The trachea was intubated successfully at the first attempt in all patients. RESULTS: Onset time following a single dose of mivacurium was shorter in the sevoflurane group (2.99 min), than in the propofol group (4.42 min). The times to 25, 50, 75, and 90% recovery were significantly longer in the sevoflurane group (13.1, 15.7, 18.6, and 21.2 min, respectively) than in the propofol group (11.4, 13.2, 14.4, and 17.2 min respectively). TOF ratios of 50, 70, and 90% were significantly occurred later in sevoflurane group than propofol group. CONCLUSIONS: Our results indicate that when compared with propofol group, the sevoflurane group had an accelerated onset and a delayed recovery of neuromuscular block induced by mivacurium in children.     

Pulmonary mechanics during isoflurane,sevoflurane and desflurane anaesthesia

This study was designed to investigate the effects of desflurane on bronchial smooth muscle tone, following intubation and to compare these effects with isoflurane and sevoflurane. Patients were randomly divided into three groups to receive, isoflurane (n = 22), sevoflurane (n = 23), or desflurane (n = 22). Peak inspiratory pressure (PIP), respiratory resistance (Rr) and dynamic compliance (Cdyn) measurements were recorded at three time points; After the beginning of ventilation and before inhalation agent was started, following 5 min of ventilation with 1 MAC (minimum alveolar concentration) inhalation agent and following 5 min of 2 MAC inhalation agent. We found that all inhalation agents caused a significant decrease in Peak Inspiratory Pressure (PIP) and respiratory resistance (Rr), and an increase in dynamic compliance (Cdyn) at 1 MAC concentrations. When the agent concentration was increased to 2 MAC, desflurane caused a significant increase in Rr and PIP and a decrease in Cdyn. We concluded that desflurane, like isoflurane and sevoflurane, exhibits a bronchodilator effect at 1 MAC concentration. However, increasing the concentration to 2 MAC caused an increase in airway resistance with desflurane, whilst sevoflurane and isoflurane continued to have a bronchodilator effect.     

Convulsions associated with epidural analgesia during sevoflurane anaesthesia

A three-year-old girl who underwent an operation for adrenal neuroblastoma was anaesthetized with sevoflurane and epidural analgesia. In the immediate recovery period she had convulsions. The convulsions were successfully treated with thiopentone and sevoflurane, there were no neurological sequelae. The convulsions were considered to be a manifestation of mepivacaine toxicity because of a high plasma mepivacaine concentration. Complications of paediatric regional analgesia and manifestations of mepivacaine toxicity under sevoflurane anaesthesia are discussed.     

Effect of nitrous oxide on cerebrovascular reactivity to carbon dioxide in children during sevoflurane anaesthesia

Background. Sevoflurane and nitrous oxide have intrinsic cerebralvasodilatory activity. To determine the effects of nitrous oxideon cerebrovascular reactivity to carbon dioxide (CCO₂R) duringsevoflurane anaesthesia in children, middle cerebral arteryblood flow velocity (V_mca) was measured over a range of end-tidalcarbon dioxide concentrations (E'_CO2), using transcranial Doppler(TCD) ultrasonography. Methods. Ten children aged 1.5–6 yr were anaesthetizedwith sevoflurane and received a caudal block. Patients wereallocated randomly to receive either air–nitrous oxideor nitrous oxide–air. Further randomization determinedthe sequence of E'_CO2 (25, 35, 45, and 55 mm Hg) and sevoflurane(1.0 then 1.5 MAC or 1.5 then 1.0 MAC) concentrations. Oncesteady state had been reached, three measurements of V_mca, meanarterial pressure (MAP), and heart rate (HR) were recorded. Results. Cerebrovascular carbon dioxide reactivity was reducedin the 25–35 mm Hg E'_CO2 range on the addition of nitrousoxide to 1.5 MAC, but not 1.0 MAC sevoflurane. A plateau inCCO₂R of 0.4–0.6% per mm Hg was seen in all groups betweenE'_CO2 values of 45 and 55 mm Hg. Mean HR and MAP remained constantthroughout the study period. Conclusions. Cerebrovascular carbon dioxide reactivity is reducedat and above an E'_CO2 of 45 mm Hg during 1.0 and 1.5 MAC sevofluraneanaesthesia. The addition of nitrous oxide to 1.5 MAC sevofluranediminishes CCO₂R in the hypocapnic range. This should be takeninto consideration when hyperventilation techniques for reductionof brain bulk are being contemplated in children with raisedintracranial pressure. Br J Anaesth 2003; 91: 190–5     

Early intravenous cannulation in children during sevoflurane induction

BACKGROUND: It has been shown that early placement of an intravenous line in children anesthetized with halothane is equally safe compared with later placement. Whether this is true of sevoflurane is not known. METHODS: Pediatric patients, age 1-18 years, undergoing elective general anesthesia via an inhalation induction were randomized to intravenous placement either 30 or 120 s following loss of lid reflex. Movement on intravenous placement and incidence of laryngospasm were determined. Difficulty with intravenous placement was recorded. RESULTS: Movement on intravenous placement was more prevalent in the early group than in the late group (P < 0.0001). There was no laryngospasm in the late group and eight cases in the early group (P < 0.004). Children who had laryngospasm were older (P < 0.02) and weighed more (P < 0.04). Older children in the early group were more likely to have significant movement. CONCLUSION: Following an inhalation induction with sevoflurane in children, movement with intravenous placement was greater, and the incidence of laryngospasm was higher, when the intravenous access was attempted 30 s rather than 120 s following loss of lid reflex. We recommend waiting two min following the loss of lid reflex before attempting intravenous placement in children receiving an inhalation induction with sevoflurane.     

Intraocular pressure more reduced during anesthesia with propofol than with sevoflurane: both combined with remifentanil

BACKGROUND: Short-acting anesthetic agents are suitable and commonly used in ocular surgery. Propofol and remifentanil are known to reduce intraocular pressure (IOP), but no information is available regarding the effects of sevoflurane combined with remifentanil on IOP. METHODS: Therefore, a prospective, randomized study was conducted to compare the effects on IOP of two different anesthetic techniques: one based on a total intravenous anesthesia with propofol (Group P, bolus 1.5-2.0 mg/kg, maintenance 3.0-7.0 mg/kg/h); and the other based on sevoflurane (Group S, inhalational induction, end-tidal concentration 0.7-1.2 vol.%). An infusion of remifentanil (10 microg/kg/h) was used with both techniques. In ASA I-III patients with normal IOP undergoing elective cataract surgery, using an applanation tonometer, IOP was measured contralateral to the operated eye at nine predefined time points before, during and after anesthesia. RESULTS: The two groups (n=20 each) were comparable with regard to demographic data and hemodynamic variables. Baseline IOP was 14.2+/-2.8 mmHg (Group P) and 14.1+/-2.4 mmHg (Group S; NS). During and following the induction of anesthesia, IOP was reduced in both groups. Intraocular pressure was significantly lower in Group P (6.0+/-3.2 mmHg) than in Group S (8.9+/-3.4 mmHg) during the induction of anesthesia. CONCLUSION: In patients undergoing cataract surgery under general anesthesia with tracheal intubation, anesthetic regimens with propofol as well as with sevoflurane, both combined with remifentanil, decrease IOP significantly. The decrease in IOP was significantly more pronounced in the propofol group than in the sevoflurane group.     

Comparison of ocular microtremor and bispectral index during sevoflurane anaesthesia

Background. A practical and reliable monitor of depth of anaesthesiawould be a major advance on current clinical practice. Noneof the present monitors is both simple to use and accurate.Ocular microtremor (OMT) is a physiological tremor that is suppressedby propofol in a dose-dependent manner. We studied OMT duringpropofol induction and nitrous oxide– oxygen–sevofluranemaintenance of anaesthesia in 30 patients, and compared OMTwith the bispectral index (BIS) as a predictor of response toverbal command. Methods. OMT was measured using the closed-eye piezoelectricstrain-gauge technique. OMT and BIS were measured at specifictimes during the anaesthetic, including at loss of consciousness,at end-tidal sevoflurane 1 and 2%, and at emergence. Results. OMT decreased significantly after induction, did notdecrease as end-tidal sevoflurane was increased from 1 to 2%,and increased at emergence in all patients. By logistic regression,OMT was more sensitive and specific than BIS in distinguishingthe awake from the anaesthetized state (OMT, 84.9 and 93.1%respectively; BIS, 75.7 and 69.0%). Conclusions. OMT is suppressed by sevoflurane and accuratelypredicts response to verbal command. OMT may be a useful monitorof depth of hypnosis. Br J Anaesth 2002; 89; 551–5