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PubMed1991

A system model for closed-circuit inhalation anesthesia. II. Clinical validation.

Recently, we described a basic model and its more elaborate variants to predict the uptake and distribution of inhalational anesthetics during closed-circuit anesthesia. As an initial clinical validation of the linear, continuous, 14-compartment basic model, the current study examined its predictive performance in 50 patients by comparing quantitatively the predicted and the measured alveolar concentration-time profiles after bolus injections of liquid isoflurane into the closed system during mechanical ventilation. The two versions of the model studied differed in the size of their peripheral shunt, as 0% (version A) and 16% (version B) of the cardiac output. A total of 15,744 alveolar concentrations of isoflurane (one per 10s period) were measured by mass spectrometry. For each measured concentration we used computer simulations of version A and version B to calculate a predicted concentration for both versions. For each patient we calculated the bias (indicating over- or underprediction) and the scatter of the prediction errors (indicating the typical error size). The bias and the scatter of the prediction errors, both given as mean (and standard deviation), were 2.25 (13.59) and 12.51 (5.84)% for version A and 12.00 (14.97) and 14.12 (6.54)% for B. Version A performed better than B: both the bias (P = 0.008) and the scatter (P less than 0.0001) were closer to zero for A. Logistic regression analysis showed for version A that scatter, but not bias, increased with age (P = 0.002). Gender, body mass index (weight x height-2), and number of injections per hour did not influence scatter or bias.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Sedation during regional anesthesia: inhalation versus intravenous.

PURPOSE OF REVIEW: Sedation of patients either with or without regional anesthesia is discussed to ascertain sedation requirements in the two groups. The differences between 'monitored anesthesia care' and conscious sedation are defined. Several current and promising methods with which we can evaluate a patient's degree or level of sedation are assessed. Also noted are safety concerns regarding monitoring solutions for patients undergoing monitored anesthesia care. Well established techniques, including some which are decidedly 'low tech', are examined. Several routes of intravenous administration are discussed along with patient variables. Sevoflurane sedation is mentioned with regards to administration, advantages and drawbacks. RECENT FINDINGS: Several modalities have been studied for evaluation of a patient's level of sedation, some of which have little applicability in the operating room. Processed electroencephalographic monitoring has tremendous promise but is currently not reliable enough to assess sedation level. Sevoflurane has a role in sedation, providing the limitations are understood. One drawback of sevoflurane is its greater degree of disinhibition when compared with intravenous agents, necessitating conversion to general anesthesia. SUMMARY: Evaluating the degree of patient sedation is a need that technology has yet to meet. Several techniques have been tried in intensive care units but have little utility in the operating room. Utilization of processed electroencephalogram waveforms has the greatest potential but is of limited value at the present time. Sevoflurane is demonstrated to have a limited role in sedation but may prove useful in specific circumstances.

Journal Article↗
PubMed1998

Cardiorespiratory effects of low-flow and closed circuit inhalation anesthesia, using sevoflurane delivered with an in-circuit vaporizer and concentrations of compound A.

OBJECTIVES: To determine the concentrations of sevoflurane and compound A (a degradation product of sevoflurane) in the anesthetic circuit when sevoflurane was delivered with an in-circuit vaporizer, and to determine the cardiorespiratory effects of sevoflurane in dogs. ANIMALS: 6 mixed-breed dogs. PROCEDURE: In-circuit vaporizers were connected to the inspiratory limb of a circle rebreathing system connected to a ventilator. A reservoir bag was attached to the Y-piece connector to act as an artificial lung, and sevoflurane concentrations in the anesthetic circuit were measured at vaporizer settings of 1, 3, 5, 7, and 10 and oxygen flow rates of 250 and 500 ml/min. Cardiorespiratory effects of sevoflurane were determined in dogs while they were breathing spontaneously, during controlled ventilation, and during closed circuit anesthesia. Concentrations of compound A were determined by means of gas chromatography with flame ionization. RESULTS: The concentration of sevoflurane in the anesthetic circuit increased with vaporizer setting and time. For oxygen flow rates of 250 and 500 ml/min, vaporizer settings between 5 and 7 and between 7 and 10, respectively, produced sevoflurane concentrations closest to values reported to produce surgical anesthesia in dogs. Significant differences were not observed in cardiorespiratory variables with time or among anesthetic conditions. Concentrations of compound A in the anesthetic circuit were less than values reported to produce renal toxicoses and death in rats. CONCLUSION: Results suggested that sevoflurane can be administered to nonsurgically stimulated dogs, using an in-circuit vaporizer and low (< 15 ml/kg/min) oxygen flow rates, without causing significant cardiorespiratory depression or clinically important concentrations of compound A.

Anesthesia, Closed-Circuit↗
PubMed1996

[Sevoflurane or halothane in inhalational anesthesia induction in childhood. Anesthesia quality and fluoride level].

UNLABELLED: Due to its low blood:gas partition coefficient (0.69) and its neutral odor, sevoflurane (S) is suitable for inhalational induction of anaesthesia. At the moment halothane (H) is preferentially used for this purpose due to its non-irritating odor and the smoothness of anaesthetic action. However, experience is limited with the use of S in children, and concern exists about potential renal toxicity of its metabolite, i.e. fluoride. Therefore, we compared S and H in an open, randomized phase III trial. MATERIAL AND METHODS: With approval of the ethics committee and written informed parental consent, 40 children (age 1-10, mean 5.3 years, ASA class I and II) had anaesthesia induced without premedication (fresh gas flow 6 l/min, N2O/O2 = 65/35). Concentration of volatile anaesthetics was increased every 3-5 breaths (S: 0.8...3.2 vol%, H: 0.4...1.6 Vol%). The ciliary reflex was tested until it disappeared. Airway reflexes and excitation were quantified using a score. Upon venipuncture, relaxation and intubation, anaesthesia was maintained with S (Fi: 2.4 vol%) or H (Fi: 1.2 vol%) in N2O/O2 (3 l/min, etCO2 35-38 mm HG). Alfentanil was supplemented in repeated doses of 20 micrograms/kg. ECG, NIBP, SpO2, Fi and Fet of CO2 and volatile anaesthetics were continuously recorded. At the end of surgery anaesthetics were terminated abruptly and fresh gas flow was increased to 6 l/min O2. Time to the first purposeful movement was registered. Serum fluoride levels were determined immediately after venipuncture, at the end of surgery and 70 min later. Time to possible discharge from the PACU was quantified using a modified Aldrete score. Data were analysed with descriptive methods, Student's t-test or non-parametric tests as appropriate. RESULTS: Groups did not differ with respect to age, weight, sex, or type of surgery. Total dose of anaesthetics was 1.60 MACxh for S and 1.77 MACxh for H (p = 0.68). Table 6 shows the essential data. Mean arterial blood pressures and heart rate remained within +/- 20% of age-related normal values (Table 7). Mean serum fluoride level was 23.1 +/- 1.2 mumol/l at the end of surgery and decreased to 18.6 +/- 0.970 min later (Fig. 3). CONCLUSIONS: Sevoflurane is an alternative to halothane in pediatric inhalational anaesthesia, with a comparable, low incidence of airway irritation and smoothness of induction. Because of the significantly faster induction and recovery it seems superior to halothane. With the fluoride levels measured, an impairment of renal function is unlikely.

Anesthesia Recovery Period↗
PubMed2003

[Standing behavior in horses after inhalation anesthesia with isoflurane (Isoflo) and postanesthetic sedation with romifidine (Sedivet) or xylazine (Rompun)].

Isofluorane is a modern, only slightly depressive inhalation anaesthetic with excellent pharmacologic characteristics in use in equine medicine. In contrast to halothane, isofluorane is hardly broken down in the liver, but is eliminated by the lung. It low solubility in blood permits excellent control of anaesthesia. However, due to its swift elimination from the organism there is heightened risk of premature recovery from isofluorane anaesthesia. In this study the recovery phases of 96 horses were monitored for its duration and the animals' physical coordination. The horses were divided into four groups. Two groups were sedated with xylazine, one of which received postanaesthetic sedation with xylazine, the other saline solution only. The other two groups were sedated with romifidine, either with or without postanaesthetic sedation after general anaesthesia. In this study the horses of Group 4, sedated with 0.02 mg/kg BW romifidine at the moment of extubation, showed the best recovery phase. The number of attempts to arise was reduced and coordination was better. Similar results were obtained by postanaesthetic sedation with 0.2 mg/kg BW xylazine (Group 2). Premedication with 0.08 mg/kg BW romifidine without postanaesthetic sedation (Group 3) could be carried out at mean duration of anaesthesia of 85 minutes with no negative effects observed during the recovery period. Premedication with xylazine without postanaesthetic sedation (Group 1) is not to be recommended, as the number of attemps to stand up was significantly higher and coordination was either weak or significantly poorer than in the other three groups. The results of this study show that post-anaesthetic sedation of horses with an alpha 2-adrenoceptor agonist can improve the recovery phase after inhalant anaesthesia with isofluorane in regard to the number of attempts to arise and the animals' physical coordination.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

[Inhalation anesthesia with halogen-containing anesthetics in children].

The study was carried out in 158 children aged 3-16 years operated on in an inpatient setting. The patients were divided into 3 groups with different types of induction narcosis: 1) ethrane inhalation up to 3 vol% and N2O with O2 in 1:1 ratio (56 pts); 2) fluothane up to 3.5 vol% and N2O with O2 in 2:1 ratio (87 pts), and 3) isoflurane inhalation up to 3 vol% and N2O with O2 in 1:1 ratio (15 children). Central hemodynamics, cardiointervalograms, and external respiration function were studied. Ethrane and isoflurane induction was longer (4-12 min) than fluothane induction (3-5 min). Anesthesia with ethrane and isoflurane in combination with N2O with O2 led to a less pronounced reaction of the central hemodynamics than fluothane anesthesia, which led to a decrease of the sympathic tone and increase in the activity of the parasympathetic component of the autonomic nervous system. Analyzing a vast scope of clinical material on the use of inhalation anesthetics and all the pros and contras, the authors conclude that inhalation anesthetics can be used in children.

Adolescent↗
PubMed1999

Hydroxyl radical formation during inhalation anesthesia in the reperfused working rat heart.

PURPOSE: To determine whether isoflurane, sevoflurane and halothane influenced hydroxyl radical production in the ischemic rat heart. METHODS: Twenty-four male Wistar rats were divided into four groups; control (C), isoflurane 1.4% (I), sevoflurane 2.5% (S) and halothane 1% (H). The hearts were perfused with modified Krebs-Henseleit bicarbonate buffer by a working heart model for 10 min. Then, whole heart ischemia was induced by severely restricting coronary perfusion for 15 min. Reperfusion of the hearts after this ischemic period lasted for 20 min. The coronary effluent was collected before and during ischemia and at 1, 5, 10, 20 min after reperfusion. At the end of reperfusion, hearts were removed and prepared for measurement. Hydroxyl radicals were identified by their reaction with salicylic acid to yield dihydroxybenzoic acids (DHBAs). RESULTS: Before and after ischemia, there were no differences in coronary flow and heart rate among the four groups, but cardiac output and LV dP/dt maximum in the anesthetic groups were lower than in the control group. Hydroxyl radical products in the heart were significantly lower in the I group than the other groups (e.g. C vs I, 278.1 +/- 24.3 vs 219.3 +/- 14.4 microM x g(-1), P < 0.05). The concentrations of DHBAs in the coronary effluent at some points in the I and H groups were less than in the C and S groups. CONCLUSION: These results indicate that isoflurane and halothane (to a lesser extent), reduce hydroxyl radical production in the ischemic heart, but sevoflurane does not.

Anesthetics, Inhalation↗
PubMedDate not supplied

[Non-inhalation anesthesia with preservation of spontaneous breathing in emergency surgery in children].

A total of 320 patients with acute abdominal surgical pathology were examined after general anesthesia with combined intravenous injection of sodium hydroxybutyrate and calypsol, with spontaneous respiration preserved. The examinations were performed under clinical control and impedance plethysmography. The combination of the above anesthetics has a lot of advantages over calypsol mono-anesthesia and ensures adequate blockade of visceral innervation. A slight circulatory hyperdynamia has been observed. This type of analgesia is one of the optimal methods of general anesthesia in children.

Adolescent↗
PubMedDate not supplied

[Closed circuit inhalation anesthesia. Consumption and cost].

Closed circuit anaesthesia (CCA) and minimal flow anaesthesia diminish inhalatory anaesthetic consumption. Consumption of inhalatory anaesthesia was calculated using two different techniques: CCA and "non rebreathing" system. Costs were compared on the basis of the official list price. The CCA allowed for reduced consumption at lower costs. The resulting annual savings are equal to one third of the total price of the whole apparatus with its complementary monitoring and control systems.

Anesthesia, Closed-Circuit↗
PubMed1992

[Inhalation anesthesia in low-flow systems. Clinical evaluation of the kinetics of isoflurane in induction phase].

Closed circuit and low flow anaesthesia offer numerous advantages such as reduction of gas consumption, low cost, and less pollution in both the operating theatre and the environment. These procedures also offer increases in inspired gas humidity and temperature. However the time needed to attain the alveolar concentration MAC 95, is too long. Prefilling the whole circuit, the bellow and the bag with anaesthetic vapours shortens that time without overdosage.

Anesthesia, Closed-Circuit↗
PubMed1987

[Inhalation anesthesia or "balanced anesthesia"? A comparative perioperative study in geriatric patients].

During a prospective randomized trial, 50 geriatric patients underwent surgery for a fractured femoral neck. The perioperative circulatory and respiratory effects of anesthesia with enflurane or balanced anesthesia with enflurane and fentanyl were compared. We were particularly looking for postoperative respiratory depression after a standard dose of fentanyl given during balanced anesthesia. Method. In 25 patients anesthesia was induced with 0.2 mg/kg etomidate and 1 mg/kg succinylcholine and maintained with 0.15 mg/kg alcuronium and enflurane. Twenty-five patients received a additional dose of 5 micrograms/kg fentanyl divided into 0.1 mg/kg 2 min before endotracheal intubation and the remainder 5 min before the start of surgery. Systolic and diastolic arterial pressures, heart rate, central venous pressure, hemoglobin, hematocrit, and electrolytes were measured and arterial blood gases were analyzed. Results. There was no important difference between the two methods: during careful use of both techniques circulation remained stable. No marked postoperative respiratory depression occurred even after 5 micrograms/kg fentanyl. Conclusions. Both anesthetic procedures are suitable for hip surgery in elderly patients. In the early postoperative period geriatric patients should be observed carefully in the recovery room for at least 2 h. In some patients--especially if fentanyl is used intraoperatively--this time must be prolonged.

Aged↗