Abstract
Purpose
To descnbe the pharmacokinetic behaviour and practical aspects of low (0.5–1l· min−1) and minimal (0.25–0.5 l · min−1) flow anaesthesia.
Methods
A Medline search located articles on low flow anaesthesia, and computer simulated anaesthetic uptake models are used.
Principal findings
Most, 85–90%, of anaesthetists use high fresh gas flow rates during inhalational anaesthesia. Low/minimal flow anaesthesia with a circle circuit may avoid the need for in-circuit humidifiers, raise the temperature of inspired gases by up to 6°C, reduce cost by about 25% by reduction of fresh gas flows to 1.51· mm−1, and reduce environmental pollution with scavenged gas. Knowledge of volatile anaesthetic pharmacokinetic behaviour facilitates the use of minimal/low flow rates. Small amounts of nitrogen or minute amounts of methane, acetone, carbon monoxide, and inert gases in the circuit are of no concern, but the degradation of desflurane (to carbon monoxide by dry absorbent) and sevoflurane (to compound A by using a fresh gas flow of >2 l · min−1) must be avoided. With modem gas monitoring technology, safety should be no more of a concern than with high flow techniques.
Conclusion
The use of fresh gas flow rates of < 1l · min−1 for maintenance of anaesthesia has many advantages, and should be encouraged for inhalational anaesthesia with most modem volatile anaesthetics.
Résumé
Objectif
Décnre le comportement pharmacocinétique et les aspects pratiques de l’anesthésie à débit bas (0,5–01 L · min−1) et minimal (0.25–0,5 L · min−1).
Méthodes
Recherche sur Medline des articles publiés sur l’anesthésie à bas débit et étude sur des modèles anesthésiques d’absorption simulée par ordinateur.
Principales constatations
Pendant l’anesthésie inhalatoire, la plupart (85–90%) des anesthésistes utilisent des débits élevés de gaz frais. L’anesthésie à débit bas ou minimal en circuit fermé peut éliminer les humidificateurs intégrés au circuit, augmenter la température des gaz inpirés de 6°C, et réduire les coûts d’opération d’environ 25% (débit diminué à 1.5 L · min−1) tout en permettant l’épuration des gaz. Il est plus facile d’utiliser des débits bas ou minimaux si on connaît le comportement pharmacocinétique des anesthésiques volatils. Les petites quantités d’azote ou des quantités infinitésimales de méthane, d’acétone ou de gaz inertes dans le circuit n’ont rien d’inquiétant, mais la dégradation du desflurane (en monoxyde de carbone en présence d’un absorbant anhydre) et du sévoflurane (en composé A avec un débit de gaz frais >2 L · min−1) doit être évitée. Grâce à la technologie moderne de monrtorage des gaz. on doit se sentir autant en sécurité qu’avec les techniques à hauts débits.
Conclusion
Avec les anesthésiques volatils modernes, l’utilisation de débits aussi bas que I L· min−1 pour le maintien de l’anesthésie inhalatoire a plusieurs avantages et devrait être encouragée.
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References
Baker AB. Low flow and closed circuits (Editorial). Anaesth Intensive Care 1994; 22: 341–2.
Simionescu R. Safety of low flow anaesthesia. Circular 1986; 3: 7–9.
Abbott Laboratories Marketing Survey. American Society of Anesthesiologists 1994 Annual Meeting.
Cravero J, Suida E, Manzi DJ, Rice LJ. Survey of low flow anesthesia use in the United States. Anesthesiology 1996; 85: A995.
Andrews JJ. Inhaled anesthetic delivery systems.In: Miller RD (Ed.). Anesthesia, 3rd ed. New York: Churchill Livingstone Inc., 1990: 171–223.
Hawkes C, Miller D, Martineau R, Hull K, Hopkins H, Tierney M. Evaluation of cost minimization strategies of anaesthetic drugs in a tertiary care hospital. Can J Anaesth 1994; 41: 894–901.
Szocik JF, Learned DW. Impact of a cost containment program on the use of volatile anesthetics and neuromuscular blocking drugs. J Clin Anesth 1994; 6: 378–82.
Cotter SM, Petros AJ, Boré CJ, Barber ND, White DC. Low-flow anaesthesia. Practice, cost implications and acceptability. Anaesthesia 1991; 46: 1009–12.
Logan M, Farmer JG. Anaesthesia and the ozone layer. Br J Anaesth 1989; 63: 645–7.
Kleemann PP. Humidity of anaesthetic gases with respect to low flow anaesthesia. Anaesth Intensive Care 1994; 22: 396–108.
Bengtson JP, Sonander H, Stenqvist O. Preservation of humidity and heat of respiratory gases during anaesthesia — a laboratory investigation. Acta Anaesthesiol Scand 1987; 31: 127–31.
Henriksson B-Å, Sundling J, Hellman A. The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system. Anaesthesia 1997; 52: 144–9.
Eger EI III. Uptake and distribution.In: Miller RD (Ed.). Anesthesia, 3rd ed. New York: Churchill Livingstone Inc., 1990: 85–104.
Wolfson B. Closed circuit anaesthesia by intermittent injections of halothane. Br J Anaesth 1962; 34: 733–7.
Lowe HJ, Ernst EA. The Qualitative Practice of Anesthesia. Use of Closed Circuit. Baltimore/London: Williams and Wilkins, 1981.
Weir HM, Kennedy RR. Infusing liquid anaesthetics into a closed circuit. Anaesth Intensive Care 1994; 22: 376–9.
Lowe HJ, Viljoen JF. Nomogram for anaesthetic uptake. Anaesth Intensive Care 1994; 22: 374–5.
Eger EI II. New inhaled anesthetics. Anesthesiology 1994; 80: 906–22.
Hargasser S, Hipp R, Breinbauer B, Mielke L, Entholzner E, Rust M. A lower solubility recommends the use of desflurane more than isoflurane, halothane, and enflurane under low-flow conditions. J Clin Anesth 1995; 7: 49–53.
Weiskopf RB, Eger EI II. Comparing the costs of inhaled anesthetics. Anesthesiology 1993; 79: 1413–8.
Morita S, Latta W, Hambro K, Snider MT. Accumulation of methane, acetone, and nitrogen in the inspired gas during closed-circuit anesthesia. Anesth Analg 1985; 64: 343–7.
Roily G, Versichelen LF, Mortier E. Methane accumulation during closed-circuit anesthesia. Anesth Analg 1994;79: 545–7.
Straub JM, Hausdörfer. Accumulation of acetone in blood during long-term anaesthesia with closed systems. Br J Anaesth 1993; 70: 363–4.
Versichelen L, Roily G, Vermuten H. Accumulation of foreign gases during closed-circuit anaesthesia. Br J Anaesth 1996; 76: 668–72.
Fang ZX, Eger EI II, Laster MJ, Chortkoff BS, Kandel L, Ionescu P. Carbon monoxide production from degradation of desflurane, enflurane, isoflurane, halothane, and sevoflurane by soda lime and Baralyme®. Anesth Analg 1995; 80: 1187–93.
Fang ZX, Eger EI II. Factors affecting the concentration of Compound A resulting from the degradation of sevoflurane by soda lime and Baralyme® in a standard anesthetic circuit. Anesth Analg 1995; 81: 564–8.
Bito H, Ikeda K. Long-duration, low-flow sevoflurane anesthesia using two carbon dioxide absorbents. Anesthesiology 1994; 81: 340–5.
Frink EJ Jr. Toxicologic potential of desflurane and sevoflurane. Acta Anaesthesiol Scand 1995; 39: 120–2.
Bito H, Ikeda K. Closed-circuit anesthesia with sevoflurane in humans. Effects on renal and hepatic fonction and concentrations of breakdown products with soda lime in the circuit. Anesthesiology 1994; 80: 71–6.
Bito H, Ikeda K. Renal and hepatic function in surgical patients after low-flow sevoflurane or isoflurane anesthesia. Anesth Analg 1996; 82: 173–6.
Bito H, Ikeda K. Effect of total flow rate on the concentration of degradation products generated by reaction between sevoflurane and soda lime. Br J Anaesth 1995; 74: 667–9.
Frink EJ Jr, Isner RJ, Malan TP Jr, Morgan SE, Brown EA, Brown BR Jr. Sevoflurane degradation product concentrations with soda lime during prolonged anesthesia. J Clin Anesth 1994; 6: 239–42.
Holloway AM. Possible alternatives to soda lime. Anaesth Intensive Care 1994; 22: 359–62.
Fee JPH, Murray JM, Luney SR. Molecular sieves: an alternative method of carbon dioxide removal which does not generate compound A during simulated lowflow sevoflurane anaesthesia. Anaesthesia 1995; 50: 841–5.
Baumgarten RK, Reynolds WJ. Much ado about nothing: trace gaseous metabolites in the closed circuit (Letter). Anesth Analg 1985; 94: 1029–30.
Baker AB. Back to basics — a simplified non-mathematical approach to low flow techniques in anaesthesia. Anaesth Intensive Care 1994; 22: 394–5.
Conway CM. Anaesthetic breathing systems.In: Scurr C, Feldman S (Eds.). Scientific Foundations of Anaesthesia, 3rd ed. Chicago: William Heinemann, Year Book Medical Publishers, 1982: 557–66.
Baum JA, Aitkenhead AR. Low-flow anaesthesia. Anaesthesia 1995; 50 (Suppl): 37–44.
Mapleson WW. The concentration of anaesthetics in closed circuits, with special reference to halothane. I: Theoretical study. Br J Anaesth 1960; 32: 298–309.
Ohmeda. Tec 5 Continuous flow vaporizer. Operation and maintenance manual. Part No. 1105-0100-000.
Morris LE. Closed carbon dioxide filtration revisited. Anaesth Intensive Care 1994; 22: 345–58.
Leijten DTM, Rejger VS, Mouton RP. Bacterial contamination and the effect of filters in anaesthetic circuits in a simulated patient model. J Hosp Infect 1992; 21: 51–60.
Luttropp HH, Berntman L. Bacterial filters protect anaesthetic equipment in a low-flow system. Anaesthesia 1993; 48: 520–3.
Bengtson JP, Brandberg A, Brinkhoff B, Sonander H, Stenqvist O. Low-flow anaesthesia does not increase the risk of microbial contamination through the circle absorber system. Acta Anaesthesiol Scand 1989; 33: 89–92.
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Baxter, A.D. Low and minimal flow inhalational anaesthesia. Can J Anaesth 44, 643–653 (1997). https://doi.org/10.1007/BF03015449
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DOI: https://doi.org/10.1007/BF03015449