1
|
Korman B, Dash RK, Peyton PJ. Effects of N 2 O elimination on the elimination of second gases in a two-step mathematical model of heterogeneous gas exchange. Physiol Rep 2023; 11:e15822. [PMID: 37923389 PMCID: PMC10624564 DOI: 10.14814/phy2.15822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 09/01/2023] [Indexed: 11/07/2023] Open
Abstract
We have investigated the elimination of inert gases in the lung during the elimination of nitrous oxide (N2 O) using a two-step mathematical model that allows the contribution from net gas volume expansion, which occurs in Step 2, to be separated from other factors. When a second inert gas is used in addition to N2 O, the effect on that gas appears as an extra volume of the gas eliminated in association with the dilution produced by N2 O washout in Step 2. We first considered the effect of elimination in a single gas-exchanging unit under steady-state conditions and then extended our analysis to a lung having a log-normal distribution of ventilation and perfusion. A further increase in inert gas elimination was demonstrated with gases of low solubility in the presence of the increased ventilation-perfusion mismatch that is known to occur during anesthesia. These effects are transient because N2 O elimination depletes the input of that gas from mixed venous blood to the lung, thereby rapidly reducing the magnitude of the diluting action.
Collapse
Affiliation(s)
- Ben Korman
- School of MedicineUniversity of Western AustraliaPerthWestern AustraliaAustralia
- Department of Anaesthesia and Pain MedicineRoyal Perth HospitalPerthWestern AustraliaAustralia
| | - Ranjan K. Dash
- Department of Biomedical EngineeringMedical College of WisconsinMilwaukeeWisconsinUSA
- Department of PhysiologyMedical College of WisconsinMilwaukeeWisconsinUSA
| | - Philip J. Peyton
- Anaesthesia, Perioperative and Pain Medicine Unit, Department of Anaesthesia, Austin Health, Melbourne Medical SchoolUniversity of MelbourneHeidelbergVictoriaAustralia
| |
Collapse
|
2
|
The association of nitrous oxide on length of stay in the postanesthesia care unit: a retrospective observational study. Can J Anaesth 2021; 68:1630-1640. [PMID: 34406608 DOI: 10.1007/s12630-021-02067-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 06/04/2021] [Accepted: 06/16/2021] [Indexed: 10/20/2022] Open
Abstract
PURPOSE To assess whether intraoperative use of nitrous oxide (N2O) as an adjunct to general anesthesia is associated with a shorter length of stay in the postanesthesia care unit (PACU). METHODS We analyzed data from adult patients who underwent non-cardiothoracic surgery under general anesthesia between May 2008 and December 2018. We assessed the association between intraoperative low- and high-dose N2O and PACU length of stay. RESULTS A total of 148,284 patients were included in the primary analysis. After adjusting for a priori defined confounders, a high dose of N2O significantly decreased PACU length of stay, with a calculated difference of -9.1 min (95% confidence interval [CI], -10.5 to -7.7; P < 0.001). Patients who received high-dose N2O had a lower incidence of both short- and prolonged-duration of intraoperative hypotension (adjusted odds ratio [aOR], 0.85; 95% CI, 0.83 to 0.88; P < 0.001 and aOR, 0.76; 95% CI, 0.73 to 0.80; P < 0.001, respectively) and received a lower total intraoperative vasopressor dose (-0.04 mg of norepinephrine equivalents; 95% CI, -0.06 to -0.01; P = 0.01). The effect of high-dose N2O on PACU length of stay was modified by surgical complexity (adjusted absolute difference: -26.1 min; 95% CI, -29.2 to -23.1; P < 0.001; P for interaction < 0.001), and most pronounced in patients who underwent complex surgery and received intraoperative antiemetic therapy (adjusted absolute difference: -38.9 min; 95% CI, -43.1 to -34.6; P < 0.001; P for interaction < 0.001). CONCLUSIONS Nitrous oxide was dose-dependently associated with a decreased PACU length of stay. The effect was clinically relevant (> 30 min difference) in patients who underwent complex surgical procedures and received intraoperative antiemetic therapy.
Collapse
|
3
|
Cumin D, Baker PA, Anderson BJ. Incidence of post-induction hypoxemia in children and the effect of induction gas composition. Paediatr Anaesth 2021; 31:763-769. [PMID: 33615619 DOI: 10.1111/pan.14161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 02/11/2021] [Accepted: 02/13/2021] [Indexed: 11/30/2022]
Abstract
BACKGROUND Pediatric preoxygenation and inhalation induction of anesthesia can include a mixture of gases. In children, the clinical impact on oxygenation while using other gases with oxygen during an inhalation induction is unknown. AIM We aimed to determine the impact of oxygen, nitrous oxide, and air concentrations added to the volatile agent by recording the incidence of hypoxemia following an inhalation gaseous induction in children. METHOD Records from an Automated Information Management System were used to find the incidence of hypoxemia following an inhalation induction of anesthesia. Episodes of hypoxemia (SaO2 < 90% sustained for at least 120 s) were recorded in the 10 min after the 3-min induction period. Nitrous oxide and oxygen concentrations were recorded and nitrogen concentration was deduced. We also considered patient sex, age, and ASA status as covariates. RESULTS A total of 27 258 cases were included in the analysis. The overall incidence of hypoxemia following an inhalation induction of anesthesia was 5.08% (95% CI 4.83 5.35). Hypoxemia was more common in younger patients and those with higher ASA scores. Controlling for those factors and sex, the incidence of hypoxemia increased 1.2-fold when inspired oxygen concentration was less than 60% and hypoxemia was 2.37 times greater than the overall incidence when the inspired oxygen concentration was less than 40%. There was no clear effect of different concentrations of nitrous oxide or nitrogen when those were factored into the model. CONCLUSION The risk of hypoxemia following an inhalation induction of anesthesia in children is minimized when the inspired concentration of oxygen is greater than 60%.
Collapse
Affiliation(s)
- David Cumin
- Department of Anaesthesiology, University of Auckland, Auckland, New Zealand
| | - Paul A Baker
- Department of Anaesthesiology, University of Auckland, Auckland, New Zealand.,Department of Paediatric Anaesthesia, Starship Children's Hospital, Auckland, New Zealand
| | - Brian J Anderson
- Department of Anaesthesiology, University of Auckland, Auckland, New Zealand.,Department of Paediatric Anaesthesia, Starship Children's Hospital, Auckland, New Zealand
| |
Collapse
|
4
|
Peyton PJ, Hendrickx J, Grouls RJE, Van Zundert A, De Wolf A. End-tidal to Arterial Gradients and Alveolar Deadspace for Anesthetic Agents. Anesthesiology 2020; 133:534-547. [PMID: 32784343 DOI: 10.1097/aln.0000000000003445] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND According to the "three-compartment" model of ventilation-perfusion ((Equation is included in full-text article.)) inequality, increased (Equation is included in full-text article.)scatter in the lung under general anesthesia is reflected in increased alveolar deadspace fraction (VDA/VA) customarily measured using end-tidal to arterial (A-a) partial pressure gradients for carbon dioxide. A-a gradients for anesthetic agents such as isoflurane are also significant but have been shown to be inconsistent with those for carbon dioxide under the three-compartment theory. The authors hypothesized that three-compartment VDA/VA calculated using partial pressures of four inhalational agents (VDA/VAG) is different from that calculated using carbon dioxide (VDA/VACO2) measurements, but similar to predictions from multicompartment models of physiologically realistic "log-normal" (Equation is included in full-text article.)distributions. METHODS In an observational study, inspired, end-tidal, arterial, and mixed venous partial pressures of halothane, isoflurane, sevoflurane, or desflurane were measured simultaneously with carbon dioxide in 52 cardiac surgery patients at two centers. VDA/VA was calculated from three-compartment model theory and compared for all gases. Ideal alveolar (PAG) and end-capillary partial pressure (Pc'G) of each agent, theoretically identical, were also calculated from end-tidal and arterial partial pressures adjusted for deadspace and venous admixture. RESULTS Calculated VDA/VAG was larger (mean ± SD) for halothane (0.47 ± 0.08), isoflurane (0.55 ± 0.09), sevoflurane (0.61 ± 0.10), and desflurane (0.65 ± 0.07) than VDA/VACO2 (0.23 ± 0.07 overall), increasing with lower blood solubility (slope [Cis], -0.096 [-0.133 to -0.059], P < 0.001). There was a significant difference between calculated ideal PAG and Pc'G median [interquartile range], PAG 5.1 [3.7, 8.9] versus Pc'G 4.0[2.5, 6.2], P = 0.011, for all agents combined. The slope of the relationship to solubility was predicted by the log-normal lung model, but with a lower magnitude relative to calculated VDA/VAG. CONCLUSIONS Alveolar deadspace for anesthetic agents is much larger than for carbon dioxide and related to blood solubility. Unlike the three-compartment model, multicompartment (Equation is included in full-text article.)scatter models explain this from physiologically realistic gas uptake distributions, but suggest a residual factor other than solubility, potentially diffusion limitation, contributes to deadspace.
Collapse
Affiliation(s)
- Philip J Peyton
- From the Anaesthesia, Perioperative and Pain Medicine Program, Centre for Integrated Critical Care, University of Melbourne, Melbourne, Australia (P.J.P.) the Department of Anaesthesia, Austin Health, Victoria, Australia (P.J.P.) the Institute for Breathing and Sleep, Victoria, Australia (P.J.P.) the Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium (J.H.) the Department of Anesthesiology, Onze-Lieve-Vrouw (OLV) Hospital, Aalst, Belgium (J.H.) the Department of Clinical Pharmacy, Catharina Hospital, Eindhoven, The Netherlands (R.J.E.G.) the Discipline of Anaesthesiology, Royal Brisbane and Women's Hospital, The University of Queensland, Brisbane, Australia (A.V.Z.) the Department of Anesthesiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois (A.D.W.)
| | | | | | | | | |
Collapse
|
5
|
Korman B, Dash RK, Peyton PJ. Elucidating the roles of solubility and ventilation-perfusion mismatch in the second gas effect using a two-step model of gas exchange. J Appl Physiol (1985) 2020; 128:1587-1593. [DOI: 10.1152/japplphysiol.00049.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gas exchange in the lung can always be represented as the sum of two components: gas exchange at constant volume followed by gas exchange on volume correction. Using this sequence to study the second gas effect, low gas solubility and increased ventilation-perfusion mismatch are shown to act together to enhance second gas uptake. While appearing to contravene classical concepts of gas exchange, a detailed theoretical analysis shows it is fully consistent with these concepts.
Collapse
Affiliation(s)
- Ben Korman
- Department of Anaesthesia and Pain Medicine, Royal Perth Hospital, Perth, Western Australia, Australia
| | - Ranjan K. Dash
- Departments of Biomedical Engineering and Physiology, Medical College of Wisconsin, Wisconsin
| | - Philip J. Peyton
- Anaesthesia, Perioperative, and Pain Medicine Unit, Melbourne Medical School, University of Melbourne, Department of Anaesthesia, Austin Health, Heidelberg, Victoria, Australia
| |
Collapse
|
6
|
Buhre W, Disma N, Hendrickx J, DeHert S, Hollmann MW, Huhn R, Jakobsson J, Nagele P, Peyton P, Vutskits L. European Society of Anaesthesiology Task Force on Nitrous Oxide: a narrative review of its role in clinical practice. Br J Anaesth 2019; 122:587-604. [PMID: 30916011 DOI: 10.1016/j.bja.2019.01.023] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 12/26/2018] [Accepted: 01/13/2019] [Indexed: 12/12/2022] Open
Abstract
Nitrous oxide (N2O) is one of the oldest drugs still in use in medicine. Despite its superior pharmacokinetic properties, controversy remains over its continued use in clinical practice, reflecting in part significant improvements in the pharmacology of other anaesthetic agents and developing awareness of its shortcomings. This narrative review describes current knowledge regarding the clinical use of N2O based on a systematic and critical analysis of the available scientific literature. The pharmacological properties of N2O are reviewed in detail along with current evidence for the indications and contraindications of this drug in specific settings, both in perioperative care and in procedural sedation. Novel potential applications for N2O for the prevention or treatment of chronic pain and depression are also discussed. In view of the available evidence, we recommend that the supply of N2O in hospitals be maintained while encouraging its economic delivery using modern low flow delivery systems. Future research into its potential novel applications in prevention or treatment of chronic conditions should be pursued to better identify its role place in the developing era of precision medicine.
Collapse
Affiliation(s)
- Wolfgang Buhre
- Department of Anesthesiology and Pain Medicine, Maastricht University Medical Center, University of Maastricht, Maastricht, the Netherlands
| | - Nicola Disma
- Department of Anesthesia, Istituto Giannina Gaslini, Genoa, Italy
| | - Jan Hendrickx
- Department of Anesthesiology, Onze-Lieve-Vrouwziekenhuis Hospital Aalst, Aalst, Belgium
| | - Stefan DeHert
- Department of Anesthesiology and Perioperative Medicine, University Hospital Ghent, Ghent, Belgium
| | - Markus W Hollmann
- Department of Anesthesiology, Amsterdam University Medical Center (AUMC), AMC, University of Amsterdam, Amsterdam, the Netherlands.
| | - Ragnar Huhn
- Department of Anesthesiology, University Hospital Düsseldorf, Düsseldorf, Germany
| | - Jan Jakobsson
- Department of Anesthesiology and Intensive Care, Institution for Clinical Science, Karolinska Institute, Danderyds University Hospital, Danderyd, Sweden
| | - Peter Nagele
- Department of Anesthesia and Critical Care, University of Chicago Medicine, Chicago, IL, USA
| | - Philip Peyton
- Department of Anaesthesia, Austin Health, and Anaesthesia Perioperative and Pain Medicine Unit, Melbourne Medical School, University of Melbourne, Melbourne, Australia
| | - Laszlo Vutskits
- Department of Anesthesiology, Pharmacology and Intensive Care, University Hospitals Geneva, Genève, Switzerland
| |
Collapse
|
7
|
Korman B, Dash RK, Peyton PJ. Effect of net gas volume changes on alveolar and arterial gas partial pressures in the presence of ventilation-perfusion mismatch. J Appl Physiol (1985) 2018; 126:558-568. [PMID: 30521424 DOI: 10.1152/japplphysiol.00689.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The second gas effect (SGE) occurs when nitrous oxide enhances the uptake of volatile anesthetics administered simultaneously. Recent work shows that the SGE is greater in blood than in the gas phase, that this is due to ventilation-perfusion mismatch, that as mismatch increases, the SGE increases in blood but is diminished in the gas phase, and that these effects persist well into the period of nitrous oxide maintenance anesthesia. These modifications of the SGE are most pronounced with the low soluble agents in current use. We investigate further the effect of net gas volume loss during nitrous oxide uptake on low concentrations of other gases present using partial pressure-solubility diagrams. The steady-state equations of gas exchange were solved assuming a log-normal distribution of ventilation-perfusion ratios using Lebesgue-Stieltjes integration. It was shown that under these conditions the classical partial pressure-solubility diagram must be modified, that for currently used volatile anesthetic agents the alveolar-arterial partial pressure difference is less than that predicted in the past, and that the alveolar-arterial partial pressure difference may even be reversed during uptake in the case of highly insoluble gases such as sulfur hexafluoride. Comparing this with the situation described previously for nitrogen in steady-state air breathing, we show that for nitrogen, the direction of the alveolar-arterial gradient is opposite to the direction of net gas volume movement. Although gas uptake with ventilation-perfusion inequality exceeding that when matching is optimal is shown to be possible, it is less likely than alveolar-arterial partial pressure reversal. NEW & NOTEWORTHY Net uptake of gases administered with nitrous oxide may proceed against an alveolar-arterial partial pressure gradient. The alveolar-arterial gradient for nitrogen in the steady-state breathing air depends not only on the existence of a distribution of ventilation-perfusion ratios in the lung but also on the presence of a net change in gas volume and is opposite in direction to the direction of net gas volume uptake.
Collapse
Affiliation(s)
- Ben Korman
- Department of Anaesthesia and Pain Medicine, Royal Perth Hospital , Perth, Western Australia , Australia
| | - Ranjan K Dash
- Departments of Biomedical Engineering and Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Philip J Peyton
- Anaesthesia, Perioperative, and Pain Medicine Unit, Melbourne Medical School, University of Melbourne, Department of Anaesthesia, Austin Health, Heidelberg, Victoria , Australia
| |
Collapse
|
8
|
|
9
|
Abstract
BACKGROUND Recent clinical studies suggest that the magnitude of the second gas effect is considerably greater on arterial blood partial pressures of volatile agents than on end-expired partial pressures, and a significant second gas effect on blood partial pressures of oxygen and volatile agents occurs even at relatively low rates of nitrous oxide uptake. We set out to further investigate the mechanism of this phenomenon with the help of mathematical modeling. METHODS Log-normal distributions of ventilation and blood flow were generated representing the range of ventilation-perfusion scatter seen in patients during general anesthesia. Mixtures of nominal delivered concentrations of volatile agents (desflurane, isoflurane and diethyl ether) with and without 70% nitrous oxide were mathematically modeled using steady state mass-balance principles, and the magnitude of the second gas effect calculated as an augmentation ratio for the volatile agent, defined as the partial pressure in the presence to that in the absence of nitrous oxide. RESULTS Increasing the degree of mismatch increased the second gas effect in blood. Simultaneously, the second gas effect decreased in the gas phase. The increase in blood was greatest for the least soluble gas, desflurane, and least for the most soluble gas, diethyl ether, while opposite results applied in the gas phase. CONCLUSIONS Modeling of ventilation-perfusion inhomogeneity confirms that the second gas effect is greater in blood than in expired gas. Gas-based minimum alveolar concentration readings may therefore underestimate the depth of anesthesia during nitrous oxide anesthesia with volatile agents. The effect on minimum alveolar concentration is likely to be most pronounced for the less soluble volatile agents in current use.
Collapse
|
10
|
|
11
|
The current place of nitrous oxide in clinical practice: An expert opinion-based task force consensus statement of the European Society of Anaesthesiology. Eur J Anaesthesiol 2016; 32:517-20. [PMID: 26244467 DOI: 10.1097/eja.0000000000000264] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
12
|
De Vasconcellos K. Nitrous oxide in 2010: who will have the last laugh? (Part 1). SOUTHERN AFRICAN JOURNAL OF ANAESTHESIA AND ANALGESIA 2014. [DOI: 10.1080/22201173.2010.10872662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
13
|
Role of Nitrous Oxide in Ambulatory Anaesthesia. CURRENT ANESTHESIOLOGY REPORTS 2014. [DOI: 10.1007/s40140-014-0072-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
14
|
Lee S, Cheng S, Ng S, Lim S. Single-breath vital capacity high concentration sevoflurane induction in children: with or without nitrous oxide? Br J Anaesth 2013; 110:81-6. [DOI: 10.1093/bja/aes319] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
15
|
De Vasconcellos K. Nitrous oxide in 2010: who will have the last laugh? (Part 2). SOUTHERN AFRICAN JOURNAL OF ANAESTHESIA AND ANALGESIA 2010. [DOI: 10.1080/22201173.2010.10872663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
16
|
Laing S, Paul V, Murison PJ. The effects of nitrous oxide on recovery from isoflurane anaesthesia in dogs. J Small Anim Pract 2009; 50:82-6. [DOI: 10.1111/j.1748-5827.2008.00689.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
17
|
Calvo Vecino JM, Abad Gurumeta A, Gil Lapetra C, Muñoz Velázquez MF, Pérez Gallardo A, Gilsanz Rodríguez F. [Monitoring airway gas in pediatric anesthesia: an experimental model for endotracheal gas measurement]. ACTA ACUST UNITED AC 2008; 55:13-20. [PMID: 18333381 DOI: 10.1016/s0034-9356(08)70492-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND We designed an endotracheal probe for measuring inspired and expired gas fractions during pediatric general anesthesia. OBJECTIVE To compare the gas fractions measured by means of intratracheal and extratracheal monitoring. MATERIAL AND METHODS The study included ASA 1 patients between the ages of 7 and 12 years under inhaled anesthesia with mechanical ventilation. The following parameters were recorded inside and outside the trachea: inspired and expired oxygen, nitric oxide (N2O) and sevoflurane fractions; the expired and inspired fraction gradients; PaCO2; and end-tidal carbon dioxide (ETCO2). Measurements were taken by an airflow sensor (Pedi-Lite) in the circuit before the point of connection to the endotracheal tube and by an intratracheal probe placed between the tube and the carina. Both sensors were connected to the same monitor. Measurements were taken on intubation and 5, 10, 15, 20, 30, 40, 50, and 60 minutes thereafter. PaCO2 was recorded at the same time. The recorded values were analyzed using the t test and the Pearson product moment correlation coefficient (r), and regression models were constructed using analysis of variance. RESULTS Seventy-one patients were enrolled in the study. The mean difference (SD) ETCO2 was 5 (3) mm Hg higher according to endotracheal measurement (P < .005), and that measurement was almost identical (+/-13 mm Hg) to the PaCO2 (P < or = .5). The inspired/expired gradients of endotracheal measurement of oxygen and N2O were 3 (2) points higher (P < .05) than the gradients of extratracheal measurements. In the case of sevoflurane gradients, however, the extratracheal values were higher (mean difference, 0.6 [0.2] points, P < .05). The inspired/expired oxygen and N2O gradients became equal after 18 (3) minutes; the sevoflurane gradients became equal after 8 (2) minutes. CONCLUSIONS Intratracheal and extratracheal measurements of the inspired and expired fractions of mixed gases provide different results.
Collapse
Affiliation(s)
- J M Calvo Vecino
- Servicio de Anestesiología y Reanimación, Hospital Infantil Universitario Niño Jesús, Madrid.
| | | | | | | | | | | |
Collapse
|
18
|
Smith I. Nitrous oxide in ambulatory anaesthesia: does it have a place in day surgical anaesthesia or is it just a threat for personnel and the global environment? Curr Opin Anaesthesiol 2006; 19:592-6. [PMID: 17093360 DOI: 10.1097/01.aco.0000247339.84685.d7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Nitrous oxide is by far the oldest anaesthetic still in routine use and its continued use is often questioned. Nitrous oxide is toxic with prolonged exposure, can damage the environment, causes pressure effects through expansion of closed air-filled spaces and has long been suspected of being harmful following chronic exposure to trace concentrations. What could possibly justify the continuing use of nitrous oxide? RECENT FINDINGS This review will attempt to demonstrate that the harmful effects of nitrous oxide are limited and not relevant to the majority of ambulatory patients. The environmental effects of nitrous oxide derived from anaesthetic use are negligible and there is no convincing evidence of harm to personnel. SUMMARY Not only is nitrous oxide almost certainly less hazardous than is sometimes perceived, it has numerous benefits which are not easily replicated by possible alternatives. In particular, its use improves the quality and safety of induction and maintenance of anaesthesia and facilitates faster recovery with minimal adverse effects. All of these benefits are achieved while at the same time reducing overall costs. With few significant drawbacks and numerous advantages, there appears still to be a valuable place for nitrous oxide in modern ambulatory anaesthesia.
Collapse
Affiliation(s)
- Ian Smith
- University Hospital of North Staffordshire, Stoke-on-Trent, Staffordshire, UK.
| |
Collapse
|
19
|
Current World Literature. Curr Opin Anaesthesiol 2006; 19:660-5. [PMID: 17093372 DOI: 10.1097/aco.0b013e3280122f5d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|