DOCSLIB.ORG

Respiratory Monitoring of Carbon Dioxide and Oxygen: a Ten-Year

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Respiratory Monitoring of Carbon Dioxide and Oxygen: a Ten-Year Special Communication RESPIRATORY MONITORING OF CARBON DIOXIDE Weingarten M. Respiratory monitoring of carbon dioxide and oxy- gen: a ten-year perspective. AND OXYGEN: A TEN-YEAR PERSPECTIVE J Clin Monit 1990;6:217-225 Maxwell Weingarten, MD ABSTRACT.During the past 10 years, instrumentation has been developed that can continuously and noninvasively measure changes in carbon dioxide and oxygen. The information gen- erated, which cannot be obtained through the human senses, provides vital clinical data regarding the effectiveness of intu- bation, ventilation, circulation, oxygenation, and the circuit. This instrumentation plays a major role in decision making both in the safe conduct of anesthesia and mechanical ventila- tion as well as in the detection and prevention of potentially catastrophic mishaps. For these reasons, a review of what has been learned regarding the instrumentation, collection, and interpretation of the clinical data, and the clinical value of the information is timely. The clinical significance of the carbon dioxide and oxygen waveforms, inspired to expired carbon dioxide and oxygen differences, alveolar-arterial gradients, and global supply-to-demand oxygen relationships measured by capnography, oxygraphy, and pulse oximetry are ad- dressed in this essay. KEY WORDS.Measurement techniques: capnography; oxyg- raphy; pulse oximetry. During the past 10 years major advances have been made in our ability to monitor and quantify carbon dioxide (CO2) and oxygen (O2) exchange continuously and noninvasively. Since evidence is accumulating that monitoring improves outcome, it may be useful to give a perspective gained from 10 years of monitoring CO2 and 02 during anesthesia and in ventilated patients. MEASUREMENT OF C02 The introduction of capnography by Smalhout and Kalenda [1] defined the relationship of exhaled CO2 to metabolism, circulation, respiration, and the circuit. Under their direction, capnography survived a stormy gestational period as it reached maturity in The Nether- lands. It was introduced in the United States at a small private meeting sponsored by a major instrument man- ufacturer held in conjunction with the World Congress on Intensive Care Medicine in Washington, DC, in May 1978. Five anesthesiologists attended the meeting, two of whom concluded that capnography would prove to be of very little value. Since then, capnography has come to be recognized as an extremely valuable method for the continuous monitoring of respiration and circu- lation in unconscious patients. Recognition of the value From the Department of Anesthesiology, St. Francis Hospital, Mil- ofcapnography for the detection and prevention of mis- waukee, WI 53215. haps has grown to the extent that some states (New Received Sep 15, 1988, and in revised formjan 29, 1990. Accepted for York, New Jersey) have mandated its use on all intubated publication Feb 7, 1990. patients. Copyright 1990 by Little, Brown and Company 217 218 Journal of Clinical Monitoring Vol 6 No 3 July 1990 Capnography refers to the graphic portrayal of the placed in one of the prongs of a nasal 0 2 catheter, or changing concentration of exhaled CO2 during the en- shielded inside a catheter placed in the nose or pharynx. tire respiratory cycle. It also may refer to the interpreta- tion of the waveforms. It should not be confused with INFECTION CONTROL. Sidestream sampling is simpler be- capnometry, which refers to only the digital presentation cause the water trap, connectors, and sampling catheter of the concentration without a waveform. are all disposable. With mainstream detectors the cu- The basis of capnography is rooted in the fact that all vette can be sterilized. mammalian cells, irrespective of their diversity of func- tion, have one common denominator, namely, that they WEIGHT. Sidestream sampling adds very little weight obtain the energy necessary to carry out their specific and bulk to the endotracheal tube connector. Main- functions by continuously using 02 to burn glucose to stream detectors add weight and bulk, which may in- its products of combustion, CO2 and water (H20). For crease the chances of inadvertently pushing the endotra- CO2 to be detected in the exhaled gases there must be cheal tube into the right bronchus if care is not taken. the production of CO2 in the cell (metabolism), the transport of CO2 from the cell to the lung (circulation), SAMPLING PROBLEMS. Moisture, blood, pus, and mucus and the elimination of CO2 as it diffuses into the alveoli may present a problem with both the mainstream and and through the airways (ventilation) [1]. Because the the sidestream techniques. In mainstream monitors, this respiratory cycle alternates the CO2-containing gases of material may cover the cuvette window; in sidestream exhalation with the fresh non-CO2-containing gases of monitors it may be aspirated directly into the detector. inspiration, a characteristic waveform of the changing Line plugging is possible, but these problems are mini- concentration of CO2 is produced. This waveform ac- mized in the better designed monitors of both tech- curately reflects the above sequence of events, as well as niques. Also, in sidestream monitors the aspiration of the total integrity and efficiency of the breathing circuit, air from leaks or fresh inflow gases can dilute the ex- including the ventilator, if one is in use. haled CO2 sample and slur the waveform. This occur- rence is less likely in mainstream monitors because there INSTRUMENTATION is no negative pressure in the circuit. Medical instrument manufacturers have provided a va- RESPONSE TIME. With mainstream monitors the response riety of CO2 monitors that differ widely in response time is less than half a second; in sidestream monitors time, data display, and clinical usefulness [2]. There are the response time is 2 to 3 seconds because of the time two main types, mainstream and sidestream monitors required for the sample to be aspirated through the sam- [3]. pling catheter to the detector. This difference in re- sponse time can be significant because of the need to furnish as early a warning as possible. With sidestream Comparison of Mainstream and Sidestream monitors the waveform can be influenced by the rate of Monitors aspiration, the length and diameter of the sampling In mainstream monitors the detector is designed to be catheter, the flow rate of the incoming gas, and sample attached to an airway adapter that is connected to the catheter turbulence that may distort the proximal and endotracheal tube. The respiratory gases pass by win- distal end of the expired CO2 bolus. dows in the airway adapter, so that the CO2 concentra- tion is measured by the detector without direct contact IMPORTANCEOF THE C02 WAVEFORM with the gases. In sidestream monitors, a small, light- weight Y piece is attached to the end of the endotracheal There is only one normal capnogram (Fig 1), and all tube, and gas is continuously aspirated back through the variations from the normal pattern indicate some ab- detector, which is housed within the monitor. normality that must be recognized and corrected if pos- sible [2]. MONITORING INTUBATED VERSUS NONINTUBATED PA- Any factor that impairs the free exhalation of gas, TIENTS. With the mainstream technique, only those pa- such as a kinked, displaced, or otherwise obstructed en- tients who are intubated can be monitored, since the dotracheal tube; asthma; bronchospasm; or chronic ob- detector is connected to the endotracheal tube. Side- structive pulmonary disease, will produce a change in stream sampling can be used on nonintubated as well as the angle of rise of the ascending limb from about 90 to intubated patients. On nonintubated patients the sam- 160 ~, depending on the severity of the expiratory ob- piing catheter can be placed inside a dental mouth hook, struction. An ascending limb with a long rise time and Special Communication: Weingarten: Carbon Dioxide and Oxygen Monitoring 219 G H 38mm Hg 38ram Hg Om~ Hg Omm Hg E F I dE Fig 2. Capnogram indicating expiratory obstruction. Fig 1. The normal carbon dioxide (C02) waveform. E represents the beginning of expiration; EF represents exhalation of upper air- way dead-space gases, which do not contain C02. FG, the ascend~ ing limb, rises almost at a right angle from the baseline and repre- 38ram Hg sents the increasing concentrations of CO2-containing gases coming flora the more distal airways. GH, the plateau, makes an ahnost right angle turn and parallels the baseline, gently rising a few ram, -L representing the product of the mixed expired COe-containing gases. H represents the end-tidal C02, t, ormally between 35 and Omm Hg 40 mm Hg. This measurement is valid as a trending relationship with arterial COz tension only if a normal plateau has been pres- Fig 3. Capnogram indicating diluted inspired gases. ent. HI, the descending limb, makes an almost right angle turn and rapidly descends to the base line. It represents the inspiratory phase during which fresh non-CO2-containing gases are inhaled and the C02 value falls to O. IE represents the phase of inspiration during tension, will decrease the height of the plateau. In a cir- which the upper airway dead space is filled with fresh non-CO2- culatory crisis the plateau will fall in proportion to the containing gases. Thus, IEF, the baseline, represents both the fresh severity of the event and slowly rise in height as pulmo- gas that filled the upper airway during inspiration and that which nary circulation improves, because the height of the is exhaled in early expiration. plateau is affected by pulmonary perfusion. In fact, ofaU available monitors in use during cardiac arrest, capnog- raphy furnishes the best real-time, continuous informa- no plateau indicates that exhalation has not been com- tion regarding the effectiveness of resuscitative efforts pleted before inhalation occurs. In this situation the arte- [4]. rial-alveolar CO2 [(a - A)Co2] gradient will increase The descending limb reflects the dynamics of inspi- significantly (Fig 2).
Load more

Recommended publications
  • National Competency Framework for Anesthesia Assistance
    National Competency Framework In Anesthesia Assistance Validated June 2016 201-2460 Lancaster Road Ottawa, Ontario K1B 4S5 1 INTRODUCTION ................................................................................................................ 3 ACKNOWLEDGEMENTS .................................................................................................. 3 HISTORICAL PERSPECTIVE ............................................................................................ 4 UNDERSTANDING THIS DOCUMENT ........................................................................... 6 SECTION 1: PROFESSIONAL AND ORGANIZATIONAL COMPETENCIES ............. 7 A. Demonstrate professionalism toward patients and their families, co-workers and the public .................................................................................................................................... 7 B. Demonstrate effective communication with the patient and their families, co-workers and the public ........................................................................................................................ 7 C. Demonstrate critical thinking and reasoning ............................................................... 7 D. Ensure the health and safety of the patient, co-workers and self ................................ 8 E. Use evidence to inform practice .................................................................................. 8 F. Perform administrative duties .....................................................................................
    [Show full text]
  • Pharmacology – Inhalant Anesthetics
    Pharmacology- Inhalant Anesthetics Lyon Lee DVM PhD DACVA Introduction • Maintenance of general anesthesia is primarily carried out using inhalation anesthetics, although intravenous anesthetics may be used for short procedures. • Inhalation anesthetics provide quicker changes of anesthetic depth than injectable anesthetics, and reversal of central nervous depression is more readily achieved, explaining for its popularity in prolonged anesthesia (less risk of overdosing, less accumulation and quicker recovery) (see table 1) Table 1. Comparison of inhalant and injectable anesthetics Inhalant Technique Injectable Technique Expensive Equipment Cheap (needles, syringes) Patent Airway and high O2 Not necessarily Better control of anesthetic depth Once given, suffer the consequences Ease of elimination (ventilation) Only through metabolism & Excretion Pollution No • Commonly administered inhalant anesthetics include volatile liquids such as isoflurane, halothane, sevoflurane and desflurane, and inorganic gas, nitrous oxide (N2O). Except N2O, these volatile anesthetics are chemically ‘halogenated hydrocarbons’ and all are closely related. • Physical characteristics of volatile anesthetics govern their clinical effects and practicality associated with their use. Table 2. Physical characteristics of some volatile anesthetic agents. (MAC is for man) Name partition coefficient. boiling point MAC % blood /gas oil/gas (deg=C) Nitrous oxide 0.47 1.4 -89 105 Cyclopropane 0.55 11.5 -34 9.2 Halothane 2.4 220 50.2 0.75 Methoxyflurane 11.0 950 104.7 0.2 Enflurane 1.9 98 56.5 1.68 Isoflurane 1.4 97 48.5 1.15 Sevoflurane 0.6 53 58.5 2.5 Desflurane 0.42 18.7 25 5.72 Diethyl ether 12 65 34.6 1.92 Chloroform 8 400 61.2 0.77 Trichloroethylene 9 714 86.7 0.23 • The volatile anesthetics are administered as vapors after their evaporization in devices known as vaporizers.
    [Show full text]
  • Low-Flow, Minimal-Flow and Metabolic-Flow Anaesthesia Clinical Techniques for Use with Rebreathing Systems ACKNOWLEDGEMENT: AHEAD of HIS TIME Professor Jan A
    Low-flow, minimal-flow and metabolic-flowLow-flow, anaesthesia D-38293-2015 Low-flow, minimal-flow and metabolic-flow anaesthesia Clinical techniques for use with rebreathing systems Christian Hönemann Bert Mierke Drägerwerk KGaA & Co. AG IMPORTANT NOTES Medical expertise is continually undergoing change due to research and clinical experience. The authors of this book intend to ensure that the views, opinions and assumptions in this book, especially those concerning applications and effects, correspond to the current state of knowledge. But this does not relieve the reader from the duty to personally carry the responsibilities for clinical measures. The use of registered names, trademarks, etc. in this publication does not mean that such names are exempt from the applicable protection laws and regulations, even if there are no related specific statements. All rights to this book, especially the rights to reproduce and copy, are reserved by Drägerwerk AG & Co. KGaA. No part of this book may be reproduced or stored mechanically, electronically or photographically without prior written authorization by Drägerwerk AG & Co. KGaA. Fabius®, Primus®, Zeus® and Perseus® are trademarks of Dräger. AUTHORS Christian Hönemann Bert Mierke PhD, MD PhD, MD Vice Medical Director Medical Director Chief physician in the collegiate system of Chief physician of the Clinic for the department of Anaesthesia and Operative Anesthesiology and Intensive Care Intensive Care, St. Marienhospital Vechta St. Elisabeth GmbH, Lindenstraße 3–7, Catholic Clinics Oldenburger Münsterland, 49401 Damme, Germany Marienstraβe 6–8, 49377 Vechta, Germany Low-flow, minimal-flow and metabolic-flow anaesthesia Clinical techniques for use with rebreathing systems ACKNOWLEDGEMENT: AHEAD OF HIS TIME Professor Jan A.
    [Show full text]
  • Pharmacokinetics and Pharmacology of Drugs Used in Children
    Drug and Fluid Th erapy SECTION II Pharmacokinetics and Pharmacology of Drugs Used CHAPTER 6 in Children Charles J. Coté, Jerrold Lerman, Robert M. Ward, Ralph A. Lugo, and Nishan Goudsouzian Drug Distribution Propofol Protein Binding Ketamine Body Composition Etomidate Metabolism and Excretion Muscle Relaxants Hepatic Blood Flow Succinylcholine Renal Excretion Intermediate-Acting Nondepolarizing Relaxants Pharmacokinetic Principles and Calculations Atracurium First-Order Kinetics Cisatracurium Half-Life Vecuronium First-Order Single-Compartment Kinetics Rocuronium First-Order Multiple-Compartment Kinetics Clinical Implications When Using Short- and Zero-Order Kinetics Intermediate-Acting Relaxants Apparent Volume of Distribution Long-Acting Nondepolarizing Relaxants Repetitive Dosing and Drug Accumulation Pancuronium Steady State Antagonism of Muscle Relaxants Loading Dose General Principles Central Nervous System Effects Suggamadex The Drug Approval Process, the Package Insert, and Relaxants in Special Situations Drug Labeling Opioids Inhalation Anesthetic Agents Morphine Physicochemical Properties Meperidine Pharmacokinetics of Inhaled Anesthetics Hydromorphone Pharmacodynamics of Inhaled Anesthetics Oxycodone Clinical Effects Methadone Nitrous Oxide Fentanyl Environmental Impact Alfentanil Oxygen Sufentanil Intravenous Anesthetic Agents Remifentanil Barbiturates Butorphanol and Nalbuphine 89 A Practice of Anesthesia for Infants and Children Codeine Antiemetics Tramadol Metoclopramide Nonsteroidal Anti-infl ammatory Agents 5-Hydroxytryptamine
    [Show full text]
  • BASIC Examination Questions with Answer
    BASIC Examination Questions 1. Which of the following nerves should be blocked for an operation at the medial aspect of the lower leg? A. Femoral B. Sciatic C. Common peroneal D. Tibial 2. A patient is scheduled to undergo laparoscopic cholecystectomy. Thirty minutes after receiving premedication with morphine and midazolam, she suddenly develops right upper quadrant abdominal pain and nausea. Which of the following is the most appropriate therapy for this patient’s pain? A. Flumazenil B. Ketorolac C. Naloxone D. Ranitidine 3. The relaxant effect of vecuronium on the neuromuscular system is augmented by adding a volatile anesthetic to a nitrous oxide/opioid anesthetic because of a decrease in: A. Muscle blood flow. B. Release of acetylcholine at the motor end-plate. C. Reuptake of acetylcholine at the motor end-plate. D. Sensitivity of the postjunctional membrane to depolarization. 4. An 85-kg, 35-year-old woman has persistent somnolence after a prolonged lower extremity orthopedic procedure during spinal anesthesia. During the last two hours of surgery, midazolam 5 mg and fentanyl 150 µg were administered for increasing restlessness and discomfort. Which of the following is most likely to result from administration of flumazenil? A. Grand mal seizure B. Hypertension and tachycardia C. Reversal of somnolence followed by resedation D. Sudden onset of pulmonary edema 5. A 68-year-old woman with primary hyperparathyroidism is scheduled to undergo parathyroidectomy. Her serum calcium concentration is 15 mg/dL. The most appropriate initial management is intravenous administration of: A. Indomethacin B. Magnesium sulfate C. Methylprednisolone D. Normal saline 6. Which of the following tests most reliably predicts the likelihood that a patient will develop malignant hyperthermia? A.
    [Show full text]
  • Inhalational Anesthetics
    UPTAKE AND DISTRIBUTION OF INHALATIONAL ANESTHETICS Dr.J.Edward Johnson.M.D.(Anaes),D.C.H. Asst.Professor, Kanyakumari Govt. Medical College Hospital. INTRODUCTION The modern anesthetist expeditiously develops and then sustains anesthetic concentrations in the central nervous system that are sufficient for surgery with agents and techniques that usually permit rapid recovery from anesthesia. Understanding the factors that govern the relationship between the delivered anesthetic and brain concentrations enhances the optimum conduct of anesthesia. I. UPTAKE OF INHALED ANESTHETICS. A. Factors raising the alveolar concentration, assuming a constant inspired anesthetic concentration, and no uptake by blood: 1. The inspired concentration (FI). a. The rate of rise is directly proportional to the inspired concentration. 2. The alveolar ventilation (Valveolar) a. The larger the minute alveolar ventilation (Valveolar), the more rapid the rise in alveolar concentration (FA) . b. Inspired gas is diluted by the FRC, so the larger the FRC, as a fraction of Valveolar, the slower the alveolar rise in anesthetic concentration. c. For ventilatory rates over 4 breaths, the ventilatory rate does not make any difference at the same Valveolar. 3. The time constant The time required for flow through a container to equal the capacity of the container. Time constant = volume (capacity)/flow Time Constant % washin/washout 1 63% 2 86% 3 95% 4 98% For example; If 10 liter box is initially filled with oxygen and 5 l/min of nitrogen flow into box then, the TC is volume (capacity)/flow. TC = 10 / 5 = 2 minutes. So, the nitrogen concentration at end of 2 minutes is 63%.
    [Show full text]
  • The Effects of Ventilation-Perfusion Scatter on Gas Exchange During Nitrous Oxide Anaesthesia
    The effects of ventilation-perfusion scatter on gas exchange during nitrous oxide anaesthesia A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy By Dr. Philip John Peyton MD MBBS FANZCA Department of Anaesthesia Austin Hospital and University Department of Surgery Austin Hospital and University of Melbourne 2011 Printed on Archival Quality Paper ii Abstract Nitrous oxide (N2O) is the oldest anaesthetic agent still in clinical use. Due to its weak anaesthetic potency, it is customarily administered at concentrations as high as 70%, in combination with the more potent volatile anaesthetic agents. It allows a dose reduction of these agents and, unlike them, is characterised by remarkable cardiovascular and respiratory stability and has analgesic properties. Its low solubility in blood and body tissues produces rapid washin into the body on induction and rapid washout on emergence at the end of surgery. Its rapid early uptake by the lungs is known to produce a concentrating effect on the accompanying alveolar oxygen (O2) and volatile agent, increasing their alveolar concentration and enhancing their uptake, which speeds induction of anaesthesia. This is called the “second gas effect”. The place of N2O in modern anaesthetic practice has increasingly been criticised. It has a number of potential adverse effects, such as immunosuppression with prolonged exposure, and the possibility of cardiovascular complications due to acute elevation of plasma homocysteine levels is currently being investigated. It has been implicated as a cause of post-operative nausea and vomiting (PONV), and is a greenhouse gas pollutant. Its continued use relies largely on its perceived pharmacokinetic advantages, but these have been questioned.
    [Show full text]
  • Pharmacology of Inhalational Anaesthetics John Myatt Correspondence Email: [email protected]
    Update in Anaesthesia Pharmacology of Inhalational Anaesthetics John Myatt Correspondence Email: [email protected] MODE OF ACTION Summary importance in lower brain centres and the spinal The molecular basis of inhalational anaesthesia is not cord. Potentiation of glycine receptors is seen at low Inhalational anaesthetics fully understood. Historically, the first observation concentrations for all the volatile agents. produce loss of consciousness, but may that had a significant impact was the Meyer-Overton Two-pore-domain potassium channels have other effects including hypothesis which demonstrated that the potency - these analgesia (nitrous oxide) (expressed as minimum alveolar concentration, MAC have subunits that are activated by volatile and gaseous or muscle relaxation - see below) of an anaesthetic agent increased in direct anaesthetics and may modulate membrane excitability (isoflurane). They are proportion to its oil:gas partition coefficient (see and have a complex distribution within the CNS. presented as liquefied gases Figure 1). This led to the interpretation that the site of Other possible targets may include NMDA receptors, under pressure or as volatile action of general anaesthetics was the lipid bilayer of HCN channels and some subtypes of the sodium liquids. nerve membranes and that when a sufficient amount channel. of drug was dissolved in this layer, then anaesthesia occurred. There were several theories as to the molecular POTENCY mechanism, but each with its own limitations. The potency of an inhalational anaesthetic agent can be More recent research suggests that inhalational agents measured by its MAC. This is defined as the minimum may act on specific membrane proteins and alter ion alveolar concentration at steady-state that prevents flux or receptor function.
    [Show full text]
  • Nitrous Oxide Diffusion and the Second Gas Effect on Emergence from Anesthesia
    Nitrous Oxide Diffusion and the Second Gas Effect on Emergence from Anesthesia Philip J. Peyton, M.D.,* Ian Chao, M.B.B.S.,† Laurence Weinberg, F.A.N.Z.C.A.,‡ Gavin J. B. Robinson, F.A.N.Z.C.A.,§ Bruce R. Thompson, Ph.D.࿣ ABSTRACT What We Already Know about This Topic Downloaded from http://pubs.asahq.org/anesthesiology/article-pdf/114/3/596/253394/0000542-201103000-00026.pdf by guest on 27 September 2021 • The increase in the partial pressures of the other gases in the Background: Rapid elimination of nitrous oxide from the alveolar mixture resulting from the rapid uptake of high con- lungs at the end of inhalational anesthesia dilutes alveolar centrations of nitrous oxide during inhalational anesthesia in- duction is known as the second gas effect. oxygen, producing “diffusion hypoxia.” A similar dilutional effect on accompanying volatile anesthetic agent has not been evaluated and may impact the speed of emergence. Methods: Twenty patients undergoing surgery were ran- What This Article Tells Us That Is New domly assigned to receive an anesthetic maintenance gas • The second gas effect also occurs during emergence, with the mixture of sevoflurane adjusted to bispectral index, in air- rapid removal of nitrous oxide increasing the removal of other oxygen (control group) versus a 2:1 mixture of nitrous oxide- volatile anesthetics. oxygen (nitrous oxide group). After surgery, baseline arterial and tidal gas samples were taken. Patients were ventilated reduction of concentrations of the accompanying volatile with oxygen, and arterial and tidal gas sampling was repeated agents, contributing to the speed of emergence observed after at 2 and 5 min.
    [Show full text]
  • Nitrous Oxide Use in Children
    Rev Bras Anestesiol SPECIAL ARTICLE 2012; 62: 3: 451-467 SPECIAL ARTICLE Nitrous Oxide Use in Children Leonardo Teixeira Domingues Duarte 1, Gastão Fernandes Duval Neto 2, Florentino Fernandes Mendes 3 Summary: Duarte LTD, Duval Neto GF, Mendes FF – Nitrous Oxide Use in Children. ©2012 Elsevier Editora Ltda. All rights reserved. DESCRIPTION OF THE EVIDENCE COLLECTION 11. Nitrous Oxide [MeSH] AND Anesthesia, General METHOD [MeSH] AND Child [MeSH] AND Randomized Con- trolled Trial[ptyp] Searches were carried out in multiple databases (Medline 12. Pediatrics [MeSH] OR Neonatology [MeSH] AND Ni- 1965 to 2009, Cochrane Library, LILACS) and cross-referenc- trous Oxide [MeSH] es with the collected material to identify articles with better 13. Nitrous Oxide [MeSH] AND Anesthesia, General methodological design, followed by critical evaluation of their [MeSH] AND Pediatrics [MeSH] AND Randomized content and classification according with the strength of evi- Controlled Trial[ptyp] dence. 14. Nitrous Oxide [MeSH] AND Anesthesia, General Searches occurred between December 2007 and April [MeSH] AND Neonatology [MeSH] AND Randomized 2008. The following search strategies were used for searches Controlled Trial[ptyp] in PubMed: 15. Cerebral Palsy [MeSH] AND Child [MeSH] AND Ni- trous Oxide [MeSH] 1. Nitrous Oxide [MeSH] AND Pharmacology [MeSH] AND Toxicology [MeSH] Studies comparing different classes of anesthetic drugs or 2. Nitrous Oxide [MeSH] AND Toxicology [MeSH] sedation techniques in children undergoing diagnostic tests 3. Nitrous Oxide [MeSH] AND toxicity [subheading] or procedures with the use of sedation or anesthesia were 4. Nitrous Oxide [MeSH] AND Acute Toxicity Tests selected. Also selected were studies that evaluated the phar- [MeSH] OR Toxicity Tests [MeSH] macological effects of nitrous oxide, its interaction with other 5.
    [Show full text]
  • The Use of Midazolam, Isoflurane, and Nitrous Oxide for Sedation and Anesthesia of Ball Pythons (Python Regius)
    The Use of Midazolam, Isoflurane, and Nitrous Oxide for Sedation and Anesthesia of Ball Pythons (Python regius) by Cédric B. Larouche A Thesis presented to The University of Guelph In partial fulfilment of requirements for the degree of Doctor of Veterinary Science in Pathobiology Guelph, Ontario, Canada © Cédric B. Larouche, August, 2019 ABSTRACT THE USE OF MIDAZOLAM, ISOFLURANE, AND NITROUS OXIDE FOR SEDATION AND ANESTHESIA OF BALL PYTHONS (PYTHON REGIUS) Cédric B. Larouche Co-advisors: University of Guelph, 2019 Nicole Nemeth Dorothee Bienzle The objectives of this project were to characterize the pharmacodynamics and pharmacokinetics of midazolam in the ball python (Python regius), and to evaluate the effects of midazolam and nitrous oxide (N2O) on the minimum anesthetic concentration of isoflurane (MACIso) in this species. The pharmacodynamics of midazolam were evaluated in a blinded, randomized, crossover study comparing two dosages (1 and 2 mg/kg intramuscular [IM]) in ten ball pythons. There were no significant differences between the two dosages for any parameter evaluated. Midazolam provided moderate sedation and muscle relaxation in all snakes starting 10-15 min post-injection and lasting up to 3-5 days, with a peak effect 60 min post-injection. Heart rates were significantly lower than baseline from 30 min to 5.3 days post-injection with both dosages. In an open trial using 9 ball pythons, the reversal effect of flumazenil was evaluated by administering 0.08 mg/kg IM 60 min after the administration of 1 mg/kg IM of midazolam. Sedation and muscle relaxation were fully reversed within 10 min of administration, but all snakes fully resedated within 3 h.
    [Show full text]
  • Inhalant Anesthesia
    Inhalant Anesthesia Horatiu V. Vinerean DVM, DACLAM Director, Laboratory Animal Research Attending Veterinarian 1 Inhalation Anesthesia - History 2 Inhalation Anesthesia • This is the technique of administering anesthetic agents to the animals via the lungs. • This consists of a volatile agent being vaporized by oxygen in a vaporizer and then being administered to the patient through an anesthetic breathing circuit. 3 Vaporization of volatile anesthetics • A vapor is a gas below its critical temperature. Both liquid and gaseous phases exist simultaneously and in a closed container a state of equilibrium is attained when the number of molecules leaving the liquid phase equals the number of molecules re-entering it. • In this situation, the vapor is said to be saturated and the partial pressure that the vapor exerts is the saturated vapor pressure (s.v.p.) that depends only upon the nature of the liquid and the temperature. 4 Anesthetic Uptake • The depth of anesthesia is related to the partial pressure of anesthetic agents in the brain. This is in turn related to the partial pressure in the blood and this, in turn, is related to the partial pressure of the agent in the alveoli of the lungs. • The mechanism for a gas to dissolve in the patients blood and other tissues relies on pressure and pressure gradients between the tissues or phases. • For an anesthetic action to occur the anesthetic agent must be capable of crossing the blood brain barrier to the central nervous system (lipid soluble). 5 Physics laws of anesthetic uptake • Dalton's Law of Partial Pressure: The constituent gases in gas mixtures act independently of each other and exert the pressure that each would have exerted in isolation in the given volume.
    [Show full text]