Nitrous oxide defined

The energy of nitrous oxide adsorption is defined as the energy difference between (a) and (b)... 

Fig. 15. Relationship between the alfentanil plasma concentrations and the probability of needing naloxone to restore adequate spontaneous ventilation. The diagram at the upper part shows the alfentanil plasma concentrations of the patients who required naloxone (upward deflection) or did not require naloxone (downward deflection). The plasma concentration-effect curve for this clinical endpoint (lower part) was defined from the quantal data shown in the upper diagram using logistic regression. Bars indicate SE of C5o%. (From Ausems ME, Hug CC, Stanski DR, Burm AGE. Plasma concentrations of alfentanil required to supplement nitrous oxide anaesthesia for general surgery. Anaesthesiology 1986 65 362-73, reproduced by permission.)...

One of the most important factors influencing the transfer of an anesthetic from the lungs to the arterial blood is its solubility characteristics (Table 25-2). The blood gas partition coefficient is a useful index of solubility and defines the relative affinity of an anesthetic for the blood compared with that of inspired gas. The partition coefficients for desflurane and nitrous oxide, which are relatively insoluble in blood, are extremely low. When an anesthetic with low blood solubility... 

Depth of anesthesia is determined by the concentration of anesthetic agent that reaches the brain. Brain concentration, in turn, depends on the solubility and transport of the anesthetic agent in the bloodstream and on its partial pressure in inhaled air. Anesthetic potency is usually expressed as a minimum alveolar concentration (MAC), defined as the percent concentration of anesthetic in inhaled air that results in anesthesia in 50% of patients. As shown in Table 9.6, nitrous oxide, N2O, is the least potent of the common anesthetics. Fewer than 50% of patients are immobilized by breathing an 80 20 mix of nitrous oxide and oxygen. Methoxyflurane is the most potent agent a partial pressure of only 1.2 mm Hg is sufficient to anesthetize 50% of patients, and a partial pressure of 1.4 mm Hg will anesthetize 95%. 

It was first prepd in 1892 by Wislicenus (Ref l) by the action of nitrous oxide on Zn amide at 150-250°. Curtius Rissom (Ref 2) obtd the basic zinc azide, ZnOHN, by dissolving the metal in dil HN3 and allowing the soln to evap in air. The product, ill-defined anisotropic crysts, was insol in w. Dennis Isham (Ref 3) prepd Zn(Ns)a-2NH3 and Zn (Nj)a 2Cs Hs N by dissolving Zn in alcoholic HNj, adding dry NH3 or pyridine in excess, and allowing the soln to evap. Both products were wh, crystalline ppts, insol in w, and... 

A supercritical fluid is defined as a substance that is above its critical temperature and pressure. It exhibits remarkable liquid-like solvent properties and, therefore, high extraction efficiency. Such common gases as carbon dioxide and nitrous oxide have been successfully employed as supercritical fluids in the extraction of organics from solid matrices. The solid sample is placed in an extraction vessel into which the pressurized supercritical fluid is pumped. The organic analytes dissolve in the supercritical fluid and are swept out of the extraction chamber... 

The liquid-gas equilibrium line terminates at a point known as the critical point. The temperature and pressure that define the critical point are known as the critical temperature and the critical pressure. For example, nitrous oxide has a critical temperature of 36°C and a critical pressure of 72.45 bar (1051 psi). When the temperature and pressure exceed these critical values, the system becomes a supercritical fluid. Supercritical fluids have the flow properties of gases but densities similar to liquids, and supercritical fluids have no surface tension. Therefore, supercritical fluids are terrific solvents. For example, supercritical carbon dioxide is an excellent solvent for extracting caffeine from coffee without resorting to more toxic organic solvents like dichloromethane. 

Anesthetic potency can be expressed in terms of the minimal alveolar concentration (MAC) at which 50% of patients remain immobile following a defined painful stimulus (skin incision). Whereas the poorly lipophilic nitrous oxide must be inhaled in high concentrations, much smaller concentrations are required in the case of the more lipophilic halothane. 

The technique of flame atomic absorption spectrophotometry accomplishes this by aspirating the sample solution into a burner chamber, where it is mixed with a fuel gas and an oxidant gas. The mixture is then burned in a specially designed burner head (Fig. 2). The light beam is directed lengthway down the burner, and the absorption of the analyte atoms in the flame is measured. The most commonly used gas mixtures are air with acetylene and nitrous oxide with acetylene. Experimental conditions are well-defined in the literature, and cookbook conditions are available from most instrument manufacturers. In addition, many instruments are computer-controlled, and typical conditions are available directly on the operating screen. 

Preliminary investigations of intramuscular droperidol, nitrous oxide, and intravenous propofol have yielded favorable results in the treatment of acute migraine headache. Future studies may establish a more defined role for these agents in migraine management. 

Current anesthesia protocols usually include several agents in combinations that vary according to the depth of anesthesia required for specific procedures. Inhalational anesthetics, which include nitrous oxide and six halogenated hydrocarbons, have varying potency in proportion to their lipid solubilities. MAC value, a measure of anesthetic potency, is defined as the minimal alveolar anesthetic concentration (% of inspired air) at which 50% of patients do not respond to a surgical stimulus. MAC values are additive, lower in elderly patients, and lower in the presence of opioid analgesics and sedative hypnotics. 

The fragmentation of nitrous oxide following site-selective excitation of Is electrons of ah three atoms to the lowest unoccupied molecular orbital clearly shows a dependence on the atomic site of excitation as shown in Fig. 6 and Table V. The fragmentation patterns are not consistent with the idea of a Coulomb explosion as defined in the preceding section, or with the concept of localized bond rupture around the atomic site of excitation. The... 

The odd nitrogen family (NOy) is defined as the sum of all nitrogen-containing species except the major atmospheric constituent N2 and the source gases such as nitrous oxide (N20), hydrogen cyanide (HCN) and methyl cyanide (CH3CN). Thus, in the middle atmosphere, if we include... 

The main-chain scission yield was recently compared at room and liquid nitrogen temperatures [415] in the presence of a large number of additives known as radical, cation or electron scavengers. The results are given in Table 31. The protection index, in this case defined as 100(7V0 — N)/N where N0 and N are the number of scissions per chain in the absence and in the presence of additive, respectively, is nearly independent of the irradiation temperature marked protection is observed for all the additives studied with the exception of nitrous oxide. It must therefore be concluded that the mechanism of main-chain scission is identical at room and liquid nitrogen temperatures and that ions and radicals are involved in the radiolysis. A detailed study of the effect of ethyl mercaptan on main-chain scission and volatile formation was then undertaken [395]. About 75% protection of main-chain scission was obtained at 313 and at 77°K when the polymer contained 1.49 wt. % of ethyl mercaptan the protection index increases to 90% for concentrations of the order of 10 wt. %. The yield of volatile products was, however, unaltered by the presence of 1.5 wt. % ethyl mercaptan. 

To summarize the present results, Co (II) ions can be introduced into the Type A molecular sieves into the S-II type positions, where they are stable and resist both oxidation and reduction. These ions bind nitrous oxide, cyclopropane, water, and ammonia as additional ligands, their spectra being simultaneously changed in a defined fashion. The spectrochemical series of these ligands is, in the order of increasing ligand strength,... 

In clinical practice, one can monitor the equilibration of a patient with anesthetic gas. Equilibrium is achieved when the partial pressure in inspired gas is equal to the partial pressure in end-tidal (alveolar) gas. This defines equilibrium because it is the point at which there is no net uptake of anesthetic from the alveoh into the blood. For inhalational agents that are not very soluble in blood or any other tissue, equilibrium is achieved quickly (e.g., nitrous oxide, Figure 13-4). If an agent is more soluble in a tissue such as fat, equilibrium may take many hours to reach. This occurs because fat represents a huge anesthetic reservoir that will be filled slowly because of the modest blood flow to fat (e.g., halothane, Figure 13 ). 

Bent 1,3-dipolar systems such as ozone, nitrile imines, nitrile oxides, nitrous oxide, and bent allenoid azides are devoid of stereochemical handles at the termini nevertheless they have well-defined molecular faces, and if needed, the HED system can be applied to them as well. 

For many elements the atomization efficiency, defined as the ratio of the number of atoms to the total number of analyte species, atoms, ions, and molecules in the flame, is 1, although for other elements (e.g., the lanthanoids) it is less than 1, even in a nitrous oxide-acetylene flame. However, the formation of atoms is not the end of the story since once formed they may be lost through compound formation or ionization. Ionization increases exponentially with temperature and is a particular problem for the elements on the left of the periodic table, i.e., the alkali and the alkaline-earth elements. It is also a problem with Al, Ga, In, Sc, Ti, and T1 in the nitrous oxide-acetylene flame. A summary of atomization in flames is presented in Figure 2. 

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