Venous air emboli with 15N2: pulmonary excretion and physiologic responses in dogs

Venous air embolism occurs with decompression sickness as well as during a wide variety of surgical procedures in hospitalized patients. We developed a canine model to allow documentation and quantitation of pulmonary excretion of intravascular air emboli both in a control air breathing state and during treatment. We utilized 15N2 (a stable, nonradioactive isotope of room air nitrogen, 14N2) as the nitrogen component of venous air emboli (1 ml.kg-1) given to 27 anesthetized mongrel dogs ventilated with room air (tidal volume = 15 ml.kg-1). End-tidal 15N2 was measured and the embolism diagnosed by increased levels in exhaled gases. Exhaled gases were also collected in Douglas bags and the 15N2 recovered was quantitated by a helium dilution technique. Systemic and pulmonary artery pressure changes and quantitation of excreted 15N2 were documented after embolism during a control state with continued room air (21% oxygen) ventilation, and after treatments with either a) 100% oxygen ventilation; b) compression to 2128 mmHg, or 2.8 atm abs, and room air ventilation; or c) a combination of 100% oxygen ventilation and 2.8 atm abs compression. Increased end-tidal 15N2 was characteristic of all emboli, and use of 15N2 allowed accurate measurement of excreted gas during both room air and 100% oxygen ventilation. Embolic gas recoveries were not increased significantly by any of the treatments.

Stability of arterial to end-tidal carbon dioxide gradients during postoperative cardiorespiratory support

The changes in the arterial to end-tidal carbon dioxide gradient. P(a-ET)CO2, were studied in postoperative cardiac surgery patients from the time of admission to the intensive care unit, during changing cardiorespiratory support, up to the time of tracheal extubation. Individual factors evaluated for their effects on P(a-ET)CO2 included rate of mechanical ventilation, infusion of vasoactive agents (nitroglycerin, nitroprusside, dopamine, dobutamine, and metariminol), and associated changes in haemodynamic pathophysiology (cardiac index, pulmonary artery pressure, pulmonary vascular resistance index, systemic vascular resistance index, and pulmonary capillary wedge pressure). After approval by the Clinical Investigation Committee, 59 patients, age 63 +/- 9 (41 to 75) yr, were studied and 382 individual gradient determinations made. Mean P(a-ET)CO2 was 5.47 +/- 5.21 mmHg, with the mean PaCO2, 36.51 +/- 5.89 mmHg and mean ETCO2, 31.04 +/- 6.44 mmHg. For the population as a whole, the correlation between PaCO2 and ETCO2 determined by regression analysis was maintained (R = 0.644, P less than 0.001). Comparison of the individual and population correlation coefficients by Student's t test showed no significant difference, but a normal population distribution of the gradients (P less than 0.05). None of the variables assessed could be determined to influence P(a-ET)CO2 significantly. For many of the individual patients, however, the relationship between PaCO2 and ETCO2 did not maintain a significant correlation throughout the study period. In the postoperative cardiac surgery patient population P(a-ET)CO2 follows a normal distribution and PaCO2 and ETCO2 maintain a statistically significant correlation. However, when evaluating individual patients, this relationship has wide variability.

An evaluation of three intravenous anesthetic regimens in New Zealand rabbits

Intravenous anesthetics can be readily administered to rabbits through the marginal ear vein. In this study, three intravenous anesthetic protocols were evaluated in New Zealand White rabbits. The three anesthetic regimens were: (a) pentobarbital (40 mg/kg); (b) ketamine-xylazine (25-5 mg/kg); (c) midazolam-xylazine-alfentanil (1-1-0.1 mg/kg). The anesthetics were injected slowly over defined time intervals. Reactions to noxious stimuli were determined before and after administration of the anesthetics. Additionally, the effects of the anesthetic agents on the rabbit's cardiopulmonary system were evaluated. Rabbits anesthetized with midazolam-xylazine-alfentanil did not have a pedal withdrawal or ear pinch reflex throughout the testing period. The ketamine-xylazine combination produced a shorter duration of non-responsiveness to noxious stimuli. Rabbits anesthetized with pentobarbital had the greatest variability in response to noxious stimuli. Apnea occurred in at least one rabbit in each group. A side effect unique to the midazolam-xylazine-alfentanil group was the occurrence of opisthotonus or seizure activity during or shortly after the administration of alfentanil. Hypotension, hypercapnia and respiratory acidosis were characteristic of the cardiopulmonary effects of the anesthetics. When choosing an anesthetic regimen for rabbits, intravenous infusion should be considered as an option. Advantages include ease of administration, possibility of redosing as required, and minimal requirements for equipment. Disadvantages of intravenous anesthetic infusion in rabbits include potential for lethal overdose and metabolic alterations after administration.

Hyperbaric nitrous oxide as a sole anesthetic agent in humans

Nitrous oxide (N2O) has been used to produce analgesia and anesthesia for more than 100 yr. However, because of its high MAC value (1.04), general anesthesia with N2O can usually be attained only in a hyperbaric environment. Because of the sparsity of documentation for human physiologic responses to hyperbaric N2O, we studied eight male volunteers at 2 ATA (1520 mm Hg) anesthetized with N2O only for periods of 2-4 h. N2O partial pressures ranged from 836 to 1368 mm Hg. The anesthetic state was associated with tachypnea, tachycardia, increases in systemic blood pressure, mydriasis, diaphoresis, and at times, clonus and opisthotonus. A stable level of physiologic activity was difficult to maintain.

Detection of venous air embolism in dogs by emission spectrometry

Emission spectrometers provide alternative, relatively inexpensive methods for detecting the concentration of respiratory gas nitrogen. Mass spectrometers are accepted as reliable monitors of end-tidal nitrogen for detection of venous air embolisms. We evaluated an inexpensive emission spectrometer for detecting changes in nitrogen levels and compared it with a mass spectrometer for detecting increased end-tidal nitrogen levels in dogs with venous air embolisms. During in vitro gas flow studies (helium; oxygen; helium/oxygen mixtures; or 70% nitrous oxide/30% oxygen with 0, 1, 2, or 3% isoflurane), air boluses (0.01 to 5.0 ml) were injected into a gas flow circuit and outlet nitrogen levels were measured by a Collins 21232 emission spectrometer. Responses were greater after each bolus when helium rather than oxygen was the major diluent gas. During in vivo studies, 5 dogs were anesthetized, ventilated, denitrogenated, and given venous air embolisms (0.1, 0.5, and 1.0 ml.kg-1) during oxygen and then during Heliox (20% oxygen:80% helium) breathing. End-tidal nitrogen increased approximately two-fold after venous air embolisms given during Heliox as compared with oxygen ventilation. In all 0.1-ml.kg-1 venous air embolisms end-tidal nitrogen increased when the emission spectrometer was used, but venous air embolisms less than 1.0 ml.kg-1 were not consistently detected by mass spectrometry. Emission spectrometry can be used to detect increased end-tidal nitrogen levels indicative of venous air embolism and may be a more sensitive detector than mass spectrometry.

The structure of 19αH-Lupeol methyl ether from Chionochloa bromoides

The structure of l9αH-lupeol methyl ether isolated from Chionochloa bromoides has been determined by 13C n.m.r. spectroscopy and X-ray diffraction. Crystals of the triterpene are monoclinic, space group P21, with a 8.071(1), b 14.5477(6), c 11.6061(4) �, β 104.466(5)�, V 319.6 �3 and Z 2. The structure was solved by direct methods, and was refined to R 0.054 for 1092 observed reflections. Previous reports of synthetic and naturally occurring 19αH-lupanes are briefly discussed, as is the distribution of the chemotaxonomically discriminating triterpene methyl ethers in Chionochloa.

The Absolute Configuration at C24 of the Ecdysteroids Dacrysterone, Pterosterone and Ponasterone C

The shielding values in 13C N.M.R. spectra of the ecdysteroids dacrysterone, pterosterone, and ponasterone C have been assigned, together with those for the 20,22- and 22,24-benzylidene acetal derivatives of the latter. From the N.M.R. data the C24 configuration of dacrysterone is assigned as 24R, while the 24s configuration is assigned to pterosterone and ponasterone C.

Insect-control chemicals from plants. III. Toxic lignans from Libocedrus bidwillii

Feeding tests showed that the powdered dried leaves and leaf extracts of L. bidwilli are toxic to the larvae of the housefly (Musca domestica), and the codling moth (Laspeyresia pomonella). The powdered material was not toxic to the light-brown apple moth (Epiphyas postvittana). The most active toxin is the lignan beta-peltatin-A methyl ether (II) and at a concentration of 100 ppm in a chemically defined diet it gave 98% mortality of housefly larvae.

Insect-Control Chemicals From Plants III. Toxic Lignans From Libocedrus Bidwillii

Feeding tests showed that the powdered dried leaves and leaf extracts of L. bidwillii are toxic to the larvae of the housefly (Musca domestica), and the codling moth (Laspeyresia pomonella). The powdered material was not toxic to the light-brown apple moth (Epiphyas postvittana).The most active toxin is the lignan fi-peltatin-A methyl ether (II) and at a concentration of 100 ppm in a chemically defined diet it gave 98 % mortality of housefly larvae.

Tumour inhibitory plants. New alkaloids from the bark of Erythrophleum chlorostachys (Leguminosae)

A new alkaloid, norerythrostachamine (1), and its rearrangement product, norerythrostachamide (2), from extracts of E. chlorostachys bark, are shown to be the ester and amide of 2-methylaminoethanol and 3β,7β-dihydroxycass-13(18)-en-16,19-dioic acid 16-methyl ester already known from borohydride reduction of erythrophlamic acid. A second isomeric pair, norcassamidine (3) and norcassamidide (4), derived from 2-methylaminoethanol and cassamidic acid, are described as well as a new amide, norcassaidide (9, formed from the same amine and cassaidic acid. The known alkaloids cassaidine (6), cassamidine (7) and norerythrophlamide (8) were also isolated.

Insect-control chemicals from plants. II. Effects of five natural norditerpene dilactones on the development of the housefly

The effects of feeding five natural norditerpene dilactones (hallactone A, podolactones A, C, and E, and sellowin A) to housefly larvae (Musca domestica L.) reared on a defined diet were determined.

Insect-control chemicals from plants. Nagilactone C, a toxic substance from the leaves of Podocarpus nivalis and P. hallii

Feeding tests showed that the powdered dried leaves and leaf extract of P. nivalis Hook and P. hallii Kirk are toxic to housefly larvae when incorporated into a milk diet. An active toxic ingredient has been isolated and identified as the known norditerpene lactone, nagilactone C. Nagilactone Cat 50 p.p.m. in a defined medium was toxic to housefly larvae. At lower concentrations it inhibited larval growth, maturation to pupae, and emergence of adults. Nagilactone C was not toxic to 3-4-day�old housefly larvae or to 2-3 day old adults when applied topically at the rate of 5 p.g per insect.

ω-Hydroxyisodillapiole, a new cinnamyl alcohol from Piper novae-hollandiae

A minor constituent of the wood of Piper novae-hollandiae is shown by synthesis from dillapiole to be the previously unknown ω-hydroxyisodillapiole (2)((E)-2,3-dimethoxy-4,5-methylenedioxyoinnamyl alcohol).

Tumour inhibitory plants. Amides of Piper novae-hollandiae (Piperaceae)

A new amide, Δαβ-dihydropiperine (I), has been isolated from the wood of Piper novae-hollandiae and synthesized. Two amides, N-isobutyl-trans- 2,trans-4-octadienamide and 3,4-methylenedioxycinnamoylpiperidide, previously unreported from natural sources but known from synthesis, were present as were five amides already established as plant constituents, namely, N-isobutyl-trans-2,trans-4-decadienamide, fagaramide, piperlonguminine, piperine, and an isomer of piperine, probably chavicine, as well as the essential oil, dillapiole. Δαβ-and Δβγ-Dihydro-piperlonguminine, (VIII) and (IX), and Δβγ-dihydropiperine (III) were also synthesized.

Tumour inhibitory plants. The alkaloids of Bruguiera sexangula and Bruguiera exaristata (Rhizophoraceae)

Tropine and tropine esters of acetic, propionic (a new natural ester), n-butyric (a new natural ester), isobutyric, α-methylbutyric or isovaleric, and benzoic acids have been identified in crude alkaloid mixtures from the bark of B. sexangula and B. exaristata. The major component of the mixtures from both species was a new alkaloid, brugine, (+)-tropine 1,2-dithiolan-3-carboxylate.