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At least 19 recordsLinked to original sources
PubMed1992

[A comparative study of the cost of open-circuit as opposed to closed-circuit ventilation].

The authors compared two open randomized groups of patients undergoing surgery through general anaesthesia. Group 1 consisted of 54 patients ventilated by a Siemens 900 B ventilator in open circuit, and group 2, 56 patients ventilated by an ELSA de Gambro ventilator in a closed circuit. Comparative hour cost for nitrous oxide (N2O), oxygen (O2) and halogen gas, Enflurane, Isoflurane, was noted. All patients received the same regimen of anaesthesia and the two groups were identical in age, weight, surgery, respiratory volume and ventilation time. The evaluation of comparative hour cost included specific materials of close circuit ventilator: CO2 filter (Aridus), Lime. Were excluded maintenance and gas consumption expenditures before patient connected to the ventilator. The total hour cost (O2, N2O, specific materials for close circuit, without halogen gas) was 8.23 FF in closed circuit against 13.28 FF in open circuit, an economy of 38.27%. Hence, for oxygen, the hour cost was 0.70 FF in open circuit against 0.27 FF in closed circuit (gain of 65.3%). For nitrous oxide, the hour cost in open circuit was 12.50 FF against 2.44 FF in closed circuit (80.5%). For Isoflurane, the open circuit hour cost was 41.38 FF against 22.44 FF in closed circuit (47%). For Enflurane, the open circuit hour cost was 14.17 FF against 5.94 FF in closed circuit (58.1%). And, lastly for Enflurane, open circuit hour cost was 14.17 FF against 5.94 FF in close circuit, gain of 58.1%. These "modest" economy against those found in previous studies can be explained by the long-time duration of ventilation, saturating time in open circuit more or less long, depending on the physician, specific materials for closed circuit ventilation--lime, CO2 filter--in not taken into account, the hour cost of O2 + NO2 goes from 8.23 FF to 2.71 FF, and the gain against the close circuit becomes 79.6%: reducing hour cost by 5 times. In order to improve the effective cost of close circuit, the authors proposed: the use of closed circuit ventilation for more than 3 hours surgery, gas saturation in closed circuit after denitrogenation--which demands the use of halogen infjectors, and lime in containers cheaper than disposable cartridges. Respecting the above criteria, the total hour cost in close circuit fell to 4.90 FF, gain of 63% against open circuit. For O2 et N2O, the hour cost goes from 1.34 FF in close circuit to 13.28 FF in open circuit, 90% economy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1977

[The closed system (author's transl)].

It is appropriate to consider dose-regulated or quantitative closed-circuit anesthesia in terms of uptake of inhalation anesthetics from a reservoir bag which is never allowed to fill completely. The method which the authors have used routinely for 8 years requires reduction of the dose as a function of the inverse square root of elapsed anaesthesia time. Nitrogen does not accumulate because there is an inevitable loss of 20 to 100 ml/min between cuff and trachea. A simpler method, which has been well received, is that of "minimal flow" anesthesia (Virtue) with a constant fresh gas flow of 300 ml/min O2 and 200 ml/min N2O. "Low-flow" techniques typically entail use of 500 ml each of O2 and N2O per min.

Anesthesia, Inhalation↗
PubMed1992

Inspiratory valve malfunction in a circle system: pitfalls in capnography.

Capnography is a useful technique in monitoring the integrity of anaesthetic equipment such as the malfunctioning of unidirectional valves in circle system. However, the lack of a precise mechanism in existing capnographs to identify the start of inspiration and the beginning of expiration in the capnograms, makes the analysis of the carbon dioxide waveforms during inspiration difficult and thus results in inaccurate assessment of rebreathing. We report a case where, during the malfunction of the inspiratory unidirectional valve in the circle system, the capnograph failed to detect the presence of substantial rebreathing. Critical analysis of the capnogram recorded during the malfunction revealed that there was substantial rebreathing which was underestimated by the capnograph as it reports only the lowest CO2 concentration rebreathed during inspiration in such abnormal situations.

Anesthesia, Closed-Circuit↗
PubMed1992

Bacterial contamination and the effect of filters in anaesthetic circuits in a simulated patient model.

In order to investigate bacterial contamination of anaesthetic breathing circuits and means of prevention of this, six different laboratory experiments were performed. These experiments involved the bacterial contamination of Dräger Narkose Spiromat 650 and Dräger AV-1 circle system circuits and of an isolated soda lime carbon dioxide absorber. The effects of anaesthetic gas, gas flow rate and the incorporation of a hydrophobic membrane heat and moisture exchanging bacterial/viral filter (HMEF) at the patient end of these circuits were investigated. It was found that without a HMEF the whole interior of the anaesthetic circuits became contaminated with bacteria. Components closest to the simulated patient showed the highest levels of contamination. Higher gas flows were associated with decreased levels of circuit contamination, presumably because more bacteria were expelled from the system. Halothane (1 volume %) and soda lime were not found to have any demonstrable bactericidal action. The presence of a HMEF between the simulated patient and the Y-piece prevented any detectable contamination from reaching the circuit. Consequently, the presence of a HMEF provides protection of the anaesthetic circuit as well as other patients, healthcare workers and the environment.

Anesthesia, Closed-Circuit↗
PubMedDate not supplied

Anesthesia rebreathing bags: physical characteristics and use as portable oxygen reservoirs.

STUDY OBJECTIVE: To examine the physical characteristics of 3-liter anesthesia rebreathing bags and assess their use for oxygen (O2) storage and delivery during transport of patients from the operating room (OR) to the recovery area. SETTING: Anesthesia laboratory and pulmonary function laboratory. INTERVENTIONS: Five anesthesia rebreathing bags were inflated in 2-liter increments with 50 liters of air and then deflated in 2-liter increments. A sixth bag was inflated twice in 1-liter increments. Five bags were inflated with 60 liters of gas and allowed to deflate through a cannula functioning as a flow restrictor. Five bags were inflated with 100 liters of gas and checked for damage. MEASUREMENTS AND MAIN RESULTS: Pressure measurements done at 2-liter increments during inflation of the bags to 50 liters and deflation showed a consistent pattern of pressure-volume relationships. Assessment of gas flow during deflation through the cannula showed flow rates ranging from 3.1 to 3.8 L/min after 5 minutes of continuous flow and from 2.8 to 3.8 L/min after 10 minutes. No weakness or damage was apparent in bags inflated with 100 liters of gas. CONCLUSIONS: It is feasible for anesthesia rebreathing bags distended with O2 to serve as lightweight, inexpensive, and easily monitored alternatives to O2 tanks for O2 delivery during transport of patients from the OR to the recovery area.

Anesthesia Recovery Period↗
PubMed1992

Physical characteristics of an enclosed afferent reservoir breathing system.

We have assessed the characteristics of the Ohmeda Enclosed Afferent Reservoir Breathing System (EAR) using simulated spontaneous ventilation and controlled ventilation. The additional work of breathing through the system was measured and shown to be comparable to that of a modified Mapleson D breathing system (Bain) for fresh gas flows producing similar end-tidal carbon dioxide concentrations. It was shown under conditions of simulated controlled ventilation that end-tidal gas concentration was relatively insensitive to variations in inspired to expired ratio (I: E), tidal volume (VT) and deadspace (VD). Measurement of the volume of carbon dioxide rebreathed using simulated spontaneous ventilation led to the prediction that rebreathing of carbon dioxide would begin to occur in the EAR when fresh gas flow to total ventilation ratio (VF: VE) was approximately 0.87. However, comparison of the results of model lung tests and clinical data suggests that great caution should be taken in extrapolating such results into clinical advice.

Anesthesia, Closed-Circuit↗
PubMed1976

Efficacy of activated charcoal hemoperfusion in removing lethal doses of barbiturates and salicylate from the blood of rats and dogs.

Rats were injected intraperitoneally with lethal doses of sodium pentobarbital (115 mg/kg) or a lethal mixture of sodium salicylate (500 mg/kg) and sodium acetazolamide (25 mg/kg). Within about 20 min, part of each group was connected to an extracorporeal circuit containing uncoated activated charcoal and part to an empty control circuit. After a 90-min hemoperfusion, the treated groups showed a significantly decreased mortality (58% to 14% for pentobarbital; 100% to 0% for salicylate). Dogs were injected intravenously with lethal doses of sodium phenobarbital (175 mg/kg). One group was treated by hemoperfusion through an empty device in a control extracorporeal circuit, a second group was treated with loose-bed activated charcoal devices, and a third group with fixed-bed activated charcoal devices. For both the fixed and loose-bed devices, a 5-h hemoperfusion markedly decreased mortality (100% to less than or equal to 15%). The lethal combination of salicylate and closed-circuit methoxyflurane anesthesia was also successfully treated in dogs. This study clearly demonstrates the lifesaving potential of uncoated activated charcoal hemoperfusion.

Animals↗
PubMed1992

[Is the lithium chloride-coated heat and moisture exchanger a danger for patients?].

Such hygroscopic compounds as LiCl, CaCl2, and MgCl2 are used to improve water retention capacity and, as a consequence, the effectiveness of heat and moisture exchangers (HME). Resorption of these substances via the bronchopulmonary tract and a resulting systemic action cannot be excluded, especially if additional active moisturizing devices are used. The narrow therapeutic range of lithium is known, as are its unwanted side effects, such as nausea, vomiting, somnolence and even cardiac arrhythmia. These are symptoms that also frequently occur during anaesthesia and intensive care, so that differentiation against effects of lithium is nearly impossible. We investigated whether, in theory and in practice, LiCl-coated HME could result in effective Li plasma concentrations. We measured (1) total LiCl content of HMEs, (2) release of this content, simulating the worst-case situation with a breathing model, and (3) lithium plasma concentrations of adult patients being ventilated during anaesthesia with a rebreathing circuit and LiCl-coated HME, but with no additional active moisturizing system incorporated. RESULTS. The results show striking differences with LiCl content ranging from 3 to 251 mg varying not only between different types of HME but also within the same lots. After 20 min of ventilation more than 90% of the LiCl coating was rinsed into the test lung of the breathing model. In practical use, we observed an increase in lithium plasma concentration in 3 of 20 investigated patients. The plasma values of maximum 49.5 micrograms/l (= 0.007 mmol/l) do not amount to potentially toxic concentrations. Nevertheless, clinically relevant concentrations might occur in patients with small distribution volumes, e.g. newborns or infants with frequent exposition within short intervals such as in intensive care units. The differences in lithium content also indicate qualitative differences in water retention capacity. Because of the potential side effects of lithium, we prefer qualitatively equivalent HMEs, e.g., with MgCl2 or CaCl2 as hygroscopic substance.

Adult↗
PubMed1976

Closing capacity measurement during general anesthesia.

A modification of the single-breath nitrogen closing volume (CV) test allows measurement of closing capacity (CC) during general anesthesia. In the modification, inspiration and expiration are mechanically produced by a hydraulically powered cylinder. For 14 awake, normal subjects results of the CV test performed using this mechanical method differed that those obtained following spontaneous inspiration and expiration. Mean (+/-SE) CC's were 2.25 (+/-0.15) and 2.42 1 (+/-0.14) (P less than 0.01) using spontaneous and mechanical methods, respectively. The slopes of Phase III of the CV traces were 2.24 (+/-0.27) and 2.66 per cent N2/L (+/-0.32) (P less than 0.01), respectively. To eliminate differences due to measurement technique, the modified CV test was used both before and during anesthesia with halothane in 70 per cent N2 in 11 normal, supine, spontaneously breathing subjects. CC's were 1.89 l (+/-0.16) before and 1.84 l (+/-0.15) during anesthesia (P greater than .5). Mean functional residual capacities (FRC) by the closed-circuit helium method were 1.77 l (+/-0.15) before and 1.45 l (+/-0.17) during anesthesia (P less than .001). With CC unchanged and FRC decreased following induction, CC/FRC increased from 1.07 (+/-0.08) to 1.37 (+/-0.11) (P less than .005), suggesting increased small-airway closure during anesthesia.

Adult↗
PubMed1977

Anesthesia-induced alteration of small vessel response to norepinephrine.

Closed-circuit television microscopy was used to quantitate the in vivo response of small arteries (approximately 100 micron) and small veins (approximately 150 micron) to topically applied norepinephrine in the rat cremaster muscle. Rats were anesthetized with pentobarbital (50 mg/kg), or urethane (1200 mg/kg) or a combination of urethane (800 mg/kg) and chloralose (60 mg/kg). Complete concentration-response curves were obtained for an artery and vein pair in each rat and pD2 values (-log ED50) were used to evaluate the vascular sensitivity to norepinephrine. Both the artery and the vein in urethane-anesthetized animals had decreased sensitivity to norepinephrine in comparison to the vessels of animals anesthetized with pentobarbital or urethane-chloralose. Pretreatment with cocaine (10(-5) M) significantly increased the sensitivity of both the artery and vein in pentobarbital-anesthetized animals but did not affect the vessels in urethane-chloralose-anesthetized animals. These results are consistent with two opposing effects of the urethane-chloralose combination. The first is an increased sensitivity to norepinephrine via blockade of neuronal uptake and the second is a decreased sensitivity of norepinephrine via a vascular inhibitory effect of urethane.

Anesthetics↗
PubMed1976

Continuous measurement of vascular diameters via television microscopy.

In the past 10 years, microcirculation studies have emphasized quantitative measurements of microvascular diameters to characterize in vivo small vessel responses to experimental forcings such as hemorrhage, anesthesia, and hypoxia. We have developed an instrument to obtain continuous diameter measurements of a small artery and vein (40-200 mu) via closed-circuit television microscopy. The outputs are analog voltages proportional to the vessel diameters. Video processing is limited to two image areas termed "windows," which are defined by markers on the monitor and positioned over separate vertically aligned vessels. Each vessel, which appears darker than the surrounding tissue, is located by comparing the video signal to a reference voltage that adapts to changes in the relative contrast within the window. In the presence of a vessel, a ramp voltage is generated, the peak value of which is proportional to the vessel diameter. These peaks are averaged over the 15-video lines of the window and over several video frames to reduce noise sensitivity. In order to accommodate preparation movement such as skeletal muscle contraction, window position and width automatically adapt to changes in vessel position and width. Visual verification of system performance is provided by clamping the video signal to white on that portion of the image which the instrument identifies as vessel.

Arteries↗
PubMed1977

A comparison of the effect of three anaesthetic techniques on postoperative arterial oxygenation in the elderly.

Ninety patients (age range 49--99 yr) with a fracture of the neck of the femur were anaesthetized by a technique using halothane in oxygen in a closed circuit, halothane and 66% nitrous oxide in oxygen in a Magill circuit or artificial ventilation with 66% nitrous oxide in oxygen ("IPPV group"). In all three groups, there was a small decrease in PaO2 from an overall mean of 9.07 kPa before operation to 8.13 kPa at 60 min after anaesthesia. There was no significant difference between the groups in respect of the decrease; it was concluded that closed-circuit halothane in oxygen anaesthesia for this type of surgery was not accompanied by a significant degree of absorption collapse.

Aged↗
PubMed1979

Volatile metabolites and decomposition products of halothane in man.

The presence of two volatile halothane metabolites, 2-chloro-1,1,1-trifluoroethane (CF3CH2Cl) and 2-chloro-1,1-difluoroethylene (CF2CHCl), and a metabolite-decomposition product, 2-bromo-2-chloro-1,1-difluoroethylene (CF2CBrCl), were identified by gas chromatography-mass spectrometry in exhaled gases of 16 patients anesthetized with halothane in nonrebreathing, semiclosed and totally closed anesthesia circuits. No significant differences in concentrations of CF3CH2Cl and CF2CHCl were found relative to the anesthesia circuits used. CF2CBrCl could not be identified in the expired gases of patients anesthetized with a nonrebreathing circuit (Bain), but was present in gases recovered from both semiclosed and totally closed circuits. Under totally closed-circuit rebreathing conditions, the concentration of CF2CBrCl increased to 4-5 ppm, indicating significant breakdown of halothane by the soda lime. Possible pathways for formation of the two metabolites and the metabolite-decomposition product are presented, as well as clinical implications of these findings.

Anesthesia, Inhalation↗