Fragmentation of tube exchanger.
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Adult↗
Biomedical subjects
A G Targ
Publications and source records attributed to A G Targ.
A new device to check the anesthesia machine low-pressure system.
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Anesthesiology↗
Cardiovascular actions of common anesthetic adjuvants during desflurane (I-653) and isoflurane anesthesia in swine.
To determine the cardiovascular actions of drugs commonly combined with inhalation anesthetics, we administered one drug from each of several classes of adjuvants to seven swine already anesthetized with equipotent concentrations (1.2 MAC) of desflurane, formerly I-653, a new inhaled anesthetic, or isoflurane. Succinylcholine (1 and 2 mg/kg), atracurium (0.6 mg/kg), and atropine (5 micrograms/kg) plus edrophonium (5 mg/kg) had no cardiovascular effects. Fentanyl was given in amounts that decreased MAC for the inhaled anesthetics by 25%-35%. A dose of 50 micrograms/kg IV had no cardiovascular effects during either anesthetic, whereas 100 micrograms/kg IV modestly increased systemic vascular resistance without changing other variables. Naloxone (100 micrograms/kg IV) during infusion of fentanyl decreased systemic vascular resistance and increased cardiac output during both desflurane and isoflurane anesthesia, increased heart rate during only isoflurane anesthesia, and did not affect mean arterial blood pressure during either anesthetic. Thiopental (2.5 and 5.0 mg/kg IV) decreased mean aortic blood pressure, cardiac output, stroke volume, and systemic vascular resistance during both anesthetics without altering heart rate or left- or right-sided cardiac filling pressures. The addition of 60% nitrous oxide caused no cardiovascular changes during desflurane anesthesia, but increased systemic vascular resistance and decreased cardiac output and stroke volume during isoflurane without altering heart rate or cardiac preload. We conclude that the usual clinical doses of adjuvants commonly administered during anesthesia have no untoward cardiovascular actions during 1.2 MAC desflurane or isoflurane anesthesia in swine.
Adjuvants, Anesthesia↗
Pharmacokinetics of desflurane, sevoflurane, isoflurane, and halothane in pigs.
We tested the prediction that the alveolar washin and washout, tissue time constants, and pulmonary recovery (volume of agent recovered during washout relative to the volume taken up during washin) of desflurane, sevoflurane, isoflurane, and halothane would be defined primarily by their respective solubilities in blood, by their solubilities in tissues, and by their metabolism. We concurrently administered approximately one-third the MAC of each of these anesthetics to five young female swine and determined (separately) their solubilities in pig blood and tissues. The blood/gas partition coefficient of desflurane (0.35 +/- 0.02) was significantly smaller (P less than 0.01) than that of sevoflurane (0.45 +/- 0.02), isoflurane (0.94 +/- 0.05), and halothane (2.54 +/- 0.21). Tissue/blood partition coefficients of desflurane and halothane were smaller than those for the other two anesthetics (P less than 0.05) for all tissue groups. As predicted from their blood solubilities, the order of washin and washout was desflurane, sevoflurane, isoflurane, and halothane (most to least rapid). As predicted from tissue solubilities, the tissue time constants for desflurane were smaller than those for sevoflurane, isoflurane, and halothane. Recovery (normalized to that of isoflurane) of the volume of anesthetic taken up was significantly greater (P less than 0.05) for desflurane (93% +/- 7% [mean +/- SD]) than for halothane (77% +/- 6%), was not different from that of isoflurane (100%), but was less than that for sevoflurane (111% +/- 17%). The lower value for halothane is consistent with its known metabolism, but the lower (than sevoflurane) value for desflurane is at variance with other presently available data for their respective biodegradations.
Anesthetics↗
Epinephrine-induced premature ventricular contractions and changes in arterial blood pressure and heart rate during I-653, isoflurane, and halothane anesthesia in swine.
I653 is a new inhalation anesthetic having especially desirable recovery characteristics because of its very low blood and tissue solubility. Investigations of its cardiovascular and electroencephalographic effects have revealed actions similar to those of isoflurane. However, these studies did not evaluate the potential of I653 to predispose the heart to epinephrine-induced arrhythmias. In this investigation, we studied eight domestic swine to compare the effects of I653 with those of other anesthetics on the cardiac arrhythmogenic actions of intravenously infused epinephrine. I653, isoflurane, and halothane each were given, on separate days, at 0.7-0.8 and at 1.1-1.2 MAC. The rate of infusion of epinephrine needed to produce premature ventricular contractions (PVCs) when the animals were anesthetized with I653 (6.9 +/- 0.7 and 6.6 +/- 0.9 micrograms.kg-1.min-1 at 0.8 and 1.2 MAC) did not differ from that during isoflurane anesthesia (5.7 +/- 1.1 and 6.0 +/- 1.0 micrograms.kg-1.min-1 at 0.7 and 1.1 MAC), but was greater than that required during halothane anesthesia (1.3 +/- 0.2 and 1.1 +/- 0.3 micrograms.kg-1.min-1 at 0.7 and 1.1 MAC). Similar mean arterial blood pressures and heart rates resulted from like infusions of epinephrine during I653 and isoflurane anesthesia. PVCs occurred at lesser infusion rates of epinephrine and at lower mean arterial blood pressures and heart rates with halothane than with I653 or isoflurane. Anesthetic concentration, over the range studied, did not alter the infusion rate of epinephrine required to produce arrhythmias with any anesthetic. The authors conclude that I-653 and isoflurane have similar properties with respect to epinephrine-induced arrhythmias and increases in heart rate and arterial blood pressure.
Anesthetics↗
Cardiovascular safety and actions of high concentrations of I-653 and isoflurane in swine.
The ratio of lethal-to-anesthetic concentration can be used to define the margin of safety of an inhaled anesthetic. In mechanically ventilated swine the fatal concentration of I-653, a new inhaled anesthetic, was 23.9 +/- 0.06% (mean +/- SE), and of isoflurane, 6.22 +/- 0.23%. The ratio of fatal anesthetic concentration-to-MAC for I-653 (2.45 +/- 0.11) was less than that determined for isoflurane (3.02 +/- 0.13; P less than 0.01) but relatively greater than that reported previously for other inhaled anesthetics. As with other inhaled anesthetics, the concentration of I-653 causing cardiovascular collapse exceeds that producing apnea, making cardiovascular collapse during spontaneous ventilation unlikely. Mean aortic blood pressure and cardiac output decreased as linear functions of anesthetic concentration. Values for these variables for isoflurane were greater than those for I-653 at concentrations exceeding 1.5 MAC. Heart rate, blood lactate concentration, and base-deficit did not change with anesthetic depth. Mixed venous PO2, mixed venous oxyhemoglobin saturation, and the ratio of oxygen transport to oxygen consumption remained at or above values in conscious swine but decreased similarly with both anesthetics when anesthetic concentration increased to within 0.5 MAC of the fatal concentration. Thus, the latter three variables, reflecting the fraction of delivered oxygen that is consumed, and "mean" tissue PO2 appear to be useful indices of anesthetic concentrations approaching those producing cardiovascular collapse.(ABSTRACT TRUNCATED AT 250 WORDS)
Anesthetics↗
Halogenation and anesthetic potency.
Previous studies have shown that the anesthetic potency of organic compounds increases as a given halogen is replaced with successively larger halogens. These studies often are limited in the accuracy of determination of potency, rarely correlate potency with physical properties, and usually fail to include ether compounds. Because establishing relationships between structure and activity may shed light on anesthetic action, we studied the new anesthetic, I-537 (CHF2-O-CHBr-CF3), relative to two other ether anesthetics, I-653 (CHF2-O-CHF-CF3) and isoflurane (CHF2-O-CHCl-CF3) for both of which MAC and oil/gas partition coefficients are accurately known. The oil/gas partition coefficient of I-537 at 37 degrees C was found to be 245 +/- 6 (mean +/- SD) and the MAC in Sprague-Dawley rats 0.52 +/- 0.07%. Increasing atomic weight of the 1-ethyl halogen (i.e., F in I-653, Cl in isoflurane, and Br in I-537) progressively decreases MAC (increases potency) and increases lipid solubility. Although potency and solubility change by more than 10-fold, the product of MAC and the oil/gas partition coefficient remains essentially constant (120 +/- 11). However, this product is significantly less than that for other inhaled anesthetics, a finding which either challenges the unitary theory of narcosis or suggests that the lipid solvent classically used to model the site of anesthetic action (olive oil) is inappropriate.
Anesthetics↗
Solubility of I-653, sevoflurane, isoflurane, and halothane in plastics and rubber composing a conventional anesthetic circuit.
This study defines some characteristics of a standard anesthetic circuit that may impede anesthetic induction and recovery with I-653, sevoflurane, isoflurane, and halothane. Partition coefficients for anesthetic circuit components (masks, bellows, bags, airways, and circuit tubes) consistently ranked halothane greater than isoflurane greater than sevoflurane greater than I-653, suggesting a reverse order of washin and washout rates for an anesthetic circuit constructed from similar components. Consistent with this prediction, the concentrations of I-653 increased and decreased more rapidly than those of the other agents at any flow rate during washin (0.5, 1, or 2 L/min gas inflow rates) or washout (1, 3, or 5 L/min) in a conventional anesthetic circuit. The rates of change in I-653 concentration closely approximated the maximal possible theoretical rates. Our results suggest that absorption of I-653 by circuit components or soda lime should not hinder induction of or recovery from anesthesia.
Adsorption↗
Solubility of I-653, sevoflurane, isoflurane, and halothane in human tissues.
Tissue/blood partition coefficients of anesthetics are important indicators of the rate of tissue wash-in and wash-out, and wash-in and wash-out are determinants of the rates of induction of and recovery from anesthesia. In the present study of human tissues, we found that the tissue/blood partition coefficients (for brain, heart, liver, kidney, muscle, and fat) for the new anesthetic I-653 were smaller than those for isoflurane, sevoflurane, and halothane (anesthetics listed in order of increasing tissue/blood partition coefficients). For example, the respective brain/blood partition coefficients were 1.29 +/- 0.05 (mean +/- SD); 1.57 +/- 0.10; 1.70 +/- 0.09; and 1.94 +/- 0.17. This indicates that induction of and recovery from anesthesia with I-653 should be more rapid than with the other agents. The finding of a lower tissue/blood partition coefficient for I-653 parallels the previous finding of a lower blood/gas partition coefficient.
Aged↗