Showing papers in "Anesthesiology in 1977"
387 citations
TL;DR: No wonder you activities are, reading will be always needed, it is not only to fulfil the duties that you need to finish in deadline time, but also to encourage your mind and thoughts.
Abstract: No wonder you activities are, reading will be always needed. It is not only to fulfil the duties that you need to finish in deadline time. Reading will encourage your mind and thoughts. Of course, reading will greatly develop your experiences about everything. Reading blood brain barrier in physiology and medicine is also a way as one of the collective books that gives many advantages. The advantages are not only for you, but for the other peoples with those meaningful benefits.
320 citations
298 citations
TL;DR: It is proposed that the anesthetic-modified phase separation behavior of the membrane may alter neural function by a combination of the following effects: inhibition of conformational changes of intrinsic membrane proteins; prevention of the association of protein subunits to form polymeric ion channels; depression of transmitter release by preventing fusion of vesicles containing synaptic transmitter with the membrane of the presynaptic terminal.
Abstract: This paper relates research on anesthetic effects on lipid membrane systems to mechanisms of neural function. A unitary theory of anesthesia based on anesthetic-induced changes in fluid-solid-phase separations in the lipid region of nerve membranes is presented. It is suggested that anesthetics act
230 citations
189 citations
TL;DR: The effects of prolonged enflurane and halothane administration on urine-concentrating ability were determined in volunteers by examining their responses to vasopressin before and on days 1 and 5 after anesthesia, and the threshold level for inorganic fluoride nephrotoxicity is lower than previously suspected.
Abstract: The effects of prolonged enflurane and halothane administration on urine-concentrating ability were determined in volunteers by examining their responses to vasopressin before anesthesia and on days 1 and 5 after anesthesia. A significant decrease in maximum urinary osmolality of 264 +/- 34 mOsm/kg (26 per cent of the preanesthetic value) was present on day 1 after enflurane anesthesia, whereas subjects anesthetized with halothane had a significant increase in maximum urinary osmolality of 120 +/- 44 mOsm/kg. Serum inorganic fluoride level peaked at 33.6 muM and remained above 20 muM for approximately 18 hours. Thus, the threshold level for inorganic fluoride nephrotoxicity is lower than previously suspected.
182 citations
TL;DR: Various amounts of carbon dioxide were removed through an extracorporeal membrane lung in spontaneously breathing lambs and the decrease in alveolar ventilation was proportional to the fraction of total carbon dioxide removed by the membrane lung.
Abstract: Various amounts of carbon dioxide were removed through an extracorporeal membrane lung in spontaneously breathing lambs. The decrease in alveolar ventilation was proportional to the fraction of total carbon dioxide removed by the membrane lung. When extracorporeal CO2 removal approximated CO2 production (VCO2), alveolar ventilation almost ceased. Pulmonary ventilation can be controlled by extracorporeal carbon dioxide removal.
177 citations
TL;DR: An EEG change common to various anesthetics may increase the clinical usefulness of EEG monitoring and may signal loss of awareness, and is interpreted as support for physical solution-lipid solubility theories of anesthetic action.
Abstract: EEG amplitude dominance in awake man is posterior. During EEC monitoring in patients, the authors observed the abrupt appearance of anterior amplitude dominance during induction of anesthesia with halothane, enflurane, or thiopental. This EEG change is coincident with loss of eyelid reflex and loss
154 citations
TL;DR: At clinically common concentrations of lidocaine, significant decreases in anesthetic requirements should be anticipated.
Abstract: The effects of various plasma concentrations of lidocaine on nitrous oxide anesthesia in man and halothane requirements in the dog were studied The response to incision of the skin was observed in 20 patients who were anesthetized with nitrous oxide, 70% inspired, and oxygen, 30%, plus various plasma levels of lidocaine In addition, changes in the MAC of halothane in dogs were observed at various levels of lidocaine In both circumstances lidocaine concentrations of 3 to 6 microgram/ml decreased anesthetic requirements approximately 10 to 28% At clinically common concentrations of lidocaine, significant decreases in anesthetic requirements should be anticipated
144 citations
TL;DR: The results demonstrate that the change in the EEG to an “anesthetic” pattern, which occurs at concentrations well below MAC, is accompanied by an abrupt metabolic depression and it is speculated that these events coincide with the onset of functional depression.
Abstract: The relationship between cerebral oxygen consumption (CMRO2) and anesthetic concentration has been assumed (based upon isolated measurements) to be approximately linear at concentrations less than 1 MAC. The shapes of the anesthetic dose-response curves for both CMRO2 and cerebral blood flow (CBF) were examined by multiple measurements made at small, progressive concentration increments from 0 to 2 MAC halothane (six dogs), enflurane (six dogs), and isoflurane (six dogs), and during a constant 23 mg/kg/hr infusion of thiopental (six dogs). The EEG was continuously recorded and changes in EEG patterns from "awake" to "anesthetic" were correlated with changes in anesthetic concentration, CBF, and CMRO2. The significance of changes in the slopes of regression lines for CMRO2 before, during and after changes in EEG patterns from "awake" to "anesthetic" were then determined. Contrary to previous inferences, CMRO2 dose-response curves were found to be nonlinear at anesthetic concentrations less than 1 MAC for all anesthetics studied. CMRO2 decreased precipitously until a stable "anesthetic" pattern was observed on the EEG; thereafter, CMRO2 decreased at a markedly reduced rate. The onset of this change occurred at concentrations well below MAC for the inhalational anesthetics. With the thiopental infusion, CMRO2 decreased most rapidly during the first 25 minutes. With halothane and enflurane, CBF was maximal during the period of transition in the EEG from an "awake" to an "anesthetic" pattern. CBF was elevated at all concentrations of isoflurane studied. CBF decreased rapidly during thiopental infusion until the EEG pattern changed from "awake" to "anesthetic" and then more slowly. The results demonstrate that the change in the EEG to an "anesthetic" pattern, which occurs at concentrations well below MAC, is accompanied by an abrupt metabolic depression. It is speculated that these events coincide with the onset of functional depression.
TL;DR: A major component of the ventilatory depression associated with halothane anesthesia results from the preferential suppression of intercostal muscle function with relative sparing of diaphragmatic activity, which is associated with a marked decrease in rib cage ventilation.
Abstract: The ventilatory response to CO2 was subdivided into that portion due to increasing rib cage expansion, and that due to increased diaphragmatic descent. Five children were studied, awake, and anesthetized with halothane, 0.8-0.9%. During anesthesia there was a 67+/-8% reduction (mean+/-SE) in the slope of the response of overall ventilation to an increase in CO2. This was primarily due to an 89+/-8% reduction in the recruitment of rib cage ventilation (P less than .001). There was no significant change in the slope of the diaphragmatic response (anesthetized value 19+/-21% less than control), although the response curve was shifted to the right so that a higher CO2 concentration was needed to stimulate a given level of diaphragmatic excursion. Additional measurements of the inspiratory intercostal electromyogram in three adult subjects documented a rapid, profound depression of intercostal activity with halothane anesthesia that was associated with a marked decrease in rib cage ventilation. The authors conclude that a major component of the ventilatory depression associated with halothane anesthesia results from the preferential suppression of intercostal muscle function with relative sparing of diaphragmatic activity.
TL;DR: The incidence of arterial occlusion increases linearly as the ratio of cannula outer diameter to vessel-lumen diameter increases.
Abstract: Radial arterial function was evaluated in 108 patients following 24 hours of percutaneous cannulation with either 18- or 20-gauge cannulas. Arteriography, Doppler ultrasound examination, and Allen's test disclosed an 8 per cent incidence of radial-artery occlusion following cannulation with 20-gauge cannulas, compared with a 34 per cent incidence of occlusion with 18-gauge cannulas (P less than .05). Vessels that occluded were significantly smaller in diameter than were patent vessels (mean 2.00 +/- .09 mm SE vs. 2.22 +/- .05 mm, P less than .05). Occluded vessels also contained significantly greater amounts of thrombotic material (0-3+) just prior to decannulation than those that remained patent (2.42 +/- .13 vs. 1.20 +/- .11,P less than .001). The incidence of arterial occlusion increases linearly as the ratio of cannula outer diameter to vessel-lumen diameter increases.
TL;DR: It is concluded that N2O, isoflurane, and fluroxene locally inhibit regional HPV and via this mechanism increase total venous admixture, while halothane and enflurane do not have this effect.
Abstract: Administration of N2O, fluroxene and isoflurane to the left lower lobe (LLL) of dogs anesthetized with pentobarbital was previously shown to inhibit LLL hypoxic pulmonary vasoconstriction (HPV). Using the same experimental model, the present study examined the effect of whole-lung administration of N2O, fluroxene, isoflurane, halothane, and enflurane on left-lower-lobe HPV. Selective ventilation of the LLL with N2 alone caused blood flow to the lobe to decrease 53.3 +/- 3.0 per cent. Responses to LLL hypoxia were remeasured during administration of inhalation anesthetics at 1 and 2 MAC to both the LLL and the rest of the lung. Isoflurane and fluroxene progressively inhibited and at 2 MAC halved lobar HPV. N2O (one third MAC) caused slight but significant inhibition, while halothane and enflurane caused slight and nonsignificant changes in lobar HPV. These effects of whole-lung administration of anesthetics on HPV were almost identical to those obtained when the administration was confined to the test lobe alone. It is concluded that N2O, isoflurane, and fluroxene locally inhibit regional HPV and via this mechanism increase total venous admixture, while halothane and enflurane do not have this effect.
TL;DR: Serotonin, 100 or 200 µg, administered into the lumbar intrathecal space, produced an analgesic effect for as long as 40 minutes, and behavioral and morphologic observations after serotonin injections showed no adverse reaction.
Abstract: It has been suggested that serotonin neurons and their pathways may mediate sensitivity to nociceptive stimuli by activating the descending inhibitory mechanisms at the spinal cord. This antinociceptive effect may be induced by direct administration of serotonin into the cerebrospinal fluid pathways. The experiment is designed to demonstrate the changes in the tail-flick response latency after the intrathecal injection of serotonin. Serotonin, 100 or 200 microgram, administered into the lumbar intrathecal space, produced an analgesic effect for as long as 40 minutes. Behavioral and morphologic observations after serotonin injections showed no adverse reaction. It is assumed that serotonin molecules penetrate the spinal cord tissue and activate the antinociceptive serotonergic pathyways.
TL;DR: The EEG patterns of several animals anesthetized with either cyclopropane or halothane changed to patterns consistent with lighter planes of anesthesia after naloxone administration, suggesting that anesthetics may release an endogenous morphine-like factor in the central nervous system.
Abstract: The effect of naloxone, a narcotic antagonist, on the response of animals to painful stimuli during anesthesia was studied. Bats were anesthetized with cyclopropane, halothune, or enflurane in groups of 12. Following induction, inspired anesthetic concentration was gradually reduced to a point at wh
TL;DR: In dogs with pulmonary edema, PEEP's of 5 and 10 cm H2O resulted in dramatic reductions in shunt, virtual obliteration of low VA/Q regions, and market improvement in Pao2, however, at 15 and 20 cm H 2O PEP's highVA/Q and dead space ventilation with CO2 retention again developed in all but the most severely affected dogs.
Abstract: The effects of positive end-expiratory pressure (PEEP) at 5, 10, 15, and 20 cm H2O on the distribution of ventilation-perfusion (VA/Q) ratios was determined in four normal dogs and in ten with oleic acid-induced acute hemorrhagic pulmonary edema. Tidal volume and frequency were held constant at all times with mechanical ventilation during intravenous pentobarbital and gallamine anesthesia. Normal dogs had little or no shunt, and no areas of low (less than 0.1) or high VA/Q (greater than 10.0) at zero end-expiratory pressure (intermittent positive-pressure breathing). In these animals increasing PEEP caused progressive depression of cardiac output, associated with an increase in ventilation to both high VA/Q and unperfused regions. PEEP greater than or equal to 10 cm H2O resulted in a reduction in Pao2 and an increase in PaCO2. In dogs with pulmonary edema, PEEP's of 5 and 10 cm H2O resulted in dramatic reductions in shunt, virtual obliteration of low VA/Q regions, and market improvement in Pao2. However, at 15 and 20 cm H2O PEEP's high VA/Q and dead space ventilation with CO2 retention again developed in all but the most severely affected (shunt greater than 40%) dogs.
TL;DR: The results suggest that the systemic and cerebral effects of halothane and nitroprusside are similar and at a mean arterial pressure of 50 torr are of little consequence.
Abstract: In 62 dogs, hypotension to a mean arterial pressure of either 40 or 50 torr (equivalent to a cerebral perfusion pressure of 30 or 40 torr, respectively) for one hour was induced by hemorrhage (oligemia), trimethaphan, halothane, or sodium nitroprusside. Before and during the period of hypotension, the following were measured: mean arterial blood pressure, cardiac output, whole-body O2 consumption, cerebral blood flow, cerebral O2 consumption, arterial blood gases, blood O2 content, and lactate, pyruvate, glucose, epinephrine, and norepinephrine concentrations. At the end of the period of hypotension, brain biopsies were taken for determination of adenosine triphosphate, phosphocreatine, lactate, and pyruvate concentrations. In an additional eight dogs following one hour of hypotension (at 40 torr) induced by one of the four techniques, the brains were perfused with carbon black, removed, and examined. In another ten dogs following hypotension (at 40 torr) induced with either halothane or trimethaphan, the animals were observed for three days and then killed for examination of the brain. Dogs maintained at a mean arterial pressure of 40 torr, despite differences in cerebral blood flow, demonstrated metabolic disturbances compatible with systemic and cerebral hypoxia. These were greatest in those dogs given nitroprusside in excess of 1.0 mg/kg, presumably due to cyanide toxicity. In dogs maintained at 50 torr, metabolic disturbances were minimal or absent in the halothane- and nitroprusside-treated dogs but were still apparent in the oligemic and trimethaphan-treated dogs. Carbon black infusions revealed no evidence of non-homogeneous flow. Three of the ten dogs observed for three days had persistent post-hypotension neurologic dysfunction. Two of these were given trimethaphan. The results suggest that the systemic and cerebral effects of halothane and nitroprusside (at doses less than 1.0 mg/kg) are similar and at a mean arterial pressure of 50 torr are of little consequence. By contrast, hypotension induced by trimethaphan or oligemia results in detectable metabolic alterations even at a pressure of 50 torr.
TL;DR: It is concluded that halothane anesthesia produces depression of baroreflex control of heart rate in man.
Abstract: Baroreflex control of heart rate was determined during three awake control situations and during two depths of halothane anesthesia in man. Baroreflex function was quantitated by calculating the pressor test slope from the R-R interval change on the ECG produced by a pharmacologically induced presso
TL;DR: The effects of equipotent concentrations of enflurane, isofluranes, and halothane on isolated human uterine muscle have been evaluated and it is shown that they are equally depressing to isolated human uterusine muscle.
Abstract: The effects of equipotent concentrations of enflurane, isoflurane, and halothane on isolated human uterine muscle have been evaluated. Three anesthetic concentrations (0.5, 1.9, and 1.5 MAC) were studied. Specimens included myometrial strips from 45 non-gravid and seven gravid uteri. Both groups of muscle strips showed significant (P less than 0.05) and progressive depression of contractility with all anesthetics. However, the extents of depression at each anesthetic level studied were similar with all drugs. Enflurane, isoflurane, and halothane are equally depressing to isolated human uterine muscle.
TL;DR: The present results indicate that the uncharged molecules fluidize the lecithin membrane by unsaturable nonspecific binding, and the possible effect of the charged molecules upon the fluidity of natural membranes remains to be established.
Abstract: Disordering, fluidizing and dilating effects of anesthetics upon cell membranes are well recognized. The fluidization can be precisely measured with phospholipid membranes. When phospholipids are dispersed in water, they form globules of bilayer structure. These model membranes undergo transition between crystalline (ordered and less fluid) and liquid crystalline (less ordered and fluid) phases according to the temperature, the degree of packing of each molecule, and the chemical environment. The phase transition occurs in a cooperative fashion and the turbidity of the dispersion changes abruptly, clear in liquid crystalline phase and turbid in crystalline phase. The present study was undertaken to quantitate the fluidizing effects of local anesthetics on dipalmitoyl lecithin (DPL) bilayer dispersion by measuring the turbidity change. Tetracaine, bupivacaine, lidocaine, and procaine were studied. They all depressed the phase-transition temperature. The binding of the drugs to the model membrane followed unsaturable kinetics, and the pH titration curve showed that only uncharged molecules were active. The freezing point depression was analyzed according to the Van't Hoff model. From this model, the partition coefficients of the uncharged molecules between DPL and water were estimated: lidocaine 76, procaine 159, bupivacaine 812, and tetracaine 1,405. The concentration of local anesthetics in the DPL phase needed to decrease the phase-transition temperature 1 degree C showed a constant value of 0.132 M. The concentration of local anesthetics in the DPL phase is a function of pH, partition coefficient, and volume ratio between the DPL and aqueous phases. The normalized values of the fluidizing action of these drugs at physiologic conditions correlated well with their nerve-blocking potencies. The present results indicate that the uncharged molecules fluidize the lecithin membrane by unsaturable nonspecific binding. The possible effect of the charged molecules upon the fluidity of natural membranes remains to be established.