bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of the ARX-derived Auditory Evoked Potential Index as an Indicator of Anesthetic Depth
Authors: Struys Michel M. R. F. , Jensen Erik Weber , Smith Warren , Smith N. Ty , Rampil Ira , Dumortier Frank J. E. , Mestach Christel , Mortier Eric P. 
Published: August 2004

Background
Autoregressive modeling with exogenous input of middle-latency auditory evoked potential (A-Line autoregressive index [AAI]) has been proposed for monitoring anesthetic depth. The aim of the current study was to compare the accuracy of this new index with the Bispectral Index (BIS), predicted effect-site concentration of propofol, and hemodynamic measures.

Methods
Twenty female patients scheduled for ambulatory gynecologic surgery received effect compartment controlled infusion of propofol. Target effect-site concentration was started at 1.5 microg/ml and increased every 4 min by 0.5 microg/ml. At every step, sedation level was compared with monitoring values using different clinical scoring systems and reaction to noxious stimulus.

Results
Bispectral Index, AAI, and predicted propofol effect-site concentration were accurate indicators for the level of sedation and loss of consciousness. Hemodynamic variables were poor indicators of the hypnotic-anesthetic status of the patient. BIS correlated best with propofol effect-site concentration, followed by AAI. Hemodynamic measurements did not correlate well. No indicators predicted reaction to noxious stimulus. Poststimulus, BIS and AAI showed an increase as a result of arousal. This reaction occurred more rapidly with the AAI than with BIS.

Conclusion
Bispectral Index, AAI, and predicted propofol effect-site concentration revealed information on the level of sedation and loss of consciousness but did not predict response to noxious stimulus.
Automatic CPAP Compared with Conventional Treatment for Episodic Hypoxemia and Sleep Disturbance after Major Abdominal Surgery
Authors: Drummond Gordon B. , Stedul Kristina , Kingshott Ruth , Rees Karen , Nimmo Alastair F. , Wraith Peter , Douglas Neil J. 
Published: August 2004

Background
After major surgery, analgesia with opioids can cause obstructive apnea and intermittent hypoxemia, probably from loss of upper airway control. Since this resembles the obstructive sleep apnea syndrome, we tested the possibility that nasal continuous positive airway pressure (nCPAP) would reduce episodes of reduced oxygen saturation and sleep disruption. Because oxygen therapy is frequent after surgery, we also assessed the effect of oxygen on sleep disruption.

Methods
We recruited 48 patients about to have major abdominal surgery. We present data for 34 patients: 27 who received patient-controlled intravenous morphine and 7 who received epidural opioid. Treatment was randomized to either nCPAP or conventional therapy with an oxygen mask. Alternate periods of administration of air and 35% oxygen were used in both groups. If the oxygen saturation as measured by pulse oximetry was consistently <90% on air, the patient was withdrawn from the study. We measured sleep, arousals, oxygenation, episodes of desaturation, and disturbances of respiration. Values are given as median and quartiles.

Results
The median proportion of time awake was 65% (45-79%) among control patients and 74% (55-87%) among those undergoing nCPAP. Oxygen administration did not affect the sleep pattern. The median frequency of arousals per hour of sleep was very similar in each group: during air breathing from nCPAP, 125 (76-187), and during air breathing by mask, 116 (84-187). Oxygen therapy had no effect. Oxygenation and hypoxemic events were not improved by nCPAP. Oxygen therapy improved oxygenation and reduced but did not eliminate episodes of desaturation.

Conclusions
Nasal CPAP does not improve sleep and oxygenation or reduce hypoxemic events in the first night after major abdominal surgery.
Usefulness of Nitric Oxide Treatment for Pulmonary Hypertensive Infants during Cardiac Anesthesia
Authors: Kadosaki Mamoru , Kawamura Takae , Oyama Kotaro , Nara Noriko , Wei Jicheng , Mori Naohisa 
Published: August 2004

Background
The beneficial effect of inhaled nitric oxide (NO) on pulmonary hypertension is well known. However, the indications for NO inhalation therapy for pulmonary hypertension associated with congenital heart lesions are still unclear. The aim of the current study was to seek a measure that would predict the effectiveness of inhaled NO in infants undergoing cardiac surgery.

Methods
Forty-six infants with pulmonary hypertension were studied. Pulmonary vascular resistance (PVR) measured at the time of cardiac catheterization was used as an indicator and compared with pulmonary arterial pressure/systemic blood pressure ratio (Pp/Ps) at the time of weaning from cardiopulmonary bypass. The effect of 40 ppm of inhaled NO for 15 min was evaluated in patients whose Pp exceeded systemic values.

Results
Preoperative PVR correlated positively with Pp/Ps at the time of weaning from cardiopulmonary bypass (r2 = 0.86; P < 0.05; n = 46). A Pp/Ps greater than or equal to 1 was not observed in any cases in which the preoperative PVR values were less than 7 Wood units m2; Pp/Ps ratio greater than or equal to 1 occurred in four patients. Each of these had PVR values greater than 7 Wood units m2. Three of these patients who had PVR values in the 7-12 Wood units m2 range were responsive to inhaled NO. The fourth patient, whose PVR value was greater than 15 Wood units m2, was unresponsive. Lung biopsy specimens were obtained in two patients whose preoperative PVR values were greater than 10 Wood units m2.

Conclusion
Preoperative PVR correlates reasonably well with postbypass Pp/Ps.
Analgesic Effects of Intravenous Lidocaine and Morphine on Postamputation Pain
Authors: Wu Christopher L. , Tella Prabhav , Staats Peter S. , Vaslav Rachel , Kazim Debra A. , Wesselmann Ursula , Raja Srinivasa N. 
Published: August 2004

Background
Phantom and stump pains, common sequelae of limb amputations, are significant impediments to rehabilitation of amputees. The pathophysiology and optimal treatment of postamputation pain states are unclear. While stump pain may result from neuromas in the stump, phantom pain is thought to be related to cortical reorganization. The authors hypothesized that morphine and lidocaine may have differential effectiveness on stump and phantom pains.

Methods
The authors conducted a randomized double-blind, active-placebo-controlled, crossover trial to compare the analgesic effects of intravenous morphine and lidocaine on postamputation stump and phantom pains. An intravenous bolus followed by an intravenous infusion of morphine (0.05 mg/kg bolus + 0.2 mg/kg infusion over 40 min), lidocaine (1 mg/kg bolus + 4 mg/kg infusion) and the active placebo, diphenhydramine (10 mg bolus + 40 mg infusion), were performed on three consecutive days. Phantom and stump pain ratings and sedation scores were recorded at 5-min intervals using a 0-100 visual analog scale. Pain measures were initiated 30 min before drug infusion and continued until 30 min after the end of infusion. Subjects' self-reported pain relief and satisfaction were assessed at the end of each infusion.

Results
Thirty-one of 32 subjects enrolled completed the study. Eleven subjects had both stump and phantom pains, 11 and 9 subjects had stump and phantom pain alone, respectively. Baseline pain scores were similar in the three drug groups. Compared with placebo, morphine reduced both stump and phantom pains significantly (P < 0.01). In contrast, lidocaine decreased stump (P < 0.01), but not phantom pain. The changes in sedation scores for morphine and lidocaine were not significantly different from placebo. Compared with placebo, self-reported stump pain relief was significantly greater for lidocaine (P < 0.05) and morphine (P < 0.01), while phantom pain relief was greater only for morphine (P < 0.01). Satisfaction scores were significantly higher for lidocaine (mean +/- SD: 39.3 +/- 37.8, P < 0.01) and morphine (45.9 +/- 35.5, P < 0.01) when compared with placebo (9.6 +/- 21.0).

Conclusions
Stump pain was diminished both by morphine and lidocaine, while phantom pain was diminished only by morphine, suggesting that the mechanisms and pharmacological sensitivity of stump and phantom pains are different.
Performance of Infusion Pumps during Hyperbaric Conditions
Authors: Lavon Haim , Shupak Avi , Tal Dror , Ziser Avishai , Abramovich Amir , Yanir Yoav , Shoshani Oren , Gil Amnon , Leiba Ronit , Nachum Zohar 
Published: August 2004

Background
Many hyperbaric facilities use infusion pumps inside the chamber. It is therefore important to ensure that this equipment will perform accurately during hyperbaric conditions. The authors tested the function and accuracy of the Imed 965 and Infutec 520 volumetric infusion pumps, the Easy-pump MZ-257 peristaltic infusion pump, and the Graseby 3100 syringe pump.

Methods
The authors calculated the deviations of infused volumes at low and high rates (12-18 and 60-100 ml/h) on three different hyperbaric protocols (up to 2.5, 2.8, and 6 atmospheres absolute [ATA]), resembling a standard hyperbaric oxygen treatment and US Navy treatment tables used for decompression illness and for arterial gas embolism. Two examples of each pump model were examined in every experiment.

Results
The Easy-pump MZ-257 failed to function completely beyond a chamber pressure of 1.4 ATA, making it unsuitable for use inside the hyperbaric chamber. The Graseby 3100 failed to respond to all keyboard functions at 2.5-2.8 ATA, making it unsuitable for use in most hyperbaric treatments. The Imed 965 performed within an acceptable volume deviation (< or =10%) during most hyperbaric conditions. During the compression phase of the profiles used, and for the low infusion rates only, exceptional volume deviations of 20-40% were monitored. The Infutec 520 demonstrated an acceptable deviation (within 10%) throughout all the hyperbaric profiles used, unaffected by changes in ambient pressure or infusion rate.

Conclusions
Commercially available infusion pumps operating during hyperbaric conditions demonstrate substantial variations in performance and accuracy. It is therefore important that the hyperbaric facility staff make a careful examination of such instruments to anticipate possible deviations in the accuracy of the equipment during use.
Oxygen Reverses Deficits of Cognitive Function and Memory and Increased Heart Rate Induced by Acute Severe Isovolemic Anemia
Authors: Weiskopf Richard B. , Feiner John , Hopf Harriet W. , Viele Maurene K. , Watson Jessica J. , Kramer Joel H. , Ho Rachel , Toy Pearl 
Published: August 2004

Background
Erythrocytes are transfused to improve oxygen delivery and prevent or treat inadequate oxygenation of tissues. Acute isovolemic anemia subtly slows human data processing and degrades memory, increases heart rate, and decreases self-assessed energy level. Erythrocyte transfusion is efficacious in reversing these effects of acute anemia. We tested the hypothesis that increasing arterial oxygen pressure (Pao2) to 350 mmHg or greater would supply sufficient oxygen to be equivalent to augmenting hemoglobin concentration by 2-3 g/dl and thus reverse the effects of acute anemia.

Methods
Thirty-one healthy volunteers, aged 28 +/- 4 yr (mean +/- SD), were tested with verbal memory and standard, computerized neuropsychologic tests before and twice after acute isovolemic reduction of their hemoglobin concentration to 5.7 +/- 0.3 g/dl. Two sets of tests were performed in randomized order at the lower hemoglobin concentration: with the volunteer breathing room air or oxygen. The subject and those administering the tests and recording the results were unaware which gas was administered. As an additional control for duration of the experiment, 10 of these volunteers also completed the same tests on a separate day, without alteration of hemoglobin concentration, at times of the day similar to those on the experimental day. Heart rate, mean arterial blood pressure, and self-assessed sense of energy were recorded at the time of each test.

Results
Reaction time for digit-symbol substitution test increased, delayed memory was degraded, mean arterial pressure and energy level decreased, and heart rate increased at a hemoglobin concentration of 5.7 g/dl (all P < 0.05). Increasing Pao2 to 406 +/- 47 mmHg reversed the digit-symbol substitution test result and the delayed memory changes to values not different from those at the baseline hemoglobin concentration of 12.7 +/- 1.0 g/dl, and decreased heart rate (P < 0.05). However, mean arterial pressure and energy level changes were not altered with increased Pao2 during acute anemia.

Conclusion
The authors confirmed that acute isovolemic anemia subtly slows human reaction time, degrades memory, increases heart rate, and decreases energy level. The findings of this study support the hypothesis that increasing Pao2 to 350 mmHg or greater by breathing oxygen reverses all of these effects of acute anemia except for decreased energy.
Sleep Tendency as a Measure of Recovery after Drugs Used for Ambulatory Surgery
Authors: Lichtor J. Lance , Alessi Richard , Lane Bradford S. 
Published: August 2004

Background
Although tests of psychomotor function indicate that drug effects after ambulatory anesthesia are short-lived, patients often feel washed out for long periods of time. Among the psychomotor tests that measure different motor and cognitive functions, none directly measures sleepiness or alertness. The authors hypothesized that sleepiness, measured by a sleep latency test, would be a more sensitive indicator of drug effect after an anesthetic than psychomotor tests. The second objective was to determine a sedation regimen that produced the least residual effect.

Methods
On four separate occasions, volunteers (N = 12) received an injection of propofol 2.5 mg/kg; propofol 2.0 mg/kg and fentanyl 2 microg/kg; propofol 2.0 mg/kg and midazolam 2 mg/70 kg; or midazolam 0.07 mg/kg and fentanyl 2 microg/kg. Dependent measures included the multiple sleep latency test (MSLT), Maddox Wing and digit symbol substitution tests, auditory and visual reaction times, and a divided attention task.

Results
The multiple sleep latency test demonstrated sleepiness up to 4 h after injection, and in some patients, sleepiness continued up to 8 h afterward. Psychomotor function was impaired only at 2 h after injection of the drug combination.

Conclusion
The multiple sleep latency test may be a more sensitive measure of a drug's effect than other tests of psychomotor function. For up to 8 h after an injection of midazolam and fentanyl, patients must consider driving or operating heavy machinery unsafe activities.
Mechanisms Underlying Greater Sensitivity of Neonatal Cardiac Muscle to Volatile Anesthetics
Authors: Prakash Y.S. , Seckin Inanc , Hunter Larry W. , Sieck Gary C. 
Published: August 2004

Background
In neonatal heart, plasma membrane Na+-Ca2+ exchange (NCX) and Ca2+ influx channels play greater roles in intracellular Ca2+ concentration [Ca2+]i regulation compared with the sarcoplasmic reticulum (SR). In neonatal (aged 0-3 days) and adult (aged 84 days) rat cardiac myocytes, we determined the mechanisms underlying greater sensitivity of the neonatal myocardium to inhibition by volatile anesthetics.

Methods
The effects of 1 and 2 minimum alveolar concentration halothane and sevoflurane on Ca2+ influx during electrical stimulation in the presence or blockade of NCX and the Ca2+ channel agonist BayK8644 were examined. [Ca2+]i responses to caffeine were used to examine anesthetic effects on SR Ca2+ release (via ryanodine receptor channels) and reuptake (via SR Ca2+ adenosine triphosphatase). Ca2+ influx via NCX was examined during rapid activation in the presence of the reversible SR Ca2+ adenosine triphosphatase inhibitor cyclopiazonic acid and ryanodine to inhibit the SR. Efflux mode NCX was examined during activation by extracellular Na+ in the absence of SR reuptake.

Results
Intracellular Ca2+ concentration transients during electrical stimulation were inhibited to a greater extent in neonates by halothane (80%) and sevoflurane (50%). Potentiation of [Ca2+]i responses by BayK8644 (160 and 120% control in neonates and adults, respectively) was also blunted by anesthetics to a greater extent in neonates. [Ca2+]i responses to caffeine in neonates ( approximately 30% adult responses) were inhibited to a lesser extent compared with adults (35 vs. 60% by halothane). Both anesthetics inhibited Ca2+ reuptake at 2 minimum alveolar concentration, again to a greater extent in adults. Reduction in NCX-mediated influx was more pronounced in neonates (90%) compared with adults (65%) but was comparable between anesthetics. Both anesthetics also reduced NCX-mediated efflux to a greater extent in neonates. Potentiation of NCX-mediated Ca2+ efflux by extracellular Na+ and NCX-mediated Ca2+ influx by intracellular Na+ were both prevented by halothane, especially in neonates.

Conclusions
These data indicate that greater myocardial depression in neonates induced by volatile anesthetics may be mediated by inhibition of NCX and Ca2+ influx channels rather than inhibition of SR Ca2+ release.
Interaction of Morphine, Fentanyl, Sufentanil, Alfentanil, and Loperamide with the Efflux Drug Transporter P-glycoprotein
Authors: Wandel Christoph , Kim Richard , Wood Margaret , Wood Alastair 
Published: August 2004

Background
The efflux transporter P-glycoprotein, a member of the adenosine triphosphate-binding cassette superfamily, is a major determinant of the pharmacokinetics and pharmacodynamics of the opioid loperamide, a well-recognized antidiarrheal agent. Animal studies indicate that P-glycoprotein limits morphine entry into the brain. In this study, the authors examined whether other opioids of importance to anesthesiologists such as fentanyl, sufentanil, and alfentanil, and also morphine-6-glucuronide and morphine-3-glucuronide, are P-glycoprotein substrates and whether, in turn, these opioids act also as P-glycoprotein inhibitors.

Methods
The transcellular movement of the various opioids, including loperamide and morphine, was assessed in L-MDR1 (expressing P-glycoprotein) and LLC-PK1 cell monolayers (P-glycoprotein expression absent). A preferential basal-to-apical versus apical-to-basal transport in the L-MDR cells but not the LLC-PK1 cells is seen for P-glycoprotein substrates. In addition, the effect of the various opioids on the transcellular movement of the prototypical P-glycoprotein substrate digoxin was examined in Caco-2 cell monolayers. IC50 values were calculated according to the Hill equation.

Results
Loperamide was a substrate showing high dependence on P-glycoprotein in that basal-apical transport was nearly 10-fold greater than in the apical-basal direction in L-MDRI cells. Morphine also showed a basal-to-apical gradient in the L-MDR1 cell monolayer, indicating that it too is a P-glycoprotein substrate, but with less dependence than loperamide in that only 1.5-fold greater basal-apical directional transport was observed. Fentanyl, sufentanil, and alfentanil did not behave as P-glycoprotein substrates, whereas the morphine glucuronides did not cross the cell monolayers at all, whether P-glycoprotein was present or not. Loperamide, sufentanil, fentanyl, and alfentanil inhibited P-glycoprotein-mediated digoxin transport in Caco-2 cells with IC50 values of 2.5, 4.5, 6.5, and 112 microm, respectively. Morphine and its glucuronides (20 microm) did not inhibit digoxin (5 microm) transport in Caco-2 cells, and therefore IC50 values were not determined.

Conclusions
Opioids have a wide spectrum of P-glycoprotein activity, acting as both substrates and inhibitors, which might contribute to their varying central nervous system-related effects.
Isoflurane Preconditions Myocardium against Infarction via Release of Free Radicals
Authors: Müllenheim Jost , Ebel Dirk , Fräβdorf Jan , Preckel Benedikt , Thämer Volker , Schlack Wolfgang 
Published: August 2004

Background
Isoflurane exerts cardioprotective effects that mimic the ischemic preconditioning phenomenon. Generation of free radicals is implicated in ischemic preconditioning. The authors investigated whether isoflurane-induced preconditioning may involve release of free radicals.

Methods
Sixty-one alpha-chloralose-anesthetized rabbits were instrumented for measurement of left ventricular (LV) pressure (tip-manometer), cardiac output (ultrasonic flowprobe), and myocardial infarct size (triphenyltetrazolium staining). All rabbits were subjected to 30 min of occlusion of a major coronary artery and 2 h of subsequent reperfusion. Rabbits of all six groups underwent a treatment period consisting of either no intervention for 35 min (control group, n = 11) or 15 min of isoflurane inhalation (1 minimum alveolar concentration end-tidal concentration) followed by a 10-min washout period (isoflurane group, n = 12). Four additional groups received the radical scavenger N-(2-mercaptoproprionyl)glycine (MPG; 1 mg. kg-1.min-1) or Mn(III)tetrakis(4-benzoic acid)porphyrine chloride (MnTBAP; 100 microg.kg-1.min-1) during the treatment period with (isoflurane + MPG; n = 11; isoflurane + MnTBAP, n = 9) or without isoflurane inhalation (MPG, n = 11; MnTBAP, n = 7).

Results
Hemodynamic baseline values were not significantly different between groups (LV pressure, 97 +/- 17 mmHg [mean +/- SD]; cardiac output, 228 +/- 61 ml/min). During coronary artery occlusion, LV pressure was reduced to 91 +/- 17% of baseline and cardiac output to 94 +/- 21%. After 2 h of reperfusion, recovery of LV pressure and cardiac output was not significantly different between groups (LV pressure, 83 +/- 20%; cardiac output, 86 +/- 23% of baseline). Infarct size was reduced from 49 +/- 17% of the area at risk in controls to 29 +/- 19% in the isoflurane group (P = 0.04). MPG and MnTBAP themselves had no effect on infarct size (MPG, 50 +/- 14%; MnTBAP, 56 +/- 15%), but both abolished the preconditioning effect of isoflurane (isoflurane + MPG, 50 +/- 24%, P = 0.02; isoflurane + MnTBAP, 55 +/- 10%, P = 0.001).

Conclusion
Isoflurane-induced preconditioning depends on the release of free radicals.
Preparation of the Siemens KION Anesthetic Machine for Patients Susceptible to Malignant Hyperthermia
Authors: Petroz Guy C. , Lerman Jerrold 
Published: August 2004

Background
Preparation of anesthetic machines for use with malignant hyperthermia-susceptible (MHS) patients requires that the machines be flushed with clean fresh gas. We investigated the washout of inhalational anesthetics from the KION anesthetic machine.

Methods
In part 1, halothane was circulated through KION anesthetic machines for either 2 or 12 h using a test lung. The times to washout halothane (to 10 parts per million [ppm]) first, from the internal circuitry and second, from the ventilator-patient cassette (without the carbon dioxide absorber) were determined at 5 and 10 l/min fresh gas flow (FGF). In part 2, the rates of washout of halothane or isoflurane from either the KION or Ohmeda Excel 210 machines were compared. The effluent gases were analyzed using calibrated Datex Capnomac Ultima (Helsinki, Finland) and a Miran LB2 Portable Ambient Air Analyzer (Foxboro, Norwalk, CT).

Results
Halothane was washed out of the internal circuitry of the KION within 5 min at 10 l/min FGF. Halothane was eliminated from the ventilator-patient cassette in 22 min at the same FGF. The times to reach 10 ppm concentration of halothane and isoflurane in the KION at 10 l/min FGF, 23 to 25 min, was four-fold greater than those in the Ohmeda Excel 210, 6 min.

Conclusions
To prepare the KION anesthetic machine for MHS patients, the machine without the carbon dioxide absorber must be flushed with 10 l/min FGF for at least 25 min to achieve 10 ppm anesthetic concentration. This FGF should be maintained throughout the anesthetic to avoid increases in anesthetic concentration in the FGF.