bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of the Alfentanil Canonical Univariate Parameter as a Measure of Opioid Effect on the Electroencephalogram
Authors: Gambus Pedro L. , Gregg Keith M. , Shafer Steven L. 
Published: August 2004

Background
Several parameters derived from the multivariate electroencephalographic (EEG) signal have been used to characterize the effects of opioids on the central nervous system. These parameters were formulated on an empirical basis. A new statistical method, semilinear canonical correlation, has been used to construct a new EEG parameter (a certain combination of the powers in the EEG power spectrum) that correlates maximally with the concentration of alfentanil at the effect site. To date, this new canonical univariate parameter (CUP) has been tested only in a small sample of subjects receiving alfentanil.

Methods
The CUP was tested on EEG data from prior studies of the effect of five opioids: alfentanil (n = 5), fentanyl (n = 15), sufentanil (n = 11), trefentanil (n = 5), and remifentanil (n = 8). We compared the CUP to the commonly used EEG parameter spectral edge, SE95%. The comparison was based on the signal to noise ratio, obtained by fitting a nonlinear pharmacodynamic model to both parameters. The pharmacodynamic parameter estimates obtained using both measurements were also compared.

Results
The values for signal-to-noise ratio were significantly greater for the CUP than for SE95% when considering all the opioids at once. The pharmacodynamic estimates were similar between the two EEG parameters and with previously published results. Semilinear canonical correlation coefficients estimated within each drug group showed patterns similar to each other and to the coefficients in the CUP, but different from coefficients for propofol and midazolam.

Conclusions
Although the CUP was originally designed and tested using alfentanil, we have proven it to be a general measure of opioid effect on the EEG.
Fluorine-19 Nuclear Magnetic Resonance Imaging and Spectroscopy of Sevoflurane Uptake, Distribution, and Elimination in Rat Brain
Authors: Xu Yan , Tang Pei , Zhang Weiguo , Firestone Leonard , Winter Peter M. 
Published: August 2004

Background
Determination of macroscopic and microscopic distribution of general anesthetics can facilitate identification of anatomic, cellular, and molecular loci of anesthetic action. Previous attempts to measure brain anesthetic distributions with fluorine-19 (19F) nuclear magnetic resonance (NMR) imaging were conducted at magnetic field strengths lower than 2 Tesla. All have produced only silhouettes of brain tissue. Difficulties intrinsic to NMR imaging of anesthetics include higher anesthetic solubility in extracranial tissues and the lower limits to spin-echo delay times that can be used in conventional NMR imaging methods. So far, such methods have been unable to capture rapidly decaying brain 19F NMR signals.

Methods
19F NMR imaging and spectroscopy were conducted at 4.7 Tesla using a specially developed NMR probe and new imaging methods. With the new techniques, it was possible to observe directly the uptake, distribution, and elimination in brain of sevoflurane, a fluorinated general anesthetic with special advantages for NMR investigations.

Results
19F NMR images, acquired at different times after sevoflurane administration, clearly showed the distribution of a fluorinated general anesthetic within the brain. Based on continuous transverse relaxation time measurements, sevoflurane signals could be separated into two components, attributable respectively to sevoflurane in a mobile or immobile microenvironment. During washin, there was a delayed accumulation of anesthetic in the mobile microenvironment. During washout, there was a rapid elimination from the immobile microenvironment.

Conclusions
At anesthetizing concentrations, sevoflurane distributes heterogeneously in the brain. Sevoflurane in the brain tissue contributes mostly to the immobile component of the 19F signal, whereas that in the surrounding adipose and muscle tissues contributes mostly to the mobile component. Imaging and spectroscopic results suggest that the immobile component of sevoflurane is associated with the general anesthetic effects of the agent.
In Vitro Effects of Eltanolone on Rat Myocardium
Authors: Riou Bruno , Ruel Patrick , Hanouz Jean-Luc , Langeron Olivier , Lecarpentier Yves , Viars Pierre 
Published: August 2004

Background
Eltanolone is a new short-acting intravenous induction agent. However, its effects on intrinsic myocardial contractility remain unknown.

Methods
The effects of eltanolone and its solvent (soya bean emulsion) on the intrinsic contractility of rat left ventricular papillary muscles were investigated in vitro (Krebs-Henseleit solution, 29 degrees C, pH 7.40, Ca2+ 0.5 mM, stimulation frequency 12 pulses/min). We studied contraction; relaxation; contraction-relaxation coupling under high and low loads; and postrest potentiation.

Results
Eltanolone (0.1, 0.3, 1, 3, and 10 micrograms.ml-1) induced no significant inotropic effect, as shown by the lack of changes in maximum unloaded shortening velocity and active isometric force. Eltanolone did not significantly modify the contraction-relaxation coupling under low load, suggesting that it did not modify calcium uptake by the sarcoplasmic reticulum. Eltanolone did not significantly modify the contraction-relaxation coupling under high load, suggesting that it did not modify calcium myofilament sensitivity. Eltanolone decreased the postrest potentiation in a concentration-dependent manner (from 150 +/- 14% to 118 +/- 9% at 10 micrograms.ml-1, P < 0.001), suggesting a decrease in the maximum capacity of calcium release by the sarcoplasmic reticulum, whereas its solvent did not. However, eltanolone did not slow postrest potentiation recovery, as shown by the absence of significant changes in the recovery slope, tau (4.5 +/- 1.4 vs. 3.8 +/- 1.0 beats; difference not statistically significant).

Conclusions
Eltanolone induced no significant inotropic effect on rat myocardium. It induced a decrease in the calcium release function of the sarcoplasmic reticulum, but this effect was not sufficiently important to modify the inotropic properties.
Inhaled Anesthetics Alter the Determinants of Coronary Collateral Blood Flow in the Dog
Authors: Mignella Ronnie , Buffington Charles W. 
Published: August 2004

Background
Whether coronary steal is induced by inhaled anesthetic agents remains controversial in part because multiple factors determine collateral blood flow.

Methods
We used an established model to determine how halothane, isoflurane, and desflurane affect the hemodynamic determinants of coronary collateral blood flow. Twelve dogs were studied 4-5 weeks after ameroid constrictor implantation. Retrograde flow draining from the occluded artery was measured as an index of collateral flow after antegrade embolization. Pressure in the supplying artery at the origin of the collaterals was estimated with a stop-flow technique. These techniques allow calculation of collateral segment resistance and the resistances of the supply artery upstream and downstream from the origin of the collaterals.

Results
None of the inhaled anesthetics affected collateral segment resistance. Downstream (arteriolar) resistance of the supplying artery was decreased by desflurane (-45%), isoflurane (-35%), and halothane (-15%), lowering pressure at the origin of the collaterals, an effect that was partially offset by a decrease in upstream resistance. Retrograde flow was unaffected by isoflurane and halothane but decreased by about 20% during desflurane administration.

Conclusions
Inhaled anesthetics have many effects on segmental resistance and pressure in the coronary circulation. These findings help explain conflicting results from previous studies and provide a useful model for investigating the effects of inhaled agents on small coronary arteries.
Halothane and Isoflurane Inhibit Endothelium-derived Relaxing Factor-dependent Cyclic Guanosine Monophosphate Accumulation in Endothelial Cell-Vascular Smooth Muscle Co-cultures Independent of an Effect on Guanylyl Cyclase Activation
Authors: Johns Roger A. , Tichotsky Alexandra , Muro Michael , Spaeth James P. , Le Cras Timothy D. , Rengasamy Appavoo 
Published: August 2004

Background
Interaction of inhalational anesthetics with the nitric oxide signaling pathway and the mechanism of such effects are controversial. The aim of this study was to clarify the sites and mechanism of inhalational anesthetic interaction with the vascular nitric oxide and guanylyl cyclase signaling pathway.

Methods
To specifically study the mechanism of anesthetic interaction with the nitric oxide-guanylyl cyclase pathway, cultured vascular smooth muscle and endothelial cell-vascular smooth muscle (EC-VSM) co-culture models were chosen. Monolayer cultures of VSM with or without cultured endothelial cells grown on microcarrier beads were preequilibrated with anesthetic and stimulated with agonists. The effect of inhalational anesthetics on cyclic guanosine monophosphate (GMP) content of unstimulated VSM and of VSM in which soluble guanylyl cyclase had been activated by the endothelium-independent nitrovasodilators, sodium nitroprusside, nitroglycerin, or nitric oxide was determined. Experiments were also performed to assess the effect of inhalational anesthetics on unstimulated endothelial cell-vascular smooth muscle co-cultures and on co-cultures in which nitric oxide synthase and subsequent cyclic GMP production had been activated by the receptor-mediated agonists bradykinin and adenosine triphosphate and by the non-receptor-mediated calcium ionophore A23187.

Results
Increasing concentrations of halothane and isoflurane from 0.5 to 5% had no effect on basal cyclic GMP concentrations in cultured VSM alone or in endothelial cell-vascular smooth muscle co-cultures, and had no effect on sodium nitroprusside, nitroglycerin, or nitric oxide stimulated cyclic GMP accumulation in cultured VSM. In agonist-stimulated co-cultures, however, halothane and isoflurane significantly (P < 0.05) inhibited increases in cyclic GMP concentration in response to both receptor- and non-receptor-mediated nitric oxide synthase activating agents.

Conclusions
Inhalational anesthetics do not stimulate or inhibit basal cyclic GMP production in co-cultures or VSM, suggesting that inhalational anesthetics do not activate soluble or particulate guanylyl cyclase and do not activate nitric oxide synthase. Inhalational anesthetics do not inhibit nitrovasodilator-induced cyclic GMP formation, suggesting a lack of interference with soluble guanylyl cyclase activation. Inhalational anesthetics inhibit both agonist and calcium ionophore-stimulated nitric oxide-dependent cyclic GMP accumulation in endothelial cell-vascular smooth muscle co-cultures. Consistent with previous vascular ring studies, anesthetics appear to inhibit nitric oxide-guanylyl cyclase signaling distal to receptor activation in the endothelial cell and proximal to nitric oxide activation of guanylyl cyclase.
Characteristics of the Analgesic Effects and Drug Interactions of Intrathecal Carbachol in Rats
Authors: Abram Stephen E. , O'Connor Therese C. 
Published: August 2004

Background
Intrathecal carbachol produces consistent analgesia in animals without appreciable adverse effects. Little is known about the ability of this drug to provide analgesia as stimulus intensity is increased. Likewise, there are few data regarding interactions between carbachol and other intrathecal analgesics.

Methods
Using two different noxious radiant heat intensities, one applied to each hind limb, analgesic effects of 1, 3, 10, and 30 micrograms intrathecal carbachol on paw withdrawal latencies were measured. Similar testing was done for intrathecal morphine and clonidine. ED50 fractions (1/2, 1/4, 1/8, 1/16) of drug combinations of carbachol-morphine and carbachol-clonidine were administered, responses to the low intensity stimulus were recorded, and the ED50 of each combination was established and isobolographic analysis of the drug interactions was carried out.

Results
The 30-micrograms dose of carbachol was associated with transient agitation, salivation, and hind limb weakness. No other adverse effects were noted. The ED50 (95% confidence interval) of intrathecal carbachol was 2.34 micrograms (1.34-4.04) for low intensity stimulation and 12.64 micrograms (4.18-38.25) for high intensity. There was no significant difference between high- and low-intensity ED50 values for intrathecal morphine and clonidine. The analgesic effect of the carbachol-morphine and carbachol-clonidine combinations were significantly greater than the calculated additive effects. The ED50 for the carbachol-morphine combination was 12% of the expected additive value and the ED50 for the carbachol-clonidine combination was 30% of the expected additive value.

Conclusions
Intrathecal carbachol provides analgesia to noxious thermal stimulation of the hind paw in rats. It is relatively less effective at providing analgesia than intrathecal morphine or clonidine when stimulus intensity is raised. Intrathecal carbachol is synergistic when combined with intrathecal morphine or clonidine.
Hepatic Heat Shock and Acute-phase Gene Expression Are Induced Simultaneously after Celiotomy in the Anesthetized Pig
Authors: Pannen Benedikt H. J. , Maeda Kaori , Ayuse Takao , Brienza Nicola , Revelly Jean-Pierre , Robotham James L. , Buchman Timothy G. 
Published: August 2004

Background
The liver plays a central role in the whole organism's response to injury. Expression of hepatic acute-phase and heat-shock genes likely contributes to the restoration of homeostasis after stressful events. However, after prolonged ischemia, hepatic transcription of heat-shock genes can exclude the simultaneous transcription of acute-phase genes. The issue of whether hepatic 72-kd heat-shock protein (hsp72) gene expression is induced under perioperative conditions that do not result in prolonged liver ischemia and whether this might further affect the expression of the acute-phase reactant inter-alpha-trypsin inhibitor (alpha-Ti) was examined.

Methods
Pigs were anesthetized with sodium pentobarbital and ketamine hydrochloride, tracheally intubated, and their lungs ventilated. After celiotomy, a hepatic biopsy sample was obtained. Arterial blood pressure, cardiac output, and total hepatic blood flow were measured. Subsequent biopsies were obtained at 1, 2, 3, 4, and 6 h after the initial biopsy. Arterial norepinephrine concentrations were measured using high-pressure liquid chromatography. Nuclear runoff (run on) analysis and Northern blotting were applied to estimate changes in hsp72 and alpha-Ti gene transcription rates and RNA levels. Western blotting was used to estimate changes in hsp72 levels.

Results
Hemodynamic parameters did not change significantly over time. Arterial norepinephrine concentrations were increased at all time points. Hepatic hsp72 RNA levels increased up to sixfold while nuclear runoff assays did not detect significant changes in hsp72 gene transcription rates. The increases in hsp72 RNA levels correlated with accumulation of hsp72 (up to sevenfold). Increases in alpha-Ti transcription rates up to 42-fold were associated with respective increases in alpha-Ti RNA levels (up to 17-fold).

Conclusions
These data demonstrate that hepatic expression of hsp72 is not confined to conditions that lead to prolonged liver ischemia but is also part of the response of the liver to surgery under general anesthesia. Furthermore, these conditions are permissive for the simultaneous RNA expression of the acute-phase reactant alpha-Ti.
Parental Presence and a Sedative Premedicant for Children Undergoing Surgery
Authors: Kain Zeev N. , Mayes Linda C. , Wang Shu-Ming , Caramico Lisa A. , Krivutza Dawn M. , Hofstadter Maura B. 
Published: August 2004

Background
Although some anesthesiologists use oral sedatives or parental presence during induction of anesthesia (PPIA) to treat preoperative anxiety in children, others may use these interventions simultaneously (e.g., sedatives and PPIA). The purpose of this investigation was to determine whether this approach has advantages over treating children with sedatives alone.

Methods
The child's and the parental anxiety throughout the perioperative period was the primary endpoint of the study. Parental satisfaction was the secondary endpoint. Subjects (n = 103) were assigned randomly to one of two groups: a sedative group (0.5 mg/kg oral midazolam) or a sedative and PPIA group. Using standardized measures of anxiety and satisfaction, the effects of the interventions on the children and parents were assessed. Statistical analysis (varimax rotation) of the satisfaction questionnaire items resulted in two factors that described satisfaction of the separation process and satisfaction of the overall care provided.

Results
Anxiety in the holding area, at entrance to the operating room, and at introduction of the anesthesia mask did not differ significantly between the two groups (F[2,192] = 1.26, P = 0.28). Parental anxiety after separation, however, was significantly lower in the sedative and PPIA group (F[2,93] = 4.46, P = 0.037). Parental satisfaction with the overall care provided (-0.28 +/- 1.2 vs. 0.43 +/- 0.26, P = 0.046) and with the separation process (-0.30 +/- 1.2 vs. 0.47 +/- 0.20, P = 0.03) was significantly higher among the sedative and PPIA group compared with the sedative group.

Conclusions
PPIA in addition to 0.5 mg/kg oral midazolam has no additive effects in terms of reducing a child's anxiety. Parents who accompanied their children to the operating room, however, were less anxious and more satisfied.
Pharmacokinetics and Arteriovenous Differences in Clevidipine Concentration following a Short- and a Long-term Intravenous Infusion in Healthy Volunteers
Authors: Ericsson Hans , Bredberg Ulf , Eriksson Ulf , Jolin-Mellgård Åse , Nordlander Margareta , Regårdh Carl G. 
Published: August 2004

Background
Clevidipine is an ultra-short-acting calcium antagonist developed for reduction and control of blood pressure during cardiac surgery. The objectives of the current study were to determine the pharmacokinetics of clevidipine after 20-min and 24-h intravenous infusions, and to determine the relation between the arterial and venous concentrations and the hemodynamic responses to clevidipine in healthy volunteers.

Methods
Four volunteers received clevidipine for 20 min, and eight subjects were administered clevidipine intravenously for 24 h at two different dose rates. Arterial and venous blood samples were drawn for pharmacokinetic evaluation, and blood pressure and heart rate were recorded.

Results
A triexponential disposition model described the pharmacokinetics of clevidipine. The mean arterial blood clearance of clevidipine was 0.069l/kg-1/min-1 and the mean volume of distribution at steady state was 0.19 l/kg. The duration of the infusion had negligible effect on the pharmacokinetic parameters, and the context-sensitive half-time for clevidipine, simulated from the mean pharmacokinetic parameters derived after 24 h infusion at the highest dose, was less than 1 min. The arterial blood levels reached steady state within 2 min of the start of infusion and were about twice as high as those in the venous blood at steady state. The peak response preceded the peak venous concentration and was slightly delayed from the peak arterial blood concentration.

Conclusion
Clevidipine is a high clearance drug with a small volume of distribution, resulting in extremely short half-lives in healthy subjects. The initial rapid increase in the arterial blood concentrations and the short equilibrium time between the blood and the biophase suggest that clevidipine can be rapidly titrated to the desired effect.
Maximum Tolerated Dose of Nalmefene in Patients Receiving Epidural Fentanyl and Dilute Bupivacaine for Postoperative Analgesia
Authors: Dougherty Thomas B. , Porche Vivian H. , Thall Peter F. 
Published: August 2004

Background
This study investigated the ability of the modified continual reassessment method (MCRM) to determine the maximum tolerated dose of the opioid antagonist nalmefene, which does not reverse analgesia in an acceptable number of postoperative patients receiving epidural fentanyl in 0.075% bupivacaine.

Methods
In the postanesthetic care unit, patients received a single intravenous dose of 0.25, 0.50, 0.75, or 1.00 microg/kg nalmefene. Reversal of analgesia was defined as an increase in pain score of two or more integers above baseline on a visual analog scale from 0 through 10 after nalmefene administration. Patients were treated in cohorts of one, starting with the lowest dose. The maximum tolerated dose of nalmefene was defined as that dose, among the four studied, with a final mean probability of reversal of anesthesia (PROA) closest to 0.20 (ie., a 20% chance of causing reversal). The modified continual reassessment method is an iterative Bayesian statistical procedure that, in this study, selected the dose for each successive cohort as that having a mean PROA closest to the preselected target PROA of 0.20.

Results
The modified continual reassessment method repeatedly updated the PROA of each dose level as successive patients were observed for presence or absence of ROA. After 25 patients, the maximum tolerated dose of nalmefene was selected as 0.50 microg/kg (final mean PROA = 0.18). The 1.00-microg/kg dose was never tried because its projected PROA was far above 0.20.

Conclusions
The modified continual reassessment method facilitated determination of the maximum tolerated dose ofnalmefene . Operating characteristics of the modified continual reassessment method suggest it may be an effective statistical tool for dose-finding in trials of selected analgesic or anesthetic agents.
Prophylactic Ondansetron in Prevention of Postoperative Nausea and Vomiting following Pediatric Strabismus Surgery
Authors: Sadhasivam Senthilkumar , Shende Dilip , Madan Rashmi 
Published: August 2004

Background
This study evaluated the antiemetic effectiveness, dose-response, and clinical usefulness of prophylactic ondansetron in the prevention of postoperative nausea and vomiting (PONV) in children undergoing strabismus repair.

Method
The authors observed 180 children, American Society of Anesthesiologists physical status I or II, 2-12 yr of age, who were undergoing strabismus repair. After induction of anesthesia with halothane and nitrous oxide in oxygen or intravenous thiopental, children received either placebo (saline) or intravenous ondansetron in doses of 25, 50, 75, 100, and 150 /microg/kg (n = 30). The trachea was intubated and ventilation was controlled. Perioperative analgesic and fluid requirements were standardized. Episodes of nausea and vomiting were recorded for the first 24 h postoperatively. Data such as nonsurrogate (parental satisfaction scores and duration of postanesthesia care unit stay) and therapeutic (numbers needed to prevent and harm) outcome measures were collected.

Results
The incidences of PONV in the placebo and 25-, 50-, 75-, 100-, and 150-,microg/kg ondansetron groups were 83, 77, 47, 30, 30, and 27%, respectively. The incidence was less in the 75(P = 0.002), 100- (P = 0.002), and 150-microg/kg (P < 0.001) ondansetron groups compared with placebo. Duration of stay in the postanesthesia care unit was shorter in the 75-, 100-, and 150-microg/kg ondansetron groups (P < 0.002) compared with the placebo group. Parental assessment scores for the child's perioperative experience and the positive number needed to prevent PONV were also better and favorable in the 75-, 100-, and 150-microg/kg ondansetron groups compared with the placebo group. The incidence (P > 0.99) and severity (P = 0.63) of PONV were similar in the 75- and 150-microg/kg ondansetron groups. Surrogate, nonsurrogate, and therapeutic outcome measures revealed that 75 microg/kg ondansetron provided the same benefits as did 100 and 150 microg/kg.

Conclusion
The routine prophylactic use of ondansetron at a dose of 75 microg/kg is as effective as 150 microg/kg in preventing PONV and improving the "true" outcome measures after strabismus repair in children.