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Biomedical subjects

R Mansilla

Publications and source records attributed to R Mansilla.

6 recordsLinked to original sources
PubMed2004

Comparative assessment of the effects of alfentanil, esmolol or clonidine when used as adjuvants during induction of general anaesthesia.

BACKGROUND AND OBJECTIVE: This randomized, double-blinded, prospective study compared the effects of clonidine, esmolol or alfentanil on the level of hypnosis and haemodynamic responses to intravenous induction of anaesthesia and endotracheal intubation. METHODS: Forty-five patients scheduled for elective surgery were allotted to one of three groups. They were given either alfentanil 3 microg kg(-1) min(-1) (n = 15); esmolol 1 mg kg(-1) min(-1) (n = 16) or clonidine 3 microg kg(-1) (n = 14) as a 10 min infusion. The infusions of alfentanil and esmolol, but not of clonidine, were maintained during endotracheal intubation. Anaesthesia was induced with midazolam (2 mg) and thiopental as required to suppress the eyelash reflex. Atracurium (0.5 mg kg(-1)) was given to produce neuromuscular block. Mean arterial pressure, heart rate, and bispectral index were recorded on arrival (baseline), after study drug infusion, after injecting midazolam and thiopental, as well as after endotracheal intubation. ANOVA and chi2-test were used for analysis. RESULTS: Blood pressure, heart rate and the bispectral index were unaltered by the study drugs, but thiopental requirements were reduced by alfentanil and clonidine (P < 0.014). Mean arterial pressure values (mean +/- standard error of mean) in the alfentanil, esmolol and clonidine groups were: baseline: 107.8 +/- 3.8; 106.6 +/- 3.9; 103.4 +/- 3.7 mmHg; after thiopental: 74.0 +/- 4.2; 85.6 +/- 4.3; 94.2 +/- 4.1 mmHg and after endotracheal intubation: 91.7 +/- 5.3; 114.1 +/- 6.9; 123.6 +/- 5.6 mmHg, respectively (two-way ANOVA, P < 0.001). Mean arterial pressure changed significantly after intubation from baseline (P < 0.001) after alfentanil (-15%) and clonidine (+20%) but not after esmolol (+7%), while the changes between pre- and postintubation values were similar in all groups (24-33% increase). The bispectral index indicated that all patients had an adequate level of hypnosis, but the variability was higher in the esmolol group (P < 0.002). CONCLUSIONS: None of the study drugs blocked the increase in mean arterial pressure induced by endotracheal intubation, but esmolol provided better overall haemodynamic stability. All groups had an adequate level of hypnosis.

Adjuvants, Anesthesia↗
PubMed2003

[Ephedrine shortens the onset of action of rocuronium but not atracurium].

HYPOTHESIS: Ephedrine increases blood flow to muscles and may shorten the onset of action of rocuronium and atracurium. MATERIAL AND METHODS: A prospective study of 80 ASA I-III patients undergoing surgery under general anesthesia and randomized to 4 groups: ephedrine-rocuronium, placebo-rocuronium, ephedrine-atracurium and placebo-atracurium. Atracurium or rocuronium was administered at a dose of 0.04 mg.Kg-1. We monitored neuromuscular function by acceleromyography, ECG and pulse oxymetry, arterial blood pressure (ABP) using an intra-arterial catheter (AT), heart rate (HR) and carbon dioxide pressure. Patient characteristics, time to onset, duration and recovery from the neuromuscular block were recorded. HR and ABP were measured at baseline, 3 minutes after ephedrine dosing, 1 minute after induction, immediately after intubation and 5, 10 and 20 minutes after intubation. RESULTS: Patient characteristics were similar in all groups. The time to onset of neuromuscular block was significantly shorter in the rocuronium and rocuronium-ephedrine groups than in the atracurium groups. Duration and recovery were similar in all groups. Patients premedicated with ephedrine experienced a significant increase in HR for 20 minutes. The only complications were 2 cases of self-limiting sinus tachycardia of less than 130 beats.min-1 in the ephedrine group. CONCLUSIONS: Premeditation with 10 mg of ephedrine decreases the time until onset of action of rocuronium but does not affect the timing of atracurium.

Adult↗
PubMed2000

Algorithmic complexity in the minority game

In this paper, we present our approach for the study of the complexity of Minority Game using tools from thermodynamics and statistical physics. Previous attempts were based on the behavior of volatility, an observable of the financial markets. Our approach focuses on some properties of the binary stream of outcomes of the game. Physical complexity, a magnitude rooted in Kolmogorov-Chaitin theory, allows us to explain some properties of collective behavior of the agents. Mutual information function, a measure related to Shannon's information entropy, was useful to observe a kind of phase transition when applied to the binary string of the whole history of the game.

Journal Article↗