Anesthesia and analgesia
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Anesthesia and analgesia · Mar 1999
Randomized Controlled Trial Clinical TrialThe intubating laryngeal mask airway with and without fiberoptic guidance.
We conducted this feasibility study using the intubating laryngeal mask airway (ILMA) and a polyvinyl chloride tracheal tube to compare success rates, hemodynamic effects, and postoperative morbidity with two methods of tracheal intubation. After ethics approval and informed consent, 90 healthy ASA physical status I or II women with normal airways were enrolled in the randomized, controlled study. After a standardized inhaled anesthesia induction protocol, tracheal intubations using ILMA with fiberoptic guidance (ILMA-FOB) and ILMA inserted blindly without fiberoptic guidance (ILMA-Blind) were compared with the control group of direct laryngoscopy (laryngoscopy group). All 90 patients were successfully ventilated. For tracheal intubation, success rates were equal in all three groups (97%). Total intubation times were longer for the ILMA-FOB group (77 s versus 48.5 s for laryngoscopy and 53.5 s for ILMA-Blind). The laryngoscopy group had a larger increase in mean arterial blood pressure to tracheal intubation. There were no differences in postoperative sore throat or hoarseness among the groups. In conclusion, success rates are equally high for tracheal intubation using ILMA-Blind and ILMA-FOB techniques in women with normal airways. ⋯ The intubating laryngeal mask airway (ILMA) can be used as a primary airway for oxygenation and ventilation. Both methods of tracheal intubation using the ILMA were equally successful. Postoperative morbidity in the ILMA groups was similar to that in the laryngoscopy group. For women with normal airways, both the ILMA inserted blindly and the ILMA with fiberoptic guidance are suitable alternatives to laryngoscopy for tracheal intubation.
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Anesthesia and analgesia · Mar 1999
Pretreatment with dexmedetomidine: altered indices of anesthetic depth for halothane in the neuraxis of cats.
The sedative and anesthetic-sparing ability of the alpha2-adrenergic agonist dexmedetomidine is well documented. In this study, we identified the effects of halothane, with and without dexmedetomidine, on hemodynamic and electroencephalographic (EEG) variables and quantified the concentration of halothane resulting in various anesthetic depth indices mediated through the central nervous system (CNS) in chronically instrumented cats. Halothane was given alone or after dexmedetomidine (15 microg/kg p.o.). In both groups, four indices of anesthetic depth--minimum alveolar anesthetic concentration (MAC; no movement to noxious stimuli), MAC(BAR) (no autonomic response to noxious stimuli), MAC(BS) (EEG burst suppression), and MAC(ISOELECTRIC) (EEG isoelectricity)--were determined. Halothane decreased arterial blood pressure, heart rate, and higher frequency components of the EEG before the onset of burst suppression and isoelectricity. Dexmedetomidine pretreatment augmented the actions of halothane on arterial pressure, heart rate, and the EEG. Dexmedetomidine reduced the halothane concentrations resulting in MAC (from 1.22% +/- 0.06% to 0.89% +/- 0.08%) and MAC(BAR) (from 1.81% +/- 0.05% to 1.1% +/- 0.10%), but not those resulting in MAC(BS) (3.01% +/- 0.17% vs 3.14% +/- 0.10%) or MAC(ISOELECTRIC) (4.39% +/- 0.26% vs 4.65% +/- 0.12%). These results suggest that dexmedetomidine does not alter various CNS-mediated indices of anesthetic action to equivalent degrees and that there are dissimilar degrees of an anesthetic-sparing action at different levels of the neuraxis. ⋯ The anesthetic adjuvant dexmedetomidine seems to differentially alter central nervous system-mediated indices of anesthetic action. Lower brainstem or spinal determinants of anesthetic depth (movement and hemodynamic responses) are more attenuated than those of higher brain functions, such as the electroencephalogram.
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Anesthesia and analgesia · Mar 1999
Clinical TrialThe effects of in vitro hemodilution with gelatin, hydroxyethyl starch, and lactated Ringer's solution on markers of coagulation: an analysis using SONOCLOT.
Blood-saving strategies have recently been established to avoid allogeneic transfusion during surgery or after trauma. This includes an expanding use of crystalloids and colloids. These solutions interfere with coagulation systems, but quantitative measurements are still lacking. The SONOCLOT (Sienco Company, Morrison, CO) analysis (SCT), a viscoelastic test, measures clot formation and includes information on the cellular, as well as the plasmatic coagulation, system. To quantify hemodilutional effects on in vitro coagulation, we studied gelatin (G), hydroxyethyl starch 6% (HES; molecular weight 450,000), and lactated Ringer's solution (RL) in 33% and 66% dilutions measuring routines laboratory and SCT variables. Hemodilution with RL tended to increase in vitro coagulability. Among the tested colloids, G had the least impact on markers of coagulation. G33% did not differ significantly from the undiluted control group. HES had the largest impact on markers of coagulation compared with G and RL. In conclusion, SCT provides a fast and easy to perform bedside test to quantify in vitro hemodilution. ⋯ The effects of progressive hemodilution on coagulation are difficult to measure. SONOCLOT analyses provide an easy to perform test with fast information on cellular and plasmatic coagulation properties. Among colloids, hydroxyethyl starch has the largest impact on markers of coagulation compared with gelatin or lactated Ringer's solution.
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Anesthesia and analgesia · Mar 1999
Clinical TrialThe nature of spontaneous recovery from mivacurium-induced neuromuscular block.
The hypothesis of this study was that, in a given patient, recovery from a tracheal intubating dose of mivacurium would indicate the time course of spontaneous recovery after discontinuation of an infusion of mivacurium. Thirty-eight male patients consented to participate in the study. After induction of anesthesia and endotracheal intubation, the ulnar nerve was stimulated with train-of-four (TOF) stimuli at 12-s intervals. Patients received 0.3 mg/kg mivacurium in two evenly divided doses of 0.15 mg/kg each, separated by 30 s. Complete ablation of TOF responses occurred in most patients. Once the first twitch in the TOF (T ) had recovered to 25% of its baseline height, a mivacurium infusion was begun to maintain 95% suppression of T1. As surgery was nearing completion, the infusion was discontinued, and neuromuscular function was allowed to recover spontaneously. Data were analyzed for recovery intervals after the administration of the initial doses of mivacurium and after discontinuation of the infusion. Analysis of variance was used to determine the strength of correlation between the time from administration of the initial 0.3 mg/kg dose to 5% recovery of T1 and the times to recovery of TOF ratios of 70% and 90%. The 25%-75% recovery interval after discontinuation of the infusion ranged from 2.8 to 11.3 min. The time interval after administration of mivacurium 0.3 mg/kg to 5% recovery of T1 correlated with both the time to recovery of a TOF ratio of 70% and 90%. Recovery to a TOF of 90% after discontinuation of the infusion required approximately the same amount of time as recovery to 5% T1 after the administration of 0.3 mg/kg mivacurium. Each patient's recovery of neuromuscular function after discontinuation of a mivacurium infusion was related to his recovery after the administration of 0.3 mg/kg mivacurium. Therefore, the need for pharmacologic antagonism of block can be anticipated well before the end of an anesthetic. ⋯ Mivacurium (0.3 mg/kg) was administered to 38 patients. As they began to recover muscle strength, a mivacurium infusion was begun and later discontinued as surgery was nearing completion. Each patient's early recovery (administration to 5% recovery of T1) after the initial dose of mivacurium correlated well with more complete recovery of muscle strength after discontinuation of an infusion. This relationship enables early prediction of recovery speed after a mivacurium infusion.
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Anesthesia and analgesia · Mar 1999
Minimum alveolar anesthetic concentration of volatile anesthetics in normal and cardiomyopathic hamsters.
Minimum alveolar anesthetic concentrations (MAC) values of volatile anesthetics in cardiovascular diseases remain unknown. We determined MAC values of volatile anesthetics in spontaneously breathing normal and cardiomyopathic hamsters exposed to increasing (0.1%-0.3% steps) concentrations of halothane, isoflurane, sevoflurane, or desflurane (n = 30 in each group) using the tail-clamp technique. MAC values and their 95% confidence interval were calculated using logistic regression. In normal hamsters, inspired MAC values were: halothane 1.15% (1.10%-1.20%), isoflurane 1.62% (1.54%-1.69%), sevoflurane 2.31% (2.22%-2.40%), and desflurane 7.48% (7.30%-7.67%). In cardiomyopathic hamsters, they were: halothane 0.89% (0.83%-0.95%), isoflurane 1.39% (1.30%-1.47%), sevoflurane 2.00% (1.85%-2.15%), and desflurane 6.97% (6.77%-7.17%). Thus, MAC values of halothane, isoflurane, sevoflurane, and desflurane were reduced by 23% (P < 0.05), 14% (P < 0.05), 13% (P < 0.05), and 7% (P < 0.05), respectively in cardiomyopathic hamsters. ⋯ Minimum alveolar anesthetic concentrations of volatile anesthetics were significantly lower in cardiomyopathic hamsters than in normal hamsters.