Journal of anesthesia
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Journal of anesthesia · Jul 1990
Evaluation of conventional weaning criteria in patients with acute respiratory failure.
We evaluated the reliability of conventional weaning criteria from a ventilator during 33 weaning trials on 25 patients with acute respiratory failure (ARF). Of 13 criteria, a ratio of maximal voluntary ventilation to minute ventilation (MV) >2, a vital capacity >12 ml.kg(-1), a spontaneous respiratory rate <25 breaths.min(-1), and a MV <10 l.min(-1) appeared to be useful for predicting successful weaning outcome. ⋯ The present study demonstrates that conventional criteria are frequently inaccurate for predicting weaning outcomes and suggests that the use of some of these criteria may unnecessarily prolong the length of ventilator support. Since ventilation of most patients with poor oxygenation can be successfully discontinued by placing them on a continuous positive airway pressure system, these results suggest that the improvement of oxygenation is not an indispensable prerequisite for weaning from mechanical ventilators.
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We examined the effect of enflurane on diaphragmatic contractility in six anesthetized mechanically ventilated dogs. The diaphragmatic force was assessed from transdiaphragmatic pressure (Pdi) developed at functional residual capacity against an occluded airway during cervical phrenic nerve stimulation. Pdi-stimulus frequency relationship was compared at three levels of anesthesia, namely 1, 1.5, and 2 MAC (minimum alveolar concentration) of enflurane. ⋯ Pdi of 20 Hz stimulation was significantly decreased at 2 MAC as compared to those at 1 and 1.5 MAC. We conclude that enflurane decreases contractility of the diaphragm mainly through impairment of the neuromuscular transmission and/or membrane excitability. Part of its effects is, however, probably related to the impairment of excitation-contraction coupling, as suggested by the depression of Pdi at 2 MAC in response to 20 Hz stimulation.
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Journal of anesthesia · Apr 1990
Comparative study of intravenous administration of Ringer's lactate, Ringer's acetate and 5% glucose containing these Ringer's solutions in human being.
The effects of the administration of Ringer's lactate (L) and Ringer's acetate (A) solution on blood biochemistry in human subjects operated for tympanoplasty under general anesthesia were investigated. And the feasibilities of the clinical use of Ringer's lactate (LD) and Ringer's acetate (AD) solution containing 5% glucose were also assessed. In all cases the rate of infusion was 500 ml for initial 20 min, and then 5 ml.hr(-1).kg(-1) B. ⋯ In both LD and AD group, the higher blood concentrations of lactate, pyruvate, acetate and glucose were found than in L and A group. Urinary excretions of these metabolites were much higher in LD and AD group than in L and A group. So glucose containing Ringer's lactate or acetate solutions should be administered in appropriate amounts and rate not to induce clinically significant metabolic alterations.
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Journal of anesthesia · Apr 1990
Airway occlusion pressure (P0.1)-a useful predictor for the weaning outcome in patients with acute respiratory failure-.
Twenty-five patients who required mechanical ventilatory support (MVS) after major surgery or severe burns were studied to determine whether airway occlusion pressure (P(0.1)) is a clinically useful indicator to predict the success or failure of the weaning trial. A total of 33 weaning trials were attempted on these patients. Of the 33 trials, 24 were followed by successful weaning and 9 by failure. ⋯ The alveolar-arterial P(O)(2) gradient, with an F i(O)(2) of 1.0, in weaning success and failure showed no statistical difference. In contrast, all patients in the success group had a P(0.1) of less than 3.5 cmH(2)O and those in the failure group had a P(0.1) of greater than 3.5 cmH(2)O ( P < 0.001). We conclude that P(0.1) is a clinically superior indicator for discontinuing MVS in patients with acute respiratory failure.
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Journal of anesthesia · Apr 1990
Enflurane reduces the excitation and inhibition of dorsal horn WDR neuronal activity induced by BK injection in spinal cats.
The effects of enflurane (0.5%, 1.5% and 2.5%) on the excitation and inhibition of dorsal horn wide dynamic range (WDR) neuronal activity induced by bradykinin (BK) injection was studied in spinal cats. Extracellular activity was recorded in the dorsal horn from single WDR neurons responding to noxious and non-noxious stimuli applied to the cutaneous receptive fields on the left hind paw foot pads of decerebrate, spinal cord transected (L(1-2)) cats. When 10 microg of BK was injected into the femoral artery ipsilateral to the recording site as the noxious test stimulus, 24 of 26 WDR neurons (92%) gave excitatory responses and 2 (8%) gave inhibitory responses. ⋯ However, the inhibitory neuronal activity in WDR neurons was significantly depressed by 0.5%, 1.5% and 2.5% enflurane. We have found that enflurane reduces the excitation as well as the inhibition of dorsal horn WDR neuronal activity induced by BK injection. These results suggest that the reduction of excitatory and inhibitory responses produced by noxious stimulation is likely to be the fundamental basis of the enflurane-induced anesthetic state in terms of WDR neurons.