Journal of anesthesia
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Journal of anesthesia · Dec 1995
Evaluation of a delivery system and monitors for ventilator administration of nitric oxide.
The aim of this study was to compare nitric oxide (NO) and nitrogen dioxide (NO2) measurements obtained by chemiluminescence and electrochemical monitors using a delivery system for ventilator administration of NO. The formation of NO2 in this system and the efficacy of a soda-lime absorber to scavenge NO2 from inspiratory gas were also evaluated. Various concentrations of NO without and with soda lime were administered to a model lung via a Servo ventilator 900C with controlled ventilation by setting mass-flow regulators to maintain desired concentrations of NO in 80% O2. ⋯ NO, although a high concentration of NO2 appeared in the breathing circuit without soda lime. Four hundred grams of soda lime continued to absorb NO2 effectively during long-term administration of inhaled NO. These findings suggest that electrochemical monitoring is accurate and clinically useful for measurements of NO and NO2 concentrations, and that low doses of inhaled NO can be administered safely and reliably with the NO delivery system using a soda-lime absorber and mass-flow regulators.
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Journal of anesthesia · Dec 1995
Interactions of nicardipine to inhalation anesthetics sevoflurane and isoflurane.
The hemodynamic effects and pharmacokinetics of nicardipine under general anesthesia were compared between two different volatile anesthetics, sevoflurane and isoflurane. Sixteen adult neurosurgery patients were divided into sevoflurane and isoflurane groups. Anesthesia was maintained with either sevoflurane or isoflurane (0.5-1.5%) and nitrous oxide in oxygen. ⋯ The sevoflurane group had a significantly longer elimination half-life, a larger area under the plasma concentration curve, and smaller clearance of nicardipine compared to the isoflurane group. In summary, the effects of nicardipine on blood pressure and heart rate were significantly longer under isoflurane anesthesia than under sevoflurane anesthesia. However, the etabolism and excretion of nicardipine were significantly delayed under sevoflurane anesthesia.
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Journal of anesthesia · Dec 1995
Difference of train-of-four fade induced by nondepolarizing neuromuscular blocking drugs: a theoretical consideration on the underlying mechanisms.
Nondepolarizing neuromuscular blocking drugs induce train-of-four (TOF) fade, i.e., the reduction of the fourth to the first twitch height in a train under TOF stimulation. It has been observed that the degree of TOF fade varies with the drug used and is inversely correlated with the potencies of the drug. ⋯ The model was based on the following assumptions: (1) Twitch response is evoked by the binding of acetylcholine (ACh) molecules to the postsynaptic nicotinic receptors in a neuromuscular junction, (2) time-dependent ACh mobilization in a motor nerve terminal results in less ACh output at the fourth stimulus in a train than at the first stimulus, (3) the drugs compete with ACh for the postsynaptic receptors and inhibit the receptor-binding of ACh, and (4) the drugs have various affinities for the receptors. This study suggested that the difference of affinities of the drugs for postsynaptic ACh receptors may cause the difference of TOF fade.
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Journal of anesthesia · Dec 1995
Effects of stellate ganglion block on cardiac coronary circulation.
Since the stellate ganglion contains cardiac sympathetic nerves, stellate ganglion block (SGB) may influence cardiac and coronary hemodynamics. We investigated this influence of SGB by measuring the heart rate (HR), the left circumflex coronary artery blood flow (CBF), the maximum rate of increase of the left ventricular pressure (LV max dP/dt), the cardiac output (CO), the myocardial oxygen consumption (MVO2), and the myocardial oxygen extraction ratio (MOER) in nine dogs before and after performing SGB by means of injection of 2 ml 1% mepivacaine. Left SGB resulted in a decrease of 10% in CBF and a decrease of 15% in LV max dP/dt, but HR, CO, and MVO2 remained unchanged. ⋯ Inhalation of 100% oxygen decreased MOER to the pre-SGB level in either side, thus improving the myocardial oxygen supply-demand relationship. This study suggests the possibility that SGB has deteriorative effects on the myocardial oxygen supply-demand relationship. Those effects were counteracted by the inhalation of 100% oxygen.