Journal of anesthesia
-
Journal of anesthesia · Jun 1994
Effects of biogenic amines and intravenous anesthetics on the activity of rat locus coeruleus neurons in vitro.
To examine the effects of biogenic amines and clinically relevant concentrations of intravenous anesthetics on neuronal activities, the authors analyzed both spontaneous and evoked activities of neurons in the nucleus locus coeruleus (LC)in vitro using a single unit recording technique. Spontaneous firing was observed in 37% (14/38) of LC neurons, andN-methyl-D-aspartate (NMDA, 50 μM), glutamate (250 μM), and carbachol (1-2 mM) elicited firing in 100% (38/38), 63% (12/19), and 58% (7/12) of silent LC neurons respectively. Noradrenaline (50 μM) and serotonin (5-HT) (1-5 μM) suppressed spontaneous and drug-induced activities in 47% (15/32) and 23% (8/35) of LC neurons, respectively. ⋯ All neurons activated by NMDA (n=8) and glutamate (n-3) were suppressed by ketamine (40 μM), but fentanyl (1 μM) only suppressed 60% (3/5) of spontaneously active and 75% (3/4) of glutamate-activated neurons. Identical LC neurons were inhibited by various combinations of noradrenaline, 5-HT, pentobarbital, ketamine, and fentanyl. The results suggest that clinically relevant concentrations of anesthetics and opioids modulate the activity of LC neurons induced by biogenic amines, excitatory amino acids, and acetylcholine.
-
Journal of anesthesia · Jun 1994
An analysis of CO2 elimination curves during artificial ventilation.
We have developed some indices to evaluate the phase III slope in CO2 elimination curves. The indices were applied to 12 mechanically ventilated patients in ICU to determine their stability under various ventilator settings. Fco2-sl[30-90] and[Formula: see text] expressed the mean incline of phase III slope in Fco2-volume curves and[Formula: see text]-volume curves, respectively. ⋯ In the first study, Fco2-sl[30-90] and[Formula: see text][30-90] correlated with ETco2, Vd/Vt and the volume of CO2 expired, but Fco2-SR and[Formula: see text]-SR were independent of these parameters.[Formula: see text]-SR did not show any significant changes under various ventilator settings except for application of PEEP. In the second study, those with impaired preoperative respiratory function had significantly larger values for[Formula: see text].[Formula: see text] was as sensitive as parameters such as VD/VT, arterial to end-tidal CO2 tension difference (a-ET·Dco2), and volume pressure index (VPI) in prediting poor respiratory functions. We concluded that[Formula: see text] is a useful index for evaluating the phase III slope in CO2 elimination curves.