Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2008
Does patient position influence Doppler signal quality from the USCOM ultrasonic cardiac output monitor?
The USCOM1A continuous wave cardiac output monitor (USCOM Pty Ltd., Sydney, NSW, Australia) is a novel Doppler-based device used to measure cardiac output noninvasively. The proper alignment of the transducer, and hence the ultrasound beam to the aortic or pulmonary outflow tracts, is essential to acquire accurate measurements and often much time is spent on transducer and/or patient positioning. In this prospective, observational, crossover study, we investigated the effect of patient positioning on the acquisition of cardiac output measurement with USCOM1A. ⋯ Our results suggested the sitting position is the least suitable and least reliable position in which to perform cardiac output measurements using USCOM1A compared with the supine, Trendelenburg (20 degrees), left lateral tilt (20 degrees), and right lateral tilt (20 degrees) positions.
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Anesthesia and analgesia · Jun 2008
Comparative Study Clinical TrialBispectral index values during sevoflurane-nitrous oxide general anesthesia in women undergoing cesarean delivery: a comparison between women with and without prior labor.
An end-tidal concentration of 1% sevoflurane (1% ET(SEVO)) in 50% nitrous oxide (N(2)O) during elective cesarean delivery has been associated with bispectral index (BIS) values >60, which are associated with an increased risk of awareness. We hypothesized that BIS values during sevoflurane-N(2)O general anesthesia for cesarean delivery would be lower in women with prior labor compared with women without prior labor. ⋯ Prior labor was associated with lower intraoperative BIS values during sevoflurane/N(2)O general anesthesia and reduced postoperative analgesic consumption in women undergoing cesarean delivery compared with women without prior labor.
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Anesthesia and analgesia · Jun 2008
Hypothermia and acidosis synergistically impair coagulation in human whole blood.
Hypothermia and acidosis were reported to influence coagulopathy in different clinical settings. We evaluated whole blood coagulation to determine the effects of hypothermia and/or acidosis on hemostasis. ⋯ In this in vitro study, hypothermia produced coagulation changes that were worsened by acidosis whereas acidosis without hypothermia has no significant effect on coagulation, as studied by thromboelastometry. This effect was mediated by the inhibition of coagulation factors and platelet function. Thus, thromboelastometry performed at 37 degrees C overestimated integrity of coagulation during hypothermia in particular in combination with acidosis.
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Anesthesia and analgesia · Jun 2008
Comparative StudyThe effect of prolonged anesthesia with isoflurane, propofol, dexmedetomidine, or ketamine on neural cell proliferation in the adult rat.
Recent evidence indicates that new neurons are produced in the adult hippocampus, and play a functional role in cognitive processes such as learning and memory. In animals, new neuron production is suppressed by increasing age, gamma-aminobutyric acid receptor activity, reductions in basal forebrain activity and brain norepinephrine levels, and decreased environmental stimuli. Similarities between these effects and those of anesthetic administration suggest that anesthetics may modulate new cell production, and raise the possibility that postoperative cognitive dysfunction may result, in part, from anesthetic-induced suppression of adult neurogenesis. To test this hypothesis, we investigated the effects of prolonged anesthesia with four different anesthetics on hippocampal cell proliferation in young and older rats. ⋯ Despite using multiple, mechanistically distinct drugs, we found no effect of prolonged anesthesia on adult hippocampal cell proliferation in young rats, a slight suppressive effect of ketamine in older rats, and no circadian effect with isoflurane. These data indicate that anesthetics are unlikely to alter cell proliferation, and by extension that anesthetic-induced inhibition of cell proliferation is unlikely to play a major role in postoperative cognitive impairment. The contrast between our findings, current concepts of anesthetic action, and known modifiers of cell proliferation suggest an incomplete understanding of the pharmacological and behavioral factors governing new neuron production.
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Anesthesia and analgesia · Jun 2008
The effects of aromatic anesthetics on dorsal horn neuronal responses to noxious stimulation.
Gamma-aminobutyric acid type A receptor potentiation and/or N-methyl-d-aspartate (NMDA) receptor inhibition might explain the anesthetic properties of fluorinated aromatic compounds. We hypothesized that depression of dorsal horn neuronal responses to noxious stimulation would correlate with the magnitude of effect of benzene (BNZ), o-difluorobenzene, and hexafluorobenzene (HFB) on NMDA receptors. ⋯ The findings in intact rats suggest that NMDA blockade contributes to the depression of dorsal horn neurons to nociceptive stimulation by fluorinated aromatic anesthetics. These results, combined with the additional findings in decerebrate rats, suggest that supraspinal effects (perhaps on gamma-aminobutyric acid type A receptors) may have a supraspinal facilitatory effect on nociception for HFB.