Journal of applied physiology
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Clinical Trial
The respiratory change in preejection period: a new method to predict fluid responsiveness.
The accuracy and clinical utility of preload indexes as bedside indicators of fluid responsiveness in patients after cardiac surgery is controversial. This study evaluates whether respiratory changes (Delta) in the preejection period (PEP; DeltaPEP) predict fluid responsiveness in mechanically ventilated patients. Sixteen postcoronary artery bypass surgery patients, deeply sedated under mechanical ventilation, were enrolled. ⋯ Right atrial pressure and pulmonary arterial occlusion pressure before volume expansion did not correlate with the change in stroke volume index after the fluid challenge. Systolic pressure variation, DeltaPEP, Deltadown, and change in pulse pressure before volume expansion correlated with stroke volume index change after fluid challenge (r2 = 0.52, 0.57, 0.68, and 0.83, respectively). In deeply sedated, mechanically ventilated patients after cardiac surgery, DeltaPEP, a new method, can be used to predict fluid responsiveness and hemodynamic response to PEEP10.
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We investigated the effect of head-down bed rest (HDBR) for 14 days on thermoregulatory sweating and cutaneous vasodilation in humans. Fluid intake was ad libitum during HDBR. We induced whole body heating by increasing skin temperature for 1 h with a water-perfused blanket through which hot water (42 degrees C) was circulated. ⋯ The increase in the threshold temperature for sweating correlated with that for cutaneous vasodilation. In conclusion, HDBR attenuated thermoregulatory sweating and cutaneous vasodilation by increasing the threshold temperature and decreasing sensitivity. HDBR increased the threshold temperature for sweating and cutaneous vasodilation by similar magnitudes, whereas it decreased their sensitivity by different magnitudes.
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Mutations in the skeletal muscle RyR1 isoform of the ryanodine receptor (RyR) Ca2+-release channel confer susceptibility to malignant hyperthermia, which may be triggered by inhalational anesthetics such as halothane. Using immunoblotting, we show here that the ryanodine receptor, calmodulin, junctin, calsequestrin, sarcalumenin, calreticulin, annexin-VI, sarco(endo)plasmic reticulum Ca2+-ATPase, and the dihydropyridine receptor exhibit no major changes in their expression level between normal human skeletal muscle and biopsies from individuals susceptible to malignant hyperthermia. In contrast, protein gel-shift studies with halothane-treated sarcoplasmic reticulum vesicles from normal and susceptible specimens showed a clear difference. ⋯ In the concentration range of 0.014-0.35 mM halothane, anesthetic-induced oligomerization of the RyR1 complex was observed at a lower threshold concentration in the sarcoplasmic reticulum from patients with malignant hyperthermia. Thus the previously described decreased Ca2+-loading ability of the sarcoplasmic reticulum from susceptible muscle fibers is probably not due to a modified expression of Ca2+-handling elements, but more likely a feature of altered quaternary receptor structure or modified functional dynamics within the Ca2+-regulatory apparatus. Possibly increased RyR1 complex formation, in conjunction with decreased Ca2+ uptake, is of central importance to the development of a metabolic crisis in malignant hyperthermia.