Critical care medicine
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Critical care medicine · Jan 1996
Comparative StudyOxygen consumption calculated from the Fick equation has limited utility.
To determine if oxygen consumption (VO2) calculated using the Fick relationship (calculated VO2) determines total body VO2 accurately and precisely enough to employ this method during clinical assessment of oxygen transport. ⋯ Even in a tightly controlled, clinical simulation in the laboratory, calculated VO2 from the Fick relationship systematically underestimated VO2 measured with a water-sealed spirometer. If true VO2 changes, the magnitude and direction of change will be reflected by calculated VO2 but with approximately 20% error in the absolute value. Heart failure, acute lung injury, and their combination did not affect the accuracy of calculated VO2. Therefore, calculating VO2 using the Fick relationship is too inaccurate to be used for research purposes. Because assessment of the directional change of VO2 may be clinically useful, calculated VO2 can be employed with discretion during clinical oxygen transport evaluation, bearing in mind the calculation's inherent imprecision.
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Critical care medicine · Jan 1996
Hypertonic saline does not improve cerebral oxygen delivery after head injury and mild hemorrhage in cats.
To investigate the effects of hypertonic saline for resuscitation after mild hemorrhagic hypotension combined with fluid-percussion traumatic brain injury. Specifically, the effects of hypertonic saline on intracranial pressure, cerebral blood flow (radioactive microsphere method), cerebral oxygen delivery (cerebral oxygen delivery = cerebral blood flow x arterial oxygen content), and electroencephalographic activity were studied. ⋯ After a combination of hemorrhage and traumatic brain injury, neither 10% hydroxyethyl starch nor 3.0% hypertonic saline restored cerebral oxygen delivery. Although neither trauma alone nor hemorrhage alone altered electroencephalographic activity, the combination produced significant decreases in electroencephalographic activity at 60 and 120 mins after resuscitation in groups 3 and 4, suggesting that cerebral oxygen delivery is inadequately restored by either resuscitation fluid. Therefore, traumatic brain injury abolished compensatory cerebral blood flow increases to hemodilution, and neither hydroxyethyl starch nor 3.0% hypertonic saline restored cerebral blood flow, cerebral oxygen delivery, or electroencephalographic activity after hemorrhagic hypotension after traumatic brain injury.
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Critical care medicine · Jan 1996
Editorial CommentLiquid breathing: stretching the technological envelope.