Critical care medicine
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Critical care medicine · Aug 1987
Comparative StudyComparison of noninvasive measurements of carbon dioxide tension during withdrawal from mechanical ventilation.
End tidal CO2 tension (PetCO2) and transcutaneous CO2 tension (PtcCO2) were compared with arterial CO2 (PaCO2) before and after withdrawal of mechanical ventilation in 20 patients predisposed to hypercarbia. With stable PaCO2 during mechanical ventilation, the correlation coefficient (r) between PaCO2 and PetCO2 was .9, and between PaCO2 and PtcCO2, .87. PtcCO2 considerably overestimated PaCO2 in three patients who were receiving dopamine. ⋯ In eight of these, PetCO2 and PtcCO2 rose by at least 5 torr, and in seven, the rise in PetCO2 and PtcCO2 was within 5 torr of the rise in PaCO2. During mechanical ventilation, PetCO2 and PtcCO2 estimated stable PaCO2 with sufficient accuracy for clinical use, except in patients with cutaneous vasoconstriction. After withdrawal of mechanical ventilation, changes in PetCO2 and PtcCO2 were predictive of important PaCO2 increases, warranting continued exploration and evaluation as to their use in monitoring patients predisposed to hypercarbia.
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Traditional concepts of shock therapy have been based on conventional monitoring. However, the availability of invasive monitoring systems has provided the means to describe the patterns of oxygen transport in various acute life-threatening illnesses. Surgical trauma provides a useful model for investigation of other shock syndromes, because measurements may be made in the preoperative control period, during the hemodynamic crisis intraoperatively, and sequentially throughout the postoperative period for survivors and nonsurvivors. ⋯ The interactions of survivors' hemodynamic and oxygen transport patterns define compensatory responses which primarily are increased cardiac output, DO2, and VO2. Inadequate compensations and decompensations of shock are clearly manifest by the nonsurvivor pattern. Therapeutic goals may be defined by the values of the survivor patterns; reduced mortality and morbidity result when these goals are vigorously applied prospectively (17-19).
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Cutaneous blood flow may be an indirect measure of circulatory function estimated by continuous, noninvasive laser Doppler velocimetry (LDV). It has been postulated that LDV may be a useful monitor of cardiac output changes. To test this hypothesis, LDV was evaluated in 67 critically ill adult patients with simultaneous measurements of cardiac index (CI) and other physiologic variables. ⋯ Further, with the heated laser probe, the magnitude of acute CI change is reflected. However, there are gradual changes over time of LDV which may occur independently of CI or other monitored variables. Hence, absolute LDV values are not predictive of absolute CI values.
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Critical care medicine · Aug 1987
Comparative StudyEvaporation versus iced gastric lavage treatment of heatstroke: comparative efficacy in a canine model.
We compared the speed of cooling and treatment efficacy for evaporative cooling vs. iced gastric lavage in a canine heatstroke model. Nine random-source, mongrel dogs were anesthetized, shaved, and internally heated until the core temperature reached 43.0 degrees C. The animals were then randomly assigned to be cooled to 37 degrees C either by iced (1 degree C) tap water gastric lavage (n = 5200 ml/min) through a large (32-Fr) orogastric tube, or by spraying with tap water (n = 4, 15 degrees C, 12 L/min) before a large fan blowing room temperature air (23 degrees C) across the dog at 0.5 m/sec from a height of 50 cm. ⋯ Moreover, all animals treated with evaporation survived and were neurologically intact 48 h later, while only one lavage-treated dog was neurologically intact over the same period. The others in the lavage group died one hour after cooling (n = 1), were grossly ataxic (n = 1), or were persistently comatose (n = 2). A simple evaporative cooling technique, readily available in the emergency department, appears to be the most rapid and effective means for cooling and treating heatstroke in the dog.