Critical care clinics
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In the quest for a better monitor of end-organ injury in the critically ill patient, gastrointestinal tonometry to measure intramucosal pH (pHi) and PCO2 has been advocated by several investigators. The authors discuss the principles and practice of gastric tonometry. ⋯ Although prognostic capability is an important role for tonometry, the principal benefit of the technology is its efficacy as an index of tissue resuscitation and as a guide to medical intervention. Given recent technical advances, gastrointestinal tonometry may gain increasing use in the assessment of tissue perfusion and oxygen metabolism.
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Current monitoring of critically ill patients uses measurement of global parameters such as oxygen consumption and lactate levels. With development of new monitoring technologies, it may be possible to monitor patients on an organ or tissue level, allowing manipulation of specific organ or tissue perfusion. Potentially useful techniques for monitoring tissue energetics in the future include NIR and NMR spectroscopy. ⋯ Both of these techniques may be useful for identification of dysoxia or oxygen-limited mitochondrial turnover. Experimental evidence suggests that organs in the septic state are more sensitive to dysoxia. Implications for the care of the patient with sepsis include possible decreased tolerance to factors leading to dysoxia, such as hypoxemia, hemodilution, or ischemia.
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Critical care clinics · Oct 1996
ReviewDetermination of oxygen delivery and consumption versus cardiac index and oxygen extraction ratio.
Measuring cardiac output without knowledge of the oxygen extraction by the tissues is of limited value. Instead of calculating oxygen consumption and oxygen delivery, a diagram relating cardiac index to the oxygen extraction ratio is proposed to interpret hemodynamic data at the bedside. This diagram is particularly helpful in interpreting cardiac index in the presence of changes in hemoglobin or oxygen demands and in evaluating the effects of therapy.
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Critical care clinics · Oct 1996
ReviewHemodynamics and positive end-expiratory pressure in critically ill patients.
This article examines the factors that affect the transmission of airway pressures to intrathoracic structures. The effects of positive end-expiratory pressure on central venous pressures, cardiac filling pressures, and right and left ventricular function are discussed. Various techniques for estimating intrathoracic pressures and their limitations are reviewed.
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Arterial blood gas (ABG) measurements are one of the most frequently requested laboratory examinations in critically ill patients. ABGs include measurement of pHa, PaCO2, PaO2, and oxyhemoglobin saturation. These measurements allow for assessment of the nature, progression, and severity of metabolic and respiratory disturbances.