Journal of critical care
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Journal of critical care · Dec 1993
Comparative StudyImportance of tonicity of carbicarb on the functional and metabolic responses of the acidotic isolated heart.
In this study, the physiological and metabolic effects of Carbicarb administered as an isotonic (150 mmol/L Na[n[]I+) or hypertonic (1 mol/L Na[n[]I+) solution over 2 minutes in the acidotic isolated heart were compared. Physiological monitoring as well as 31P and 23Na nuclear magnetic resonance spectroscopy were performed. Both isotonic and hypertonic Carbicarb induced comparable dose-dependent increases in intracellular pH as well as decreases in inorganic phosphate and increases in creatine phosphate concentrations, which were sustained for 20 minutes. ⋯ In this setting, hypertonic Carbicarb induced a large transient increase in cytosolic sodium, whereas isotonic Carbicarb caused immediate and sustained decreases in cytosolic sodium. These data suggest that isotonic Carbicarb may have more beneficial effects on cardiac function than hypertonic Carbicarb. These effects may be related to associated changes in cytosolic sodium.
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Journal of critical care · Dec 1993
What good are we doing? The role of clinical research in enhancing critical care medicine.
The amount of financial and other resources used by physicians in the treatment of critically ill patients makes it incumbent upon physicians to ensure that sufficient benefit is obtained from these resources and that physicians are in fact doing good for their patients. Knowing that one is in fact doing good requires an understanding of what counts as benefit. Current medical practice suggests that patient benefit is typically understood in terms of physiological changes and responses, highlighting the role of medical subspecialties in patient care. ⋯ This broader understanding calls for an ambitious research agenda so that physicians will be able to learn how they can genuinely help critically ill patients and their families during times of illness. Carrying out such an agenda requires overcoming the ethical challenges of performing research on patients as vulnerable as critically ill patients. It also requires physicians to establish collaborative ties with other professionals so that truly interdisciplinary research can be performed on a routine basis.
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Journal of critical care · Dec 1993
Absence of supply dependence of oxygen consumption in patients with septic shock.
We tested whether oxygen consumption (VO2) was dependent on oxygen delivery (QO2) in 10 patients with septic shock when QO2 was changed by the use of the inotropic agent, dobutamine. The mean acute physiology and chronic health evaluation (APACHE) II score of the patients was 27.3 +/- 8.1 with a mean blood pressure on entry of 66.8 +/- 12.4 mm Hg, and all had been volume resuscitated to a pulmonary artery occlusion pressure of greater than 10 mm Hg. We measured VO2 by analysis of respiratory gases (VO2G) while calculating VO2 by the Fick equation (VO2F) at three different O2 deliveries. ⋯ Neither lactic acidosis nor acute respiratory distress syndrome (ARDS) conferred supply dependence of VO2G, but the presence of ARDS was predictive of death in this cohort. It is concluded that VO2 is independent of QO2 in patients with septic shock and lactic acidosis. These data confirm that maximizing QO2 beyond values achieved by initial fluid and vasoactive drug resuscitation of septic shock does not improve tissue oxygenation as determined by respiratory gas measurement of VO2.
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Journal of critical care · Dec 1993
A physical chemical approach to the analysis of acid-base balance in the clinical setting.
We evaluated the clinical application of a model of acid-base balance, which is based on quantitative physical chemical principles (Stewart model). This model postulates that acid-base balance is normally determined by the difference in concentration between strong cations and anions (strong ion difference [SID]), PCO2, and weak acids (primarily proteins). We measured electrolytes and blood gases in arterial blood samples from 21 patients in a medical or surgical intensive care unit or emergency room of a tertiary care hospital. ⋯ It could also be calculated from the difference between the standard Siggaard-Anderson calculation of base excess and base excess attributable to free water, [Cl-], and proteins (ie, base-excess gap). Our results indicate that the SID gap, base excess gap, and anion gap reflect the presence of unmeasured ions, and both the anion-gap and base-excess gap provide readily available estimates of the SID gap. This provides a simple bedside approach for using the Stewart model to analyze the nonrespiratory component of clinical acid-base disorders and indicates that, in addition to unmeasured anions, unmeasured cations can be present.
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Journal of critical care · Dec 1993
Comparative StudyThe relationship between the arteriovenous carbon dioxide gradient and cardiac index.
It has been reported that under normal conditions, mixed venous blood gases have approximated arterial samples; however, during cardiac arrest or severe cardiogenic shock, marked differences between arterial and venous blood gases have been noted. To further assess the relationships between arterial and mixed venous blood gases and cardiac index, a study population was chosen consisting of patients with less severe states of cardiac impairment. The differences between arterial and mixed venous PCO2s and pHs were compared with cardiac indexes (CI) of 44 patients in an intensive care unit with arterial lines and Swan-Ganz catheters in place. ⋯ When the CIs of all patients were plotted against the delta PCO2s, there was an inverse linear relationship wherein delta PCO2 increased as CI decreased (r = -.47, P = .0011). There is an inverse relationship between delta PCO2 and CI that has not been previously described. An elevated delta PCO2 may be a marker of a low cardiac index.