Critical reviews in clinical laboratory sciences
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Metabolic alkalosis is the commonest form of acid-base disorder seen in critically ill patients. Although the effects of acidosis have long been known, those of severe metabolic alkalosis are only slowly being recognized. Metabolic alkalosis is itself associated with an increased mortality and a knowledge of the causative factors and treatment options is important. ⋯ Metabolic alkalosis leads to hypoventilation in patients both with and without lung disease, although in the latter, the effect is relatively transient. In patients with chronic obstructive lung disease, however, the development of metabolic alkalosis leads to prolonged hypoventilation and the establishment of a mixed acid-base disorder that may cause difficulty in weaning in the ventilated patient. This is an often forgotten cause of prolonged stay in the intensive care unit with consequent cost and morbidity implications.
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In the last several decades serum levels of cardiac enzymes and isoenzymes have become the final arbiters by which myocardial damage is diagnosed or excluded. Because conventionally used enzymes are neither perfectly sensitive nor specific, there is need for a new sensitive and cardiospecific marker of myocardial damage. Cardiac troponin T (TnT) is a contractile protein unique to cardiac muscle and can be differentiated by immunologic methods from its skeletal-muscle isoform. ⋯ TnT is also useful in monitoring the effectiveness of thrombolytic therapy in myocardial infarction patients. The ratio of peak TnT concentration on day 1 to TnT concentration at day 4 discriminates between patients with successful (greater than 1) and failed (less than or equal to 1) reperfusion. TnT measurements are very sensitive and specific for the early and late diagnosis of myocardial damage and could, therefore, provide a new criterion in laboratory diagnosis of the occurrence of myocardial damage.
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Crit Rev Clin Lab Sci · Jan 1991
ReviewBlood lactate: biochemistry, laboratory methods, and clinical interpretation.
With the renewed awareness of blood lactate as an indicator of circulatory impairment, there has been much interest in the use of lactate measurements to determine the overall state of oxygenation of patients in critical care. This review begins by covering the areas of lactate homeostasis and biochemistry, both of which are essential for fully understanding the interpretation of lactate measurements. ⋯ Both the principles and the latest developments in lactate methodology are covered, including the new whole blood analyzers. This review concludes with reference intervals and guidelines to the interpretation of results.
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Crit Rev Clin Lab Sci · Jan 1989
ReviewThe use of crystalloidal and colloidal solutions for volume replacement in hypovolemic shock.
A wide variety of colloidal and crystalloidal fluids, as well as blood and blood products, are available to the clinician for treatment of the hypovolemic patient. These fluids vary with respect to the size, shape, and concentrations of electrolytes, colloidal molecules, and/or cellular components, duration of volume-expanding effects, incidence of allergic reactions, and effect on the coagulation system. When these fluids are administered intravenously, their distribution in the vascular, interstitial, and cellular compartments can be predicted from fundamental physiological principles as well as from the results of laboratory and clinical research. ⋯ Similar volumes of crystalloidal fluids more rapidly expand the interstitial and intracellular spaces. These principles guide therapy in hypovolemic shock. A logical decision regarding intravenous fluid therapy may be based on the nature of the volume deficit (blood, plasma, or selective protein loss, loss of free water and/or electrolytes) and the predicted changes in cellular and extracellular compartments.
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Crit Rev Clin Lab Sci · Jan 1987
Review Comparative StudySalicylate measurement: clinical usefulness and methodology.
The salicylates are the most commonly used analgesic, antipyretic, and anti-inflammatory drugs. They are available in hundreds of preparations, many of which are over-the-counter medications. The easy access to large quantities of the drug and the widespread perception that the drug is harmless have contributed to salicylate intoxication becoming a serious and common problem, particularly among the pediatric and geriatric populations. ⋯ Recent research on the inhibitory effect of aspirin on platelet aggregation has led to the prophylactic use of aspirin in low doses as an antithrombotic drug. This new therapeutic use of aspirin can be aided by monitoring low serum levels of salicylate and perhaps aspirin itself. This article reviews the current state of the knowledge of the pharmacokinetics and clinical toxicology of salicylate, the clinical usefulness of salicylate measurement by the clinical laboratory, and recent development in the analytical technology for salicylate analysis.