Journal of critical care
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Estimation and measurement of serum osmolality can be of value in the clinical management of certain forms of critical illness. Osmolality is a measure of the concentration of osmotically active particles, or solutes, in a solution. Only low-formula weight ions and uncharged molecules that are present in relatively high concentrations contribute significantly to serum osmolality. ⋯ An understanding of serum osmolality, its laboratory measurement, its bedside estimation, and the concept of the osmole gap, is crucial in making a preliminary diagnosis of methanol and ethylene glycol intoxication, as well as a few other related compounds. There are important caveats to this use of the osmole gap, because under certain circumstances both false-positive and false-negative interpretations may occur. The osmole gap may also be helpful for confirming pseudohyponatremia, as a gauge for dosing mannitol and glycerol when used to treat intracranial hypertension, and as a prognostic indicator in circulatory shock.
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Journal of critical care · Sep 1994
ReviewSplanchnic tonometry: a review of physiology, methodology, and clinical applications.
The objective of this article is to review splanchnic tonometry. The English literature, involving both animal and human studies, was used for review, with emphasis on papers on physiological and methodological principles and clinical applications. Tonometry involves the measurement of intraluminal PCO2 as a measure of mucosal PCO2 in the gastrointestinal tract via a catheter in, for instance, stomach or sigmoid colon, and the calculation, with help of the blood bicarbonate content and the Henderson-Hasselbalch equation, of the mucosal pH (pHi). ⋯ Tonometry may be a useful monitoring technique to guide treatment and to improve survival. Splanchnic tonometry is a relatively simple, noninvasive, and thereby promising technique to monitor the critically ill. However, some aspects need further evaluation before the technique can be advocated for routine use.