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A physicochemical model of crystalloid infusion on acid-base status
Edward M Omron1, Rodney M Omron
1Alta Bates Summit Medical Center, Oakland, CA, USA. edofiron@gmail.com
Journal of Intensive Care Medicine
|July 13, 2010
Summary
This study models how crystalloid infusions affect standard base excess (SBE). Infusions with a strong ion difference (SID) greater than 24.5 mEq/L cause metabolic alkalosis, while those with lower SID cause acidosis.
Area of Science:
- Physiology
- Biochemistry
- Medical Simulation
Background:
- Acid-base balance is crucial for physiological function.
- Crystalloid solutions are commonly infused, but their impact on acid-base status requires precise modeling.
- Understanding the effects of different crystalloid compositions on standard base excess (SBE) is clinically relevant.
Purpose of the Study:
- To develop a physicochemical model predicting changes in standard base excess (SBE) after crystalloid infusion.
- To analyze the impact of varying crystalloid strong ion difference (SID) and infusion volumes on acid-base balance.
- To provide a projection of SBE changes per unit volume of common crystalloid solutions.
Main Methods:
- A 70-kg human simulation model was used to assess acid-base and fluid parameters.
- Simulations included sequential infusions of up to 10 L of various crystalloid solutions (normal saline, lactated Ringer's, Plasmalyte 148, NaHCO3 mixtures) with differing SIDs.
- Partial pressure of carbon dioxide (PCO2) was fixed at 40 mm Hg to isolate nonrespiratory acid-base effects.
Main Results:
- A crystalloid SID of 24.5 mEq/L, matching physiological bicarbonate, resulted in neutral acid-base status for up to 10 L infusions.
- Curvilinear relationships were observed between SBE and crystalloid infusion volume for all solutions.
- Crystalloid solutions with SID > 24.5 mEq/L induced metabolic alkalosis, while those with SID < 24.5 mEq/L induced metabolic acidosis.
Conclusions:
- The impact of crystalloid infusion on SBE is determined by the crystalloid's SID, infused volume, and plasma weak acid changes.
- The developed model quantifies the nonrespiratory acid-base effects of crystalloid administration.
- The study presents a predictive tool for clinicians regarding crystalloid-induced acid-base disturbances.
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