Chapter 41
- Perioperative Acid-Base Balance
- Patrick J. Neligan
- Clifford S. Deutschman
The chemical composition of the extracellular and intracellular
spaces is tightly controlled to facilitate homeostatic function. This includes,
but is not limited to, hydrogen and hydroxyl ion concentrations. Alterations in
the relative concentrations of these ions are associated with significant clinical
problems. Consequently, the detection, interpretation, and treatment of acid-base
abnormalities have become core elements of clinical care. Traditional educational
approaches to acid-base balance have tended to focus on methods of interpretation
of laboratory data, rather than on understanding the underlying biophysical chemistry.
The field has been confusing for students and clinicians alike, and several commonly
recognized acidbase problems have escaped explanation. The modern physical-chemical
approach to acid-base balance has significantly enhanced our understanding of these
problems and simplified the clinical approach.[1]
[2]
[3]
[4]
Acid-base abnormalities should be seen as resulting from other
biochemical changes in the extracellular environment.[5]
Alterations in the relative concentrations of hydronium (hydrogen) and hydroxyl
ions are less important than the chemical abnormalities causing them. Hydronium
and hydroxyl ions are the dissociation products of water, whose concentrations are
modulated to maintain electrical neutrality depending on the local concentration
of strong ions, weak acids, and carbon dioxide. In this chapter, we explore the
physical chemistry of water, examine the evolution of acid-base medicine, and apply
clinical approaches to acid-base conundrums.
