The Intracellular Milieu


Life, a transient process of creating and maintaining, within discrete boundaries, an ordered environment within an ultimate sea of entropy, is a reflection of complex biochemical interactions.

Proteins, replete with titratible histidine residues, exhibit conformational changes and altered functioning with changes in local proton availability. Cellular function, upon which are built tissues, organs, and organ systems, is possible only within a rather narrow range of concentrations of essential electrolytes such as sodium and potassium.

The kidneys are responsible for maintaining the proper “soup” so that proteins, enzymes, and cellular function can work efficiently to maintain the homeostasis which is life.

The Nephron

Structure & Function

Kimball’s physiology site has a brief summary of renal structure & function.


Renal Pathology Tutorial by J. Charles Jennette, MD of UNC, focusing on the histology of the normal kidney contrasted with that of the kidney with different types of chronic renal failure

Differentiating Categories of Renal Dysfunction

The Diagnosis of Acute Renal Failure by American Family Physician, E-Medicine, Schrier 2004.

Very detailed information is available on – the hypertension, dialysis and clinical nephrology site – requires registration first.

Pre-renal azotemia: differentiation of hyperureagenesis from renal hypoperfusion using urea nitrogen data, an abstract from HDCN (requires registration first)

Water and Electrolyte Homeostasis

Body Fluid Compartments

The ‘Fluid Book’ from AnaesthesiaMCQ is an excellent overview of all aspects of fluid homeostasis. Some basic lecture notes from Pete Smith.Elsevier offers Guyton’s classic chapter.

Several common formulas used in electrolyte calculations are available from ncemi and globalrph.

Body Fluid Composition

See the Fluid Book


This FRCA article summarises common fluid and electrolyte abnormalities.

Perioperative Fluid Therapy

Transfusion for Massive Blood Loss from, an overview of “how to do it,” including potential complications such as hypocalcemia, hyperkalemia, and acid-base disturbances

FFP, Cryo Indications and Risks, from the British Committee for Standards in Haematology.

Electrolyte Disorders


Merck’s Water and Sodium manual.

Hyponatremia after “ecstasy,” an abstract from HDCN (requires registration first). Basically party-goers sweat a lot and only drink plain water. They should drink something with a sodium content similar to sweat (70mM/l).


Potassium metabolism and disorders from the Merck Manual

Bartter’s syndrome – an e-Medicine overview.


Increasing info that hyperchloraemic acidosis isn’t good.


Calcium metabolism from the Merck Manual.

The section on hypercalcemia from the NCI CancerNet Supportive information for physicians site is a very comprehensive, annotated reference including an overview of hypercalcemia associated with malignancies, and discussions of etiologies, manifestations, clinical assessment, and management.


Magnesium from the Merck manual

Mildred S. Seelig, MD, MPH, at the New York Medical College and the American College of Nutrition, provides a comprehensive extravaganza on magnesium effects on cardiovascular physiology, with links.


Phosphate from the Merck manual

Glucose Homeostasis

See my (old) lecture on diabetes, or the Merck Manual. These days very long acting insulins and pumps are much more common.

Oncotic Pressure includes a section on microcirculation, also Chapter 4 of the Fluid Book.


Crystalloid vs. Colloid Solution Therapy

Lots of interest in this area. This editorial summarises the latest view that there is little difference between crystalloids and colloids in ICU, perhaps some subgroups may benefit. The FRCA has notes on this. Older articles from (2000). Starches may be suitable plasma substitutes.

Acid-Base Physiology

Fundamentals of Acids, Bases, and Buffers

Alan ‘Grog’ Grogono has a huge website – – with lots of useful information, diagrams, etc.

Kerry Brandis from Queensland, Australia has provided this concise, clear and thorough explanation of acid-base physiology. Dave Sainsbury from Adelaide has written (in Java) a graphical (java) acid-base interpreter.

Peter A Stewart takes a ‘modern’ approach with his ‘Basic approach to body pH’. Paul Elbers provides Stewart’s 1981 “How to Understand Acid-Base” book in html form on Another substantial review, more traditional and philosophical in nature, is Michael Bookallil’s treatise on Acid-Base – the frames version is best.

The WFSA has a summary of the physiology , Acid-Base and Blood Gas results and Acid-Base in Critical Care.

The Merck Manual has a section on acid-base.

Clinical Consequences of Disordered pH and pCO2

Basic pharmacy info on bicarbonate.

Also notes from QldAnaesthesia.

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