Acid-base physiology

A.W. Grogono, Acid-Base Physiology, http //www.acid-base.com/ physiology.-php (2005). 

H.E. Adrogue and H.J. Adrogue, Acid-base physiology. Respir. Care 46, 328-341 (2001). 

Marquis RE (1995) Oxygen metabolism, oxidative stress and acid-base physiology of dental plaque biofilms. J Ind Microbiol 15, 198-207. 

Manz, Freidrich. History of Nutrition and Acid-Base Physiology. European foumal of Nutrition 40, no. 5 (October 2001) 189-99. 

The special nature of H is discussed below in the section about acid-base physiology. The special functions of calcium, magnesium, phosphates, amino acids, iron, and the trace elements are considered separately in Chapters 20 and 30. 

Alterations of HCOj and CO2 dissolved in plasma are characteristic of acid-base imbalance. Its value has most significance in the context of other electrolyte values and with blood gases and pH values. The full clinical significance of the determination of total CO2 wiU become apparent in the following discussion of acid-base physiology. 

Jones, N. L. Blood Gases and Acid-Base Physiology, Marcel Decker, New York 1980... 

F. Manz F (2001) History of nutrition and acid-base physiology. Eur. JNutr., 40, 189-199. 

In acid-base physiology, one is concerned with the concentration of hydrogen ions (HsO ) in the bulk phase. The Henderson-Hasselbalch equation of the form given below is of interest ... 

Acid-base physiology is about the concentration of hydrogen ions in the body fluids. This first chapter is a summary of the physico-chemical background to the subject. 

This is the Henderson-Hasselbalch equation it plays a prominent role in acid-base physiology. 

As the subject of acid-base physiology is developed, it will become apparent that carbon dioxide and bicarbonate play a crucial role. Carbon dioxide is not itself an acid but in aqueous solution it reacts with water to yield hydrogen ions (Table 1.4 reaction 1) and such a chemical is an acid. It also yields bicarbonate and this is the corresponding (conjugate) base. The C02-bicarbonate system is thus a buffer pair in which we will refer, rather loosely, to CO2 as the buffer acid and bicarbonate as the buffer base. Typical values for the concentrations in arterial blood are [CO2] = 1.2 m M and [HCO3 ] = 24 m M. 

As will be explained later, the respiratory system contributes more than mere maintenance of a constant [CO2]. When the pH is low as in the present examine, hyperventilation contributes to the physiological response by changing the PCO2 to a subnormal value, this lowers [CO2] and thereby raises the pH to above 7.1. Such is the efliciency of the body in its response to disorders of acid-base physiology. 

Not only is the concentration of carbon dioxide under physiological control, so also is the concentration of the other component of the buffer pair, the bicarbonate. This is controlled in the kidney, which may increase or decrease the excretion of bicarbonate as components of physiological control mechanisms. Since both components of the buffer pair are under physiological control, it is possible for the C02-bicarbonate system to act as a perfect buffer and completely to restore the pH of the internal environment to normal. Examples of such contributions will appear repeatedly as the subject of acid-base physiology unfolds. 

The pH values of arterial plasma measured for all the individuals in a crowd of normal healthy people would fall mostly in the range 7.35 to 7.45, with an average of 7.4 (Robinson, 1962, p. 3). The plasma pH values measured on patients admitted to the metabolic ward of a hospital and suffering from untreated disorders of acid-base physiology would probably range between 7.1 and 7.7, this being the range compatible with life. For short periods of time, it is possible for the pH to go even further from normal particularly on the acid side, but these are useful limits to remember and are shown in Table 2.1. 

Range in disorders of acid-base physiology compatible with life ... 

Bicarbonate and carbon dioxide are two chemicals of great importance in acid-base physiology and they too can deviate in concentration widely from normal before the change becomes life-threatening. 

The reversible reaction of carbon dioxide with water to yield hydrogen ions and bicarbonate ions is fundamental in acid- base physiology. 

The first relationship to be considered is that between PCO2 and bicarbonate concentration for water. Then fluids are considered which contain plasma constituents important in acid-base physiology. 

Chapters 1 and 2 have provided the necessary background to consider disturbances of acid-base physiology and the body s responses, which forms the subject matter of this chapter. 

The renal mechanisms come into play immediately the disturbance of acid-base physiology starts. However, it takes a relatively long period for the renal mechanisms to come to maximum efficiency and for the renal retention of bicarbonate to build up the concentration throughout the body. In respiratory acidosis, it takes around three days for the subject to settle to the compensated point. This is where the subject then stays so long as the same degree of hypoventilation persists. 

Disorders of acid-base physiology which are not of respiratory origin are called metabolic disorders. This nomenclature derives from the fact that such disorders result from abnormal metabolism. Metabolic disorders of metabolism may also be due to excessive intake of acid or alkali or to failure of renal function, when the tubular mechanisms for formation of acid or alkaline urine are impaired. 

Respiratory disorders of acid-base physiology have the common feature that the primary abnormality is a deviation from normal of the amount of carbon dioxide in the body. Metabolic disorders are caused by a large variety of primary abnormalities resulting from an excess of non-respiratory acid or alkali in the body. It is useful to classify the causes thus ... 

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