Acid-base homeostasis

Cameron, J.N. (1989). Acid-base homeostasis past and present perspectives. Physiol. Zool. 62 845-865. 

The kidney plays a major role in the maintenance of acid-base homeostasis, particiilarly with respect to metabolic acidosis. In response to metabolic acidosis, the kidney is able to increase its production of ammonia resulting in enhanced urinary ammonium excretion, a process linked to proton excretion and the generation of... 

Hansinger, D. Organization of hepatic nitrogen metabolism and its relation to acid-base homeostasis. Khn. Wschr. 1990 68 1096-1101... 

Cohen R D, Woods H F 1996 Disturbances of acid-base homeostasis. In Weatherall D J, Ledingham J G G, Warrell D A (eds) Oxford textbook of medicine, 3rd edn. Oxford University Press, Oxford, pp. 1533-1544 Collatos C 1997 Blood and blood component therapy. In Robinson N E (ed) Current therapy in equine medicine, 4th edn. Saunders, Philadelphia, PA, pp. 290-292 Conhaim R L, Watson K E, Potenza B M et al 1999... 

The kidney plays a central role in the maintenance of acid-base homeostasis through reclamation of filtered bicarbonate and secretion of ammonium and acid. The tubular mechanisms underlying these processes are discussed in Chapter 46. 

The chloride (CD) ion is the most abundant anion in the ECF (see Table 46-2), In the absence of acid-base disturbances, Cr concentrations in plasma will generally follow those of Na. However, determination of plasma CD concentration is useful in the differential diagnoses of acid-base disturbances and is essential for calculating the anion gap (see Increased Anion Gap Acidosis [Organic Acidosis] section later in this chapter). Fluctuations in serum or plasma Cl have little clinical consequence, but do serve as signs of an underlying disturbance in fluid and acid-base homeostasis and can be an aid in differentiating the cause of these disturbances. 

Under normal conditions each of the two million nephrons of the kidney work in an organized approach to filter, reabsorb, and excrete various solutes and water. The kidney is a primary regulator of sodium and water as well as acid-base homeostasis. The kidney also produces hormones necessary for red blood cell synthesis and calcium homeostasis. Impairment of normal kidney function is often referred to as renal insufficiency. Based on the time course of development, renal insufficiency has historically been divided into two broad categories. Acute renal failure (ARF) refers to the rapid loss of renal function over days to weeks. Chronic kidney disease (CKD)", also called chronic renal insufficiency (CRI) by some, is defined as a progressive loss of function occurring over several months to years, and is characterized by the gradual replacement of normal kidney architecture with interstitial fibrosis. Progressive kidney disease or nephropathy is... 

Acid-base disorders are common, and often serious, disturbances that may result in significant morbidity and mortality. This chapter reviews the mechanisms responsible for the maintenance of acid-base balance and the laboratory analyses that aid clinicians in their assessment of acid-base disorders. The pathophysiology of the four primary acid-base disturbances is presented, the therapeutic options are critiqued, and guidelines for the achievement of the desired therapeutic outcomes are presented. Because many drugs affect acid-base homeostasis and many acid-base abnormalities are potentially preventable, clinicians must anticipate drug-related problems in order to avoid or minimize the clinical consequences, and when necessary design appropriate treatment regimens. 

Digestion of dietary substances and tissue metabolism also results in the production of nonvolatile acids. These acids are derived primarily from the sulfur-containing amino acids cysteine and methionine, as well as from ingested sulfur. In addition, phosphates are generated from the metabolism of proteins and phospholipids. Neutral substances such as glucose may also be incompletely metabolized to intermediates, such as lactic and pyruvic acid, and fatty acids may be incompletely metabolized to acetoacetic acid and / -hydroxybutyric acid. These dietary and metabolic fixed acids are excreted, primarily by the kidney, to maintain acid-base homeostasis. On average, daily fixed acid excretion is approximately 0.8 mEq/kg per day. ... 

Excretion of metabolic fixed acids and generation of new HCO3 is achieved through renal ammoniagenesis and distal tubular hydrogen ion secretion. Ammoniagenesis plays a critical role in acid-base homeostasis, with ammonium (NH4+) excretion comprising approxi-... 

Mineralocorticoid excess also plays a significant role in the maintenance of metabolic alkalosis. In patients with volume-responsive metabolic alkalosis, intravascular volume depletion stimulates aldosterone secretion. As discussed earlier, excess mineralocorticoid activity may also underlie the generation of metabolic alkalosis. In either situation, the increased mineralocorticoid effect stimulates collecting duct H+ secretion. Metabolic alkalosis may also be maintained by persistent hypokalemia. Hypokalemia has a multitude of effects on renal acid-base homeostasis, enhancing proximal tubular bicarbonate reabsorption, stimulating ammoniagenesis and increasing distal tubular H secretion. ... 

When considering the mechanism by which drug causes nephrotoxicity, two components of renal function are decisive. The first are the renal transport processes which are critical to recovering essential minerals and nutrients from the glomerular filtrate and the second are the renal enzyme systems which are essential to both detoxification of xenobiotics and maintaining the bod)/ s acid/base homeostasis [22, 23]. 

Collectively, plasma proteins perform a nutritive function they exert colloidal osmotic pressure and aid in the maintenance of acid-base homeostasis. Individual proteins serve as enzymes, antibodies, coagulation factors, and hormones and in the transport of other molecules. The enzymatic roles of proteins are discussed in other chapters (see Chapter 2). On the basis of their metabolic roles, proteins can also be divided into several broad categories several have more than one function. These categories are acute phase (reactant) proteins, immunoproteins, complement... 

By far the greatest production of chemical which threatens acid-base homeostasis is that of carbon dioxide in metabolism. Quantitatively, this amounts to 25 Moles of acid per day. This acid is blown off by the lungs (Table 5.1). 

Define titratable acid and total acid indicate how they are measured. Describe in outline the effects on acid-base homeostasis of a) renal failure and b) diuretic therapy. 

Carbonic acid equilibria are important for acid-base homeostasis in the human body. 

An important component of acid-base homeostasis. It exists in equilibrium with carbonic acid and carbon dioxide as follows ... 

The concentration of CO2 in blood is usually represented as FCO2, the partial pressure of CO2. Bicarbonate concentration can be regarded as the metabolic component of acid-base homeostasis while CO2 can be regarded as the respiratory component. Thus a primary change in one of these components as a result of a clinical condition can result in a compensatory change in other component. Raised blood PCO2 occurs in respiratory acidosis (as in chronic obstructive airway disease] and compensated metabolic alkalosis. Low blood PCO2 is found in respiratory alkalosis (hyperventilation) and in compensated metabolic acidosis. 

A red cell protein comprised of four protein subunits (globin) each of which consists of a polypeptide chain linked to haem. In normal haemoglobin there are two a chainsand twoj chains. Itis involved in the transport of oxygen in blood and also functions in acid-base homeostasis. 

Glycolytic contribution to tissue acid-base homeostasis... 

There are three major tubular functions to be recognised (1) salt and water balance, (2) potassium and acid/base homeostasis, and (3) calcium and phosphorus balance. 

The determination of arterial blood gases is very important to monitor the gas exchange in critically ill patients. It provides valuable information about the patient s metabolism, gas exchange, ventilation, and acid-base homeostasis [2]. A reliable way for blood gas determination is the direct analysis of an arterial blood sample by point-of-care blood gas analyzers with implemented Clark and Severinghaus sensors to measure p02 and PCO2, respectively [3]. 

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