Blood acid-base balance

M.J. Bookallil, pH of the blood acid-base balance, Anaesthetics Royal Prince Alfred Hospital, the University of Sydney, http //www.usyd.edu.au/-su/anaes/-lectures/acidbase mjb/description.html... 

Monitor rate of infusion frequently. Monitor blood acid-base balance. 

The early development of tachypnoea, usually accompanied by hyperpnoea, and resulting in an increased tidal volume, is frequently ascribed to stimulation of the carotid and aortic chemore-ceptors as a result of local accumulation of acid metabolites following cytochrome c oxidase inhibition. However, the general blood acid-base balance changes, notably lactate acidosis, may also be an important factor in breathing changes. 

This electrolyte plays a vital role in the acid-base balance of the body. Bicarbonate may be given IV as sodium bicarbonate (NaHC03) in the treatment of metabolic acidosis, a state of imbalance that may be seen in diseases or situations such as severe shock, diabetic acidosis, severe diarrhea, extracorporeal circulation of blood, severe renal disease, and cardiac arrest. Oral sodium bicarbonate is used as a gastric and urinary alkalinizer. It may be used as a single drug or may be found as one of the ingredients in some antacid preparations. It is also useful in treating severe diarrhea accompanied by bicarbonate loss. 

For Further Reading J. A. Kraut and N. E. Madias, Approach to patients with acid—base disorders, Respiratory Care, vol. 46, no. 4, April 2001, pp. 392—403. J. Squires, Artificial blood, Science, vol. 295, Feb. 8, 2002, pp. 1002-1005. Lynn Taylor and Norman P. Curthoys, Glutamine metabolism Role in Acid-Base Balance, Biochemistry and Molecular Biology Education, vol. 32, no. 5, 2004, pp. 291-304. 

Eliminates waste products from the body regulates blood volume and blood pressure regulates acid-base balance (pH)... 

Chemoreceptor response to increased arterial hydrogen ion concentration. An increase in arterial hydrogen ion concentration, or a decrease in arterial pH, stimulates the peripheral chemoreceptors and enhances ventilation. This response is important in maintaining acid-base balance. For example, under conditions of metabolic acidosis, caused by the accumulation of acids in the blood, the enhanced ventilation eliminates carbon dioxide and thus reduces the concentration of H+ ions in the blood. Metabolic acidosis may occur in patients with uncontrolled diabetes mellitus or when tissues become hypoxic and produce lactic acid. An increase in arterial hydrogen ion concentration has no effect on the central chemoreceptors. Hydrogen ions are unable to cross the blood-brain barrier. 

Hydrogen ion secretion. Hydrogen ions are secreted in the proximal tubule, distal tubule, and collecting duct. The secretion of hydrogen ions is an important mechanism in acid-base balance. The normal pH of the arterial blood is 7.4. When the plasma becomes acidic, H+ ion secretion increases and when it becomes alkalotic, H+-ion secretion is reduced. 

The C02-bicarbonate buffer is a little different from buffers using the usual kind of acids and bases, but it is extremely important in maintaining the acid-base balance of the blood. The acid form of the bicarbonate buffer is actually a gas dissolved in water. Dissolved C02 is turned into an acid by hydration to give H2C03. Hydrated C02 is then much like a carboxylic acid. It gives up a proton to a base and makes bicarbonate, HCO 3. 

Kidney Failure, Chronic An irreversible and usually progressive reduction in renal function in which both kidneys have been damaged by a variety of diseases to the extent that they are unable to adequately remove the metabolic products from the blood and regulate the body s electrolyte composition and acid-base balance. Chronic kidney failure requires hemodialysis or surgery, usually kidney transplantation. [NIH]... 

Excess nitrogen is eliminated from the body in the urine. The kidney adds small quantities of ammonium ion to the urine in part to regulate acid-base balance, but nitrogen is also eliminated in this process. Most excess nitrogen is converted to urea in the liver and goes through the blood to the kidney, where it is eliminated in urine. 

Homeostasis. The blood ensures that a balanced distribution of water is maintained between the vascular system, the cells (intracellular space), and the extracellular space. The acid-base balance is regulated by the blood in combination with the lungs, liver, and kidneys (see p. 288). The regulation of body temperature also depends on the controlled transport of heat by the blood. 

The pH value is kept constant by buffer systems that cushion minor disturbances in the acid-base balance (C). In the longer term, the decisive aspect is maintaining a balanced equilibrium between H" production and uptake and H" release. If the blood s buffering capacity is not suf cient, or if the acid-base balance is not in equilibrium—e.g., in kidney disease or during hypoventilation or hyperventilation-shifts in the plasma pH value can occur. A reduction by more than 0.03 units is known as acidosis, and an increase is called alkalosis. 

Frequently monitor both ethylene glycol levels and acid-base balance, as determined by serum electrolyte (anion gap) or arterial blood gas analysis... 

Fluid balance, acid-base balance, blood pressure, electrolytes... 

The change in the acid-base balance in the body also alters the urine pH, making it more acidic (Fig. 7.59). This alters the excretion dynamics of salicylate, because more salicylate becomes nonionized and so is reabsorbed from the kidney tubules into the blood stream rather than being excreted into the urine. As can be seen from the Figure 7.59, lowering the pH of the urine to 6 results in a dramatic decrease in the ionization of the salicylate. Hence, elimination from the body is reduced. 

Hasselbalch equation, which is important for understanding buffer action and acid-base balance in the blood and tissues of vertebrates. This equation is simply a useful way of restating the expression for the dissociation constant of an acid. For the dissociation of a weak acid HA into H+ and A-, the Henderson-Hasselbalch equation can be derived as follows ... 

Blood chemistry. Pretest, and at least prior to termination, electrolytes and electrolyte balance, acid-base balance, glucose, urea nitrogen, serum lipids, serum proteins (albumin-globulin ratio), enzymes indicative of organ damage such as transaminases and phosphatases should be measured. Toxicant and metabolite levels should be assessed as needed. 

It is not yet clear which estimates of the ratio between the levels of protein and of carbohydrate metabolism during hypoxia should be regarded as reliable. It seems likely that the increase in respiratory quotient in freshwater fish to values of 2.5-2.8, as found by Mohamed and Kutty (1983a, 1986), indicates a predominance of protein expenditure over that of carbohydrate. A hypoxic environment shifts the acid-base balance of the fish towards acidosis (Kotsar, 1976), thereby inducing the redistribution of electrolytes, alteration of ion exchange and the activity of Na+-K+-Mg2+-ATPases and alkaline phosphatases. It also leads to an increased level of C02 in the blood, which enhances the bicarbonate buffer system (Kotsar, 1976). In section 2.1, we... 

The primary functions of the blood may be considered in a broad sense to be the following (1) metabolic regulation—transport of oxygen, carbon dioxide, metabolites, hormones (2) physical and chemical regulation—temperature, acid-base balance, and osmotic pressure and fluid balance and (3) regulation of body defenses—protection against infection by the action of antibodies, leukocytes, and other mechanisms and prevention of hemorrhage. 

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