Acid-base balance disturbances

The respiratory effects of salicylates contribute to the serious acid—base balance disturbances that characterize poisoning. Salicylates stimulate respiration directly and indirectly. Uncoupling of oxidative phosphorylation leads to increased peripheral CO2 production and a compensatory increase in minute ventilation, usually with no overall change in PCO2. Uncoupling of oxidative phosphorylation also leads to excessive heat production, and salicylate toxicity is associated with hyperthermia, particularly in children. 

Effects of repeated ethylene glycol peroral overexposure in treated rats and mice can result in kidney, Hver, and nervous system damage. The most sensitive indicators of ethylene glycol toxicity are disturbances in acid—base balance and nephrotoxic (kidney) effects. Effects of repeated chronic peroral overexposure of diethylene glycol in treated rats result in kidney and Hver damage (48). 

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. 

Over dose/acute salicylate poisoning is characterized by salicylism which consists of tinnitus, vertigo and deafness, hyperthermia, toxic encephalopathy (agitation, confusion and convulsions followed by coma), dehydration (due to hyperpyrexia, sweating and vomiting), disturbances of acid base balance and petechial haemorrhages. 

In oxidation-reduction reactions, electron transfers (e ) are coupled with the transfer of protons (H ) to maintain a charge balance. A modification of the redox balance corresponds to a modification of the acid-base balance. The net reactions of the oxidation of C, S, and N exceed reduction reactions in these elemental cycles. A net production of ions in atmospheric precipitation is a necessary consequence. The disturbance is transferred to the terrestrial and aquatic environments, and it can impair terrestrial and aquatic ecosystems. 

Many pathological conditions are accompanied by disturbances of the acid-base balance and electrolyte composition of the blood. These changes are usually reflected in the acid-base pattern and anion-cation composition of ECF, as measured in blood. However, results obtained on blood or plasma may not always reflect the acid-base status of the ICF. 

Within the liver, elimination of ammonia occurs via urea synthesis (Chapter 17). Since urea is uncharged, it does not disturb the acid-base balance. Many interorgan relationships in protein and nitrogen homeostasis arose because of the role that the liver plays in excess nitrogen excretion. 

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. 

Phenacetin has analgesic and antipyretic but no antiinflammatory properties. Phenacetin and its deethylated metabolite, acetaminophen, are superior to aspirin in that they do not cause hypoprothrombinemia, GI irritation, or disturbances of acid-base balance. The serious, but rare, side effects of phenacetin are methemoglobinemia, hemolytic anemia, fatal hepatic necrosis, and hypoglycemic coma. Both interstitial nephritis and renal papillary necrosis can be caused by phenacetin and acetaminophen. The less toxic acetaminophen should be used only in patients who cannot tolerate aspirin or in whom aspirin is contraindicated (see also Table 3). 

Alkalosis Condition in which the pH of the blood is alkaline, >7.8 caused by a disturbance in the acid-base balance. 

Ascorbate and Oxidation-Reduction Potential. The ascorbic acld-dehydroascorbic acid system is believed to play an important part in maintaining optimum oxidation-reduction conditions in the tissues. The oxidation-reduction potential, like acid-base balance and pH, must be balanced within fairly narrow limits for normal health. Any disturbance of oxidation-reduction potential, such as would result from depletion of ascorbate reserves in cancer, could have deleterious systemic effects (3). 

This rise in blood lactate after infusions of fructose in low concentrations (0.5g. per Kg. body weight per hour) is large enough to disturb the acid-base balance in clinical settings associated with acid-base disturbances. Fructose is rapidly phosphorylated in the liver and leads to a sharp fall in liver ATP concentrations (Woods and Alberti, 1972 Maenpaa et al.,... 

Intravenous feeding involves many problems, some of which remain to be solved. The basic problem is the compounding of utilizable nutrients which can be dispersed in a suitable medium and administered without greatly disturbing the fluid distribution, acid-base balance, or metabolic status of the body. Because a major need in intravenous feeding is the provision of suitable energy-yielding food, carbohydrates are important. 

In spite of the variety and efficiency of the body s mechanisms for maintaining a constant pH, disturbances of acid-base balance can and do occur. They may result from gross dietary imbalance, and also from respiratory, metabolic or renal disorders in which there is either too great a production or a failure of elimination of acid or base. 

Diuretic therapy is a common iatrogenic origin of metabolic disturbances of acid-base physiology. Diuretics are administered for their naturetic properties particularly in patients with cardiac, hepatic, pulmonary and renal disease, to rid the body of excess extracellular fluid. When the loss of sodium is matched by losses of other extracellular electrolytes in proportion to their extracellular concentrations, no disturbance of acid-base balance occurs. In cases where there is a disproportionate loss of bicarbonate, the result is metabolic acidosis. Conversely when there is an exaggeration of loss of ammonium or chloride ions by comparison with sodium, this leads to metabolic alkalosis. 

B. Disturbances of acid-base balance and of fluid volume interactions... 

Persistent vomiting of gastric contents. There is a loss of HCl, NaCl, water. Hence the kidney is called upon to retain sodium and chloride and to restore fluid volume as well as respond to the disturbance of acid-base balance. 

See also acidosis, alkalosis (disturbances of acid-base balance), bicarbonate, carbon dioxide, (parameters used in... 

There is no specific antidote. Supportive care should be instituted for all patients with history of serious boric acid exposure. Substantial recent ingestions may benefit from administration of activated charcoal. Fluid and electrolyte balance, correction of acid/base disturbance, and control of seizures are essential to therapy. Hemodialysis has been successfully used to treat acute boric acid poisoning. Sodium bicarbonate may be used for any metabolic acidosis. 

The observed [H ] in any acid-base disorder reflects the balance between the primary disturbance and the amount of compensation. 

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