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How Do Kidneys Respond To Acidosis?

4.5 Respiratory Acidosis - Compensation

4.5 Respiratory Acidosis - Compensation

Acid-Base Physiology 4.5.1 The compensatory response is a rise in the bicarbonate level This rise has an immediate component (due to a resetting of the physicochemical equilibrium point) which raises the bicarbonate slightly. Next is a slower component where a further rise in plasma bicarbonate due to enhanced renal retention of bicarbonate. The additional effect on plasma bicarbonate of the renal retention is what converts an "acute" respiratory acidsosis into a "chronic" respiratory acidosis. As can be seen by inspection of the Henderson-Hasselbalch equation (below), an increased [HCO3-] will counteract the effect (on the pH) of an increased pCO2 because it returns the value of the [HCO3]/0.03 pCO2 ratio towards normal. pH = pKa + log([HCO3]/0.03 pCO2) 4.5.2 Buffering in Acute Respiratory Acidosis The compensatory response to an acute respiratory acidosis is limited to buffering. By the law of mass action, the increased arterial pCO2 causes a shift to the right in the following reaction: CO2 + H2O <-> H2CO3 <-> H+ + HCO3- In the blood, this reaction occurs rapidly inside red blood cells because of the presence of carbonic anhydrase. The hydrogen ion produced is buffered by intracellular proteins and by phosphates. Consequently, in the red cell, the buffering is mostly by haemoglobin. This buffering by removal of hydrogen ion, pulls the reaction to the right resulting in an increased bicarbonate production. The bicarbonate exchanges for chloride ion across the erythrocyte membrane and the plasma bicarbonate level rises. In an acute acidosis, there is insufficient time for the kidneys to respond to the increased arterial pCO2 so this is the only cause of the increased plasma bicarbonate in this early phase. The increase in bicarbonate only partially returns the extracel Continue reading >>

Metabolic Acidosis

Metabolic Acidosis

What is metabolic acidosis? The buildup of acid in the body due to kidney disease or kidney failure is called metabolic acidosis. When your body fluids contain too much acid, it means that your body is either not getting rid of enough acid, is making too much acid, or cannot balance the acid in your body. What causes metabolic acidosis? Healthy kidneys have many jobs. One of these jobs is to keep the right balance of acids in the body. The kidneys do this by removing acid from the body through urine. Metabolic acidosis is caused by a build-up of too many acids in the blood. This happens when your kidneys are unable to adequately remove the acid from your blood. What are the signs and symptoms? Not everyone will have signs or symptoms. However, you may experience: Long and deep breaths Fast heartbeat Headache and/or confusion Weakness Feeling very tired Vomiting and/or feeling sick to your stomach (nausea) Loss of appetite If you experience any of these, it is important to let your healthcare provider know immediately. What are the complications of metabolic acidosis if I have kidney disease or kidney failure? Increased bone loss (osteoporosis): Metabolic acidosis can lead to a loss of bone in your body. This can lead to a higher chance of fractures in important bones like your hips or backbone. Progression of kidney disease: Metabolic acidosis can make your kidney disease worse. Exactly how this happens is not clear. As acid builds up, kidney function lowers; and as kidney function lowers, acid builds up. This can lead to the progression of kidney disease. Muscle loss: Albumin is an important protein in your body that helps build and keep muscles healthy. Metabolic acidosis lowers the amount of albumin created in your body, and leads to muscle loss, or what is called Continue reading >>

Renal Response To Acid-base Imbalance

Renal Response To Acid-base Imbalance

The kidneys respond to acid-base disturbances by modulating both renal acid excretion and renal bicarbonate excretion. These processes are coordinated to return the extracellular fluid pH, and thus blood pH, to normal following a derangement. Below we discuss the coordinated renal response to such acid-base disturbances. Acidosis refers to an excess extracellular fluid H+ concentration and thus abnormally low pH. The overall renal response to acidosis involves the net urinary excretion of hydrogen, resorption of nearly all filtered bicarbonate, and the generation of novel bicarbonate which is added to the extracellular fluid. Processes of renal acid excretion result in both direct secretion of free hydrogen ions, thus acidifying the urine, as well as secretion of hydrogen in the form of ammonium. These mechanisms are molecularly coupled to the generation of fresh bicarbonate, which is added to the extracellular fluid. Additionally, as discussed in renal bicarbonate excretion, nearly all filtered bicarbonate is resorbed and thus its urinary loss is minimized. Together, these processes slowly reduce ECF hydrogen ions and increase ECF bicarbonate concentrations, thus gradually raising blood pH to its normal value. Alkalosis refers to a insufficient extracellular fluid H+ concentration and thus abnormally high pH. The overall response to alkalosis involves reduced urinary secretion of hydrogen and the urinary excretion of filtered bicarbonate. Renal acid excretion is minimized in the context of alkalosis, thus preventing further increases in the ECF pH. Instead, renal bicarbonate excretion is increased, resulting in loss of bicarbonate from the extracellular fluid, and an alkalinization of the urine. Together these processes reduce ECF bicarbonate concentrations and in doin Continue reading >>

Renal Compensation

Renal Compensation

Chronic Carbon Dioxide Retainer Renal compensation of respiratory acidosis is by increased urinary excretion of hydrogen ions and resorption of HCO3−. This relatively slow process occurs over several days. Slowly, pH reaches low normal values, but HCO3− levels and BE are increased. This is the situation of the patient with chronic respiratory failure. Pulmonary patients usually have chronic obstructive pulmonary disease or restrictive pulmonary disease, or they are morbidly obese. Increased Co2 stores are the rule, and the normal respiratory drive to Paco2 is obtunded. This group of patients is sensitive to O2 supplementation because respiratory drive is predominantly determined by hypoxemia. Patients with a Pao2 in the mid-50s and a Paco2 at the same level usually receive home O2 treatment, initially at night to reduce pulmonary hypertension and to relieve dyspnea. When the chronic Co2 retainer develops an acute respiratory problem and pH levels fall to less than 7.20, noninvasive ventilatory assistance is usually indicated. Fetoplacental Elimination of Metabolic Acid Load Fetal respiratory and renal compensation in response to changes in fetal pH is limited by the level of maturity and the surrounding maternal environment. However, although the placentomaternal unit performs most compensatory functions,3 the fetal kidneys have some, although limited, ability to contribute to the maintenance of fetal acid–base balance. The most frequent cause of fetal metabolic acidosis is fetal hypoxemia owing to abnormalities of uteroplacental function or blood flow (or both). Primary maternal hypoxemia or maternal metabolic acidosis secondary to maternal diabetes mellitus, sepsis, or renal tubular abnormalities is an unusual cause of fetal metabolic acidosis. Pregnant women, a Continue reading >>

Acid-base Disorders And The Kidney.

Acid-base Disorders And The Kidney.

In the normal human body, the extracellular fluid pH of 7.40 is closelyprotected. Any increase in acidity or alkalinity summons forth three lines ofdefense, starting immediately with the blood buffers, followed soon by therespiratory system's control of CO2, and finally purged by the renal excretion ofthe excess acid or base. The complex interrelated processes of the renalresponses require a few days to accomplish maximum compensation. We havepresented the fundamental principles governing maintenance of the acid-baseequilibrium to provide a conceptual framework for understanding the clinicaldisorders of hydrogen ion metabolism. The somewhat elusive concepts of endogenousacid production and net acid balance have also been reviewed to help reveal thepathophysiology of metabolic acidosis caused by renal tubular acidosis, chronicrenal failure, certain infant feedings, and total parenteral nutrition. Thedevelopment and perpetuation of metabolic alkalosis in relationship to chlorideand potassium deficiency have been examined. In the delineation of a clinicalacid-base disorder, the clinician must bear in mind the continual interactions ofelectrolytes and hormonal systems and should be prepared to reevaluate frequentlythe elected therapy against the changing responses, based on a thoroughunderstanding of physiology. The various types of renal tubular acidosis havemanifold facets but the basic understanding of their pathophysiology begins with the concept of the "anion gap," a point of reference that can be used in thedifferential diagnosis and treatment. In this chapter a number of new causes oftype IV renal tubular acidosis--currently considered to be the most common formof renal tubular acidosis--have been pointed out, along with special reference tothe mineral, electrolyte, Continue reading >>

Renal Tubular Acidosis

Renal Tubular Acidosis

Renal tubular acidosis (RTA) is a disease that occurs when the kidneys fail to excrete acids into the urine, which causes a person's blood to remain too acidic. Without proper treatment, chronic acidity of the blood leads to growth retardation, kidney stones, bone disease, chronic kidney disease, and possibly total kidney failure. The body's cells use chemical reactions to carry out tasks such as turning food into energy and repairing tissue. These chemical reactions generate acids. Some acid in the blood is normal, but too much acidacidosiscan disturb many bodily functions. Healthy kidneys help maintain acid-base balance by excreting acids into the urine and returning bicarbonatean alkaline, or base, substanceto the blood. This "reclaimed" bicarbonate neutralizes much of the acid that is created when food is broken down in the body. The movement of substances like bicarbonate between the blood and structures in the kidneys is called transport. One researcher has theorized that Charles Dickens may have been describing a child with RTA in the character of Tiny Tim from A Christmas Carol. Tiny Tim's small stature, malformed limbs, and periods of weakness are all possible consequences of the chemical imbalance caused by RTA.1 In the story, Tiny Tim recovers when he receives medical treatment, which would likely have included sodium bicarbonate and sodium citrate, alkaline agents to neutralize acidic blood. The good news is that medical treatment can indeed reverse the effects of RTA. To diagnose RTA, doctors check the acid-base balance in blood and urine samples. If the blood is more acidic than it should be and the urine less acidic than it should be, RTA may be the reason, but additional information is needed to rule out other causes. If RTA is the reason, additional in Continue reading >>

How Does The Renal System Compensate For Conditions Of Respiratory Alkalosis?

How Does The Renal System Compensate For Conditions Of Respiratory Alkalosis?

In order to function normally, your body needs a blood pH of between 7.35 and 7.45. Alkalosis is when you have too much base in your blood, causing your blood pH to rise above 7.45. The lungs and the kidneys are the two main organs involved in maintaining a normal blood pH. The lungs do this by blowing off carbon dioxide, since most of the acid in the body is carbonic acid, which is made from carbon dioxide during metabolic processes. The amount of carbon dioxide removed is controlled by your breathing rate. The kidneys maintain blood pH by controlling the amount of bicarbonate, which is a base that is excreted from the body. The kidneys also control the amount of acids excreted from the body. Respiratory alkalosis occurs when the lungs are blowing off more carbon dioxide than the body is producing. This usually occurs from hyperventilation. Your body's immediate response, after about 10 minutes of respiratory alkalosis, is a process called cell buffering. During cell buffering, hydrogen ions found in hemoglobin, proteins and phosphates, move out of the cells and into the extracellular fluid. There they combine with bicarbonate molecules and form carbonic acid. This process helps to reduce the amount of bicarbonate in the body and increase the amount of acid. However, while cell buffering occurs quickly, it does not have a huge effect on the body's pH. After about two to six hours of respiratory alkalosis the kidneys respond. They begin to limit the excretion of hydrogen and other acids and increase the excretion of bicarbonate. It usually takes the kidneys two or three days to reach a new steady state. In chronic respiratory alkalosis, the pH may constantly be high, but the body learns to adapt to it over time, with the help of the kidneys. Continue reading >>

Renal Regulation Of Metabolic Acidosis And Alkalosis

Renal Regulation Of Metabolic Acidosis And Alkalosis

1. 06/21/14 1 Normal Acid-Base Balance • Normal pH 7.35-7.45 • Narrow normal range • Compatible with life 6.8 - 8.0 ___/______/___/______/___ 6.8 7.35 7.45 8.0 Acid Alkaline 2. 06/21/14 2 PH Scale 3. 06/21/14 3 Acid & Base • Acid: • An acid is "when hydrogen ions accumulate in a solution" • It becomes more acidic • [H+] increases = more acidity • CO2 is an example of an acid. Base: A base is chemical that will remove hydrogen ions from the solution Bicarbonate is an example of a base. 4. 06/21/14 4 Acid and Base Containing Food: • To maintain health, the diet should consist of 60% alkaline forming foods and 40% acid forming foods. To restore health, the diet should consist of 80% alkaline forming foods and 20% acid forming foods. • Generally, alkaline forming foods include: most fruits, green vegetables, peas, beans, lentils, spices, herbs,seasonings,seeds and nuts. • Generally, acid forming foods include: meat, fish, poultry, eggs, grains, and legumes. 5. 06/21/14 5 Citric Acid And Lactic Acid Although both citric acid and lactic acid are acids BUT Citric acid leads to Alkalosis while Lactic acid to Acidosis due to metabolism 6. 06/21/14 6 Acidoses & Alkalosis • An abnormality in one or more of the pH control mechanisms can cause one of two major disturbances in Acid-BaseAcid-Base balance – AcidosisAcidosis – AlkalosisAlkalosis 7. 06/21/14 7 Acidosis • Acidosis is excessive blood acidity caused by an overabundance of acid in the blood or a loss of bicarbonate from the blood (metabolic acidosis), or by a buildup of carbon dioxide in the blood that results from poor lung function or slow breathing (respiratory acidosis). • Blood acidity increases when people ingest substances that contain or produce acid or when the lungs do not expel enou Continue reading >>

Acidosis And Alkolosis

Acidosis And Alkolosis

The normal pH value for the body fluids is between pH 7.35 and 7.45. When the pH value of body fluids is below 7.35, the condition is called acidosis, and when the pH is above 7.45, it is called alkalosis. Metabolism produces acidic products that lower the pH of the body fluids. For example, carbon dioxide is a by-product of metabolism, and carbon dioxide combines with water to form carbonic acid. Also, lactic acid is a product of anaerobic metabolism, protein metabolism produces phosphoric and sulfuric acids, and lipid metabolism produces fatty acids. These acidic substances must continuously be eliminated from the body to maintain pH homeostasis. Rapid elimination of acidic products of metabolism results in alkalosis, and the failure to eliminate acidic products of metabolism results in acidosis. The major effect of acidosis is depression of the central nervous system. When the pH of the blood falls below 7.35, the central nervous system malfunctions, and the individual becomes disoriented and possibly comatose as the condition worsens. A major effect of alkalosis is hyperexcitability of the nervous system. Peripheral nerves are affected first, resulting in spontaneous nervous stimulation of muscles. Spasms and tetanic contractions and possibly extreme nervousness or convulsions result. Severe alkalosis can cause death as a result of tetany of the respiratory muscles. Although buffers in the body fluids help resist changes in the pH of body fluids, the respiratory system and the kidneys regulate the pH of the body fluids. Malfunctions of either the respiratory system or the kidneys can result in acidosis or alkalosis. Acidosis and alkalosis are categorized by the cause of the condition. Respiratory acidosis or respiratory alkalosis results from abnormalities of the r Continue reading >>

Metabolic Acidosis

Metabolic Acidosis

Metabolic acidosis is a condition that occurs when the body produces excessive quantities of acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low (less than 7.35) due to increased production of hydrogen ions by the body or the inability of the body to form bicarbonate (HCO3−) in the kidney. Its causes are diverse, and its consequences can be serious, including coma and death. Together with respiratory acidosis, it is one of the two general causes of acidemia. Terminology : Acidosis refers to a process that causes a low pH in blood and tissues. Acidemia refers specifically to a low pH in the blood. In most cases, acidosis occurs first for reasons explained below. Free hydrogen ions then diffuse into the blood, lowering the pH. Arterial blood gas analysis detects acidemia (pH lower than 7.35). When acidemia is present, acidosis is presumed. Signs and symptoms[edit] Symptoms are not specific, and diagnosis can be difficult unless the patient presents with clear indications for arterial blood gas sampling. Symptoms may include chest pain, palpitations, headache, altered mental status such as severe anxiety due to hypoxia, decreased visual acuity, nausea, vomiting, abdominal pain, altered appetite and weight gain, muscle weakness, bone pain, and joint pain. Those in metabolic acidosis may exhibit deep, rapid breathing called Kussmaul respirations which is classically associated with diabetic ketoacidosis. Rapid deep breaths increase the amount of carbon dioxide exhaled, thus lowering the serum carbon dioxide levels, resulting in some degree of compensation. Overcompensation via respiratory alkalosis to form an alkalemia does not occur. Extreme acidemia leads to neurological and cardia Continue reading >>

Renal Response To Metabolic Acidosis: Role Of Mrna Stabilization

Renal Response To Metabolic Acidosis: Role Of Mrna Stabilization

Renal response to metabolic acidosis: Role of mRNA stabilization Hend Ibrahim , Ph.D., Yeon J. Lee , Ph.D., and Norman P. Curthoys , Ph.D. Department of Biochemistry and Molecular Biology Colorado State University Fort Collins, CO 80523-1870 Direct Correspondence to: Dr. Norman P. Curthoys, Department of Biochemistry and Molecular Biology, Campus Delivery 1870, Colorado State University, Fort Collins, CO 80523-1870. Phone: (970) 491-3123, FAX: (970) 491-0494, [email protected] The publisher's final edited version of this article is available at Kidney Int See other articles in PMC that cite the published article. The renal response to metabolic acidosis is mediated, in part, by increased expression of the genes encoding key enzymes of glutamine catabolism and various ion transporters that contribute to the increased synthesis and excretion of ammonium ions and the net production and release of bicarbonate ions. The resulting adaptations facilitate the excretion of acid and partially restore systemic acid-base balance. Much of this response may be mediated by selective stabilization of the mRNAs that encode the responsive proteins. For example, the glutaminase mRNA contains a direct repeat of 8-nt AU-sequences that function as a pH-response element (pH-RE). This element is both necessary and sufficient to impart a pH-responsive stabilization to chimeric mRNAs. The pH-RE also binds multiple RNA binding proteins, including -crystallin, AUF1 and HuR. The onset of acidosis initiates an ER-stress response that leads to the formation of cytoplasmic stress granules. -crystallin is transiently recruited to the stress granules and concurrently, HuR is translocated from the nucleus to the cytoplasm. Based upon the cumulative data, a mechanism for the stabilization of Continue reading >>

How The Kidneys Regulate Acid Base Balance

How The Kidneys Regulate Acid Base Balance

Acid-Base Balance Everyday processes like walking, the digestion of food, and the overall metabolism in your body produce a lot of acid as a byproduct. Because of this, you'd be a giant walking lemon if it wasn't for your kidneys. What I mean is, like a lemon, you'd be filled with acid if your kidneys weren't there to help you regulate your body's pH through something we call acid-base balance. This is a process whereby receptors are able to determine the pH of your body and blood and do something about it if it's too acidic or too basic. If an imbalance in the pH is detected by your lungs, buffers, or kidneys, your body springs into action to take care of the problem. In this lesson, we'll focus in on how the kidneys help to control the acid-base balance in your body. Protons and Buffers Whereas the buffers in your body and your lungs are involved in the rapid adjustment of your blood's pH, the kidneys adjust the pH more slowly. Under normal conditions, the kidney's main role in acid-base balance is through the excretion of acid in the form of hydrogen (H+) ions. The kidneys secrete excess hydrogen ions primarily in the proximal tubule. The interesting thing to note is that while the proximal tubule secretes a lot of acid, the tubular fluid's pH remains virtually unchanged. This is because buffers filtered by the glomerulus, including phosphate and bicarbonate, help to minimize the acidity of the tubular fluid. In fact, what's really cool is that the pH of the tubular fluid, by the time it reaches the collecting duct, is about 7.4, which is exactly the pH of normal blood. The Collecting Duct However, by the time urine is excreted out of the body, it can be acidic, basic, or neutral. This is because the end-all, be-all gatekeeper in determining the final pH of urine is Continue reading >>

Renal Physiology Acid-base Balance

Renal Physiology Acid-base Balance

Sort Your patient's blood pH is too low (acidosis), caused by metabolic acidosis. After examining the patient, you find that the urine bicarbonate levels are too low (H+ is being reabsorbed) and blood carbon dioxide levels are too high (too much blood acid); What does this mean? Based on the patient's pCO2 levels are they compensating or not? This means that the original problem of a low bicarbonate level needs to be compensated for by the lungs, which need to hyperventilate, expelling more CO2 (an acid). Since this patient's pCO2 levels are also high (not expelling enough acid), they are NOT compensating. Patient's blood pH is too high (alkalosis). This can be caused by either respiratory or metabolic alkalosis. Let's say it is metabolic alkalosis. What do you need to check to see if patient is compensating? If bicarbonate levels are high (too much base) and blood CO2 levels are high (too much acid), what do the lungs need to do to compensate? What does the patient's elevated Pco2 levels tell you? Patients partial pressure of Carbon dioxide and bicarbonate Take shallower breaths to prevent loss of acid Patient is compensating Patient's blood pH is too high (alkalosis). This can be caused by either respiratory or metabolic alkalosis. Let's say it is metabolic alkalosis. What do you need to check to see if patient is compensating? If bicarbonate levels are high (too much base) and blood CO2 levels are low (too little acid), what do the lungs need to do to compensate? Since the patient's pCO2 level is low, this tells you what? Patients pCO2 and bicarbonate Take shallower breaths to prevent loss of acid Not compensating Continue reading >>

Handling Ph: How Your Body Regulates Acidity

Handling Ph: How Your Body Regulates Acidity

When it comes to pH, your body likes to keep a tight control of the balance between acidity and alkalinity. The normal range for pH in your body is between 7.35-7.45 so, very slightly alkaline. At times, this balance can be disrupted. I will be talking about what occurs. Now, we must think about the ways you can control acidity. One is to remove/add acid, the other is to remove/add base. So how can we do this? There are two places where we can do this — the lungs and the kidneys. The lungs may seem like a strange place for controlling pH however, if we consider how CO2 is transported from the tissues (read more here), we see that CO2 dissociates into carbonic acid. Hence, the higher the CO2 levels in the tissues, the lower the pH gets (more acidic). So, if we are experiencing an Acidosis (low pH), if we decrease our CO2, we can increase the pH. We do this by hyperventilating and blowing off our CO2 however, this is limited by the amount of CO2 we have in our bodies; once we have blown off all our CO2, there is no more that the lungs can do to help us compensate. Conversely, if we experience an Alkylosis (high pH) our lungs can try to compensate by slowing down our breathing to increase our CO2 however, this can be dangerous because it can cause hypoxia (lack of oxygen). The benefit of respiratory compensation is that it happens very quickly (a few minutes) however, it has a very limited range of effectiveness. The kidneys deal in acids and bases, they can excrete/retain H+ if needed and they also control the excretion/retention of bicarbonate (HCO3-). If you are acidotic, your kidneys will try to excrete H+ and retain HCO3-, if you are alkylotic, your kidneys will try to retain H+ and excrete HCO3-. The drawback of this is that it takes a few days to be effective but, Continue reading >>

Response To Disturbances

Response To Disturbances

The body tries to minimize pH changes and responds to acid-base disturbances with body buffers, compensatory responses by the lungs and kidney (to metabolic and respiratory disturbances, respectively) and by the kidney correcting metabolic disturbances. Body buffers: There are intracellular and extracellular buffers for primary respiratory and metabolic acid-base disturbances. Intracellular buffers include hemoglobin in erythrocytes and phosphates in all cells. Extracellular buffers are carbonate (HCO3–) and non-carbonate (e.g. protein, bone) buffers. These immediately buffer the rise or fall in H+. Compensation: This involves responses by the respiratory tract and kidney to primary metabolic and respiratory acid-base disturbances, respectively. Compensation opposes the primary disturbance, although the laboratory changes in the compensatory response parallel those in the primary response. This concept is illustrated in the summary below. Respiratory compensation for a primary metabolic disturbance: Alterations in alveolar ventilation occurs in response to primary metabolic acid-base disturbances. This begins within minutes to hours of an acute primary metabolic disturbance. Note that complete compensation via this mechanism may take up to 24 hours. Renal compensation for a primary respiratory disturbance: Here, the kidney alters excretion of acid (which influences bases as well) in response to primary respiratory disturbances. This begins within hours of an acute respiratory disturbance, but take several days (3-5 days) to take full effect. Correction of acid-base changes: Correction of a primary respiratory acid-base abnormality usually requires medical or surgical intervention of the primary problem causing the acid-base disturbance, e.g. surgical relief of a colla Continue reading >>

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