Acidosis (Acidoses)

Acidosis is the condition of having too much acid in the blood and other body fluids with two classifications – metabolic acidosis or respiratory acidosis.

Acidosis is caused by the following process: biochemical.

Presentation

Metabolic acidosis
The signs will depend on the underlying cause. Usually there will be a rapid breathing (tachypnoea), lethargy and confusion with a headache. Severe disease can progress to shock or death. There is a fruity smell from the ketones of diabetic acidosis [6].

Respiratory acidosis:
Presenting signs can include lethargy or fatigue, shortness of breath, confusion and sleepiness [7].

Workup

A full history and a thorough clinical examination will allow a correct diagnosis.

Laboratory support will provide extra information with arterial blood gas analyses and electrolyte analysis with a basic metabolic panel. These will confirm the acidosis and identify whether it is metabolic or respiratory in origins [8].

Treatment

The mainstay of treatment is the use of appropriate fluid therapy using either oral or intravenous routes.

Sodium acetate may be used specifically to neutralise the acids.

At the same time the underlying cause must be treated.

In the most severe cases, severe measures such as mechanical ventilation or liver transplantation may be indicated [9].

Prognosis

The prognosis is generally favourable if prompt treatment is initiated. However, complications depend on the underlying cause.

Etiology

Acidosis occurs when the pH (hydrogen ion concentration) of blood plasma falls below 7.35.

  1. Respiratory acidosis (also known as hypercapnic acidosis) is the result of too much carbon dioxide remaining in the body because inadequate amounts are being removed by breathing.
  2. Metabolic acidosis occurs when either too much acid is produced in the body or too little is removed by the kidneys [2].

Epidemiology

1. Respiratory acidosis can be caused by inadequate respiratory function for several underlying reasons -

2. Several different forms of metabolic acidosis can occur with several various types of underlying pathology:

Lactic acidosis occurs as a result of the build-up of lactic acid -

Diabetic acidosis (also known as diabetic ketoacidosis – DKA) occurs as a result of the accumulation of acidic ketone bodies during uncontrolled diabetes mellitus.

Hyperchloraemic acidosis occurs with the loss of sodium bicarbonate from the body, e.g. sever diarrhoea or vomiting.

Other reasons for metabolic acidosis include – [3]

Sex distribution
Age distribution

Pathophysiology

Metabolic acidosis can either be caused when there is inadequate removal of excessive metabolicacids by the kidneys or over-production of metabolic acids elsewhere in body by other disturbed systems. These latter include urea and creatinine as well as the metabolic residues of protein catabolism. Overproduction of lactic acid can occur with excessive exercise or as a result of hypoxia in tissues with poor blood perfusion or low blood oxygen levels [4].
Stimulation of chemoreceptors by the raised acid levels leads to increased alveolar ventilation and results in some compensation for metabolic acidosis by the lungs with increased carbon dioxide exhalation. This alters the body’s buffering system to further reduce the metabolic acidosis.

Respiratory acidosis is usually the result of ineffective breathing and to return this back to a normal condition it will usually be useful to reverse the acidosis. However, where there is severe disturbance, e.g. trauma or nerve paralyses, mechanical ventilation may be needed as well [5].

Prevention

Mechanisms for prevention depend on the underlying cause. Metabolic acidosis can be prevented by ensuring the proper management of the underlying causes, e.g hepatic, renal and diabetic disease as well as avoiding excessive exercise or dehydration [10].

Summary

Normally the kidneys and the lungs maintain the balance between acids and bases in the body as part of homoeostasis so that the level of acidity (pH) is maintained within a narrow range – about 7.4. When either the acids build up or the bicarbonate (base) is lost, acidosis develops [1].

Patient Information

Definition: Acidosis is a buildup of acids in the body so that the pH of the blood plasma falls below 7.35


Cause: There are two types of acidosis depending on the underlying cause.

1. Metabolic acidosis - in which the kidneys are unable to effectively remove the acids produced by the body’s metabolism or in which the body is over-producing certain acids so that normal mechanisms can no longer maintain the level of hydrogen ions within the normal range. Potential causes include uncontrolled diabetes, over-exercise, poor diet, dehydration, overuse of drugs, diseases of the kidney and liver.


2. Respiratory acidosis results from the inability of the lungs to effectively remove carbon dioxide from the body. Changes in the lung ventilation may be caused by such chronic diseases as asthma, chest deformities, cancer, trauma to the chest or altered nerve function.


Symptoms: The symptoms of acidosis are similar for both the respiratory and metabolic forms. These include rapid breathing, lethargy, tiredness, headaches and confusion.

Diagnosis: Clinical signs and history should allow the underlying identification. Analysis of blood samples supported by a basic metabolic panel will provide an electrolyte analysis, while arterial blood gas analysis will conform the acidosis and identify whether this is metabolic or respiratory in origins.

Treatment: Fluid therapy with appropriate solutions, either oral or intravenous, will be used to correct the acidosis. Sometimes sodium acetate is used separately to neutralize the acids. Correcting the underlying problem is also important. Sometime mechanical ventilation is needed to correct severe respiratory acidosis.

Prevention: Correct management of the disease is critical to prevention its further development. Examples include controlling diabetes and avoiding excessive exercise or severe weather that might lead to dehydration.

Self-assessment

References

  1. Winter SD, Pearson JR, Gabow PA, et al. The fall of the serum anion gap. Arch Intern Med 1990; 150:311.
  2. Morimatsu H, Toda Y, Egi M, et al. Acid-base variables in patients with acute kidney injury requiring peritoneal dialysis in the pediatric cardiac care unit. J Anesth. 2009;23(3):334-40.
  3. Fernandez PC, Cohen RM, Feldman GM. The concept of bicarbonate distribution space: the crucial role of body buffers. Kidney Int 1989; 36:747.
  4. Pereira PC, Miranda DM, Oliveira EA, Silva AC. Molecular pathophysiology of renal tubular acidosis. Curr Genomics. Mar 2009;10(1):51-9
  5. Corey HE. Stewart and beyond: new models of acid-base balance. Kidney Int 2003; 64:777.
  6. Kraut JA, Kurtz I. Metabolic acidosis of CKD: diagnosis, clinical characteristics, and treatment. Am J Kidney Dis 2005; 45:978.
  7. Ehrsam RE, Heigenhauser GJ, Jones NL. Effect of respiratory acidosis on metabolism in exercise. J Appl Physiol. Jul 1982;53(1):63-9.
  8. Wiseman AC, Linas S. Disorders of potassium and acid-base balance. Am J Kidney Dis. May 2005;45(5):941-9
  9. Pierce NF, Fedson DS, Brigham KL, et al. The ventilatory response to acute base deficit in humans. Time course during development and correction of metabolic acidosis. Ann Intern Med 1970; 72:633.
  10. Adrogué HJ, Eknoyan G, Suki WK. Diabetic ketoacidosis: role of the kidney in the acid-base homeostasis re-evaluated. Kidney Int 1984; 25:591.

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