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Metabolic Acidosis

Metabolic acidosis is a metabolic state in the body where there is an increase of acid in the body fluids. Metabolic acidosis is also physiologically defined as the primary reduction in HCO3 ion concentration in the blood with a compensatory reduction in PCO2 ion levels while pH remains subnormal.


Davenport Fig 12
Davenport Fig 12
Davenport Fig 12, CC BY-SA 3.0

Presentation

Most cases of metabolic acidosis present with non-specific signs and symptoms. These symptomatology and signs are most commonly seen among patients with established metabolic acidosis:

  • Hyperventilation: The respiratory centers are stimulated to cause hyperventilation to help eliminate carbon dioxide from the blood during acidotic states. 
  • Dyspnea: Breathing will be too fast and shallow impairing adequate oxygen exchange in the lungs.
  • Chest pain: The acidic plasma triggers the release of some cytokines that may cause angina and temporary coronary vasospasm.
  • Palpitation: The compensatory tachycardia will be felt as palpitation.
  • Neurologic signs: Headache and confusion are common findings when the cerebrospinal fluid becomes acidic.
  • Fatigue and weakness: Sodium channels are impaired during metabolic acidosis causing an essential hyponatremia in the extracellular space lowering the action potential in muscles.
  • Nausea and vomiting: The toxic state of metabolic acidosis is exemplified as nausea and vomiting among children.
  • Bone pains: The acidotic state causes vasospasm of the smaller arterioles that supply the bones presenting as sharp bone pains. Chronic calcium depletion with the acidemic state can also cause untimely osteoporosis among patients. 
Kussmaul Respiration
  • Infants will try to correct metabolic acidosis by a reflex respiratory alkalosis using hyperventilation and Kussmaul respirations.[mhmedical.com]
  • Those in metabolic acidosis may exhibit deep, rapid breathing called Kussmaul respirations which is classically associated with diabetic ketoacidosis.[en.wikipedia.org]
  • EFFECTS Respiratory Effects hyperventilation (Kussmaul respirations) – this is the compensatory response shift of oxyhaemoglobin dissociation curve (ODC) to the right – due to the acidosis occurs rapidly decreased 2,3 DPG levels in red cells (shifting[lifeinthefastlane.com]
  • Patients may be hypotensive and tachycardic due to dehydration and acidosis; they may breathe rapidly and deeply to compensate for acidemia (Kussmaul respirations). They may also have fruity breath due to exhaled acetone.[merckmanuals.com]
  • Kussmaul's respiration may be noted where there is deep, slowly rhythmic breathing that increases the minute tidal volume. Children with chronic metabolic acidosis may have growth restriction and show signs of rickets.[patient.info]
Hyperpnea
  • The resulting tachypnea and hyperpnea reduces the PaCO 2 in an attempt to increase the pH back toward normal.[emedicine.com]
  • Symptoms and signs in severe cases include nausea and vomiting, lethargy, and hyperpnea. Diagnosis is clinical and with ABG and serum electrolyte measurement. The cause is treated; IV sodium bicarbonate may be indicated when pH is very low.[msdmanuals.com]
  • The most characteristic sign is hyperpnea (long, deep breaths at a normal rate), reflecting a compensatory increase in alveolar ventilation; this hyperpnea is not accompanied by a feeling of dyspnea.[merckmanuals.com]
Tachypnea
  • During the initial examination by the physician at our hospital, the patient presented with tachypnea, a precordinal burning sensation, nausea and metabolic acidosis.[ncbi.nlm.nih.gov]
  • The resulting tachypnea and hyperpnea reduces the PaCO 2 in an attempt to increase the pH back toward normal.[emedicine.com]
  • Tachypnea and hyperventilation worsened during the ensuing 12 h. Blood gas analysis showed severe metabolic acidosis resulting in hypocapnia and a normal pH ( table 1 ).[anesthesiology.pubs.asahq.org]
Abnormal Breathing
  • Other symptoms for lactic acidosis include: Nausea Vomiting Abdominal pain Lethargy Abnormal breathing Low blood pressure Irregular heart rhythm Causes of Lactic Acidosis Lactic Acidosis is caused if a person reaches the anaerobic threshold or lactate[acidalkalinediet.net]
Vomiting
  • Laboratory examinations reveal the presence of significant metabolic alkalosis despite the severe vomiting of the patient. Hypochloremic alkalosis would be expected to be present in this patient.[ncbi.nlm.nih.gov]
  • Clinical presentation is heterogeneous, usually characterised by repetitive vomiting and diarrhoea, lethargy, failure to thrive until to dehydration with hypotension and shock.[ncbi.nlm.nih.gov]
  • Approximately 60 mL (20 mL/day) was used and after the third application he developed agitation, nausea, vomiting, respiratory distress, tachycardia, and metabolic acidosis. His clinical symptoms and metabolic acidosis normalized within 20 hours.[ncbi.nlm.nih.gov]
  • We report a previously healthy 19-month-old female infant admitted to the emergency department (ED) with vomiting and tonic-clonic seizure. On physical examination, she was comatose and presented signs of decompensated shock with Kussmaul breathing.[ncbi.nlm.nih.gov]
  • Nausea and vomiting: The toxic state of metabolic acidosis is exemplified as nausea and vomiting among children. Bone pains: The acidotic state causes vasospasm of the smaller arterioles that supply the bones presenting as sharp bone pains.[symptoma.com]
Nausea
  • We describe the case of a 28-year-old otherwise healthy woman who presents to our emergency department with nausea for 2 days and severe vomiting for 1 day. She has no history of travel, and her medical history is unremarkable.[ncbi.nlm.nih.gov]
  • However, eight days after admission, he again reported nausea, a venous blood gas revealed metabolic acidosis with a normal anion gap.[ncbi.nlm.nih.gov]
  • Approximately 60 mL (20 mL/day) was used and after the third application he developed agitation, nausea, vomiting, respiratory distress, tachycardia, and metabolic acidosis. His clinical symptoms and metabolic acidosis normalized within 20 hours.[ncbi.nlm.nih.gov]
  • During the initial examination by the physician at our hospital, the patient presented with tachypnea, a precordinal burning sensation, nausea and metabolic acidosis.[ncbi.nlm.nih.gov]
  • Uncontrolled, deep breathing Nausea and vomiting Weakness or confusion Not able to be woken easily How is metabolic acidosis diagnosed? Blood and urine tests are done to check oxygen, carbon dioxide, and acid levels.[drugs.com]
Hypotension
  • Clinical presentation is heterogeneous, usually characterised by repetitive vomiting and diarrhoea, lethargy, failure to thrive until to dehydration with hypotension and shock.[ncbi.nlm.nih.gov]
  • However, a change in consciousness and hypotension subsequently developed 6h later, combined with severe metabolic acidosis (pH7.16), high anion gap (25.5), and high osmolal gap (83). A presumed diagnosis of methanol intoxication was suspected.[ncbi.nlm.nih.gov]
  • CASE REPORT An otherwise-healthy 24-year-old female presented for elective spine surgery and was found to have metabolic acidosis, hypotension, and polyuria intraoperatively.[ncbi.nlm.nih.gov]
  • Metabolic acidosis due to paraldehyde overdose is exceedingly rare Iron and isoniazid are just two of many drugs and toxins that cause hypotension and lactic acidosis (isoniazid can also generate a component of ketoacidosis).[emergencymedicinecases.com]
  • […] acidosis due to poor ventilation resulting in a raised [H ] and raised P CO 2 Anion gap [Na K ] - [Cl - HCO 3 - ] usual reference range 12-20 mmol/L Causes of lactic acidosis Type A - tissue hypoxia severe hypoxia, severe anaemia, shock, haemorrhage, hypotension[pathology.leedsth.nhs.uk]
Tachycardia
  • Commonest signs were tachycardia (100%) and moaning (73%). At presentation 52% were in cardiogenic shock. Response to thiamine was dramatic with moaning and irritability subsiding in two hours and tachycardia in four hours.[ncbi.nlm.nih.gov]
  • Approximately 60 mL (20 mL/day) was used and after the third application he developed agitation, nausea, vomiting, respiratory distress, tachycardia, and metabolic acidosis. His clinical symptoms and metabolic acidosis normalized within 20 hours.[ncbi.nlm.nih.gov]
  • Tachycardia is the most common cardiovascular effect seen with a mild metabolic acidosis. As the serum pH continues to fall below 7.2, myocardial depression occurs because hydrogen ions act as a negative inotrope and peripheral vasodilation occurs.[emedicine.com]
  • Initial evaluation revealed tachycardia (111/min,) mild hypothermia (95.5 o F,) and a depressed level of consciousness with non-focal neurological examination. Blood glucose was 362 mg/dL.[thepoisonreview.com]
  • Palpitation: The compensatory tachycardia will be felt as palpitation. Neurologic signs: Headache and confusion are common findings when the cerebrospinal fluid becomes acidic.[symptoma.com]
Uremia
  • ., methanol, ethylene glycol), uremia, and acute renal failure. Laboratory workup was remarkable only for elevated serum and urinary ketone levels, believed to be secondary to starvation ketoacidosis.[ncbi.nlm.nih.gov]
  • Description English: Causes of high anion-gap metabolic acidosis Mnemonic "CAT MUDPILES": Carbon monoxide, Cyanide, Congenital heart failure Aminoglycosides Teophylline, Toluene (Glue-sniffing) Methanol Uremia Diabetic ketoacidosis, Alcoholic ketoacidosis[commons.wikimedia.org]
  • Causes of elevated Anion gap acidosis is best remembered by the mnemonic KULT or the popular MUDPILES M Methanol U Uremia D DKA (also AKA and starvation) P Paraldehyde I INH L Lactic acidosis E Ethylene Glycol S Salycilate K Ketoacidosis (DKA,alcoholic[web.archive.org]
  • […] isoniazid Sulfates, metformin Propylene glycol (metabolized to L and D-lactate and is often found in infusions for certain intravenous medications used in the intensive care unit) Massive rhabdomyolysisA mnemonic can also be used – MUDPILES M-Methanol U-Uremia[en.wikipedia.org]
  • Causes: Metabolic Acidosis and Elevated Anion Gap (Mnemonic: "MUD PILERS") Methanol , Metformin Uremia Diabetic Ketoacidosis (DKA), Alcohol ic ketoacidosis or starvation ketosis Paraldehyde, Phenformin (neither used in U.S. now) Propofol Infusion Syndrome[fpnotebook.com]
Confusion
  • You become weak or confused. You cannot be woken easily. Care Agreement You have the right to help plan your care. Learn about your health condition and how it may be treated.[drugs.com]
  • People with respiratory acidosis often have headache and confusion, and breathing may appear shallow, slow, or both. Tests on blood samples typically show pH below the normal range. Doctors treat the cause of the acidosis.[merckmanuals.com]
  • Some confusion may occur in patients admitted with 'collapse' and in extremis .[pathology.leedsth.nhs.uk]
  • Patients with metabolic acidosis develop rapid breathing, confusion, lethargy, shock and, in untreated cases, death, according to MedlinePlus, a National Institutes of Health website.[livestrong.com]
Lethargy
  • Clinical presentation is heterogeneous, usually characterised by repetitive vomiting and diarrhoea, lethargy, failure to thrive until to dehydration with hypotension and shock.[ncbi.nlm.nih.gov]
  • Symptoms and signs in severe cases include nausea and vomiting, lethargy, and hyperpnea. Diagnosis is clinical and with ABG and serum electrolyte measurement. The cause is treated; IV sodium bicarbonate may be indicated when pH is very low.[msdmanuals.com]
  • Patients with metabolic acidosis develop rapid breathing, confusion, lethargy, shock and, in untreated cases, death, according to MedlinePlus, a National Institutes of Health website.[livestrong.com]
Stupor
  • We report a 33 year-old woman addicted to chronic unspecified solvents abuse with stupor, respiratory disorders, tetraplegia and severe metabolic acidosis.[ncbi.nlm.nih.gov]
  • In respiratory acidosis, the earliest symptoms are Drowsiness may progress to stupor and coma as the oxygen in the blood becomes inadequate.[merckmanuals.com]
  • Extreme acidemia leads to neurological and cardiac complications: Neurological: lethargy, stupor, coma, seizures Cardiac: Abnormal heart rhythms (e.g., ventricular tachycardia) and decreased response to epinephrine, both leading to low blood pressurePhysical[en.wikipedia.org]
  • Examination Lethargy, stupor and progression to a state of coma may occur, particularly in cases of poisoning. An intoxicated-appearing patient who has no smell of alcoholic drink on their breath may have ingested ethylene glycol.[patient.info]
Somnolence
  • Lethargy and somnolence are symptoms of more severe decompensation. Patients may be hypotensive and tachycardic due to dehydration and acidosis; they may breathe rapidly and deeply to compensate for acidemia (Kussmaul respirations).[merckmanuals.com]
Neglect
  • […] review, we briefly look at the more relevant, though scanty, studies which have, over time, addressed the above-mentioned points, with the hope that in the future the interest of transplant nephrologists and surgeons will grow towards this unreasonably neglected[ncbi.nlm.nih.gov]

Workup

The following laboratory examinations and tests are utilized for the work up of patients with metabolic acidosis:

  • Serum electrolytes: The bicarbonate (HCO3) ion is usually inadequate during metabolic acidosis. 
  • Arterial blood gases (ABG): Blood gases analysis will reveal a pH level less than 7.4 during acidotic states. Concentration of HCO3 can also be determined in the ABG [4].
  • Urinalysis: Urine pH may be determined from the urinalysis. Electrolytes such as sodium, chloride, and potassium can also be measured in the urine [5]. The determination of ketones in the urine is associated with diabetic, starvation, and alcoholic ketoacidosis.
  • Anion gap: An increasing anion gap (AG) is indicative of an acidemic state where there is an increased number of undetected ions in the serum [6]. 
  • Complete blood count: An elevated white blood cell (WBC) count may connote septicemia which could cause lactic acidosis.
  • Blood urea nitrogen (BUN): This renal function test is sensitive in assessing the degree of metabolic acidosis during renal failure [7].
  • Serum lactate level: An elevation of up to 3 times the normal serum lactate level is indicative of lactic ketoacidosis. 
  • Salicylate level in serum: An elevated serum level of salicylate from oral medications can induce metabolic acidosis.
  • Iron serum level: Iron levels exceeding 300 mg/dl is already considered toxic and could consequently lead to metabolic acidosis. 
  • Electrocardiography (ECG): This test will detect rhythm abnormalities in the heart during eg. hyperkalemia.
Hypercapnia
  • The development of normocapnia or hypercapnia when a severe metabolic acidosis is present often signals respiratory muscle fatigue, impending respiratory failure, and the possible need for initiating mechanical ventilation.[emedicine.com]
  • Post-hypocapnia In prolonged hypercapnia renal tubular cells compensate for a prolonged respiratory alkalosis by decreasing reclaimation and generation of HCO 3 (which takes 12-24 hrs for full affect).[nimbot.com]
  • In any condition, sodium bicarbonate may also cause sodium and volume overload, hypokalemia, and, by inhibiting respiratory drive, hypercapnia.[merckmanuals.com]
  • References Prieto de Paula JM, Villamandos Nicas V, Cancelo Suarez P, del Portillo Rubi A, Guillem Ares E, Prada Minguez A, Sanz de la Fuente H: Efficacy of acetazolamide treatment of patients with hypercapnia and superimposed metabolic alkalosis.[anesthesiology.pubs.asahq.org]
  • […] mechanical ventilation settings Table 4 : Selected causes of metabolic alkalosis Hypovolemia with Cl- depletion GI loss of H Vomiting, gastric suction, villous adenoma, diarrhea with chloride-rich fluid Renal loss H Loop and thiazide diuretics, post-hypercapnia[thoracic.org]
Hypocapnia
  • Blood gas analysis showed severe metabolic acidosis resulting in hypocapnia and a normal pH ( table 1 ).[anesthesiology.pubs.asahq.org]
  • Post-hypocapnia In prolonged hypercapnia renal tubular cells compensate for a prolonged respiratory alkalosis by decreasing reclaimation and generation of HCO 3 (which takes 12-24 hrs for full affect).[nimbot.com]
  • Mineralocorticoid Deficiency Angiotensin Deficiency: Liver Failure ACE Inhibitor Renin Deficiency Aging Extracellular fluid volume expansion Lead Beta Blocker s Prostaglandin Inhibitor Methyldopa Carbonic anhydrase inhibitor Acetazolamide Mefenamic acid Post-hypocapnia[fpnotebook.com]
Staphylococcus Aureus
  • An 82-year-old white woman was admitted to our intensive care unit because of septic shock caused by right knee methicillin-sensitive Staphylococcus aureus-induced arthritis.[ncbi.nlm.nih.gov]

Treatment

The goal in the treatment of metabolic acidosis is to raise the serum pH to more than 7.2 to prevent life-threatening complications like cardiac arrhythmia. The most common drug used to balance metabolic acidosis is sodium bicarbonate [8]. Bicarbonate deficit is generally computed as desired HCO3 is equal to HCO3 deficit per Liter multiplied by 0.5 times body weight.

This computation will give a crude estimate of the HCO3 deficit in serum where sodium bicarbonate is administered intravenously to correct the imbalance. In the same way potassium citrate can also be given to correct metabolic acidosis with hypokalemia. Oral sodium bicarbonate is indicated for metabolic acidosis states that requires exogenous bases or alkalis to correct [9]. Researches have determined that potassium citrate may be superior to sodium bicarbonate because it requires lesser volume and does propagate the unnecessary excretion of calcium ion in the urine [10].

Prognosis

In general, the prognosis of metabolic acidosis is related to the underlying condition that gave rise to it. Cohort studies have shown that mortality with metabolic acidosis is usually caused by unabated acidotic states from hyperchloremia [3]. Significant morbidity is also observable among patients with uncorrected and late correction of acid-base imbalances from the time of admission. Severe uncorrected metabolic acidosis can lead to shock or death.

Etiology

Medical conditions that lead to the buildup of acid in the body can potentially cause metabolic acidosis. These medical conditions include:

Epidemiology

There are no exact epidemiologic data that give the incidence and prevalence of metabolic acidosis. The relative prevalence of this metabolic state is reflected in each primary disease etiology that result in this acidemic state. Moreover, metabolic acidosis is oftentimes underdiagnosed and underdocumented because metabolic acidosis is just a mere sign of a primary disease process.

Sex distribution
Age distribution

Pathophysiology

In general, the basic pathophysiology of metabolic acidosis is two folds. There could be an increased acid production within any organ system or there is an inadequate production of bicarbonates from the buffering systems of the body [2]. The body regulates plasma acidity by means of these buffering systems: the bicarbonate buffering system, renal compensatory system, respiratory compensatory system, and the intracellular absorption of hydrogen atoms. The bicarbonate system receives the hydrogen from the acidic compounds and neutralizes them into carbon dioxide and water. Any imbalance in the buffering system moves the pH lower than 7.4 making the serum acidic.

Prevention

Prevention of metabolic acidosis is grossly dependent on the primary prevention of its underlying causes. Diabetic control is essential to prevent diabetic ketoacidosis from ensuing. Alcohol should be taken in moderation to avoid alcoholic ketoacidosis from taking place. Athletic sports and exercises should be done in moderation to prevent lactic acidosis from developing. The injudicious use of salicylate-base pain relievers and iron supplements must be checked to prevent it’s toxicity that may lead to metabolic acidosis.

Summary

Metabolic acidosis is defined as a medical condition where there is an imbalance of the acid-base ions causing plasma acidity. The metabolic acidosis state is usually a sign of underlying disease process. Correction of the primary cause of the metabolic imbalance will normalize or reverse the metabolic state. An indepth understanding of the nature of the acid-base regulation mechanism is required to understand the complex processes that give rise to metabolic acidosis.

Patient Information
  • Definition: Metabolic acidosis is defines as a clinical condition where there is an imbalance of the acid-base ions causing too much acid in plasma.
  • Cause: Ketoacidosis is the leading cause of metabolic acidosis which could be brought about by diabetes, alcoholism, starvation, and cancer. Hyperchloremic states with diarrhea and vomiting may also induce acidemic states in the serum.
  • Symptoms: Acidotic patients will present with varying degrees of dyspnea, hyperventilation, chest pains, palpitation, and bone pain. 
  • Diagnosis: The ideal workup for metabolic acidosis include ABG, CBC, serum lactate levels, and ECG readings. 
  • Treatment and follow-up: The prompt correction of the acidemic state is imperative to prevent life-threatening arrhythmia. Patients may be given sodium bicarbonate intravenously, oral sodium bicarbonate, and potassium citrate to correct the metabolic acidosis.

References

Article

  1. 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.
  2. Mitch WE. Metabolic and clinical consequences of metabolic acidosis. J Nephrol. 2006; 19 Suppl 9:S70-5 (ISSN: 1121-8428)
  3. Maciel AT, Park M. Differences in acid-base behavior between intensive care unit survivors and nonsurvivors using both a physicochemical and a standard base excess approach: a prospective, observational study. J Crit Care. Dec 2009; 24(4):477-83.
  4. Schauer KL, Freund DM, Prenni JE, Curthoys NP. Proteomic profiling and pathway analysis of the response of rat renal proximal convoluted tubules to metabolic acidosis. Am J Physiol Renal Physiol. 2013; 305(5):F628-40 
  5. Pereira PC, Miranda DM, Oliveira EA, Silva AC. Molecular pathophysiology of renal tubular acidosis. Curr Genomics. Mar 2009; 10(1):51-9.
  6. Reddy P, Mooradian AD. Clinical utility of anion gap in deciphering acid-base disorders. Int J Clin Pract. Oct 2009; 63(10):1516-25.
  7. Mathur RP, Dash SC, Gupta N, Prakash S. Effects of correction of metabolic acidosis on blood urea and bone metabolism in patients with mild to moderate chronic kidney disease: a prospective randomized single blind controlled trial. Ren Fail. 2006; 28(1):1-5.
  8. Goraya N, Simoni J, Jo CH, Wesson DE. A comparison of treating metabolic acidosis in CKD stage 4 hypertensive kidney disease with fruits and vegetables or sodium bicarbonate. Clin J Am Soc Nephrol. Mar 2013; 8(3):371-81.
  9. Abramowitz MK, Melamed ML, Bauer C, Raff AC, Hostetter TH. Effects of oral sodium bicarbonate in patients with CKD. Clin J Am Soc Nephrol. May 2013; 8(5):714-20.
  10. Starke A, Corsenca A, Kohler T, Knubben J, Kraenzlin M, Uebelhart D, et al. Correction of metabolic acidosis with potassium citrate in renal transplant patients and its effect on bone quality. Clin J Am Soc Nephrol. Sep 2012; 7(9):1461-72.

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Last updated: 2018-06-22 06:08