Updated: Aug 13, 2008
Metabolic alkalosis is an acid-base disturbance caused by an elevation in plasma bicarbonate (HCO3) concentration. This condition is not a disease; it is a sign or state encountered in certain disease processes. Although metabolic alkalosis may not be referred to as often as metabolic acidosis, it is the most common acid-base abnormality in hospitalized adults. Alkalosis refers to a loss of acid or gain of base in the extracellular fluid (ECF); alkalemia refers to a change in blood pH. Alkalosis is not necessarily accompanied by alkalemia.
The 2 types of metabolic alkalosis (ie, chloride-responsive, chloride-resistant) are classified based on the amount of chloride in the urine.
Chloride-responsive metabolic alkalosis involves urine chloride levels of less than 10 mEq/L and is characterized by decreased ECF volume and low serum chloride levels, such as occurs with vomiting. This type responds to administration of chloride salt.
Chloride-resistant metabolic alkalosis involves urine chloride levels of more than 20 mEq/L and is characterized by increased ECF volume. As the name implies, this type resists administration of chloride salt. Primary aldosteronism is an example of chloride-resistant metabolic alkalosis.
In most cases, metabolic alkalosis is caused by loss of hydrochloric acid (HCl) through the kidney or GI tract, especially due to vomiting. Occasionally, the condition is caused by disproportionate loss of chloride. Metabolic alkalosis is rarely caused by actual gain from administered HCO3.
Other causes of metabolic alkalosis include (1) loss of hydrogen ions (eg, due to vomiting or renal acid losses that exceed acid production from cellular metabolism), (2) disproportionate chloride loss compared with HCO3 loss (ie, the plasma concentration of HCO3 increases upon restriction to a smaller space of distribution), and (3) HCO3 administration (unusual because additional HCO3 is very quickly eliminated by the kidneys).
The consequences of metabolic alkalosis on organ systems depend on the severity of the alkalemia and the degree of respiratory compensation. If the elevated plasma HCO3 concentration is not accompanied by a rise in PCO2, the elevation of pH is much more severe.
Because metabolic alkalosis is a manifestation of a disease process rather than a disease itself, the incidence is unknown. In a review of 2000 hospitalized adults, Hodgkin et al noted that metabolic alkalosis was the most common acid-base disorder.1
Severe metabolic alkalosis is associated with increased morbidity and mortality, probably because of its profound influences on multiple organ systems and, more importantly, because of tissue anoxia caused by hypoventilation and shift of the oxygen-dissociation curve to the left.
No racial predilection has been reported.
Incidence is equal in males and females.
Metabolic alkalosis can occur in people of any age. A higher incidence of metabolic alkalosis after cardiac surgery in younger children has been reported.
Obtain historical data to pinpoint the nature of the disease causing metabolic alkalosis.
Increased neuromuscular excitability sometimes causes tetany or seizures. Generalized weakness may be noted if the patient also has hypokalemia. Signs and symptoms observed with metabolic alkalosis usually relate to the specific disease process that caused the acid-base disorder.
Alkalosis, Metabolic
Bartter Syndrome
Cystic Fibrosis
Pyloric Stenosis, Hypertrophic
Liddle syndrome
Primary aldosteronism
Hyperglucocorticoidism
DOC excess syndromes
Gastric fluid losses
Potassium depletion
Congenital chloride diarrhea
Mild or moderate metabolic alkalosis or alkalemia rarely requires correction. For severe metabolic alkalosis, therapy should address the underlying disease state, in addition to moderating the alkalemia. As with correction of any electrolyte or acid-base imbalance, the goal is to prevent life-threatening complications with the least amount of correction. The initial target pH and bicarbonate level in correcting severe alkalemia is approximately 7.55 mmol/L and 40 mmol/L, respectively, not values within the reference range.
Children with pyloric stenosis require surgical intervention (pyloromyotomy) following intravascular fluid expansion and correction of metabolic abnormalities.
Severe alkalemia should be initially managed in an ICU setting under the direction of a pediatric intensivist. Subsequent consultations should be obtained with specific specialists (eg, endocrinologist, nephrologist) to manage the underlying etiology responsible for the metabolic alkalosis.
Tailor dietary changes to the underlying disease.
Metabolic alkalosis that results from chloride depletion and volume contraction can often be corrected with volume replacement, but persistent severe metabolic alkalosis may require more specific therapy directed at moderating the alkalemia.
These solutions are the recommended therapeutic agents for rapid correction of severe metabolic alkalosis, especially metabolic alkalosis due to gastric losses of chloride.
Amount required to correct metabolic alkalosis is determined by estimating the amount of pH deficit, the volume, and the infusion rate of HCl solution.
IV HCl may be indicated in severe metabolic alkalosis (pH >7.55) or when NaCl or KCl cannot be administered because of volume overload or advanced renal failure. May also be indicated if rapid correction of severe metabolic alkalosis is warranted (eg, cardiac arrhythmia, hepatic encephalopathy, digoxin toxicity).
Typical preparation contains 0.1 N solution (ie, 100 mmol H+/L [mEq/L]) in D5W or 0.9% NaCl).
IV via central venous catheter: H+ ion deficit (mEq) = 0.3 X weight (kg) X (measured HCO3 - desired HCO3 [mEq/L])
Rate of H+ replacement: 0.1-0.2 mEq/kg/h
For example, 0.1 N solution IV at 100 mL/h provides about 10 mEq/h
Not established, limited data have been reported
None reported
Lack of central venous access
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Do not use HCl solutions with concentrations >0.2 N (increased venous irritation and potential hemolysis); concentrations >0.1 N have been reported to cause corrosive effects, even when administered through a central venous catheter; injection of HCl into a peripheral vein may cause extravasation and can produce severe tissue necrosis; monitor ABGs and serum electrolyte levels
Administer to correct severe metabolic alkalosis related to chloride deficiency. NH4 Cl is converted to ammonia and HCl by the liver. By releasing HCl, NH4 Cl may help correct metabolic alkalosis.
Available as 500-mg tabs and 26.75% parenteral for IV use. Parenteral contains 5 mEq/mL (267.5 mg/mL).
8-12 g/d PO divided q6h
1.5 g IV q6h; dilute solution to concentration <0.4 mEq/mL; not to exceed infusion rate of 1 mEq/kg/h
75 mg/kg/d PO/IV divided q6h; not to exceed 6 g/d and an infusion rate of 1 mEq/kg/h; dilute solution to concentration <0.4 mEq/mL
May reduce levels of aspirin, chlorpropamide, ephedrine, methadone, pseudoephedrine, spirolactone, and para-aminosalicylic acid (PSA)
Hepatic or renal failure
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Use with extreme caution in infants; may produce acidosis and hyperammonemia with encephalopathy; may cause GI irritation; monitor chloride levels, serum ammonia levels, and acid-base status
Essential for transmission of nerve impulses, contraction of cardiac muscle, and maintenance of intracellular tonicity, skeletal and smooth muscles, and normal renal function.
20-120 mEq PO qd
Up to 20 mEq/dose IV; dilute in >500 mL IV fluid for peripheral line infusion or >100 mL for central line infusion; not to exceed administration rate of 10 mEq/h unless cardiac monitoring in place
0.5-1 mEq/kg/dose IV; dilute in adequate IV fluid before administering by either peripheral or central IV; not to exceed administration rate of 10 mEq/h unless cardiac monitoring in place; may be prudent to not exceed 10 mEq in any one total dose, regardless if per Kg calculation indicates higher dose; recheck level, and administer additional dose as needed
Concurrent use with ACE inhibitors may result in elevated serum potassium concentrations; potassium-sparing diuretics and potassium-containing salt substitutes can produce severe hyperkalemia; caution if discontinuing potassium administration in patients maintained on digoxin (hypokalemia may result in digoxin toxicity)
Hyperkalemia; renal failure; conditions in which potassium retention is present; oliguria or azotemia; crush syndrome; severe hemolytic reactions; anuria; adrenocortical insufficiency
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Do not rapidly infuse; high plasma concentrations of potassium may cause death due to cardiac depression, arrhythmias, or arrest; plasma levels do not necessarily reflect tissue levels; monitor potassium replacement therapy whenever possible by continuous or serial ECG; when a concentration >40 mEq/L is infused, local pain and phlebitis may also follow
These agents may be used to treat chloride-resistant metabolic alkalosis.
A carbonic anhydrase inhibitor that blocks HCO3 reabsorption in the proximal renal tubules. A recent study demonstrated that acetazolamide causes increased renal excretion of sodium vs chloride, causing a net increase in serum chloride. Acetazolamide is also a diuretic and, therefore, may help decrease ECF volume that frequently accompanies chloride-resistant metabolic alkalosis.
5-10 mg/kg/d PO/IV divided q6h
5 mg/kg PO qd/qod
8-30 mg/kg/d IV/IM divided q6-8h; not to exceed 1 g/d
Can decrease therapeutic levels of lithium and alter excretion of drugs (amphetamines, quinidine, phenobarbital, salicylates) by alkalinizing urine
Documented hypersensitivity; hepatic disease; severe renal disease; adrenocortical insufficiency; severe pulmonary obstruction
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Caution with respiratory acidosis and diabetes mellitus (may increase blood glucose); IM administration is painful
Hodgkin JE, Soeprono FF, Chan DM. Incidence of metabolic alkalemia in hospitalized patients. Crit Care Med. Dec 1980;8(12):725-8. [Medline].
Moviat M, Pickkers P, van der Voort PH, van der Hoeven JG. Acetazolamide-mediated decrease in strong ion difference accounts for the correction of metabolic alkalosis in critically ill patients. Crit Care. Feb 2006;10(1):R14. [Medline].
Moffett BS, Moffett TI, Dickerson HA. Acetazolamide therapy for hypochloremic metabolic alkalosis in pediatric patients with heart disease. Am J Ther. Jul-Aug 2007;14(4):331-5. [Medline].
Adrogue HJ, Madias NE. Management of life-threatening acid-base disorders. Second of two parts. N Engl J Med. Jan 8 1998;338(2):107-11. [Medline].
Finberg L, Kravath RE, Hellerstein S. Metabolic Alkalosis. In: Water and Electrolytes in Pediatrics: Physiology, Pathophysiology, and Treatment. Philadelphia, Pa: WB Saunders; 1993:97-98.
Galla JH. Metabolic alkalosis. J Am Soc Nephrol. Feb 2000;11(2):369-75. [Medline].
Kokko JP, Tannen RL, eds. Metabolic Alkalosis. In: Fluids and Electrolytes. 1990. Philadelphia, Pa: WB Saunders; 356-376.
Maxwell MH, Kleeman CR, eds. Metabolic Alkalosis. In: Clinical Disorders of Fluid and Electrolyte Metabolism. New York, NY: McGraw-Hill; 1994:213-220.
Naka T, Bellomo R. Bench-to-bedside review: treating acid-base abnormalities in the intensive care unit--the role of renal replacement therapy. Crit Care. Apr 2004;8(2):108-14. [Medline].
Omron EM. Metabolic alkalosis and cystic fibrosis. Chest. Mar 2004;125(3):1169; author reply 1169-70. [Medline].
Palmer BF, Alpern RJ. Metabolic alkalosis. J Am Soc Nephrol. Sep 1997;8(9):1462-9. [Medline].
Shapiro BA, Harrison RA, Cane RD. Clinical application of blood gases. St. Louis, Mo: Mosby; 1989.
Siberry GK, Iannone R. Formulary. In: The Harriet Lane Handbook: A Manual for Pediatric House Officers. St. Louis, Mo: Mosby; 2000:616, 629.
van Thiel RJ, Koopman SR, Takkenberg JJ, Ten Harkel AD, Bogers AJ. Metabolic alkalosis after pediatric cardiac surgery. Eur J Cardiothorac Surg. Aug 2005;28(2):229-33. [Medline].
[Best Evidence] Wiedemann HP, Wheeler AP, Bernard GR, Thompson BT, Hayden D, deBoisblanc B, et al. Comparison of two fluid-management strategies in acute lung injury. N Engl J Med. Jun 15 2006;354(24):2564-75. [Medline].
Wong HR, Chundu KR. Metabolic alkalosis in children undergoing cardiac surgery. Crit Care Med. Jun 1993;21(6):884-7. [Medline].
metabolic alkalosis, plasma bicarbonate, HCO3, acid-base abnormality, metabolic acidosis, chloride-responsive metabolic alkalosis, chloride-resistant metabolic alkalosis, primary aldosteronism, hypoxemia, arteriolar constriction, hypokalemia, vomiting, pyloric stenosis, primary hyperaldosteronism, reninism, hyperglucocorticoidism, Bartter syndrome, deoxycorticosterone excess syndromes, hypertension, hypermineralocorticoid state, cystic fibrosis, primary aldosteronism, Liddle syndrome, anorexia nervosa, hyperglucocorticoidism, milk-alkali syndrome, hypercalcemia, hypochloremia, hyponatremia
Lennox H Huang, MD, Associate Clinical Chair, Assistant Professor, Department of Pediatrics, McMaster University; Deputy Chief of Pediatrics, McMaster Children's Hospital
Lennox H Huang, MD is a member of the following medical societies: American Academy of Pediatrics, Canadian Medical Association, Ontario Medical Association, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.
Margaret A Priestley, MD, Assistant Professor of Clinical Anesthesiology and Critical Care, University of Pennsylvania School of Medicine; Clinical Director, Pediatric Intensive Care Unit, The Children's Hospital of Philadelphia
Margaret A Priestley, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.
G Patricia Cantwell, MD, Associate Clinical Professor, Department of Pediatrics, University of Miami; Director of Pediatric Critical Care Medicine, Miller School of Medicine, Jackson Children's Hospital
G Patricia Cantwell, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Emergency Physicians, American Heart Association, American Trauma Society, National Association of EMS Physicians, Society of Critical Care Medicine, and Wilderness Medical Society
Disclosure: Nothing to disclose.
Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation
Barry J Evans, MD, Assistant Professor of Pediatrics, Temple University Medical School; Director of Pediatric Critical Care and Pulmonology, Associate Chair for Pediatric Education, Temple University Children's Medical Center
Barry J Evans, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Chest Physicians, American Thoracic Society, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.
Mary E Cataletto, MD, Associate Director, Division of Pediatric Pulmonology, Winthrop University Hospital; Professor of Clinical Pediatrics, State University of New York at Stony Brook; Director of Children's Sleep Services, Winthrop University Hospital
Mary E Cataletto, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Chest Physicians
Disclosure: Shering Plough Pharmaceuticals Honoraria Consulting
Timothy E Corden, MD, Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin
Timothy E Corden, MD is a member of the following medical societies: American Academy of Pediatrics, Phi Beta Kappa, Society of Critical Care Medicine, and Wisconsin Medical Society
Disclosure: Nothing to disclose.
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