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Introduction ⬇

Lactic acid is produced during periods of anaerobic metabolism when cells do not receive adequate oxygen to allow conversion of fuel sources to CO2 and water. Lactic acid is a weak acid that partially dissociates in water, resulting in production of lactate and hydrogen ions. Lactic acid accumulates because of excess production of lactate and decreased removal of lactic acid from blood by the liver. Measuring lactic acid is common in cases of suspected septic shock.

This measurement contributes to the knowledge of acid–base volume and is used to detect lactic acidosis in persons with underlying risk factors such as cardiovascular or kidney disease that predispose them to this imbalance. Lactic acid is elevated in a variety of conditions in which hypoxia occurs due to shock or vascular occlusion and in liver disease. Lactic acidosis can occur in both patients with diabetes and without diabetes. Elevated lactic acid levels can be fatal.

Procedure ⬆ ⬇

  1. Obtain a venous or arterial blood sample of at least 5 mL. (See Chapter 2 for venous and arterial blood collection.)

  2. Label specimen with the patient’s name, date, and test(s) ordered. Take the specimen to the laboratory immediately for analysis.

Clinical Implications ⬆ ⬇

  1. Values are increased with:

    1. Medications, such as metformin

    2. Sepsis

    3. Cardiac arrest

    4. Pulmonary failure (sometimes defined as a PaO2<50 mm Hg [<6.7 kPa] and a PaCO2 >50 mm Hg [>6.7 kPa])

    5. Hemorrhage

    6. Diabetes

    7. Shock

    8. Liver disease; alcoholism

    9. Ischemic tissue; trauma

  2. Lactic acidosis can be distinguished from ketoacidosis by the absence of severe ketosis and hyperglycemia in this state.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain the purpose and procedure of arterial blood sampling. Assess patient cooperation.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Frequently observe the puncture site for bleeding. Manual pressure and a pressure dressing should be applied to the puncture site if necessary.

  2. Base posttest assessments on patient outcomes; monitor and intervene appropriately for ventilatory and acid–base disturbances and hypoxemia.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆ ⬇

Lactic acid levels normally rise during strenuous exercise, when blood flow and oxygen cannot keep pace with the increased needs of exercising muscle.

Clinical Alert

An unexplained decrease in pH associated with a hypoxia-producing condition is the reason to suspect lactic acidosis

Reference Values ⬆

Normal