The source of CSF lactic acid (L-lactate) is CNS anaerobic metabolism. Lactic acid in CSF varies independently with the level of lactic acid in the blood. Destruction of tissue within the CNS because of oxygen deprivation causes the production of increased CSF lactic acid levels. Thus, elevated CSF lactic acid levels can result from any condition that decreases the flow of oxygen to brain tissues.
The CSF lactic acid test is used to differentiate between bacterial and nonbacterial meningitis. Elevated CSF lactate levels are not limited to meningitis and can result from any condition that decreases the flow of oxygen to the brain. CSF lactate levels are frequently used to monitor severe head injuries.
Adult: 10–22 mg/dL or 1.1–2.4 mmol/L
Newborn: 10–25 mg/dL or 1.1–2.8 mmol/L
Increased CSF lactic acid levels are associated with the following conditions:
Bacterial meningitis
Brain abscess or tumor
Cerebral ischemia
Cerebral trauma
Seizures
Stroke
Increased ICP
Pretest Patient Care
Follow pretest patient care for lumbar puncture (see Lumbar Puncture [Spinal Tap]).
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test outcomes; report and record findings. Modify the nursing care plan as needed to detect CNS disease and prevent complications.
Follow posttest patient care for lumbar puncture (see Lumbar Puncture [Spinal Tap]).
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
Clinical Alert
Increases in CSF lactic acid levels must be interpreted in light of the clinical findings and in conjunction with glucose levels, protein levels, and cell counts in the CSF. Equivocal results in some instances of aseptic meningitis may lead to erroneous diagnosis of a bacterial etiology. Increased lactate in CSF following head injury suggests poor prognosis
Traumatic tap causes elevated levels: RBCs contain large amounts of lactate. Hemolyzed or xanthochromic specimens will give falsely elevated results.