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Introduction ⬇

Glutamine, an amino acid, is synthesized in brain tissue from ammonia and alpha-ketoglutarate. Production of glutamine, the most prominent amino acid in CSF, provides a mechanism for removing the ammonia, a toxic metabolic waste product, from the CNS.

The determination of CSF glutamine level provides an indirect test for the presence of excess ammonia in the CSF. As the concentration of ammonia in the CSF increases, the supply of alpha-ketoglutarate becomes depleted; consequently, glutamine can no longer be produced to remove the toxic ammonia, and coma ensues. A CSF glutamine test is therefore frequently requested for patients with coma of unknown origin.

Normal Findings ⬆ ⬇

8.6 ± 0.50 mg/dL or 0.60 ± 0.03 mmol/L or 590 ± 34 μmol/L

Clinical Alert

A CSF glutamine value >35 mg/dL (>2.4 mmol/L) usually results in loss of consciousness

Procedure ⬆ ⬇

  1. A lumbar puncture is performed (see Lumbar Puncture [Spinal Tap]).

  2. Use 1 mL of CSF for the glutamine test in a sterile screw-top tube.

  3. Centrifuge the samples if cells are present.

Clinical Implications ⬆ ⬇

Increased CSF glutamine levels are associated with the following conditions:

  1. Hepatic encephalopathy (glutamine values >35 mg/dL or >2.4 mmol/L are diagnostic)

  2. Reye syndrome (typically affects the brain and liver of children after a viral infection)

  3. Encephalopathy secondary to hypercapnia or sepsis

  4. Bacterial meningitis

Interventions ⬆

Pretest Patient Care

  1. Follow pretest patient care for lumbar puncture (see Lumbar Puncture [Spinal Tap]).

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

Posttest Patient Care

  1. Review abnormal glutamine levels; report and record findings. Modify the nursing care plan as needed to prevent complications. Correlate with clinical symptoms.

  2. Follow posttest patient care for lumbar puncture (see Lumbar Puncture [Spinal Tap]).

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