From the Guidelines
Neither lactic acid levels nor sedimentation rate should solely determine the decision to perform a spinal tap, as the decision should be based on a comprehensive clinical assessment, including patient presentation, physical examination findings, and other diagnostic results, as suggested by the guidelines from the UK joint specialist societies 1. When considering a spinal tap, it is crucial to evaluate the patient's overall clinical condition, including any contraindications such as local skin sepsis, clinically unstable patient, suspicion of spinal cord compression, or coagulopathy, as outlined in the management of suspected viral encephalitis in adults 1.
- Key factors influencing the decision include:
- Clinical presentation and physical examination findings
- Results from other laboratory tests and imaging studies when appropriate
- Presence of contraindications to lumbar puncture
- Patient's coagulation status, including platelet count and use of anticoagulant medications The guidelines recommend that a lumbar puncture should not be delayed to await the results of blood tests unless there is a strong suspicion of a clotting abnormality, and the decision to perform the procedure should be reviewed regularly if initially delayed 1.
- In patients with abnormal clotting or on anticoagulant therapy, specific precautions and considerations must be taken into account, such as the timing of the last dose of low molecular weight heparin (LMWH) or the use of reversal agents for newer oral anticoagulants, as discussed in the guideline on the diagnosis and management of acute meningitis and meningococcal sepsis in immunocompetent adults 1. Ultimately, clinical judgment plays a critical role in deciding whether to perform a spinal tap, taking into account the potential benefits and risks of the procedure in the context of the individual patient's condition, as emphasized by the need for a case-by-case assessment 1.
From the Research
Decision to Perform a Spinal Tap
The decision to perform a spinal tap, also known as a lumbar puncture, is based on various factors, including the patient's symptoms, medical history, and laboratory results.
- Lactic acid levels in cerebrospinal fluid (CSF) can be an indicator of certain conditions, such as bacterial meningitis 2.
- However, there is no direct evidence to suggest that lactic acid levels alone affect the decision to perform a spinal tap.
- Sedimentation rate, which is a measure of the rate at which red blood cells settle in a test tube, is not typically a factor in deciding whether to perform a spinal tap 3, 4.
- The presence of blood in the CSF, which can be indicated by a high red blood cell count, can be a factor in deciding whether to perform a spinal tap, as it may suggest a subarachnoid hemorrhage or traumatic tap 5.
- Other factors, such as the patient's symptoms, medical history, and results of other laboratory tests, are also taken into account when deciding whether to perform a spinal tap 6.
Laboratory Tests and Spinal Tap Decision
Laboratory tests, such as CSF analysis, can provide valuable information to help guide the decision to perform a spinal tap.
- CSF lactate dehydrogenase level can be used to differentiate between subarachnoid hemorrhage and traumatic tap 5.
- Other CSF markers, such as procalcitonin, lactate, and lactate ratio, can be used to diagnose bacterial meningitis in blood-contaminated CSF 2.
- The results of these laboratory tests, along with other factors, can help inform the decision to perform a spinal tap.