From the Guidelines
A lumbar puncture is safe at an International Normalized Ratio (INR) of less than 1.5.
Safe INR for Lumbar Puncture
- The UK Joint Specialist Societies guideline on the diagnosis and management of acute meningitis and meningococcal sepsis in immunocompetent adults recommends that an LP should not be routinely performed at an INR of 1.5 1.
- This guideline suggests that the risks of reversing warfarin should be weighed against the benefits of performing an LP, implying that an INR below 1.5 is considered safe.
- It is essential to note that the decision to perform an LP should be made on a case-by-case basis, taking into account the individual patient's risk factors and the potential benefits of the procedure.
- In patients on warfarin, the benefits of performing an LP should be carefully weighed against the risks of reversing anticoagulation, and alternative diagnostic methods should be considered if possible 1.
From the Research
Safety of Lumbar Puncture and INR Levels
The safety of performing a lumbar puncture (spinal tap) is a concern in patients with coagulopathy, including those with elevated International Normalized Ratio (INR) levels.
- A study published in JAMA in 2020 2 defined coagulopathy as an INR greater than 1.4, among other factors, and found that the risk of spinal hematoma after lumbar puncture was 0.20% in patients without coagulopathy and 0.23% in those with coagulopathy.
- The same study found that traumatic lumbar punctures occurred more frequently among patients with INR levels of 1.5 to 2.0,2.1 to 2.5, and 2.6 to 3.0 compared to those with normal INR levels.
Reversal of Anticoagulation for Lumbar Puncture
In patients receiving vitamin K antagonists, such as warfarin, reversal of anticoagulation may be necessary to perform a lumbar puncture safely.
- A study published in the Annals of Emergency Medicine in 2016 3 found that treatment with prothrombin complex concentrate was effective in reversing vitamin K antagonist therapy and enabling emergency lumbar puncture, with a target INR of less than or equal to 1.5.
- Another study published in the American Journal of Health-System Pharmacy in 2015 4 reported the use of low-dose prothrombin complex concentrate to reverse an INR from 1.7 to 1.3 in a patient before a diagnostic lumbar puncture.
General Guidelines for Lumbar Puncture
While there is no specific INR level universally agreed upon for the safety of lumbar puncture, the general guidelines suggest that an INR of 1.5 or less is considered safe for the procedure.
- A study published in Postgraduate Medicine in 1986 5 stated that lumbar puncture is a safe and simple procedure with little risk of major complication if proper technique and indications are followed, but did not provide specific guidance on INR levels.
- A plain language summary published in Neurodegenerative Disease Management in 2022 6 discussed the safety of lumbar puncture in patients with Alzheimer's disease, but did not provide specific guidance on INR levels.