Lumbar puncture: Technique, indications, contraindications,

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Lumbar puncture: Technique, indications, contraindications,

مشاركةبواسطة دكتور كمال سيد » الأحد يناير 11, 2015 10:01 pm

Lumbar puncture: Technique, indications, contraindications, and complications in adults


Lumbar puncture (LP) is essential or extremely useful in the diagnosis of bacterial, fungal, mycobacterial, and viral CNS infections and, in certain settings, for help in the diagnosis of subarachnoid hemorrhage, CNS malignancies, demyelinating diseases, and Guillain-Barré syndrome.

●LP is a relatively safe procedure, but minor and major complications can occur, including headache, infection, bleeding, cerebral herniation, as well as minor neurologic symptoms such as radicular pain or numbness.
●Meningitis is a relatively rare complication of LP. (See 'Meningitis' above.)
•LP is contraindicated in patients with a suspected spinal epidural abscess.
•Suspected bacteremia is NOT a contraindication to LP.
•We suggest the use of a face mask for diagnostic LP if the procedure is expected to be prolonged or difficult or if the operator has an upper respiratory tract infection.
●Bleeding in the epidural or subdural space following LP may occur in up to 2 percent of patients, primarily in those patients with thrombocytopenia or other bleeding disorders or in those who have received anticoagulant therapy. (See 'Bleeding' above.)
•Antiplatelet therapy with aspirin and nonsteroidal anti-inflammatory agents is NOT clearly associated with an increased risk of bleeding after LP. The bleeding risk associated with thienopyridine derivatives or GP IIb/IIIa-receptor antagonists is unknown. It is reasonable to suspend therapy, when possible, prior to elective LP.
•Anticoagulation therapy is generally suspended, when possible, prior to elective LP.
•We recommend NOT performing an LP in patients with coagulation defects who are actively bleeding, have severe thrombocytopenia (eg, platelet counts <50,000 to 80,000/µL), or an INR >1.4, without correcting the underlying abnormalities.
•When an LP is considered essential in this setting, consultation with a hematologist may provide the best advice for safe correction of the coagulopathy prior to LP.
●Cerebral herniation is a rare, but usually fatal, complication of an LP performed in an individual with increased intracranial pressure (ICP). While routine neuroimaging, usually brain computed tomography (CT), before LP is not indicated in all patients, those with suspected increased intracranial pressure (altered mentation, focal neurologic signs, papilledema, recent seizure, and impaired cellular immunity) should have a CT scan to rule out possible mass lesion and other causes of increased intracranial pressure. (See 'Cerebral herniation' above.)
•Independent of a decision to perform LP, patients with suspected elevated ICP may require urgent interventions to lower ICP. (See "Evaluation and management of elevated intracranial pressure in adults", section on 'Urgent situations'.)
•When the LP is delayed or deferred in a patient with suspected meningitis, it is important to obtain blood cultures and promptly institute antibiotic therapy. (See "Initial therapy and prognosis of bacterial meningitis in adults", section on 'Avoidance of delay'.)


Preparation

— An LP can be performed with the patient in the lateral recumbent position or sitting upright. The lateral recumbent position is preferred because it allows accurate measurement of the opening pressure.

The choice of needle type (cutting versus atraumatic) and bore size can influence the risk of a post-LP headache, but also may increase the technical difficulty of the procedure. This is discussed in detail separately. (See "Post-lumbar puncture headache", section on 'Prevention'.)

The correct level of entry of the spinal needle is most easily determined with the patient sitting upright or standing. The highest points of the iliac crests should be identified visually and confirmed by palpation; a direct line joining these is a guide to the fourth lumbar vertebral body. The spinous processes of L3, L4, and L5, and the interspaces between can usually be directly identified by palpation. The spinal needle can be safely inserted into the subarachnoid space at the L3/4 or L4/5 interspace, since this is well below the termination of the spinal cord.

Correct patient positioning is an important determinant of success in obtaining CSF. The patient is instructed to remain in the fetal position with the neck, back, and limbs held in flexion. The lower lumbar spine should be flexed with the back perfectly perpendicular to the edge of a bed or examining table. The hips and legs should be parallel to each other and perpendicular to the table. Pillows placed under the head and between the knees may improve patient comfort.

The overlying skin should be cleaned with alcohol and a disinfectant such as povidone-iodine or chlorhexidine (0.5 percent in alcohol 70 percent); the antiseptic should be allowed to dry before the procedure is begun. Many product inserts of chlorhexidine-containing solutions warn against use of chlorhexidine prior to lumbar puncture because of a concern that it can cause arachnoiditis. The evidence that it does so is very limited, and many experts believe that chlorhexidine has an advantage over povidone-iodine because of its onset, efficacy, and potency [2-6]. Due to specific labeling prohibiting use, a formal institutional policy to support such use may be indicated. After the skin is cleaned and allowed to dry, a sterile drape with an opening over the lumbar spine is placed on the patient. Local anesthesia (eg, lidocaine) is infiltrated into the previously identified lumbar intervertebral space and a 20 or 22 gauge spinal needle containing a stylet is inserted into the lumbar intervertebral space.


Procedure technique

— The spinal needle may be advanced slowly, angling slightly toward the head, as if aiming towards the umbilicus. The flat surface of the bevel of the needle should be positioned to face the patient's flanks to allow the needle to spread rather than cut the dural sac (the fibers of which run parallel to the spinal axis). Many physicians choose to advance the needle incrementally, removing the stylet periodically to check for CSF flow, then reinserting the stylet until the subarachnoid space is entered [7]. However, others report a higher rate of successful LP when the stylet is removed, just after the skin is punctured and before it is passed into the subarachnoid space in order to better observe the flow of CSF upon entry of the subarachnoid space [8,9].

Once CSF appears and begins to flow through the needle, the patient should be instructed to slowly straighten or extend the legs to allow free flow of CSF within the subarachnoid space. A manometer should then be placed over the hub of the needle and the opening pressure should be measured (figure 1). Fluid is then serially collected in sterile plastic tubes. A total of 8 to 15 mL of CSF is typically removed during routine LP. However, when special studies are required, such as cytology or cultures for organisms that grow less readily (eg, fungi or mycobacteria), 40 mL of fluid can safely be removed. Aspiration of CSF should not be attempted as it may increase the risk of bleeding [7]. The stylet should be replaced before the spinal needle is removed

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