Lumbar puncture

Key points

The rachicentesi (lumbar puncture) is a medical-surgical practice which consists in collecting a sample of cerebrospinal fluid by introducing a needle between the L3-L4 or L4-L5 vertebrae.

Goals of rachicentesi

• Diagnostic purposes of rachicentesi: ascertainment of brain infections (eg meningitis), demyelinating pathologies (eg multiple sclerosis), neoplasms, epilepsy.
• Therapeutic purpose of rachicentesis: reduction of intracranial pressure and administration of medicines (eg chemotherapy / spinal anesthesia)

Contraindications of rachicentesi

Lumbar puncture must NOT be performed in the case of: sepsis, cerebral hernia, IDIOPATHIC intracranial hypertension, hemorrhagic diathesis, vertebral deformity, hypertension with bradycardia

Execution of the rachicentesi

• Preparation of the sterile field (disinfection of the skin with iodine-based antiseptic substances)
• Performing local anesthesia
• Introduction of the lumbar puncture needle between the intravertebral spaces L3-L4 or L4-L5
• Collection of a liquor sample
• Removal of the needle from rachicentesi
• Cleaning of the area

Post-rachicent complications

• Mild: headache (+ nausea / vomiting / dizziness), lower back pain, temporary paresthesia
• Severe: anesthetic toxicity, bleeding, bleeding in the epidural space, epidural abscess, descent of the cerebellar tonsils, severe thrombocytopenia

Definition of rachicentesi

The rachicentesi - or lumbar puncture - is a surgical strategy performed to extract a sample of cerebrospinal fluid (CSF or CSF, the fluid that surrounds and protects the brain and spinal cord).

The rachicentesi consists in the introduction of a needle between the third / fourth or fourth / fifth lumbar vertebra: having reached the subarachnoid space (between arachnoid and pia mater), one proceeds with the collection of a liquid sample.

In this informative article we will shed light on some frequent questions concerning the rachicentesi:

• What is the purpose of lumbar puncture?
• What are the contraindications?
• What is the surgical procedure? Is it painful?
• What complications / problems do patients undergo rachicentesi?
• How are the results of the rachicentesi interpreted?

Purposes

The lumbar puncture is performed for diagnostic or therapeutic purposes:

1. RACHICENTESI DIAGNOSTICA: the objective is to collect a sample of liquor to verify an eventual infectious-inflammatory process on the brain (eg encephalitis, meningitis, Guillain Barre syndrome, etc.). The diagnostic rachicentesi is also performed to ascertain or not the presence of demyelinating pathologies (eg multiple sclerosis) and for the search for neoplastic cells (oncological screening). The lumbar puncture is also performed to ascertain or deny a possible epileptic state (especially after a "suspicious" convulsion).
2. THERAPEUTIC RACHYCENTESIS: indicated to reduce the intracranial pressure in the case of hydrocephalus (accumulation of liquor in the cavities - or ventricles - cerebral) or to administer medicines directly within the sub-arachnoid space (eg spinal anesthesia, chemotherapy).

Contraindications

The rachicentesi cannot be performed in some particular circumstances, listed below:

• Lumbar skin infection: rachicentesis can promote the spread of infection
• Sepsis
• Suspected or ascertained cerebral hernia
• Degenerative joint disease
• Idiopathic intracranial hypertension: rachicentesi is strongly discouraged when it is not possible to trace the cause of the aforementioned hypertension. Let us briefly recall that complicated intracranial hypertension may be associated with cerebral hernia
• Respiratory disorders: hyperventilation, apneas, respiratory arrest
• Hemorrhagic diathesis: Coagulopathy or Thrombocytopenia
• Hypertension associated with bradycardia and altered consciousness
• Vertebral deformities (eg scoliosis, kyphosis)

The rachicentesi should not be performed if the patient does not cooperate: in similar situations, the subject should be slightly sedated.

execution

The rachicentesi is performed as an outpatient procedure: it takes a few minutes and is performed under local anesthesia.

BEFORE THE RACHICENTESI

Before proceeding with the lumbar puncture, the medical team must prepare all the necessary equipment for the operation: lumbar puncture needle, 5-10 ml syringes, local anesthetic, antiseptic, sterile gloves / gauze / drapes, intramuscular needles for local anesthetic etc ..

Before the rachicenthesis, the doctor investigates the patient's clinical history (anamnesis); it is recommended to perform blood tests in order to check for any bleeding or other circulation disorders. The doctor sometimes prescribes a CT scan for the patient to ascertain the absence of swelling or brain abnormalities. The patient is obliged to inform the doctor in case of anticoagulant therapy (eg warfarin, clopidogrel, aspirin etc.). A possible allergy to local anesthetic drugs should also be reported to the doctor.

The patient must then sign a form in which he declares to have been informed of the purpose, methods and possible risks of the intervention, giving his consent to the execution of the procedure.

DURING RACHICENTESI

The lumbar puncture can be performed in lateral decubitus position (positioning the patient in fetal position, with arms and legs collected), or in a sitting position, with the back bent forward and the elbows resting on a pillow. The patient must be relaxed and must NOT move during the procedure: abrupt movements can in fact cause the needle to break!

Even the doctor must assume a comfortable and safe posture: in this way he can perform the necessary maneuvers in total safety. Once the patient has been positioned correctly, it is possible to begin the rachetic period. The surgical procedure is described below by points:

• Preparation of the sterile field : the skin - near the point where the lumbar puncture is performed - should be disinfected with an antiseptic solution (generally iodine-based).
• Performing local anesthesia (1% lidocaine) using a very fine needle: it is necessary to wait a few moments before practicing the rachicentesis, to allow the anesthetic to exert its therapeutic effect.
• Introduction of the lumbar puncture needle between the intravertebral spaces L3-L4 or L4-L5, until reaching the sub-arachnoid space. At these levels we operate in total safety: it is almost impossible to cause lesions to the marrow structures (normally extended up to the upper margin of the second lumbar vertebra). The insertion of the needle may favor a particular tingling sensation: it is necessary to inform the patient of this possibility, to avoid agitation and concern that could complicate the procedure.

The attainment of the sub arachnoid space is identified by two very important elements: the sudden cessation of needle resistance and the emission of the liquor

• (Possible) measurement of intracranial pressure using the Claude pressure gauge
• Collection of a liquor sample: the cerebrospinal fluid must NOT be aspirated, rather the collection must take place by collecting the drops coming out of the needle. In doing so, we avoid subjecting the sub-arachnoid space to negative pressure; otherwise, the patient complains of nausea and headache. Usually, three sample tubes are collected, useful for the biochemical study, for microbiological analysis and for cell research.
• Removal of the needle from rachicentesi.
• Apply light pressure with sterile gauze directly to the puncture site.
• Cleaning of the area with a physiological solution and application of an antiseptic substance, essential to remove blood residues and avoid contamination of the area.
• Application of a medicated plaster at the needle insertion point.

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After the rachicentesi

It is not uncommon for the patient to complain about headache at the end of the procedure: in this case, an analgesic can be administered. After collection, the patient must remain in the supine position for a few hours (usually 2 or 3 hours is sufficient) to monitor the clinical conditions. The patient is asked to take substantial amounts of water after the lumbar puncture: the forced intake of liquids restores the level of the liquor.

Neither forced hyperhydration, nor the maintenance of the supine position have proved to be effective strategies to escape the typical side effects (headache) post-rachicentesi.

Rachicentesi: complications and results »