Cerebrospinal fluid analysis

Cerebrospinal fluid (CSF) examination is the main method of diagnostics, differential diagnostics and evaluation of the effectiveness of treatment of infectious diseases of the central nervous system (CNS). Cerebrospinal fluid for examination is obtained by puncturing the subarachnoid space of the spinal cord (spinal puncture).

Indications for cerebrospinal fluid analysis

• Suspected infectious disease of the central nervous system.
• Evaluation of the effectiveness of her treatment.
• Endolumbar administration of antibiotics and other drugs.

Contraindications to cerebrospinal fluid analysis

Contraindications for spinal puncture: disruption of vital functions, convulsive syndrome. In these cases, spinal puncture is performed after restoration of hemodynamics, breathing or transfer of the patient to artificial lung ventilation (ALV), seizures relief. Considering the exceptional importance of studying the cerebrospinal fluid for providing effective care to the patient, in case of relative contraindications (suspected volumetric process, brain dislocation), in doubtful cases, the cerebrospinal fluid should be removed in separate drops, without removing the mandrin from the lumen of the needle, in a volume of no more than 2.0 ml.

Preparing for the study

A routine examination is carried out in the morning on an empty stomach; in emergency cases, it is carried out at any time of the day.

Research methodology

A spinal puncture is performed with a special puncture needle (Vira needle) with a diameter of 1.0 and 1.2 mm, a length of 60, 90 and 120 mm, with a bevel angle of 45° and a cone-shaped needle head channel, which allows for easy insertion and withdrawal of the mandrin into the lumen of the needle. A spinal puncture is performed with the patient lying strictly on his side with his legs tucked up to his stomach and his head bent. The puncture site is marked with a longitudinal line applied with iodine solution along the spinous processes of the vertebrae from top to bottom, and a transverse line connecting the iliac crests. The place of their intersection corresponds to the space between the vertebrae L3 _and L4 _- the most convenient for a spinal puncture (puncture is allowed between L4 _and L5 _and between L2 _and L3 ₎. Then the skin around the proposed puncture site is carefully treated with iodine within a radius of 5 cm and with alcohol within a radius of 4 cm. In patients with acutely developed neurological symptoms, the puncture is performed without anesthesia. If necessary, the skin and subcutaneous tissue is anesthetized with a 1-2% solution of novocaine. An additional landmark for specifying the puncture site is the protruding spinous process of L ₄, which is fixed with the thumb of the left hand. The needle is inserted close to the finger, with a slight backward tilt (30 °), strictly along the midline until a “failure” is felt when puncturing the dura mater. After this, the mandrin is slowly removed from the lumen of the needle (do not allow the cerebrospinal fluid to flow out in a stream!), the pressure of the cerebrospinal fluid is measured and it is collected for research. After the puncture, the patient should lie horizontally on his back without a pillow for 2 hours.

Mistakes in performing a spinal puncture

Due to the incorrect position of the patient (torso tilt, pelvic rotation), the needle passes by the vertebra and does not enter the spinal canal. In this case, it is necessary to check the correct position of the patient.

Due to incorrect tilt, the needle rests against the vertebral body. It is necessary to check the correctness of the determination of landmarks and the tilt of the needle and, having pulled the needle outward by 2-3 cm, repeat the puncture.

If there is no sensation of the needle “failing” and it rests against the anterior wall of the spinal canal, pull the needle back 1 cm and remove the mandrin from the lumen of the needle.

In rare cases, even if the puncture is technically correct, it is not possible to obtain cerebrospinal fluid due to the high viscosity of the fluid or severe cerebrospinal fluid hypotension. In this case, you can try to obtain fluid by gentle suction with a syringe.

Complications during spinal puncture

• Traumatization of the vascular plexus of the anterior wall of the spinal canal. In this case, the first drops of blood in the cerebrospinal fluid ("travel blood") appear.
• Touching the spinal nerve root (cauda equina) hanging into the lumen of the canal with a needle. In this case, a reflex contraction of the muscles of the lower limb occurs, the patient experiences a sensation of "electric shock".
• Convulsions and respiratory failure due to brain dislocation are extremely rare.

In the first two cases, no special measures are required. In the latter case, it is necessary to inject 5-15 ml of sterile isotonic sodium chloride solution into the spinal canal, remove the needle, and lay the patient on his back with the head end lowered. If there is no effect, administer emergency therapy (artificial ventilation, anticonvulsants).

After performing a spinal puncture

• Liquorrhea.
• Post-puncture syndrome (headache, dizziness, nausea, vomiting).

In case of liquorrhea, it is enough to apply a pressure bandage. In case of post-puncture syndrome, bed rest, plenty of fluids, drip administration of 0.5 l of polyionic solution should be prescribed, and any diuretics should be avoided.

Taking cerebrospinal fluid for examination

Cerebrospinal fluid for examination is collected in three test tubes: 2 ml - for general analysis, 2 ml - for biochemical analysis, 1 ml - for bacteriological examination in a sterile test tube. Two or three drops of liquid for bacteriological examination are applied to a Petri dish with a nutrient medium (chocolate agar with polivitex) and two or three drops are added to a test tube with semi-liquid 0.01% agar.

It is also recommended to collect 1-2 ml of cerebrospinal fluid in a reserve sterile tube. Before transportation to the laboratory, cerebrospinal fluid for general and biochemical studies is stored in a household refrigerator, and for microbiological studies - in a thermostat at a temperature of 37 ° C. Transportation of cerebrospinal fluid for these purposes must be carried out at the same temperature, using thermocouples if necessary.

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