A lumber puncture ( spinal tap ) is carried out by inserting a needle into the lumber subarachnoid space ( beneath the middle layer of the membrane surrounding the spinal cord ) .
- The needle is inserted into the subarachnoid space between the 3rd and 4th lumber interspace .
The needle is inserted below the level of the 3rd lumber vertebra to prevent the spinal from being punctured .
Purposes of lumber puncture :
- This needle is inserted in order to withdraw cerebrospinal fluid for diagnostic and therapeutic purposes .
Diagnostic Lumber Puncture
1. To measure pressure of CSF within ( brain , spinal cord tumor , infection )
2. To determine the presence or absence of blood in the spinal fluid .
3.To detect spinal subarachnoid block .
4. CSF withdrawn before instilling contrast medium for X-rays of the spinal column.
Therapeutic Lumber Puncture
1.To instill some drugs after withdrawal of a similar amount .
2.To administer antibiotics intrathecally in some cases of infection .
Lumber Puncture Contraindications :
- Signs of cerebral herniation .
- Previous lumber surgery .
- Cardiorespiratory compromise .
- The normal range of spinal fluid pressure with the patient in lateral recumbent position is : 70 – 200 mm H2O
- A successful lumber puncture require that the patient be relaxed , since an anxious patient may become tense , causing an increase in the pressure reading .
Nursing Role in lumber puncture :
1- During explanations, the client should be assured that inserting a needle into the spine will not result in paralysis .
2- Ensure that the client has signed the consent form , if needed .
3- Perform a basic neurological examination including pupil size and response & muscle strength & sensation in all four extremities , this provide a baseline for future comparisons .
4- Prior to LP, encourage the client to empty bladder to promote comfort .
5- Administer a sedative drug if ordered to reduce anxiety .
6- Obtain a prepackage LP kit with a local anesthetic .
7- Gather equipments
• Extra gloves
• Collection tubes
• Manometer ( if needed )
• Styletted spinal needles