Page 247 - Critical Care Nursing Demystified

232 CRITICAL CARE NURSING DeMYSTIFIED

NURSING ALERT

Nurses must make sure that efforts are taken to stabilize the cervical spine or neck
of the spinal-cord-injured patient by using a hard cervical collar and logrolling the
patient during testing.

Spinal Tap or Lumbar Puncture
This is an invasive procedure done to detect blood in the cerebrospinal fluid and
to assess for infection or autoimmune disorders. After skin preparation and provid-
ing a local anesthetic, a sterile needle is inserted into the subarachnoid space at the
L3-4 or L4-5 vertebral level. Ten milliliters of obtained fluid is analyzed for culture
and sensitivity, cell counts, chemistry, and microbiologic examination. CSF pres-
sure readings are also obtained. Remember that normal CSF pressure is 70 to
200 mm H O. Also, one-half to 1 hour prior to a spinal tap, a blood glucose sample
2
is drawn and used as a comparison with the CSF glucose level of 50 to 75 mg/dL
or 60% of serum levels. Patient positioning for a spinal tap is very important to
allow for the maximum separation of the vertebrae. Patients are positioned on
their sides, curled up into a ball with their head and feet as close to each other as Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
possible. In other words, the patient assumes the fetal position.
Complications from a spinal tap include a post-procedure headache that can
last for 24 hours or longer, nuchal rigidity, fever, and dysuria. The patient may
be instructed to remain flat in bed for a few hours post procedure to prevent
spinal headaches. Further treatment includes the injection of a “blood patch” or
blood into the dura mater to stop the CSF leak.

NURSING ALERT
If an increase in ICP is suspected, an LP is not done because a quick reduction of CSF
pressure in the spinal column can cause a herniation of the brainstem into the fora-

men magnum. Remember that spinal fluid is formed in the lateral ventricles of the
brain. The fluid bathes the brain, meninges, and spinal cord and protects the CNS

from injury.

Magnetic Resonance Imaging (MRI)

An MRI produces computerized cross-sectional images of finely detailed ana-
tomical slices of the body. It is most useful in the early diagnosis of cerebral
infarction, multiple sclerosis, and tumors and hemorrhages that might not
be identified on CAT scan. The use of an MRI is limited in that it cannot be