Page 263 - Critical Care Nursing Demystified

248 CRITICAL CARE NURSING DeMYSTIFIED

to rupture. An AVM can also cause chronic ischemia and cerebral atrophy
because of the abnormal blood flow, which is directed away from normal blood
circulation.

Hallmark Signs and Symptoms
An unruptured AVM may only reveal symptoms of headache, dizziness or even
syncope.
With an SAH, the patient may have had what are described as “warning
leaks,” such as sudden onset of headaches and vomiting several weeks prior to
experiencing a major SAH. With a warning leak, small amounts of blood will
ooze from a cerebral aneurysm into the subarachnoid space. The blood irritates
the meninges causing headache, stiff neck, and photophobia. However, the
patient does not seek medical advice believing the symptoms to be temporary
and not especially severe.

Interpreting Test Results
Diagnosis of the cause of the SAH, an aneurysm, or an AVM is made by CAT
scan, patient symptoms and a lumbar puncture. A CAT scan will detect
bleeding or a clot in the subarachnoid space where an MRI cannot. If, and 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.
only if, the CAT scan is negative will a spinal tap be done to measure the CSF
for RBCs. The CSF will be bloody in appearance after an SAH and the RBC
count will be greater than 1000 mm. Once diagnosed, a cerebral angiogram
is indicated to identify the cause of the SAH. Surgery may be done to control
the bleed. The decision to operate depends on the size and location of the
problem, which can be so deep in the cerebral structures that attempts at
removal could create even more severe neurological deficits. The patient’s
age, overall condition, and history of prior hemorrhage and injuries are all
considered when deciding whether or not to operate. If surgery does occur,
a craniotomy is performed to expose and locate the area of the aneurysm or
an AVM.
If the problem is an aneurysm, a surgical clip is placed over its neck or stem
to isolate it and eliminate and completely destroy the weak area. It is recom-
mended that surgery take place within the first 48 hours after rupture. SAH
patients who are within the Grade 1 or 2 categories of the Hunt and Hess Clas-
sification System of Subarachnoid Hemorrhage have a better postoperative
outcome as compared to the more serious grades on the scale.
A description of the Hunt and Hess Classification System of Subarachnoid
Hemorrhage is as follows: