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  1. Compare and contrast the pathophysiology, clinical presentation, patient needs, and management approaches for the following conditions:

    • Subarachnoid hemorrhage

    • Traumatic brain injury

    • Acute spinal cord injury

    • Brain tumor

  2. Describe the concept of cerebral oxygenation and brain tissue oxygen monitoring.


Etiology, Risk Factors, and Pathophysiology

Subarachnoid hemorrhage (SAH) can result from trauma, aneurysm, or other vascular malformations. This discussion focuses on SAH due to the rupture of an intracranial aneurysm. Intracranial aneurysms usually occur in the circle of Willis at arterial bifurcations or trifurcations (Figure 21-1). Aneurysms vary in size and shape; saccular (also called berry) aneurysms are the most common and most amenable to treatment. When an intracranial aneurysm ruptures, blood is expelled. The blood takes the path of least resistance, which most often is into the subarachnoid space. Subsequently, a clot may form in the ventricular system or in the brain parenchyma. In some patients, blood in the subarachnoid space causes hydrocephalus by obstructing cerebrospinal fluid (CSF) flow through the ventricles or clogging the arachnoid granulations (or arachnoid villi) that reabsorb CSF. Although the mechanism is not well understood, arterial narrowing, commonly referred to as “vasospasm” or “cerebral artery vasospasm,” occurs in a significant number of patients in the days following aneurysm rupture and can cause delayed cerebral ischemia (DCI) or delayed ischemic neurological deficit (DIND). There are several scales used to grade the severity of aneurysmal subarachnoid hemorrhage (aSAH). The Hunt and Hess scale and World Federation of Neurological Surgeons (WFNS) scale (Table 21-1) are most commonly used.

Figure 21-1.

The circle of Willis as seen from below the brain. (Reproduced with permission from Phipps WJ, Marek JF, Monahan FD, et al. Medical-Surgical Nursing: Health and Illness Perspectives. St Louis, MO: Mosby; 2003.)


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