H Posterior fossa procedures
Neuropathology within the posterior fossa may impair control of the airway, respiratory function, cardiovascular function, autonomic function, and consciousness. The major motor and sensory pathways, primary cardiovascular and respiratory centers, reticular activating system, and nuclei of the lower cranial nerves are all concentrated in the brainstem. All of these vital structures are contained in a tight space with little room for accommodating edema, tumor, or blood.
2. Preoperative assessment and patient preparation
a) History and physical examination
(1) Neurologic: The history and physical examination should include a thorough neurologic evaluation with documentation. Pay special attention to signs and symptoms of brainstem involvement, such as focal neurologic deficits, depressed respiration, and cranial nerve palsies. Changes in level of consciousness may be secondary to increased ICP resulting in headaches, nausea, vomiting, visual changes, and seizures from obstructive hydrocephalus of the fourth ventricle.
(2) Cardiovascular: Evaluate for cardiovascular disease and hypertension. Increased ICP may result in brainstem herniation and manifest as Cushing triad (hypertension and irregular respirations).
(5) Gastrointestinal: Infratentorial tumors may involve the glossopharyngeal and vagus nerves. This may impair the gag reflex, increasing the chance for aspiration.
b) Laboratory tests: CBC, electrolytes, blood urea nitrogen, creatinine, glucose, prothrombin time, and partial thromboplastin time are obtained.
d) Preoperative medications: Anxiolytics may be given to alert and anxious patients. Patients who are lethargic or have an altered level of consciousness should not receive premedication.
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