Monitoring

Neurologic monitoring techniques are discussed in Chapter 38 . Invasive monitoring is frequently appropriate in neurosurgery. Some of the numerous indications for an arterial catheter are listed in Table 53-7 .

Patients with increased ICP may be intolerant of the vascular engorgement associated with sudden hypertension occurring as a consequence of light anesthesia. Surgical relief of increased ICP may be associated with sudden hypotension as brainstem compression is relieved. Beat-by-beat arterial pressure monitoring also serves as an important depth-of-anesthesia monitor and as an early warning system for neurologic injury. Much of the brain is insensate. As a consequence, the intracranial portion of many neurosurgical procedures is not very stimulating, and to achieve circulatory stability, relatively light anesthesia is often necessary. There should be constant attention to the possibility of sudden arousal (most often associated with cranial nerve traction or irritation), especially when paralysis is precluded by the use of electromyographic recording of facial muscles to monitor cranial nerve integrity. Blood pressure responses may reveal imminent arousal. They may also serve to warn a surgeon of excessive or unrecognized irritation, traction, or compression of neurologic tissue. These problems occur most often with posterior fossa procedures involving the brainstem or cranial nerves, and abrupt changes should be reported to the surgeon immediately.

The use of right heart catheters for air retrieval is discussed in the section "Venous Air Embolism." Thereafter, anticipated blood loss and fluid flux (including aggressive mannitol use) and an evaluation of the patient's physiologic reserve should determine the necessity for CVP or pulmonary artery catheters. The use of precordial Doppler is also described in the section "Venous Air Embolism."

2143