Koji Mii

Sequential changes of auditory brain stem responses in relation to intracranial and cerebral perfusion pressure and initiation of secondary brain stem damage

SummaryThe relationship of supratentorial intracranial pressure (ICP) and cerebral perfusion pressure (CCP) with serial changes in auditory evoked brain stem responses was investigated. Eighty-one patients without primary brain stem damage admitted to our emergency unit were studied. When ICP over 50 mm Hg persisted for 4 hours, the I–V interpeak latency was significantly prolonged. The threshold of this prolongation was 8 hours for the ICP over 45 mm Hg and 24 hours for that of over 40 mm Hg. The ICP of 35–40 mm Hg for 24 hours was the border zone. CCP did not show a significant relation with I–V interpeak latency changes. The loss of wave V was observed in a wide range of the ICP (30–147 mm Hg) and CPP (0–60 mm Hg). Wave III disappeared when the ICP exceeded 50 mm Hg. Wave I became undetectable with an ICP above 50 mm Hg or a CPP below 40 mm Hg.These results indicate that an increase of ICP over 40 mm Hg definitely initiates secondary brainstem dysfunction if it lasts for more than 24 hours and that the ICP should be reduced below this level, preferably below 35 mm Hg, to maintain brain function. The fact that both low CPP and high ICP were involved in the loss of wave I clearly shows that both ischaemia and displacement of the brain stem are the important pathophysiological factors for the disappearance of wave I.

The Relationship Between Intracranial Pressure, Cerebral Perfusion Pressure and Outcome in Head-Injured Patients: The Critical Level of Cerebral Perfusion Pressure

In the past many reports have been devoted to the issue of the relationship between intracranial pressure (ICP) and outcome (Langfitt, 1976), but ICP alone does not seem to be fully reliable as an indicator of prognosis, for ICP changes are in some degree influenced by changes in arterial pressure. For example, identical ICP values with different arterial pressures do not represent similar conditions of intracranial hypertension. The aim of this study is to make an overall assessment of the relationship between ICP and outcome, taking cerebral perfusion pressure (CPP) into consideration, and to try to obtain the clinically relevant values of ICP and CPP as a guide to management.

Usefulness of ICP Histogram and ICP Histogram Array in ICP Monitoring

The importance of ICP monitoring is now well recognized. It is and will remain as one of the significant subjects for the processing of ICP values and ICP waveforms, not only in the treatment of severely brain-damaged patients but also in the understanding of pathophysiology. We present a minicomputerized system of a new method for the analysis of ICP and discuss its usefulness with clinical examples.

Automatic and Serial Monitoring of Auditory Evoked Brain-stem Responses

Auditory evoked brain-stem responses (ABRs) reflect activities of the auditory pathway in the brain-stem and by inference activities of the structures surrounding the auditory pathway. It is said that ABR is a reliable diagnostic tool for predicting the outcome of patients with primary or secondary brain-stem injuries as a result of head trauma, cerebrovascular disorders, and others. However, the evaluation of ABRs has depended mostly on the delay of the fifth wave, and such parameters as intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), were not considered. The authors have made a new automatic and serial monitoring system of ABRs, which is composed of an audio-stimulator, a stimulus-controller, an amplifier, a signal processor, and a X-Y recorder. The stimulus-controller enables to monitor ABRs automatically and serially. The clinical study consisted of 17 patients with severe brain damage, including 10 head injuries, five cerebrovascular disorders and others. Following findings were observed. 1) The fifth wave delayed synchronously with a decrease in CPP in critical brain failure. 2) In some cases, decreases in the amplitude of the waves except the fifth wave were exaggerated during trans-tentorial herniation. For better use of the new monitoring system, the ABR-ICP-MAP correlative arrays are being made up, in which ICP, MAP, and other vital signs are evaluated at a glance, which makes it easy to recognize the status of the brain failure and to decide on the appropriate therapy.

Outcome of Acute Subdural Hematoma — Large Decompressive Craniectomy Vs Hematoma Irrigation with Trephination Therapy

The clinical comparison was instituted between large decompressive craniectomy (LDC) and hematoma irrigation with trephination (HIT) therapy for 120 cases suffering from the complicated hematoma type of traumatic acute subdural hematoma. The medical management of increased intracranial pressure (ICP) included osmotherapy, hyperventilation and barbiturate induced coma post-operatively equally in these two strategies. LDC proved superior to HIT in patients with severely disturbed consciousness (30 to 200 /Japan coma scale) on admission. The parenchymal lesion associated with the complicated type of acute subdural hematoma should be regarded as the severest entity of diffuse cerebral Injury. For the present, the surgical removal of subdural clot with large external decompression and the intensive medical decompression with continuous ICP monitoring, containing barbiturate administration, if necessary are both recomended for the management of this clinical entity.